균질한 매질 내 Calcium polysulfide 주입에 따른 고농도 중금속 오염지하수 정화 타당성 검토 ; Feasibility Evaluation for Remediation of Groundwater Contaminated with Heavy Metal using Calcium Polysulfide in Homogeneous media

In this study, column tests using relatively uniform Jumunjin sand media were conducted to evaluate the feasibility ofcalcium polysulfide (CaSx, CPS) in removing high concentration of Zn2+ in groundwater. The injected CPS solutionreacted rapidly with Zn2+ in artificial groundwater and effectively reduced Zn2+ by more than 99% through metal sulfideprecipitation. Since the density (d = 1.27 g/cm3) of CPS solution was greater than that of water, CPS solution settled downrapidly while capturing Zn2+ and formed stable CPS layer similar to dense nonaqueous phase liquid. Mass balance analysison Zn2+ in CPS solution suggested that CPS solution effectively reacted with Zn2+ to form metal sulfide precipitates exceptfor high groundwater seepage velocity of 400 cm/d. With greater groundwater seepage velocity, injected CPS did notcompletely dissolve at the CPS-water interface, but a partially-misible CPS layer continuously moved and reacted withZn2+ in the direction of groundwater flow. Since hydraulic conductivity (Kh) decreased slightly due to the generated metalprecipitates in the inter-pores of media, injection of CPS solution should be optimized to prevent clogging. As evidencedby both XRF and SEM/EDS results, ZnS precipitates were clearly observed through the reaction between the CPSsolution and Zn2+. Further study is warranted to evaluate the feasibility of CPS to remove high-concentration heavy metalcontaminatedgroundwater in complex and heterogeneous media. ; N ; 2