| The wastewater containing lead not only has great harm to human, but also have great harm to plants and animals. When the wastewater containing lead enters the environment, the lead of the wastewater is constantly enriched through the enrichment of the organism and the food chain. Therefore, the human being as the top of the food chain are seriously threatened. As a result, lead wastewater treatment has the vital significance.The method of biological adsorption method and the method of biological flocculation are new, which has a broad development prospects. But microbial adsorption and flocculation mechanism are not fully understood, the application of microbial flocculant adsorption is still in its infancy. Therefore, further explore and study of the mechanism of microbial flocculation Pb(Ⅱ) adsorption., the effective chemical components of the microbial flocculation adsorption Pb(Ⅱ) perhaps could help find out the culture conditions suitable for the adsorption of heavy metal ions, improving the ability of microorganism for the adsorption of Pb(Ⅱ). At the same time, researchers must strengthen and broaden the microbial strains of adsorbent resources, and look for the microorganism of big quantity and low price which can adsorb and flocculate more various heavy metal ions at the same time. It will pose important economic and social significance upon the treatment of wastewater containing lead.A lead-resistant and flocculant produced strains was screened from Activated sludge of the sewage treatment plant in Chenggong County, Kunming, which was identified as Klebsiella by16S rDNA. The wet microbial cells were used as active adsorbent, after the drying microbial cells as an non-active adsorbent, we studied adsorption flocculation properties for water Pb(Ⅱ) in water of active and non-active sorbent. In the treatment of the wastewater containing lead, research of Klebsiella adsorption flocculation Pb(Ⅱ) under the different pH, different dosage, different time, different concentration of Pb(Ⅱ) and different speed, in order to determine the best conditions; Explored the adsorption flocculation mechanism through Adsorption isotherm curve, Kinetic models, FT-IR, SEM and XPS, the results are as follows: (1)53Lead-resistant strains were selected from Sludge,10of which can produce lead-resistant microorganisms adsorbed flocculant. And the lead-resistant strains of best flocculation characteristic was ZJ-15, whose flocculation rate on Kaolin suspension was87.93%; Sucrose of15g, KH2PO4of2g, K2HPO4of5g, MgSO4-7H2O of0.2g, NaCl of0.1g, urea of3.3g; distilled water of1000ml, pH of6.0were the best best medium components of ZJ-15lead-resistant strains producing lead-resistant microorganisms adsorbed flocculant; The optimal culture conditions of ZJ-15lead-resistant strains producing lead-resistant microorganisms adsorbed flocculant:initial pH of medium hit6.0, fermentation temperature T reached28℃; and rotation speed was100rpm; The effect that ZJ-15posed upon flocculant produced by ZJ-15:no effect for Na+、Cu2+, inhibition for Fe2+, Fe3+, Al3+, promotion for Mg2+(2) By Gram stain, observation of bacterial colony morphology and16SrDNA identification, it was found that the right ZJ-15lead-resistant strains producing lead-resistant microorganisms adsorbed flocculant was identified as Klebsiella sp.(3) When the active adsorbent treated the waste water with Pb(Ⅱ), the pH was5, the amount of adsorbent was8g/L, the time was120min, the concentration of Pb (Ⅱ) was150mg/L, the speed was120rpm, the equilibrium adsorption amount was73.3mg/g; When the non-active adsorbent treated the waste water with Pb(Ⅱ), the pH was4, the amount of adsorbent was0.5g/L, the time was120min, the concentration of Pb(Ⅱ)was150mg/L, the speed was120rpm, the equilibrium adsorption amount was73.3mg/g.(4) Adsorbent (active and inactive)’s adsorption of Pb(Ⅱ) can better fit Langmuir isotherm model, Adsorbent (active and inactive)’s adsorption of Pb(Ⅱ) mainly monolayer adsorption function; The second order kinetic model can better describe the kinetics process for Pb(Ⅱ) of adsorbent.(5) The FTIR result presented that t the main component of the adsorbent is polysaccharide and the mainly groups including hydroxyl, carboxyl and amide groups.The spectra of the unloaded Klebsiella biological adsorbent indicated strong asymmetrical stretching bands at3467cm-1(-OH groups),2923cm-1(C-H groups),1670cm-1(C=O groups),1421cm-1(COO groups) and1083cm-1C-OH stretching of carboxyl groups). This indicates thatthe physical adsorption and chemisorption occurred between the adsorbent and the Pb (Ⅱ) in the solution.(6) SEM comparative analysis was conducted before and after thallus absorbed the Pb(Ⅱ), the appearance of Klebsiella sp. before and after adsorption Pb(Ⅱ) was quite different, implying that Klebsiella sp. reacted with Pb(Ⅱ). Before absorbing Pb (Ⅱ), the adsorption flocculant were clumps shape with different sizes. But after adsorption Pb (Ⅱ), the pores became smaller, and amorphous crystals existed.(7) XPS comparative analysis was conducted before and after thallus absorbed the Pb2+, before absorbing, the Pb(Ⅱ) was absent, and the combination of the adsorption flocculant and Pb(Ⅱ) was weak, but after adsorption, the Pb(Ⅱ) appeared, and the relative strength of adsorption was obviously higher, and two peak number of the adsorption of lead appeared, showing that both active and non-active adsorption flocculant flocculant reacted with Pb(Ⅱ); After adsorption Pb(Ⅱ), the comparative analysis on the XPS spectra decomposition and the standard spectra of lead of Pb(4f5/2) and Pb(4f7/2) showed that their peaks were very similar,and the binding energy of lead was138.84eV. After analyzing by standard spectrum, it was found that the main form of lead after adsorption is Pb (Ⅱ). |
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