Single- and multi-component adsorption of cadmium and zinc using activated carbon derived from bagasse--an agricultural waste

Sorption of lead from aqueous solution by chemically modified carbon adsorbents

An indigenously prepared, steam activated and chemically modified carbon from husk and pods of Moringa oleifera (M. oleifera), an agricultural waste, was comparatively examined as an adsorbent for the removal of lead from aqueous solutions. Studies were conducted as a function of contact time, initial metal concentration, dose of adsorbent, agitation speed, particle size and pH. Maximum uptake capacities were found to be, 98.89, 96.58, 91.8, 88.63, 79.43% for cetyltrimethyl ammonium bromide (CTAB), phosphoric, sulfuric, hydrochloric acid treated and untreated carbon adsorbents, respectively. Bangham, pseudo-first- and second-order, intra-particle diffusion equations were implemented to express the sorption mechanism by utilized adsorbents. Adsorption rate of lead ions was found to be considerably faster for chemically modified adsorbents than unmodified. The results of adsorption were fitted to both the Langmuir and Freundlich models. Satisfactory agreement between the metal uptake capacities by the adsorbents at different time intervals was expressed by the correlation coefficient (R(2)). The Langmuir model represented the sorption process better than the Freundlich one, with R(2) values ranging from 0.994 to 0.998.

Mechanisms of competitive adsorption of Pb, Cu, and Cd on peat

Combined use of batch equilibration adsorption and X-ray absorption spectroscopy (XAS) was employed to study the mechanisms of competitive adsorption of Pb, Cu, and Cd on Danish and Heilongjiang peat in single- and multi-solute systems. The adsorption capacity and initial adsorption rate on the same peat in single-solute systems followed the order Pb>Cu>Cd. Both the adsorbed amount of each metal (q'm) and its initial adsorption rate were decreased in multi-solute systems. It was observed that the adsorbed amounts of metals at low-energy adsorption sites (qm,1) decreased pronouncedly compared to those at high-energy adsorption sites (qm,2), indicating that the competitive adsorption of Pb, Cu and Cd occurred mainly at the low-energy adsorption sites. XAS study revealed that both Pb and Cu were coordinated in peat predominantly to carboxylic moieties without excluding the hydroxyl groups, thereby providing an insight into the mechanism of competitive adsorption of Pb and Cu on peat.

Removal of ammonium from aqueous solutions with volcanic tuff

This paper presents kinetic and equilibrium data concerning ammonium ion uptake from aqueous solutions using Romanian volcanic tuff. The influence of contact time, pH, ammonium concentration, presence of other cations and anion species is discussed. Equilibrium isotherms adequately fit the Langmuir and Freundlich models. The results showed a contact time of 3h to be sufficient to reach equilibrium and pH of 7 to be the optimum value. Adsorption capacities of 19 mg NH(4)(+)/g were obtained in multicomponent solutions (containing NH(4)(+), Zn(2+), Cd(2+), Ca(2+), Na(2+)). The presence of Zn and Cd at low concentrations did not decrease the ammonium adsorption capacity. Comparison of Romanian volcanic tuff with synthetic zeolites used for ammonium removal (5A, 13X and ZSM-5) was carried out. The removal efficiciency of ammonium by volcanic tuff were similar to those of zeolites 5A and 13X at low initial ammonium concentration, and much higher than those of zeolite ZSM-5.

Adsorption of phenolic compound by aged-refuse

The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

Sorption of Zn(II), Pb(II), and Co(II) using natural sorbents: equilibrium and kinetic studies

Natural Jordanian sorbent (consisting of primary minerals, i.e., quartz and aluminosilicates and secondary minerals, i.e., calcite and dolomite) was shown to be effective for removing Zn(II), Pb(II) and Co(II) from aqueous solution. The major mineral constitutions of the sorbent are calcite and quartz. Dolomite was present as minor mineral and palygorskite was present as trace mineral. The sorbent has microporous structure with a modest surface area of 14.4 m(2)g(-1). pH(zpc) (pH of zero point charge) of the sorbent was estimated by alkaline-titration methods and a value of 9.5 was obtained. The sorption capacities of the metals were: 2.860, 0.320, 0.076 mmol cation g(-1) for Zn(II), Pb(II) and Co(II) at pH 6.5, 4.5 and 7.0, respectively. The shape of the experimental isotherm of Zn(II) was of a "L2" type, while that of Pb(II) and Co(II) was of a "L1" type according to Giles classification for isotherms. Sorption data of metals were described by Langmuir and Freundlich models over the entire concentration range. It was found that the mechanism of metal sorption was mainly due to precipitation of metal carbonate complexes. The overall sorption capacity decreased after acid treatment, as this decreased the extent of precipitation on calcite and dolomite. The effect of Zn(II) ions concentration on sorption kinetics was investigated. Kinetic data were accurately fitted to pseudo-first order and external diffusion models which indicated that sorption of Zn(II) occurred on the exterior surface of the sorbent and the contribution of internal diffusion mechanism was insignificant. Furthermore, the sorption rate of Zn(II) was found to be slow, where only 10-20% of the maximum capacity was utilized in the first 30 min of interaction.

Single, binary, and multicomponent sorption of iron and manganese on lignite

Acid mine drainage (AMD) has long been a significant environmental problem resulting from the microbial oxidation of iron pyrite in the presence of water and air, affording an acidic solution that contains toxic metal ions. The main objective of this study was to remove metal ions [Fe(II), Fe(III), Mn(II), Zn(II)] from AMD using lignite, a low-cost adsorbent. The lignite sorbent was utilized for the sorption of ferrous, ferric, manganese, zinc, and calcium ions in aqueous solutions. Studies were performed at different pH to find optimum pH. Equilibrium isotherms were determined to assess the maximum adsorption capacity of lignite for different metal ions. Sorption capacities were compared in single, binary, ternary, and multicomponent systems. The sorption data are correlated with Freundlich and Langmuir isotherms in each system. Both Freundlich and Langmuir isotherms fit the data reasonably well in terms of regression coefficients. Sorption studies were also performed at different temperatures to obtain the thermodynamic parameters of the process. The maximum lignite adsorption capacities at 25 degrees C were 34.22, 25.84, and 11.90 mg/g for Fe(II), Mn(II), and Fe(III), respectively. Adsorption of Fe(2+) (24.70 mg/g at 10 degrees C and 46.46 mg/g at 40 degrees C) increased with increased temperature, while Mn(2+) adsorption (28.11 mg/g at 10 degrees C and 7.70 mg/g at 40 degrees C) decreased with increased temperature.

Adsorption of Cu(II) and Ni(II) on solid humic acid from the Azraq area, Jordan

Isotherms of adsorption of Cu(II) and Ni(II) onto solid Azraq humic acid (AZHA) were studied at different pH (2.0-3.7) values and 0.1 M NaClO4 ionic strength. The Langmuir monolayer adsorption capacity was found to range from 0.1 to 1.0 mmol metal ion/g AZHA, where Cu(II) has higher adsorptivity than Ni(II). The previously reported NICA-Donnan parameters for sorption of Cu(II) on HA fit the amount of Cu(bound) determined in the present study at pH 3.7 but underestimates those at pH values of 3.0, 2.4, and 2.0. The contribution of low affinity sites to binding of metal ions increases with decreasing pH and increasing metal ion loading. The aggregation of HA, which is facilitated by decreasing pH and increasing metal loading, may increase the ability of low-affinity sites to encapsulate metal ions. The binding of Ni(II) to HA exhibits less heterogeneity and less multidentism than that of Cu(II). AZHA loaded with Cu(II) and Ni(II) was found to be insoluble in water with no measurable amount of desorbed metal ions.

Effect of surface modification of an engineered activated carbon on the sorption of 2,4-dichlorophenoxy acetic acid and benazolin from water

The performance of a conventional (F400) and a surface modified activated carbon (F400AN) has been investigated for the sorption of benazolin and 2,4-dichlorophenoxy acetic acid (2,4-D) from water. It was observed that the modified carbon, F400AN, which was obtained by annealing the conventional sample had a higher BET surface area (960 m2 g(-1) compared to 790 m2 g(-1)) and it had a higher proportion of micropores. This was attributed to the loss of oxygen containing functional groups during the thermal treatment. Zeta potential and pH titration measurements also showed that acidic functionality had been lost on the F400AN sample. The adsorption data were analysed and were fitted well using the Langmuir isotherm. The modified carbon marginally out-performed the conventional activated carbon for sorption of these two herbicides. Thermodynamic parameters (DeltaG0, DeltaH0, and DeltaS0) were determined and their values indicated that the sorption process was spontaneous and endothermic for both herbicides. A pseudo-second-order kinetic model was employed for analysing the kinetic data. It was concluded that the herbicide sorption process was controlled by a film diffusion mechanism.

Single, binary and multi-component adsorption of copper and cadmium from aqueous solutions on Kraft lignin—a biosorbent

A new biosorbent for removing toxic metal ions from water/industrial wastewater has been investigated using by-product lignin from paper production. Lignin was extracted from black liquor waste, characterized and utilized for the removal of copper and cadmium from aqueous solutions in single, binary and multi-component systems. Adsorption studies were conducted at different temperatures, lignin particle sizes, pHs and solid to liquid ratios. All the studies were conducted by a batch method to determine equilibrium and kinetic parameters. The Langmuir and Freundlich isotherm models were applied. The Langmuir model fits best the equilibrium isotherm data. The maximum lignin adsorption capacities at 25 degrees C were 87.05 mg/g (1.37 mmol/g) and 137.14 mg/g (1.22 mmol/g) for Cu(II) and Cd(II), respectively. Adsorption of Cu2+ (68.63 mg/g at 10 degrees C and 94.68 mg/g at 40 degrees C) and Cd2+ (59.58 mg/g at 10 degrees C and 175.36 mg/g at 40 degrees C) increased with an increase in temperature. Copper and cadmium adsorption followed pseudo-second order rate kinetics. From kinetic studies, various rate and thermodynamic parameters such as effective diffusion coefficients, activation energy, and activation entropy were evaluated. Adsorption occurs through a particle diffusion mechanism at temperatures 10 and 25 degrees C while at 40 degrees C it occurs through a film diffusion mechanism. The sorption capacity of black liquor lignin is higher than many other adsorbents/carbons/biosorbents utilized for the removal of Cu(II) and Cd(II) from water/wastewater in single and multi-component systems.

Thermodynamic parameters for adsorption equilibrium of heavy metals and dyes from wastewater with low-cost adsorbents

This note revisits the literature evaluating the thermodynamic parameters of adsorption equilibrium uptakes of heavy metals and dyes from water and wastewater streams using low-cost adsorbents derived from agricultural waste, industrial wastes, inorganic particulates, or some natural products. We highlighted the possible flaws in some adsorption studies when their thermodynamic parameters were assessed, since compensation effects during enthalpy and entropy evaluation were possibly overlooked.

Sorption of Zn(II) in aqueous solutions by scoria

We conducted kinetic and equilibrium sorption experiments on removal of Zn(II) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The batch-type kinetic sorption tests under variable conditions indicated that the percentage of Zn(II) removal by scoria increases with decreasing initial Zn(II) concentration, particle size, and sorbate/sorbent ratio. However, the sorption capacity decreases with the decrease of the initial Zn(II) concentration and sorbate/sorbent ratio. Equilibrium sorption tests show that Jeju scoria has a larger capacity and affinity for Zn(II) sorption than commercial powdered activated carbon (PAC); at initial Zn(II) concentrations of more than 10mM, the sorption capacity of Jeju scoria is about 1.5 times higher than that of PAC. The acquired sorption data are better fitted to the Langmuir isotherm than the Freundlich isotherm. Careful examination of ionic concentrations in sorption batches suggests that the sorption behavior is mainly controlled by cation exchange and typically displays characteristics of 'cation sorption'. The Zn(II) removal capacity decreases when solution pH decreases because of the competition with hydrogen ions for sorption sites, while the Zn(II) removal capacity increases under higher pH conditions, likely due to hydroxide precipitation. At an initial Zn(II) concentration of 5.0mM, the removal increases from 70% to 96% with the increase of initial pH from 3.0 to 7.0. We recommend Jeju scoria as an economic and efficient sorbent for Zn(II) in contaminated water.

Removal of alpha-picoline, beta-picoline, and gamma-picoline from synthetic wastewater using low cost activated carbons derived from coconut shell fibers

In the present study the ability of activated carbons developed from coconut shell fibers to remove alpha-picoline, beta-picoline, and gamma-picoline from aqueous solution in the broad range of concentrations (1-100 mg/L) is investigated. The derived carbons are designated as FAC (activated carbon derived from coconut shell fibers without any treatment) and ATFAC (activated carbon derived from acid treated coconut shell fibers). Systematic equilibrium and kinetic adsorption studies at different pH, temperatures, particle size, and solid-to-liquid ratio were carried out to determine various parameters necessary to establish the fixed bed reactors. The Langmuir and Freundlich models were applied and the data are not fitted well by the Freundlich and Langmuir equations, but the Langmuir model has an edge over Freundlich model. The monolayer adsorption capacity (Q0) as calculated using Langmuir adsorption isotherm of the activated carbons viz., FAC and ATFAC is found to increase with an increase in temperature confirming the endothermic process. The ATFAC has a higher sorption capacity than FAC. Overall the adsorption of alpha-picoline, beta-picoline, and y-picoline on FAC and ATFAC follow the order FACalpha-picoline < ATFACalpha-picoline < FAC gamma-picoline < ATFACbeta-picoline < FACbeta picoline < ATFAC gamma-picoline. The adsorption of alpha-,beta-, and gamma-picoline followed the pseudosecond-order rate kinetics. On the basis of these studies, various parameters such as effective diffusion coefficients, activation energy, and entropy of activation were evaluated to establish the mechanisms. It was concluded that the adsorption occurred through particle diffusion at low temperatures viz., 10 degrees C and 25 degrees C (except alpha-picoline where it was film diffusion), while at 40 degrees C it occurred through film diffusion. Similarly at concentrations of 25 and 50 mg/L the adsorption was particle diffusion controlled (except for alpha-picoline where it was film diffusion), while at > 50 mg/L it was film diffusion controlled.

Prediction of simultaneous adsorption of Cu(II) and Pb(II) onto activated carbon by conventional Langmuir type equations

Removal of Cu(II) and Pb(II) by adsorption onto activated carbon was examined in single- and binary-component aqueous solutions representative of contaminated solutions containing heavy metals. Reversibility of adsorption of the heavy metals on the activated carbon was evaluated by desorption experiments. The number of the maximum adsorption sites and adsorption equilibrium constants of Cu(II) and Pb(II) were estimated by the results of single-component systems assuming the Langmuir adsorption model. The adsorption sites per gram of activated carbon resulted in similar values for Cu(II) and Pb(II) from the isotherms. The adsorption constant for Pb(II) was nearly 1.8 times greater than that of Cu(II). Rate constants of adsorption and desorption were also estimated from the kinetic analysis. Using the single set of common parameters obtained from the single-component systems, the experimental results for a binary-component system were quantitatively predicted. Competitive adsorption of Cu(II) and Pb(II) on the same adsorption sites was confirmed by both experimental and predicted results of adsorption in the binary mixture.

Development of activated carbon using vine shoots (Vitis vinifera) and its use for wine treatment

An abundant and low-cost agricultural waste such as vine shoots (Vitis vinifera) (VS), which is generated by the annual pruning of vineyards, has been used as raw material in the preparation of powder activated carbon (AC) with a view to develop a new fining agent for white wines. A commercial activated carbon, S5X-Agrovin, was used for comparison purposes. From VS size-reduced pieces, AC was prepared using phosphoric acid as activating agent. The concentration of the H(3)PO(4) solution, the impregnation temperature, and the carbonization conditions were controlled. The carbons were texturally characterized by gas adsorption (N(2), -196 degrees C), mercury porosimetry, and density measurements. FT-IR spectroscopy was used in the analysis of the surface functional groups and structures of the carbons. Three varieties of white wine (i.e., cv. Cayetana, cv. Macabeo, and cv. Sauvignon Blanc) were treated with the activated carbons. Color changes were monitored by UV-vis spectrometry. Significant differences in the degree of uptake of polyphenols were observed depending on the wine variety and on the method of preparation of activated carbon. The carbon prepared by first impregnation of VS with the 60 vol% H(3)PO(4) solution at 50 degrees C and by then carbonization of the resultant product at 400 degrees C for 2 h presents a higher ability to discolor the white wines. The action of this carbon is comparable to that shown by the commercial product. Both carbons possess a well-developed porosity in the macropore range.

Experimental design methodology for the preparation of carbonaceous sorbents from sewage sludge by chemical activation--application to air and water treatments

The objective of this study is to optimize experimental conditions of sorbent preparation from sewage sludge using experimental design methodology. Series of carbonaceous sorbents have been prepared by chemical activation with sulfuric acid. The sorbents produced were characterized, and their properties (surface chemistry, porous and adsorptive properties) were analyzed as a function of the experimental conditions (impregnation ratio, activation temperature and time). Carbonaceous sorbents developed from sludge allow copper ion, phenol and dyes (Acid Red 18 and Basic Violet 4) to be removed from aqueous solution as well as VOC from gas phase. Indeed, according to experimental conditions, copper adsorption capacity varies from 77 to 83 mg g(-1), phenol adsorption capacity varies between 41 and 53 mg g(-1) and VOC adsorption capacities (acetone and toluene) range from 12 to 54 mg g(-1). Each response has been described by a second-order model that was found to be appropriate to predict most of the responses in every experimental region. The most influential factors on each experimental design response have been identified. Regions in which optimum values of each factor were achieved for preparation of activated carbons suitable for use in wastewater and gas treatments have been determined using response surfaces methodology. In order to have a high mass yield and to minimize the energetic cost of the process, the following optimal conditions, 1.5 g of H2SO4 g(-1) of sludge, 700 degrees C and 145 min are more appropriate for use of activated carbon from sludge in water and gas treatments.

Adsorption kinetics of zinc in multicomponent ionic systems

Using commercial activated carbon as an adsorbent, the kinetics of adsorption of zinc from multicomponent ionic systems having cadmium and mercury has been studied and reported. The variables investigated have been the chemical nature, ionic strength, and pH of the adsorptive (Zn2+) solution. The adsorption of Zn2+ is speeded up by the presence of Cd2+ and Hg2+ ions provided that the concentration of these two ions is high as compared to the concentration of Zn2+. When the ionic strength of the solution in relative terms is high (i.e., > 3 x 10(-4) M), however, the adsorption of Zn2+ decelerates. Also, the adsorption process is greatly accelerated at pH 12, whereas at pH 2 it does not occur at all.

Adsorption of copper and lead ions onto regenerated sludge from a water treatment plant

In this study, water treatment sludges were sintered under various experimental conditions to generate Al-containing adsorbents. The adsorption of Cu2+ and Pb2+ onto sintered oxide was examined and sorption results were further modeled using a surface complex model. The specific surface area of the sintered adsorbent was substantially reduced from 30 m2/g (dried sludge) to 2 m2/g (sinter sludge). The pH-adsorption-edges of both Cu2+ and Pb2+ were shifted towards a higher pH than the edges of the unsintered adsorbent, revealing reduced affinity of the sintered adsorbent for metal ions. Metal leaching was measured by the TCLP procedure, and the results indicated that the amount of metal leaching by the sintered adsorbent was negligible. The effect of background electrolytes on Cu2+ and Pb2+ sorption was negligible. Triple-layer model (TLM) simulation revealed that Cu2+ and Pb2+ sorption on sintered adsorbent involves inner-sphere interactions and the dominant surface metal species are monodentates of Me2+ and MeOH+. The intrinsic adsorption constants of Cu2+ and Pb2+ on dried sludge, adsorbent sintered at 1000 degrees C, and adsorbent sintered at 1100 degrees C were also examined.

Characterization and nickel sorption kinetics of a new metal hyper-accumulator Bacillus sp

The heavy metal-resistant bacterial strain SJ-101 has been isolated from fly ash contaminated soil. Based on the morphological and biochemical characteristics, the isolate SJ-101 was presumptively identified as Bacillus sp. The adsorption isotherms revealed the absolute adsorption capacity (Q degrees) of 244 mg Ni g(-1) dry cell mass vis-à-vis 161 mg Ni g(-1) synthetic resin (Amberlite IR-120). The higher relative adsorption capacity (K(F)) of 7.37, and the intensity of adsorption (1/n) of 0.58 with dry cell biomass suggested higher affinity of Bacillus cells towards nickel ions. The data conform to the Langmuir adsorption model relatively better than the Freundlich model. The thermodynamic parameters indicated the feasibility, endothermic, and interactive nature of nickel adsorption process on the cell surface. Higher Ni tolerance and sorption capacity of Bacillus sp. SJ-101, explicitly signifies its implications in Ni bioremediation process.