The removal of methyl violet from dye wastewater by Pseudomonas sp.: the effect of extra- and intra-cellular substances

摘要

Sorption and degradation are considered two primary modes of pollutant removal by microorganisms, and extracellular polymeric substances have been shown to play an important role in biological processes. However, the way sorption and degradation by microorganisms work to remove refractory organic pollutants and the effects of intracellular substances remain unclear. In this study, we investigated both the removal mechanisms and the intracellular substances involved in removal of pollutants by bacteria in the system of methyl violet (MV) dye pollutant removal by Pseudomonas sp. bacteria. The results, obtained using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy analyses, acid-base titration and conductivity analysis, indicated that the MV was mainly adsorbed rather than degraded by bacteria. Moreover, various bacterial components were extracted and utilized for MV removal. We found that the major bacterial component involved in MV adsorption was the cell wall and membrane fraction, accounting for more than 80% of total MV removal. Tightly-bound extracellular polymeric substances accounted for about 10%, and there was no obvious influence of other components. Protein played the largest role in MV adsorption, and polysaccharides had no adsorption effect on MV. Furthermore, a possible mechanism of MV removal by bacteria is proposed.