Diffusion and leachability index studies on stabilization of chromium contaminated soil using fly ash.
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 40.49 kg/cm(2). 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.
Environmental Technology Division, CSIR - Central Leather Research Institute, Adyar, Chennai 600020, Tamil Nadu, India. Electronic address: sribalak@yahoo.com.
Sri Bala Kameswari
SB
Kanchinadham
Shanmugha Arts, Science, Technology and Research Academy, Sastra University, Thanjavur 613 402, India.
L M
LM
Narasimman
Birla Instituteof Technology and Science, Pilani, Hyderabad Campus, Andhra Pradesh, India.
Vihita
V
Pedaballe
Environmental Technology Division, CSIR - Central Leather Research Institute, Adyar, Chennai 600020, Tamil Nadu, India.
Chitra
C
Kalyanaraman
D017610:Calcium Compounds / Q000737:chemistry*; D002857:Chromium / Q000032:analysis* / Q000302:isolation & purification; D060729:Coal Ash / Q000737:chemistry*; D019245:Compressive Strength; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007194:India; D008956:Models, Chemical; D012989:Soil Pollutants / Q000032:analysis* / Q000302:isolation & purification; D012995:Solubility; D013440:Sulfides / Q000737:chemistry*; D018505:Waste Management / Q000379:methods*
D017610:Calcium Compounds; D060729:Coal Ash; D012989:Soil Pollutants; D013440:Sulfides; D002857:Chromium; C074702:chromium hexavalent ion; C033907:calcium sulfide
Calcium polysulfide; Chromium; Leachability index; Solidification and stabilization; Toxicity Characteristic Leaching Procedure