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Removal of Hexavalent chromium by using citric acid modified Tamarind pod shell powder Tamarindus indica L.
... Mopoung et al. [92] fabricated activated carbon from tamarind seed by activation with a base, i.e., KOH instead of an acid, for the study of Fe (III) adsorption, taking varying ratios of KOH and tamarind seed charcoal which indicated that the percent yield of activated carbon ranges from 54.09 to 82.03 wt% using impregnation ratios of KOH and activated carbon from tamarind seed as 0.5: 1-1.5: 1. The adsorption of Cr (VI), Zn (II) and Cd(II) from aqueous solutions by crude tamarind fruit shell (CTFS), HCl treated shell (H-TS), oxalic acid treated shell (O-TS) [93], tamarind hull-based adsorbent [94], Tamarindus indica seeds [95], Tamarindus indica pod shells [96], citric acid-modified tamarind pod shell [97,98], tamarind fruit shell adsorbent [99] and phosphorylated tamarind nut carbon (PTNC) [100] was investigated by different groups of researchers. A common conclusion can be drawn for the analysis of these adsorbents that impregnated or modified tamarind increases the adsorption efficiency of the adsorbent as it always leads to an increase in surface area. ...
Large-scale industrialization and urbanization have led to such an alarming level of water contamination throughout the world that wastewater management has become one of the major global challenges attracting much research attention in recent times. Various techniques have been adopted for the treatment of polluted water among which adsorption has been preferred on a larger scale by virtue of its ease and cost-effective nature. This review highlights the efficiency of tamarind-based nanocomposites as potential adsorbents for a varying range of harmful organic and inorganic water pollutants including metal ions, fluoride ions and numerous kinds of dyes. A comprehensive analysis of fabrication routes, adsorption isotherms, kinetic and thermodynamic modeling as well as the adsorption mechanism and recyclability of these adsorbents is being presented in this work. In addition, various factors affecting the adsorption behavior such as pH, amount of adsorbent, concentration of ion/dye and influence of contact time are being elaborately outlined. The comparison of different composites on the basis of their effectiveness, selectivity, economic and environmental aspects has also been outlined. Moreover, a brief comparison of tamarind-based nanocomposites with other nanomaterials has also been included with respect to their efficiency in removal of water pollutants. Based on the data collected from a good number of literatures being surveyed, a great scope of future research on tamarind-based nanocomposites as alternative low-cost biomaterials in the field of water purification can be perceived.
Hazardous contamination of water is a major hurdle in the provision of usable and drinkable water to the world. Innovative, economic, renewable and environment friendly technologies are need of the hour for wastewater treatment. Several technologies such as ion-exchange, co-precipitation, adsorption, membrane separation, oxidation, biochemical processes etc. are being researched to encourage the wastewater treatment. Among these technologies, the adsorption is being considered as a promising approach owing to its short route. To adsorb the pollutants, different types of adsorbents are synthesized and utilized for wastewater treatment. The bio-adsorbents (BAs) from waste biomass sources are renewable, sustainable, economical, and ecofriendly for wastewater treatment. Among other biomass waste sources, fruit-based biomass wastes are on rise due to global food and fruit demand. The utilization of fruit wastes for the development of BAs have received high attention due to their low cost, rich in bio cellulose and abundance. Herein, we report a comprehensive review on the fruit waste derived bio-adsorbents for wastewater treatment. The manuscript includes synthesis, characterizations, and utilization of fruit waste derived bio-adsorbents for removal of various water contaminants. Characteristics, adsorption capacities, isotherms and adsorption kinetics of various bio-adsorbents and influence of parameters on adsorption is provided and critically analyzed.
Pomegranate peels were used to remove zinc, chromium and nickel from industrial wastewater. Three forms of these peels (fresh, dried small pieces and powder) were tested under some environmental factors such as pH, temperature and contact time. The obtained results showed that these peels are capable of removing zinc, chromium and nickel ions at significant capacities. The powder of the peels had the highest capability in bioremoving all zinc, chromium and nickel ions while dried peels had the lowest capacity again for all metals under test. However, the highest capacities were found in a sequence of chromium, nickel and zinc. Furthermore, all these data were significantly (LSD peel forms = 2.761 mg/l, LSD metal ions = 1.756 mg/l) varied. In case of chromium, these figures were 69.7 ± 0.9 mg/l, 58.0 ± 2.4 mg/l and 49.7 ± 0.5 mg/l for powder, fresh and dried peels respectively. Regarding nickel ions, the data were 58.7 ± 1.1 mg/l for peel powder, 50.7 ± 2.0 mg/l for fresh peel and 42.0 ± 1.2 mg/l for dry peel. While for zinc ions, the biosorption capacity was 48.4 ± 2.2 mg/l, 39.4 ± 0.8 mg/l and 32.0 ± 1.6 mg/l for powder, fresh and dry peels respectively. However, some examined factors were found to have significant impacts upon bioremoval capacity of pomegranate peels such as pH, temperature, and contact time where best biosorption capacities were found at pH 4, with temperature 50 Cº and contact time of 1 hour. Regarding pH, the highest bioremoval ability was found at pH 4 for all heavy metals, but with the sequence of Cr, Ni, and Zn and the data were 68.1 ± 1.5 mg/l, 56.0 ± 0.5 mg/l and 47.88 ± 1.21 mg/l respectively. Similar pattern of bioremoval capacity was detected for temperature which was 50 Cº giving capacities of 72.0 ± 0.0 mg Cr/l, 60.0 ± 1.84 mg Ni/l and 54.0 ± 1.72 mg Zn/l. In case of contact time, these capacities were again similar to those of pH and temperature and found to be 76.0 ± 3.0 mg/l , 64.0 ± 1.82 mg/l and 60.0 ± 2.0 mg/l for Cr, Ni, and Zn respectively but at 1 hour contact time.
This paper focuses on how the surface chemical groups of sheep manure affect the adsorption capacity of cobalt ions. Improvement in cobalt ions uptake onto sheep manure was achieved successfully by introducing more carboxylic functional groups into its surface due to citric acid treatment. According to Langmuir model, cobalt ions uptake was increased from 22.88 mg/g for dried sheep manure (D-SM) to 37.45 mg/g when D-SM was treated with 0.6 M citric acid (C-SM). Point of zero charge and cation exchange capacity were determined and found as 4.3 and 82 meq/100g for D-SM while it was found as 3.4 and 281 meq/100g for C-SM, respectively. The effects of process parameters such as solution pH, initial concentration of cobalt ions, contact time and concentration of citric acid on the uptake of cobalt ions were also investigated. Langmuir and Freundlich models were applied to the experimental data. Both models fitted quite well with the experimental data.
Macadamia nutshell biosorbents treated in three different activating agents [raw Macadamia nutshell powder (RMN), acid-treated Macadamia nutshell (ATMN) and base-treated Macadamia nutshell (BTMN)] were investigated for the adsorption of hexavalent chromium [Cr(VI)] from aqueous solutions. Fourier transform infrared spectroscopy spectra of free and Cr(VI)-loaded sorbents as well as thermogravimetric analysis revealed that the acid and base treatments modified the surface properties of the sorbent. Surface characteristics were also evaluated by the scanning electron microscopy and surface area analyzer. The optimum conditions for the adsorption of Cr(VI) by sorbents were pH 2, contact time 10 h, adsorbent mass 0.2 g and concentration 100 mg L⁻¹. The equilibrium data were fitted into the Langmuir, Freundlich, Redlich–Peterson and Sips isotherms, and no single model could clearly explain the sorption mechanism. Maximum binding capacities of 45.23, 44.83 and 42.44 mg g⁻¹ for RMN, ATMN and BTMN, respectively, were obtained. The kinetic data were analyzed using the pseudo-first, pseudo-second and Elovich kinetic models, and it was observed that the pseudo-second-order model produced the best fit for the experimental data. Macadamia nutshell sorbents showed potential as low-cost adsorbent for the removal of Cr(VI) from aqueous solution.
The main objective of this work was to use the okra powder modified with citric acid as biosorbent for the removal of Cr(VI) from aqueous solutions. Samples of Cr(VI) solution were prepared by diluting the 100 ppm solution diluted from the 1000 ppm stock solution prepared with K 2 Cr 2 O 7 . The determination of Cr(VI) was performed spectrophotometrically by the method of complexation with 1,5-diphenylcarbazide, measuring the absorbance at a 540 nm wavelength. The experiments were conducted at 25 ± 1 °C; 2, 5, 7 and 8 initial pH; 10-240 minutes contact time and 0.05 g of adsorbent. The Freundlich and Langmuir models were used to fit the experimental data. The Freundlich model provided R 2 =0.9599, indicating adsorption on heterogeneous conditions. Analysis of fluorescence of X-rays, SEM and FTIR were used to prove the okra powder efficiency in the removal of Cr(VI) from aqueous solutions.
In this work, bean husk (BH) was used to remove Cr (VI) ion from synthetic aqueous solution. Batch experiments using closed plastic beakers were designed to obtain Cr (VI) ion sorption data. Bean Husk was modified by using citric acid. The parameter for modification was selected by trying different parameters such as time, temperature and citric acid quantity. In batch experiments, the influences of contact time, pH, adsorbent dose and initial chromium concentration was researched on adsorption process performance and adsorption isotherm for the equilibrium was studied on modified bean husk (MBH). The results showed that adsorption of Cr (VI) by (MBH) reached to equilibrium after 90 min and after that a little change of Cr (VI) removal efficiency was observed. Higher chromium adsorption was observed at lower pH such as pH around 2. The (MBH) in this study showed very good promise for practical applicability and can be an alternative biosorbent for the removal of Cr (VI) from aqueous solution.
Pistachio shell (Pistacia vera) (PS), a low-cost material, has been utilized for the removal of the Cr(VI) ions after treatment with citric acid. Batch experimental steps were applied to obtain Cr(VI) ion adsorption details for the equilibrium between Cr(VI) and modified pistachio shell (MPS). The influences of contact time, pH, adsorbent dose and initial chromium concentration on the adsorption performance of MPS was investigated in detail. The results displayed that adsorption of Cr(VI) by MPS reached to equilibrium after 2 h and after that a little change of Cr(VI) removal efficiency was observed. The sorption percent is higher at lower pH and lower chromium concentration. Two possible mechanisms for reduction of Cr(VI) to Cr(III) can be suggested in Cr(VI) removal. In the first mechanism, Cr(VI) is reduced to Cr(III) by surface electron-donor groups of the adsorbent and the reduced Cr(III) forms complexes with adsorbent or remains in the solution. This Cr(III) is not adsorbed by adsorbent at pH 1.8. But in second mechanism, the adsorption-coupled reduction of Cr(VI) to Cr(III) occurred on the adsorbent sites. The equilibrium sorption capacity of Cr(VI) ion after 2 h was 64.35 mg/g for MPS.
The low cost adsorbent palm oil fuel ash (POFA) derived from an agricultural waste material was investigated as a replacement of current expensive methods for treating wastewater contaminated by Pb(II) cation. Adsorption studies were carried out to delineate the effect of contact time, temperature, pH and initial metal ion concentration. The experimental data followed pseudo second order kinetics which confirms chemisorptions. The values of Langmuir dimensionless constant, R(L) and Freundlich constant, 1/n were less than 1 representing favorable process for adsorption. Thermodynamic parameters such as Delta G degrees, Delta H degrees and Delta S degrees, related to Gibbs free energy, enthalpy and entropy were evaluated. It was concluded that, chemically treated palm oil fuel ash (POFA) can be used successfully for adsorption of Pb(II) from aqueous solution.
The biosorption of Cd(II) by Moringa oleifera using a batch system and a continuous up flow mode in a fixed bed column was studied. Batch adsorption experiments were performed as a function of pH, biosorbent dose, contact time, volume of the solution, and initial metal concentration. The adsorption isotherms obtained fitted well into the Freundlich and Langmuir isotherms. The dynamic removal of cadmium by powdered seed of the Moringa oleifera was studied in a packed column. The effect of bed height (4 and 8 cm) and flow rate (2 and 5mL/min) on biosorption process was investigated and the experimental breakthrough curves were obtained. Results showed that by increasing the bed height and decreasing the flow rate, the breakthrough and exhaustion times increased. The break-through time was considered as a measure of the column performance. The maximum break-through time of 320 min was achieved at the operating condition of 2 mL/min influent flow rate and bed height of 8 cm.
Heavy metal ions (Pb2+, Cd2+, Mn2+, Cu2+, and Cr2O72−) were biosorbed by brown seaweeds (Hizikia fusiformis, Laminaria japonica, and Undaria pinnatifida) collected from the southern coast of South Korea. The biosorption of heavy metal ions was pH-dependent showing a minimum absorption at pH 2 and a maximum biosorption at pH 4 (Pb2+, Cd2+, Mn2+, and Cr2O72−) or pH 6 (Cu2+). Biosorption increased most noticeably for pH changes from 2 to 3. In the latter pH range, biosorption increased, because a higher pH decreased the electrostatic repulsion between metal ions and functional groups on the seaweed. In the pH range of 2 ∼ 4, biosorption of negatively-charged chromium species (Cr2O7−2) followed the pattern of positively-charged metal ions (Pb2+, Cd2+, Mn2+, and Cu2+). This suggests that the most prevalent chromium species were positively-charged Cr3+, reduced from Cr6+ in Cr2O7−2. Whereas positively-charged heavy metal ions (Pb2+, Cd2+, Mn2+, and Cu2+) reached a plateau after the maximum level, biosorption of chromium ions decreased noticeably between pH 5 and 8. Kinetic data showed that biosorption by brown seaweed occurred rapidly during the first 10 min, and most of the heavy metals were bound to the seaweed within 30 min. Equilibrium adsorption data for a lead ion could fit well in the Langmuir and Freundlich isotherm models with regression coefficients (R
2) between 0.93 and 0.98.
Walnut shell (WNS) (Juglans regia) has been utilised as an adsorbent for the removal of Cr(VI) ions from aqueous solutions after treatment with citric acid. The modification reaction variables, such as citric acid level (5–10 g), reaction time (0–24 h), and temperature (110–130 °C) were studied in batch experiments. The rate of adsorption was studied under a variety of conditions, including initial Cr(VI) concentration (0.1–1.0 mM), amount of adsorbent (0.02–0.20 g), pH (2–9), temperature and contact time (10–240 min). Adsorption of Cr(VI) is in all cases pH-dependent showing a maximum at equilibrium pH values between 2.0 and 3.0 for citric acid modified walnut shell (CA-WNS). The applicability of the Langmuir, Freundlich and D–R adsorption isotherms has been tested for the equilibrium. Maximum adsorption capacities of CA-WNS and untreated WNS under experimental conditions were 0.596 and 0.154 mmol/g for Cr(VI) ions, respectively.
Analysis of peat samples from four regions of the British Isles indicates that the concentrations of Al, Pb and common transition metals tend, as expected, to be higher in regions subject to industrial pollution, but that the concentrations of the non-transition metals Na, K, Mg, Ca and Zn tend to be higher in regions remote from industrial pollution. Humic acids were extracted from the most polluted and least polluted of the peat samples and some characteristics of these acids were compared with those of two commercial acids. Values for stability constants of complexes formed between humic acids extracted from peat and Cu2+, Zn2+ or Pb2+ have been obtained by an ion-exchange equilibrium method. Of the three metal ions examined, Pb2+ was found to form the most stable humic acid complexes, followed by Cu2+: this order agrees with the findings of Irving and Williams and of Bunzl. Implications to the binding of actinide and other heavy metal ions in aqueous humic acid are discussed.
The adsorption of Cr(VI) from aqueous solutions by commercial and lab-made high surface area (HSA)-activated carbons was investigated. Physiochemical factors such as equilibrium time, temperature and solution pH that affect the magnitude of Cr(VI) adsorption were studied. The HSA-activated carbons showed high performance for Cr removal, and their adsorption capacity is several times larger than that of commercial carbons. Both micropores and mesopores have important contribution on the adsorption. However, desorption is more dependent on the mesoporosity of activated carbons. Therefore, regeneration is easier for the carbon with high mesoporosity. As a result, the adsorption capacity of mesoporous carbon could be recovered over 97%, whereas 54% for highly microporous carbon.
Chromium (VI) is a major pollutant released during several industrial operations. In this paper, we discuss how tamarind (Tamarindus indica) pod shells, otherwise discarded as a waste material is used in the biosorption of Cr (VI) from aqueous solutions. Parameters like agitation time, adsorbent dosage and pH were studied at different initial Cr (VI) concentrations. The adsorption data fit well with Langmuir and Freundlich isotherm models. Desorption studies were performed at different concentrations of sodium hydroxide. The infrared spectra of the biomass revealed that hydroxyl, carboxyl and amide groups are involved in the uptake of Cr (VI).
The present study explores the sorption properties of shelled Moringa oleifera seeds (SMOS) for removal of two environmentally important oxidation states of chromium (trivalent and hexavalent) from an aqueous system on the laboratory scale. Sorption studies reveal the optimum conditions for the removal of 81.02%; Cr (III) and 88.15% Cr (VI) as follows: biomass dosage (4.0 g), metal concentration [25 mg/L for Cr (III); 50 mg/L for Cr (VI)], contact time (40 minutes) at pH 6.5 and 2.5 respectively. The adsorption data were found to fit well both the Freundlich and Langmuir isotherms. Characterization of the seed powder by FTIR showed the clear presence of amino acid moieties having both positively charged amino and negatively charged carboxylic groups and confirmed that biosorption involves amino acid-chromium interactions. SEM studies of native and exhausted [Cr (III) and Cr (VI)] treated SMOS revealed large spherical clusters having a pore area of 8.66 μm2 in the case of native SMOS while dense agglomerated etched dendrite type morphology have a pore area of 0.80 μm2 in Cr (III) and 0.78 μm2 in Cr (VI) treated SMOS The spent biosorbent was regenerated and found to be effectively reusable for four cycles.
Low cost mixed adsorbents have been used to study, the removal of Cu(II) at different concentrations, and pH of the solution. The uptake of Cu (II) is maximum by wollastonite‐china clay followed by fly ash‐wollastonite and fly ash‐china clay at the same concentration, temperature and pH of the solution. Equilibrium data of various systems at 30°C and pH 6.5 fit well in the Freundlich equation. Removal of Cu(II) increases with the pH of the solution and is maximum at pH 8.0. Significant desorption of Cu(II) from the surfaces of mixed adsorbents was noted at pH 2.0.
A new process, namely, IERECHROM (Ion Exchange REcovery of CHROMmium), has been developed for removal of Cr(III) ionic complex from segregated wastewaters (10% of the overall wastewaters discharged from tanning operations). The process is based on a macroporous carboxylic resin (i.e., Purolite C106) retaining the metal of reference, together with other trace metals, including aluminum and iron. In a first regeneration step, alkaline hydrogen peroxide (pH 12) is used. The anionic species formed (chromate and aluminate) are quantitatively eluted from the cation resin and separated. In a second polishing step of the resin, ferric species are eluted with 1 M sulfuric acid. The resulting ferric and aluminum sulfate solutions are recycled as flocculating agents. The residual chromate solution is directly reused in the plating industry or, after reduction to Cr(III), in the same tannery. Before the new exhaustion cycle, the resin is reactivated by elution of 1 M NaOH followed by hydrolysis with softened water. A 10 m³/day fully automated pilot plant was assembled, and process reliability and cost benefits were demonstrated.
The removal of poisonous Cr(VI) from industrial wastewater by different low-cost abundant adsorbents was investigated. Wool, olive cake, sawdust, pine needles, almond shells, cactus leaves and charcoal were used at different adsorbent/metal ion ratios. The influence of pH, contact time, metal concentration, adsorbent nature and concentration on the selectivity and sensitivity of the removal process was investigated. The adsorption process was found to follow a first-order rate mechanism and the rate constant was evaluated at 30°C. In the case of wool, the rate constant was the highest (39.6×10−3 min−1) and the cactus leaves gave the lowest value (6.8×10−3 min−1). Langmuir and Freundlich isotherms were applicable to the adsorption process and their constants were evaluated. The thermodynamic equilibrium constant and the Gibbs free energy were calculated for each system. The ΔGo for the absorption by wool (−2.26 kJ mol−1) and that for the cactus leaves (2.8 kJ mol−1) supported the findings that wool was the best among the selected adsorbents for the selective removal of Cr(VI) at pH 2 and an adsorbent concentration of 16 g l−1 at 30°C, for which the removal was 81% out of 100 ppm Cr(VI) after 2 h of stirring. A comparison between a simulated sample containing 100 ppm Cr(VI) and a true wastewater sample containing 100 ppm Cr(VI), 19 ppm Al, 30 ppm Mg, 49 ppm Ca, and 10 ppm B, showed that the adsorption process is satisfactory and selective for Cr(VI).
Chromium and cadmium are toxic heavy metals present in wastewaters from a variety of industries. A strong cationexchange resin, Amberlite IR 120, was used for the removal of chromium and cadmium. The resin was prepared in two different cationic forms, as Na+ and H+. The optimum conditions were concentration, pH, stirring time and resin amount. The concentration range was between 2–50 mg/L, pH range between 2–10, stirring time between 5–60 min, and the amount of resin was from 50–1000 mg. Exchange capacities, moisture content and optimum conditions of this resin were determined in a batch system. The stirring speed was 2000 rpm during all of the batch experiments. The initial and final chromium and cadmium amounts were determined by atomic absorption spectrophotometry. The optimum conditions were found to be a concentration of 20 mg/L, pH of 5.5, stirring time of 20 min and 100 mg of resin. The results obtained show that the Amberlite IR 120 strong cation-exchange resin performed well for the removal and recovery of chromium and cadmium.
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This paper reports the feasibility of using agricultural waste and timber industry waste carbons to remove Cr(VI) from synthetic wastewater under different experimental conditions. For this, rice husk and saw dust have been used as adsorbent after sulphuric acid treatment. Effect of various process parameters, namely, pH, adsorbent dose, initial chromium concentration and contact time has been studied in batch systems. Maximum metal removal was observed at pH 2.0. The efficiencies of rice husk carbon (RHC) and saw dust carbon (SDC) for Cr(VI) removal were 91.75% and 94.33%, respectively for aqueous solutions (250 mg L(-1)) at 20 g L(-1) adsorbent dose. The experimental data was analyzed using Freundlich, Langmuir, Dubinin-Redushkevich (D-R) and Temkin isotherm models. It was found that Langmuir, D-R and Temkin models fitted well. The results revealed that the hexavalent chromium is considerably adsorbed on RHC and SDC and it could be an economical method for the removal of hexavalent chromium from aqueous systems. FTIR and SEM of the adsorbents were recorded in native and Cr(VI)-loaded state to explore the number and position of various functional groups available for Cr(VI) binding onto studied adsorbents and changes in adsorbent surface morphology. The surface area of RHC and SDC was 1.12 and 1.16 m(2)g(-1), respectively.
The ability of activated alumina as synthetic adsorbent was investigated for adsorptive removal of Cd(II) and Pb(II) ions from aqueous solutions. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied. The optimum solution pH for adsorption of Cd(II) and Pb(II) from aqueous solutions was found to be 5. Kinetics data were best described by pseudo-second order model. The effective particle diffusion coefficient of Cd(II) and Pb(II) are of the order of 10(-10) m(2)/s. Values of mass transfer coefficient were estimated as 4.868x10(-6) cm/s and 6.85x10(-6) cm/s for Cd(II) and Pb(II) adsorption respectively. The equilibrium adsorption data for Cd(II) and Pb(II) were better fitted to Langmuir adsorption isotherm model. The thermodynamic studies indicated that the adsorption was spontaneous and exothermic for Cd(II) adsorption and endothermic for Pb(II). The sorption energy calculated from Dubinin-Radushkevich isotherm were 11.85 kJ/mol and 11.8 kJ/mol for the adsorption of Cd(II) and Pb(II) respectively which indicated that both the adsorption processes were chemical in nature. Desorption studies were carried out using dilute mineral acids. Application studies carried out using industrial waste water samples containing Cd(II) and Pb(II) showed the suitability of activated alumina in waste water treatment plant operation.
The hexavalent chromium, Cr(VI), biosorption by raw and acid-treated Oedogonium hatei were studied from aqueous solutions. Batch experiments were conducted to determine the biosorption properties of the biomass. The optimum conditions of biosorption were found to be: a biomass dose of 0.8 g/L, contact time of 110 min, pH and temperature 2.0 and 318 K respectively. Both Langmuir and Freundlich isotherm equations could fit the equilibrium data. Under the optimal conditions, the biosorption capacities of the raw and acid-treated algae were 31 and 35.2 mg Cr(VI) per g of dry adsorbent, respectively. Thermodynamic parameters showed that the adsorption of Cr(VI) onto algal biomass was feasible, spontaneous and endothermic under studied conditions. The pseudo-first-order kinetic model adequately describe the kinetic data in comparison to second-order model and the process involving rate-controlling step is much complex involving both boundary layer and intra-particle diffusion processes. The physical and chemical properties of the biosorbent were determined and the nature of biomass-metal ions interactions were evaluated by FTIR analysis, which showed the participation of -COOH, -OH and -NH(2) groups in the biosorption process. Biosorbents could be regenerated using 0.1 M NaOH solution, with up to 75% recovery. Thus, the biomass used in this work proved to be effective materials for the treatment of chromium bearing aqueous solutions.
Thermodynamic parameters and stoichiometries for the binding of anilinonaphthalenesulfonates to beta-cyclodextrin are obtained from steady-state fluorescence intensity and anisotropy measurements. Specifically, formation constant, enthalpy, and entropy values are obtained for complexes of beta-cyclodextrin with eight different substrate molecules at five different temperatures and six different pH values, and their associated errors are given. We propose an explanation of the relative magnitudes of the values obtained with regard to the geometry of the substrate and the importance of the various noncovalent interactions responsible for the complexation.
Iron-chelating therapy with deferoxamine in patients with thalassemia major has dramatically altered the prognosis of this previously fatal disease. The successes achieved with deferoxamine, as well as the limitations of this treatment, have stimulated the design of alternative strategies of iron-chelating therapy, including orally active iron chelators. The development of the most promising of these, deferiprone, has progressed rapidly over the last 5 years; data from several trials have provided direct and supportive evidence for its short-term efficacy. At the same time, the toxicity of this agent mandates a careful evaluation of the balance between risk and benefit of deferiprone in patients with thalassemia, in most of whom long-term deferoxamine is safe and efficacious therapy.
An inexpensive and effective adsorbent was developed from bagasse fly ash, obtained from a sugar industry, for the dynamic uptake of lead and chromium. Lead and chromium are sorbed by the developed adsorbent up to 96-98%. The removal of these two metal ions up to 95-96% was achieved by column experiments at a flow rate of 0.5 mlmin(-1). The adsorption was found to be exothermic in nature. The adsorbent was successfully tried for the removal of lead and chromium from wastewater in our laboratory. The developed system for the removal of two ions is very useful, economic, rapid, and reproducible.
The objective of this study is to assess the uptake of hexavalent chromium (Cr(VI)) from aqueous solutions onto activated carbons (AC) produced from wood. Two activated carbons are tested, a KOH-activated carbon and a commercial H3PO4-activated carbon (Acticarbone CXV). The adsorption of Cr(VI) is maximal at the lowest values of pH (pH 3) and increases with temperature for both adsorbents. The KOH-activated carbon shows higher capacity for adsorption of Cr(VI) than Acticarbone. The sorption isotherms fit the Langmuir model accurately. The adsorption reaction was found to obey a pseudo second-order rate. The activation energy and the pre-exponential factor as well as the thermodynamic functions related to adsorption reaction, DeltaS degrees , DeltaH degrees , DeltaG degrees , were determined. Nevertheless, the global reaction rate is probably controlled by the intra-particular diffusion of Cr(VI) and the mass diffusivity of Cr(VI) was evaluated.
In this study, the adsorption properties of two different marine algae (Ulva fasciata (green algae) and Sargassum sp. (brown algae)) were investigated. Equilibrium isotherms and kinetics were studied to evaluate the relative ability of the two algae to sequester Cu(II) from aqueous solutions. The maximum biosorption capacity obtained was 73.5 mg g(-1) for U. fasciata and 72.5 mg g(-1) for Sargassum sp. at a solution pH of 5.5 +/- 0.5. A significant fraction of the total copper(II) uptake was achieved within 30 min. The copper(II) uptake by the biosorbents was best described by pseudo-second-order rate model.
The biosorption data of Cd(II), Cr(III), and Cr(VI) by saltbush leaves biomass were fit on the Freundlich and Langmuir adsorption isotherms at 297 K. The Cd(II) and Cr(III) solutions were adjusted to pH 5.0 and the Cr(VI) solution was adjusted to pH 2.0. The correlation coefficient values indicated that the data fit better the Freundlich model. The maximal capacities (K(F)) were found to be 5.79 x 10(-2), 3.25 x 10(-2), and 1.14 x 10(-2) mol/g for Cr(III), Cd(II), and Cr(VI), respectively. Similar results were obtained using the Langmuir and the Dubinin-Radushkevick equations. Thermodynamic parameters calculated from the Khan and Singh equation and from the q(e) vs C(e) plot show that the equilibrium constants for the biosorption of the metals follow the same order of the maximal capacities. The negative Gibbs free energy values obtained for Cd(II) and Cr(III) indicated that these ions were biosorbed spontaneously. The mean free energy values calculated from the Dubinin-Radushkevick equation (10.78, 9.45, and 9.05 for Cr(III), Cr(VI), and Cd(II), respectively) suggest that the binding of Cd(II), Cr(III), and Cr(VI) by saltbush leaves biomass occurs through an ionic exchange mechanism.
The adsorption of Al(III) from aqueous solutions onto chitosan was studied in a batch system. The isotherms and the kinetics of adsorption with respect to the initial Al(III) concentration and temperature were investigated. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms. Equilibrium data fitted very well to the Langmuir model in the entire concentration range (5-40 mg/L). The negative values of free energy (DeltaG degrees ) and enthalpy (DeltaH degrees ) for the adsorption of Al(III) onto chitosan indicated that the adsorption process is a spontaneous and exothermic one. Two simplified kinetic models, based on pseudo first-order and pseudo second-order equations, were tested to describe the adsorption mechanism. The pseudo second-order kinetic model resulted in an activation energy of 56.4 kJ/mol. It is suggested that the overall rate of Al(III) ion adsorption is likely to be controlled by the chemical process. The values of the enthalpy (DeltaH(#)) and entropy (DeltaS(#)) of activation were 53.7 kJ/mol and -164.4 J/molK, respectively. The free energy of activation (DeltaG(#)) at 30 degrees C was 103.5 kJ/mol.
Biosorption is the effective method for the removal of heavy metal ions from wastewaters. Results are presented showing the sorption of Pb(II) from solutions by biomass of commonly available, filamentous green algae Spirogyra sp. Batch experiments were conducted to determine the biosorption properties of the biomass and it was observed that the maximum adsorption capacity of Pb(II) ion was around 140mgmetal/g of biomass at pH 5.0 in 100min with 200mg/L of initial concentration. Temperature change in the range 20-40 degrees C affected the adsorption capacity and the nature of the reaction was found to be endothermic in nature. Uptake kinetics follows the pseudo-second-order model and equilibrium is well described by Langmuir isotherm. Isotherms have been used to determine thermodynamic parameters of the process, viz., free energy change, enthalpy change and entropy change. Various properties of the algae, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, thermal analysis by TGA, surface area calculation by BET method, surface morphology with scanning electron microscope images and surface functionality by FTIR. FTIR analysis of algal biomass revealed the presence of amino, carboxyl, hydroxyl and carbonyl groups, which are responsible for biosorption of metal ions. The results indicated that the biomass of Spirogyra sp. is an efficient biosorbent for the removal of Pb(II) from aqueous solutions.
The adsorption of Cr(VI) from aqueous solutions on sawdust (SD), base extracted sawdust (BESD) and tartaric acid modified sawdust (TASD) of Turkish red pine tree (Pinus nigra), a timber industry waste, was studied at varying Cr(VI) concentrations, adsorbent dose, modifier concentration and pH. Batch adsorption studies have been carried out. Sawdust was collected from waste timber industry and modified with various amount of tartaric acid (TA) (0.1-1.5M). The batch sorption kinetics has been tested and the applicability of the Langmuir and Freundlich adsorption isotherms for the present system has been tested at 25+/-2 degrees C. Under observed test conditions, the equilibrium adsorption data fits the linear Freundlich isotherms. An initial pH of 3.0 was most favorable for Cr(VI) removal by all adsorbents. Maximum Cr(VI) was sequestered from the solution within 120 min after the beginning for every experiment. The experimental result inferred that chelation and ion exchange is one of the major adsorption mechanisms for binding metal ions to the SD. Percentage removal of Cr(VI) was maximum at the initial pH of 3.0 (87.7, 70.6 and 55.2% by TASD, BESD, and SD, respectively). Adsorption capacities range from 8.3 to 22.6 mg/g for SD samples.
This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 degrees C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO3 and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater.
Industrial wastewaters containing heavy metals pose a major environmental problem that needs to be remedied. The present study reports the ability of two non-living (dried) fresh water algae, Oedogonium sp. and Nostoc sp. to remove lead(II) from aqueous solutions in batch system under varying range of pH (2.99-7.04), contact time (5-300 min), biosorbent dose (0.1-0.8 g/L), and initial metal ion concentrations (100 and 200mg/L). The optimum conditions for lead biosorption are almost same for the two algal biomass Oedogonium sp. and Nostoc sp. (pH 5.0, contact time 90 and 70 min, biosorbent dose 0.5 g/L and initial Pb(II) concentration 200mg/L) however, the biomass of Oedogonium sp. was found to be more suitable than Nostoc sp. for the development of an efficient biosorbent for the removal of lead(II) from aqueous solutions, as it showed higher values of q(e) adsorption capacity (145.0mg/g for Oedogonium sp. and 93.5mg/g for Nostoc sp.). The equilibrium data fitted well in the Langmuir isotherms than the Freundlich isotherm, thus proving monolayer adsorption of lead on both the algal biomass. Analysis of data shows that the process involves second-order kinetics and thermodynamic treatment of equilibrium data shows endothermic nature of the adsorption process. The spectrum of FTIR confirms that the amino and carboxyl groups on the surface of algal biomass were the main adsorption sites for lead removal. Both the biosorbents could be regenerated using 0.1 mol/L HCl solution, with upto 90% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that both the algal biomass could be used as an efficient biosorbents for the treatment of lead(II) bearing wastewater streams.
Uber dies adsorption in losungen
- H M F Freundlich
Freundlich, H. M. F., (1906). Uber dies adsorption
in losungen, Zeitschriftfue Physikalische Chemie
(Leipzig). A57, 385-470.
Kinetic studies on adsorption of chromium by coconut shell carbons from synthetic effluents
- P S Rao
- R Shashikant
- G S Munjunatha
Rao P. S., Shashikant R. and Munjunatha G. S.,
1992. Kinetic studies on adsorption of chromium
by coconut shell carbons from synthetic effluents.
Application of Citric Acid Modified Annona squamosa (Custard Apple) Bark Powder as Bio sorbent to Remove Ni (II) From Waste Water
- N Seshadri
- B Ramesh Naik
- N V Kumar
- D K Venkata Ramana
- K Seshaiah
Seshadri N., B. Ramesh Naik, N. V. Sandeep
Kumar, D. K. Venkata Ramana, K. Seshaiah
(2014) Application of Citric Acid Modified
Annona squamosa (Custard Apple) Bark Powder
as Bio sorbent to Remove Ni (II) From Waste
Water. Indian Journal of Advances in Chemical
Science, vol. 3, pp. 1-10.