The role of surfactants in coal bio-solubilisation

The interaction between coal, surfactants and enzymes was studied in this paper in order to investigate the role of surfactants in coal bio-solubilisation. The results showed that in the absence of the surfactants, limited enzymes were adsorbed onto the coal surface (< 0.5 mg/g, enzyme/coal), and then the coal bio-solubilisation occurred to small extents. Under these conditions, the extents of coal bio-solubilisation, characterized by the absorbance of reaction media at 450 nm, were all less than 0.1 (A450nm < 0.1). But, in the presence of the surfactants, the adsorption of the enzymes onto the coal greatly improved (8.2 mg/g, enzyme/coal), leading to relatively high bio-solubilisation extents (A450nm = 0.65). The main mechanism was that the surfactants modified the charges and the hydrophilic property of the coal surface such that more enzymes can contact and solubilise the coal. Therefore, during coal bio-solubilisation, surfactants mainly promoted the adsorption of enzymes onto coal to improve coal bio-solubilisation, rather than solubilised coal directly. ► Interaction between coal, surfactants and enzymes during coal bio-solubilisation. ► Without surfactants, limited enzymes were adsorbed onto coal surface. ► With surfactants, the adsorption of enzymes onto coal improved. ► Surfactants modified the charges and the hydrophilic property of coal surface. ► By promoting the adsorption, surfactants improved coal bio-solubilisation.