| Lead and zinc smelting wastewater is mainly characterized by low pH, high concentration of zinc, lead, copper, arsenic, fluoride and other impurities. Its component is complicated and treatment process is very difficult. Currently, the main treatment method of lead and zinc smelting wastewater is lime precipitation; this method generates a large number of hazardous waste sediments, which are difficult to be recycled, and the hardness of water is too large to reuse. Fe-C micro-electrolysis can be used to treat wastewater containing some heavy metal ions by catalyzed oxidation reduction and flocculation precipitation of ferrite, but there are some problems of easy hardening and low reactivity. In this paper, we design and prepare a kind of enhanced micro-electrolysis functional material using direct reduction sponge iron production process and carbon pellet production technology, and use this material to treat lead and zinc smelting wastewater and achieve good results.In the preparation experiments, enhanced micro-electrolysis material was prepared using iron ore and coal as raw materials for the purpose of improving metallization and the activity of Fe-C micro-electrolysis. The optimum preparation conditions are coal blending 35%, iron ore particle size 140 mesh, reaction temperature 1140℃, reaction time 12 min. In this material, the metallization is 92.35%, iron content is 60%, and carbon content is 13%, density is 1.82 g/cm3, compressive strength is 0.22 kN/cm3, direct reduction iron and carbon are equally distributed and combined tightly.Simulated and actual lead and zinc smelting wastewater were treated by aerated micro-electrolysis flocculation using prepared material. The results showed that the optimum removal conditions were initial pH 3.0, material particle size 60 mesh, the amount of micro-electrolysis material 20 g/L, reaction time 30 min and flocculation pH 8.0 for the simulated wastewater of 100 mg/L Pb2+. The removal efficiency of Pb2+ was 99.88%. For the simulated wastewater of 150 mg/L Zn2+, the optimum removal conditions are the same as above except reaction time 40 min. The removal efficiency of Zn2+ was 99.75%. For the actual wastewater containing Pb2+ and Zn2+, the integrated optimal removal conditions were initial pH 3.0, material particle size 60 mesh, the mount of micro-electrolysis 30 g/L, reaction time 40 min. In the stage of micro-electrolysis the removal efficiency of Pb2+, Zn2+ and total arsenic was 98.87%,77.89%, and 47.26%, respectively. After effluents were treated by flocculation at pH 9.0, the removal efficiency of Pb2+, Zn2+ and total arsenic was 99.90%,99.67%, and 98.74%, respectively.The material treated by micro-electrolysis and floc treated by flocculation were analyzed by scanning microscopy (SEM), energy disperse spectroscopy (EDS), and X-ray diffraction (XRD). The reaction mechanism was studied by analysis of SEM, EDS, XRD, and, combined with corrosion cell principle, characteristics of pollutant of wastewater, equilibrium theory of heavy metal ions with water hydroxyl ions, co-precipitation of iron and the hydroxyl polymer, and adsorption theory.Compared with iron scrap method and common iron-carbon method, enhanced micro-electrolysis treating lead and zinc smelting wastewater had the advantages of good treatment efficiency, small amount of enhanced material, short reaction time, a large range of pH value, un-hardening and so on, achieving the object of designing. In this study, we had done a useful exploration in order to solve the pollution problem of heavy metal in the refining wastewater and opened a new road of treating refining wastewater. |
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