氧化石墨烯/海藻酸钙水凝胶复合膜对水中Cd(II)的吸附

将氧化石墨烯(GO)、致孔剂与海藻酸钠共混后与CaCl₂交联制备的GO/海藻酸钙（CA）水凝胶复合膜作为含重金属废水的吸附材料。采用SEM和TEM表征了复合膜的表面形貌及透射性能,且分析了GO的加入对复合膜的力学性能、平均孔径、水通量及表面官能团的影响。为探究GO/CA水凝胶复合膜的吸附性能,考察了其吸附Cd(II)的影响因素:pH（6~7）值、初始离子浓度、接触时间、温度（三者均正相关）。用FTIR、XPS在吸附前后对复合膜进行了表征;引入了吸附动力学和等温线模型分析其吸附机制。探究结果表明GO的加入提高了复合膜的力学性能、平均孔径及水通量;吸附过程遵循Langmuir等温线,属于单层吸附,拟合得到的最大吸附量为173.61 mg/g;伪一级和伪二级吸附动力学分别在低浓度和高浓度时能较好地描述吸附过程的动力学行为;吸附机制主要为物理作用力吸附和离子交换。经过5个连续的吸附-解吸循环证明了GO/CA水凝胶复合膜的可重复利用性。      

氮化硼纳米片吸附Cd(II)的动力学和热力学研究

本工作对Cd(II)在多孔六方氮化硼(p-BN)上的吸附行为和机理进行了系统而全面的研究, 考察了溶液pH、吸附剂用量、接触时间和温度等条件对于Cd(II)吸附的影响, 并采用不同手段表征了吸附前后p-BN的化学组成、形态和表面官能团的变化, 进而研究其吸附机理。研究结果显示, 在pH 7.0和313 K条件下, Cd(II)的最大吸附容量可达到184 mg·g ^-1, 其动力学数据与拟二级模型和颗粒内扩散模型吻合, 表明吸附主要受化学吸附控制, 限速步骤主要是分子扩散。Cd(II)在p-BN上的吸附是一个自发和吸热过程, 吸附等温线分别符合Freundlich和Langmuir模型, 说明Cd(II)通过多层和单层吸附而吸附在非均相表面上。XPS的光谱结果显示, p-BN吸附剂具有大量的B-N, B-O等结构用作键合位点, 有利于从废水中吸收Cd(II)。这些结果表明, p-BN有希望作为吸附材料用于清除水体中的Cd(II)。     

Ce(SO_4)_2改性褐煤半焦对废水中Cd(Ⅱ)的吸附效果

为了提高褐煤半焦对重金属离子的吸附性能,将褐煤用3.0 mol/L H_3PO_4进行活化,将改性剂Ce(SO_4)_2·4H_2O与活化褐煤混合,通过炭化制备出改性褐煤半焦,对改性褐煤半焦的制备条件进行了优化,并通过扫描电镜(SEM)和能谱仪(EDS)对改性褐煤半焦进行了表征。在25℃和静态条件下,研究了改性褐煤半焦对模拟废水中Cd(Ⅱ)的吸附效果,探讨了改性褐煤半焦对废水中Cd(Ⅱ)的吸附条件。结果表明:改性褐煤半焦对模拟废水中Cd(Ⅱ)具有很好的吸附性能,Cd(Ⅱ)的去除率达99.8%。改性褐煤半焦对模拟废水中Cd(Ⅱ)吸附的适宜条件为吸附温度为25℃,Ce(SO_4)_2·4H_2O用量为褐煤质量的5.0%,废水pH值为3.0,Cd(Ⅱ)的起始浓度为40.00 mg/L,吸附时间为2.0 h,Cd(Ⅱ)与改性褐煤半焦的质量比为1∶50。按照改性褐煤半焦对模拟废水中Cd(Ⅱ)吸附的适宜条件,含Cd(Ⅱ)12.90 mg/L的电镀废水经改性褐煤半焦处理后,Cd(Ⅱ)去除率为99.3%,Cd(Ⅱ)的浓度降为0.09 mg/L,可达标排放。改性褐煤半焦可再生利用。     

改性竹炭对水溶液中Cu(Ⅱ)、Cd(Ⅱ)的吸附性能

采用不同方法对竹炭进行改性,寻求吸附效果最好的改性产品,并研究其对溶液中Cu2+、Cd2+的吸附性能,考察了吸附时间、溶液pH值、吸附温度和溶液初始浓度对吸附效果的影响,同时与未改性竹炭的吸附性能进行了对比。实验结果表明:相同条件下,氧化改性竹炭对Cu2+、Cd2+的吸附效果明显优于其他方法改性竹炭和未经改性的竹炭。吸附温度为15℃、25℃、45℃时,氧化竹炭对Cu2+的最大吸附量分别为6.653mg/g、6.702mg/g和7.897mg/g,而氧化竹炭对Cd2+的最大吸附量分别为1.700mg/g、1.826mg/g和2.282mg/g。氧化改性竹炭对Cu2+、Cd2+的吸附均符合Freundlich方程和Langmuir方程。实验证明,氧化竹炭是一种应用前景广泛的重金属离子吸附剂。     

不同pH条件下硫化钼纳米片吸附Cd(II)的微观机制研究

本研究结合静态实验和X射线吸收精细结构谱学(EXAFS)评估了硫化钼纳米片对重金属Cd(II)的吸附行为和微观机制。结果表明: Cd(II)在硫化钼纳米片上的吸附受溶液pH、反应时间和温度的显著影响, 但不受离子强度的影响。在pH 3.3~9.6范围内, pH升高显著促进了硫化钼对Cd(II)的吸附量, 但不改变吸收速率、吸附等温线和热力学。二级动力学模型能更好地拟合该吸附平衡, 且内表面颗粒扩散模型显示了吸附过程中的三个典型阶段。等温线和热力学分析说明Cd(II)在硫化钼上的吸附是异质性的、自发的、吸热的和不可逆的过程。EXAFS光谱学分析揭示了该吸附存在两种类型: 在较低的pH(3.56, 6.48)条件下, 内表面络合以Cd-S配位键为主; 在较高的pH(9.57)条件下, 出现Cd(OH)₂沉淀, 且配位键以Cd-O和Cd-Cd的形式存在。这些研究结果对于评估重金属离子和硫化钼纳米片在分子水平上的作用机理提供了新的视野。     

蛭石/聚乙二醇/丙烯酸水凝胶对阳离子染料的吸附研究

研究了用辉光放电电解等离子体引发合成的蛭石/聚乙二醇/丙烯酸(VMT/PEG/AA)水凝胶对常见阳离子染料结晶紫、亚甲基蓝和孔雀石绿的吸附行为,考察了pH值、吸附时间、初始染料浓度等因素对吸附量的影响,同时对水凝胶的吸附-解吸性能进行了研究。结果表明:VMT/PEG/AA水凝胶达到吸附平衡的时间为3h,最佳pH值为6,其对染料的吸附行为符合准二级动力学方程,水凝胶具有一定的解吸和再生能力。     

氮化硼纳米片吸附Cd(Ⅱ)的动力学和热力学研究（英文）

本工作对Cd(Ⅱ)在多孔六方氮化硼(p-BN)上的吸附行为和机理进行了系统而全面的研究,考察了溶液pH、吸附剂用量、接触时间和温度等条件对于Cd(Ⅱ)吸附的影响,并采用不同手段表征了吸附前后p-BN的化学组成、形态和表面官能团的变化,进而研究其吸附机理。研究结果显示,在pH 7.0和313 K条件下, Cd(Ⅱ)的最大吸附容量可达到184mg·g–1,其动力学数据与拟二级模型和颗粒内扩散模型吻合,表明吸附主要受化学吸附控制,限速步骤主要是分子扩散。Cd(Ⅱ)在p-BN上的吸附是一个自发和吸热过程,吸附等温线分别符合Freundlich和Langmuir模型,说明Cd(Ⅱ)通过多层和单层吸附而吸附在非均相表面上。XPS的光谱结果显示,p-BN吸附剂具有大量的B–N,B–O等结构用作键合位点,有利于从废水中吸收Cd(Ⅱ)。这些结果表明, p-BN有希望作为吸附材料用于清除水体中的Cd(Ⅱ)。     

磁性壳聚糖半互穿热膨胀水凝胶的制备及对Cr(Ⅵ)的吸附性能

以壳聚糖、丙烯酰胺和新型温敏大分子单体为主要原料,N,N′-亚甲基双丙烯酰胺为交联剂,采用水溶液半互穿网络聚合技术制备了壳聚糖半互穿热膨胀水凝胶,并通过原位化学共沉淀法向水凝胶中引入Fe3 O4纳米粒子,得到了磁性壳聚糖半互穿热膨胀水凝胶(Semi-INP/Fe3 O4).利用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)仪、热重分析(TG)仪和扫描电子显微镜(SEM)对所得样品进行了表征分析.考察了Semi-INP/Fe3 O4的热溶胀性能及吸附时间、吸附温度和Semi-INP/Fe3 O4用量对Cr(Ⅵ)去除率的影响.结果表明,本工作成功制备了Semi-INP/Fe3 O4,且该水凝胶具有明显的热溶胀性能;Semi-INP/Fe3 O4对Cr(Ⅵ)的去除率分别随吸附时间的延长、吸附温度的升高及吸附剂用量的增加而增大.70℃,pH=3时,10 g/L Semi-INP3/Fe3 O4对10 mg/L Cr(Ⅵ)的去除率可达98.03％.     

温度及pH敏感P (DMAEMA-g-PEG)水凝胶的合成与性能研究

通过氧化还原自由基溶液聚合制备了聚甲基丙烯酸-N,N'-二甲氨基乙醋接枝聚乙二醉共聚水凝胶P (DMAEMA-g-PEG).实验结果表明,该水凝胶具有温度、pH敏感性及溶胀一退胀可逆性,其相转变温度在45℃左右.少童PEG大分子单体的加入,使水凝胶具有较高的溶胀率,但随着PEG大分子单体用量的增大,溶胀率反而下降;水凝...     

互穿网络水凝胶的前端聚合制备及吸附性能研究

采用前端聚合方法,以丙烯酸(AA)和丙烯酰胺(AM)为单体,在4种线性高分子水溶液中制备了半互穿网络结构(semi-IPN)的水凝胶,其中的线性高分子分别为:聚乙烯醇(PVA)、聚乙二醇(PEG)、聚丙烯酰胺(PAM)、聚乙烯吡咯烷酮(PVP)。用扫描电镜(SEM)、吸水率和吸附量对互穿网络水凝胶的结构和性能进行了表征,结果表明:水解对水凝胶的吸水性能影响显著,使吸水率平均提高9.1倍,但对吸附性能影响较小,使亚甲基蓝吸附量提高不足1倍;在4种互穿网络水凝胶中,P(AM-AA)/PEG的吸水率最大,高达627.9g/g,P(AM-AA)/PAM互穿网络水凝胶对亚甲基蓝有最大的吸附能力,吸附量为91.6mg/g。     

Cystine-modified biomass for Cd(II) and Pb(II) biosorption

The surface of dried biomass of baker's yeast was modified by crosslinking cystine with glutaraldehyde. X-ray photoelectron spectroscopy and microscope were used to characterize the modified biomass. The adsorption capacity of the modified biomass for Cd(2+) and Pb(2+) showed an increase compared with the pristine biomass due to the presence of cystine on the biomass surface. Experimental data showed that the adsorption of the two metal ions increased with time until equilibrium was achieved. The adsorption capacities for Cd(2+) and Pb(2+) were 11.63 and 45.87 mg g(-1), respectively, which were determined from the Langmuir isotherm. The loaded biosorbent was regenerated using HCl solution and could be used repeatedly at six times with little loss of uptake capacity. FTIR spectroscopy revealed that carboxyl, amide, and hydroxyl groups on the biomass surface were involved in the adsorption of Cd(2+) and Pb(2+).     

A comparative study for the sorption of Cd(II) by soils with different clay contents and mineralogy and the recovery of Cd(II) using rhamnolipid biosurfactant

Recent research has demonstrated that biosurfactants, especially rhamnolipids, can enhance recovery of soil-bound metals. To propose the success of remediation process of soils by rhamnolipids, both sorption and desorption characteristics of soils having different clay mineralogy should be known exactly. To assess sorption of Cd(II), batch equilibrium experiments were performed using three soils characterized with different proportions of clay minerals from Eski?ehir region of Turkey. Soil pH, initial metal concentration and clay mineralogy affected the sorption process. For comparisons between soils, the sorption process was characterized using the Langmuir, Freundlich, Redlich-Peterson, Koble-Corrigan sorption models. The Freundlich model showed the best fit for the Cd(II) sorption data by the soils, while the Langmuir-type models generally failed to describe the sorption data. Soils with higher clay content characterized by having smectite as a dominant component had the greatest sorption capacity and intensity estimated by the KF and n parameters of the Freundlich model. The soil C has the highest sorption efficiency of 83.9%, followed by soils B and A with sorption efficiencies of 76.7% and 57.9%, respectively. After the soils were loaded by different doses of Cd(II), batch washing experiments were used to evaluate the feasibility of using rhamnolipid biosurfactant for the recovery of Cd(II) from the soils. The Cd(II) recovery of the soils were investigated as a function of pH, amount of Cd(II) loaded to the soils, and rhamnolipid concentration. Cd(II) recovery efficiencies from the soils using rhamnolipid biosurfactant decreased in the order of soil A>soil B>soil C. This order was the reverse of the Cd(II) sorption efficiency order on the soils. When 80 mM rhamnolipid was used, the recovery efficiencies of Cd(II) from the soils A, B, and C was found to be 52.9%, 47.7%, 45.5% of the sorbed Cd(II), respectively. Rhamnolipid sorption capacity of the soils in the presence of Cd(II) ions decreased in the order of soil A>soil B>soil C.     

Development of a New Selective Optical Sensor for Cd(II) Ions Based on 4-Hydroxy Salophen

A new sensor membrane based on immobilization of 4-hydroxy salophen on triacetyl cellulose has been developed for the determination of Cd(II) ions that displays excellent performance. The sensing membrane is capable of spectrophotometric determining of Cd(II) with an outstanding high selectivity over a dynamic range between 1.0$,times 10^{-6}$ and 5.0$,times 10^{-2}$ mol L$^{-1}$ with a limit of detection of 5.3 $,times 10^{-7}~$mol L $^{-1}$ (0.06 $mu$g mL $^{-1}$ The sensor shows a fast response time ($≪ {5}~$ min) and the membrane can be used for more than two months without observing any major deviation. The optode revealed very good selectivity with respect to many cations including alkali, alkaline earth, transition and heavy metal ions. The proposed sensor could be used to determine cadmium ions in water and waste water samples. Different experimental parameters such as variable affecting on sensor preparation and pH of the sample solution plus response time were studied. The optodes developed in the present work were found to be stable, cost effective, easy to prepare, and efficient for direct determination of Cd(II) in a variety of aqueous samples using spectrophotometry, with satisfactory results.      

Tartrazine modified activated carbon for the removal of Pb(II), Cd(II) and Cr(III)

A two in one attempt for the removal of tartrazine and metal ions on activated carbon has been developed. The method was based on the modification of activated carbon with tartrazine then its application for the removal of Pb(II), Cd(II) and Cr(III) ions at different pH values. Tartrazine adsorption data were modelled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacities qm were 121.3, 67 and 56.7mgg(-1) at initial pH values of 1.0, 6.0 and 10, respectively. The adsorption of tartrazine onto activated carbon followed second-order kinetic model. The equilibrium time was found to be 240min at pH 1.0 and 120min at pH 10 for 500mgL(-1) tartrazine concentration. A maximum removal of 85% was obtained after 1h of contact time. The presence of tartrazine as modifier enhances attractive electrostatic interactions between metal ions and carbon surface. The adsorption capacity for Pb(II), Cd(II) and Cr(III) ions has been improved with respect to non-modified carbon reaching a maximum of 140%. The adsorption capacity was found to be a pH dependent for both modified and non-modified carbon with a greater adsorption at higher pH values except for Cr(III). The enhancement percent of Pb(II), Cd(II) and Cr(III) at different pH values was varied from 28% to 140% with respect to non-modified carbon. The amount of metal ions adsorbed using static regime was 11-40% higher than that with dynamic mode. The difference between adsorption capacities could be attributed to the applied flow rate.     

Pb(II) and Cd(II) biosorption on Chondracanthus chamissoi (a red alga)

Chondracanthus chamissoi is an efficient biosorbent for Pb(II) and Cd(II). The sorption efficiency increases with pH and reaches an optimum around pH 4. Maximum sorption capacity reaches 1.37 mmol P bg(-1) and 0.76 mmol C dg(-1). The biosorbent has a marked preference for Pb(II) over Cd(II), though insufficient for separating these metals by a simple sorption step. The uptake kinetics is controlled by the resistance to intraparticle diffusion with a limited impact of particle size, metal concentration and sorbent dosage. In the present case, grinding the biomass does not improve sorption capacity and uptake kinetics. The sorption of metal ions is probably due to their interaction with carrageenan (one of the main constituents of the biosorbent): sulfonic groups (on the sulfated polysaccharide) have a higher affinity for Pb(II) than for Cd(II) according to HSAB rules.     

Application of grass char for Cd(II) treatment in column leaching test

Various adsorbents as well as toxicants have been investigated regarding the adsorption behaviors and mechanisms. However, most of these reports were based on batch test. The discrepancy in adsorption behaviors between batch test and column test has been recognized recently. This study was to investigate the sorption behavior of Cd(II) in a novel adsorbent made from Reed char. Batch adsorption test and column leaching test were both conducted. Various influence factors including confining pressure, pH, velocity, concentration and ionic strength were studied. The velocity was found to have negligible effect on the breakthrough of Cd(II). The adsorption affinity was observed for the first time to decrease from a high value (R(d) = 130.00) to a negligible one (R(d) = 1.20) with increasing confining pressure from 0 to 100.00 kPa. The breakthrough of acid Cd(II) solution was earlier for solutions with less pH and higher ionic strength. The Cd(II) laden adsorbent was reclaimed by flushing chelants through the column. The recycled adsorbent appeared to be applicable in the following adsorption treatment. Suggestions were provided regarding the potential engineering applications.     

Effect of Cu(II), Cd(II) and Zn(II) on Pb(II) biosorption by algae Gelidium-derived materials

Biosorption of Pb(II), Cu(II), Cd(II) and Zn(II) from binary metal solutions onto the algae Gelidium sesquipedale, an algal industrial waste and a waste-based composite material was investigated at pH 5.3, in a batch system. Binary Pb(II)/Cu(II), Pb(II)/Cd(II) and Pb(II)/Zn(II) solutions have been tested. For the same equilibrium concentrations of both metal ions (1 mmol l(-1)), approximately 66, 85 and 86% of the total uptake capacity of the biosorbents is taken by lead ions in the systems Pb(II)/Cu(II), Pb(II)/Cd(II) and Pb(II)/Zn(II), respectively. Two-metal results were fitted to a discrete and a continuous model, showing the inhibition of the primary metal biosorption by the co-cation. The model parameters suggest that Cd(II) and Zn(II) have the same decreasing effect on the Pb(II) uptake capacity. The uptake of Pb(II) was highly sensitive to the presence of Cu(II). From the discrete model it was possible to obtain the Langmuir affinity constant for Pb(II) biosorption. The presence of the co-cations decreases the apparent affinity of Pb(II). The experimental results were successfully fitted by the continuous model, at different pH values, for each biosorbent. The following sequence for the equilibrium affinity constants was found: Pb>Cu>Cd approximately Zn.     

Use of rice straw as biosorbent for removal of Cu(II), Zn(II), Cd(II) and Hg(II) ions in industrial effluents

Adsorption experiments were carried out using waste rice straw of several kinds as a biosorbent to adsorb Cu(II), Zn(II), Cd(II) and Hg(II) ions from aqueous solutions at room temperature. To achieve the best adsorption conditions the influence of pH and contact time were investigated. The isotherms of adsorption were fitted to the Freundlich equation. Based on the experimental data and Freundlich model, the adsorption order was Cd(II) > Cu(II) > Zn(II) > Hg(II) on the rice straw. This quick adsorption process reached the equilibrium before 1.5 h, with maximum adsorptions at pH 5.0. Thermodynamic aspects of the adsorption process were investigated. The biosorbent material was used in columns for the removal of ions Cu, Zn, Cd and Hg of real samples of industrial effluent and its efficiency was studied.     

Adsorption properties of Cd(II)-imprinted chitosan resin

A Cd(II)-imprinted chitosan resin (Cd-ICR) was prepared for adsorption of Cd(II) from aqueous solutions. Batch adsorption experiments were performed to evaluate the adsorption conditions, selectivity and reusability as well as its application in the removal of Cd(II) from oyster hydrolysate. The results indicated that the maximum adsorption capacity of Cd-ICR was 0.795 mmol/g in sole Cd(II) solution at pH 5.0, 45 °C with equilibrium time 10 h. The selectivity coefficient of Cd(II) and other metal cations on Cd-ICR indicated an overall preference for Cd(II), which was much higher than that of non-imprinted chitosan resin. Cd-ICR could be reused for ten times with about 27% regeneration loss. FTIR spectra demonstrated that Cd(II) in Cd-ICR occurred on amino and secondary hydroxyl groups. The removal ratio of Cd(II) from oyster hydrolysate was 73.6%, while that of Ca(II) and Zn(II) were 6.2 and 9.9%, respectively. This suggests that Cd-ICR is a very promising adsorbent for selective removal of Cd(II) from aqueous solutions.     

Sorption of Cd(II) onto kaolin as a soil component and desorption of Cd(II) from kaolin using rhamnolipid biosurfactant

In this study, a microbial surfactant, rhamnolipid, was investigated for its potential to enhance recovery of Cd(II) from kaolin, a representative soil component. The study was divided into two parts. In the first part, the sorption of Cd(II) ions to kaolin was investigated as a function of pH and initial Cd(II) ion concentration. Kaolin was also shown to be a good sorbent for treatment of Cd(II) ions from waste waters. The equilibrium sorption capacity for Cd(II) ions was measured and extrapolated using the Langmuir, Freundlich, Redlich-Peterson, and Koble-Corrigan sorption models. The best correlation between experimental and model predicted equilibrium uptake was obtained using the Kolbe-Corrigan sorption model. The values of parameters of the Koble-Corrigan model were determined as A=11.13 (mmol(1-b)kg(-1)L(b)); B=0.39 (L(b)mmol(-b)); b=0.48. In the second part, the desorption of Cd(II) from kaolin was investigated as a function of pH, rhamnolipid concentration, and the amount of sorbed Cd(II) by kaolin. The highest Cd(II) desorption efficiency by rhamnolipid biosurfactant from kaolin was obtained at pH 6.8, at an initial Cd(II) ion concentration of 0.87 mM (4.42 mmol Cd(II)/kg kaolin) and at a rhamnolipid concentration of 80 mM and found to be 71.9% of the sorbed Cd(II).