Removal of haloacetic acid by adsorption on mesoporous silicates

Abstract

Haloacetic acids are disinfection by-products generated from reaction of chlorine with natural organic matter. Some of them are suspected human carcinogens such as dichloroacetic acid (DCAA). Adsorption of DCAA at low concentration was studied in batch experiment. Synthesized hexagonal mesoporous silicate (HMS) and functionalized HMSs were used to evaluate the effect of surface functional groups compared with powdered activated carbon (PAC) and activated alumina. NaY and HY zeolite were selected to evaluate the effect of crystalline structure. The results showed that physical characteristic of adsorbents did not affect DCAA adsorption capacity, except for surface charge and surface functional groups. The pseudo-second-order kinetic model provided the best correlation of experimental data compared to the pseudo-first-order model. Adsorption capacity suggested that hydrophilicity of adsorbents played more important role than electrostatic force and crystalline structure. Adsorption data were well described by Freundlich isotherm by non-linear estimation. The effects of pH and temperature were also studied. DCAA adsorption capacity was significantly affected by pH depending on pHZPC of adsorbents. DCAA adsorption capacity on PAC was decreased by increasing of temperature. The opposite result was observed on NaY zeolite. The DCAA adsorption capacity was not affected by temperature significantly for HMS and activated alumina. Therefore, DCAA adsorption capacity of HMS was less than PAC according to several interaction forces involved caused by surface complexity of PAC.