Evaluation of factors affecting performance of a zeolitic rock barrier to remove zinc from water

This study examined the factors affecting the performance of zeolitic rocks as reactive media in a permeable reactive barrier (PRB) used to remediate groundwater contaminated with Zn. Serial batch kinetic and sorption tests were conducted on zeolitic rock samples under a variety of conditions (i.e., reaction time, pH, initial Zn concentration, and particle size) using Zn(NO3)2·6H2O solutions. Serial column tests were also conducted on zeolitic rock samples at various flow rates. The removal of Zn increased approximately from 20-60 to 70-100% with increasing pH from 2 to 4 and decreasing initial Zn concentration from 434 to 5 mg/L. Zn removal was not affected by the particle size, regardless of the zeolitic rock samples used in this study. The Zn removal increased approximately from 20-70 to 60-100% with increasing the cation exchange capacity (CEC) from 124.9 to 178.5 meq/100 g and increasing zeolite (i.e., clinoptilonite and mordenite) and montmorillonite contents from 53.7 to 73.2%. The results from the column and batch tests were comparable. Increasing the flow rate caused the earlier breakthrough of Zn (sorbing cation) and a rapid decrease in the concentration of Na, Ca, and Mg (desorbing cations). The hydraulic conductivities of the samples were unaffected by the particle size and mineral components.