Adsorption studies on coir pith for heavy metal removal

Biosorption efficiency of coir pith, a waste product from coir industry, was investigated in this study for the removal of metallic pollutants such as Ni, Cu and Zn from aqueous solutions. The disposal of coir pith is a major problem associated with the coir industries, especially working in the small-scale sector. The present study explores the effectiveness of utilization of coir pith, an accumulating waste, as a biosorbent for heavy metal removal. Batch mode studies were done to evaluate the efficiency of removal of metals under varying adsorption conditions of pH, metal concentration and contact time. Characterization studies of the biosorbent and SEM analysis were done. Kinetic modelling studies were tried using Lagergren pseudo-first-order and second-order models. Equilibrium studies were done using well-known Freundlich, Langmuir and D–R isotherm models. It was found that all isotherms are fitting well indicating the efficiency of coir pith as an adsorbent of heavy metals. The applicability of all the three isotherms to the sorption processes shows that both monolayer adsorption and heterogeneous energetic distribution of active sites on the surface of the adsorbent are possible. Due to the abundance and low cost of these materials, adsorption technologies developed can act as good sustainable options for the future in heavy metal removal from industrial effluents.     

聚丙烯酰胺和椰糠配合对绿地土壤换填介质渗、蓄、净的效果

绿地土壤换填介质性能对海绵城市雨水径流源头削减起着至关重要的作用。为解决西咸新区海绵城市绿地土壤换填介质(土∶沙∶椰糠=4∶4∶2,体积比)去污性能不佳和椰糠遇水漂浮的问题,通过设置不同质量浓度(0.00%、0.50%、0.75%、1.00%、1.50%)的聚丙烯酰胺(polyacrylamide,PAM)溶液与换填介质进行混合,测定其饱和导水率、饱和含水量、全氮(TN)、全磷(TP)、化学需氧量(COD)以及重金属铜(Cu)、锌(Zn)和镉(Cd)静态吸附效果。结果表明:与不添加PAM处理相比,用量为0.75%、 1.00%、1.50%(质量分数)的PAM处理,介质的容重分别显著降低了9.1%、10.8%、12.2%;用量为1.00%、1.50%的PAM处理,介质的饱和含水量分别显著增加了24.3%、30.0%;用量为1.50%的PAM处理,介质的饱和导水率显著提高了52.6%;不同处理对TN和COD的吸附效果没有显著影响;与对照相比,用量为0.75%、1.00%、1.50%的PAM处理,滤液中磷的含量分别显著增加了20.1%、31.3%、51.1%;PAM的添加增加了介质对Cu、Zn和Cd的吸附。总之,用量为1.50%的PAM处理对于介质容重、饱和含水量、饱和导水率及对污染物(TN、COD、Cu、Zn、Cd)的静态吸附效果方面表现最优,因此推荐1.50%的PAM与土∶沙∶椰糠(4∶4∶2)配合可作为西咸新区绿地土壤换填介质。     

硼掺杂介孔炭吸附四环素的效能与机制

以椰壳和硼酸为原料,通过简单的一步热解法制备出新型硼掺杂椰壳介孔炭材料（B-CSC）用于水中四环素类污染物的高效吸附去除.系统研究了关键制备条件热解温度和硼碳质量比对其吸附性能的影响,使用比表面积及孔径分析仪（BET）、场发射扫描电镜（SEM）、X射线光子能谱仪（XPS）、拉曼光谱仪（Raman）以及Zeta电位仪（Zeta）对其微观结构及物化性质进行了表征分析.系统考察了初始pH值、不同金属阳离子以及不同背景水质条件对其吸附效果的影响.结合材料表征与相关分析等对其强化吸附机制进行了深入讨论与分析.结果表明,一步热解能够将硼掺入椰壳炭的表面及晶格,导致其拥有更大的比表面积和孔体积,引入硼的形态主要是H₃BO₃、B₂O₃、B和B₄C.B-CSC对四环素的吸附量达到297.65 mg·g^-1,是原始椰壳介孔炭（CSC）的8.9倍.同时,B-CSC对于水环境中常见污染物罗丹明B（RhB）、双酚A（BPA）和亚甲基蓝（MB）的吸附量分别高达372.65、255.24和147.82 mg·g^-1.B-CSC对四环素的吸附过程是物理化学作用共同主导的,主要涉及液膜扩散、表面吸附、介孔与微孔内扩散和活性位点吸附,H₃BO₃是其主要吸附位点.吸附强化机制主要是硼掺杂降低了其碳网络的化学惰性,增强了其与四环素分子的π—π相互作用和氢键作用.