Investigation of adsorption of lead,mercury and nickel from aqueous solutions onto carbon aerogel

Recently a new form of activated carbon has appeared: carbon aerogel (CA). Its use for the removal of inorganic (and especially metal ions) has not been studied. In the present study, the adsorption of three metal ions, Hg(II), Pb(II) and Ni(II), onto carbon aerogel has been investigated. Batch experiments were carried out to assess adsorption equilibria and kinetic behaviour of heavy metal ions by varying parameters such as agitation time, metal ions' concentration, adsorbent dose and pH. They facilitated the computation of kinetic parameters and maximum metal ion adsorption capacities. Increasing the initial solution pH (2–10) and carbon concentration (50–500 mg per 50 cm³) increases the removal of all three metal ions. A decrease of equilibrium pH with an increase of metal ion concentration led us to propose an adsorption mechanism by ion exchange between metal cations and H⁺ at the carbon aerogel surface. Carboxylic groups are especially involved in this adsorption mechanism. Langmuir and Freundlich isotherm models were used to analyse the experimental data of carbon aerogel. The thermodynamics of the metal adsorption was also investigated for the practical implementation of the adsorbent. The sorption showed significant increase with increase of temperature. Kinetics models describing the adsorption of Hg(II), Pb(II) and Ni(II) ions onto carbon aerogel have been compared. Kinetics models evaluated include the pseudo‐first order and second order model. The parameters of the adsorption rate constants have been determined and the effectiveness of each model assessed. The result obtained showed that the pseudo‐second order kinetic model correlated well with the experimental data and better than the pseudo‐first order model examined in the study. Mass transfer coefficients obtained can be useful in designing wastewater treatment systems or in the development of environmental technologies. Copyright © 2005 Society of Chemical Industry     

Adsorption of Cd(II) ions at the hydroxyapatite/electrolyte solution interface

The study of the Cd(II) ions adsorption at the hydroxyapatite/electrolyte solution interface and the changes of the electrical double layer (EDL) structure in this system are presented. The adsorption of Cd(II) ions was calculated from the loss of their concentration from the solution using the radioisotope method. The adsorption was studied in the range of the initial concentration from 0.000001 to 0.001mol/dm³ and as the function of pH. The results of measurements of Cd(II) ions adsorption kinetics on hydroxyapatite were fitted using the pseudo-first, pseudo-second, and multiexponential modes to check which model describes this process in the best way. In addition, the main properties of the EDL, i.e., surface charge density and zeta potential were determined by the potentiometeric titration and electrophoresis measurements, respectively. The adsorption of Cd(II) ions at hydroxyapatite contributed to the increase of the zeta potential and also to the change of the double electrical layer structure.     

Porous dye affinity beads for nickel adsorption from aqueous solutions: A kinetic study

We investigated a new adsorbent system, Reactive Red 120 attached poly(2‐hydroxyethyl methacrylate ethylene dimethacrylate) [poly(HEMA–EDMA)] beads, for the removal of Ni²⁺ ions from aqueous solutions. Poly(HEMA–EDMA) beads were prepared by the modified suspension copolymerization of 2‐hydroxyethyl methacrylate and ethylene dimethacrylate. Reactive Red 120 molecules were covalently attached to the beads. The beads (150–250 μm), having a swelling ratio of 55% and carrying 25.5 μmol of Reactive Red 120/g of polymer, were used in the removal of Ni²⁺ ions. The adsorption rate and capacity of the Reactive Red 120 attached poly(HEMA–EDMA) beads for Ni²⁺ ions was investigated in aqueous media containing different amounts of Ni²⁺ ions (5–35 mg/L) and having different pH values (2.0–7.0). Very high adsorption rates were observed at the beginning, and adsorption equilibria were then gradually achieved in about 60 min. The maximum adsorption of Ni²⁺ ions onto the Reactive Red 120 attached poly(HEMA–EDMA) beads was 2.83 mg/g at pH 6.0. The nonspecific adsorption of Ni²⁺ ions onto poly(HEMA–EDMA) beads was negligible (0.1 mg/g). The desorption of Ni²⁺ ions was studied with 0.1M HNO₃. High desorption ratios (>90%) were achieved. The intraparticle diffusion rate constants at various temperatures were calculated as k_20°C = 0.565 mg/g min^0.5, k_30°C = 0.560 mg/g min^0.5, and k_40°C = 0.385 mg/g min^0.5. Adsorption–desorption cycles showed the feasibility of repeated use of this novel adsorbent system. The equilibrium data fitted very well both Langmuir and Freundlich adsorption models. The pseudo‐first‐order kinetic model was used to describe the kinetic data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:5056–5065, 2006     

Adsorption of Cu(II) from aqueous solutions by tannins immobilized on collagen

Novel adsorbents were prepared by immobilizing tannins on collagen fibre matrices. Their adsorption properties, including adsorption equilibrium, adsorption kinetics, and column adsorption kinetics to Cu(II) were investigated. Immobilized Myrica rubra tannin and black wattle tannin exhibited significantly higher adsorption capacity than larch tannin and the adsorption isotherms of these three immobilized tannins can be described by the Freundlich model. Detailed adsorption studies of immobilized black wattle tannin to Cu(II) indicated that temperature had little effect on the adsorption isotherms whereas the effect of pH was significant. Adsorption rate data fitted well to a pseudo‐second‐order rate model, and the adsorption capacity calculated by this model was consistent with the result of actual measurement at relatively higher adsorption temperatures. Immobilized black wattle tannin also had excellent column adsorption kinetic properties and high binding capacity. The adsorptivity of the column was stable even after repeated adsorption–desorption cycles. Copyright © 2004 Society of Chemical Industry     

Kinetics of zirconium ions adsorption on activated charcoal from aqueous solutions

The batch kinetics of adsorption of the zirconium ions from aqueous solutions on activated charcoal has been investigated over a wide range of concentration of zirconium ions (1.0–5.0 g/l) and temperatures (10–50°C). The adsorption process of zirconium ions proceeds via two stages; the first stage is rather fast, followed by a much slower one. The Bangham equation was used to study the kinetics of the zirconium ions' adsorption on activated charcoal. It is observed that the diffusion of zirconium ions into the pores of the activated charcoal controls the kinetics of the adsorption process. Moreover, zirconium ion adsorption obeys the Freundlich and Langmuir isotherms in the concentration range studied. The adsorption equilibrium constant (k_c) values for zirconium ions adsorption on activated charcoal have also been calculated at different temperatures. Various thermodynamic quantities, ΔG, ΔH, and ΔS were computed from k_c values. The results showed that the adsorption of zirconium ions on activated charcoal is an endothermic process.     

Adsorption of cadmium ions from aqueous solutions by activated carbon with oxygen-containing functional groups

The adsorption of aqueous cadmium ions (Cd(II)) have been investigated for modified activated carbon (AC-T) with oxygen-containing functional groups. The oxygen-containing groups of AC-T play an important role in Cd(II) ion adsorption onto AC-T. The modified activated carbon is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results of batch experiments indicate that the maximal adsorption could be achieved over the broad pH range of 4.5 to 6.5. Adsorption isotherms and kinetic study suggest that the sorption of Cd(II) onto AC-T produces monolayer coverage and that adsorption is controlled by chemical adsorption. And the adsorbent has a good reusability. According to the FT-IR and XPS analyses, electrostatic attraction and cation exchange between Cd(II) and oxygen-containing functional groups on AC-T are dominant mechanisms for Cd(II) adsorption.     

Effective adsorption of ciprofloxacin hydrochloride from aqueous solutions using metal-organic framework

ABSTRACT

Metal organic frameworks (MOFs) have become material of special attention due to their high porosity and large surface area. Adsorptive removal of ciprofloxacin hydrochloride using MOFs from aqueous waste and real wastewater has been studied in this work. The MOF-5 synthesized showed higher adsorption capacity as compared to activated charcoal. The adsorption satisfies the pseudo-second-order kinetic model and adsorption isotherm is very well explained by the Freundlich and the Sips isotherm. The adsorption mechanism may be explained by the electrostatic interactions of the pharmaceutical compounds and the MOF-5 surface. Finally, it can be concluded that MOF-5 has shown a great potential for their application in wastewater treatment technology development.     

Acid treatment of south Tunisian palygorskite: Removal of Cd(II) from aqueous and phosphoric acid solutions

The object of this work is to study the modifications of Tunisian palygorskite upon HCl treatment and to investigate the ability of natural and acid treated palygorskite to adsorb heavy metal ions. Chemical analysis, X ray diffraction, infrared spectra, MAS-NMR methods, BET surface and surface charge of HCl treated palygorskite have been reported. It was established that acid leaching at reflux temperature resulted in an increase in the amount of Mg, Fe and Al extracted and in surface area from 59.7 to 437 m² g^− 1 for 2 M HCl samples and from 59.7 to 360 m² g^− 1 for 4 M HCl samples, due to a dissolution of the octahedral sheet and the creation of mesoporosity. ²⁹Si-MAS-NMR studies yield information on changes occurring in the structure of the mineral. During acid treatment the clay structure is progressively transformed into amorphous silica (essentially for samples treated by HCl 4 M for 10 h and HCl 2 M for 35 h).Natural palygorskite and the activated samples were applied as adsorbents for the removal of Cd(II) from aqueous solutions. The effects of various experimental parameters were investigated. The adsorption isotherms of activated palygorskites for Cd(II) could be described by the Freundlich model. The acid activated sample showed a higher adsorption capacity for Cd(II) than the natural palygorskite. The retention of Cd(II) ions by palygorskite occurs dominantly by specific adsorption. A different behaviour was observed in the phosphoric acid medium. Despite increases in the surface areas upon acid activation, improvements in the adsorption were not observed, as a result of the decreasing number of negative surface sites, as main centers for specific adsorption.     

Behaviour and mechanism of Zn(II) adsorption on Chinese loess at dilute slurry concentrations

BACKGROUND: Zn(II) is commonly present in mining drainage in developing countries. Since loess is abundant and always located near mining sites in China, it would be useful to investigate the possibility and efficiency of using loess to remove Zn(II) from aqueous solution. RESULTS: The Zn(II) adsorption capacity of Chinese loess was determined as 215.9 mg g^?1. The adsorption followed pseudo‐second‐order kinetics and took place mainly by surface diffusion. Generally, higher initial pH and solute concentration resulted in higher % Zn(II) removal, while higher temperature and slurry concentration led to lower % Zn(II) removal. A thermodynamic study revealed that the adsorption process was exothermic, with the predicted enthalpy change ranging from ?20.87 to ?4.06 kJ mol^?1. With the assistance of X‐ray photoelectron spectroscopy and X‐ray diffraction, the high adsorption capacity was ascribed to the growth of micro‐organisms and mineral constituents such as kaolinite and goethite. CONCLUSION: Chinese loess proved effective for Zn(II) adsorption in this study. The optimal adsorption conditions included pH > 3.0, temperature ?15 °C and contact time ≈ 400 min. As an abundant natural soil in arid areas with very low population density, it would be appropriate to develop this material into a wastewater‐purifying agent. Copyright © 2008 Society of Chemical Industry     

Adsorption of trivalent chromium from aqueous solutions onto activated carbon

The adsorption of chromium (III) onto activated carbon was investigated as a possible alternative method for its removal from aqueous solutions. The adsorption data were obtained in a batch adsorber and fitted the Langmuir adsorption isotherm well. The effect of pH on the adsorption isotherm was investigated at pH values of 2, 4, 5 and 6. It was found that at pH values below 2 the Cr(III) was not adsorbed and at pH values above 6.4 the Cr(III) was precipitated as Cr(OH)₃. Maximum adsorption occurred at pH 5. The pH plays a very important role in the adsorption of Cr(III) since Cr(III) can form different complexes in aqueous solutions. The adsorption capacity was increased by about 20% as the temperature was raised from 25 to 40°C. It was concluded that Cr(III) is adsorbed to an appreciable extent on activated carbon and that the adsorption is highly dependent upon pH.     

Prediction of mixed-gas adsorption equilibria from pure component adsorption isotherms

Using only a single binary interaction parameter per adsorbate-adsorbate pair, the adsorption nonrandom two-liquid theory successfully correlates binary gas adsorption experimental data and predicts multicomponent gas adsorption equilibria. This work estimates the binary adsorbate–adsorbate interaction parameters from pure component isotherms and shows very promising agreement with the binary interaction parameters identified from regression of binary gas adsorption data. The results support the feasibility to predict binary and multicomponent gas adsorption equilibria from pure component isotherms for various adsorbents including silica gel, activated carbon, zeolites, and metal–organic frameworks.     

Removal of Zinc(II) from Aqueous Solutions using an Eco-Friendly Biosorbent Originating from the Winery Industry

The aim of this work was to evaluate the morphological and chemical characteristics of Isabel grape bagasse (Vitis labrusca × Vitis vinifera) through instrumental techniques, including scanning electron microscopy, Fourier Transform infrared spectroscopy, and ¹³C nuclear magnetic resonance, and to describe the adsorption of zinc(II) from aqueous solutions by this biosorbent. In general, the grape bagasse was constituted mainly of particles with heterogeneous shapes and sizes that were also rich in oxygenated functional groups, especially –OH. With respect to the equilibrium of the adsorption process, the Freundlich isotherm provided the better fit for the experimental data. The rate-controlling step, on the other hand, was better described using a pseudo-second-order kinetic model, and the removal percentage (? 50%) was similar for all tested concentrations. Finally, the thermodynamic data showed that the adsorption occurred via an exothermic process accompanied by a decrease in the randomness at the solid/solution interface.     

甲醇酯化改性花生壳吸附水溶液中铬蓝黑

以花生壳为原料,甲醇为改性剂,制备了酯化改性花生壳吸附剂,并以其吸附水溶液中的铬蓝黑,考察了铬蓝黑的初始质量浓度、吸附时间、吸附剂粒径、温度等因素对改性花生壳吸附铬蓝黑过程的影响。分别采用拟一级和拟二级动力学模型和Langmuir,Freundlich等温式对吸附动力学和等温线进行分析。结果表明:酯化改性花生壳对铬蓝黑的吸附过程符合拟二级动力学方程,吸附平衡符合Freundlich等温方程,吸附焓变ΔH>0,反应吉布斯自由能ΔG<0,表明该吸附过程为自发进行的吸热过程。甲醇酯化改性花生壳对去除水溶液中铬蓝黑效果好,是一种具有发展潜力的吸附剂。     

Intraparticle diffusion of cadmium and zinc ions during adsorption from aqueous solution on activated carbon

The adsorption isotherms of cadmium(II) and zinc(II) onto activated carbons were obtained in a batch adsorber. The concentration decay data were obtained in a rotating basket adsorber and were interpreted by a mathematical model, which takes into account the adsorption rate, external mass transport and intraparticle diffusion. The results showed that the overall rate of adsorption of Cd(II) and Zn(II) was mainly controlled by the intraparticle diffusion which was solely due to pore volume diffusion. The contribution of the external mass transport resistance was negligible. The effective pore volume diffusivities of Cd(II) and Zn(II) were predicted reasonably well using the ionic diffusivity of the metal and the void fraction and tortuosity of activated carbon. Copyright © 2005 Society of Chemical Industry     

Adsorption of lead(II) from aqueous solution by activated carbon prepared from Eichhornia

Activated carbon prepared from Eichhornia was used for the adsorptive removal of Pb(II) from aqueous solution. As the raw material for the preparation of the activated carbon is an aquatic weed, the production of this carbon is expected to be economically feasible. Parameters such as agitation time, metal ion concentration, adsorbent dose and pH were studied. Adsorption equilibrium was reached in 100 min for a solution containing 15 mgdm^?3 and 125 min for solutions containing 20 and 25 mgdm^?3 Pb(II), respectively. Adsorption parameters were determined using both Langmuir and Freundlich isotherm models. The adsorption capacity was 16.61 mgg^?1 at pH 3.0 for particle sizes of 125–180 µm. Pb(II) removal increased as the pH increased from 2 to 4 and remained constant up to pH 10.0. Desorption studies were also carried out with dilute hydrochloric acid to recover both carbon and Pb(II). Quantitative desorption of Pb(II) from carbon indicates that adsorption of metal ion is by ion exchange. © 2002 Society of Chemical Industry     

Acrylamide‐plasma treated electrospun polystyrene nanofibrous adsorbents for cadmium and nickel ions removal from aqueous solutions

The aim of this work was to prepare novel electrospun polystyrene (PS) nanofibrous samples functionalization with acrylamide monomer (AAm) as promising nanoadsorbents by the use of nitrogen gas plasma. To investigate the performance evaluation of the samples for adsorbing cadmium (Cd²⁺) and nickel (Ni²⁺) ions, a series of tests in terms of ATR‐FTIR spectroscopy, FE‐SEM, water contact angle (WCA) measurements and atomic adsorption spectroscopy were carried out. The ATR‐FTIR results showed that nitrogen (N₂) plasma was an efficient tool because of the formation of functionalized AAm‐PS nanofibrous samples by providing amide (?NCO) and amine (?NH?) groups onto their surfaces. The WCA measurements demonstrated that the N₂ plasma‐modified samples in the presence of AAm had a lower contact angle of 42.8º than the other samples. Moreover, FE‐SEM micrpgraph images of AAm‐treated PS nanofibrous samples indicated that approperiate amount of the functional groups onto the samples surfaces were deposited. Afterwards, AAS analysis along with Langmuir and Freundlich's isotherm models revealed that a high adsorption of the ions was occurred at pH 5 in the order Cd²⁺ (10 mg g^?1) > Ni²⁺ (4.9 mg g^?1) by using the nanoadsorbents dosage 1 g L^?1 and the metal ions concentration 25 mg L^?1. In addition, the obtained results exhibited the Cd²⁺ and Ni²⁺ ions removal efficiencies (%R) were increased up to 96% and 94%, respectively with raising the nanoadsorbents dosage. Moreover, the equilibrium adsorption of the ions showed the best fitting by the Freundlich's model. Finally, the desorption of the optimized samples for regenerating them owing to the effective removal of the ions has been confirmed by applying the recyclability test. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42944.     

Studies on the removal of Cobalt(II) from aqueous solutions by adsorption with Ficus benghalensis leaf powder through response surface methodology

Suitability of Ficus benghalensis leaf powder for the adsorptive removal of Cobalt(II) from aqueous solutions is exhaustively studied and is reported in this article. Experimentation based on response surface methodology is conducted to understand the interaction among the variables—metal ion concentration, adsorbent dosage, initial solution pH and temperature that are of significance in the treatment. A 20?mg?L^?1 of Cobalt(II) solution, treated with 25?g?L^?1 of adsorbent at a pH of 5.0 and a temperature of 303?K, yielded 98.73% removal of Cobalt(II). Langmuir isotherm proved to be a better model representation of the equilibrium. Adsorption kinetics is of pseudo second rate form. Maximum sorption capacity of F. benghalensis leaf powder, q_max, is found to be 5.65?mg?g^?1. Adsorption is endothermic and spontaneous in nature. Study on surface morphology is included in the study.     

用DIOSO从水溶液中萃取镉的研究

为探究亚砜类化合物对水中重金属镉的萃取效率和萃取机理，报道了利用二异辛基亚砜(DIOSO)萃取水溶液中镉的情况，实验制备了DIOSO，以其为萃取剂探索其对水溶液中镉的萃取情况，得出最佳萃取条件，在此条件下最高萃取率为99.7%。为达到萃取剂的回收循环利用，实验研究了不同反萃剂对Cd(Ⅱ)的反萃情况，得出利用0.2 mol/L NaOH为反萃剂时能把有机相中的Cd(Ⅱ)全部洗脱出来，反萃率达99.86%。在此基础上，结合光谱和热力学分析，DIOSO对Cd(Ⅱ)的萃取过程可能是离子间发生了缔合作用。DIOSO对水中Cd(Ⅱ)的成功萃取，可以为工业废水污染中Cd(Ⅱ)的处理提供重要理论研究基础。     

废啤酒酵母同步吸附水中Pb2+、Zn2+、Cd2+的研究

利用废啤酒酵母同步吸附处理含Pb2+、Zn2+、Cd2+废水,考察了初始pH、反应时间和初始浓度等因素对去除率的影响,并对吸附动力学进行探讨.结果表明:废啤酒酵母对Pb2+、Zn2+、Cd2+同步吸附去除率大小依次为Pb2+＞Cd2+＞Zn2+;三者之间存在竞争吸附;拟二级动力学方程相关系数R2＞0.99,对Pb2+和在低浓度条件下拟合情况更好,内扩散和液膜扩散联合控制吸附速率.