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Removal of lead (II) ions from Aqueous Solution using Eggplant Peels Activated Charcoal,
Abstract
Abstract
The eggplant peel activated charcoal (EPPAC) was investigated as an adsorbent for the removal of lead II ions from aqueous solution. Three methods were tested for the production of eggplant peel activated charcoal (EPPAC) from eggplant peel charcoal (EPPC), yielding three different products; EPPAC-1, EPPAC-2, and EPPAC-3. The difference among the three methods lies in the primary physical mixing of the EPPC with the activating agent (potassium hydroxide) before heating the mixture in a furnace for activation. The removal efficiency of lead II ions by the three adsorbents was 57.7%, 70.0%, and 60.0% for EPPAC-1, EPPAC-2, and EPPPAC-3, respectively. The optimized activation parameters for EPPAC-2 were: activation time 2 hours, activation temperature 700°C, and activation ratio 1:2 (EPPAC: KOH). Scanning electron microscopy (SEM) revealed that EPPAC-2 has the most porous structure. The surface area of EPPAC-2 was measured to be 739 m2/g. Adsorption kinetics of lead (II) is best described by the pseudo-second-order kinetic model with second order rate constant of 1.70 × 10−3 g/mg.h at room temperature. The adsorption of lead on EPPAC-2 is found to follow the Langmuir isotherm with a maximum adsorption capacity of 1.4 × 102 mg/g.
... Therefore, in the perspective of sustainable development, the identification of a possible alternative use of these food waste is important. Recent studies have shown that banana peel [27], apple peel [28], eggplant peel [29], potato peel [30], orange peel [31], lemon peel [32,33], watermelon peel [34,35], tomato peel [36], coffee waste [11,15,37,38] decaf coffee waste, carob peel and grape waste [39,40] are efficient adsorbents for the removal of heavy metals and toxic elements from wastewater. However, the removal efficiency of food waste materials has been assessed by performing adsorption experiments in heterogeneous operating conditions. ...
... The aim of this study is to evaluate the adsorption capacities of 12 food waste materials (potato peel, lemon peel, orange peel, watermelon peel, tomato peel, coffee waste, apple peel, banana peel, decaf coffee waste, eggplant peel, carob peel and grape waste), comparing their efficiency for the removal of 23 elements (for the most of whom the adsorption capacities have never been assessed) from multi-element solutions (at pH 2.0 and pH 5.5), in homogeneous experimental conditions. The use of multi-element solutions does not allow the identification of the adsorption isotherms of the single elements and the determination of the interaction mechanism for the adsorption, which in part have already been defined in previous studies [11,15,[27][28][29][30][31][32][33][34][35][36][37][38][39][40]. In fact, the competitiveness between the metals for the adsorbents' active sites precludes obtaining the optimum removal values of the single elements. ...
... Banana peel, watermelon peel and grape waste resulted the most efficient adsorbents for the removal of most of the metals and metalloids from multi-element solutions at pH 2.0 as well as at pH 5.5. Elements' removal efficiency varies depending on the amount of adsorbent exposed in solution, as expected from the adsorption isotherms defined in previous studies [11,15,[27][28][29][30][31][32][33][34][35][36][37][38][39][40]. ...
Recent studies have shown the potential of food waste materials as low cost adsorbents
for the removal of heavy metals and toxic elements from wastewater. However, the adsorption
experiments have been performed in heterogeneous conditions, consequently it is difficult to compare
the efficiency of the individual adsorbents. In this study, the adsorption capacities of 12 food waste
materials were evaluated by comparing the adsorbents’ efficiency for the removal of 23 elements from
complex multi-element solutions, maintaining homogeneous experimental conditions. The examined
materials resulted to be extremely efficient for the adsorption of many elements from synthetic
multi-element solutions as well as from a heavy metal wastewater. The 12 adsorbent surfaces were
analyzed by Fourier transform infrared spectroscopy and showed different types and amounts
of functional groups, which demonstrated to act as adsorption active sites for various elements.
By multivariate statistical computations of the obtained data, the 12 food waste materials were
grouped in five clusters characterized by different elements’ removal efficiency which resulted to be
in correlation with the specific adsorbents’ chemical structures. Banana peel, watermelon peel and
grape waste resulted the least selective and the most efficient food waste materials for the removal of
most of the elements.
... The factors that were used to produce the 3 activated charcoals, such as temperature and time were utilized in a new process. Gulistan et al. [23] observed that the efficiency of taking out the oil from the samples of created water (SPW) that is supplying a less-price adsorbent eggplant peel powder (EPP). Factors that were used to study the exclusion effectiveness are pH, time, and temperature. ...
... It was reported [21][22][23][24] that the Boyd equation can be applied to determine the rate-controlling step for an adsorbent and expressed as [38,39]: ...
The removal of oil from domestic wastewater was achieved by implementing eggplant peels (EPP) powder as an efficient bio-adsorbent material. The batch adsorption process was adopted to reach the acceptable range that allowed in Iraqi standardizations, which should not exceed (10 mg L-1). The characterization of EPP was conducted with X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared (FT-IF) spectroscopy, and Brunauer-Emmett-Teller (BET). Two variables were taken into consideration, including time and temperature. It was noticed that these two variables had an essential impact in decreasing oil concentration in domestic wastewater. The temperature has an excellent effect comparing with time in decreasing the oil concentration from domestic wastewater; as both time and temperature increased, the oil concentration decreased. Results manifested that the adsorption method was effective in decreasing the oil concentration. Also, the results elucidated that the adsorption isotherms can be reasonably befitting via the Langmuir model due to the chemisorption that occurs on the surface between bio-adsorbent and pollutant with a determination coefficient of (0.8376). The adsorption kinetics of the oily west water upon the adsorbate was vigorously denoted via a pseudo-first-order kinetic model. The thermodynamic variables were assessed for determining free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°).
... As the temperature was increased to 500 o C, activation process was able to create pore structure within the carbon, indicating higher surface area. It seems that the pores and cavities on the surfaces of carbons resulted from the evaporation of the activating agent in this case is phosphoric acid during carbonization, leaving the space previously occupied by the activating agent [29,38]. Therefore, the H3PO4 is an effective activating agent to obtain activated carbon having high surface area. ...
In this study, activated carbons were produced from pumpkin seed shell by chemical activation. In chemical activation, H3PO4 was used as chemical agent. The effects of impregnation ratio (IR) and activation temperature were investigated. Activation temperatures and impregnation ratios were selected in the range of 400–600 °C and 1–3, respectively. The surface area, pore volumes, pore size distribution and average pore diameter of the activated carbons were characterized by N2 adsorption at 77 K using the BET, t-plot and DFT methods. The highest BET surface area and total pore volume of the activated carbon was obtained as 1421 m2/g and 0.908 cm3/g at 500 °C activation temperature and at an impregnation ratio of 2, respectively. The morphology and functional groups present were investigated by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. The experimental results show that the activation temperature and the impregnation ratio have a significant effect on the pore structure of the activated carbon and pumpkin seed shell seemed to be an alternative precursor for the commercial activated carbon productions.
Agricultural waste peels have been recognized as an ecological burden for the society. However, waste peels, as lignocellulosic biomass-rich materials, have stimulated new gateways for the production of renewable, low cost and sustainable adsorbents for water treatment applications. This review compiles the work conducted by various researchers over the last few decades on the use of various agricultural waste peels as adsorbents for the water and wastewater treatment. In this review, adsorption capacities for organic and inorganic pollutants by different peel-based adsorbents are summarized. Wherever applicable, different modification methods, which have been employed to develop modified peel-based adsorbents, have also been presented to highlight and discuss the key advancements on the preparation of novel adsorbents using agricultural waste peels. Adsorption mechanisms responsible for pollutants removal by peel-based adsorbents have also been discussed. Finally, conclusions have been drawn from the literature reviewed. The paper also discusses the future research needs in the area of biosorbent development utilizing agricultural waste peels for application in water treatment.
In this research, the results of the SEM morphology and XRD pattern studies of charcoals and activated charcoals prepared from banana peel are used to describe the effects of pyrolysis temperature and the mass ratios of KOH. In the carbonization process, banana peel charcoal carbonized at 300 o C to 400 o C has incomplete carbonization and the cell structure is maintained. Complete pore evolution occurred at temperatures of 500 o C. The surface image of activated carbon from banana peel charcoal obtained at a pyrolysis temperature between 500 o C and 700 o C and with mass ratios between 1:2 and 1:5 showed increased porosity with increasing temperature. Increase KOH ratios slightly raised the pore size and porosity of activated charcoals. The change of pyrolysis temperature from 500 o C to700 o C for ratios ranging between 1:2 and 1:4 has a big effect on the pore size. However, the 1:5 ratio of activated charcoal suppressed the pore size. This result showed that the over KOH ratio resulted in an insulating layer, covering the particles of banana peel charcoal. The XRD pattern showed that the constituents of banana peel activated charcoal were probably graphite, amorphous C, amorphous SiO 2 , K 2 O, K and K 2 CO 3 . Background Organic matter may be converted by controlled thermal decomposition into carbon. The mechanisms involved in the conversion of organic matter to carbon are: (1) desorption of adsorbed water up to 150 o C, (2) splitting of matter structure water between 150 o C and 260 o C, (3) chain scissions, or depolymerization, and breaking of C-O and C-C bonds within ring units evolving water, CO and CO 2 between 260 o C and 400 o C, (4) aromatization forming graphitic layers above 400 o C, and (5) above 800 o C, the thermal induced decomposition and the rearrangement reaction are almost terminated leaving a carbon template structure. The major components of organic matter break down in a stepwise manner at 200-800 o C (hemicellulose), 260-350 o C (cellulose) and 280-500 o C (lignin). Between 260 o C and 400 o C almost 80% of the total weight loss occurs which may vary between 40% (lignin) to about 80% (cellulose) due to evolution of H 2 O, CO 2 , and volatile hydrocarbon species from fragmentation reactions of the polyaromatic constituents [1]. Chemical activation of carbons is a very common method for obtaining activated carbons with very high surface areas. KOH is one of the most effective agents employed for organic materials. KOH might be more selective in the activation process, causing a more localized reaction with the carbon precursor and is more effective for the highly ordered materials [2]. Thus, it can be stated that direct KOH activation of a lignocellulosic material is not necessarily an advantage [2]. The temperatures of pyrolysis and activation are considered to be the most important parameters controlling the activated carbon production. There are many precursors from which activated carbons can be obtained. The use of organic materials for activated carbon is common. These materials are obtained as by-products of the agricultural and food industries and, hence, they are cheap and their use contributes to the conservation of the environment [3]. Banana peels are a solid waste from finished food products, such as chips, slices, and dried banana. They are high organic carbon (41.37%). This waste has been subjected to biomethanation [4] and biogas production [5]. The banana peel charcoals have been prepared by carbonization at 300-700 o C. It was found that the percentage of charcoal from banana peel was decreased with the increase of carbonization temperature. However, the percentage of fixed carbons was reversed. The maximum of iodine numbers of charcoal from banana peels were found to be at the carbonized temperature of 500 o C. The charcoals of banana peels with carbonization at 500 o C were activated with KOH in ratios of 1:2 to 1:5 by weight. Then, these activated charcoals were recarbonized at 600 o to 900 o C. The iodine number of activated charcoals increased with increasing ratios of KOH, but the ethylene blue absorptions were increased a little [6]. These results suggest that activated carbons prepared from banana peel using KOH activation may be developed for adsorbents. In this study, the results of the SEM morphology and XRD pattern studies of charcoals and activated charcoals prepared from banana peel are used to describe the effects of pyrolysis temperature and the mass ratios of KOH.
An attempt was made to assess the biosorption potential of rose waste biomass for the removal of Pb(II) and Co(II) ions from synthetic effluents. Biosorption of heavy metal ions (>90%) reached equilibrium in 30 min. Maximum removal of Pb(II) and Co(II) occurred at pH 5 and 6 respectively. The biosorbent dose for efficient uptake of Pb(II) and Co(II) was 0.5 g/L for both metals. The biosorbent size affected the Pb(II) and Co(II) biosorption rate and capacity. Rose waste biomass was found effective for Pb(II) and Co(II) removal from synthetic effluents in the concentration range 10–640 mg/L. Equilibrium sorption studies showed that the extent of Pb(II) and Co(II) uptake by the rose waste biomass was better described by the Langmuir isotherm in comparison to the Freundlich model. The uptake capacities of the two metal ions were 156 and 27.15 mg/g for Pb(II) and Co(II) respectively.
The biosorption of Cu(II) onto chestnut shell, a residue of the food processing industry, in a batch adsorber has been studied. Equilibrium isotherms, kinetic data, and thermodynamic parameters have been evaluated. Equilibrium data agreed well with Langmuir isotherm and Redlich–Peterson isotherm models. The adsorption capacity of chestnut shell for Cu(II) was determined with the Langmuir model and was found to be 12.56 mg g−1 at 293 K. The kinetic data were found to follow the pseudo-second-order model. Intra-particle diffusion is not the sole rate-controlling factor. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. Chestnut shell was shown to be a promising biosorbent for Cu(II) removal from aqueous solutions.
Melocanna baccifera (Poaceae) is the most abundant and economically important non-timber product in state of Mizoram, India. The communities of the region use this potential resource in many ways, charcoal production is one of them. Bamboo charcoal has application in food, pharmaceutical and chemical industries. Activated charcoal was prepared from M. baccifera charcoal by chemical pretreatment in order to make better use of this abundant biomass material. Batch experiments were conducted under varying range of pH (2.0-6.0), contact time (15-360 min) and metal ion concentrations (50-90 mg L(-1)). The optimum conditions for lead biosorption are almost same for M. baccifera raw charcoal (MBRC) and M. baccifera activated charcoal (MBAC)-pH 5.0, contact time 120 min, adsorption capacity q(max) 10.66 mg g(-1) and 53.76 mg g(-1), respectively. However, the biomass of MBAC was found to be more suitable than MBRC for the development of an efficient adsorbent for the removal of lead(II) from aqueous solutions. FTIR analysis revealed that -OH, C-H bending, C=O stretching vibration and carbonyl functional groups were mainly responsible for Pb(II) biosorption. Thus, this study demonstrated that both the charcoal biomass could be used as adsorbents for the treatment of Pb(II) from aqueous solution.
Discharge of heavy metals from metal processing industries is known to have adverse effects on the environment. Conventional treatment technologies for removal of heavy metals from aqueous solution are not economical and generate huge quantity of toxic chemical sludge. Biosorption of heavy metals by metabolically inactive non-living biomass of microbial or plant origin is an innovative and alternative technology for removal of these pollutants from aqueous solution. Due to unique chemical composition biomass sequesters metal ions by forming metal complexes from solution and obviates the necessity to maintain special growth-supporting conditions. Biomass of Aspergillus niger, Penicillium chrysogenum, Rhizopus nigricans, Ascophyllum nodosum, Sargassum natans, Chlorella fusca, Oscillatoria anguistissima, Bacillus firmus and Streptomyces sp. have highest metal adsorption capacities ranging from 5 to 641 mg g(-1) mainly for Pb, Zn, Cd, Cr, Cu and Ni. Biomass generated as a by-product of fermentative processes offers great potential for adopting an economical metal-recovery system. The purpose of this paper is to review the available information on various attributes of utilization of microbial and plant derived biomass and explores the possibility of exploiting them for heavy metal remediation.
The adsorption of Pb(II) and Cd(II) metal ions on mustard husk has been found to be concentration, pH, contact time, adsorbent dose and temperature dependent. The adsorption parameters were determined using Langmuir and Freundlich isotherm models. The adsorption isotherm studies clearly indicated that the adsorptive behavior of Pb(II) and Cd(II) metal ions on mustard husk satisfies not only the Langmuir assumptions but also the Freundlich assumptions, i.e. multilayer formation on the surface of the adsorbent with an exponential distribution of site energy. Ion exchange and surface complexation are the major adsorption mechanisms involved. The applicability of Lagergren kinetic model has also been investigated. Thermodynamic constant (k(ad)), free energy change (DeltaG), enthalpy change (DeltaH) and entropy change (DeltaS) were calculated for predicting the nature of adsorption. The results indicate the potential application of this method for effluent treatment in industries and also provide strong evidence to support the adsorption mechanism proposed.
Ionic liquids are expected to replace conventional organic solvents in organic synthesis, solvent extraction and electrochemistry due to their unique characters such as low volatility, high stability and so on. In this work, N,N,-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethansulfonyl) imide was used as an alternative solvent to extract heavy metal ions. As the extracting conditions, the additional effect of 8-hydroxyquinoline (8-HQ) as metal chelating agent into ionic liquids, shaking time and volume ratio were investigated. As extraction efficiency depended on 8-HQ concentration significantly, in order to extract high concentrated metal ions the solubility of 8-HQ into ionic liquid was tested. N,N,-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethansulfonyl)imide had good solubility of 8-HQ. Consequently, 5 μmol of copper, zinc, cadmium and manganese could be completely recovered with 100 μl ionic liquid.
A comparison of the linear least-squares method and a trial-and-error non-linear method of three widely used isotherms (the Langmuir, Freundlich, and Redlich-Peterson) were examined in an experiment using lead ion sorp-tion onto peat at different temperatures. The four Langmuir linear equations are discussed. Langmuir isotherm pa-rameters obtained from the four Langmuir linear equations using the linear method differed but they were the same when using the non-linear method. Langmuir-1 is the most popular linear form, and it had the highest coefficient of determination compared with the other Langmuir linear equations. The Redlich-Peterson and Langmuir isotherms produced higher coefficients of determination. There are two separate regions depicting the Freundlich isotherm. The results show that that non-linear method may be a better way to obtain the parameters.
Activated carbons were prepared from biomass of Algerian date pits for developing efficient and cheap adsorbents in the aim to remove heavy metals from waste water. Carbon adsorbents were obtained following two successive treatments: pyrolysis under dry nitrogen flow and physical activation under wet nitrogen flow. Pyrolysis process was optimized by varying some operating parameters such as temperature, nitrogen flow, heating rate and pyrolysis hold time in order to determine their effects on the porous structure development of date pits activated carbon. Chars obtained from pyrolysis process were activated with the same operating conditions (activation temperature of 700 °C, 50% nitrogen + 50% water flow rate of 150 cm3/min and heating rate of 10 °C/min) except for the activation hold time which varied from 0.5 to 4 h. Experimental results showed that pyrolysis conditions have significant effects on the chars and activated carbons properties prepared from date pits. The best microporous activated carbon (surface area of 464 m2/g, microporous volume of 0.203 cm3/g and total pore volume of 0.220 cm3/g) was obtained by pyrolysis at 10 °C/min up to 700 °C for 1 h under 150 cm3/min of nitrogen. Activation hold time has also an impact on activated carbons porosity. The best surface area, microporous volume and total pore volume were obtained after activation for 4 h: 1467 m2/g, 0.711 cm3/g and 0.725 cm3/g respectively. The best adsorbents prepared from date pits were then tested for the removal of Fe3+ and Cu2+ from aqueous solutions. Results show that these adsorbents have higher metallic cation adsorption capacities than usual commercial activated carbons because of the presence of both carboxylic and phenolic groups at the surface witch improves the cation-exchange and complexation properties of these adsorbents in addition of the greater specific surface area. Adsorption data were analyzed with Langmuir and Freundlich isotherms. The better fit is obtained with the Langmuir model.
The effects of different activation conditions, including KOH/CNTs ratio, activation temperature, activation time, and nitrogen flow rate, on the specific surface area of activated carbon nanotubes (CNTs) prepared with KOH were investigated. The nanometer hollow tube structure of CNTs can be well preserved for the activated CNTs but their BET specific surface area is significantly enlarged. The best results of activated CNTs with larger BET specific surface areas can be achieved by optimizing the four factors amongst which the KOH/CNTs ratio is found to be dominant.
Pine bark was able to sorb cadmium, copper, and nickel ions from aqueous solutions. Binary equilibrium data from the combination of these metals were collected in this work using this sorbent. These data were modeled using three types of binary component equilibrium isotherms, all of which resulted in good fitting of the experimental data, with the Langmuir—Freundlich model resulting in their best representa- tion. In general, the capacity of bark for each metal in the binary system was lower than in the single metal systems. The study also examined the mechanisms of metal biosorption by bark. Scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) microanalyses revealed that metal ions were sorbed mainly at the cell wall of the bark and only a small amount of ions diffused into the cytoplasm. Both the EDX analysis and the atomic absorption spectrophotometry (AAS) measurements showed that ion exchange was an important mechanism in this sorption process. Electron spin resonance (ESR) tests demonstrated that free radicals from the sorbent also have a significant role in the sorption processes.
Samples of activated carbons of different origins were tested as removers of hydrogen sulfide at room temperature. The breakthrough capacity was evaluated using a lab designed test. The surface properties of the carbons were studied using Boehm titration, nitrogen sorption and thermal analysis. The results obtained indicate that the choice of unimpregnated carbon for hydrogen sulfide removal should be based on the parameters describing surface acidity such as pH, number of acidic groups, or weight loss during thermal treatment associated with the presence of acidic functional groups. There are certain threshold ranges of these quantities which, when exceeded, have a dramatic effect on the H2S breakthrough capacity.
Distinctive adsorption equilibria and kinetic models are of extensive use in explaining the biosorption of heavy metals, denoting the need to highlight and summarize their essential issues, which is the main purpose of this paper. As a general trend, up until now, most studies on the biosorption of heavy metal ions by miscellaneous biosorbent types have been directed toward the uptake of single metal in preference to multicomponent systems. In particular, Langmuir and Freundlich models are the most common isotherms for correlating biosorption experimental data though other isotherms, which were initially established for gas phase applications, can also be extended onto biosorption system. In kinetic modeling, the pseudo-first and -second order equations are considered as the most celebrated models.
The sorption of three divalent metal ions — copper, nickel and lead — from aqueous solution onto peat in single component
systems has been studied and the equilibrium isotherms determined. The experimental data have been analysed using the Langmuir,
Freundlich, Redlich-Peterson, Toth, Temkin, Dubinin-Radushkevich and Sips isotherm models. In order to determine the best
fit isotherm for each system, six error analysis methods were used to evaluate the data: the coefficient of determination,
the sum of the errors squared, a hybrid error function, Marquardt's percent standard deviation, the average relative error
and the sum of absolute errors. The error values demonstrated that the Sips equation provided the best model for the three
sets of experimental data overall.
Multiple steps in the Boehm titration are carried out in a variety of manners by different research groups, thereby making results difficult to compare. The methods standardized in this paper include method of agitation, use of dilute titrant, carbon removal from reaction bases and the effect of air on NaOH standardization; uncertainty estimations are also shown. By examining the multiple agitation methods, it was found shaking was the optimal method for use in the Boehm titration as other methods (stirring and sonicating) affect the carbon surface. It was also found that filtering the carbon and reaction base mixture did not affect the titration, nor did the use of dilute titrant. Solutions must be freshly standardized prior to use since storage (even over a one week time period) results in a change in concentration.
The kinetics and thermodynamics of copper(II) and lead(II) biosorption onto Aspergillus niger pretreated with NaOH were studied with respect to pH, temperature and initial metal ion concentration. The optimum pH values were determined as 5.0 and 4.0 for copper(II) and lead(II) at 25 °C, respectively. Biosorption capacity values of the biomass increased with increasing initial metal ion concentration and temperature. The maximum biosorption capacities were obtained as 28.7 and 32.6 mg g−1 at 250 mg dm−3 initial copper(II) and lead(II) concentration at 35 °C, respectively. The equilibrium data were analyzed using Freundlich, Langmuir and Redlich–Peterson adsorption models. The model parameters were estimated by the non-linear regression analysis. It was seen that equilibrium data fitted very well to the Langmuir adsorption model at all temperatures studied. The applicability of the saturation type kinetic model for metal–A. niger system was tested at different temperature in the range of 20–35 °C. The activation energies of the biosorption were determined as 27.48 and 36.76 kJ mol−1 for Cu(II) and Pb(II)–A. niger systems, respectively. Using the thermodynamic equilibrium coefficients obtained at different temperature, the Gibbs free energy changes (−18.97 kJ mol−1 for Cu(II) and −22.97 kJ mol−1 for Pb(II) (at 35 °C)), enthalpy changes (28.9 kJ mol−1 for Cu(II) and 38.3 kJ mol−1 for Pb(II)) and entropy changes (0.168 kJ mol−1 K−1 for Cu(II) and 0.186 kJ mol−1 K−1 for Pb(II)) of biosorption were also determined. The results showed that biosorption of copper(II) and lead(II) on A. niger was endothermic and spontaneous.
The removal of Cu(II) by adsorption on fly ash has been found to be concentration, pH and temperature dependent. The kinetics of adsorption indicates the process to be diffusion controlled. The Langmuir constants have been calculated at different temperatures, and the adsorption has been found to be endothermic (ΔH = 15.652 kcal mol−1). The maximum removal is observed at pH 8.0, and variation in adsorption with pH has been explained on the basis of surface ionisation and complexation.
The adsorption of Cu(II) ions onto chitosan and cross-linked chitosan beads has been investigated. Chitosan beads were cross-linked with glutaraldehyde (GLA), epichlorohydrin (ECH) and ethylene glycol diglycidyl ether (EGDE) in order to obtain sorbents that are insoluble in aqueous acidic and basic solution. Batch adsorption experiments were carried out as a function of pH, agitation period, agitation rate and concentration of Cu(II) ions. A pH of 6.0 was found to be a optimum for Cu(II) adsorption on chitosan and cross-linked chitosan beads. Isotherm studies indicate Cu(II) can be effectively removed by chitosan and cross-linked chitosan beads. Adsorption isothermal data could be well interpreted by the Langmuir equation. Langmuir constants have been determined for chitosan and cross-linked chitosan beads. The experimental data of the adsorption equilibrium from Cu(II) solution correlated well with the Langmuir isotherm equation. The uptakes of Cu(II) ions on chitosan beads were 80.71 mg Cu(II)/g chitosan, on chitosan-GLA beads were 59.67 mg Cu(II)/g chitosan-GLA, on chitosan-ECH beads were 62.47 mg Cu(II)/g chitosan-ECH and on chitosan-EGDE beads were 45.94 mg Cu(II)/g chitosan-EGDE. The Cu(II) ions can be removed from the chitosan and cross-linked chitosan beads rapidly by treatment with an aqueous EDTA solution and at the same time the chitosan and cross-linked chitosan beads can be regenerated and also can be used again to adsorb heavy metal ions.
Adsorption of copper and lead ions onto tea waste from aqueous solutions was studied to enable comparison with alternative commonly available absorbents. Batch experiments were conducted to determine the factors affecting adsorption and kinetics of the process. Fixed bed column experiments were performed to study practical applicability and breakthrough curves were obtained. Tea waste is capable of binding appreciable amounts of Pb and Cu from aqueous solutions. The adsorption capacity was highest at solution pH range 5–6. The adsorbent to solution ratio and the metal ion concentration in the solution affect the degree of metal ion removal. The equilibrium data were satisfactorily fitted to Langmuir and Freundlich isotherms. Highest metal uptake of 48 and 65 mg/g were observed for Cu and Pb, respectively. Pb showed higher affinity and adsorption rate compared to Cu under all the experimental conditions. Kinetic studies revealed that Pb and Cu uptake was fast with 90% or more of the adsorption occurring within first 15–20 min of contact time. The kinetic data fits to pseudo second order model with correlation coefficients greater than 0.999. Increase in the total adsorption capacity was observed when both Cu and Pb ions are present in the solution. Higher adsorption rate and the capacity were observed for smaller adsorbent particles. Tea waste is a better adsorbent compared to number of alternative low cost adsorbents reported in literature.
Heavy metal pollution has become one of the most serious environmental problems today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. In recent years, various methods for heavy metal removal from wastewater have been extensively studied. This paper reviews the current methods that have been used to treat heavy metal wastewater and evaluates these techniques. These technologies include chemical precipitation, ion-exchange, adsorption, membrane filtration, coagulation-flocculation, flotation and electrochemical methods. About 185 published studies (1988-2010) are reviewed in this paper. It is evident from the literature survey articles that ion-exchange, adsorption and membrane filtration are the most frequently studied for the treatment of heavy metal wastewater.
Grape waste generated in wine production is a cellulosic material rich in polyphenolic compounds which exhibits a high affinity for heavy metal ions. An adsorption gel was prepared from grape waste by cross-linking with concentrated sulfuric acid. It was characterized and utilized for the removal of Cr(VI) from synthetic aqueous solution. Adsorption tests were conducted in batch mode to study the effects of pH, contact time and adsorption isotherm of Cr(VI), which followed the Langmuir type adsorption and exhibited a maximum loading capacity of 1.91 mol/kg at pH 4. The adsorption of different metal ions like Cr(VI), Cr(III), Fe(III), Zn(II), Cd(II) and Pb(II) from aqueous solution at different pH values 1-5 has also been investigated. The cross-linked grape waste gel was found to selectively adsorb Cr(VI) over other metal ions tested. The results suggest that cross-linked grape waste gel has high possibility to be used as effective adsorbent for Cr(VI) removal.
Animal bone is able to adsorb copper and nickel ions from their single aqueous solutions. It was noted that a decrease in the sorbent concentration with constant copper or nickel concentration, or an increase in the copper or nickel concentration with a constant sorbent concentration resulted in a higher metal loading per unit weight of the sorbent. Increase in the initial pH of the metal solution resulted in an increase in the metals uptake per unit weight of the sorbent. Freundlich isotherm model was found to be applicable for the experimental data of Cu2+ and Ni2+. The results showed that animals bones can be used for the adsorption of the Cu2+ and Ni2+ with higher affinity toward Cu2+ ions. The new sorbent was able to decrease copper concentration to a limit lower than the limit permitted by the environmental regulations.
Biosorption of heavy metals was carried out using whole mycelia and selected components of Aspergillus niger, Rhizopus oryzae and Mucor rouxii. Binding of copper, cadmium, nickel and zinc was considerably improved by treating the cell wall fraction with 4 M NaOH at 121 degrees C. Chitosan contributed most to the biosorptive capacity. 0.96 mmol copper was bound by 1 g of the treated mycelium of M. rouxii DSM 1191.
The effect of activation temperature on the textural and chemical properties of activated carbons prepared from pistachio-nut shells by potassium hydroxide activation was studied. Relatively high activation temperature was required to develop high porosities. However, too high an activation temperature resulted in the burn-off of the carbon structures and the widening of micropores to meso- and macropores. The microstructures and microcrystallinities of the carbons prepared were examined using a scanning electron microscope and a powder X-ray diffraction analyzer, respectively, while the Fourier transform infrared spectra indicated the changes in the surface functional groups that were formed during the different preparation stages.
In this article, the technical feasibility of various low-cost adsorbents for heavy metal removal from contaminated water has been reviewed. Instead of using commercial activated carbon, researchers have worked on inexpensive materials, such as chitosan, zeolites, and other adsorbents, which have high adsorption capacity and are locally available. The results of their removal performance are compared to that of activated carbon and are presented in this study. It is evident from our literature survey of about 100 papers that low-cost adsorbents have demonstrated outstanding removal capabilities for certain metal ions as compared to activated carbon. Adsorbents that stand out for high adsorption capacities are chitosan (815, 273, 250 mg/g of Hg(2+), Cr(6+), and Cd(2+), respectively), zeolites (175 and 137 mg/g of Pb(2+) and Cd(2+), respectively), waste slurry (1030, 560, 540 mg/g of Pb(2+), Hg(2+), and Cr(6+), respectively), and lignin (1865 mg/g of Pb(2+)). These adsorbents are suitable for inorganic effluent treatment containing the metal ions mentioned previously. It is important to note that the adsorption capacities of the adsorbents presented in this paper vary, depending on the characteristics of the individual adsorbent, the extent of chemical modifications, and the concentration of adsorbate.
The main factors that affect the large specific surface area (SSA) of the activated carbon from agricultural waste corn cobs were studied by chemically activated method with solution of KOH and soap which acted as surfactant. The experiment showed that not only the activation temperature, activation time and the mass ratio of KOH to the carbonized material, but also the activated methods using activator obviously influenced the SSA of activated carbon. The experimental operating conditions were as follows: the carbonized temperature being 450 degrees C and keeping time being 4 h using N2 as protective gas; the activation temperature being 850 degrees C and holding time being 1.2 h; the mass ratio of KOH to carbonized material being 4.0; the time of soaking carbonized material in the solution of KOH and soap being 30 min. Under the optimal conditions, the SSA of activated carbon from corn cobs reached 2700 m2/g. And the addition of the soap as surfactant may shorten the soaking time. The structure of the activated carbon prepared had narrow distribution of pore size and the micro-pores accounted for 78%. The advantages of the method described were easy and feasible.
Toxic heavy metals in air, soil and water are global problems that are growing threat to the environment. Therefore, the removal and separation of toxic and environmentally relevant heavy metal ions are a technological challenge with respect to industrial and environmental application. A promising process for the removal of heavy metal ions from aqueous solutions involves bonding the metals to a bonding agent (such as macromolecular species), and then separating the loaded agents from wastewater by separation processes such as membrane filtration. The choice of water-soluble macroligands remains important for developing this technology. The effects of type of complexing agent, pH value and applied pressure on retention coefficients of Zn(II) and Cd(II) complexes were investigated. At best operating conditions (pH=9.0, p=300kPa) using diethylaminoethyl cellulose, the removal of Cd(2+) and Zn(2+) was more than 95% and 99%, respectively.
The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. The results of the kinetic studies showed that the uptake processes of the two metal ions(Cd(lII) and Pb(ll)) followed the pseudo-second-order rate expression. The equilibrium data fitted very well to both the Langmuir and Freundlich adsorption models. The FT-IR analysis showed that the main mechanism of Cd(ll) and Pb(II) biosorption onto dried activated sludge was their binding with amide I group.
The use of low-cost adsorbents was investigated as a replacement for current costly methods of removing metals from aqueous solution. Removal of copper (II) from aqueous solution by different adsorbents such as shells of lentil (LS), wheat (WS), and rice (RS) was investigated. The equilibrium adsorption level was determined as a function of the solution pH, temperature, contact time, initial adsorbate concentration and adsorbent doses. Adsorption isotherms of Cu (II) on adsorbents were determined and correlated with common isotherm equations such as Langmuir and Freundlich models. The maximum adsorption capacities for Cu (II) on LS, WS and RS adsorbents at 293, 313 and 333 K temperature were found to be 8.977, 9.510, and 9.588; 7.391, 16.077, and 17.422; 1.854, 2.314, and 2.954 mg g(-1), respectively. The thermodynamic parameters such as free energy (delta G0), enthalpy (delta H0) and entropy changes (delta S0) for the adsorption of Cu (II) were computed to predict the nature of adsorption process. The kinetics and the factors controlling the adsorption process were also studied. Locally available adsorbents were found to be low-cost and promising for the removal of Cu (II) from aqueous solution.
The waste distillery sludge from sugar-cane industry was pretreated physically (boiled, heated and autoclaved) as well as chemically (HCl, H(2)SO(4), H(3)PO(4), NaOH, Ca(OH)(2), Al(OH)(3), C(6)H(6), HCHO, CH(3)OH and C1(2)H(25)OSO(3)Na (sodium dodecyl sulphate (SDS)) for assessing the comparative sorption capacity of untreated and modified distillery sludge for Pb(II) biosorption from aqueous solutions. Experiments were conducted in shake flasks on a batch basis to access the effect of different experimental parameters such as pH, biosorbent dosage, biosorbent size, initial Pb(II) concentration and contact time. The uptake capacity 'q' (mg/g) of untreated and pretreated distillery sludge was in following order: NaOH (51.29+/-1.21)>HCl (49.82+/-1.22)>HCHO (49.56+/-1.14)>H(2)SO(4) (47.71+/-1.20)>HgCl(2) (45.32+/-1.06)>Ca(OH)(2) (44.01+/-1.18)>MeOH (43.73+/-1.23)>C(6)H(6) (42.72+/-1.19)>H(3)PO(4) (42.01+/-1.17)>SDS (40.87+/-1.27)>autoclaved (40.23+/-1.24)>Boiled (39.95+/-1.19)>heated (38.87+/-1.32)>Al (OH)(3) (38.30+/-1.14)>untreated (37.76+/-1.21). In further parameter studies, the optimized biosorbent size was 0.250 mm at pH 5 and best dose was 0.05 g of biosorbent. The applicability of the Langmuir and Freundlich models for sorption process was tested and best fitted model was Langmuir with the coefficient of determination (R(2)) value, 0.97, the process followed second order kinetic mechanism.
This study investigated the adsorption of the heavy metal ions Pb(II), Cu(II), Cd(II), Zn(II), and Ni(II) on a lignin isolated from black liquor, a waste product of the paper industry. Lignin has affinity with metal ions in the following order: Pb(II)>Cu(II)>Cd(II)>Zn(II)>Ni(II). The adsorption kinetic data can be described well with a pseudosecond-order model and the equilibrium data can be fitted well to the Langmuir isotherm. Metal ion adsorption was strongly dependent on pH and ionic strength. Surface complexation modelling was performed to elucidate the adsorption mechanism involved. This shows that lignin surfaces contain two main types of acid sites attributed to carboxylic- and phenolic-type surface groups and the phenolic sites have a higher affinity for metal ions than the carboxylic sites.
In this study biosorption potential of pre-treated arca shell biomass for lead, copper, nickel, cobalt and cesium was explored from the artificially prepared solution containing known amount of metals. The effects of pH, initial concentration, biosorbent dosage and contact time were studied in batch experiments. Effects of common ions like sodium, potassium, calcium and magnesium on the sorption capacity of pre-treated arca biomasses were also studied. To analyse the homogeneity of the biomaterial, experiments were performed for eight lots arca shell biomass for all the studies elements and it was observed that relative standard deviation in uptake capacity was within 10% for all elements. At equilibrium, the maximum total uptake by shell biomaterial was 18.33+/-0.44, 17.64+/-0.31, 9.86+/-0.17, 3.93+/-0.11 and 7.82+/-0.36 mg/g for lead, copper, nickel, cesium and cobalt, respectively, under the optimised condition of pH, initial concentration, biosorbent dose and contact time. Effect of all the common ions jointly up to concentration of 50 ppm was negligible for all the elements but at higher levels the cations affects the uptake capacity. Sorption isotherms were studied to explain the removal mechanism of both elements by fitting isotherms data into Lagergren, Freundlich and Langmuir equations. Halls separation factor estimated under optimised condition also favours the sorption potential of these elements using arca shell biomass. Arca shell biomass can be effectively and efficiently employed for removal of studied elements after optimisation of parameters.
The adsorption of Cd2+ and Pb2+ on sugar beet pulp (SBP), a low-cost material, has been studied. In the present work, the abilities of native (SBP) to remove cadmium (Cd2+) and lead (Pb2+) ions from aqueous solutions were compared. The (SBP) an industrial by product and solid waste of sugar industry were used for the removal of Cd2+ and Pb2+ ions from aqueous water. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, adsorbent dose, initial metal ion concentration, and time on uptake. The sorption process was relatively fast and equilibrium was reached after about 70 min of contact. As much as 70-75% removal of Cd2+ and Pb2+ ions for (SBP) are possible in about 70 min, respectively, under the batch test conditions. Uptake of Cd2+ and Pb2+ ions on (SBP) showed a pH-dependent profile. The overall uptake for the (SBP) is at a maximum at pH 5.3 and gives up to 46.1 mg g(-1) for Cd2+ and at pH 5.0 and gives 43.5 mg g(-1) for Pb2+ for (SBP), which seems to be removed exclusively by ion exchange, physical sorption and chelation. A dose of 8 gL(-1) was sufficient for the optimum removal of both the metal ions. The Freundlich represented the sorption data for (SBP). In the presence of 0.1M NaNO3 the level of metal ion uptake was found to reach its maximum value very rapidly with the speed increasing both with the (SPB) concentration and with increasing initial pH of the suspension. The reversibility of the process was investigated. The desorption of Cd2+ and Pb2+ ions which were previously deposited on the (SBP) back into the deionised water was observed only in acidic pH values during one day study period and was generally rather low. The extent of adsorption for both metals increased along with an increase of the (SBP) dosage. (SBP), which is cheap and highly selective, therefore seems to be a promising substrate to entrap heavy metals in aqueous solutions.
The objectives of the present study were to convert soybean straw to a metal ion adsorbent and further to investigate the potential of using the adsorbent for the removal of Cu(2+) from aqueous solution. The soybean straw was water or base washed and citric acid (CA) modified to enhance its nature adsorption capacity. The morphological and chemical characteristics of the adsorbent were evaluated by spectroscopy and N(2)-adsorption techniques. The porous structure, as well as high amounts of introduced free carboxyl groups of CA modified soybean straw makes the adsorbent be good to retain Cu(2+). The adsorption capacities increased when the solution pH increased from 2 to 6 and reached the maximum value at pH 6 (0.64 mmol g(-1) for the base washed, CA modified soybean straw (CA-BWSS)). The Cu(2+) uptake increased and percentage adsorption of the Cu(2+) decreased with the increase in initial Cu(2+) concentration from 1 mM to 20 mM. Both the Langmuir and Freundlich adsorption isotherms were tested, and the Freundlich model fited much better than the Langmuir model. It was found that CA-BWSS have the highest adsorption capacity of the four kinds of pretreated soybean straw.
Heavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment. Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge. Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The major advantages of biosorption over conventional treatment methods include: low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possibility of metal recovery. Cellulosic agricultural waste materials are an abundant source for significant metal biosorption. The functional groups present in agricultural waste biomass viz. acetamido, alcoholic, carbonyl, phenolic, amido, amino, sulphydryl groups etc. have affinity for heavy metal ions to form metal complexes or chelates. The mechanism of biosorption process includes chemisorption, complexation, adsorption on surface, diffusion through pores and ion exchange etc. The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.
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