| A large number of industrial wastewater containing heavy metals caused water pollution. Industrial wastewater from electroplating, mineral processing, and oil smelting and other industries contained lead, copper, cadmium and other heavy metals. And long-term cumulative effects of heavy metals were seriously harmful to human healthy. Among them, the lead had toxic effects on plants and human health even at low concentrations. Therefore, the treatment of lead wastewater aroused extensive attention.As a new technology of lead pollution treatment, microbial adsorption method had many advantages comparing with other technologies. Microbial adsorption method was more efficient, faster and less running cost, it also could remove lead selectively, especially to lead of low concentration. Comparing with microbial adsorption method, immobilized microorganism technology was considered more efficient. It located microorganisms in the carrier, overcoming the shortcoming that the cell was small, difficult to separate from wastewater and could cause secondary pollution. It also had the advantage that reaction process was easy to control, the processing efficiency was enhanced and favorable effect of repeated using.Four bacteria strains isolated from the battery factory wastewater can tolerate lead with concentrations of 250～300 mg/L. After domestication, the tolerance of the bacteria strains to lead enhanced, and reached 400～650 mg/L. The original and the mutant yeast strains saved in my laboratory were able to tolerate 6000 mg/L and 8000 mg/L lead respectively.The effects of adsorption time (5 to 240 min), the mass concentration of immobilized particles (0.02 to 0.20 g/mL), temperature (20,30,40℃), pH value (1.0 to 10.0), rotational speed (150,200,250 r/min), initial lead concentration (10,30,50,70,100,150 and 200 mg/L) were studied using the method of sodium alginate-gelatin embedding. We found that the lead adsorption contained the fast response phase (in 30 min) and the slow reaction phase (in 30～180 min); the best temperature was 30℃; weak acid or neutral solution was better for adsorption; and immobilized particles had good effect to the low concentration of lead (≤50 mg/L). When the temperature was 30℃, rotation speed was 200 r/min, and particle mass concentration was 0.1 g/mL, the adsorption rates of the original and the mutant yeast strains to 50 mg/L lead solution pH 6.0 were 86.80% and 88.00% respectively, and little influenced by environmental changes such as temperature and lead concentration. It showed that the microorganisms with tolerance of high concentration of lead could adsorb well. |
