壳聚糖功能化的茶基水凝胶膜材料的制备及其在Pb^(2+)吸附中的应用

Preparation of chitosan-functionalized tea-based hydrogel membrane materials and their application in Pb^(2+)adsorption

为充分发挥茶渣的利用价值,以茶渣为原料,制备了4种不同性能的铅离子吸附剂.通过改变溶液pH、Pb^(2+)初始浓度、温度和吸附时间等因素探究其最佳吸附条件,并对吸附过程进行吸附热力学和吸附动力学研究.结果表明,Chitosan/Tea膜(CT膜)、PVA/Chitosan/Tea膜(PCT膜)、Chitosan/Modified tea膜(CM膜)和PVA/Chitosan/Modified tea膜(PCM膜)的最佳pH值分别为6.0、6.0、5.0和5.0;Pb^(2+)初始浓度为400 mg·L^(−1)时吸附量最大,分别为185.8、160.7、197.0、153.9 mg·g^(−1).Pb^(2+)初始浓度为20 mg·L^(−1)时吸附率最大,分别为90.1%、90.9%、91.1%和83.8%.在360 min内,吸附均可达到平衡.吸附热力学结果显示,CT膜、PCT膜和PCM膜的吸附过程符合Langmuir吸附等温线模型,属于单层吸附;CM膜的吸附过程符合Freundlich吸附等温线模型,属于多层吸附,4种膜的吸附过程均为吸热、熵增、有利的自发过程.四者的饱和吸附量分别为202.8、173.3、223.7、172.4 mg·g^(-1).吸附动力学结果显示,CT膜和PCM膜吸附速率主要受扩散过程控制,符合准一级吸附动力学模型;PCT膜和CM膜吸附速率主要受化学吸附控制,符合准二级吸附动力学模型.4种吸附膜对Pb^(2+)均具有良好的吸附能力,并且适用的酸度范围较广,使用时操作简单,回收时处理方便,具有重要的参考作用和应用价值.

This study aimed at preparing four different performance adsorbents for removal of Pb^(2+)from water in order to give full play to the utilization value of tea waste.And their optimal adsorption conditions were explored by changing the pH of the solution,the initial concentration of Pb^(2+),the temperature and the time of adsorption.The adsorption thermodynamics and adsorption kinetics of the adsorption process were also investigated.The results show that the optimal pH values of Chitosan;Tea(CT),PVA/Chitosan/Tea(PCT),Chitosan;Modified tea(CM)and PVA/Chitosan/Modified tea(PCM)adsorption films are 6.0,6.0,5.0 and 5.0,respectively.The adsorption capacities were the largest at the initial concentration of 400 mg·L^(−1),which were 185.8,160.7,197.0 and 153.9 mg·g^(−1).And the adsorption rates were the largest at the initial concentration of 20 mg·L^(−1),which were 90.1%,90.9%,91.1%and 83.8%,respectively.The adsorption can reach equilibrium within 360 min.The adsorption thermodynamic results show that the adsorption processes of CT,PCT and PCM adsorption films are in accordance with the Langmuir adsorption isotherm model and belong to monolayer adsorption;while the adsorption processes of CM adsorption film is in accordance with the Freundlich adsorption isotherm model and belongs to multilayer adsorption,the adsorption processes of all four adsorption films are heat-absorbing,entropy-increasing and favorable spontaneous processes.The saturation adsorption capacities of 202.8,173.3,223.7 and 172.4 mg·g^(-1)were obtained for the four adsorption films.Besides,the adsorption kinetic results show that the adsorption rates of CT and PCM adsorption films are mainly controlled by the diffusion process and are consistent with the pseudo-first order kinetic model;the adsorption rates of PCT and CM adsorption films are mainly controlled by chemisorption and are consistent with the pseudo-second order kinetic model.All four adsorption films have good adsorption capacity for Pb^(2+),and have a wide range of applicable acidity,simple operation in use,easy handling in recovery,large reference role and high application value.