活性炭对乙腈-水溶液中新型POPs六溴环十二烷的吸附

Adsorption of a new POPs hexabromocyclododecane in acetonitrile-water solutions by activated carbon

选用活性炭作为吸附剂,研究了新型持久性有机污染物六溴环十二烷(HBCD)在乙腈-水溶液中的吸附行为.结果表明,活性炭的投加量(0.2—2 g·L-1)、HBCD初始浓度(0—60 mg·L-1)及溶液中乙腈的比例(40%—100%)对吸附效果产生显著影响;吸附动力学分析表明活性炭对HBCD的吸附速率受颗粒内扩散过程控制;通过对比Langmuir、Freundlich和Sips模型发现Sips模型更适于描述在0.05 g·L-1的活性炭投加量,HBCD初始浓度为0—60 mg·L-1的条件下,HBCD在乙腈溶液中的吸附过程,且呈现出S型吸附等温线特点,说明在吸附剂表面可能存在较强烈的竞争吸附;通过Sips模型求得的饱和吸附容量为62 mg·g-1;在40%—100%的乙腈比例下,吸附量随着乙腈比例的提高而线性降低.在活性炭投加量为0.05 g·L-1,HBCD初始浓度为5 mg·L-1条件下,获得平衡吸附量随乙腈浓度(40%—100%)变化的回归方程,并且估算乙腈比例为0%情况下,HBCD的平衡吸附量为127.35 mg·g-1.

In this work, activated carbon （ AC ） was selected as the adsorbent to investigate the adsorption behavior of one of the new persistent organic pollutants, hexabromocyclododecane （ HBCD） , in the acetonitrile-water solution. Results showed that the adsorptions were affected significantly by the dosages of AC （ 0. 2 g·L^-1—2 g·L^-1 ） , initial concentrations of HBCD （ 0—60 mg·L^-1 ） and proportions of acetonitrile （ 40%—100%） . The adsorption kinetics analysis showed the rate of adsorption of HBCD was controlled by the inner-sphere diffusion in AC. Langmuir, Freundlich and Sips models were used to fit the adsorption isotherm respectively. In the presence of 0.05 g·L^-1 of AC and 0—60 mg·L^-1 of initial concentrations of HBCD, the Sips model can better describe the adsorption process in acetonitrile solution which has the S type isotherm and implied the existence of strong competition of adsorption on the surface of AC. The saturated adsorption capacity is 62 mg·g^-1 via Sips model. The adsorption capacity decreased linearly as the proportion of acetonitrile over the range of 40% to 100%. The regression equation of equilibrium adsorption capacity that varies with acetonitrile concentrations （ 40—100%） was obtained in the presence of 0-05 g·L^-1 of AC and 5 mg·L^-1 of initial concentration of HBCD, and the equilibrium adsorption capacity for HBCD was speculated as 127. 35 mg·g^-1 under the acetonitrile proportion of 0%. This work provides the basis for removing HBCD from water by AC.