Optimization And Mechanism Study Of Biosorption Of Cu (Ⅱ) And Pb (Ⅱ) From Aqueous Solutions By Microbial Flocculants Of MBFGA1

In recent years, with the rapid development of industry and agriculture and the growth of population, the amount of living sewage and production sewage constantly increased, and the elements in sewage become more complex. The efficient supervisory systems in sewage discharge are imperfection in the whole country at present. So it is needed to break through the bottlenecks of treating technology of complex sewage. Abundant sewage without dispose or is disqualification was discharged wantonly, which had brought a severe threat in water resource, and even threaten the life and health of public. The wastewater discharged in activities of various industrial and agricultural contains heavy metal ion, which is no biodegradable and highly toxic, and some of them can be biologically enriched and then lead to health hazard through biologic chain. Among the various heavy metal pollution incidents, Cu（Ⅱ） and Pb（Ⅱ） act as pollution sources are becoming more and more frequent. These incidents seriously influence the biological diversity and the health of human being. This suggests a need for dealing of the in sewage. At present, treatment techniques of wastewater contains Cu（Ⅱ） and Pb（Ⅱ） include chemical precipitation, ion exchange method, chemical oxidation or reduction, reverse osmosis, electroosmosis, ultrafiltration solvent extraction, and so on. But these methods have some limitations such as high treating costs, hard to control the operating conditions, easy to bring about secondary pollution, etc. While biological treatment is superior for its strong choice, high efficiency, little consumes and low cost, and is widely used in study of treatment in heavy metal sewage. The study of bio-adsorbent is usually being the focal point, but in contrast, the study of microbial flocculants is still in the initial stage, and thus it is rare in the exploration of mechanism of gathering heavy metals.In the present work,microbial flocculants of MBFGA1 was applied as DTCR to collect Cu（Ⅱ） and Pb（Ⅱ） from aqueous solution. And the adsorption performance of MBFGA1 to capture Cu（Ⅱ） and Pb（Ⅱ） was studied. Single-factor tests were applied to study the five main factors’influence such as pH, MBFGA1 dosage, CaCl₂ concentration, speed of stir and time of stir. And the Box-Behnken design （BBD） methodology was employed to optimizing the routine of MBFGA1 with five factors: pH, MBFGA1 dosage, CaCl₂ concentration, speed of stir and time of stir in removal of Cu（Ⅱ） and Pb（Ⅱ） from aqueous solution, with the removal rate of Cu（Ⅱ） and Pb（Ⅱ） as response value. In the meanwhile, this study also investigate the relevant mechanisms of MBFGA1 in collecting Cu（Ⅱ） by FTIR. Results showed that, impact of each factor is different, and all present its own regularity. The significant factors that influence the collecting effect of Cu（Ⅱ） were MBFGA1 dosage and speed of stir, but relevantly, factor of MBFGA1 dosage was particularly evident than stirring speed. And the optimal flocculating conditions for Cu（Ⅱ） were in condition of pH 7.23, MBFGA1 24.75 mg/L, stirring speed 130.90r/min and stirring time 47.79 s, respectively, under which circumstances the actual measurement of Cu （II） was 0.08 mg/L, removal rate was more than 99.68% and the capture capacity was 303.43mg/g. The significant factors that influence the collecting effect of Pb（Ⅱ） were MBFGA1 dosage and pH, while in contrast, pH had a more obvious effect than MBFGA1 dosage. The optimal flocculating conditions for Pb（Ⅱ） were in conditions of pH 9.0, MBFGA1 33 mg/L, stirring speed 200r/min and stirring time 120 s, respectively, when the actual measurement of Pb （Ⅱ） was 0.05 mg/L, and MBFGA1 achieved a removal rate of 99.8%. Finally, the removal mechanism was discussed by combined with FTIR images result, and found that chemical groups in MBFGA1 such as the hydroxyl, carbonyl, ethanoly, C-O-O and aromatic nucleus play an important role in adsorbing Cu （Ⅱ） and Pb （Ⅱ）. Chemical effect is dominate and physical is subsidiary in removing Cu（Ⅱ） and Pb（Ⅱ）. In this study, the results show that microbial flocculants of MBFGA1 is economically and environmentally a good absorbent in removing Cu （Ⅱ） and Pb （Ⅱ） from wastewater.