Chemical Compatibility of CMC-Treated Bentonite Under Heavy Metal Contaminants and Landfill Leachate
Carboxymethyle cellulose (CMC) is considered to enhance the chemical compatibility of bentonite in terms of hydraulic conductivity. In this study, a series of modified fluid loss (MFL) tests is conducted to investigate the hydraulic conductivity (k) of CMC-treated bentonite when exposed to heavy metal contaminant and landfill leachate. CMC content in bentonite is set at 0% (i.e., untreated bentontie) and 10% (i.e., CMC-treated). Lead-zinc nitrate mixture is selected as representative heavy metal contaminants; and calcium chloride is also used for comparison. Total metal concentrations of the chemical liquid ranged from 0 to 20 mmol/L. The result indicated that minimal change in k of CMC-bentonite is found from the MFL test; whereas the k value of untreated bentonite significantly increased with increased Pb-Zn and Ca concentration. The k value of untreated bentonite is approximately 20 times higher than that of CMC-treated bentonite for a given void ratio. In addition, it is found that the impact of landfill leachate on the hydraulic conductivity is insignificant for CMC-treated bentonite. The k of CMC-treated bentonite considerably lower than that of untreated bentonite when exposed to the leachate.
KeywordsBentonite Carboxymethyle cellulose Heavy metal Landfill leachate Hydraulic conductivity
The authors are grateful for the financial support of the National Natural Science Foundation of China (Grant No. 51278100, 41330641 and 41472258), Key Program of Natural Science Foundation of Jiangsu Province (Grant No. BE2017715).
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