Chemical and biological regeneration of HDTMA-modified montmorillonite after sorption with phenol

Hexadecyltrimethylammonium (HDTMA)-modified montmorillonite (HMM) has recently been recognized as a potential sorbent to remove organic contaminants from environmental systems. Potential applications of this material highly depend on the efficiency of regenerating contaminant-sorbing HMM. In this study, we investigated a chemical (NaOH solution) and a biological (yeast Pityrosporum sp.) method to regenerate phenol-sorbing HMM. Our results showed that the sorption coefficient of phenol to HMM is not a linear function of the ratio of the substitution of HDTMA in HMM. Chemical regeneration of HMMs (0-0.7 times of its cation exchange capacity (CEC)) proved the existence of a phenol residual amount of about 3 mg(.)g(-1) in the HMMs tested when aqueous pH is maintained above 11. In addition, the obvious deductions in the sorption capacity of the chemically regenerated HMMs were observed after four cycles of sorption-regeneration. However, the sorption capacities of intermediate substituted HMMs (0.3-0.7 CEC) can be completely restored by bioregeneration with yeast for extended cycles of reuse. The results imply that the bioregeneration method with yeast could be a promising technique for in-situ bioremediation of phenol-contaminated groundwater in the subsurface or for treatment of phenol containing wastewater.