活性炭对单宁酸的吸附去除性能

Performance of Activated Carbon Adsorption for Tannic Acid Removal

三卤甲烷(THMs)是水中天然有机物在氯化消毒过程中产生的对人体有致癌作用的挥发性物质,腐殖酸是生成消毒副产物的主要前驱物。活性炭能够去除水中的多种有机污染物,其中对腐殖酸的去除性能可以通过单宁酸值来表征。通过间歇试验,研究了两种活性炭对单宁酸的吸附行为,探索其对单宁酸的吸附规律。结果表明308 K时,1#炭对单宁酸的饱和吸附量较大,为616.0 mg/g。升高温度有利于两种活性炭对单宁酸的吸附,表明吸附过程为吸热过程。此外,两种活性炭对单宁酸的吸附动力学可以用Largergren伪二级速率方程很好地拟合,吸附过程是双速过程。1#炭对单宁酸的吸附速率更快,比3#炭具有更高的单宁酸吸附性能。1#和3#炭对单宁酸的吸附活化能依次分别为17.5和3.9 kJ/mol,说明1#炭的反应速率随温度的升高增加得较快,符合Arrhenius的经验方程,吸附反应速率随温度升高而加快的规律,活性炭对单宁酸的吸附可认为是化学吸附。

Trihalomethanes （THMs） are undesirable by-products of chlorine disinfection. Activated carbon adsorption is often used for organic contaminants removal. The tannic acid value is well correlated with humic acid removal efficiency. A series of experiments were performed to investigate the adsorption of tannic acid in aqueous solutions by two types of activated carbons in a batch system. The results show the higher saturation adsorption capacity （616.0 mg/g at 308 K） is observed when nutshell based activated carbon is used. The adsorption capacity increases with the increase of temperature, indicating that the adsorption of tannic acid is an endothermic process. The nutshell based activated carbon has rapid speed. The process of adsorption is the two-speed process, and can be well described by pseudo second order model. The nutshell based activated carbon is more suitable for the removal of tannic acid. The adsorption activation energy of nutshell based activated carbon and coconut shell based activated carbon are 17.5, 3.9 kJ/mol, respectively, which indicates the adsorption rate of nutshell based activated carbon increases faster. Such phenomenon obeys the Arrhenius＇ Empirical Equation, thus the adsorption of tannic acid on activated carbon may be classified as chemical adsorption.