Adsorption isotherm and kinetic modeling of 2,4-D pesticide on activated carbon derived from date stones

In this work, the adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on activated carbon derived from date stones (DSAC) was studied with respect to pH and initial 2,4-D concentration. The experimental data were analyzed by the Freundlich isotherm, the Langmuir isotherm, and the Temkin isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 238.10 mg/g. Pseudo-first and pseudo-second-order kinetics models were tested with the experimental data, and pseudo-first-order kinetics was the best for the adsorption of 2,4-D by DSAC with coefficients of correlation R(2)>or=0.986 for all initial 2,4-D concentrations studied. The results indicated that the DSAC is very effective for the adsorption of 2,4-D from aqueous solutions.     

Removal of direct blue-86 from aqueous solution by new activated carbon developed from orange peel

The use of low-cost, easy obtained, high efficiency and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. This study investigates the potential use of activated carbon prepared from orange peel for the removal of direct blue-86 (DB-86) (Direct Fast Turquoise Blue GL) dye from simulated wastewater. The effects of different system variables, adsorbent dosage, initial dye concentration, pH and contact time were studied. The results showed that as the amount of the adsorbent increased, the percentage of dye removal increased accordingly. Optimum pH value for dye adsorption was determined as approximately 2.0. Maximum dye was sequestered within 30min after the beginning for every experiment. The adsorption of direct blue-86 followed a pseudo-second-order rate equation and fit well Langmuir, Tempkin and Dubinin-Radushkevich (D-R) equations better than Freundlich and Redlich-Peterson equations. The maximum removal of direct blue-86 was obtained at pH 2 as 92% for adsorbent dose of 6gL(-1) and 100mgL(-1) initial dye concentration at room temperature. The maximum adsorption capacity obtained from Langmuir equation was 33.78mgg(-1). Furthermore, adsorption kinetics of DB-86 was studied and the rate of adsorption was found to conform to pseudo-second-order kinetics with a good correlation (R2>0.99) with intraparticle diffusion as one of the rate determining steps. Activated carbon developed from orange peel can be attractive options for dye removal from diluted industrial effluents since test reaction made on simulated dyeing wastewater show better removal percentage of DB-86.     

High performance activated carbon for benzene/toluene adsorption from industrial wastewater

A coal-tar-derived mesophase was chemically activated to produce a high surface area (∼3200 m²/g) carbon with a porosity made up of both micropores and mesopores. Its adsorption capacities were found to be among the highest ever reported in literature, reaching values of 860 mg/g and 1200 mg/g for the adsorption of benzene and toluene, respectively, and 1200 mg/g for the combined adsorption of benzene and toluene from an industrial wastewater. Such high values imply that the entire pore system, including the mesopore fraction, is involved in the adsorption process. The almost complete pore filling is thought to be due to the high relative concentrations of the tested solutions, resulting from the low saturation concentration values for benzene and toluene, which were obtained by fitting the adsorption data to the BET equation in liquid phase. The kinetics of adsorption in the batch experiments which were conducted in a syringe-like adsorption chamber was observed to proceed in accordance with the pseudo-second order kinetic model. The combined presence of micropores and mesopores in the material is thought to be the key to the high kinetic performance, which was outstanding in a comparison with other porous materials reported in the literature.     

Removal of chromium(III) from tannery wastewater using activated carbon from sugar industrial waste

Chromium is commonly found in huge quantities in tannery wastewaters. For this reason, the removal and recovery of the chromium content of tannery wastewaters is crucial for environmental protection and economic reasons. Removal and recovery of chromium were carried out by using low-cost potential adsorbents. For this purpose three types of activated carbon; C1, the waste generated from sugar industry as waste products and the others (C2, C3) are commercial granular activated carbon, were used. The adsorption process and extent of adsorption are dependent on the physical and chemical characteristics of the adsorbent, adsorbate and experimental condition. The effect of pH, particle size and different adsorbent on the adsorption isotherm of Cr(III) was studied in batch system. The sorption data fitted well with Langmuir adsorption model. The efficiencies of activated carbon for the removal of Cr(III) were found to be 98.86, 98.6 and 93 % for C1, C2 and C3, respectively. The order of selectivity is C1>C2>C3 for removal of Cr(III) from tannery wastewater. Carbon "C1" of the highest surface area (520.66 m(2)/g) and calcium content (333.3 mg/l) has the highest adsorptive capacity for removal of Cr(III). The results revealed that the trivalent chromium is significantly adsorbed on activated carbon collected from sugar industry as waste products and the method could be used economically as an efficient technique for removal of Cr(III) and purification of tannery wastewaters.     

In situ modification of activated carbons developed from a native invasive wood on removal of trace toxic metals from wastewater

Activated carbons were developed by phosphoric acid activation of sawdust from Prosopis ruscifolia wood, an indigenous invasive species of degraded lands, at moderate conditions (acid/precursor ratio=2, 450 degrees C, 0.5h). For in situ modification of their characteristics, either a self-generated atmosphere or flowing air was used. The activated carbons developed in the self-generated atmosphere showed higher BET surface area (2281m2/g) and total pore volume (1.7cm3/g) than those obtained under flowing air (1638m2/g and 1.3cm3/g). Conversely, the latter possessed a higher total amount of surface acidic/polar oxygen groups (2.2meq/g) than the former (1.5meq/g). To evaluate their metal sorption capability, adsorption isotherms of Cu(II) ion from model solutions were determined and properly described by the Langmuir model. Maximum sorption capacity (Xm) for the air-derived carbons (Xm=0.44mmol/g) almost duplicated the value for those obtained in the self-generated atmosphere (Xm=0.24mmol/g), pointing to a predominant effect of the surface functionalities on metal sequestering behaviour. The air-derived carbons also demonstrated a superior effectiveness in removing Cd(II) ions as determined from additional assays in equilibrium conditions. Accordingly, effective phosphoric acid-activated carbons from Prosopis wood for toxic metals removal from wastewater may be developed by in situ modification of their characteristics operating under flowing air.     

Removal of chromium (VI) from aqueous solution using treated oil palm fibre

This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution.     

Adsorption dynamics of chlorinated hydrocarbons from multi-component aqueous solution onto activated carbon

The results and a numerical simulation of studies on dynamics of the adsorption from seven-component aqueous solution of light chlorinated hydrocarbons on activated carbon have been presented. Aqueous solution of 1,2-dichloroethane (12DCE), 1,1,2,2-tetrachloroethane (S-TET), chloroform (CHCl(3)), carbon tetrachloride (CCl(4)), 1,1-dichloroethene (VDC), perchloroethene (PER) and 1,1,2-trichloroethene (TRI) was used. Concentrations of chlorohydrocarbons were similar as in wastewater from vinyl chloride plant. A cell model that incorporates the diffusion through a laminar layer of liquid around a particle was used to describe the experimental results. The applied calculation methods, which take kinetics into account, allows to well describe a phenomenon of dynamic adsorption. Mean relative deviations between the experimental and calculated values amounted 17%. The breakthrough curves become steeper along with an increase of the bed height. A consistency of the experimental results with those calculated indicates for a negligible contribution of the axial diffusion on the dynamic adsorption process of light chlorinated hydrocarbons from aqueous solution under the hydrodynamic conditions corresponding to the Reynolds number equal to 1.3. Determined optimal bed height for waste linear flow rate-15 cm/min is in the range 80-120 cm.     

Removal of phenol from aqueous solutions by adsorption onto activated carbon prepared from biomass material

Activated carbon derived from rattan sawdust (ACR) was evaluated for its ability to remove phenol from an aqueous solution in a batch process. Equilibrium studies were conducted in the range of 25–200 mg/L initial phenol concentrations, 3–10 solution pH and at temperature of 30 °C. The experimental data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. Equilibrium data fitted well to the Langmuir model with a maximum adsorption capacity of 149.25 mg/g. The dimensionless separation factor R_L revealed the favorable nature of the isotherm of the phenol-activated carbon system. The pseudo-second-order kinetic model best described the adsorption process. The results proved that the prepared activated carbon was an effective adsorbent for removal of phenol from aqueous solution.     

The dynamic adsorption characteristics of phenol by granular activated carbon

The objective of the present work is to determine the operating conditions of an activated carbon filter, based on the characteristics of breakthrough curves. For this we apply the technical developed by Mickaels for the ionic exchange and applied by Luchkis for the adsorption, and which is the mass transfer zone. To reach our goal, an evaluation of the operating conditions (height of the bed, flow and concentration of effluent) on the characteristics of the mass transfer zone was made and an explanation of the mechanism of adsorption was given. Thereafter a modeling of the experimental results was done.     

Adsorption of aromatic organic acids onto high area activated carbon cloth in relation to wastewater purification

Adsorption of aromatic organic acids: benzoic acid (BA), salicylic acid (SA), p-aminobenzoic acid (pABA) and nicotinic acid (NA), onto high area activated carbon cloth from solutions in 0.4 M H(2)SO(4), in water at natural pH, in 0.1 M NaOH and also from solutions having pH 7.0 were studied by in situ UV-spectroscopic technique. The first-order rate law was found to be applicable for the kinetic data of adsorption. The rates and extents of adsorption of the organic acids were the highest from water or 0.4 M H(2)SO(4) solutions and the lowest from 0.1 M NaOH solution. The order of rates and extents of adsorption of the four organic acids in each of the four solutions (0.4 M H(2)SO(4), water, solution of pH 7.0 and 0.1 M NaOH) was determined as SA>BA>NA approximately pABA. These observed orders were explained in terms of electrostatic, dispersion and hydrogen bonding interactions between the surface and the adsorbate species, taking the charge of the carbon surface and the adsorbate in each solution into account. Adsorption of BA in molecular form or in benzoate form was analyzed by treating the solution as a mixture of two components and applying Lambert-Beer law to two-component system. The adsorption isotherm data of the systems studied were derived at 30 degrees C and fitted to Langmuir and Freundlich equations.     

Removal of tiemonium methylsulfate,from aqueous solutions using activated carbon prepared from date stones

The retention of a pharmaceutical compound, tiemonium methylsulfate (TIM), from aqueous solutions by adsorption onto activated carbon prepared from date stones (AC–DS) was investigated. Physical and chemical characteristics of this material were also determined. Results showed that pH 8 was optimal for TIM adsorption. Among the kinetic models considered, the pseudo-second-order model was the most appropriate to describe experimental data. Regarding adsorption isotherms, it was shown that the Sips model accurately describe the sorption of TIM onto AC–DS with a correlation factor R²?>?0.98. The adsorption capacity of AC–DS was found to be 42.2?mg?g^?1 at 10°C and 60.5?mg?g^?1 at 25°C, confirming its efficiency for the removal of this compound from aqueous solutions. The values of ΔG⁰ and ΔH⁰ confirmed that the adsorption of TIM onto AC–DS was spontaneous and endothermic in nature and hence more effective at high temperatures. An irregular increase in the randomness was suggested at the AC–DS solution interface during the adsorption process for positive values of ΔS⁰.     

Use of adsorption process to remove organic mercury thimerosal from industrial process wastewater

Carbon adsorption process is tested for removal of high concentration of organic mercury (thimerosal) from industrial process wastewater, in batch and continuously flow through column systems. The organic mercury concentration in the process wastewater is about 1123 mg/L due to the thimerosal compound. Four commercially available adsorbents are tested for mercury removal and they are: Calgon F-400 granular activated carbon (GAC), CB II GAC, Mersorb GAC and an ion-exchange resin Amberlite GT73. The adsorption capacity of each adsorbent is described by the Freundlich isotherm model at pH 3.0, 9.5 and 11.0 in batch isotherm experiments. Acidic pH was favorable for thimerosal adsorption onto the GACs. Columns-in-series experiments are conducted with 30-180 min empty bed contact times (EBCTs). Mercury breakthrough of 30 mg/L occurred after about 47 h (96 Bed Volume Fed (BVF)) of operation, and 97 h (197 BVF) with 120 min EBCT and 180 min EBCT, respectively. Most of the mercury removal is attributed to the 1st adsorbent column. Increase in contact time by additional adsorbent columns did not lower the effluent mercury concentration below 30 mg/L. However, at a lower influent wastewater pH 3, the mercury effluent concentration decreased to less than 7 mg/L for up to 90 h of column operation (183 BVF).     

Adsorption of malachite green from aqueous solution onto carbon prepared from Arundo donax root

Arundo donax root carbon (ADRC), a new adsorbent, was prepared from Arundo donax root by carbonization. The surface area of the adsorbent was determined 158 m²/g by N₂ adsorption isotherm. Batch adsorption experiments were carried out for the removal of malachite green (MG) from aqueous solution using ADRC as adsorbent. The effects of various parameters such as solution pH (3–10), carbon dose (0.15–1.0 g/100 ml) and initial MG concentration (10–100 mg/l) on the adsorption system were investigated. The effective pH was 5–7 and the optimum adsorbent dose was found to be 0.6 g/100 ml. Equilibrium experimental data at 293, 303 and 313 K were better represented by Langmuir isotherm than Freundlich isotherm using linear and non-linear methods. Thermodynamic parameters such as ΔG, ΔH and ΔS were also calculated. The negative Gibbs free energy change and the positive enthalpy change indicated the spontaneous and endothermic nature of the adsorption. The adsorption equilibrium time was 180 min. Adsorption kinetics was determined using pseudo-first-order model, pseudo-second-order model and intraparticle diffusion model. The results showed that the adsorption of MG onto ADRC followed pseudo-second-order model.     

Removal of disperse dye from aqueous solution using waste-derived activated carbon: Optimization study

The purpose of this work is to obtain optimal preparation conditions for activated carbons prepared from rattan sawdust (RSAC) for removal of disperse dye from aqueous solution. The RSAC was prepared by chemical activation with phosphoric acid using response surface methodology (RSM). RSM based on a three-variable central composite design was used to determine the effect of activation temperature (400–600 °C), activation time (1–3 h) and H₃PO₄:precursor (wt%) impregnation ratio (3:1–6:1) on C.I. Disperse Orange 30 (DO30) percentage removal and activated carbon yield were investigated. Based on the central composite design, quadratic model was developed to correlate the preparation variables to the two responses. The most influential factor on each experimental design responses was identified from the analysis of variance (ANOVA). The optimum conditions for preparation of RSAC, which were based on response surface and contour plots, were found as follows: temperature of 470 °C, activation time of 2 h and 14 min and chemical impregnation ratio of 4.45.     

Removal of toxic chromium from wastewater using green alga Ulva lactuca and its activated carbon

Biosorption of heavy metals can be an effective process for the removal of toxic chromium ions from wastewater. In this study, the batch removal of toxic hexavalent chromium ions from aqueous solution, saline water and wastewater using marine dried green alga Ulva lactuca was investigated. Activated carbon prepared from U. lactuca by acid decomposition was also used for the removal of chromium from aqueous solution, saline water and wastewater. The chromium uptake was dependent on the initial pH and the initial chromium concentration, with pH approximately 1.0, being the optimum pH value. Langmuir, Freundlich, Redlich-Peterson and Koble-Corrigan isotherm models were fitted well the equilibrium data for both sorbents. The maximum efficiencies of chromium removal were 92 and 98% for U. lactuca and its activated carbon, respectively. The maximum adsorption capacity was found to be 10.61 and 112.36 mg g(-1) for dried green alga and activated carbon developed from it, respectively. The adsorption capacities of U. lactuca and its activated carbon were independent on the type of solution containing toxic chromium and the efficiency of removal was not affected by the replacing of aqueous solution by saline water or wastewater containing the same chromium concentration. Two hours were necessary to reach the sorption equilibrium. The chromium uptake by U. lactuca and its activated carbon form were best described by pseudo second-order rate model. This study verifies the possibility of using inactivated marine green alga U. lactuca and its activated carbon as valuable material for the removal of chromium from aqueous solutions, saline water or wastewater.     

Performance of a modified multi-stage bubble column reactor for lead(II) and biological oxygen demand removal from wastewater using activated rice husk

The excessive release of wastewater into the environment is a major concern worldwide. Adsorption is the one of the most effective technique for treatment of wastewater. In this work activated carbon prepared from rice husk has been used as an adsorbent. In the present investigation a three phase modified multi-stage bubble column reactor (MMBCR) has been designed to remove lead and biochemical oxygen demand (BOD) from wastewater by means of its adsorption onto the surface of activated rice husk. The multi-staging has been achieved by hydrodynamically induced continuous bubble generation, breakup and regeneration. Under optimum conditions, maximum lead and BOD reduction achieved using activated rice husk was 77.15% and 19.05%, respectively. Results showed MMBCR offered appreciated potential benefits for lead removal from wastewater and BOD removal, even this extent of removal is encouraging and the MMBCR can be used a pretreatment unit before subjecting the wastewater to biological treatment.     

Potential of pomegranate husk carbon for Cr(VI) removal from wastewater: kinetic and isotherm studies

Pomegranate husk was converted into activated carbon and tested for its ability to remove hexavalent chromium from wastewater. The new activated carbon was obtained from pomegranate husk by dehydration process using concentrated sulfuric acid. The important parameters for the adsorption process such as pH, metal concentration and sorbent weight were investigated. Batch equilibrium experiments exhibited that a maximum chromium uptake was obtained at pH 1.0. The maximum adsorption capacity for pomegranate husk activated carbon was 35.2mgg(-1) as calculated by Langmuir model. The ability of activated carbon to remove chromium from synthetic sea water, natural sea water and wastewater was investigated as well. Different isotherm models were used to analyze the experimental data and the models parameters were evaluated. This study showed that the removal of toxic chromium by activated carbon developed from pomegranate husk is a promising technique.     

Removal of nitroimidazole antibiotics from aqueous solution by adsorption/bioadsorption on activated carbon

The objective of the present study was to analyse the behaviour of activated carbon with different chemical and textural properties in nitroimidazole adsorption, also assessing the combined use of microorganisms and activated carbon in the removal of these compounds from waters and the influence of the chemical nature of the solution (pH and ionic strength) on the adsorption process. Results indicate that the adsorption of nitroimidazoles is largely determined by activated carbon chemical properties. Application of the Langmuir equation to the adsorption isotherms showed an elevated adsorption capacity (X_m = 1.04–2.04 mmol/g) for all contaminants studied. Solution pH and electrolyte concentration did not have a major effect on the adsorption of these compounds on activated carbon, confirming that the principal interactions involved in the adsorption of these compounds are non-electrostatic. Nitroimidazoles are not degraded by microorganisms used in the biological stage of a wastewater treatment plant. However, the presence of microorganisms during nitroimidazole adsorption increased their adsorption on the activated carbon, although it weakened interactions between the adsorbate and carbon surface. In dynamic regime, the adsorptive capacity of activated carbon was markedly higher in surface water and groundwater than in urban wastewaters.     

Comparative analysis of linear and non-linear method of estimating the sorption isotherm parameters for malachite green onto activated carbon

The experimental equilibrium data of malachite green onto activated carbon were fitted to the Freundlich, Langmuir and Redlich-Peterson isotherms by linear and non-linear method. A comparison between linear and non-linear of estimating the isotherm parameters was discussed. The four different linearized form of Langmuir isotherm were also discussed. The results confirmed that the non-linear method as a better way to obtain isotherm parameters. The best fitting isotherm was Langmuir and Redlich-Peterson isotherm. Redlich-Peterson is a special case of Langmuir when the Redlich-Peterson isotherm constant g was unity.     

Liquid-phase adsorption of phenols using activated carbons derived from agricultural waste material

Physical and chemical properties of activated carbons prepared from coconut shells (SAC and ATSAC) were studied. The adsorption equilibria and kinetics of phenol and 2,4-dichlorophenol from aqueous solutions on such carbons were then examined at three different temperatures (10, 25 and 40 °C). Adsorption of both phenol and 2,4-dichlorophenol increased with an increase in temperature. The experimental data were analyzed using the Langmuir and Freundlich isotherm models. Both the isotherm models adequately fit the adsorption data for both the phenols. The carbon developed through the acid treatment of coconut shells (ATSAC) exhibited relatively higher monolayer adsorption capacity for phenol (0.53 mmol g⁻¹) and 2,4-dichlorophenol (0.31 mmol g⁻¹) as compared to that developed by thermal activation (SAC) with adsorption capacity of 0.36 and 0.20 mmol g⁻¹, for phenol and 2,4-dichlorophenol, respectively. The equilibrium sorption and kinetics model parameters and thermodynamic functions were estimated and discussed. The thermodynamic parameters (free energy, enthalpy and entropy changes) exhibited the feasibility and spontaneous nature of the adsorption process. The sorption kinetics was studied using the pseudo-first-order and second-order kinetics models. The adsorption kinetics data for both the phenol and 2,4-dichlorophenol fitted better to the second-order model. An attempt was also made to identify the rate-limiting step involved in the adsorption process. Results of mass transfer analysis suggested the endothermic nature of the reaction and change in the mechanism with time and initial concentration of the adsorbate. The results of the study show that the activated carbons derived from coconut shells can be used as potential adsorbent for phenols in water/wastewater.