Hydroxypropyl-beta-cyclodextrin enhanced electrokinetic remediation of sediment contaminated with HCB and heavy metals

Abstract

This work aimed to evaluate hydroxypropyl-beta-cyclodextrin (HPCD) enhanced electrokinetic (EK) remediation of aged sediment contaminated with hexachlorobenzene (HCB) and heavy metals (Zn and Ni) in bench-scale. Deionized water, 5 and 20% HPCD were used as anodic flushing solutions, respectively, with constant voltage gradient of 1.0 V cm(-1). The experimental results showed that HCB migration and removal from sediments was significantly affected by HPCD concentrations and cumulative electroosmotic flow (EOF). In test with deionized water, only 7% of HCB was removed with 4.0 pore volumes (PVs) of EOF, while 15-26% of HCB was removed with 2.5-4.5 PVs using 5% HPCD solution. With 20% HPCD solution, nearly 40% of HCB removal efficiency achieved with 2.6 PVs. For Zn and Ni, the mobilization was greatly dependent upon sediment pH. In all tests, heavy metals migrated from anode to cathode, and accumulated near cathode due to the high pH, with little removal efficiency. This study indicated that EK process combined with HPCD flushing and pH buffering was a good alternative for HCB removal from sediments, and other enhancement was needed for heavy metals removal.