The Pre-concentration and determination of Iridium and Palladium in environmental water by imprinted polymer-based method

In this study, the imprinted aniline–formaldehyde was used as an adsorbent for removal of Iridium and Palladium ions from aqueous solutions through batch equilibrium. The sorbent was characterized by fourier transform infrared spectroscopy. The influence of pH, equilibrium time, temperature and initial concentration of metal ions on adsorbed amount of both ions were investigated. The maximum adsorption capacity in initial concentration of 100 mg/L was found to be 12.5 mg/g at pH 7.0 and 14.3 mg/g at pH 8.0 for Iridium and Palladium, respectively. In addition, the best desorption of the metal ions from resin was obtained by 0.5 mol/L nitric acid as eluting agent. The profile of both ions uptake on this sorbent reflects good accessibility of the chelating sites in the imprinted aniline–formaldehyde. Langmuir, Freundlich, Temkin and Redlich–Peterson isotherm models were applied to analyze the experimental data. Moreover, Langmuir linear method was used to obtain the isotherm parameters. However, Langmuir type II achieved the highest coefficient which led to the best fit for the palladium and the best fit for Iridium obtained from linear Redlich–Peterson. However, the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant values obtained at different temperatures. The results showed that the adsorption for Iridium and Palladium ions was spontaneous nature and endothermic. Moreover, the method was applied for the determination of both ions from tap water samples.     

ZH型重金属螯合纤维对水溶液中Sr2+的吸附行为

研究了ZH型重金属螯合纤维对水溶液中Sr~(2+)的吸附行为,考察了pH值、纤维加入量、Sr~(2+)初始浓度、作用时间等对吸附行为的影响,并采用SEM、EDS和FTIR等现代分析测试手段探讨了ZH型重金属螯合纤维对Sr~(2+)的吸附机制。结果表明,在pH值为7.0、纤维加入量为2.0 g/L、Sr~(2+)初始质量浓度为50 mg/L的条件下,纤维对Sr~(2+)的吸附在4 h左右基本达到平衡。实验条件下ZH型重金属螯合纤维对Sr~(2+)的最大吸附量可达26.22 mg/g。等温吸附拟合结果表明,ZH型重金属螯合纤维对Sr~(2+)的吸附可能是以单分子层为主的单分子层和多分子层吸附共同作用的结果。纤维对Sr~(2+)的动力学吸附过程符合准二级动力学模型。红外光谱分析表明Sr~(2+)与纤维上—NH_2和—COOH等基团进行配位络合从而吸附在纤维表面,—CH_2—和C=CH_2等基团参与此吸附过程。能谱分析表明Sr~(2+)与纤维上Na~+和Ca~(2+)还存在着离子交换作用。     

Comparison of linear and nonlinear forms of isotherm models for Zn(II) and Cu(II) sorption on a kaolinite

The most appropriate method in designing the adsorption systems and assessing the performance of the adsorption systems is to have an idea on adsorption isotherms. Comparison analysis of linear least square method and nonlinear method for estimating the isotherm parameters was made using the experimental equilibrium data of Zn(II) and Cu(II) onto kaolinite. Equilibrium data were fitted to Freundlich, Langmuir, and Redlich–Peterson isotherm equations. In order to confirm the best-fit isotherms for the adsorption system, the data set using the chi-square (χ ²), combined with the values of the determined coefficient (r ²) was analyzed. Nonlinear method was found to be a more appropriate method for estimating the isotherm parameters. The best fitting isotherm was the Langmuir and Redlich–Peterson isotherm. The Redlich–Peterson is a special case of Langmuir when the Redlich–Peterson isotherm constant g was unity. The sorption capacity of kaolinite to uptake metal ions in the increasing order was given by Cu (4.2721 mg/g)?<?Zn (4.6710 mg/g).     

Single and binary adsorption of lead and cadmium ions from aqueous solution using the clay mineral beidellite

Beidellite, a low-cost, locally available and natural mineral was used as an adsorbent for the removal of lead and cadmium ions from aqueous solutions in batch experiments. The kinetics of adsorption process was tested for the pseudo first-order, pseudo second-order reaction and intra-particle diffusion models. The rate constants of adsorption for all these kinetic models were calculated. Comparison amongst the models showed that the sorption kinetics was best described by the pseudo second-order model. Langmuir and Freundlich isotherm models were applied to the experimental equilibrium data for different temperatures. The adsorption capacities (Q°) of beidellite for lead and cadmium ions were calculated from the Langmuir isotherm. It was found that adsorption capacity was in the range of 83.3–86.9 for lead and 42–45.6 mg/g for cadmium at different temperatures. Thermodynamic studies showed that the metal uptake reaction by beidellite was endothermic in nature. Binary metal adsorption studies were also conducted to investigate the interactions and competitive effects in binary adsorption process. Based on the optimum parameters found, beidellite can be used as adsorbent for metal removal processes.     

Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads

Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, in contrast to the traditionally used calcium alginate beads. Our adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h, and the removal efficiency of chromium(VI) was found to be 95 %. The adsorption data were applied to Langmuir, Freundlich, Dubinin–Redushkevich (D–R), and Temkin isotherm equations. Both Langmuir and Freundlich isotherm constants indicated a favorable adsorption. The value of mean sorption energy calculated from D–R isoterm indicates that the adsorption is essentially physical. The high maximum chromium(VI) adsorption capacity was determined from the Langmuir isotherm as 36.5 mg/g dry alginate beads. The chromium(VI) adsorption data were analyzed using several kinetic models such as the pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models, and the rate constants were quantified. Our study suggests that barium alginate beads can be used as cost-effective and efficient adsorbents for the removal of chromium(VI) from contaminated waters.     

焙烧水滑石吸附脱除水中硫酸根离子的研究

利用焙烧水滑石对水中硫酸根离子进行吸附性能研究,考查了初始pH值、吸附时间、吸附剂用量等条件对吸附的影响。结果表明,焙烧水滑石对水中硫酸根离子具有良好的吸附能力。X射线衍射分析结果表明,水滑石及其焙烧产物对硫酸根的吸附机理不同。pH值对吸附的影响较大,pH值较低时吸附效果较好。吸附平衡符合Langmuir方程,室温下饱和吸附量为32.895 mg/g。     

Saraca indica leaf powder for decontamination of Pb: removal, recovery, adsorbent characterization and equilibrium modeling

The present study explores the effectiveness of Saraca indica leaf powder, a surplus low value agricultural waste, in removing Pb ions from aqueous solution. The influence of pH, biomass dosage, contact time, particle size and metal concentration on the removal process were investigated. Batch studies indicated that maximum biosorption capacity for Pb was 95.37% at the pH 6.5. The sorption process followed the first order rate kinetics. The adsorption equilibrium data fitted best to both Langmuir and Freundlich isotherms. Morphological changes observed in scanning electron micrographs of untreated and metal treated biomass confirmed the phenomenon of biosorption. Fourier transform infrared spectroscopy of native and exhausted leaf powder confirmed lead biomass interactions responsible for sorption. Acid regeneration was tried for several cycles with a view to recover the sorbed metal ion and also to restore the sorbent to its original state. The findings showed that Saraca indica leaf powder can easily be envisaged as a new, vibrant, low cost biosorbent for metal clean up operations.     

Adsorption isotherm models and error analysis for single and binary adsorption of Cd(II) and Zn(II) using leonardite as adsorbent

Leonardite, a by-product from coal mines, was applied to adsorb Cd(II) and Zn(II) from aqueous solutions. Individual and simultaneous adsorptions of the two metal ions were investigated. In a single-component adsorption system, Langmuir and Freundlich isotherms were fitted to the adsorption data. Linear and nonlinear regression methods were used for the assessment of the optimum adsorption isotherm. Error functions including root-mean-square error, sum of the squares of the errors, mean absolute percentage error, Marquardt’s percent standard deviation (MPSD), and Chi-square were applied in the nonlinear regression. The most suitable model for the adsorption of Cd(II) and Zn(II) in the single system is the Freundlich isotherm. The isotherm parameters calculated by MPSD provided the lowest sum of normalized error (SNE) value. The adsorption capacity was found to be 23.89 mg/g for Cd(II) and 16.86 mg/g for Zn(II). It was observed that the adsorption of Cd(II) on leonardite is greater than that of Zn(II). For binary component adsorption systems, Cd(II) and Zn(II) showed antagonistic behavior. The presence of the other metal ions could decrease the amount of metal adsorbed. Binary adsorption of Cd(II) and Zn(II) was tested with regard to four multi-component isotherms: Extended Langmuir, Modified Langmuir, Sheindorf–Rebuhn–Sheintuch, and Extended Freundlich. The Extended Freundlich isotherm proved to be a good fit for the experimental data.     

Kinetic and equilibrium study of Ni(II) sorption from aqueous solutions onto Peganum harmala-L

In this study, the adsorption behavior of Ni(II) in an aqueous solution system using natural adsorbent Peganum harmala-L was measured via batch mode. The prepared sorbent was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, N₂ adsorption–desorption and pH_zpc. Adsorption experiments were carried out by varying several conditions such as contact time, metal ion concentration and pH to assess kinetic and equilibrium parameters. The equilibrium data were analyzed based on the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particular diffusion models. Experimental data showed that at contact time 60 min, metal ion concentration 50 mg/L and pH 6, a maximum amount of Ni(II) ions can be removed. The experimental data were best described by the Langmuir isotherm model as is evident from the high R ² value of 0.988. The adsorption capacity (q _m) obtained was 68.02 mg/g at an initial pH of 6 and a temperature of 25 °C. Kinetic studies of the adsorption showed that equilibrium was reached within 60 min of contact and the adsorption process followed the pseudo-first-order model. The obtained results show that P. harmala-L can be used as an effective and a natural low-cost adsorbent for the removal of Ni(II) from aqueous solutions.     

针铁矿/水界面反应性的实验研究

选择针铁矿对Pb2+、Cu2+、Cd2+等3种重金属离子的吸附实验,开展矿物/水界面反应性研究.金属离子(M2+)在矿物-水溶液间分配有多种表面反应机制,这些表面反应发生作用的条件主要取决于吸附质水化学性质和矿物表面荷电性,因此,溶液pH值是影响矿物/水界面反应性的关键因素.在不同pH值条件下, 表面羟基可通过发生质子化或去质子化反应而使得矿物表面产生荷电性并发生改变,而金属离子的水解则可显著加快金属羟基配合物的形成,从而进一步增强了矿物/水界面反应.本实验条件下针铁矿表面对重金属离子的吸着量随pH值升高而升高,在一个较窄的pH值范围内吸附率急剧升高,呈S形分布.针铁矿对3种不同的重金属离子的吸附能力的强弱顺序是Cu2+＞Pb2+＞Cd2+.无论是Langmuir方程还是Freundlich方程,都能较好拟合针铁矿对重金属离子的等温吸附过程.Freundlich方程的n值均在0.1～0.5之间,说明重金属离子在针铁矿表面的吸附并不能简单地归结为单配位或双配位模式,可能存在着多种吸附结合形态.表观吸附常数KM值的变化规律,说明重金属离子与针铁矿表面反应模式及其表面吸附形态发生了变化,具体的吸附形态还有待谱学研究进一步证实.     

Comparison of fast elimination of Cr(VI) by alumina nanofiber and alumina nanoporous

The goal of this study is examination of the mixture between adsorption and permeation process for removing chromium (VI) from the water. Two types of supported membranes are developed: The first one which was made by sol–gel method is called nanoporous and the second one which was made by electrospinning is called nanofiber. The sorption capacity of nanoporous and nanofiber is examined in single batch experiments at various pH values, and it is found that maximum chromium removal is observed for both nanoporous and nanofiber at pH 3.5. Adsorption studies illustrated that the Cr(VI) adsorption onto alumina nanoporous and nanofiber is affected by changes in pH, contact time, dosage of adsorbent, concentration of chromium and solution volume. Langmuir and Freundlich isotherms can be used to explain the adsorption equilibria of Cr(VI) onto alumina nanoporous and nanofiber. It was found that balance adsorption data adequate Langmuir isotherm more than Freundlich model. Adsorption kinetics was found to be fitted to pseudo-second order and Weber and Morris model. The output of multiple linear regressions was run for the second-order response surface model implied that the linear agents of pH, sorbent dosage and Cr(VI) concentration are more significant factors. Manufacturing electrospun alumina nanofiber and sol–gel nanoporous with these cheap materials, renewable and fast methods are so important although the removal percentage is significant.     

A zinc oxide-coated nanoporous carbon adsorbent for lead removal from water: Optimization, equilibrium modeling, and kinetics studies

A zinc oxide-coated nanoporous carbon sorbent was prepared by acid modification and ZnO functionalization of mesoporous carbon. The synthesized materials, such as mesoporous carbon, oxidized mesoporous carbon and zinc oxide-coated nanoporous carbon, were characterized by nitrogen adsorption–desorption analysis, Fourier transform infrared spectra, scanning electron microscopy, and transmission electron microscopy. ZnO on oxidized mesoporous carbon gradually increased with increase in the number of cycles. Furthermore, the effects of agitation time, initial metal ions concentration, adsorbent dose, temperature and pH on the efficiency of Pb(II) ion removal were investigated as the controllable factors by Taguchi method. The value of correlation coefficients showed that the equilibrium data fitted well to the Langmuir isotherm. Among the adsorbents, zinc oxide-coated nanoporous carbon showed the largest adsorption capacity of 522.8 mg/g (2.52 mmol/g) which was almost close to that of the zinc oxide-coated (2.38 mmol/g), indicating the monolayer spreading of ZnO onto the oxidized mesoporous carbon. The results of the present study suggest that ZnO-coated nanoporous carbon can be effectively used for Pb(II) adsorption from aqueous solution, whereas a part of acidic functional groups may be contributed to binding the Pb(II) for the oxidized mesoporous carbon and mesoporous carbon. Kinetic studies indicated that the overall adsorption process of Pb(II) followed the pseudo-second-order model. The ZnO-coated nanoporous carbon was regenerated and found to be suitable of reuse of the adsorbent for successive adsorption–desorption cycles without considerable loss of adsorption capacity.     

Removal of chromium (VI) from aqueous solutions using Lewatit FO36 nano ion exchange resin

The removal of the chromium (VI) ion from aqueous solutions with the Lewatit FO36 ion-exchange resin is described at different conditions. The effects of adsorbent dose, initial metal concentration, contact time and pH on the removal of chromium (VI) were investigated. The batch ion exchange process was relatively fast and it reached equilibrium after about 90 min of contact. The ion exchange process, which is pH dependent showed maximum removal of chromium (VI) in the pH range 5.0–8.0 for an initial chromium (VI) concentration of 0.5 mg/dm³. The equilibrium related to Lewatit FO36 ion- exchange capacity and the amounts of the ion exchange were obtained using the plots of the Langmuir adsorption isotherm. It was observed that the maximum ion exchange capacity of 0.29 mmol of chromium (VLVg for Lewatit FO36 was achieved at optimum pH value of 6.0. The ion exchange of chromium (VI) on this cation-exchange resin followed first-order reversible kinetics.     

Retention studies of chromium (VI) from aqueous solution on the surface of a novel carbonaceous material

In the present study, the retention capacity of carbonaceous material obtained from the diesel engine exhaust mufflers for Cr(VI) removal has been investigated. The physicochemical properties such as density, pH of aqueous slurry, pH at point of zero charge, ash content, moisture content, volatile matter, surface area, scanning electron microscopy and electron dispersive spectroscopy of the carbonaceous material were determined. The capacity of adsorbent for removal of Cr(VI) from aqueous solution was observed under different experimental condition like contact time, initial concentration of metal ions, pH and temperatures on the adsorption capacity of the adsorbent. Maximum adsorption of Cr(VI) ions was found at low pH. The adsorption process was found to follow second-order kinetics. The rate constant was evaluated at different temperatures along with other thermodynamic parameters like activation energy, Gibbs free energy change, enthalpy change and entropy change. Both Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium of carbonaceous material at different temperatures. Langmuir isotherm shows better fit than Freundlich isotherm at given conditions. The result shows that low-cost carbonaceous material from diesel engine exhaust mufflers can be efficiently used for wastewater treatment containing Cr(VI) ions.     

Removal of lead from aqueous solution using low cost abundantly available adsorbents

The removal of poisonous Pb (II) from wastewater by different low-cost abundant adsorbents was investigated. Rice husks, maize cobs and sawdust, were used at different adsorbent/metal ion ratios. The influence of pH, contact time, metal concentration, adsorbent concentration on the selectivity and sensitivity of the removal process was investigated. The adsorption efficiencies were found to be pH dependent, increasing by increasing the solution pH in the range from 2.5 to 6.5. The equilibrium time was attained after 120 min and the maximum removal percentage was achieved at an adsorbent loading weight of 1.5 gm. The equilibrium adsorption capacity of adsorbents used for lead were measured and extrapolated using linear Freundlich, Langmuir and Temkin isotherms and the experimental data were found to fit the Temkin isotherm model.     

巯基有机硅烷嫁接高岭石对Cd(Ⅱ)的吸附性能研究

由于重金属镉离子的吸附性能较差、毒性大,因此,寻找镉离子的高效吸附材料具有重要现实意义。本文开展巯基硅烷对高岭石的嫁接改性研究,经红外光谱测试证实,成功将巯基引入到高岭石表面。同时,硅烷改性对高岭石晶体结构没有产生影响。通过批量实验考察了高岭石和巯基硅烷改性高岭石(K-SH)对Cd(Ⅱ)的吸附特征,主要探讨了p H值、时间对吸附效率的影响。矿物对Cd2+的吸附动力学符合准二级动力学模型,吸附等温方程更符合Langmuir模型,并估算的K-SH的最大吸附量是4.375 mg/g,比高岭石的大近20倍。改性高岭石表面嫁接了巯基后,可为高岭石吸附Cd(Ⅱ)提供大量的新吸附位点,通过配位复合作用显著提高对镉离子的吸附固定能力。因此,巯基硅烷改性高岭石是一种有应用前景的土壤修复材料。     

Aqueous heavy metals removal by adsorption on β-diketone-functionalized styrene–divinylbenzene copolymeric resin

An investigation was undertaken regarding the adsorption of different heavy metal ions from aqueous solutions using ??-diketone-functionalized styrene divinylbenzene resin under different experimental conditions such as initial concentration of metal ions, contact time, pH, and chelating capacity. The functionalization of resin was carried out by the condensation reaction of sodium salt of ??-diketones (pentane-1,3-dione) and chloromethylated styrene?Cdivinylbenzene resin in dichloromethane. Functionalized resin beads were characterized by Fourier transform infrared spectroscopy. The batch method was employed using different metal ions solution from 5 to 15?mg/L at different contact times. The adsorption kinetics was tested for the pseudo-first order, pseudo-second order reaction at different experimental conditions. The rate constant of adsorption kinetic models were also calculated and good correlation coefficient (R ²?>?0.9941) was obtained for pseudo-second order kinetic model. The maximum adsorption value obtain for lead (0.725728?mg/g), chromium (0.9199?mg/g), nickel (0.4974?mg/g), cobalt (0.6196?mg/g) and cadmium (0.6519?mg/g) at equilibrium condition, which shows that ??-diketone-functionalized styrene divinylbenzene resin is an effective adsorbent for toxic metal ions.     

Removal of cadmium and humic acid from aqueous solutions using surface modified nanozeolite A

The sorption of cadmium and humic acids from aqueous solutions using surface-modified nanozeolite A has been investigated under various examination conditions. The morphology of untreated and treated nanozeolite was studied under scanning electron microscope and transmission electron microscope. Isotherms of cadmium adsorption onto surface-modified nanozeolite A were studied at different pH, solid to liquid ratio, adsorbate concentration and interaction time. Kinetic and equilibrium studies were conducted and the equilibrium data have been analyzed using Langmuir and Freundlich isotherm models. The study revealed that experimental results were in agreement with the Freundlich model. The Langmuir monolayer adsorption capacity was found to be 1666.67 g cadmium and 6.75 g humic acid per gram of modified nanozeolite A, which is higher than that of reported value for other zeolites. The sorption ability was enhanced by surface modification and reduction in size and enabled the zeolite to adsorb cadmium. The adsorption of cadmium and humic acid on nanozeolite was found to be the highest at pH 6 and 3, respectively. Results showed that solid to liquid ratio and pH are the most important factors for cadmium and humic acid removal, respectively. Effect of competitive ions was studied and results showed that there is no competition between cadmium and humic acid sorption and presence of these ions.     

Biosorption studies on shelled Moringa oleifera Lamarck seed powder: Removal and recovery of arsenic from aqueous system

The present study explores the unexploited sorption property of the shelled Moringa oleifera seeds (SMOS) for decontamination of arsenic from water bodies. Sorption studies (batch experiments) result into the standardization of optimum conditions for removal of 60.21% As(III) and 85.60% As(V) as follows: biomass dosage (2.0 g), metal concentration (25 mg/L), contact time (60 min) and volume of the test solution (200 ml) at pH 7.5 and 2.5, respectively. The adsorption data are fitted with Langmuir isotherm. Surface area has been measured using BET surface area analyzer. Morphological changes observed in scanning electron micrograph of native and treated SMOS indicates the existence of biosorption process. Fourier transform infrared spectrometry of exhausted seed biomass highlights protein/amino acid–arsenic interactions responsible for sorption phenomenon. Regeneration has also been attempted for several cycles with a view to restore the sorbent to its original state. The sorption capacity of the regenerated biomass remained almost constant after three cycles of sorption process, suggesting that the lifetime cycle was sufficient for continuous application. The findings open up new avenues in the decontamination of arsenic using SMOS from arsenic contaminated water, as domestic and environment-friendly safe technology.