Study On The Lead,cadmium Resistance Strain Screening And Its Immobilized Post-processing For Treating Lead And Cadmium Of Wastewater

Heavy metal pollutions in the environment has become more and more serious in recent years,they had a great harm on the natural environment and human being.The physical repair,chemical remediation of heavy metal pollution had been developing for years,the bioremediation was the hotspot in recent years.As a kind of microbes of bioremediation,hyperaccumulation-plants endophytes have stronger resistance and tolerance for heavy metal.It had a good effect on soil remediation contaminated by heavy metal,so it was considered appllying to treat the heavy metal polluted wastewater.But separate microbial adsorbent for heavy metal pollution of waste water was easy to cause secondary pollution on environment,and its efficiency was not high and the reusablity was low.Therefore endophytes obtained from hyperaccumulation-plants were considered for wastewater treatment of heavy metal pollution after immobilization in this study.The results are as follows:?1?This study have extracted two kinds of lead & cadmium-resistance endophytes from the hyperaccumulation-plants Solanum nigrum L&Sedum alfredii Hance,they were classified for LRE04,BRE07.By the gram staining,BRE07 was identified as gram-negative bacteria,LRE04 was identified as gram-positive bacteria.Through molecular biology identification,BRE07,LRE04 were respectively identified as Bacillus licheniformis and Bacillus nealsonii.The concentration of lead reached 600 mg/L,the cadmium tolerance limit reached 80 mg/L.?2?A new kind of adsorbent was made out with magnetic polyvinyl alcohol,sodium alginate embedding fixxing BRE07,the best preparation conditions inclued magnetic polyvinyl alcohol content 9%,sodium alginate 0.8%,microbial inoculation amount 5%,crosslinking time 20 h.The optimum adsorption conditions inclued pH 6,adsorbent dosage 0.7 g/L,initial concentration of Pb²⁺ 200 mg/L,adsorption time 12 h.Under the above conditions,the removal rate of Pb²⁺ reached 98%.Another kind of new adsorbent was made out with the modified magnetic Fe₃O₄ nanoparticles,sodium alginate fixxing endophytes LRE04.The best preparation conditions was modification of magnetic nanoparticlest 0.10%,sodium alginate 8%,microbial quantity 0.4%,crosslinking time 2 h.The optimum adsorption conditions was pH 6,adsorption time 12 h,adsorbent dosage 2.5 g/L,initial concentration of Cd²⁺ 50 mg/L.And its maximum adsorption rate could reach 96%.By scanning electron microscopy?SEM?,the results showed that two kinds of adsorbent were porous structure which was good to the adsorption.Through the comparison of fourier infrared transform spectrum analysis,the structure of two kinds of adsorbent was stable and its adsorbent surface have functional groups,they include P-O?-COOH?C=O?O-H?N-H?Si-O and so on.?3?The adsorption kinetics and isothermal adsorption process model were analyzed in this study,we found that the adsorption process of two adsorbents for heavy metal ions conformed with secondary dynamics,it was mainly chemical adsorption,and the adsorption process were mainly for the monolayer adsorption.And the adsorption of Pb²⁺ was up to 113.84 mg/g,the adsorption of Cd²⁺ was up to 13.02 mg/g.Through the fourier infrared spectrum analysis about the before and after adsorbing,the results showed that the functional groups such as P-O,C-OH,-OH,C=O,P-OH,N-H,N-OH,-COOH all had have influence on the adsorption reaction.Desorption results showed that two kinds of immobilized pellets could be efficiently adsorbed for heavy metal ions in the solution,they could effective be recycled.Thus the endophytes in the hyperaccumulation-plants applied to the low concentration of heavy metal pollution of wastewater treatment had certain feasibility,and the potential was considerable.