Study On Remediation Of Heavy Metals Pollution In The Soil By Iron Bacteria

With the rapid development of agricultural production and industrial production and using too many pesticides and fertilizers, a lager number of pollutants containing heavy metal enter into the soil by all means, which causes serious pollution. Due to heavy metals can not be degraded easily, but easy to enrich in living organism, heavy metals exceed the standard will cause serious damage to the health and survival of all living organisms. Therefore, heavy metals pollution in soil has been a prominent problem in the field of environmental protection.It was founded in the early experiments that, the iron bacteria was a kind of mineralization microbe with reinforcement effect, it can form biological sludge with adsorption in it’s growth process, and improve the properties of soil liquefaction. So it has a good utilization value by using its adsorption to deal with heavy metals pollution. In this paper, iron bacteria was used to remediate pollution by heavy metal ions such as Pb2+、Cd2+、Cu2+、 Zn2+and Cr3+. The removal efficiency of heavy metal in water and soil was studied by experiment. And remediation mechanism of bacterial was researched by the methods of scanning electron microscopy (sem), X-ray diffraction, fourier transform infrared spectrum and so on. In this research the main conclusion is as follows:(1) The results of studying iron bacteria’s physiological characteristics showed that:the iron bacteria can survival under the condition of 0.5 to 1.0 times medium concentration, temperature value of 25℃ to 35℃, pH value of 5 to 8. The results also indicated that the largest tolerant concentrations of iron bacteria to Pb2+、Cd2+、Cu2+、Zn2+、Cr3+、 were 700 mg/L、100 mg/L、 400mg/L、500mg/L、400mg/L, respectively. By domesticating, the concentrations of Pb2+、 Cd2+、 Cu2+、Zn2+、Cr3+　which iron bacteria could endure arrived at about 1000 mg/L、400 mg/L、 800mg/L、900mg/L、450mg/L, respectively.(2) The studies on the conditions of remediated heavy metal ions Pb2+、Cd2+、Cu2、Zn2+、 Cr3+ in water by iron bacteria indicated that:under optimized conditions (heavy metal ion concentrations in solution were about 200mg/L,20mg/L, 110mg/L,150mg/Land 600mg/L, the concentration of medium concentration was 1.0 times, the temperature was 30℃, and pH was 7), the maximum removal rate of bacterial strain to Pb2+、Cd2+、Cu2+、Zn2+、Cr3+ respectively arrived at about 90%/85%、83%、65% and 70%.(3) The result of simulating pollution soil bioremediation experiment showed that:after the first treatments of bacterial suspension, the contents of available Pb2+、Cd2+、Cu2+、Zn2+、 Cr3+ were decreased by 58.37%,58.37%,45.92%,50.45%,45.92%; after the second treatments of bacterial suspension, compared with the untreated soil effective state of heavy metal content were decreased by 76.04%,49.89%,68.14%,70.28%,68.14%. Of which, the removal rates of effective Pb2+ and Zn2+ in soil were more significant.(4) Results of scanning electron microscopy (SEM) analysis showed that:the surface particles of sediment generated by the bacterial strain was relatively large. After remediation of heavy metal ions, the surface of the sediments with many smaller particles,and they were the strain metabolites sink product with heavy metal ions. X-ray diffraction (XRD) analysis showed that:the sediment were mainly amorphous. The infrared spectrum(FTIR) analysis of the sediment before and after the remediation of heavy metal ions showed that:the surface of sediment generated by bacterial strain has the active groups such as hydroxyl, carboxyl, sulfuric acid and the sediments were mainly to the adsorption of schwertmannite, the combination response between heavy metal ions and these active groups was the main mechanism of bacterial strain remediating heavy metal ions. Finally, according to the sequence analysis of 16SrDNA, the strain was identified as Arthrobacter niigatensis.