The adsorption of methylene blue dye by deep-sea Bacillus megaterium LM-44

Bacillus megaterium LM-44, a deep-sea salt-tolerant bacterium, was used as a microbial adsorbent for the adsorption of the azo dye methylene blue (MB). The inorganic carrier silica gel and organic carrier macroporous resin were used to immobilize it. The reaction conditions of the adsorbent were optimized by the single-factor method, and the optimum reaction conditions for the free strain were the adsorbent concentration of 1.187 mg/mL, the solution pH of 9, the temperature of 25 ℃, 150 r/min, and the removal rate of MB solution of 100 mg/L by shaking reaction for 60 min was 70%, and the adsorption capacity was 153 mg/g when the MB concentration increased to 500 mg/L. The optimum reaction conditions for silica gel immobilized adsorbent were 2 g/L adsorbent concentration, solution pH of 9, temperature 25 ℃, 150 r/min, shaking reaction for 120 min to remove 98% of 100 mg/L MB solution, adsorption capacity of 49 mg/g, adsorption capacity of 500 mg/L MB solution, adsorption capacity of 192 mg/g. The optimum reaction conditions for the immobilized adsorbent of macroporous resin were 8 g/L adsorbent concentration, solution pH of 9, temperature 25 ℃, 150r/min, and 180 min of shaking reaction with 82% removal rate and 10 mg/g adsorption capacity for 100 mg/L MB solution, and 32 mg/g adsorption capacity for 500 mg/L MB solution. Bacillus megaterium LM-44 had a higher adsorption capacity than the previously identified decolorizing bacterium Bacillus sp. LM-24 and still had a better removal of high concentration wastewater. The adsorption process was studied using Langmuir and Freundlich adsorption isotherm models with kinetic functions, and the results showed that all three adsorbents fit better with quasi-level kinetics, and the adsorption of free strains fit better with Freundlich model, while immobilized adsorbents fit better with Langmuir.