Decrease in hydrophilicity and moisture readsorption of Manglai lignite using lauryl polyoxyethylene ether: Effects of the HLB and coverage on functional groups and pores

Abstract

Decrease in hydrophilicity of lignite and moisture readsorption after adsorption of a series of lauryl polyoxyethylene ether (C12(EO)n) were studied with the measurement of wetting heat and moisture readsorption ratio. Effect of the hydrophilic lipophilic balance (HLB) of C12(EO)n on efficiency of the decrease in lignite hydrophilicity was investigated. X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption/desorption were used to disclose the coverage characteristics of the different functional groups and the aggregations in pores of lignite by the adsorbed surfactant. Results indicated that both wetting heat and moisture readsorption ratio of lignite decreased significantly using different C12(EO)n. The size order of wetting heat of lignite after adsorption of different C12(EO)n with variation of the HLB values were almost consistent with that of moisture readsorption. The low HLB values of C12(EO)n especially with HLB of around 13.62 and 12.49/9.75 are most efficient respectively for the decrease in wetting heat and moisture readsorption of lignite. Coverage of oxygen-containing groups by surfactant was mainly devoted to the decrease in hydrophilicity of lignite. Among those oxygen groups in lignite surface, the COO/COOH and C-O/OH were responsible for adsorption priorities. Aggregations of surfactant in pores were beneficial for decreasing moisture readsorpiton of lignite surface due to the decreased storing space of moisture.