Bacteria solubilization of shenmu lignite: influence of surfactants and characterization of the biosolubilization products

The biosolubilization experiments of Shenmu lignite were carried out by four kinds of bacteria, Ochrobactrum cytisi, Novospingobium naphthalenivorans, Alcaligenes faecalis, and Pseudomonas fluorescens. The optimal conditions of coal biosolubilization were obtained by combining single-factor and orthogonal experiments, showing the coal biosolubilization rate of dominant bacterium Pseudomonas fluorescens is 53.6%. The effects of four surfactants which were SDS, LAS, Tween 80, and Triton X-100 on coal biosolubilization were studied, it is obvious for Pseudomonas fluorescens the biosolubilization rate can reach to 61.9% and the biosolubilization time has been shortened in the presence of Triton X-100. Adsorption model of surfactants on coal surface was deduced by measuring the contact angle between oxidized coal surface and surfactants solutions, and zeta potential of mixture solution of coal and surfactant. The enhancement of the hydrophilicity of the oxidized coal surface is helpful to improve the coal biosolubilization. The unsaturated compounds with low molecular weight (89-604) such as ethers, esters and the like existed in black liquid products. The carbonyl and nitryl groups in oxidized coal increased after the coal pretreated by nitric acid, while decreased in residual coal. The residual coal surface became loose and rough with corrosive morphology after biosolubilization.

Automated summary

The biosolubilization experiments of Shenmu lignite were conducted using four types of bacteria, with Pseudomonas fluorescens demonstrating the highest coal biosolubilization rate. Addition of Triton X-100 enhanced the biosolubilization efficiency of Pseudomonas fluorescens. The study also revealed that surfactants can alter the surface properties of coal, impacting the biosolubilization process.