Research On Technology Of Oxidating Electroplating Wastewater Containing Cyanide By Microelectrolysis Combined With Fenton Reagent

It is necessary and urgent to degrade the electroplating wastewater which contain-ing cyanide and heavy metal ions are harmful to water. Micro-electrolysis combined with Fenton reagent is an efficient method for degradation of pollutants, and it is used in treatment of printing and dyeing industry. However, the research on electroplating wastewater is rare. And it is of great significance to study the mechanism of mi-cro-electrolysis combined with Fenton reagent.According to orthogonal test and single factor experiments, the study using elec-trochemical workstation and Fourier transform infrared spectroscopy (FTIR) on operat-ing conditions; mechanism and models were as following:(1) It was the first time to study on degrading electroplating wastewater containing cyanide by micro-electrolysis with Fenton reagent at the same time. And did compare with micro-electrolysis then Fenton reagent treatment (writing as "Fenton Reagent strengthens micro-electrolysis" on backward). Fenton Reagent strengthens mi-cro-electrolysis and micro-electrolysis-Fenton reagent both could degrade cyanide wastewater to meet discharge standards. The former removal rate could be beyond 99%, when pH value, the volume ratio of iron to carbon, aeration and reaction time of mi-cro-electrolysis were 3.5, 2, 60min and 60min, pH value, H₂O₂ dosage, reaction time of Fenton reagent were 5, 2.0mL/L, 20min, respectively. The removal of mi-cro-electrolysis-Fenton reagent could be to 99% with pH 4, volume ratio of iron to car-bon 2, H₂O₂ dosage 0.7mL/L and reaction 120min.(2) For the first time, reaction process was analyzed through research on iron sur-faces by the simulation of micro-electrolysis-Fenton reagent. Tafel curves in different conditions showed that low pH value had low corrosion potential, making the initial rate of degradation increase. Compared FTIR of iron surface products and precipitation, it showed that iron surface was not reacted with cyanide ions and the surface grewγ-FeOOH. The CN^- precipitated from the liquid phase with metal ions, however, it was disappeared by adding H₂O₂ which generated·OH. Compared X-ray diffraction of irons in different conditons, it showed that surface of iron grew FeOOH, Fe(OH)₂, Fe(OH)₃ and Fe₄[Fe(CN)₆]₃, besides, dissolved iron Fe²⁺ removed CN^- out of liquid phase by complex-precipitation. Micro-electrolysis could break copper cyanide complexes, re-moving CN^- by producing Fe₄[Fe(CN)₆]₃ and Cu₂[Fe(CN)₆] with Fe²⁺, Cu²⁺ from wastewater. FeOOH and hydroxides were important reasons to cause micro-electrolysis compaction.(3) By analyzing the micro-electrolysis and Fenton reagent cyanide ions in the mechanism of their removal, the degradation rate equation was established. Assuming micro-electrolysis-Fenton reagent abided by first order kinetics law, the equation was proved to be right by checking in influent pH, the amount of H₂O₂ dosage and volume of iron to carbon ratio experiments.(4) For the first time, the mathematical model was established by nonlinear fitting for Fenton reagent strengthen micro-electrolysis and micro-electrolysis-Fenton reagent, using origin pro and 1stOpt software to solve coefficients. The correlation coefficient R² were all beyond 0.91 and validation were in the confidence interval which confidence level was 95.4%. It proved that the model can correctly reflect the effect of technological processing.