The sorption of lead, cadmium, copper and zinc ions from aqueous solutions on a raw diatomite from Algeria

The adsorption of Cu(2+), Zn(2+), Cd(2+) and Pb(2+) ions from aqueous solution by Algerian raw diatomite was studied. The influences of different sorption parameters such as contact pH solution, contact time and initial metal ions concentration were studied to optimize the reaction conditions. The metals ions adsorption was strictly pH dependent. The maximum adsorption capacities towards Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were 0.319, 0.311, 0.18 and 0.096 mmol g(-1), respectively. The kinetic data were modelled using the pseudo-first-order and pseudo-second-order kinetic equations. Among the kinetic models studied, the pseudo-second-order equation was the best applicable model to describe the sorption process. Equilibrium isotherm data were analysed using the Langmuir and the Freundlich isotherms; the results showed that the adsorption equilibrium was well described by both model isotherms. The negative value of free energy change ΔG indicates feasible and spontaneous adsorption of four metal ions on raw diatomite. According to these results, the high exchange capacities of different metal ions at high and low concentration levels, and given the low cost of the investigated adsorbent in this work, Algerian diatomite was considered to be an excellent adsorbent.     

Use of sesame stalk biomass for the removal of Ni(II) and Zn(II) from aqueous solutions

In this study an agricultural residue, sesame stalk, was evaluated for the removal of Ni(II) and Zn(II) metal ions from aqueous solutions. Biosorption studies were carried out at different pH, biosorbent dosage, initial metal ion concentrations, contact time, and solution temperature to determine the optimum conditions. The experimental data were modeled by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Langmuir model resulted in the best fit of the biosorption data. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and to evaluate rate constants. The best correlation was provided by the second-order kinetic model. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated for predicting the nature of adsorption. The experimental results showed that sesame stalk can be used as an effective and low-cost biosorbent precursor for the removal of heavy metal ions from aqueous solutions.     

Poly(acrylic acid) modifying bentonite with in-situ polymerization for removing lead ions

In this paper, a new kind of poly(acrylic acid) modified clay adsorbent, the poly(acrylic acid)/bentonite composite (PAA/HB) was prepared by in-situ polymerization, and utilized to remove lead(II) ions from solutions. The maximum adsorption of adsorbent is at pH 5 for metal ions, whereas the adsorption starts at pH 2. The effects of contact time (5-60 min), initial concentration of metal ions (200-1,000 mg/L) and adsorbent dosage (0.04-0.12 g/100 mL) have been reported in this article. The experimental data were investigated by means of kinetic and equilibrium adsorption isotherms. The kinetic data were analyzed by the pseudo-first-order and pseudo-second-order equation. The experimental data fitted the pseudo-second-order kinetic model very well. Langmuir and Freundlich isotherms were tried for the system to better understand the adsorption isotherm process. The maximal adsorption capacity of the lead(II) ions on the PAA/HB, as calculated from the Langmuir model, was 769.2 mg/g. The results in this study indicated that PAA/HB was an attractive candidate for removing lead(II) (99%).     

Removal of C.I. Reactive Red 2 from aqueous solutions by chitin: an insight into kinetics, equilibrium, and thermodynamics

In this study, C.I. Reactive Red 2 (RR2) was removed from aqueous solutions by chitin. Exactly how the RR2 concentration, chitin dosage, pH, and temperature affected adsorption of RR2 by chitin was then determined. After reaction for 120 min, the amount of 10 and 20 mg/L RR2 absorbed onto chitin was 5.7 and 7.5 mg/g, respectively. The adsorption percentage increased from 56 to 94% when the chitin dosage was increased from 1.5 to 2.5 g/L. Experimental results indicated that the pseudo-second-order model best represents adsorption kinetics. Adsorption of RR2 increased as the temperature increased; however, it decreased with an increased pH. Experimental results further demonstrated that the Freundlich model is superior to the Langmuir model in fitting experimental isotherms. The ΔH° and ΔS° were 16.34 kJ/mol and 152.10 J/mol K, respectively. ΔH° suggested that adsorption of RR2 onto chitin was via physisorption.     

Adsorption of Cd(II), Zn(II) by extracellular polymeric substances extracted from waste activated sludge

Adsorption of Cd(II) and Zn(II) ions in single solutions using extracellular polymeric substances (EPS) from activated sludge was investigated. Langmuir and Freundlich models were applied to describe metal adsorption. The results showed that EPS was an effective adsorbent for the zinc and cadmium ions from aqueous solution. The equilibrium metal uptake was increased with increasing the initial concentration of metal ion. Constants calculated from isotherms model showed that the maximum uptake capacity of cadmium was estimated to be 45 mg/g of Cd(II) and 80 mg/g of Zn(II). Both Langmuir and Freundlich isotherms were suitable for describing adsorption of Cd(II) by EPS, while the Langmuir isotherm equation fit the date of Zn(II) adsorption better, indicating that EPS adsorb Cd(II) and Zn(II) by different mechanisms.Analysis of FTIR spectra demonstrated that C-O-C of polysaccharides at 1,150-1,030 cm(-1), group of the amide(I), CH(2) group of the lipids, carboxyl and -OH groups of proteins and polysaccharides were involved in cadmium and zinc binding, of which the -OH groups and the C-O-C group of polysaccharides.     

Adsorption behavior of activated carbon derived from pyrolusite-modified sewage sludge: equilibrium modeling, kinetic and thermodynamic studies

Activated carbon was developed from sewage sludge using pyrolusite as an additive. It was demonstrated that the removal efficiency of two synthetic dyes (Tracid orange GS and Direct fast turquoise blue GL) by the produced adsorbent was up to 97.6%. The activated carbon with pyrolusite addition had 38.2% higher surface area, 43.8% larger micropore and 54.4% larger mesopore production than ordinary sludge-based activated carbons. Equilibrium adsorption isotherms and kinetics were also investigated based on dyes adsorption tests. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption, and the results fitted well to the Langmuir isotherm. The kinetic data have been analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion equation. The experimental data fitted very well with pseudo-second-order kinetic model. Activation energies for the adsorption processes ranged between 8.7 and 19.1 kJ mol 1. Thermodynamic parameters such as standard free energy (deltaG0), standard enthalpy (deltaH0) and standard entropy (deltaS0) were evaluated. The adsorption of these two dyes on the activated carbon was found to be a spontaneous and endothermic process in nature.     

Biosorption of Methylene Blue onto spent corncob substrate: kinetics, equilibrium and thermodynamic studies

This study focuses on the possible use of the spent corncob substrate (SCS), an agricultural waste used after the cultivation of white rot fungus Pleurotus ostreatus, to adsorb Methylene Blue (MB) from aqueous solutions. A batch adsorption study was carried out with variable solution pH, adsorption time, temperature and initial MB concentration. It was found that MB uptake was favorable at pH ranging from 4.0 to 12.0 and the equilibrium adsorption capacity can be reached promptly within about 180 min. The biosorption data were also calculated by the pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic parameters show that the adsorption is a spontaneous and endothermic process. The study highlighted a new pathway to develop potential low-cost biosorbent for the removal of dye pollutants from wastewater.     

Removal of Cu(II) ions from aqueous solutions using N-carboxymethyl chitosan

N-carboxymethyl chitosan (NCMC) was synthesized by reacting chitosan with chloroacetic acid in water under triethylamine (Et(3)N) as catalyst. The chemical structures of NCMC were characterized by Fourier transform infrared (FT-IR) and hydrogen-1 nuclear magnetic resonance ((1)H-NMR) spectroscopy and confirmed that carboxymethylation occurred on the amino groups. Samples of NCMC were used for removal of Cu(II) from aqueous solution. The effects of degree of substitution of NCMC, initial pH value and adsorption kinetics on the adsorption were studied. Adsorption experiments showed that NCMC has a high adsorption speed and high adsorption capacity for remove Cu(II) from aqueous solution. The adsorption kinetics data were best fitted with the pseudo-second-order model. The experimental equilibrium data of Cu(II) on the NCMC were both fitted to the Langmuir model and Freundlich model, which revealed that the maximum capacity for monolayer saturation was 147.93 mg/g.     

Comparison of surface functional groups and metal uptake efficiency of rice husk harvested from different climatic zones

Rice husk (RH) is a very effective natural adsorbent for fast removal of heavy metal cations from water solutions. Application of RH for removal of some heavy metal ions, such as Ni, Zn, Mn, Co, Cu, Pb and Cd from water solutions has been studied and different maximum adsorption capacities and a variety of optimized conditions were reported in the literature. In this work, the efficiency of RH harvested from different climatic regions was studied. For this proposal, different RH samples were collected from three different climatic regions of Iran (nominated as RH1 to RH3); their removal efficiencies of heavy metal cations of Ni(2+), Cu(2+) and Cd(2+) were investigated and compared. The adsorption data at optimum conditions could be assessed well by both Langmuir and Freundlich models. Statistical analysis of the results of adsorption isotherms showed that different RH samples have different efficiencies in uptake of these heavy metal ions. The RH samples were characterized using Fourier transform infrared spectroscopy and Boehm titration, which indicated that amounts of functional groups differed between RHs that are grown in different climatic conditions.     

Removal of Cr(VI) by magnetite nanoparticle.

Magnetite nanoparticles were synthesized by sol-gel method. The highly crystalline nature of the magnetite structure with diameter of around 10 nm was characterized with transmission electron microscopy and X-ray diffractometry. The surface area was determined to be 198 m2/g. Batch experiments were carried out to determine the adsorption kinetics and mechanism of Cr(VI) by these magnetite nanoparticles. The Cr(VI) uptake was mainly governed by physico-chemical adsorption. The adsorption process was found to be pH and temperature dependent. The adsorption data fit well with the Freundlich isotherm equation. The Freundlich constants were calculated at different temperatures. The adsorption capacity increased with rising temperature. Preliminary results indicate that magnetite nanoparticles may be used as an adsorbent for removal of Cr(VI) from wastewater.     

铝污泥吸附水中磷的影响因素及响应面法优化

为提高铝污泥的利用效率,将其更好地应用于富营养化水体的修复之中,以给水厂脱水铝污泥为吸附材料对水中的磷进行吸附,考察铝污泥投加量、铝污泥颗粒粒径、体系pH、水样磷浓度对吸附效果的影响。拟合了等温吸附方程,并借助响应面分析中的BBD(Box-Behnken Design)模型确定吸附时间、pH和铝污泥投加量这3种因素对吸附反应影响的显著性及交互作用的强弱,同时利用此模型对实验条件进行优化。结果表明:①上述4种因素均对吸附过程有所影响,Langmuir等温吸附方程拟合效果较好,铝污泥对磷的理论饱和吸附量为1.487 mg/g(温度298 K)。②铝污泥投加量对吸附的影响最为显著,pH和反应时间产生的交互作用最强。③当水体中磷浓度为10 mg/L时,其最佳工艺条件为铝污泥投加量12 g/L、pH=4.5及反应时间48 h,最大去除率为92.38%。     

Enhancement of removal efficiency of heavy metal ions by polyaniline deposition on electrospun polyacrylonitrile membranes

This paper describes the preparation of a membrane of polyacrylonitrile(PAN) and its corresponding membrane coated with polyaniline(PANI) for the adsorption of heavy metal ions.Scanning electron microscopy micrographs revealed that all the membranes exhibited nanofibrous morphology.The prepared membranes were characterized by Fourier transform infrared spectroscopy(FTIR).The prepared membranes were used as an adsorbent for hazardous heavy metal ions Pb~(2+) and Cr_2 O_7~(2-).The adsorption capacity and the removal efficiency of the membranes were examined as function of the initial adsorbate concentration and pH of the medium.Coated membranes with PANI showed better adsorption performance and their direct current(DC) conductivities were correlated to heavy metal ion concentrations.Adsorption isotherms were also performed,and the adsorption process was tested according to the Langmuir and Freundlich models.The regeneration and reuse of the prepared membranes to re-adsorb heavy metal ions were also investigated.The enhancement in adsorption performance and reusability of PANI-coated membranes in comparison with non-coated ones is fully discussed.The results show that the maximum adsorption capacities of lead and chromate ions on the PANI-coated membranes are 290.12 and 1 202.53 mg/g,respectively.     

纳米铁/活性炭新型材料的制备及其对铜离子的吸附性能研究

以活性炭为载体,采用沉淀法制备纳米铁/活性炭新型材料,对活性炭的结构变化进行BET和TEM表征分析,研究纳米铁负载前后活性炭对水中铜离子的吸附能力以及p H值、起始浓度、吸附时间等因素对吸附性能的影响,同时考察其再生性能。结果表明:纳米铁成功负载于活性炭上,随着p H值的增加,吸附容量逐渐增大,当p H=6时,纳米铁/活性炭的最大吸附量为18.73 mg/g,与活性炭相比提高了150%。新型材料对铜离子的吸附过程符合Langmuir和Freundlich吸附模型,对铜离子的吸附量随时间变化的规律符合准二级动力学模型,由于负载的纳米铁阻碍了铜离子向材料表面扩散,其吸附速率仅为0.002 g/(mg·min),与活性炭相比下降了60%左右。新型材料再生效率高,具有较好的应用前景。     

Modification of granular activated carbon using low molecular weight polymer for enhanced removal of Cu(2+) from aqueous solution.

Palm shell activated carbon was modified via surface impregnation with polyethyleneimine (PEI) to enhance removal of Cu(2+) from aqueous solution in this study. The effect of PEI modification on batch adsorption of Cu(2+) as well as the equilibrium behavior of adsorption of metal ions on activated carbon were investigated. PEI modification clearly increased the Cu(2+) adsorption capacities by 68% and 75.86% for initial solution pH of 3 and 5 respectively. The adsorption data of Cu(2+) on both virgin and PEI-modified AC for both initial solution pH of 3 and 5 fitted the Langmuir and Redlich-Peterson isotherms considerably better than the Freundlich isotherm.     

Biosorption of Ni(Ⅱ) ions from aqueous solution using modified Aloe barbadensis Miller leaf powder

This study aimed to investigate the biosorption potential of Na_2 CO_3-modified Aloe barbadensis Miller(Aloe vera) leaf(MABL) powder for removal of Ni(II) ions from a synthetic aqueous solution. Effects of various process parameters(pH, equilibrium time, and temperature) were investigated in order to optimize the biosorptive removal. The maximum biosorption capacity of MABL was observed to be 28.986 mg/g at a temperature of 303 K, a biosorbent dose of 0.6 g, a contact time of 90 min, and a pH value of 7. Different kinetic models(the pseudo-first-order,pseudo-second-order, Elovich, and intraparticle diffusion models) were evaluated. The pseudo-second-order kinetic model was found to be the best fitted model in this study, with a coefficient of determination of R~2 = 0.974. Five different isotherm models(the Langmuir, Freundlich,Temkin, Dubinin-Radushkevich, and Brunauer-Emmett-Teller(BET) models) were investigated to identify the best-suited isotherm model for the present system. Based on the minimum chi-square value(x~2 = 0 027) and the maximum coefficient of determination(R~2 = 0.996), the Langmuir isotherm model was found to represent the system well, indicating the possibility of monolayer biosorption. The sticking probability(S*) was found to be 0.41, suggesting a physisorption mechanism for biosorption of Ni(II) on MABL. The biosorbent was characterized using Fourier-transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), zeta potential, and BET surface area, in order to understand its morphological and functional characteristics.     

Evaluation of the adsorption capacity of alkali-treated waste materials for the adsorption of sulphamethoxazole

The present work is to develop potential adsorbents from waste material and employ them for the removal of a hazardous antibacterial, sulphamethoxazole, from the wastewater by the Adsorption technique. The Adsorption technique was used to impound the dangerous antibiotics from wastewater using Deoiled Soya (DOS), an agricultural waste, and Water Hyacinth (WH), a prolific colonizer. The adsorption capacity of these adsorbents was further enhanced by treating them with sodium hydroxide solution and it was seen that the adsorption capacity increases by 10 to 25%. Hence a comparative account of the adsorption studies of all the four adsorbents, i.e. DOS, Alkali-treated DOS, WH and Alkali-treated Water Hyacinth has been discussed in this paper. Different isotherms like Freundlich, Langmuir and Dubinin-Radushkevich were also deduced from the adsorption data. Isotherm studies were in turn used in estimating the thermodynamic parameters. DOS showed sorption capacity of 0.0007 mol g(-1) while Alkali-treated Deoiled Soya exhibited 0.0011 mol g(-1) of sorption capacity, which reveals that the adsorption is higher in case of alkali-treated adsorbent. The mean sorption energy (E) was obtained between 9 and 12 kJ mol, which shows that the reaction proceeds by ion exchange reaction. Kinetic study reveals that the reaction follows pseudo-second-order rate equation. Moreover, mass transfer studies performed for the ongoing processes show that the mass transfer coefficient obtained for alkali-treated moieties was higher than the parent moieties. The breakthrough curves plotted from the column studies show percentage saturation of 90-98%. About 87-97% of sulphamethoxazole was recovered from column by desorption.     

Removal of copper(II) from aqueous solution using chemically modified fruit peels as efficient low-cost biosorbents

Fruit peels, which are common agricultural byproducts, have been extensively used as abandoned or low-cost biosorbents to remove heavy metals. In this study, dragon fruit peel (DFP), rambutan peel (RP), and passion fruit peel (PFP) were used to remove Cu(II) ions from an aqueous solution. Concentrations of the adsorbed metal ions were determined using the atomic absorption spectroscopic method. Adsorption experiments were performed with different adsorbent dosages, pH values, contact times, and initial copper concentrations. The optimum set of conditions for biosorption of Cu(II) ions was found to be an adsorbent dosage of 0.25 g, a contact time of 180 min, an initial concentration of 100 mg/L, a pH value of 4 for RP and PFP, and a pH value of 5 for DFP. The adsorption conformed with the pseudo-second-order kinetic model. The adsorption data were consistent with the Langmuir and Freundlich isotherm models, but the best fit was with the Langmuir model. The Langmuir monolayer adsorption capacity values of DFP, RP, and PFP were calculated to be 92.593, 192.308, and 121.951 mg/g, respectively. RP showed a higher adsorption capacity of Cu(II) ions than PFP and DFP for all parameters. The results indicate that these biosorbents might be used to effectively adsorb Cu(II) ions from wastewater treatment plants.     

天然沸石对氨氮的吸附作用及其影响因素

通过实验研究天然沸石对氨氮的吸附作用及其影响因素。结果表明,沸石对氨氮的吸附过程遵循准二级动力学模型;沸石对氨氮的等温吸附可用Langmuir和Freundlich等温模型拟合,相关系数R2达到极显著相关(P0.01);随着天然沸石粒径与投加量的减小,沸石对氨氮的吸附量显著增加;在pH值中性时,去除效果最好;温度升高有利于沸石对氨氮的吸附。     

生物炭/铁酸锰对Zn^2+和Cu^2+的吸附性能试验

为探求吸附效果好、回收方便的吸附剂以解决重金属污染废水的处理难题,以玉米秸秆和铁酸锰为原料,通过溶胶-凝胶法以蛋清为络合剂经热解制备了一种生物炭/铁酸锰(BC/FM)复合材料,在对该复合材料扫描电子显微镜(SEM)和磁滞回线分析的基础上,进行了去除废水中Zn^2+、Cu^2+的吸附试验。结果表明,铁酸锰可有效地负载到生物炭上,形成官能团丰富、磁性良好的复合材料;BC/FM对Zn^2+、Cu^2+的吸附最佳pH值分别为5和6,并均在90 min达到吸附平衡,准二级模型能更好地描述BC/FM对Zn^2+、Cu^2+吸附过程;Langmuir模型拟合曲线和Freundlich模型拟合曲线分别适用于描述BC/FM对Zn^2+、Cu^2+的等温吸附过程,且均为自发吸热反应;BC/FM对Zn^2+、Cu^2+吸附机制主要为络合反应。     

水中三种典型含氮有机物的活性炭吸附特性研究

利用三种类型活性炭(粉末炭PAC、活性炭纤维ACF、颗粒活性炭GAC),对三种典型含氮有机物(色氨酸、腺嘌呤和三聚氰胺)的吸附容量和吸附速率开展了研究。研究表明:PAC与ACF对色氨酸具有较高的吸附容量,吸附等温线符合Langmuir模型,拟二级动力学模型能够很好反应吸附速率变化;GAC吸附色氨酸等温线符合BET模型,其吸附速率变化符合内扩散模型。ACF与GAC对腺嘌呤均具有较高的吸附容量,其吸附等温线符合Freundlich模型,拟二级动力学能较好地反应了吸附速率的变化;而PAC对腺嘌呤的吸附更符合Langmuir模型,吸附速率变化同样符合拟二级模型。三种活性炭对三聚氰胺的吸附均大致符合BET模型,在低于液相饱和浓度条件下,三种炭的三聚氰胺吸附容量均较小,三种炭吸附三聚氰胺速率的变化都符合拟二级动力学模型。