Treating Waste Liquid With Precious Metal Ions With Magnetic Field-Magnetotactic Bacteria

With the fast development of electronic engineering, information industry and chemical engineering, the scope and amount of precious metal employment are found expanding yearly. The risk pollution from waste materials of precious metals are uproaring as the result of the situation mentioned.As a try to remove and enrich the precious metals, lab research is performed, aiming at the theories of adsorption and its selectivity, which is also the first step of precious recovery. In this dissertation, a novel comprehensive technology is adopted, which involves magnetic field-magnetotactic bacteria system. The treatment is discussed and probed in detail, in which the precious metal ions in waste liquid can be adsorbed and then removed in magnetic field by magnetotactic bacteria, the carrier. During the research, a double stage flowsheet of the upper mention technology is put to use for the first time. In this flowsheet, competitive adsorption of double metal system is observed, which gives firsthand data supporting the consequent research of novel recycling normal metal reinforced process.In the research, the activated sludge taken from the wastewater treatment plant is cultivated in culture medium for magnetotactic bacteria. Then the bacteria are collected in magnetic field utilizing their direction finding feature. The result indicates that 94.7% of the collected are magnetotactic bacteria. Then, adsorption of single precious metal ion is probed in detail. The optimum adsorption conditions for the precious metal ions: Pd²⁺, Au³⁺, Pt⁴⁺, Ag⁺, such as pH, temperature, biomass concentration, initial concentration of precious metal ions and time, are confirmed.Math work finds that the adsorption process in accordance with the pseudo-first order kinetic model and Langmuir isotherm.Based on the above work, the adsorption of Pd-Al,Au-Cu,Au-Cu-Ni is studied. The result indicates that the magnetotactic bacteria have the property of selective adsorption. The adsorption quantity of magnetotactic bacteria on precious metal ions is much higher than that of co-exist counterparts.Separation of magnetotactic bacteria carrying precious metal ions from waste liquid is studied using separator with paralleled wires. The result indicates that the higher magnetic field strength and the longer duration, the better separation effect. At last, the waste liquid with precious metal ions is treated by the magnetic field-magnetotactic bacteria comprehensive technology continuously under the optimum operation condition. Through two adsorption and two separation processes, precious metal ions and other metal ions are separated in sequence. Simultaneously, the liquid is purified.