Biosorption Of Cu²⁺ And Cd²⁺ By Bacillus Subtilis From Aqueous Solution

The tolerances and biosorption characteristics under different culture and adsorption conditions of Bacillus subtilis to Cu2 +and Cd2+were investigated in this experiment. And the Bacillus subtilis was acclimated in medium with different concentration gradients of Cu2+ and Cd2+to improve its adsorptive capacity.The Bacillus subtilis cultivated for 24 hours was inoculated to mediums containning different concentrations of Cu2+ and Cd2+, then the OD660 were measured. The results showed that the tolerance of Bacillus subtilis to Cu2+, Cd2+ were 20～30mg·L-1 and 40～50mg·L-1, respectively.The culture conditions results of Bacillus subtilis showed that better adsorption capacity was got when the beefextract was 5g·L-1; the peptone was 6g·L-1; the glucose was 15g·L-1; the pH value was 6.15; the temperature was 30℃; the time was 48 hours. Several factors such as time, temperature, pH value, concentration of biomass on the biosorption capacity of Bacillus subtilis were studied.Results indicated that biosorption efficiency reached 93.87% and 99.64% when the concentration of Cu2+, Cd2+ were 20mg·L-1 and 30mg·L-1; the pH value were 5.25 and 6.25; the concentration of biomass were 35g·L-1 and 45g·L-1; the time was 2 hours; the temperature was 30℃, respectively. The biosorption efficiency of Bacillus subtilis to Cu2+, Cd2+ was differently improved 28.52% and 19.09% after the culture and adsorption conditions were modified.The Bacillus subtilis was acclimatized and then studied the influence of temperature, pH, time, biomass, concentration of heavy metalions towards the adsorption of Cu2+, Cd2+ by acclimatized Mycobacterium phleicombined with single factor experiment and orthogonal design. The orthogonal design results showed that when the concentrations of Cu2+, Cd2+was 40mg·L-1 and 60mg·L-1; pH value were 5.75 and 6.25; adsorbent mass were 35g·L-1 and 40g·L-1; adsorption time was 2.5 hours and 2.0 hours; temperature was 30℃, the biosorption efficiency reached 99.44% and 99.92%, respectively. Compared with original strain, the biosorption efficiency of acclimated strain to Cu2+, Cd2+ increased by 34.43% and 19.33%, respectively. And analysis of variance showed that the effect of all factors on biosorption were in the order of pH value> biomass concentration> temperature> time, and pH value was the most significant.Bacillus subtilis pretreated with different agents has different effects on the biosorption of Cu2+, Cd2+ and alkali can enhance their biosorption efficiency. The desorption experiments showed that acid has better desorption effect especially sulfuric acid and the bacteria can be recycied used.