Iron-carbon Micro-electrolysis Catalytic Oxidation - Flocculation To Remove Arsenic From Copper Smelter Wastewater

Copper smelting wastewater is typical toxic and harmful waste of high-arsenic, high-acid and high heavy metal, especially, arsenic is difficult to remove. Now, many deals with arsenic are precipitation which is difficult to reuse, and some low-concentration wastewater is difficult to measure up. The experiment uses micro-electrolysis-bed to catalytic oxidized As(III) to As(V), which is composed by invalid iron scrap and activated carbon, and pass into the air. So that the cations in solution, in particular of the oxidized Fe and As(V) are combined into sediment, which is easier to remove.Copper smelting waste water are complicated. In order to exclude the interference of other ions, a separate study about the effects of micro-electrolysis to arsenic in solution was study, that was to prepare solution with AS2O3 simulating arsenic concentration of actual waste water. For the simulated wastewater study's conclusions were as follows:①conditional experiments concluded that under the condition of iron-carbon ratio.1:1.5, iron and arsenic ratio 25:1, aeration time 1.5h, reaction pH 4, can educe the best arsenic removal efficiency. The best arsenic removal efficiency was 33.15%;②through the contrast of direct flocculation and micro-electrolysis flocculation, it concluded arsenic in the solution was removal by micro-electrolysis;③by varying the reaction conditions, it can obtained the activated carbon's adsorption was excepted, the impact of micro-electrolysis for the removal of arsenic in solution was still obvious;④interference of ion experiment proved that simulated wastewater by adding Fe2+/Fe3+, Cu2+and Zn2+had little effect on the micro-electrolysis, but conducive to flocculation, therefore, the efficiency of arsenic was higher than that without metal ions; simulated wastewater by adding Pb2+significantly promoted micro-electrolysis'reaction, in addition to greatly improving the efficiency of arsenic.For the copper smelter wastewater, conclusions were as follows:①Conditional experiments prove that iron-carbon micro-electrolysis flocculation treatment of copper smelting wastewater under the condition of iron-carbon ratio 1:2, iron and arsenic ratio 60:1, aeration time 2h, reaction pH 3, flocculation pH 9, result was better than others;②Two stages of micro-electrolysis and flocculation's efficiency of removal of arsenic, respectively were 68.01%and 99.85%, which were higher than the direct regulation, proving the role of micro-electrolysis; Study using lime to adjust the effect of micro-electrolysis'pH, the result was 0.60mg/L, which is a certain guiding role about the practical application;③Changing the micro-electrolysis'conditions, direct aeration, adding activated carbon and aeration, adding iron filings and aeration were tested respectively, and iron-carbon micro-electrolysis treatment was proved good results;④iron filings and activated carbon can be re-used four times, and the arsenic removal efficiency gradually increased, which proved that micro-electrolysis played the role of catalytic oxidation. After the fifth time, iron-carbon losed their the role of original batteries;⑤The arsenic removal efficiency of regenerated activated carbon for micro-electrolysis was somewhat less efficient than fresh activated carbon, the concentration of arsenic in solution was 0.56 mg/L.⑥Treatment of iron-carbon micro-electrolysis flocculation disposed another manufacturer of low concentrations of copper smelter wastewater under the best conditions, the residual arsenic concentration was 0.36mg/L, which proved that the method was also applicable to the waste;⑦Based on the above test result, a structure of micro-electrolysis reactor and an initial set of two-stage micro-electrolysis treatment of copper smelting process were designed.By the analysis techniques of XPS, EMA, EDS and EMS to prove that:①micro-electrolysis process could catalyzed oxidation of As (Ⅲ) to As (V), as well as after micro-electrolysis the arsenic on the surface of arsenic and iron filings existed in the form of arsenate and arsenate respectively, while some metal elements on the surface of iron filings and activated carbon were involved in the process of micro-electrolysis catalytic oxidation;②The presence form and removed form of arsenic were analysed step by step. On the micro-electrolysis reaction stage the majority of arsenic was eliminated by simple arsenate and complex of iron and arsenic, which closely integrated with iron hydroxide, filtered to remove together; On the flocculation stage, the iron and arsenic formed a polymer precipitate and then removed, at the same time, hydrolysis of iron will form polymer which could remove arsenic by adsorption and netting the remaining solution of arsenic. The two ways achieved the purpose of arsenic removal, and at the same time the two polymers had the relationship of collaboration and competition. Results of the research for the copper smelter wastewater treatment offers a new idea, which were dealing with the waste problem of non-compliance, recycling copper, iron filings used in low-cost. The method has high economic and environmental benefits.