Mechanism And Influences Research Of Immobilized Sulfate Reducing Bacteria And Treating Wastewater Containing Thallium

As the metal processing and mining gradually strengthened, a large number of wastewater containing thallium was discharged into environment that caused to environmental pollution and impaired the peoples' healthy. If the high concentration of thallium was directly discharged into the water that will lead to water pollution and thallium will be transferred to human body by the food chain and it will cause a variety of diseases. The traditional physical and chemical method in treating wastewater containing thallium were not used widely because of high cost, poor feasibility, easy to produce the secondary pollution. Nowadays, Sulfate reducing bacteria was widely applied to treating wastewater containing thallium due to the special advantages. Nevertheless, SRB in the wastewater was easily interfered by some environmental factor and it was difficult to separate, recycle and reuse so that people were constantly developing new technology in treating wastewater containing heavy metal. Biological immobilization technology had been accepted by scholars at aliens and domestics because of these advantages, which contained easy to control reaction process, good stability, high treatment efficiency and easy to realize continuous processing. Biological immobilization technology was the method by chemical or physical methods to keep the enzyme and cell in a specific area to keep its activities so as to they can be serially used by recycling.In this research, the polyvinyl alcohol and sodium alginate were used as embedding material agent to immobilized sulfate reducing bacteria and the optimal proportion of immobilized bacteria were determined by orthogonal experiment. Immobilized bacteria were used to treatment wastewater containing thallium. This paper also studied the influences of environmental conditions about treating wastewater containing thallium by immobilized bacteria and the mechanism treating thallium.This results showed that the optimal embedding proportion of immobilized bacteria were as following: the mass fractions of polyvinyl alcohol, silicon dioxide, sodium alginate, acticarbon, microbial and calcium chloride were 6%, 3%, 0.5%, 2%, 35% and 2%. Under the optimal embedding condition, the treating capacity of immobilized bacteria for thallium can reach up to 180.87mg/g, the weightlessness rate was only 23.4%. when the solution pH was 6.0, the temperature was 30?, initial ions concentration was 25mg/L, the treating capacity of immobilized bacteria for thallium in the 720 min can reach up to 221.97mg/g, far greater than the blank beads. The kinetics and thermodynamics model experiment showed that the process of immobilized bacteria treating wastewater containing thallium was consistent with the pseudo second order kinetic and Langmuir model, respectively, and the process was exothermic. The particle diffusion model in three sections of process can be a very good description of the metal ions into the bacteria in a series of physical and chemical process. Immobilized bacteria was characterized by SEM and FTIR, it was found that surface and inner of immobilized bacteria existed a large number of network structure and chemical groups, which provided a suitable environment for bacterial metabolism so that these bacteria can keep active. The main mechanism about treating wastewater containing thallium by immobilized bacteria was that sulfate ion in the solution was transformed into sulfion by sulfate reduction of bacteria. Then thallium in the wastewater can generate sulfide thallium precipitation because it was combined with sulfion. Moreover, when the sulfate ion concentration in the solution reached 200mg/L, immobilized bacteria had a maximum treating capacity(258.38mg/g) for thallium and it can primely control the toxicity of thallium.