The Treatment Of Heavy Metal Wastewater By Electrolysis-microelectrolysis Coupled Method And Mechanism Analysis

Along with rapid economic development, the heavy metal pollution problems had become increasingly prominent, there were dozens of heavy metal contamination in recent years, specially in waste water. Heavy metal in the environment can not be decomposed destruction, but be changed of physical and chemical forms, and eventually be enriched in the body through the food chain, seriously harm to human health, meanwhile cause a great waste of resources. In order to solve the heavy metal pollution problems, a series of policies and regulations were unveiled to regulate treatment and disposal of the wastewater with heavy metal by the state. But the traditional approach with some shortcomings, just as low processing efficiency, producing large amount of miscellaneous and higher metal residues, they were hard to meet environmental requirements. Therefore, it is meaningful to explore new technologies to handle wastewater with heavy metal. This thesis was focused on handle wastewater with heavy metal by electrolysis-microelectrolysis coupled method.The experiments handled analog copper wastewater with electrolysis-microelectrolysis coupled method, investigated the affects on the reduction of treatment of different pH, electrolyte concentration, initial copper ion concentration, the operating voltage, the iron-carbon ratio and bed thickness. The results showed that:the reduction conformed first-order reaction dynamic model, the optimal electrolysis voltage of12V, the initial pH=4, the iron-carbon ratio of3:1, electrolyte concentration of0.1mol/L (Na2SO4), the initial copper ion concentration of100mg/L, and bed thickness of20mm.The experiment compared the electrolysis-microelectrolysis coupled method with microelectrolysis method, electrolysis method in capacity and efficiency. The results showed that:the apparent reaction rate constant Kobs of electrolysis-microelectrolysis coupled method was6.18times and9.88times of microelectrolysis method and electrolysis method in the same reaction conditions,2.93times and8.9times in their own optimal reaction conditions, which confirmed that the external electric field could strengthen the microelectrolysis reaction and promote reduction in fast and highly-efficient.The electrolysis-microelectrolysis coupled method was used to deal with the actual heavy metal wastewater under the optimal reaction conditions. The effluent residue concentrations of Cu、Pb、Cd、Zn were0.025mg/L,0.083mg/L,0mg/L,8.9mg/L for lead and zinc smelting wastewater. The effluent residue concentrations of Cu、Pb、Cd、Zn were0.049mg/L,0.018mg/L,0.079mg/L,0mg/L for nickel ore beneficiation drain. When the effluent of electrolysis-microelectrolysis coupled reaction was treated by flocculation and adsorption precipitation, the Cu, Cd, Zn content of final effluent are able to meet the Ⅰ class standard of surface water quality environmental, and the Pb content can reach Ⅲ class standard of surface water quality environmental.The cyclic voltammetry was used to study affect of metal ion CV curves on presence/absence external electric field. The results showed that:The external electric field can induce the reductive initial potential and peak potential shift to the positive direction, reduce the reaction activation energy and reaction overpotential, and linear relationship weaken between reduction peak current ip and (?)v on the different scan rates, it implied that the external electric field could weak the effects of ion diffusion and eliminate a certain degree of concentration polarization.The copper crystal morphology on the carbon surface was studied by SEM. The results showed that:The external electric field can promote copper crystal to be thin and tiny. it implied that the external electric field could aggravate the corrosive primary cell reaction to produce a large overpotential and current density, and finally, induce the reaction to create more crystal nucleus in order to accomplish thining of crystal.The experiment used XPS to study the change of the iron compounds binding energy under external electric field. The results showed that:The external electric field can induce binding energy of iron compounds shift to higher binding energy, and create stable iron compounds. External electric field could activate Fe2+and Fe3+, and then promote degree of polymerization of Fe(OH)2、Fe(OH)3, increase the capacity of polymer flocculation and adsorption.