Assessment of cement kiln dust (CKD) for stabilization/solidification (S/S) of arsenic contaminated soils.
A stabilization/solidification (S/S) process for arsenic (As) contaminated soils was evaluated using cement kiln dust (CKD). Laboratory-prepared slurries, made of either kaolinite or montmorillonite, and field soils spiked with either As(3+) or As(5+) were prepared and treated with CKD ranging from 10 to 25 wt%. Sodium arsenite and sodium arsenate at 0.1 wt% were used to simulate arsenite (As(3+)) and arsenate (As(5+)) source contamination in soils, respectively. The effectiveness of treatment was evaluated at curing periods of 1- and 7-days based on the toxicity characteristic leaching procedure (TCLP). As-CKD and As-clay-CKD slurries were also spiked at 10 wt% to evaluate As immobilization mechanism using X-ray powder diffraction (XRPD) analyses. Overall, the TCLP results showed that only the As(5+) concentrations in kaolinite amended with 25 wt% CKD after 1 day of curing were less than the TCLP regulatory limit of 5mg/L. Moreover, at 7 days of curing, all As(3+) and As(5+) concentrations obtained from kaolinite soils were less than the TCLP criteria. However, none of the CKD-amended montmorillonite samples satisfied the TCLP-As criteria at 7 days. Only field soil samples amended with 20 wt% CKD complied with the TCLP criteria within 1 day of curing, where the source contamination was As(5+). XRPD and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) results showed that Ca-As-O and NaCaAsO(4).7.5H(2)O were the primary phases responsible for As(3+) and As(5+) immobilization in the soils, respectively.
Moon
Deok Hyun
DH
W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA. dmoon@stevens.edu
Wazne
Mahmoud
M
Yoon
In-Ho
IH
Grubb
Dennis G
DG
D000538:Aluminum Silicates / Q000032:analysis; D001152:Arsenicals / Q000032:analysis*; D000077215:Clay; D003252:Construction Materials; D003460:Crystallization; D004391:Dust / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D008855:Microscopy, Electron, Scanning; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis*; D014961:X-Ray Diffraction
D000538:Aluminum Silicates; D001152:Arsenicals; D004391:Dust; D007202:Indicators and Reagents; D012987:Soil; D012989:Soil Pollutants; D000077215:Clay