This paper describes activated carbon block filters prepared by extrusion for water purifier. The specific surface area of the activated carbon blocks affecting the properties of a polymer binder were investigated. Polyethylene (PE) particles were used as a binder polymer and the effect of particle sizes on changes in the specific surface area of activated carbon blocks in addition to the adsorption properties of chloride anion in the aqueous solution were investigated. The sizes and shapes of PE particles were measured using SEM. The specific surface area of activated carbon was $1186m^2/g$. The specific surface area of PE binder was $444m^2/g$ and $940m^2/g$ with the particle sizes of $200{mu}m$ and $20{mu}m$, respectively. In order to verify the performance of the filter, chlorine adsorption experiments were conducted.