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Adsorption of cadmium(II) from aqueous solution on natural and oxidized corncob
Abstract
Adsorption isotherms were determined experimentally for Cd(II) adsorption from aqueous solution onto natural and oxidized corncob in a batch adsorber. The adsorption capacity of natural corncob was increased 10.8 and 3.8 times when the corncob was oxidized with citric acid (CA) and nitric acid (NA), respectively. The Cd(II) ions were adsorbed mainly to the carboxylic sites since the adsorption capacity increased directly proportionally to the concentration of carboxylic sites in the corncob. The effect of the solution pH in the adsorption isotherm on natural and corncob modified with CA was assessed and it was observed that the adsorption capacity of Cd(II) on corncob depends considerably on the solution pH; Cd(II) was not adsorbed at pH less than 2 and the adsorption capacity was increased five times while the solution pH increased from 3 to 6. The adsorption of Cd(II) on corncob was reversible and the Cd(II) desorbed almost completely while reducing solution pH from 6 to 2. The adsorption capacity of natural and modified corncob was increased slightly by augmenting the temperature. By performing mass balances of ions, it was corroborated that the adsorption is mainly due to ion exchange.
... The P ZC for the RBH and TBH are shown in Fig. 4. The pH pzc for the RBH and TBH are 6.3 and 2.6, respectively, showing an increment of surface acidity on acid treatment. Similar observations were observed for acid-treated corncob biomass (Khan & Wahab, 2007;Leyva-Ramos et al., 2005). The pH pzc of the RBH is slightly lower than 7.0 which indicates that the raw biomass surface of a slightly more acidic site than the basic site, resulting in net acidic (net positively charged surface) (Khan & Wahab, 2007;Ronda et al., 2013). ...
... The pH pzc of the RBH is slightly lower than 7.0 which indicates that the raw biomass surface of a slightly more acidic site than the basic site, resulting in net acidic (net positively charged surface) (Khan & Wahab, 2007;Ronda et al., 2013). The acid sites of the biomass are due to the carboxylic groups in the cellulose and hemicellulose, and the phenolic groups of the lignin (Leyva-Ramos et al., 2005). On treatments with acid, the acid sites increase and results in a higher next acid character (enhanced net positively charged surface) of the biomass (Khan & Wahab, 2007;Leyva-Ramos et al., 2005). ...
... The acid sites of the biomass are due to the carboxylic groups in the cellulose and hemicellulose, and the phenolic groups of the lignin (Leyva-Ramos et al., 2005). On treatments with acid, the acid sites increase and results in a higher next acid character (enhanced net positively charged surface) of the biomass (Khan & Wahab, 2007;Leyva-Ramos et al., 2005). Hence, one can expect that removal of sodium ions is not feasible below these pH (6.3 for BH and 2.6 for TBH) because the net positively charged surface is unlikely to attract the cations (Khan & Wahab, 2007). ...
In this work, raw bean seed husk (RBH) and sulfuric acid-treated bean seed husk were examined for adsorption of sodium ions from water. Treated bean seed husk at various time and acid concentration was refined by performance test on sodium removal by using salt solution of 1643 mg/L and solid to liquid ratio of 12.5 (g:L). Maximum removal of 27.8% was achieved at 4 M and 6-h treatment conditions. Both the RBH and the material which showed the maximum removal (TBH) were characterized by scanning electron microscope, Fourier-transform infrared spectroscope (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller, and points of zero charge (pHpzc) for physico-chemical properties study. SEM, XRD, and FTIR analyses showed changes in the morphology, crystallography, and functional group of the husk on acid treatments. BET result found for RBH (0.67 m²/g) and TBH (0.44 m²/g) showed low specific surface area. The pHpzc values obtained for RBH and TBH were 6.3 and 2.6, respectively. Optimum sodium ion removal of 20.7% (on RBH) and 17.23% (on TBH) were obtained at adsorption time (3 h), pH (10.0), initial sodium concentration (3486 mg/L), and adsorbent dosage (0.5 g). Experimental data were fitted to isothermal and kinetic models. The result showed best fit with the Langmuir isothermal model with RL value in the favorable range for all initial concentrations and correlation coefficients, R² of 0.985 for RBH and 0.963 for TBH. And the kinetics data showed best fit to pseudo-second-order with R² of 0.999 for both RBH and TBH. The overall results therefore show that bean seed husk may be used for removal of sodium ions from water.
... The pH value of the solution is a crucial parameter that controls the adsorption process due to the ionization of functional groups. The point of zero charge (pHPZC) value of the nanobiocomposite N1 KAC-CS-AgNPs was determined to be 6.15 by the method described in the work reported elsewhere [50]. To investigate the effect of pH on the adsorption capacity for Cu 2+ , Pb 2+ , and CR dye on NI KAC-CS-AgNPs, 50 mg of N1 KAC-CS-AgNPs was added to 1 L of the solution containing the known concentration (25 mg L −1 ) of the heavy metals and CR dye. ...
... The pH value of the solution is a crucial parameter that controls the adsorption process due to the ionization of functional groups. The point of zero charge (pH PZC ) value of the nanobiocomposite N1 KAC-CS-AgNPs was determined to be 6.15 by the method described in the work reported elsewhere [50]. To investigate the effect of pH on the adsorption capacity for Cu 2+ , Pb 2+ , and CR dye on NI KAC-CS-AgNPs, 50 mg of N1 KAC-CS-AgNPs was added to 1 L of the solution containing the known concentration (25 mg L −1 ) of the heavy metals and CR dye. ...
This research presents a novel and environmentally friendly approach for the synthesis of multifunctional nanobiocomposites for the efficient removal of toxic heavy metal and dye, as well as the disinfection of wastewater microorganisms. The nanobiocomposites (KAC-CS-AgNPs) were prepared by incorporating photochemically generated silver nanoparticles (AgNPs) within a chitosan (CS)-modified, high-surface-area activated carbon derived from kenaf (KAC), using a unique self-activation method. The even distribution of AgNPs was visible in the scanning electron microscopy images and a Fourier transform infra red study demonstrated major absorption peaks. The experimental results revealed that KA-CS-AgNPs exhibited exceptional adsorption efficiency for copper (Cu²⁺), lead (Pb²⁺), and Congo Red dye (CR), and showed potent antibacterial activity against Staphylococcus aureus and Escherichia coli. The maximum adsorption capacity (mg g⁻¹) of KAC-CS-AgNPs was 71.5 for Cu²⁺, 72.3 for Pb²⁺, and 75.9 for CR, and the adsorption phenomena followed on the Freundlich and Langmuir isotherm models and the second-order kinetic model (R² > 0.99). KAC-CS-AgNPs also exhibited excellent reusability of up to four consecutive cycles with minor losses in adsorption ability. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. The bacterial inactivation tests demonstrated that KAC-CS-AgNPs had a strong bactericidal effect on both E. coli and S. aureus, with MIC calculated for E. coli and S. aureus as 32 µg mL⁻¹ and 44 µg mL⁻¹, respectively. The synthesized bioinspired nanocomposite KAC-CS-AgNPs could be an innovative solution for effective and sustainable wastewater treatment and has great potential for commercial applications.
... Carboxylic functional groups can also be introduced on the biochar surface through citric acid and oxalic acid modification. 62,63 These organic acids are rich in carboxyl groups and thus could react with the hydroxyl groups on the biochar surface through esterification. 62 Biochar derived from sawdust showed a high adsorption capacity to methylene blue (178.6 mg/g) after being modified with citric acid. ...
... 62,63 These organic acids are rich in carboxyl groups and thus could react with the hydroxyl groups on the biochar surface through esterification. 62 Biochar derived from sawdust showed a high adsorption capacity to methylene blue (178.6 mg/g) after being modified with citric acid. 64 However, H 2 O 2 modification led to an overall decrease of methylene blue removal from solution. ...
Biochar has attracted increasing research attention. Various modification methods have been proposed to enhance a certain biochar function. However, these modifications may also result in an unstable structure, additional energy consumption, secondary pollution, and/or extra cost. Balanced consideration of different aspects will ensure the sustainable development of biochar technology. This review first summarizes the most commonly used methods for biochar modification. These methods are categorized according to the purposes of modification, such as surface area enlargement, persistent free radical manipulation, magnetism introduction, and redox potential enhancement. More importantly, a systematic analysis and discussion are provided regarding the balanced consideration of biochar designs, such as the balance between effectiveness and stability, functions and risks, as well as effectiveness and cost. Then, perspectives regarding biochar modification are presented. This review calls for attention that biochar modifications should not be evaluated for their functions only. A balanced design of biochars will ensure both the practicability and the effectiveness of this technology.
... Cadmium solutions (C0= 50 mg/L) with different pH values (2, 4, 5, 7 and 8) were performed with 0.04 g of each sample as shown in Fig. 4a. The maximum Cd(II) removal occurred in the pH range 5-8 while removal of cadmium was very slightly at pH 2 [14,29,30]. At pH 8, the removal of cadmium was completely occurred onto CX-700-60. ...
... At pH 8, the removal of cadmium was completely occurred onto CX-700-60. It has been reported that at pH 8.0, the species distribution is approximately 90% Cd 2+ and 10% Cd(OH) + [30]. The maximum removal was occurred at pH of 5. Carbon dose effect within different values (0.01 to 0.1 g/25 mL) with initial concentration of Cd (II) ions equal to 50mg/L was tested as shown in Fig. 4b. ...
Mesoporous carbon xerogels were prepared by carbonization of resorcinol-formaldehyde xerogel in presence of tannic acid as a soft-template at 700oC for 30, 60 and 90 min, respectively. Morphology, textural, surface functional surface groups and thermal analyses were measured. Their efficiency in liquid-adsorption of cadmium ions and PNP in a batch mode was carried out. Effect of some key factors such as pH, carbon dose, and contact time of cadmium ions and PNP as well as kinetic adsorption studies were performed. It was found that the obtained carbon xerogels of mesoporous structure have a moderate total surface area reached to 268 m2/g with various surface functional groups are effective sites for adsorbing cadmium ions and PNP from aqueous solutions. The adsorption behavior of both adsorbates on the prepared carbon samples was best described by the pseudo-second-order kinetic and Langmuir adsorption models. The maximum adsorption capacities of cadmium ions and PNP were 99 and 133 mg/g, respectively; onto the prepared carbon xerogel at 700oC and 60 min. As a result of these observations, the produced mesoporous carbon samples are very effective adsorbents for extracting considerable amounts of cadmium ions and PNP from aqueous solutions.
... The method reported by Moreno-Castilla et al. was employed to calculate the Zero-point of charge (ZPC) (see SI (a)). [30] [13,31,32]. The surface area of DC was calculated from the nitrogen adsorption values at 77 K using the ASAP 2020 instrument (Micro metrics, USA). ...
The role of oxygen-based functional groups in the photoluminescence of dehydrated carbon dots (DCs) and the adsorption mechanism of dye molecules onto the surface of DC is investigated. DC were prepared from orange peel for the first time via the chemical dehydration effect of sulfuric and phosphoric acid at 180 oC. We compared the emission spectra of DCs in different solvents in great detail. The solvatochromism of DC in different solvents is discussed. The role of oxygen-based functional groups in the light emission process is examined. Adsorption of methylene blue (MB) on the surface of DC was studied at different contact times, pH, concentrations, and temperatures. In this work, we used Langmuir and Freundlich adsorption models for the analysis. Sorption kinetic data were found to fit well with the pseudo-second-order model. Our results also showed increased MB adsorption capability with temperature. The results are essential for the application of CQDs, such as in wastewater treatment. Keywords: Photoluminescence; Adsorption; Solvatochromism; Carbon dots; Methylene blue (MB).
... This means that at pH values below 6.5, the IHCC particles have a positive net surface charge, and at pH values above 6.5 they have a negative net surface charge. A similar result was observed for raw corn cob (PZC = 6.2) by Leyva-Ramos et al. (2005). ...
The contamination of water resources with arsenic is a serious environmental problem. This research investigated the use of a strategic agricultural waste for Brazil, i.e., corn cob as a low-cost, biodegradable, and eco-efficient material for As(V) adsorption. Arsenate removal from an aqueous solution with iron hydroxide impregnated corn cob (IHCC) was investigated under different pH values (2-10). FTIR spectra revealed that monodentate complexes were formed during the adsorption of arsenate on IHCC. Furthermore, SEM micrographs revealed a uniform distribution of Fe(III) and also As(V) on the IHCC. IHCC was efficient in the removal of arsenic from acidic solutions, mainly those having pH values between 2 and 3 at temperatures below 50°C. The adsorption kinetics followed the pseudo-second order model with an activation energy of 39.35 ± 6.99 kJ mol-1 implying that chemical reaction was the controlling step of arsenic adsorption by IHCC. In addition, arsenic adsorption on IHCC was (i) an entropically driven, (ii) spontaneous, and (iii) endothermic phenomenon (+23.82 kJ mol-1) and involved electrostatic adsorption and chemosorption (Qmax = 40 mg/g, at 25°C). Therefore, a promising sustainable and environmentally friendly solution for the use of IHCC was devised in the current work.
... The biosorption process for the treatment of contaminated effluents [47,48] is a technique that involves the removal of contaminants using inert biomass [49][50][51]. Among the bioadsorbent materials that have been most studied for the uptake of toxic metals are bacteria [52], fungi [53], algae [54], yeast biomass [55], agro-industrial waste such as wheat bran [56][57][58], rice husk [59][60][61][62], and fruits and vegetables [63][64][65][66][67][68][69][70][71], among others. Avocado seeds and peel tissue wastes have demonstrated an important capacity for toxic trace metals retention [43,[72][73][74][75][76]. ...
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Heavy metal sequestration using fixed-bed columns for wastewater decontamination.
Abstract
This study evaluated the adsorbent capacity of the Ecuadorian avocado (Persea americana Hass.) seed and peel wastes as an alternative method for cadmium (Cd), mercury (Hg), lead (Pb), and nickel (Ni) ion removal from aqueous solutions. The laboratory microscale process was performed using fixed-bed columns containing 1 g of 600 μm particles of biomaterial pretreated with ethanol and ethylene glycol. Subsequently, metal solutions of different concentrations were eluted and measured by flame atomic absorption spectroscopy. Results showed that fixed-bed columns allow efficient adsorption of Pb (2.6 mg/g) with ethanol pretreatment. Lower adsorption capacity was achieved for Cd, Hg, and Ni ions. Favorable adsorption with high retention capacity was found for Pb⁺² for the ethanol pretreated bio-adsorbent at higher concentrations (120 mg/L). Lower removal percentages were found for Cd⁺², Hg⁺², and Ni⁺²; Ni showed the lowest adsorption capacities and negative RL values, suggesting inefficient adsorbent development. Regeneration of Cd, Hg, and Pb ions from avocado peel and seed showed the highest recovery when 1 mol/L HCl solution was used. Regarding the adsorption isotherms, the Langmuir model was the one that best fit our data, demonstrating that adsorption takes place in a uniform monolayer and that each contaminant ion occupies a single site.
... Biochar ages naturally in the environment over time with processes such as oxidation significantly changing the characteristics of the biochar, e.g. the prevalence of oxygenated functional groups, with associated effects on biochar sorption of contaminants (Cross and Sohi 2013;de la Rosa et al. 2018). Oxidising biochar for the sorption of metals such as cadmium has been studied previously (Leyva-Ramos et al. 2005) using similar techniques deployed by Magid et al. (2021). During the oxidation process an increase in the proportion of O and N was demonstrated alongside a decrease in the proportion of C and H mainly as a result of the increase in oxidised functional groups, specifically hydroxyl functional groups, on the surface of the biochar. ...
Plastic is a material that has become ubiquitous since entering the marketplace in the 1930s and 1940s; as a result, the presence of nano and microplastics (NMPs) are pervasive in natural environments affecting air, soil and water ecosystems. These NMPs are varied in size (categorised as either microplastics at 5 mm–1 µm or nanoplastics at < 1 µm), shape and chemical composition. They represent a potential threat to aquatic life and human health through ingestion and inhalation. The toxicity of NMPs is attributed to chemical additives introduced during production and the absorbance of inorganic and organic chemical contaminants in environmental settings. This review is designed to discuss the use of biochar as a natural adsorbent for the remediation of water contaminated with NMPs. Biochar is a sustainable, affordable material which can remediate water and contribute to ecosystem restoration. Whilst it is well established as a material to sorb organic and inorganic contaminants, its use to remove NMPs is in its infancy and as such this review sets out to outline the mechanisms and modifications of biochar to remove NMPs from aqueous environments. Although removal mechanisms in laboratory settings are becoming clearer this review highlights that remediative studies need to be undertaken in conjunction with the systematic investigation of the effect of key environmental parameters on remediation and the use of environmentally aged NMPs. The future direction of this discipline also needs to incorporate field trials alongside laboratory work to develop a stronger understanding of the viability of biochar to remove NMPs from waterways.
... Early reports concerning the use of natural and modified corncob for metal ion removal are also available in literature [28][29][30][31][32] . R.L-Ramos et al. reported the use of natural and oxidized corncob for the removal of cadmium form aqueous solution [33] . Corncob is a ligno-cellulosic agricultural byproduct. ...
Investigations were conducted to study the adsorption behavior of Zn(II) ions on a low-cost adsorbent. The natural corncob (NCC) was citric acid modified to enhance its adsorption ability. The physical and chemical properties of the modified corncob (MCC) such as surface area, surface functional groups and surface charge determine the adsorption characteristics of the material. The surface areas of NCC and MCC were determined to be 13 m 2 /g and 9 m 2 /g, respectively. The values for the pH PZC of the NC and MCC were found to be 5.8 and 3.6, respectively. The effect of various parameters such as pH of the medium, adsorbent dose, initial Zn(II) concentration and temperature were examined. The equilibrium adsorption data were modeled by Langmuir, Freundlich , Temkin and Dubinin-Radushkevich isotherm equations. The constants of each isotherm model were evaluated. The presented values of the normalized standard deviation (∆q) indicate that the Freundlich isotherm provide the best correlation between experimental and predicted data with the lowest value of ∆q equal to 3.4 % and appears to be the best fit model for the present Zn(II) adsorption studies. The obtained value for the mean energy of adsorption (E ads = 10.8 kJ mol-1) , shows that the interaction between Zn(II) ions and MCC proceeded principally by ion exchange at all temperatures. The optimum conditions for the maximum Zn(II) adsorption capacity (q m = 26.3 mg g-1) by MCC were pH 5.0±0.1, adsorbent dose 1.0 g, temperature 318 K, and initial Zn(II) concentration 250 mg L-1. The sorption process was found to be endothermic in nature (∆H : 70.7 kJ mol-1), with increase in entropy (∆S : 292.2 J mol-1 K-1). The negative value of Gibbs free energy, ∆G indicates that the adsorption occurs via a spontaneous process. The increase in-∆G from 16.7 to 21.9 kJ mol-1 with increase of temperature from 298 K to 318 K indicates that the adsorption of Zn(II) onto MCC is more favorable at higher temperatures. The results show that MCC , which has a very low economical value, may be used effectively in removal of Zn(II) from aqueous solution.
... Numerous works in literature have reported the use of adsorbents from various agricultural or forest-based biowastes to remove pollutants from wastewater (Jamwal et al. 2019;Chauhan et al. 2023a, b;Ahmad et al. 2018;Takmil et al. 2020). However, one serious downside associated with the agricultural or forest-based biowaste in their pristine forms for use as adsorbents is poor adsorption efficacy (Leyva-Ramos et al. 2005;Piffer et al. 2020;Ho et al. 2005) which can be improved significantly after suitable modification, such as milling (Zhang et al. 2013). Many protocols including activation to activated charcoal are not cost-effective though adsorption performance may increase manifolds. ...
Herein, we report the synthesis of an oxidized pine needle-thiosemicarbazone Schiff base (OPN-TSC) from whole pine needles (WPN) as a dual-purpose adsorbent to remove a cationic dye, methylene blue (MB), and Hg²⁺ ions in separate processes. The adsorbent was synthesized by periodate oxidation of WPN followed by a reaction with thiosemicarbazide. The syntheses of OPN and OPN-TSC were confirmed by FTIR, XRD, FESEM, EDS, BET, and surface charge analysis. The emergence of new peaks at 1729 cm⁻¹ (–CHO stretching) and 1639 cm⁻¹ (–COO⁻ stretching) in the FTIR spectrum of OPN confirmed the oxidation of WPN to OPN. FTIR spectrum of OPN-TSC has a peak at 1604 cm⁻¹ (C = N stretching), confirming the functionalization of OPN to OPN-TSC. XRD studies revealed an increase in the crystallinity of OPN and a decrease in the crystallinity of OPN-TSC because of the attachment of thiosemicarbazide to OPN. The values of %removal for MB and Hg²⁺ ions by OPN-TSC were found to be 87.36% and 98.2% with maximum adsorption capacity of 279.3 mg/g and 196 mg/g for MB and Hg²⁺ ions, respectively. The adsorption of MB followed pseudo-second-order kinetics with correlation coefficient (R² of 0.99383) and Freundlich isotherm (R² = 0.97239), whereas Hg²⁺ ion removal demonstrated the Elovich (R² = 0.97076) and Langmuir isotherm (R² = 0.95110). OPN-TSC is regenerable with significant recyclability up to 10 cycles for both the adsorbates. The studies established OPN-TSC as a low-cost, sustainable, biodegradable, environmentally benign, and promising adsorbent for the removal of hazardous cationic dyes and toxic metal ions from wastewater and industrial effluents, especially the textile effluents.
Graphical abstract
... Various corn cob-based adsorbents such as the unmodified [29], biochar-based [30] and activated carbon-based [31] have been utilised for the removal of CIP from aqueous media. The use of nitric acid-modified corn cob has been reported to enhance its adsorption performance over the unmodified cob for pollutants such as cadmium ions, a potentially toxic element [32]. Nitric acid modification can increase surface area, add functional groups (such as carboxylic, hydroxyl, and carboxyl groups) on the corn cob's surface, and improve chemical stability by removing impurities, which accounts for this improvement. ...
The removal of emergent contaminants like ciprofloxacin (CIP) from effluents discharged from pharmaceutical industries is important for water purification. An environmental and eco-friendly nitric acid modified adsorbent produced from corn cob containing cellulosic materials was used for the sequestra-tion of ciprofloxacin antibiotic from aqueous media. The adsor-bent was characterised using SEM, FTIR, BET, EDX, and TGA techniques. The results of the characterisations depicted enrichment of the adsorbent porosity, surface functional groups and surface area (156.39 m 2 /g) of the agro-waste precursor after pretreatment. The effects of various adsorption parameters, including adsorbent dosage, initial concentration, pH, contact time, and temperature, were investigated, with an optimal pH value of 7 being determined. The maximum monolayer adsorp-tion capacity for the CIP drug was found to be 51.55 mg/g. The Freundlich isotherm successfully explained the generated experimental results indicating a heterogeneous surface for the physisorption process. The rate-determining step of the reaction was predominately dominated by intraparticle diffusion , and the kinetic models were represented by pseudo-second-order processes that suggested chemisorption. The analysis of thermodynamics revealed that the adsorption process was endothermic (∆H o < 0), and spontaneous (∆G o < 0) with an increasing degree of randomness (∆S o < 0). Finally, it should be noted that CIP loaded on the adsorbent could be easily des-orbed with 0.1 mol L −1 HNO 3 and the adsorbent showed good reusability for adsorption of the studied drug. Therefore, this study proposed the viability of acid-pretreated corn cob for economically effective treatment of ciprofloxacin in water or similar pharmaceutical-laden wastewater.
... The Boehm's titration method was described briefly in Sect. 1 of the online resource 1. To determine the pH PZC for CABC and MPBC, surface titration method was used (Leyva-Ramos et al., 2005). The specific surface area of pristine and modified biochars was measured by following the methylene blue adsorption method, which is described in Sect. 2 of the online resource 1 (Tewari & Thornton, 2010). ...
The Mimosa pigra, a noxious invasive plant, was used to produce biochar (MPBC), which was then modified with citric acid to synthesize engineered biochar (CABC) with improved adsorption properties. The effects of solution pH (3.0–9.0), Cr(VI) initial concentration (2–25 mg L⁻¹), contact time (up to 24 h), and temperature (25, 35, and 45 °C) on the efficacy of Cr(VI) removal by biochars were examined through batch sorption experiments. Furthermore, the mechanisms of the sorption process were revealed by spectroscopic analysis performed with X-ray photoelectron spectroscopy (XPS). Results demonstrated that both biochars have strong adsorption potential toward Cr(VI) in an acidic medium (pH 3.0) whereas CABC showed reasonably high adsorption selectivity for Cr(VI) (78%). The incorporation of O–C = O and -OH functional groups onto the adsorbent surface through the esterification reaction was found to increase the Cr(VI) sorption capacity of modified biochar by 15%. Experimental kinetics and isotherm data were well described by fractional power kinetic and Hill isotherm models with a maximum adsorption capacity of 14.5 mg g⁻¹. Thermodynamic studies prove the endothermic and spontaneous nature of the adsorption process. The post-adsorption spectroscopic analysis performed with XPS confirmed the coexistence of Cr(VI) and Cr(III) on the CABC surface. A three-step reaction mechanism involving electrostatic attraction, reduction, and complexation was responsible for Cr(VI) adsorption onto CABC. This work presents a win–win strategy that will limit the expansion of noxious plants by converting them into biochar and simultaneously removing the top priority pollutant (Cr) from water.
Graphical Abstract
... Rice husk ash (RHA) was found to be an effective adsorbent for the removal of Nickel(II) ions from aqueous solution. The study deals with the competitive adsorption of nickel and Nickel(II) ions from aqueous solution onto RHA [51][52][53][54][55][56][57][58][59]. Non-competitive Redlich-Peterson (R-P) and Freundlich models represent the single metal ion equilibrium sorption data. ...
Adsorption process has proven to be one of the best water treatment technologies around the world and activated carbon is undoubtedly considered as a universal adsorbent for the removal of different types of pollutants from water. However, widespread use of commercial activated carbon is sometimes restricted due to its high cost. Attempts have been made to develop inexpensive adsorbents utilizing numerous agro-industrial and municipal waste materials. Use of agricultural waste materials as low-cost adsorbents is attractive because it reduces the cost of waste disposal, thereby leading to environmental protection. In this review, agricultural, synthetic and other adsorbents used for adsorbing Nickel(II) ion from aqueous solutions are reported. Different ways to improve their efficiencies are also discussed.
... In addition, the loss and reduction of impurity composition cannot be immediately removed by washing using water [23]. The EDX results also show that the O atom increases its composition after modification of nitric acid due to the oxidation of nitric acid in corn stalks [25]. ...
Corn stalk modification was used as an adsorbent to remove metal ions of Cu 2+ in solutions and have done in the adsorption column with continuous operation. The corn talk was modified with nitrate acid (HNO3). The Adsorption operations were applied with corn stalk variation sizes 50 mesh, and 70 mesh with initial concentrations of metal ions 50 and 150 mg/l. The solution flow was controlled at 5 and 15 ml/min. The adsorption operations have been done in up-flow and down-flow. Each operation collected the flow effluent base on pore volume intervals of 4 to 32 PV. To confirm the changes in surface structure and chemical components after modifying have used SEM and EDX. The results show changes significantly. While, the application of corn stalk was modified shown by the influence of loading time, % removal efficiency, adsorption kinetics, and breakthrough curve. Increased loading time occurs at increased concentration, decreased flow rate, and increased adsorbent size. While the increase in% removal efficiency occurs in the decrease in concentration, decreased flow rate, and increased adsorbent size. On adsorption up, the flow has longer saturation than in downstream adsorption. The shape of the breakthrough curve for adsorption up the flow and down flow follows the shape of the "S" curve. But the up flow breakthrough curve on adsorption is more stable than adsorption with the down flow.
... Not only do they have a large capacity for the removal of ions but they are very low cost. Adsorption of ions by biosorbents has been investigated using a wide range of agriculture wastes, for instance, lemon peel (Bhatnagar et al., 2010), corncob (Leyva-Ramos et al., 2005;Vafakhah et al., 2014), corn stalk (Vafakhah et al., 2014), almond integument (Hosseini et al., 2013), hydroxyapatite (Corami et al., 2008;Plec et al., 2006), chitosan (Baroni et al., 2008;Bazargan-lari et al., 2014;Taylor et al., n.d.), peanut hull (Contribution, 1995), bagasse fly ash (Gupta et al., 2003), rice husk (Ajmal et al., 2003) and sawdust (Yu et al., 2000) along with the optimization of different conditions on the adsorption process of biosorbent. ...
In this study, fish scales (Pomadasys kaakan's scales) were used as new biosorbent for removing Ni2+ and Cu2+ ions from wastewater. The effects of electric and magnetic fields on the absorption efficiency were also investigated. The effects of sorbent content, ion concentration, contact time, pH, electric field (EF), and magnetic field (MF) on absorption efficiency were assertained. In addition, the isotherm of absorption was studied in this work. This study revealed that electric field and magnetic field have significant effects on the absorption efficiency of ions from wastewater. An increase in the electric field enhanced the removal percentage of the ions and accelerated the absorption process by up to 40% in comparison with the same condition without an electric field or a magnetic field. By increasing contact time from 10 to 120 min, the removal of Ni2+ ions was increased from 1% to 40% and for Cu2+ ions, the removal increased from 20% to almost 95%, respectively. In addition, increasing pH, ion concentration and scales dose increased removal percentage effectively. The results indicated that using fish scales for Cu2+ ions absorption is ideal due to the very high removal percentage (approximately 95%) without using either an electric or magnetic field.
... Acid treatment alters functional groups and several surface area/porosity characteristics to enhance adsorption performance ( Table 2). The adsorption capacity of natural corncob for Cd 2+ increased from 4.7 to 19.3 mg g − 1 when the material was acidified by HNO 3 (Leyvaramos et al. 2005). The Cd 2+ was adsorbed mainly by the carboxylic sites through ion exchange and the adsorption capacity increased directly proportional to the concentration of carboxylic sites. ...
Water pollution is a great risk to aquatic ecosystems and human health. Among water pollution remediation strategies, adsorption mechanisms provide strong efficacy for a wide variety of pollutants. Several recent efforts examined the development of low cost adsorbents utilizing commonly available agricultural wastes. However, raw (i.e., unaltered) agricultural wastes typically exhibit low sorption capacity for pollutants due to their non-reactive structural/composition properties. Hence, modifications of raw agricultural wastes to enhance their sorption capacities for various aquatic pollutants are necessary to optimize their performance for pollutant removal. Numerous modification techniques are effective in altering agricultural wastes for improved sorption performance. This paper reviews the development of modified agricultural waste materials for pollutant removal from water. We compiled an extensive inventory of modification techniques applied to agricultural wastes to enhance their adsorption capacities for removal of a wide range of pollutants. Modification strategies and their effects on sorption properties were rigorously examined to highlight key advancements in the preparation of adsorbents from agricultural wastes. Finally, the costs of these materials were examined, along with the benefits and drawbacks concerning their use. This review provides a thorough assessment for advancing the utilization of agricultural wastes for preparing adsorbents for water treatment.
Graphical Abstract
... Citric acid and oxalic acid modification can also introduce carboxylic functional groups to the biochar surface. [90,91] HNO 3 oxidation generally initiates amination of the biochar surface, introducing both oxygen and nitrate functional groups.. [92] NH 2 groups can also be created by heating FeCl 3 loaded agar in an NH 3 environment in a single process. The agar's OH group could react with NH 3 to form amino groups. ...
Arsenic (As) contamination in water sources is a serious threat to safe drinking water afflicting many developed and developing nations. Among the different water treatment techniques, arsenic removal using metal‐loaded biochar has gained considerable interest as an efficient environmentally sustainable adsorbent. This review critically focuses on an in‐depth analysis of different adsorption mechanisms and various physicochemical properties such as pH, surface area and surface charge, porosity, and functional groups of the metal‐loaded biochar that are significant for As adsorption, which has not been previously described. It centers on addressing the overall effectiveness, governing mechanisms, and influential factors of metal‐loaded biochars for As removal from the aqueous medium. Special consideration on oxidation of arsenite to arsente and its removal was given. The oxidation processes are also effective in reducing arsenic toxicity by oxidation of arsenite to arsenate. A comprehensive insight into the utility of biochar for As removal for future field applications of biochar is delineated.
... This indicates that the adsorbent is selective for the anionic dyes at only acidic pH. The pHpzc of corncob was 6.83 and 6.2, therefore, the corncob particles have positive charges in pH below these values [38,39]. The positive charge of the corncob surface at acidic pH is owing to the protonated binding sites. ...
Toxic dyes are irrefutable effluent components of textile wastewater, so they have become a major economic and health concern. With the purpose of efficient removal of textile dyes, multiple nature-inspired adsorbents have been applied. Herein, raw corncob is proposed as a novel highly efficient, low-price, and abundantly attainable adsorbent with the potential for uptake of methyl red and methyl orange. Multiple experiments were carried out to optimize parameters including pH, primary concentration, adsorbent dosage, temperature, and contact time. The adsorption was raised with the mounting of the contact time and it was alleviated with the addition of initial concentration. The foremost uptake of dye was apperceived at an acidic medium pH 4 for methyl red and pH 1 for methyl orange. Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy were employed to characterize the surfaces of corncobs. The well-fitted Langmuir and Freundlich models (methyl red: R² = 0.9956 and methyl orange: R² = 0.9883) confirmed the homogeneous monolayer adsorption process on the raw corncob surface. The obtained results disclose that corncob is an effectual biosorbent for eliminating anionic dyes without the necessity for any prior modifications.
... So far, there is dearth of information on the modification of cocoa pod using citric acid as the modifying agent. However, it has been used for other agricultural wastes like corn cob [19], soybean hulls [20], Moringaoleifera [15] leaves and so on with enhanced adsorption. In this study, the use of citric acid to attach free carboxyl groups onto the hydroxyl of the polysaccharide matrix of the cellulosic agricultural materials is investigated. ...
... Upon a successfully incorporation of magnetite onto FMO, the pH zero point (pH zpc ) increased from 4.0 to 5.0. The obtained point of zero charge (pH zpc ) was higher than that of modified activated carbon (Huang et al., 2009), coffee husk (Oliveira et al., 2008), oxidized corn hob (Leyva-Ramos et al., 2005) and thuja orientalis (Malkoc, 2006). ...
Chromium(VI) a heavy metal by nature, is one of the most toxic metals in the environment. We recently reported functionalized Moringa Oleifera (FMO) leaves as a low cost and efficient adsorbent for the removal of Cr(VI) and bacterial from water, as a continuation, we report the incorporation of magnetic nanoparticles (Fe3O4) with previously studied FMO for Cr(VI) removal from aqueous solution. Iron oxide due to its magnetic properties has been shown to assist in the recovery of its adsorbents. In this study, in-situ co-precipitation synthesis of iron nanoparticles onto FMO was employed. During chemical precipitation, the iron precipitate tends to cover the FMO thus forming some outer-shell coating of magnetite on the surface of FMO. The Fe3O4/FMO was characterized using XRD, FTIR, SEM, BET, TGA and Zeta potential. FTIR results showed a new developed intense peak at 685.6 cm−1 for Fe-O stretching, indicating successful incorporation of Fe3O4 nanoparticles onto FMO. Powder XRD was further use to confirm the formation and further indicated that the structure of FMO was still intact even after the Fe3O4 incorporation. The adsorption conditions such as pH, dosage, time and concentration were optimized to 2, 0.15 g, 25 min and 20 mg/L, respectively. The adsorbent was selective toward Cr(VI) since 99% was removed in the presence of interfering ions (20–100 mg/L). The adsorbent (Fe3O4/FMO) could also be reused up to 4 times with a percentage Cr(VI) removal of >80% in the 4th cycle. Adsorption kinetics studies obeyed pseudo second-order model, suggesting a chemical interaction mechanism (chemisorption) between Fe3O4/FMO and Cr(VI). Therefore, the adsorbent has shown that it can be used for selective removal of Cr(VI) from wastewater and potentially other heavy metals as well.
... En la Figura 3-A se nota que hay efecto positivo del pH en la biosorción, lo cual, indica que a mayor pH la capacidad de biosorción del endocarpio también aumenta en el caso de Cd (II), lo cual, no se cumple para Pb (II). Asimismo, otro estudio indica que, el pH de la solución juega un papel importante en la biosorción de Cd (II) con maíz, notando que el Cd (II) no se adsorbe a pH por debajo de 2 y que la capacidad de biosorción incrementa drásticamente a pH entre 3-6 porque los sitios carboxílicos se disocian a pH entre 3-6 determinando que la máxima biosorción de Cd (II) se alcanzó a pH entre 6-8 [20]. Otro factor importante para la remoción de Cd (II) que presenta tendencia positiva en la capacidad de biosorción es la concentración inicial, encontrando que cuando se incrementa la concentración de Cd (II) en la solución bimetálica la biosorción se incrementa, lo cual, no ocurre con el Pb (II), pudiendo existir una competencia por los sitios de biosorción del endocarpio de Olea europea, o que los sitios de adsorción para Pb (II) se saturaron, Sin embargo, otro estudio indica que, la capacidad de biosorción del endocarpio de aceituna aumenta ligeramente al elevarse la concentración de Pb (II) [14], sin embargo, el estudio reportado fue en soluciones donde sólo presentó como único contaminante al Pb (II) y en la presente investigación se encontró que en una solución bimetálica el comportamiento es la adsorción es diferente. ...
En la presente investigación se optimizó la biosorción de Cd (II) y Pb (II) en endocarpio de Olea europea, para ello se evaluaron factores como tamaño de partícula, pH, pretratamiento ácido o básico y concentración inicial de ambos metales. Se utilizó un sistema de agitación tipo Batch donde se determinó que el tiempo al cual la remoción de ambos metales alcanza el equilibro fue de 40 minutos. El diseño factorial dio como resultado que el tamaño de partícula adecuado para el proceso de biosorción es de 75-150 μm y un pretratamiento básico con NaOH, siendo este último el factor de mayor importancia en la remoción de ambos metales. La optimización por el Método de Superficie Respuesta (MSR) dio como resultado que el pH=6,1 y concentración inicial de 88.3 mg/L son las condiciones óptimas para lograr remociones máximas de 28.1 y 58.5 mg/L para Cd (II) y Pb (II) respectivamente. También se encontró que Olea europea remueve en mayor proporción cada metal en soluciones monométalicas que en soluciones bimetálicas.
... So far, there is dearth of information on the modification of cocoa pod using citric acid as the modifying agent. However, it has been used for other agricultural wastes like corn cob [19], soybean hulls [20], Moringa oleifera [15] leaves and so on with enhanced adsorption. In this study, the use of citric acid to attach free carboxyl groups onto the hydroxyl of the polysaccharide matrix of the cellulosic agricultural materials is investigated. ...
Chemical modification of biosorbent is a common practice in wastewater treatment when using adsorption technology.
Thioglycollic acid has been used for the modification of cocoa pod without any significant improvement in its adsorption
capacity for lead, cadmium and copper. This study is aimed at improving the sorption of these metal ions from aqueous
solution using citric acid as the modifying agent for cocoa pod shell. The dried cocoa pod shell was ground and reacted
with citric acid according to the method in the literature. Batch adsorption studies were conducted to examine the
influence of pH, temperature, initial metal ion concentration; sorbent dose and contact time on the biosorption of Pb2+,
Cu2+and Cd2+ions by modified and unmodified cocoa pod shell. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich
models were used for fitting the equilibrium data. The amount of metal ion sorbed was determined using flame atomic
absorption spectrophotometer (FAAS). The result for the adsorption of the metal ions under varying pH showed that
sorption was pH dependent. The trend in biosorption was in the order of Cd2+> Cu2+> Pb2+ on unmodified cocoa pod shell
(UCPS); while the trend in biosorption of the ions onto modified cocoa pod shell (MCPS) was in the order of
Pb2+ > Cu2+> Cd2+. The amount of Pb2+ adsorbed increased from 4.62-33.56 mg/g after modification as shown by values
obtained using the Langmuir equation to fit the biosorption data. Langmuir isotherm gave R2 values which shows that it
satisfactorily describe the biosorption process for Pb2+, Cu2+and Cd2+ ions on UCPS and MCPS. The kinetics of the
sorption process was best described by the pseudo-second order kinetic model (R2>0.9922). Thermodynamic parameters
showed that biosorption process was feasible and spontaneous for Pb2+, Cu2+and Cd2+ions onto UCPS and MCPS. The
process is exothermic for Cu2+ and Cd2+ ions; but endothermic for Pb2+. This study has shown that citric acid modified
cocoa pod shell is a good biosorbent especially for Pb2+ ions
... The pH of the filtrate was measured using a calibrated pH meter and the measured value is the point of zero charge. Leyva-Ramos et al. and El-Shafey et al. have used this method successfully [51][52][53]. ...
Environmental friendly and biocompatible fluorescent carbon nanoparticles (CNPs) show great potential for various applications. The functional groups on the surface of the NPs dramatically influence the absorption and emission characteristics of the particles. However, a conclusive emission mechanism of CNPs and the exact role of functional groups are still lacking. Herein, a systematic investigation has been carried out by quantifying the oxygen-based function groups (-OH, -CHO, -COOH, -CO, -COO) present on the surface of activated carbon (AC) nanoparticles to identify their role in the emission characteristics. AC samples, prepared by the activation process of green waste of mandarin peels, were subjected to further treatments to achieve different levels of surface functionality with oxygen containing functional groups such as carbonyl, carboxyl, phenol and lactone. Various characterization techniques were employed to identify and quantify the functional groups. A detailed emission study revealed the role of specific functional groups in the emission process. Our results suggests that various emissive pathways in CNPs can be controlled by selective surface functionalization. This study shows significant results, which could shed more light on the emission mechanism of CNPs and the pivotal role of surface functional groups.
Heavy metals are toxic recalcitrant compounds, present in many industrial effluents like tannery industry, electroplating industry and more. Industrial sector develops whole world and contributes to welfare of the country and supports every country gross domestic product (GDP). To protect our environment from toxic compounds and carcinogenic heavy metals without compromising on environmental health, new eco-friendly adsorbents must be implicated in treatment of industrial discharges. The agriculture wastes from both domestic and large-scale sectors majorly dumped in landfills, which further pollutes the environment, so these agriculture waste can be further utilized for its metal sequestration property and can be used for heavy metals bio-remediation. This study shows that agriculture waste such as saw dust, brans, cobs, pulps, fruits flowers, adsorbed up to 98 % of the heavy metals. This study supports sustainable development goals and recommends using agriculture wastes, an eco-friendly green technology, for safeguarding our environment from further secondary pollution.
CRH والمنشطة) (ARH المائية المحاليل من) حسن عالوي بيداء عمران عادل رشاد ياسين مالك محمد البصرة الزراعه/جامعه كليه البصرة الزراعه/جامعه كليه البصرة الزراعه/جامعه كليه rashadomran74@yahoo.com الملخص ا النشطة الرز بقشور المسماة الرز قشور رماد اختبر اذ , البصرة جامعه الزراعة كلية مختبرات في التجربة جريت Activated Rice Husk (ARH تعديل اجراء خالل من طورت )والتي المكربنة الرز قشور على كيميائي Carbonized Rice Husk (CRH و الزنك و الكادميوم و النحاس (الثقيلة العناصر بعض امتزاز على) فراندليج الحراري للتماثل االمتزاز معادلتي الى االمتزاز عملية اخضعت. المائية محاليلها من) والرصاص النيكل Frenudlich دي و وبينن-رادوشيكيفش Dubinin-Radushkevich (D-R) جيد وصف المعادلتين كلتا واعطت (الرز قشور اسطح على المدروسة العناصر لتفاعل CRH و() ARH ABSTRACT The rice husk ash called activated rice husk (ARH) which developed by chemical modification of carbonized rice husk (CRH) have been tested at adsorption of some heavy metals(Copper , Cadmium , Zink , Nickel and Lead) from its aqueous solution. the adsorption data have been submitted to two equilibrium iso therm models , Frenudlich and Dubinin-Radushkevich (D-R) .Adsorption data fitted well with two models by (R 2) significant. Heavy metals were different in their favority to adsorption surfaces. As the Cu +2 and Ni +2 ions surpassed in adsorption at activated rice husk (ARH) Surfaces , While the pb +2 and Zn +2 ions was favorated the carbonated rice husk (CRH) Surfaces. while the Cd+2 ions was equal in their favority to two types of adsorption substances. Heavy metals were to take the following order in increases of adsorption quantity in (CRH) : Cd +2 > Zn +2 > pb +2 > Cu +2 > Ni +2 , while in (ARH) : Cd +2 > Zn +2 > Cu +2 > pb +2 > Ni +2 .
Co-digestion of biodegradable wastes is a viable option to utilize multiple biogenic wastes and overcome energy shortages. However, bioenergy and biofertilizers produced during the co-digestion of different wastes can be reliable options for achieving circular bio-economy systems and Sustainable Development Goal 7 (Affordable and Clean Energy). Thus, a batch study of poultry droppings (PD) and maize cob (MC) was conducted at seven
different (100:0, 90:10, 70:30, 50:50, 30:70, 10:90, and 0:100) mixing ratios to select the optimum ratio for co-digestion. This laboratory scale study was conducted in a control condition (35
◦C temperature) to investigate the biogas production potential of each test group. The 30:70 ratio of PD and MC showed the highest biogas (315.4 ±15.8 mL/gVS) and methane (162.67 ±7.37 mL/gVS) yield. Biogas production was 4.8 and 1.16 times higher
compared to mono-digestion of PD and MC, respectively. Hydrogen sulphide content of biogas at 30:70 ratio was reduced by 99.50 % and 92.58 % compared to mono-digestion of PD and MC, respectively. Potassium and phosphorus content of digestate at 30:70 ratio was increased by 97.91 % and 75.17 % compared to feedstock. Kinetic simulation of experimental methane yield showed that the Logistic model was well-fitted and reliable for
determining the kinetic process parameters, and forecasting methane yield. Further study on suitable pre-treatment and the addition of additives during co-digestion might increase yields.
The work reports the removal of cadmium from water by applying an efficient low-cost lignocellulosic adsorbent, rooibos tea waste. The cadmium-loaded rooibos tea waste was used for the photocatalytic abatement of sulfamethoxazole to cater to the setback of secondary pollution mostly associated with the adsorption technique. The rooibos tea waste adsorbent displayed a high removal efficiency of about 90.63% for 10 mg/L Cd(II) ions at 45 °C, 180 min agitation time, pH 7, and a dosage of 500 mg. The process of Cd(II) adsorption was endothermic and spontaneous. Also, the spent adsorbent was found to be efficient toward the photocatalytic breakdown of 10 mg/L sulfamethoxazole with a degradation efficiency of 69% after 150 min. In addition, the extent of mineralization of the sulfamethoxazole by the spent adsorbent as obtained from the total organic carbon data was found to be 53%. Therefore, based on the results obtained from this work, rooibos tea waste lends itself as a cheap, eco-friendly, easily sourced, and viable adsorbent for the removal of toxic ions like Cd(II). Also, the successful reuse of the spent adsorbent is a promising approach to cater to the major setback of secondary pollution associated with adsorption technology.
Heavy metal elimination from polluted water is a prerequisite as they are hazardous to the environment as well as the health of people. Heavy metal removal from wastewater may be done effectively and economically via biosorption. Using waste materials as biosorbents from the food industry is an eco-friendly approach to waste management and pollution control. A considerable amount of waste is being generated from the food industry, such as grape pomace, coffee grounds, citrus peels, banana peels, coconut coir, tea waste, and rice husks, which are dominant in functional groups comparatively like carboxylic, hydroxyl, and amino groups that are proficient of binding heavy metals. A number of variables, consisting of temperature, pH, time of contact, and initial metal concentration, have an impact on the biosorption process. The routine technique for utilization of waste materials with respect to the food industry as biosorbents has several advantages, such as their abundance, budget-friendly, and ability to get rid of heavy metals effectively. In conclusion, waste materials from the food industry have the weightage to be utilized as effective biosorbents for heavy metals, providing a sustainable and eco-friendly solution for managing waste and pollution.
Toxic pollutants in the form of heavy metals are added through various anthropogenic activities daily into the aquatic ecosystem beyond their permissible limits, and their bioaccumulation capacity makes them hazardous substances for the survival of all organisms. Thus, their removal from aquatic ecosystems is the need of the hour. Treatment of wastewater containing heavy metals through biosorption is gaining popularity and is being explored all around the world due to its various advantages over conventional methods of treatment. Utilization of animal waste as a biomaterial could be the best solution to remove it from the ecosystem. Such treatment methods are a blessing for developing and underdeveloped countries due to their low cost. This paper provides in-depth details about heavy metals, their health implications, mechanisms of toxicity, modes of transportation, and conventional treatment approaches. A comprehensive understanding of the biosorption process, encompassing its world scenario, evolution, mechanisms, factors affecting the process, and advantages, will also be covered. Finally, animal wastes and their applicability in the removal of heavy metal pollutants from wastewater shall also be thoroughly reviewed, followed by their future utility and recommendations.
Tartaric Acid-modified Rice Husk biochar (TARH) was evaluated as an efficient and cost-effective adsorbent to eliminate Fluoride (F¯) ions from aqueous solutions. F¯ is a major contaminant in groundwater, and current conventional treatment methods have certain drawbacks in treating higher concentrations of fluoride. The adsorption efficiency of TARH was improved by pre-treating rice husk biochar using tartaric acid (organic acid), which was confirmed by FT-IR measurement, indicating the presence of carboxylic acids, hydroxyl groups, and amine surface functional groups. The study optimized fluoride batch adsorption experiments by considering the parameters affecting adsorption, including pH, contact time, initial concentration, and adsorbent dosage using the Central Composite Design (CCD) from Response Surface Methodology (RSM). Maximum fluoride adsorption of 74.73% was attained by TARH under ideal circumstances (an initial fluoride concentration of 32 mg/L, a pH of 7, 0.25 g/100 mL of adsorbent dosage, and 180 minutes contact duration). The CCD models showed an exceptional R2 value of 0.988 for fluoride adsorption, illustrating their efficacy. Three-dimensional response surface plots were visualized to analyse the effects of control parameters on %adsorption, and statistical analysis supported the validity of the CCD model. Isotherm models and adsorption kinetics were investigated. The adsorption exhibited monolayer adsorption according to the Langmuir isotherm model and a pseudo-second-order rate-limiting phase due to chemisorption. The column adsorption studies were performed for various experimental factors such as influent fluoride concentration (4–16 ppm), influent flow rate (4–8 mL/min), and fixed-bed depth (4–8 cm). The experimental data were examined using the Yoon-Nelson, Thomas, and BDST models, which revealed a substantial correlation between the experimental findings and model predictions. The effectiveness of TARH was examined by regeneration study and case study was performed to evaluate the fluoride removal from actual water samples.
This overview addresses the formation of solid trash and the various forms of waste from a variety of industries, which environmentalists have embraced. The paper investigates the negative effects on the environment caused by unsustainable management of municipal solid trash as well as the opportunities presented by the formal system. This examination looks at the origins of solid waste as well as the typical treatment methods. Pyrolysis methods, feedstock pyrolysis, and lignocellulosic biomass pyrolysis were highlighted. Explain in detail the various thermochemical processes that take place during the pyrolysis of biomass. Due to its carbon content, low cost, accessibility, ubiquitousness, renewable nature, and environmental friendliness, biomass waste is a unique biochar precursor. This study looks at the different types of biomass waste that are available for treating wastewater. This study discussed a wide variety of reactors. Adsorption is the standard method that is used the most frequently to remove hazardous organic, dye, and inorganic pollutants from wastewater. These pollutants cause damage to the environment and water supplies, thus it is important to remove them. Adsorption is both simple and inexpensive to utilize. Temperature-dependent conversions explain the kinetic theories of biomaterial biochemical degradation. This article presents a review that explains how pyrolytic breakdown char materials can be used to reduce pollution and improve environmental management.
The presence of residual organic dyes in water resources results in a threat for both environment and human health due to their adverse health effects such as mutagenicity, carcinogenicity, and teratogenicity. Thus, they must be removed from industrial wastewater. Among these dyes, methylene blue (MB) is a toxic, carcinogenic, and almost non-biodegradable dye and can pose a significant threat to human health and environmental safety. Thus, it is removed from industrial effluents by a variety of methods, including adsorption, prior to discharge into the environment. This study aims to optimize the adsorption conditions of MB from an aqueous solution with nanocomposite of silver onto single-wall carbon nanotube metronidazole (Met-SWCNTs/Ag). Response Surface Methodology (RSM) based on Central Composite Design (CCD) is used to optimize and model the adsorption of MB dye (as pollutant) on Met-SWCNTs/Ag. The Met-SWCNTs/Ag is synthesized using Met-SWCNT impregnated with silver nitrate. The produced Met-SWCNT/Ag nanocomposite is characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The effect of four independent variables including nanoparticle (NP)/dye ratio, temperature, pH and contact time on MB removal on the specific surface area of SWCNT/Ag and Met-SWCNTs/Ag is evaluated. The accuracy and fit of the model for MB removal using Met-SWCNTs/Ag are estimated by ANOVA with R ² > 0.99 and P -value < 0.0001. RSM results indicates that the NP/Dye ratio has the most significant influence on the adsorption of MB onto Met-SWCNTs/Ag. The optimal condition of the adsorption process takes place at NP/Dye ratio of 2.21, contact time of 65.57 min, and pH = 6.15 at 25.79 °C temperature leading into a 98.94 % MB removal. Isotherms and kinetic studies are performed to characterize the adsorption behavior of the adsorbent for MB removal. The adsorption behavior of the MB onto Met-SWCNTs/Ag is best described by the Langmuir isotherm model with regression coefficient R ² of 0.9935 with the Q max of 112.42 mg/g. Adsorption kinetics of Met-SWCNT/Ag is investigated and modelled by means of the pseudo-first-order, pseudo-second-order models which is best fitted to the pseudo-second-order model. The thermodynamic study reveals that the adsorption of MB dye is spontaneous and exothermic. Experimental results suggest that the modified SWCNTs/Ag with Met achieves a higher removal efficiency of (∼98 %) when compared to SWCNTs/Ag (∼93 %).
The toxic and recalcitrant nature of metals in an aqueous solution may cause an ill impact on plants, humans, and other living beings. Though many methods like membrane filtration, reverse osmosis, electrocoagulation, chemical precipitation, etc. are in use to remove metals from water sources but are not practically feasible in many aspects. The application of low cost adsorbents for metal remediation has been extensively investigated as an alternative for uneconomical, unconventional, and tedious approaches of eliminating metals from an aqueous solution. Many researchers have carried out the synthesis of adsorbents derived from agricultural waste (neem bark, rice husk, orange peel, etc.), industrial waste (fly ash, waste slurry, etc.), household waste (waste tea, etc.) and some other materials like chiton, biochar, activated carbon, etc. Some of the highest reported low-cost adsorbent with maximum adsorption capacity for removal of metals are Anadara inaequivalvis shells (Copper), orange peel (Nickel, Lead, Cadmium), crab shell particles (Cobalt), oyster shells (Zinc), pistachio hull waste (Chromium), Ganga sand (copper, iron). In this chapter, various adsorbents have been investigated to evaluate the most effective material and method for metal remediation as a sustainable approach to ensure environmental safety.
Mixing iron ore tailings with clay for manufacturing bricks was investigated
with the objective of converting the hazardous solid waste into useful
products. Blocks were prepared using different compositions of iron ore tailings and
clay in 70.6 mm cubic moulds. They were sundried and then placed in a furnace at
110 °C for 24 h to remove water. The dry blocks were fired at temperatures ranging
from 900 to 1050 °C for 3 h. Characterization of tailings, clay, and sintered blocks
was done. Mechanical properties such as compressive strength, water absorption
rates, loss on ignition, and bulk density were measured. The maximum compressive
strength of 25.40 MPa was recorded for tailing and clay ratio of 40:60 sintered at
950 °C. This compares very well with the best quality bricks in India. The results
also indicate that the percentage of tailings in the blocks influences their mechanical
properties. The water absorption rates of the sample blocks are low compared to
clay and fly ash bricks, and the same varies with process parameters. The low
porosity may deter the formation of efflorescence. The process, with standardized
parameters, may be commercially adapted, and large quantities of iron ore tailings
may be put to use in making bricks. Thus, the process technology delineated in this
paper can potentially convert the huge amount of environmentally harmful useless
waste into wealth. Iron ore tailing may emerge as a sustainable supplement to clay,
use of which in brick making is increasingly being restricted. The work also paves
the way for a new strand of research.
Corncob is an agricultural scrap obtained in bulk quantities during the production of corn. This agriculture waste is a potential resource to act as a biosorbent for the removal of heavy metals. Therefore, the objective of this study is to highlight a structural and surface characterization of raw corncob, H3PO4−pretreated corncob, and KOH-pretreated corncob since modification of raw corncob with different methods may change the surface area and also the electrical nature and surface functional groups of corncob, the removal capability of corncob as adsorbent could also be affected. The biomass samples were characterized via Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET) analysis. The FTIR result shows that the major functional groups of corncob such as –OH, C–O, C–H, and C=C experienced a slight shift due to the presence of KOH and H3PO4. Treatments with KOH and H3PO4 improved the BET surface area with the values of 8.8920 and 6.7894 m2/g, respectively, compared with raw corncob (0.5011 m2/g). The results indicate that the pretreatment of corncob influenced the functional groups and surface area of the raw corncob. Improved surface area may increase the ability of the corncob as adsorbent in heavy metals removal.
Biosorption is an environment-friendly and economic technique to remediate heavy metals from aqueous systems. In the present study, Artocarpus heterophyllus seed powder was used as a biosorbent material to remove different heavy metals. The batch adsorption studies confirmed the higher removal percentage of the Artocarpus heterophyllus (jackfruit) seed powder for arsenic (As⁵⁺), cadmium (Cd²⁺), and chromium (Cr⁶⁺) while lower efficiency was observed for other heavy metals like copper (Cu²⁺), zinc (Zn²⁺) and nickel (Ni²⁺). Optimization of different process parameters was carried out and the optimum conditions were: adsorbent weight of 0.5g for the initial concentration of heavy metals as 40 μg/L, 30 mg/L, and 30 mg/L; contact time of 10 h, 8h, and 6h; process temperature from 25 to 30 °C; pH of 7, 7.5, and 7.5 for As⁵⁺, Cd²⁺, and Cr⁶⁺ respectively. The SEM-EDX, FTIR, and XRD studies before and after adsorption of heavy metals resulted in affirmative observations. The equilibrium data of the study was well fitted for Langmuir isotherm for As⁵⁺, Cd²⁺, and Cr⁶⁺, Freundlich for As⁵⁺and Cr⁶⁺, Dubinin-Radushkevich for Cd²⁺and Cr⁶⁺. The kinetic and thermodynamic study confirmed that the adsorption of all three heavy metals was following the pseudo-second-order kinetics with the endothermic and spontaneous process respectively. The cost analysis of the process confirmed that the whole process was cost-effective compared to other processes. Hence the Artocarpus heterophyllus seed powder was verified for its high heavy metal remediation efficiency from aqueous environments along with the added advantages of being eco-friendly and economic compared to other alternatives.
12 Toxic dyes are irrefutable effluent components of textile wastewater, so they have become a major 13 economic and health concern. With the purpose of efficient removal of textile dyes, multiple 14 nature-inspired adsorbents have been applied. Herein, raw corncob is proposed as a novel highly 15 efficient, low-price, and abundantly attainable adsorbent with the potential for uptake of methyl 16 red and methyl orange. Multiple experiments were carried out to optimize parameters including 17 pH, primary concentration, adsorbent dosage, temperature, and contact time. The adsorption was 18 raised with the mounting of the contact time and it was alleviated with the addition of initial 19 concentration. The foremost uptake of dye was apperceived at an acidic medium pH 4 for methyl 20 red and pH 1 for methyl orange. Scanning Electron Microscopy and Fourier Transform Infrared 21 Spectroscopy were employed to characterize the surfaces of corncobs. The well-fitted Langmuir 22 and Freundlich models (methyl red: R 2 = 0.9956 and methyl orange: R 2 = 0.9883) confirmed the 23 homogeneous monolayer adsorption process on the raw corncob surface. The obtained results 24 disclose that corncob is an effectual biosorbent for eliminating anionic dyes without the necessity 25 for any prior modifications. 26 J o u r n a l P r e-p r o o f 2 27
"When there is a decision of Smart, for what reason to pick just better." Eucalyptus bark and syzygium barks are very abundant, inexpensive and forest residues. It was decided to do experiment with it as a potential adsorbent for the removal of certain metals in industrial waste water. The efficiency of eucalyptus bark and syzygium cumini bark as a low cost sorbents for removing cadmium ions from aqueous solution has been investigated in batch mode. In order to study the variables that define the process, the variables selected were: Time, metal ion concentration, pH variation, Adsorbent dosage and particle size. Batch mode experiments were conducted to observe the effects of selected variables. It was verified that all the variables studied had significant influence on the adsorption process. Maximum cadmium uptake was obtained at 70 minutes for Eucalyptus bark and 60 minutes for Syzygium cumini bark. The equilibrium data could be well described by the Langmuir isotherm but a worse fit was obtained by the Freundlich model. Keywords: Eucalyptus bark, Syzygium cumini bark, adsorbent, cadmium, waste water.
Heavy metals (Cd, Cu, Pb) adsorption capacity experiments with a novel adsorbent Unfertilized Mango Flowering Buds (UMFB) were investigated in a batch scale studies at different constraints to obtain prime conditions of adsorption dose, initial metals concentration, contact time, pH, and temperature. The results showed that increasing the dosage of UMFB to 6 g/L enhanced the removal efficiency of Cd, Cu, and Pb to 82.46%, 65.74% and 74.99% respectively. The ideal bio-sorption limits were seen at pH 5-6 with efficiency up to 80.77%, 69.41% and 71.05% for Cd, Cu, and Pb respectively. The capacities of heavy metals removal, on the other hand, were found to be 14.51 mg/g of UMFB for Cd, 12.57 mg/g of UMFB for Cu, and 12.98 mg/g of UMFB for Pb. The ideal estimations of contact time were found at 120 min. The respective removal rates of Cd, Cu and Pb were 82.77%, 73.26%, and 79.64% while the respective adsorption capacities of Cd, Cu and Pb were 14.44, 12.65 and 13.07 mg/g. The highest accepted initial metal concentration that can achieve acceptable metal removal was not the same for the all tested metals: 100, 50, and 200 g/L for Cd, Cu, and Pb respectively. The results showed that the most suitable sorption temperature is at 40°C with a removal rate of 80.90% and 75.75% for Cd and Pb respectively, and at 60°C for Cu with a removal rate of 77.32%. The coexisting ions weakened the removal efficiency of Cd due to the intense competition for adsorption sites. Characterization of the UMFB has been conducted by scanning electron microscopic (SEM) images, before and after loaded of heavy metals , showed significant changes in the surface morphology, indicating the adsorption process had taken place. Fourier transform infrared spectroscopy (FTIR) indicates the organic functional groups which might be involved in the adsorption of heavy metals. Both pseudo-first and second-order models were used to evaluate the adsorption mechanism of different metals. It was found that information fitting best to pseudo-second-order model since the R 2 was almost equal to unity. The Cd, Cu, and Pb adsorption behavior on UMFB was a chemical homogeneous process fitting the Langmuir model (R 2 ≥ 0.98) better than Freundlich one.
The study was being planned with objectives in order to remove the chromium concentration in synthetic wastewater using rice husk and saw dust as adsorbent synthesized from agricultural waste. The study on the variation of removal efficiency under the effects of various parameters like adsorbent dose, initial concentration of metal, pH value and contact time, and further analysis is done using adsorption isotherms.
Bioadsorption is an organic technique as different bioadsorbents prepared from agricultural waste, forest waste, industrial waste and algae can be utilized for the greatest expulsion of substantial metals from wastewater. In the present study, an attempt has been made to remove the chromium concentration in synthetic wastewater using rice husk and saw dust as adsorbent synthesized from agricultural waste. The rice husk was collected from an agricultural production process industry and sawdust collected from the local wood shop was used for adsorption of chromium after grinding and then passing through a sieve size of 300 µm. The maximum chromium removal efficiency of 90.7% and 82% have been observed using rice husk and saw dust as adsorbent, respectively, with an adsorbent dosage of 3 g at an initial chromium concentration of 10 mg/L. The maximum Cr removal of 92.1% has been observed at a pH value of 6 and minimum Cr removal of 75.8% has been found at a pH value of 2 using rice husk as adsorbent. Also, the maximum Cr removal efficiency of 85% has been observed at pH 6 and minimum Cr removal efficiency of 55% has been observed at pH 2 using saw dust as an adsorbent. The adsorption isotherm Langmuir and Freundlich model has also been used in order to fit the obtained data. The correlation coefficients for the removal of chromium from aqueous solution using rice husk and saw dust adsorbent has also been computed. From the present study, it can be compared that the correlation coefficients indicates the fact that Langmuir isotherm provides a better model as compared to the Freundlich model for rice husk as an adsorbent. The adsorption in such a system is based on monolayer sorption on to the surface limiting the finite number of identical sorption sites.KeywordsHeavy metalRemoval efficiencyLow-cost adsorbentAdsorption isotherm
The total anaerobic digestion capacity has increased five-fold worldwide from
about two million metric tons in 1990 to over ten million by 2008. Several
studies based on the AD process claim the viability and feasibility of the process
in the improvement of biogas generation and sustainable handling of waste. Therefore, the present study has been undertaken with an objective to observe
methane production potential from biodegradation of industrial food waste under
psychrophilic, mesophilic and thermophilic conditions using batch type test study.
Furthermore, the study incorporates the calculation of the methane generation
rate constant (k) and Biochemical methane potential (BMP) under above-specified
conditions.
Aspergillus nidulans (accession number MT355567) was selected as a most potent isolated, dried and chemically pretreated biomass was investigated. Various biosorption parameters as pH, initial concentration of U, biosorbent dose, biosorbent particles size, temperature and contact time were studied. Maximum uranium removal efficiency was 97% and 98.5% for dried and chemically pretreated biomass, respectively. The optimum pH for U(VI) removal was 4.0 with U concentration 350 mg/L, biomass concentration 0.4 g, biomass size 0.250 mm within 16 and 14 min for dried and chemically pretreated biomass, respectively, at 25°C. Uranium biosorption was closely related to pseudo-second-order kinetic model and obeys the Langmuir isotherm model. Calculation were suggested that U biosorption was not endothermic. According to the calculation the hydroxyl, carboxyl and amino groups on the fungal surface could back to biosorption of U. Desorption of U from the metal laden (68% for dried biomass and 47.5% for chemical-treated biomass) was completely achieved by applying 2 M HNO3 although the U adsorption capacity of both biosorbents were decreased from 67.5% to 28% for dried biomass and from 47.3% to 26% for chemical-treated biomass after four biosorption–desorption cycles.
The wastewaters discharged from chemical industries which may contain heavy metal ions have toxic effect on all the living organisms. Because of this, disposal of them to the environment is a major threat to both human health and ecosystem. So the development of new technologies is required to treat wastewaters as an alternative to traditional physicochemical processes. Biosorption, the process of passive cation binding by dead or living biomass, represents a potentially cost-effective way of eliminating toxic heavy metals from industrial waste waters. While the abilities of microorganisms to remove metal ions in solution have been extensively studied, fungi have been recognized as a promising class of low-cost adsorbents for removal of heavy-metal ions from aqueous waste streams. Algae, fungi and bacteria differ from each other in their constitution, giving rise to different mechanisms of metal biosorption. The paper reviews the biosorption capacities of various fungi (free or immobilized or subjected to physical and chemical treatments) and, chitin and chitosan, important fungal cell wall components, in different reactor systems for heavy metal ions and discusses the fungal biosorption mechanisms. To explore the biosorption mechanisms, it is necessary to identify the functional groups involved in the biosorption process. As single toxic metallic species rarely exist in natural and waste waters, any approach that attempts to removal heavy metals from multi-component systems using fungi would be more realistic. The effects of various combinations of the metal ions on the biosorption capacity of various fungi are discussed and the actions of the metal ion combinations synergistic or antagonistic are identified. Equilibria and capacity relationships for mono-component systems are well established and quantitatively expressed by various types of adsorption isotherms. In the case of multi-metal systems, models should be modified in order to take into account all metals and cover experimental data over a wide range of solution concentrations. The researcher is often puzzled as to what are the basic differences or similarities between the isotherms and what isotherm to select for practical use to predict adsorption capacities or to incorporate it in predicting breakthrough of columnar operations. The paper reviews the range of equilibrium sorption models, and diffusion and sorption models in different reactor systems used by different researchers to correlate experimental data for fungal biosorption.
A series of activated carbons with different degrees of activation were oxidized with H2O2, (NH4)2S2O8 and HNO3 in order to introduce different oxygen surface complexes. Changes in the surface chemistry of the activated carbons after their oxidizing treatments were studied by different techniques including temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FTIR), titrations with HCl and NaOH, measurements of the pH of the point of zero charge and catalytic dehydration of methanol. Results showed that treatment with (NH4)2S2O8 fixed the lowest amount of both total oxygen and surface acid groups. However, this treatment yielded the acid groups with the highest acid strength. This could be because it favors fixation of carboxyl groups close to other groups, such as carbonyl and hydroxyl, which enhances their acidity.
Retention rate of Cr(VI) and Hg(II), from an aqueous medium by activated carbons obtained from peach stones and Eucalyptus globulus chips, is reported. To describe the retention rate of these ions, the effects of the activated carbon preparation variables: activating agent (steam and CO2), and burn-off, are analyzed. In addition, the effect of the following adsorption process variable: initial concentration of the metallic ion, system temperature, pH of the medium and particle size of the adsorbent is discussed. Cr(VI) was retained at a higher rate in E globulus-activated carbon than in peach stone-activated carbon due to the higher volume of the transport pores in the former material. The retention rate appears to include a micropore diffusional control in the Hg(II) retention and a transport pore diffusion control in Cr(VI) retention. The retention rate of Hg(II) is also dependent on chemical functionality of the activated carbon surface and the retention is enhanced when carbon dioxide is used as activating agent, whereas Cr(VI) retention is higher when steam activation is used.
The adsorption isotherm of cadmium on activated carbon was measured in a batch adsorber. Effects of temperature and solution pH on the adsorption isotherm were investigated by determining the adsorption isotherm at temperatures of 10, 25, and 40°C and at initial pH values from 2 to 8. Langmuir isotherm better fitted the experimental data since the average percent deviation was lower than with the Freundlich isotherm. It was noticed that the amount of Cd2+ adsorbed was reduced about 3 times by increasing the temperature from 10 to 40°C. It was found that Cd2+ was not adsorbed on activated carbon at pH of 2 or lower and that Cd2+ was precipitated out as Cd(OH)2 at pH values above 9. Maximum adsorption capacity was observed at pH of 8 and the adsorption capacity was decreased about 12 times by reducing the initial pH from 8 to 3. According to the cadmium speciation diagram the predominant species below pH of 8 is Cd2+. Thus, cadmium was adsorbed on the activated carbon surface as Cd2+. It was concluded that the adsorption capacity is a strong function of pH and temperature.
Bark, a common waste product in forestry, can be used to selectively remove cations, especially toxic heavy metals from mono or multi saline solutions. Picea, Pinus, Pseudotsuga, Larix, Tectona and Afzelia barks have been used in glass columns, after grinding and treatment with formaldehyde in acid media, to study their ability in binding toxic heavy metal ions such as Pb, Zn, Cr, Fe and Cu. The metals are exchanged against protons on the bark substrates that presumably contain carboxyl groups in both pectin and tannin compounds.Removal of these ions depends upon the nature of the bark used, the grain size and the predominant heavy metal ions present in the solutions. The metal ions could be stripped by addition of 0.1 ? HCl, making the substrate regeneration and its reutilization possible.
The effectiveness of peat in adsorbing copper, nickel and zinc from wastewater was studied. Batch kinetic and isotherm studies were carried out to determine the effects of contact time, pH, initial concentration of the adsorbate, and temperature on adsorption. It was found that a contact time of two hours was necessary for the adsorption to reach equilibrium. The optimum pH was found to be between 4.5 and 5.0. The data for the adsorption of copper, nickel and zinc were described well by both the Langmuir and the Freundlich models. The adsorption process was found to be exothermic.
A pseudo-second order rate equation describing the kinetics of sorption of divalent metal ions onto sphagnum moss peat at different initial metal ion concentrations and peat doses has been developed. The kinetics of sorption were followed based on the amounts of metal sorbed at various time intervals. Results show that sorption (chemical bonding) might be rate-limiting in the sorption of divalent metal ions onto peat during agitated batch contact time experiments. The rate constant, the equilibrium sorption capacity and the initial sorption rate were calculated. From these parameters, an empirical model for predicting the sorption capacity of metal ions sorbed was derived.
Sawdust and water hyacinth are waste products which have no economical application in Egypt. They even constitute a solid waste as far as the environment is concerned. As-received sawdust and water hyacinth were treated with phosphoric acid, phosphoric acid + urea or phosphoric acid + urea + dimethylformamide. The as-received and treated samples were used for the removal of Methylene Blue, iodine, phenol and ammonia from their aqueous solutions.
The optimum conditions for the maximum adsorption of each pollutant were determined. The isotherms obtained obeyed the Freundlich and Langmuir equations in a satisfactory manner. The initial stages of adsorption follow first-order kinetics as predicted from the Lagergren equation. Sawdust and water hyacinth show promising potentialities for the removal of pollutants from water and can, at least, be used as precursors for the preparation of efficient adsorbents for the removal of pollutants from water.
The integrity of ion exchange media used under conditions of different times of use, temperatures and pH values is important in its selection. This study was conducted to quantify the lack of integrity (attrition) in base-extracted (BE), citric acid (CA)-modified soybean hulls, a lignocellulosic cation exchange material and compare its attrition to two synthetic, commercial cation exchange resins. Attrition was determined in both batch and column operations. Batch studies included measuring attrition over a 24 h period under conditions of constant pH, variable pH and at different temperatures. Under conditions of a constant pH of 4.8, 25°C and using a stir bar, modified hulls had mostly lower attrition than the two commercial products. Under acidic conditions, modified hulls demonstrated very low (
The adsorption capacity of untreated, chemically and physically activated tyre rubber towards Cu2+ ions was studied. A comparison between these three types of adsorbent was performed in terms of dynamic and equilibrium considerations. The adsorption capacity of physically activated rubber was (marginally) greater than that of chemically activated rubber which, in turn, was greater than that of the untreated materials. The effects of activation temperature and time were considered in the physical activation process. Up to 97% of the Cu2+ ions were adsorbed from aqueous solution when untreated, chemically or physically activated tyre rubber was employed as an adsorbent with initial metal concentrations of 20 mg/ml and 40 ppm, respectively. Increasing the adsorbent concentration resulted in a greater removal of metal ions from the aqueous solution, and increasing the Cu2+ ion concentration in the presence of a constant adsorbent concentration increased the metal ion loading per unit weight of the adsorbent. An increase in the initial pH value of the metal solutions enhanced the adsorption process with all three adsorbents tested. It was demonstrated that the Freundlich and Langmuir isotherms were capable of describing the adsorption of Cu2+ ions by the adsorbents under consideration reasonably well.
The effect of temperature on the adsorption isotherms for cupric and cadmium ions by corncob particles was investigated. The uptake of the two types of ions by corncob particles increased with temperature in the ranges between 25°C and 65°C and between 15°C and 65°C for copper and cadmium, respectively. In addition, a study on the competitive adsorption of copper and cadmium ions from their mixture by the adsorbent was also conducted. The tests showed that the uptake of copper ions in the mixture increased with increasing the total metal ion concentration. However, the uptake of cadmium ions from the mixtures first increased, reached a maximum point, and then decreased with increasing the total metal ion concentration resulting in inversed U‐shape isotherms. To describe these inversed U‐shape isotherms, a new competitive adsorption model with interaction factors was proposed and its constants were estimated. From the tests, it can be concluded that the cupric ions had stronger affinity than the cadmium ions for the corncob particles during the competitive adsorption.
Activated carbon prepared from peanut hulls (PHC), an agricultural waste by-product, has been used for the adsorption of Cd(II) from synthetic wastewater. The adsorption data fit better with the Freundlich adsorption isotherm. The applicability of the Lagergren kinetic model has also been investigated. An almost quantitative removal of 20 mg/L Cd(II) by 0.7 g of PHC/L of aqueous solution was observed in the pH range 3.5--9.5. A comparative study with a commercial granular activated carbon (CAC) showed that the adsorption capacity (K[sub f]) of PHC was 31 times larger than that of CAC.
Surplus, low value agricultural by-products can be made into granular activated carbons (GACs) which are used in environmental remediation. This study characterized and evaluated GACs, made from these feedstocks, as effective removers of organics and metals from water. The by-products included soft lignocellulosics such as rice straw, soybean hull, sugarcane bagasse, peanut shell, and harder materials such as pecan and walnut shells. The softer materials were combined with a binder, molasses, to produce briquettes and pellets. The precursors were CO2- or steam-activated, and subsequent treatments included oxidation to enhance metal adsorption. Many of the GACs had acceptable physical GAC attributes, such as durability, for commercial usage. GACs made from pecan and walnut shells adsorbed higher levels of benzene, toluene, methanol, acetonitrile, acetone, and 1,4-dioxane from an aqueous mixture than commercial GACs. Neither CO2 nor steam activation was particularly advantageous in enhancing metal adsorption. Oxidation using O2–N2 gas increased metal adsorption while (NH4)S2O8 solution did not. In a copper solution, oxidized GACs made from soybean hull had three to four times the Cu(II) adsorption capacity of metal-adsorbing, commercial GACs. Oxidized GACs made from soybean hull, sugarcane bagasse, peanut shell, and rice straw adsorbed from a mixture higher amounts of Pb(II), Cu(II), Ni(II), Cd(II) and Zn(II) than any commercial GACs. Commercial GACs adsorbed only Pb(II), Cu(II) and Cd(II). The GACs made from the agricultural by-products have considerable potential for adsorption of organics and metals of environmental concern. © 1998 SCI.
The removal of trivalent chromium from solutions using biosorption in cork powder is described. The adsorption isotherm was determined, along with the effect of different variables, such as biomass particle size, solid–liquid ratio, reaction time, metal concentration and pH, on the efficiency of chromium removal. It was concluded that the adsorption is slow and favoured by an increase in pH. Therefore, using a solid–liquid ratio of 4 g dm ⁻³ it is possible to reduce the chromium concentration in the solution from 10 mg dm ⁻³ to less than 1.5 mg dm ⁻³ in 2 h at 22 °C. The kinetic studies verified that the sorption of chromium by cork was described by a second‐order model. The elution results showed that 50% of the chromium bound to the cork was eluted using 0.5 mol dm ⁻³ H 2 SO 4 and that cork maintains its binding capacity over four cycles of biosorption/elution.
© 2002 Society of Chemical Industry
Dried ground bagasse, impregnated with 50% inorganic acids and carbonized at 500°C, showed the sequence H3PO4 > H2SO4 > HCl > HNO3, with respect to the efficiency of activation. Treatment with phosphoric acid of various concentrations (30–50 wt%) was followed by carbonization at 300–500°C for 3 h. Pore structure parameters were determined from the low-temperature adsorption of nitrogen, by applying the BET and αs methods. Activated carbons obtained at low temperatures are essentially microporous with a low degree of mesoporosity. At higher temperatures products of higher surface area and total pore volume with developed mesoporosity and low microporosity are formed. An increase in the period of carbonization leads to a small decrease in both surface area and pore volume. Activated carbons with surface areas > 1000 m2 g−1 and mean pore dimensions around 2·0 nm, suitable for various purposes, are thus obtained.
Activated carbons were prepared by ZnCl2/CO2 and other salt solutions/CO2 activation of the rice husk. The products were characterized in terms of density, elemental analysis, specific surface area, and porosity. The specific surface area of activated carbon is 480 m2 g−1, porosity diameter is 0.0044 μm, specific pore volume is 1.3652 cm3 g−1. The surface area and the nature of the porosity of the resulting activated carbons were found to be related to the concentration and type of the impregnated salt solutions.
Peat has been investigated by several researchers as a sorbent for the capture of dissolved metals from wastestreams. Besides being plentiful and inexpensive, peat possesses several characteristics that make it an effective media for the removal of dissolved metal pollutants. The mechanism of metal ion binding to peat remains a controversial area with ion-exchange, complexation, and surface adsorption being the prevalent theories. Factors affecting adsorption include pH, loading rates, and the presence of competing metals. The optimum pH range for metals capture is generally 3.5–6.5. Although the presence of more than one metal in a solution creates competition for sorption sites and less of a particular ion may be bound, the total sorption capacity has been found to increase. Studies have also shown that metals removal is most efficient when the loading rates are low. In addition, recovery of metals and regeneration of the peat is possible using acid elution with little effect on peat’s sorption capacity.The utilization of peat and other biomass materials for the treatment of wastewater containing heavy metals is gaining more attention as a simple, effective and economical means of pollution remediation. Pelleting processes can now produce a robust media for a variety of applications where traditional methods of pollutant removal would be economically or technologically difficult.
Corn fiber (CF) was allowed to react thermochemically with citric acid (CA) to yield potentially biodegradable products possessing high ion-exchange capacity. The reaction variables studied were: citric acid level (0–100 g), reaction time (0–24 h), pH (1.5–8.3) and temperature (110–140 °C). Moisture content and pH were found to be controlling factors. Reaction efficiencies approaching 100% were achieved, while minimizing cross-linking and maximizing carboxyl content. Carboxyl content (0.5–3.6 mmol/g) was determined and copper-binding capacity (0.1–2.0 mmol/g) at pH 4.5 was evaluated for the various CF-CA products.
Coir pith, a by-product from coir fibre industries was used as a raw material to prepare activated carbons by physical and chemical activation methods. The physico-chemical characteristics of activated carbons obtained by different methods are reported.
A method for characterization of carbon surfaces' acidity using a continuous distribution of acidity constants is proposed. The method is based on potentiometric titration measurements. Titration curves are transformed into proton adsorption isotherms, and are analyzed to yield the distribution of acidity constants. Calculation of the distribution function is sensitive to experimental errors, and therefore a careful smoothing treatment must be applied to the experimental data. The method is tested by application to organic compounds and the calculated pK values are in excellent agreement with literature data. The method is then applied to study the evolution of acidic groups, in terms of their pK values, subsequent to modification processes such as oxidation and reduction of activated carbons. It is demonstrated that the method is sensitive to the changes in the number and character of surface acidic groups.
The abilities of native and modified sugar beet pulps to remove Ni(II) and Cu(II) ions from aqueous solutions were compared. Their preparation by chemical treatments (saponification, hot 0.05 M HCl and cold 0.05 M NaOH extractions) is described. The sugar composition, which was strongly affected during these modifications, is discussed in terms of metal sorption efficiencies. The influence of these modifications was also evaluated by comparing the content of the functional groups determined by potentiometric titration, and the rate and extent of Cu(II) and Ni(II) uptakes onto the raw and modified materials. Nickel and copper sorptions were fast and complete within 30 min and the kinetic parameters were calculated using a second order model. The equilibrium data fitted well with the Langmuir model and showed the affinity order of the materials for the metal ions. The base-extracted pulp and saponified pulp exhibited the highest Ni(II) and Cu(II) ion uptakes among the materials tested.
A review is given on the surface chemistry of carbon blacks and other carbons, in particular, activated carbons. The main part is devoted to surface oxides with emphasis on the chemical methods used in the assessment and identification of surface functional groups. Their formation under mild conditions and the influence of water vapor and metal catalysts on the reaction with air (“aging” of carbons) are described. Reaction with free organic radicals can be used for the functionalization of carbon surfaces.
The declared objective of this book is to provide an introductory review of the various theoretical and practical aspects of adsorption by powders and porous solids with particular reference to materials of technological importance. The primary aim is to meet the needs of students and non-specialists who are new to surface science or who wish to use the advanced techniques now available for the determination of surface area, pore size and surface characterization. In addition, a critical account is given of recent work on the adsorptive properties of activated carbons, oxides, clays and zeolites.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.
The adsorption of three heavy metal ions by pine bark was studied. The study was divided into two parts; single component adsorption of the metals Cu2+, Cd2+ and Ni2+ and bisolute adsorption of the three binary systems Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+. Extended Langmuir model, extended Freundlich model. Sips model and ideal adsorption solution theory (IAST) models were used to predict the equilibrium uptake for Cu2+, Cd2+ and Ni2+ in the binary diluted solutions using the single adsorption constants. The experimental data of single isotherm adsorption process were found to follow Langmuir isotherm model with less accuracy than Freundlich and Sips models. Whereas, the predictions of bisolute adsorption isotherms of the mentioned three systems, Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+, showed good agreement with experimental data when using Extended-Langmuir, Extended-Freundlich and IAST. However, the only good fit of the Sips model was with the Cu2+-Cd2+ system.
The objective of this study was to convert corncobs to metal ion adsorbents for wastewater treatment. Ground corncobs were modified with either 0.6 M citric acid (CA) or 1.0 M phosphoric acid (PA) to help improve their natural adsorption capacity. The effect of a combination of wash and modification treatment was tested for corncob adsorption efficiency with five different metal ions (cadmium, copper, lead, nickel, zinc) individually or in a mixed solution containing each metal at a 20 mM concentration. Results were compared to those of commercial resins Amberlite IRC-718, Amberlite 200, Duolite GT-73 and carboxymethylcellulose (CMC). Modified corncobs showed the same adsorption efficiency as Duolite GT-73 for cadmium, copper, nickel and zinc ions and had greater adsorption than CMC for nickel and zinc ions. For mixed metals, the modified corncobs exhibited the same adsorption efficiency as Duolite GT-73 for cadmium and copper ions and the same or higher adsorption than Amberlite IRC-718 for lead ions. Adsorption capacities of modified samples were compared to those of Amberlite IRC-718, Amberlite 200 and Duolite GT-73. Commercial resins generally had higher adsorption capacities than modified corncobs. However, the adsorption capacity of modified corncobs for copper and lead ions was equivalent to Duolite GT-73, but was lower than for Amberlite IRC-718 or Amberlite 200. Depending on the specific metal ion and the presence or absence of other metal ions, chemically modified corncobs were at least equivalent in adsorption properties to all of the commercial cation exchange resins examined in this study.
Production of granular activated carbon by chemical activation has been attempted employing walnut shells as the raw material. The thermal characteristics of walnut shell were investigated by TG/DTA and the adsorption capacity of the produced activated carbon was evaluated using the titration method. As the activation temperature increased, the iodine value increased. However, a temperature higher than 400 degrees C resulted in a thermal degradation, which was substantiated by scanning electron microscopy (SEM) analysis, and the adsorption capacity decreased. Activation longer than 1h at 375 degrees C resulted in the destruction of the microporous structure of activated carbon. The iodine value increased with the increase in the concentration of ZnCl2 solution. However, excessive ZnCl2 in the solution decreased the iodine value. The extent of activation by ZnCl2 was compared with that by CaCl2 activation. Enhanced activation was achieved when walnut shell was activated by ZnCl2. Applicability of the activated carbon as adsorbent was examined for synthetic copper wastewater. Adsorption of copper ion followed the Freundlich model. Thermodynamic aspects of adsorption have been discussed based on experimental results. The adsorption capacity of the produced activated carbon met the conditions for commercialization and was found to be superior to that made from coconut shell.
Adsorption isotherms were measured experimentally for Zn(II) adsorption from aqueous solution onto commercial activated carbons C, F-400, F-300 and Centaur HSL in a batch adsorber. The effects of carbon type and solution pH on adsorption isotherms were evaluated in this work. Nearly three times as much Zn(II) adsorbed onto C carbon as on the other three carbon types. The adsorption isotherm for Zn(II) was dependent on solution pH since Zn(II) did not adsorb to carbon below pH 2, and the adsorption isotherm increased as pH increased from 3 to 7. The adsorption isotherm of Zn(II) on C carbon was temperature independent while on F-400 the isotherm showed unusual behavior as temperature increased.
The surface of activated carbon cloth (ACC), based on polyacrylonitrile fibre as a precursor, was oxidised using nitric acid, ozone and electrochemical oxidation to enhance cadmium ion exchange capacity. Modified adsorbents were physically and chemically characterised by pH titration, direct titration, X-ray photoelectron spectroscopy, elemental analysis, surface area and porosimetry, and scanning electron microscopy. BET surface area decreased after oxidation, however, the total ion exchange capacity increased by a factor of approximately 3.5 compared to the commercial as-received ACC. A very significant increase in cadmium uptake, by a factor of 13, was observed for the electrochemically oxidised ACC. Equilibrium sorption isotherms were determined at pH 4, 5 and 6 and these showed that cadmium uptake increased with increasing pH. There was clear evidence of physical damage to ozone-oxidised fibre, however, acid and electrochemically oxidised samples were completely stable.
Formaldehyde pretreated Pinus pinaster bark was used to sorb Cd2+ and Hg2+ from aqueous solutions. The sorption kinetics showed hyperbolic dependence of the proportion of cation adsorbed on time, and the sorption isotherms were satisfactorily fitted by Freundlich equations, with k and n values showing Hg2+ to be more efficiently sorbed than Cd2+. Except for low cation concentrations, for which sorption was practically total at all initial pH > or = 6, sorption increased in this range, in keeping with a mechanism based on ion exchange with the hydroxyl protons of ring B of the procyanidin units of the tannins in the bark.
Sugar beet pulp generated by sugar-refining factories has been shown to be an effective adsorbent for the removal of heavy metals from aqueous solutions. The structural components related to the metallic adsorption being determined, batch adsorption studies were performed for several metal ions, namely, Pb2+, Cu2+, Zn2+, Cd2+, and Ni2+ cations. Two simple kinetic models, that is, pseudo-first- and pseudo-second-order, were tested to investigate the adsorption mechanisms. The kinetic parameters of the models were calculated and discussed. For an 8 x 10(-4) M initial metal concentration, the initial sorption rates (v0) ranged from 0.063 mmol x g(-1) x min(-1) for Pb2+ to 0.275 mmol x g(-1) x min(-1) for Ni2+ ions, in the order Ni2+ > Cd2+ > Zn2+ > Cu2+ > Pb2+. The equilibrium data fitted well with the Langmuir and Freundlich models and showed the following affinity order of the material: Pb2+ > Cu2+ > Zn2+ > Cd2+ > Ni2+. The metal removal was strongly dependent on pH and, to a lesser extent, ionic strength. Ion exchange with Ca2+ ions neutralizing the carboxyl groups of the polysaccharide was found to be the predominant mechanism, added with complexation for Pb2+, Cu2+, and Zn2+ metals.
Sugar beet pulp, a common agricultural waste, was studied in the removal of metal ions from aqueous solutions. Potentiometric titrations were used to characterize the surface acidity of the polysaccharide. The acid properties of the material can be described by invoking three distinct types of surface functional groups with the intrinsic acidity constants (pKa(int)) values 3.43+/-0.1, 6.05+/-0.05, and 7.89+/-0.1, respectively. The contents of each functional group (i.e., the carboxyl and phenol moieties) were also determined. Then, a simple surface complexation model with the diffuse layer model successfully described the sorption of several metal ions (Cu2+, Zn2+, Cd2+, and Ni2+) onto the polysaccharide under various experimental conditions: pH ranging from 2 to 5.5, ionic strength from 0.01 to 0.1 M, metal concentration between 10(-4) and 10(-3) M, for a constant sorbent concentration equal to 2.5 g x L(-1). It was observed experimentally that the affinity of the polysaccharide was in the sequence of Cu2+ > Zn2+ > Cd2+ > Ni2+. Predictions of sorption in binary-metal systems based on single-metal data fits represented competitive sorption data reasonably well.
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