| Electroplating industry not only largely applied on traditional industries such as metallurgy,machinery,electrification and traffic,but also widely used on those emerging industries such as electronic technology and communication technology.Large numbers of electroplating waste water was discharged every year,which counts 10 percents of all the waste water.While,only half of them was been disposed before discharging.The pollutants in electroplating waste water are so diverse,which including hazardous heavy metals such as copper ions,chromium ions,lead ions and cadmium ions.Heavy metal ions can complexed with EDTA(Ethylenediamine tetraacetic acid),CN-(cyanide ion)and NH4+(ammonium ions),thus making it harder to discharging the electroplating waste water.The traditional measures for electroplating waste water with copper is aim at Cu2+rather than complexing copper,thus the concentration of copper is so high.The traditional measures can't meet the satisfaction of environmental protection,so effective measures must been taken to treat the electroplating waste water.Electrolysis-coagulation is to removal the copper ions from electroplating waste water in this study.The actual electroplating waste water come from industry whose concentration is 38.5510mg/L is to be researched.Separately study electrode,voltage,electrode spacing,electrolytic time,initial pH,sodium sulfide dosage,PAC(Polyaluminium chloride)dosage and PAM(polyacrylamide)dosage's influence to the final concentration of copper ion by electrolysis-coagulation.In the case of the cathode and the anode are titanium plate,the electrolysis's effect is best,that is not only conducive to recycle copper,but also the titanium plate can be repeatedly used.Considering the electrolytic time and the quantity of waste water,the voltage is 12V and electrode spacing is 30mm.Then use the rest five factors:electrolytic time,initial pH,sodium sulfide dosage,PAC dosage and PAM dosage to design five factors and three levels' orthogonal experimental.The results showed that,when the initial concentration of copper ion was 38.5510mg/L,the cathode and the anode ware titanium plate,voltage was 12V,electrode spacing was 30mm,pH is 2.2,sodium sulfide dosage is 0.0450g,PAC dosage was 0.0700g,PAM dosage was 0.0600g,electrolytic time was 80min:the first step time was 15min,the second step time was 20min,the third step time was 30min,the final concentration of copper ion can be as low as 0.10mg/L.The removal rate is 99.9%.The final concentration of copper ion is 80%lower than 0.5mg/L.The primary standard of the Emission standard of pollutants for electroplating(GB21900-2008),the Local standards in Guangdong province-discharge limits of water pollutant(DB4426-2001)and Emission standard of pollutants for copper,cobalt,nickel(GB25467-2010)are all 0.5mg/L.The small experiment was implied in polyethylene cuboid every time.The specification is L×W×H= 100mm×80mm×100mm and the volume was 100mL.To guarantee the scientificity and the utility,the magnified experiment is essential.The specification of the magnified experiment was L×W×H= 210mm×110mm×340mm and the volume was 200mL.The results showed that,when the initial concentration of copper ion was 38.55 10mg/L,the cathode and the anode ware titanium plate,voltage was 12V,electrode spacing was 30mm,initial pH was 2.2,sodium sulfide dosage was 0.2025g,PAC dosage was 0.3151g,PAM dosage was 0.2452g,electrolytic time was 80min:the first step time was 15min,the second step time was 20min,the third step time was 30 minutes,the final concentration of copper ion also can be as low as 0.10mg/L.The mechanism of heavy metals removal in electroplating waste water by electrolysis-coagulation was preliminary discussed based on the above experiment data. |
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