Enhancements of mixed surfactants on Wucaiwan coal biodegradation by Nocardia mangyaensis

Abstract

The use of surfactant to enhance the efficiency of coal biodegradation is a promising technology. In this paper, the effects of nonionic-anionic mixed surfactants TR-LAS and TW-LAS on Wucaiwan coal degradation by Nocardia mangyaensis (N. mangyaensis) were investigated, in which TR (octyl phenoxy poly ethoxy) and TW (polysorbate) were nonionic surfactants, and LAS (sodium dodecyl benzene sulfonate) was anionic surfactant. The results demonstrated the enhancement order of surfactant was TR-LAS > TW-LAS > TR > TW > LAS, and when the total mass of TR-LAS was 1000 mg/L and its ratio was 1200:800 (m/m), and the maximum biodegradation rate of Wucaiwan coal was 74.8% which increased by 23.6% than the control group (without surfactant). It was also found that nonionic surfactant TR was more effective than TW and LAS in promoting the growth of N. mangyaensis, meanwhile anionic surfactant LAS was more effective than TR and TW in increase the zeta potential of oxidized coal. The increase of bacterial growth will secrete more coal-degrading alkaline protease, and the increase of coal zata potential will make bacteria and coal contact easier, both of the above actions are conducive to biodegradation of coal. Thus, the mixed surfactants TR-LAS (1000 mg/L) achieved the strongest synergistic effect of nonionic and anionic surfactants, greatly promoting the biodegradation of coal. This study provides valuable information in designing the mixed surfactant to improve the efficiency of coal biodegradation process.