Development of chitosan-alginate based biosorbent for the removal of p-chlorophenol from aqueous medium

Removal of p-chlorophenol (pCP) from synthetic aqueous solutions was studied through adsorption on a biosorbent developed from chitosan (CS) and sodium alginate (SA), the natural cationic and anionic polysaccharides, respectively. Chitosan-coated sodium alginate beads were prepared and treated with calcium chloride solution in order to improve the stability as well as hydrophobic character. The resulting beads (CS/CA) were characterized using FTIR spectra, scanning electron microscopy (SEM), and BET surface analysis. The efficiency of this biosorbent in removing pCP from aqueous medium was studied under batch equilibrium and dynamic column flow experimental conditions. The binding capacity of the biosorbent was studied as a function of initial pH, contact time, initial concentration of adsorbate and amount of biomass. The data were fitted to pseudo-first-order, pseudo-second-order, and Weber–Morris models and found that the adsorption process followed pseudo-first-order kinetics. Further, the equilibrium data were fitted to Freundlich, Langmiur, and Dubinin–Radushkevich (D–R) adsorption isotherms and the isotherm constants were evaluated for adsorption of pCP. The maximum monolayer adsorption capacity of CS/CA beads was found to be 127 mg g^?1. Column flow results were used to generate breakthrough curves. The experimental results suggested that the chitosan–calcium alginate blended biosorbent was effective for the removal of pCP from aqueous medium.     

Removal of phenol by powdered activated carbon adsorption

In this study, the adsorption performance of powdered activated carbon (PAC) on phenol was investigated in aqueous solutions. Batch adsorption studies were performed to evaluate the effects of various experimental parameters like PAC type, PAC dose, initial solution pH, temperature and pre-oxidation on the adsorption of phenol by PAC and establish the adsorption kinetics, thermodynamics and isothermal models. The results indicated that PAC adsorption is an effective method to remove phenol from water, and the effects of all the five factors on adsorption of phenol were significant. The adsorption rate of phenol by PAC was rapid, and more than 80% phenol could be absorbed by PAC within the initial 10 min. The adsorption process can be well described by pseudo-second-order adsorption kinetic model with rate constant amounted to 0.0313, 0.0305 and 0.0241 mg·μg ^-1·min ^-1 with coal, coconut shell and bamboo charcoal. The equilibrium data of phenol absorbed onto PAC were analyzed by Langmuir, Freundlich and Tempkin adsorption isotherms and Freundlich adsorption isotherm model gave the best correlation with the experimental data. Thermodynamic parameters such as the standard Gibbs free energy (?G^o), enthalpy (?H^o) and entropy (?S^o) obtained in this study indicated that the adsorption of phenol by PAC is spontaneous, exothermic and entropy decreasing.     

菲和萘在黄土上的吸附等温线和吸附热力学

研究了菲和萘在黄土上的吸附行为,比较分析了Linear方程、Freundlich方程和Langmuir方程描述吸附等温线的准确性.结果表明,菲和萘在黄土上的吸附等温线呈非线性,Freundlich方程最符合其吸附行为.菲和萘在天然黄土上的吸附量随温度升高而降低.其吸附是一个放热过程,吸附热分别为0.017 74 kJ·mol-1和-0.061 25 kJ·mol-1; 吸附的标准自由能改变量分别为-9.939 kJ·mol-1和-7.333 kJ·mol-1.标准自由能的变小是菲和萘在黄土上吸附的推动力.经过阳离子表面活性剂改性后的黄土对菲和萘的吸附能力,随加入的表面活性剂占原土阳离子交换容量(CEC)的百分数增大明显增强,能更加有效地去除水环境中的多环芳烃类污染物.     

爬山虎茎粉对水体中氨氮的吸附特性

为从植物材料中筛选适宜的氨氮吸附材料,通过批实验研究了爬山虎茎在不同初始pH值、振荡时间、初始浓度和温度下对水溶液中氨氮的吸附情况,进而分析了吸附等温线、动力学和热力学特性.结果表明,爬山虎茎已经达到或超过矿物吸附氨氮的水平.氨氮吸附最适pH值为5~9.吸附过程基本在第18h达到平衡,控速步骤主要是膜扩散和粒内扩散.等温吸附符合Langmuir模型,最大吸附量在15,25,35°C下分别为3.18,4.69,5.19mg/g.热力学参数ΔG°、ΔH°和ΔS°表明,爬山虎茎对氨氮的吸附属于自发的吸热反应,且属于物理吸附.因此,爬山虎茎可以作为开发氨氮吸附剂的原材料.     

胶质芽孢杆菌、黑曲霉及与沸石联合对模拟废水中Fe~（3＋）处理研究

研究沸石、胶质芽孢杆菌（Bacillus mucilaginosus）、黑曲霉（Aspergillus Niger）、胶质芽孢杆菌与沸石联合以及黑曲霉与沸石联合对模拟废水中Fe3＋的吸附等温曲线,分析它们对Fe3＋模拟废水的吸附及絮凝作用。结果表明：沸石对Fe3＋吸附作用符合Freundlich方程;胶质芽孢杆菌分泌含有—OH和COO-的胞外多糖,对Fe3＋具有较好的吸附效果;沸石与胶质芽孢杆菌联合对模拟废水中Fe3＋的处理,低浓度以沸石对Fe3＋的吸附为主,加入胶质芽孢杆菌絮凝剂使吸附了Fe3＋的沸石进行絮凝沉降,吸附等温曲线符合Langmuir吸附等温方程,高浓度两者共同作用使吸附量增加;黑曲霉对Fe3＋的吸附符合BET吸附等温方程;沸石与黑曲霉两者共同作用对Fe3＋模拟废水吸附等温曲线为直线。通过去除效果对比分析可知：胶质芽孢杆菌既有吸附又有絮凝功能;胶质芽孢杆菌絮凝剂无论是对Fe3＋的吸附还是对吸附Fe3＋沸石的絮凝都比黑曲霉对Fe3＋处理效果好;胶质芽孢杆菌和一些非金属矿物复合处理污染废水是一种无毒、低成本环保的处理方法,本研究将为它们在工程中的应用提供实践依据。     

Tylosin Sorption to Silty Clay Loam Soils,Swine Manure,and Sand

The objectives of this study were to assess sorption and desorption of tylosin, a macrolide antimicrobial chemical used in swine, cattle, and poultry production, in three silty clay loam soils of South Dakota and compare soil sorption to sand and manure sorption. The silty clay loam soils, from a toposequence in eastern South Dakota, standardized sand samples, and swine manure were used in 24-h batch sorption studies with tylosin concentrations ranging from 25 to 232 μ mole/L. Desorption from soil was conducted over a four-day period. Partition coefficients, based on the Freundlich isotherm (K _f ) or K _d values, were calculated. K _f values for the silty clay loams were similar, not influenced by landscape position, and averaged 1350 with isotherm slopes ranging from 0.85 to 0.93. K _f values for sand were dependent on solution/sand ratios and pH, ranging from 1.4 to 25.1. K _d values of manure were dependent on the solution type and ranged from 840 L/kg with urine to about 175 L/kg when sorbed from water. Desorption of tylosin from each soil over the four-day period was < 0.2% of the amount added. The soils' high K _f values and low desorption amounts suggest that once tylosin is in these soils, leaching to lower depths may not occur. However, this does not preclude runoff with soil eroded particles. If tylosin reaches a sand aquifer, through bypass flow or other mechanism(s), movement in the aquifer most likely would occur.     

灭草松在腐殖酸上的吸附及其机理

通过吸附动力学、吸附等温线和IR，ESR技术，研究了腐殖酸对灭草松的吸附及吸附机理，并且对pH、离子强度对吸附过程的影响进行了探讨。结果表明灭草松在腐殖酸上经过大约4h的初始快速阶段，此后进入慢速吸附过程。溶液pH可能会影响腐殖酸的构型。高pH时，吸附量随溶液离子强度增加稍有增加。灭草松在腐殖酸上的吸附过程中存在氢键、电荷转移作用，疏水分配也是可能存在的机理。     

Comments on "Ion adsorption components in liquid/solid systems"

Recently, Wu et al. (J Environ Sci 18(2006) 1167-1175) published a paper entitled as above. In the paper, the authors proposed a plotting method for describing adsorption isotherm, where adsorption density (q e) was plotted against the ratio of equilibrium concentration/particle concentration (Ce/W0) rather than (Ce) as traditionally defined. The authors claimed that this plot can eliminate the "particle concentration effect" (i.e., adsorption isotherm declines with increasing particle concentration), which may otherwise be inevasible with traditionally defined adsorption isotherms. We think that their conclusion is conceptually flawed and the plot may cause substantial inconstancy problems in practice.     

Dye removal from wastewater using the adsorbent developed from sewage sludge

Introduction Adsorptionisrelevantinenvironmentalpollutionandprotectionwithreferencetowaterandwastewatertreatment(Bowen,1992).Toxicmaterials,hazardousionsanddyes fromindustrialeffluentsbythewayofadsorptionareofgreatsignificantinconnectionwithenvironmentala…     

Biosorption of Direct Black 38 by dried anaerobic granular sludge

The biosorption of Direct Black 38 by dried anaerobic granular sludge in a batch system under specific temperatures and initial pH was investigated. The adsorption reaction is pH dependent with higher removal at low pH. The adsorption equilibrium data fit very well with both Langmuir and Freundlich models in the concentration range of Direct Black 38 at all chosen temperatures. The adsorption parameters show that the adsorption of Direct Black 38 is an endothermic and more effective process at high temperatures. The kinetics of adsorption was found to be second order and adsorption rate constants increased with increasing temperature. Activation energy was determined as 26.8 kJ/mol for the process. This suggests that the adsorption of Direct Black 38 by dried anaerobic granular sludge is chemically controlled.