Research On Ferment Production And Biosorption Of Cr By Yeast Fusion Strain

The ferment production and biosorption of Cr by yeast fusion have been investigated. It indicated that the removal ratios of total Cr were over 90% when yeast dosage was 10g (water-containing was (78±2)%) at under certain conditions and the final concentrations of both Cr(Ⅲ) and Cr(Ⅵ) met Integrated Wastewater Discharge Standard (GB8978-1996). The optimal conditions for biosorption were pH≤3, contacting time 2 hours, temperature 30℃to 35℃and yeast dosage 10g.The adsorption process was in accord with Lagergren pseudo first-order kinetic regression models, Lagergren pseudo second-order kinetic regression models and article inner diffusion model, and the fitting parameters R2 were all over 0.92, which showed microbial adsorption process is such a complex process. At the optimal conditions, yeast fusion strain adsorbed Cr(Ⅵ) apparently and Cr(Ⅲ) hardly. Hexavalent chromium partly was reduced to trivalent in the adsorption process. Moreover, FTIR and SEM analysis revealed that there were such functional groups as -OH,-NH2,-PO2- and-CONH- involved in biosorption, and Cr (Ⅵ) was more toxic to yeast fusion strain.The experiment which optimized culturing conditions showed that inoculum dosage was 10% in volume, temperature 30～35℃, oxygen rich, initial pH 8, C/N 4, MgSO4 dosage 0.02～0.5g/L, culturing time 60h～72h. Comparing flask bottle and fermenter culturing, the cell growth trend was similar. However, fermentation culturing growth process had a certain lag and got less yeast.The adsorption trend was different under two reaction processes—in aeration and in flask bottle. Reaction under aeration reached saturation after 3h while in flask bottle 2h. However, the removal rates were nearly the same.Yeast fusion strain was used to deal with hardware wastewater and electroplating wastewater, and the removal ratios of total Cr was better when pH was between 1 and 3, and the optimal culturing time was 42h and 64h, which the removal ratios was 77% and 68% individually. When it comes to the comprehensive treatment effects,the results show that:fusion has good effect(92% removal rate) on adsorption of chromium, but the COD, total nitrogen, total phosphorus removal is not satisfactory(16%,22% and 5% removal rate).Desorption experiments showed that all H2SO4, NaOH, EDTA, AICl3 solution had certain effects on yeast fusion strain desorption. The effects of 2.5 mol/LNaOH solution were best and desorption rate reached 87.9%. The higher the desorption agent concentration was, the better the desorption effect was.