Diffusion and leachability index studies on stabilization of chromium contaminated soil using fly ash

• Published in: Journal of hazardous materials Vol. 297; pp. 52 - 58
• Main Authors: Kanchinadham, Sri Bala Kameswari, L.M., Narasimman, Pedaballe, Vihita, Kalyanaraman, Chitra
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30-10-2015
• Subjects: Calcium Compounds - chemistry; Calcium polysulfide; Chromium; Chromium - analysis; Chromium - isolation & purification; Coal Ash - chemistry; Compressive Strength; Contamination; Environmental Restoration and Remediation - methods; Fly ash; India; Leachability index; Leaching; Models, Chemical; Reduction; Soil (material); Soil Pollutants - analysis; Soil Pollutants - isolation & purification; Solidification and stabilization; Solubility; Stabilization; Sulfides - chemistry; Toxicity Characteristic Leaching Procedure; Waste Management - methods; India; Chromium; Leachability index; Toxicity Characteristic Leaching Procedure; Solidification and stabilization; Calcium polysulfide
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2015.04.045

•Reduction followed by S/S using FA is an effective treatment option.•Effective diffusion coefficient was between 2.04×10−11 and 9.03×10−11cm2s−1.•Leachability index was between 8 and 9.•Characteristic compressive strength was between 24.47 and 40.49kg/cm2.•To transform the laboratory studies to field implementation this data is useful.
Experiments were performed to establish a feasible treatment process for the solidification and stabilization (S/S) of soil contaminated by leaching of Cr(VI) from Chromite ore processing residue (COPR). Reduction of the highly mobile Cr(VI) was performed using calcium polysulfide (CaS5) with a dosage of 3 times the molar stoichiometric ratio for the initial concentration of Cr(VI) present in the chromium contaminated soil (CCS). The CCS was solidified and stabilized (S/S) using fly ash (FA) in various proportions i.e., 1:1, 1:2, 1:3 (FA: CCS) with and without using reducing agent i.e., CaS5. Leachability tests such as Toxicity Characteristic Leaching Procedure (TCLP) and semi-dynamic long term leachability tests indicated that the CaS5 was effective in reduction of Cr(VI) followed by the S/S process. Leachability Index was derived from the results of the semi-dynamic long term leachability tests and was between 8 and 9, indicating that FA is an effective treatment for disposal into secured landfills for CCS. The characteristic compressive strength of the CaS5 treated CCS with FA mortar blocks were between 24.47 and 40.49kg/cm2. Considering the cost of CaS5 and FA, a total expenditure of Rs. 7826 i.e., US $ 130.4 would be required for remediation of one tonne of CCS.