Iron-carbon Micro-electrolysis Treatment Of Edta-cu With The Wastewater Process Research

Ethylenediaminetetraacetic acid (EDTA), as an important artificial organic multi-acid complex agent, enable to combine with various metal ions and form a water-soluble complex of high stability. Thus EDTA could prevent metal ions from precipitation and catalysis, increase the availability of metal ions from solution, and remove metal ions from the system, resulting in widely application in commercial and household detergents, bleaching process of textile and paper industries, metal plating process, food industry, medicine and agriculture. Owing to its difficulty to remove by conventional water and wastewater treatment, it is essential to develop new method to improve the treatment of EDTA-Cu containing wastewater.A novel technique based on Fe-C micro-electrolysis(FAC) to treat the organic wastewater containing EDTA or EDTA-Cu complex has been proposed in this thesis. The effects of reaction time, reaction temperature, Fe/C ratio, pH, and other factors on pollutants removal were investigated. Moreover, a reasonable explanation of the generation mechanism of hydroxyl free radicals and the relationship between hydroxyl free radicals and degradation of organic matter were presented. On the basis of the theory above, layer of iron and carbon filler were modified, using rolling electroplating method to make fine ferrous sulfate particulates covered on the activated carbon surface. Experiments were further evaluated the optimal removal efficiency under the optimal plating time and micro-electrolytic reaction time. A novel technique of wastewater treatment using Fe-C micro-electrolysis(FAC) was developed.The conclusions can be drawn as following:(1) Based on the principle of iron-carbon micro-electrolysis reaction, a set of FAC cylindrical reactor was designed and developed. This equipment was applied to treat EDTA and EDTA-Cu refractory organic wastewater.(2) Optimum technological conditions of EDTA wastewater treatment were pH 2-4, Fe/C ratio≥0.01, reaction time more than 30min, the presence of oxygen under ambient temperature. Under these optimal conditions, EDTA removal rate reached 83.8%。(3) The mechanism of the Fe-C micro-electrolysis could explained as that the organic matter in EDTA-Cu wastewater will be gradually degraded to small molecular by redox reactions, hydroxyl radical process and galvanic interactions. Consequently, Cu ions was released from EDTA-Cu wastewater. The optimum conditions of EDTA wastewater treatment were pH 2-4, reaction temperature 25℃, Fe/C ratio 0.02, reaction time 60min and the presence of oxygen. Under the above conditions, the concentrations of TOC and Cu ion in wastewater declined from the initial concentrations of 200 mg/L and 60 mg/L to 40.66mg/L and 1.718mg/L, respectively.(4) Electrodeposition surface modification of activate carbon was conducted under 2.5A of electrical current,80V of voltage, Na2SO4 used as electric conductor and FeSO4 used as electrolyte solutions. The electric plating procedure was performed in a reactor. Under the modified condition, electroplating 30 minutes obtained Fe-C particles, which gave the greatest removal efficiency of EDTA-Cu. The concentrations of TOC and Cu ion in wastewater declined from the initial concentrations of 200 mg/L and 60 mg/L to 35.65mg/L and 0.8618mg/L in effuent, respectively.(5) According to the principle of micro-batteries and Fenton reaction, a thermodynamics function of hydroxyl free radical-OH product was deduced by the equationlg[·OH]吸=36.69-lg[Fe3+]+lgPO2-3pH The amount of hydroxyl free radical on the surface of activated carbon depended on the concentration of iron ion, dissolved oxygen and pH value in the system, explanting of various factors on EDTA removal efficiency.