水中高氯酸根的颗粒活性炭吸附过程及影响因素分析

通过批量实验研究了颗粒活性炭(GAC)对水中高氯酸根(ClO-4)的吸附特性,考察了pH、ClO-4初始浓度和共存阴离子对吸附作用的影响,并分析了吸附动力学和等温吸附模型.结果表明, GAC对ClO-4的吸附容量在碱性条件下减小,随初始浓度升高而增大,共存阴离子与ClO-4在GAC上存在竞争吸附,其影响顺序为SO2-4 > NO-3 > CO2-3 > H2PO-4 > BrO-3≈Cl-. ClO-4在GAC上的吸附最符合准二级动力学模型,吸附中存在大孔扩散过程,且孔扩散可能为GAC吸附ClO-4的主要速率控制步骤.试验浓度范围内吸附过程符合Langmuir、Freundlich和Tempkin 3种等温吸附模型,吸附过程是自发且放热的,温度升高不利于GAC对ClO-4的吸附,温度为288、298和308K时的饱和吸附容量分别为13.00、11.21和8.04 mg'g-1.说明GAC虽较易吸附水中ClO-4,但必须控制反应条件,如温度、pH和共存阴离子浓度等,以取得最佳吸附效果.

Adsorption of Perchlorate in Water by Granular Activated Carbon and Impact Factors Analysis

The adsorption of perchloric ion (ClO4-) on granular activated carbon (GAC) was studied in aqueous solution through batch experiments. The effect of pH, initial ClO4- concentration and co-existed anions on ClO4- adsorbed by GAC, adsorption kinetics and isothermal models were studied. The results show that the adsorption capacity of ClO4- on GAC decreases in the alkaline solution, and increases with the increasing initial concentration. The competitive adsorption exists between co-existed anions and ClO4- on GAC and the order of competitive effect is SO4(2-) > NO3- > CO3(2-) > H2PO4- > BrO3- approximately Cl-. The adsorption process follows pseudo-second order kinetics. The existed pore diffusion probably is the main rate-controlling step of adsorption process. In addition, adsorption of ClO4- on GAC fits the Langmuir, Freundlich and Tempkin isothermal models in the range of experimental concentration. The adsorption of ClO4- on GAC is spontaneous and exothermic, and the increase of temperature decreases the adsorption capacity. The maximum adsorption capacity is 13.00, 11.21 and 8.04 mg x g(-1) at the temperatures of 288, 298 and 308 K, respectively. Adsorption of ClO4- on GAC is favorable, but the reaction conditions, such as temperature, pH and co-existed concentration, should be controlled to improve the adsorption efficiency.