Adsorption characteristics of sulfate reducing bacteria Clostridium sp. on lignite surface.

Biogenic coal bed methane has attracted great attention in recent years. During the process of biogas production, the interaction between microorganisms and coal is a crucial step. Sulfate-reducing bacteria (SRB) play an important role in biogas production. However, the interaction between SRB and coal has always remained an open problem. In the present work, the SRB strain Clostridium sp. and lignite were used to investigate the adsorption process with the extended DLVO (XDLVO) theory, calorimetry, and scanning electron microscopy (SEM). The results showed that the adsorption rate has a positive correlation with pH when it went from 3 to 8. XDLVO theoretical analysis was in good agreement with the adsorption experimental result. Acid-base potential energy is a more critical factor driving the adsorption comparing with electrostatic potential energy and Lifshitz-van Der Waals potential energy. The adsorption process of Clostridium sp. cells on lignite surface can be divided into three main stages: the direct adsorption, or reversible adsorption; desorption process; and irreversible adsorption. From the SEM results, the intercellular cohesion is also a very important adsorption form. The morphology and roughness of coal surface may also have a key effect on adsorption. Overall, our results provide some insights into the surface energy changes of Clostridium sp. adsorbed on coal and their interactions from the perspective of adsorption kinetics.