Removal of pyridine from aqueous solution using low cost activated carbons derived from agricultural waste materials

The purpose of this study is to suggest an efficient process, which does not require a big investment for the removal of pyridine from wastewater. Activated carbons developed from agricultural waste materials were characterized and utilized for the removal of pyridine from wastewater. Systematic studies on pyridine adsorption equilibrium and kinetics by low cost activated carbons were carried out. Adsorption studies were carried out at different temperatures, particle size, pH and adsorbent doses. Both Langmuir and Freundlich models fitted the adsorption data quite reasonably. The results indicate that the Langmuir adsorption isotherm model fits the data better as compared to the Freundlich adsorption isotherm model. Various mechanisms were established for pyridine adsorption on developed adsorbents. Further, the data are better correlated with non-linear form as compared to the linear one. The kinetic studies were conducted to delineate the effect of temperature, initial adsorbate concentration, particle size of the adsorbent and solid to liquid ratio. The adsorption of pyridine follows the first order rate kinetics. On the basis of these studies, various parameters such as effective diffusion coefficient, activation energy and entropy of activation were evaluated to establish the mechanisms. It is concluded that the adsorption occurs through a particle diffusion mechanism at temperatures 10 and 25 °C while at 40 °C it occurs through film diffusion mechanism. Similarly at concentrations 25 and 50 mg/l the adsorption is particle diffusion controlled while at⩽50 mg/l it is film diffusion controlled.     

Removal of Pb(II) from aqueous solution by adsorption using activated tea waste

A basic investigation on the removal of Pb(II) ions from aqueous solutions by using activated tea waste was conducted in batch conditions. An inexpensive and effective adsorbent was developed from waste tea leaves for the uptake of Pb(II) from aqueous solution. The influence of different experimental parameters—shaking time, particle size, adsorbent dose, initial pH, temperature, etc.—on lead uptake was evaluated. Lead is adsorbed by the developed adsorbent up to maximum of 99.7%. The initial Pb(II) concentrations were 5, 10, 15 and 20 mg/l in the experiment. The adsorption was found to be exothermic in nature. The Langmuir, Freundlich and Tempkin isotherm models were tried to represent the equilibrium data of Pb(II) adsorption. The adsorption data was fitted very well to the Langmuir isotherm model in the studied concentration range of Pb(II) adsorption. Isotherms have been used to determine thermodynamic parameters of the process: free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°). Column experiments were performed to study the practical applicability of the system. The kinetics and the factors controlling the adsorption process were also discussed. Activated tea waste is a better adsorbent compared to other adsorbents available in literature.     

改性泥炭对水溶液中铬的去除

为克服泥炭利用过程中存在的一些问题，对原泥炭进行了改性处理，并将改性后的泥炭与树脂结合以增强改性泥炭的机械强度。通过静态试验方法研究了改性泥炭对来自水溶液中的铬离子的吸附特性。结果表明：改性泥炭对水溶液中的铬的吸附等温过程符合Freundlich吸附等温方程，     

Removal of perchlorate from aqueous solution using protonated cross-linked chitosan

Protonated cross-linked chitosan was used to remove perchlorate from aqueous solution. Adsorption isotherms, the effects of pH and co-existing anions on the adsorption process, proper actual contact time in the adsorption column and the regeneration ability of the adsorbent were investigated. The equilibrium data fitted well with Langmuir and Freundlich isotherm models, and the maximum monolayer adsorption capacity was 45.455 mg g^?1. To balance the protonated degree of the amino groups and the effect of the ion competing on adsorption capacity, the optimal pH value was determined to be about 4.0. Column adsorption results indicated that the proper actual contact time was 8.1 min and the effluent perchlorate could be steadily kept below 24.5 μg L^?1 up to about 95 bed volumes with the influent perchlorate of 10 mg L^?1. The presence of other anions weakened the perchlorate adsorption, especially the high valence anion such as sulfate. The adsorbents could be well regenerated by sodium hydroxide solution with pH 12 and reused at least for 15 cycles. Electrostatic attraction as well as physical force was the main driving force for perchlorate adsorption.     

Removal of pyridine derivatives from aqueous solution by activated carbons developed from agricultural waste materials

The paper investigates the ability of activated carbons developed from coconut shell to adsorb α-picoline, β-picoline, and γ-picolin from aqueous solution. The developed carbons are designated as SAC (activated carbon derived from coconut shells with out any treatment) and ATSAC (activated carbon derived from acid treated coconut shells). The carbons were, characterized and utilized for the sorption of α-picoline, β-picoline, and γ-picoline at different temperatures, particle size, pH and solid to liquid ratio. All the studies were performed by batch method to determine various equilibrium and kinetic parameters. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best report the equilibrium isotherm data. The adsorption of α-, β-, and γ-picoline followed the pseudo-second order rate kinetics. On the basis of kinetic studies, various rate and thermodynamic parameters such as effective diffusion coefficients, activation energy and activation entropy were evaluated. It was concluded that in majority of cases, the adsorption is controlled by particle diffusion at temperatures 10° and 25 °C while at 40 °C it is controlled by film diffusion mechanism. Similarly at concentrations 25 and 50 mg/l the adsorption was governed by particle diffusion in most of the cases while at >50 mg/l it was film diffusion controlled. The overall capacity of ATSAC was higher than SAC. The sorption capacity of γ-picoline was found more followed by β-picoline and α-picoline.     

Removal of iopromide from an aqueous solution using dielectric barrier discharge

BACKGROUND: Both ionic and nonionic ICM are recalcitrant to ozone and traditional waste water treatment plants. In this study, the efficiency of one kind of ICM‐iopromide (IOPr) removal from an aqueous solution using a dielectric barrier discharge (DBD) method was investigated. RESULTS: An energy density of 1.5E05 J L^?1 resulted in the most significant removal (98.8%) of IOPr. At this energy density, no decrease in total organic carbon (TOC) was observed. Based on the IR spectra, degradation of the IOPr molecule involved hydroxylation, carbonylation and deiodination. BOD₅/COD measurements indicated that the biodegradability of IOPr increased significantly as a result of DBD treatment. The byproducts of IOPr after DBD treatment were more polar and easily adsorbed and biodegraded by the activated sludge. The removal of IOPr from the solution followed first‐order kinetics, with Ks of 0.10 min^?1, 0.11 min^?1, 0.44 min^?1 and 0.15 min^?1 corresponding to energy densities of 1E + 05 J L^?1, 1.3E + 05 J L^?1, 1.5E + 05 J L^?1 and 1.8E + 05 J L^?1, respectively. The kinetics of the deiodination reactions were more complex due to subsequent iodide oxidation. CONCLUSION: DBD is very effective as a pretreatment or advanced treatment method for increasing the recalcitrant chemical's biodegradability and making subsequent biological treatment more efficient. © 2012 Society of Chemical Industry     

Removal of ciprofloxacin from aqueous solution using wheat bran as adsorbent

Current study describes sorption of antibiotic drug (ciprofloxacin) by using nontoxic and biocompatible carrier, i.e., wheat bran (WB). For sorption study, various parameters were optimized and Freundlich, Dubinin–Radushkevich, Langmuir, and Temkin isotherm models were applied to demonstrate the mechanism of sorption, while kinetics study for sorption was evaluated using diffusion models, pseudo-first-order kinetic (Langergren) and pseudo-second-order (Ho and McKay) kinetic models. In addition, thermodynamics study was also carried out. However, sorption of ciprofloxacin was pH depended and it showed 75% drug release in alkaline medium (at pH = 1.5) indicating the good release ability of WB for ciprofloxacin.     

Removal of Neutral Red from aqueous solution by using modified hectorite

The object of this work was to study the modified hectorite as effective adsorbent for Neutral Red (NR) from aqueous solution. The adsorbent capacity of modified hectorite was discussed. The effects of surfactant content, adsorbent content, pH and adsorption temperature on the sorption of NR on modified hectorite were studied. Experimental results showed that the equilibrium adsorption data fitted well with Langmuir isotherm and the adsorption capacity was 393.70 mg/g for the modified cetylpyridinium bromide hectorite (CPB-Hect). Kinetic studies showed that the dynamical data fitted well with the pseudo-second-order kinetic model. For thermodynamic studies, parameters such as the Gibbs free energy (ΔG⁰), the enthalpy (ΔH⁰) and the entropy (ΔS⁰) indicated that the adsorption process was spontaneous and endothermic in nature.     

Removal of tannic acid from aqueous solution by magnetic carbohydrate natural polymer

Adsorptive removal of tannic acid (TA) form aqueous solution by synthesized magnetic lignocellulosic adsorbent was investigated. SEM, EDAX, and FTIR analysis were performed to characterize the magnetic saw dust (MSD). The effect of various operational parameters such as contact time, concentration and solution pH etc were studied. The optimum adsorption of TA was observed at pH 4. Results revealed that the Temkin isotherm model fitted well to the adsorption equilibrium data and obeyed the pseudo-second order kinetics model. The values of free energy change and activation energy suggested that physical forces were involved in the adsorption of TA onto MSD.     

Ultrafiltration: a means for decolorization of cane sugar solution

Membrane ultrafiltration was used for clarification as well as for decolorization of raw brown sugar obtained from the Indian sugar industry. Experimental results were obtained using sugar solutions of 28 and 46°Brix and mineral membranes of 20 nm, 5 and 1 kDa molecular weight cut-off (MWCO) on an industrial size pilot plant under different operating conditions. It was found that, even with the membrane of MWCO of 1 kDa, the maximum color removal was limited to 58.67% and steady-state permeate flux was only 29 1/h m² for the 46°Brix sugar solution. Empirical relationships between membrane performance (for decolorization and clarification) and membrane pore diameter were obtained from the experimental results. In order to obtain very high quality white crystalline sugar, further processing with adsorbents or use of an ion-exchange technique is required.     

Removal of methyl violet from aqueous solution using a stevensite-rich clay from Morocco

An inexpensive and easily available Moroccan natural clay, called locally Ghassoul, was employed for adsorption of methyl violet, a cationic dye, in aqueous solution. The experiments were carried out in a batch system to optimize various experimental parameters such as pH, initial dye concentration, contact time, temperature and ionic strength. The experimental data can be well represented by Langmuir and Freundlich models. The Langmuir monolayer adsorption capacity was estimated as 625 mg/g at 298. Kinetic analyses showed that the adsorption rates were more accurately represented by a pseudo second-order model. Intraparticle diffusion process was identified as the main mechanism controlling the rate of the dye sorption. In addition, various thermodynamic activation parameters, such as Gibbs free energy, enthalpy, entropy and the activation energy were calculated. The adsorption process was found to be a spontaneous and endothermic process. The obtained results confirmed the applicability of this clay as an efficient and economical adsorbent for cationic dyes from contaminated water.     

Removal of strontium ions from aqueous solution using hybrid membranes: Kinetics and thermodynamics

The removal of radionuclide from radioactive wastewater has captured much attention. Strontium-90 is one of the major radionuclides. To develop a new type of adsorbents to remove strontium ions from the radioactive wastewater, in this study, novel hybrid membranes were prepared and characterized. The adsorption kinetics, thermodynamic parameters of ΔG, ΔH and ΔS, as well as surface SEM and EDS images were used to investigate the removal of strontium ions from stimulated radioactive wastewater using the previously prepared hybrid membranes as efficient adsorbents. The study of kinetic model confirmed that the adsorption of strontium ions on these hybrid membranes followed the Lagergren pseudo-second order model. Moreover, it was proved that the adsorption of strontium ions on these samples was solely controlled by intraparticle diffusion. The negative values of ΔG and the positive values of ΔH indicated that the adsorption of strontium ions on samples A-D is a spontaneous and endothermic process in nature. Furthermore, surface SEM and DES images give significant evidence to confirm the existence of strontiumions on the surface of the adsorbed samples. These findings demonstrate that these hybrid membranes are promising adsorbents for the removal of strontium ions from aqueous solution and can be potentially applied in the adsorptive separation of radionuclides from the radioactive wastewater.     

Removal of cadmium(II) from aqueous solution by agricultural waste cashew nut shell

Cashew nut shell (CNS) is a low cost adsorbent that has been used for the removal of cadmium(II) from an aqueous solution. The effects of various parameters such as solution pH, CNS concentration, contact time, initial cadmium(II) concentration and temperature were examined. The CNS was effective for the quantitative removal of cadmium(II) ions in acidic conditions and equilibrium was achieved in 30 min. The experimental data were analyzed by two-parameter (Langmuir, Freundlich, Temkin and Dubinin-Radushkevich) and three-parameter models (Redlich- Peterson, Koble-Corrigan, Toth and Sips) by nonlinear regression analysis. The characteristic parameters for each isotherms and related correlation coefficients have been determined by using MATLAB 7.1. Thermodynamic parameters such as ??G ^o , ??H ^o and ??S ^o have also been evaluated, and it was found that the sorption process was feasible, spontaneous and exothermic. Pseudo-first-order, pseudo-second-order, Elovich kinetic and intraparticle diffusion models were selected to follow the adsorption process. The results of the kinetic study show that the adsorption of cadmium(II) could be described by the pseudo-second order equation, suggesting that the adsorption process is presumably chemisorption. A single-stage batch adsorber was designed for different adsorbent dose-to-effluent volume ratios using the Freundlich equation. The results indicate that the cashew nut shell could be used to effectively adsorb cadmium(II) from an aqueous solution.     

Removal of arsenic from aqueous solution using polyaniline/rice husk nanocomposite

The present study deals with the adsorption of arsenic ions from aqueous solution on polyaniline/rice husk (PAn/RH) nanocomposite. Batch studies were performed to evaluate the influence of various experimental parameters like pH, adsorbent dosage, contact time and the effect of temperature. Optimum conditions for arsenic removal were found to be pH 10, adsorbent dosage of 10 g/L and equilibrium time 30 minutes. Adsorption of arsenic followed pseudo-second-order kinetics. The equilibrium adsorption isotherm was better described by Freundlich adsorption isotherm model. The adsorption capacity (q _max ) of PAn/RH for arsenic ions in terms of monolayer adsorption was 34.48 mg/g. The change of entropy (ΔS⁰) and enthalpy (ΔH⁰) was estimated at −0.066 kJ/(mol K) and −22.49 kJ/mol, respectively. The negative value of the Gibbs free energy (ΔG⁰) indicates feasible and spontaneous adsorption of arsenic on PAn/RH.     

Removal of zinc ions from aqueous solution using a cation exchange resin

The present study is concerned with the mass transfer and kinetics study of zinc ions removal from aqueous solution using a cation exchange resin packed in a rotating cylindrical basket reactor. The effect of various experimental parameters on the rate of zinc ion removal, such as initial zinc ion concentration, packed bed rotation speed and temperature has been investigated. In addition to find a suitable equilibrium isotherm and kinetic model for the zinc ion removal in a batch reactor. The experimental isotherm data were analyzed using the Langmuir, Freundlich and D–R equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analyzed using four sorption kinetic models, pseudo-first and second-order equations, the Elovich and the intraparticle diffusion model equation, to determine the best fit equation for the biosorption of zinc ions onto purolite C-100 MH resin. Results show that the Elovich equation provides the best correlation for the biosorption process.     

Removal of Diazinon from aqueous solution by electrocoagulation process using aluminum electrodes

Electrocoagulation (EC) is an electrochemical method to treat polluted wastewaters and aqueous solutions. In this paper, the removal of Diazinon was studied by EC on aluminum electrode. The effect of several parameters such as initial concentration of Diazinon, current density, solution conductivity, effect of pH, and electrolysis time were investigated on EC performance. The obtained results showed that the removal efficiency of EC depends on the current density, initial concentration of Diazinon and electrolysis time. The optimum pH is 3 and also the solution conductivity has no significant effect on removal efficiency.     

Removal of basic and acid dyes from aqueous solutions by a waste containing boron impurity

In this study, batch experiments were carried out for the sorption of basic blue 41 (BB 41), and acid blue 225 (AB 225) onto boron waste (BW) from boron enrichment plant. The operating variables studied are the initial dye concentration, contact time, solution pH, and adsorbent dosage. The experimental equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that the adsorption behavior of AB 225 and BB 41 could be described well reasonably by Langmuir and Temkin isotherms, respectively. Kinetics studies indicated that the adsorption of both dyes follow pseudo-second-order kinetics. The sorption of basic dye increased at high pH values, whereas the opposite was true for acidic dye. The results indicate that BW could be employed as low-cost alternatives to the commercially available adsorbents in wastewater treatment for the removal of acid and basic dyes.     

Removal of diclofenac from aqueous solution with multi-walled carbon nanotubes modified by nitric acid☆

Modified multi-walled carbon nanotubes (MWCNTs) were used as adsorbents for removal of diclofenac. The re-action conditions were examined. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were applied to determine appropriate equilibrium expression. The results show that the experimental data fit the Freundlich equation well. Thermodynamic parameters show that the adsorption process is spontaneous and exothermic. The kinetic study indicates that the adsorption of diclofenac can be well described with the pseudo-second-order kinetic model and the process is controlled by multiple steps.     

MIEX对水中DBP的去除效果及机理分析

邻苯二甲酸二丁酯(DBP)是水源水中常见的内分泌干扰物。以新型的饮用水处理材料离子交换树脂(MIEX)为吸附剂,以DBP为目标污染物,从动力学、吸附等温线、电荷密度测定、红外光谱表征、X射线光电子能谱以及共存组分影响等方面分析了MIEX去除DBP的效果和机理。MIEX去除DBP的过程仅需20 min即达到平衡,可用准二级动力学描述,中性溶液中DBP的饱和吸附量为0.944 mg·g^-1。中性条件下DBP带电量仅为2.7×10^-3 mmol·mmol^-1,MIEX与DBP间的作用并非离子交换,而是以DBP分子与MIEX基材间的疏水作用以及氢键作用为主。高浓度 和 不会对DBP的去除效果产生影响;高浓度的腐殖酸(HA)轻微抑制DBP的去除,但微量DBP并不会影响MIEX对HA的去除效果。因此,MIEX作为能高效去除水中天然有机物的新型材料,也可用于去除其中微量的DBP,适用于饮用水复合污染的处理。