Characterization of ultra-micropore powder activated carbon for use in removing regulated disinfection by-product precursors

Abstract

This work investigated the adsorption kinetics and adsorption isotherms of ultra-micropore powder activated carbon (PAC) for the application of disinfection by-products precursors removal from Hatyai, Songkhla, and Bangkhen, Bangkok raw water sources in Thailand. Poly aluminum chloride (PACl) was used as the pre-treatment prior to the PAC adsorption. The remaining dissolved organic carbon (DOC) after PACl coagulation at a low dose of 20 mg/L resulted in a high concentration of trihalomethanes in the pre-treated water. Three PACs with a micropore area in the range of 1189 to 1544 m2/g were employed to adsorb the remaining DOC. An equilibrium contact time of roughly 60 min was determined. The three PACs have comparable adsorption rates, ranging from 2.4 to 3.3 mg/g-h. The adsorption capacities from 17.9 to 28.4 mg DOC/g PAC were found. These values increased when the number of micropores increased. A good linear relationship between micropore area and the adsorption capacities of DOC was determined. The micropore area was the important parameter for selecting PAC to remove DOC. Doubling the PACl dosage for the pre-treatment of the water samples before PAC adsorption decreased the PAC dosage in a range from 30 % to 43 %. The isotherms could be applied to other water sources that have correlated characteristics. Using ultra-micropore PAC after PACl coagulation with controlled equilibrium concentration in terms of DOC to <1.8 mg/L could reduce trihalomethanes to lower than the World Health Organization, the Japan, and the European Union drinking water standards.