改性沸石对水中微量汞的吸附性能

Characterization of trace mercury adsorption by modified zeolite

为了更好的去除水体中微量汞,研究了采用二氧化锰和壳聚糖对天然斜发沸石进行改性,着重考察了pH、温度、离子强度、Hg^(2+)初始浓度和时间对改性前后沸石吸附Hg^(2+)的影响,并研究了其吸附机理。结果表明,改性沸石受pH、温度和离子强度影响较小,在pH、温度、离子强度和初始浓度为6、25℃、0.05 mol·L^(-1)和50μg·L^(-1)时,二氧化锰+壳聚糖改性沸石(ZCM)对Hg^(2+)的去除率高达99%,符合国家饮用水标准,并且二氧化锰+壳聚糖改性沸石(ZCM)具有更好的解吸再生性。3种沸石均较好的符合Langmuir等温吸附模型和假二级动力学模型,其中改性沸石对汞的吸附主要为离子交换和表面官能团的络合作用,二氧化锰+壳聚糖改性沸石(ZCM)和壳聚糖改性沸石(ZC)饱和吸附量由1.43 mg·g^(-1)提高到5和3.3 mg·g^(-1),吸附平衡时间由10 h减少至1和4 h,为治理汞微污染地表水提供一定的理论支持。

In this experiment,manganese oxide and chitosan were used to modify natural clinoptilolite zeolites. The results show great enhancement in the absorption capacity of the zeolites. The effects of pH values,temperature,ionic strength,Hg^（2 ＋）concentration,and adsorption time on the mechanism of Hg^（2 ＋）adsorption and adsorption were investigated. The results showed that the pH,temperature,and ionic strength exert a minor effect on the mechanism of Hg^（2 ＋）adsorption by the modified zeolites. When the pH,temperature,ionic strength,and initial concentration are 6,25 ℃,0. 05 mmol·L^（-1）,and 50 μg·L^（-1）,the zeolites modified by chitosan and manganese oxide（ ZCM） could remove as much as 99% Hg^（2 ＋）. As a result,the water so obtained meets the national drinking water standards. The zeolites modified by chitosan and manganese oxide（ ZCM） show better desorption regeneration. Three types of zeolites were obtained that conform better to the Langmuir isotherm model and the second-order kinetics dynamic equation. The modified zeolites perform mercury adsorption mainly by ion exchange and complexation of surface functional groups. The saturated adsorption capacity of zeolite ZCM and zeolite modified by chitosan,i. e.,ZC,increases from 1. 43 mg·g-1to 5 mg·g-1and 3. 3 mg·g^（-1）and the adsorption equilibrium time is reduced by 10 h to 1 h and 4 h,respectively,which could provide a certain theoretical support for treating surface water slightly polluted by mercury.