Crystallization And Recovery Of Copper From Wastewater With High Copper Concentration

Heavy metal wastewater is characterized by large capacity of drainage, complicated components and heavy-toxicity. Coagulation precipitation and ion exchange method are common treatment of heavy metal wastewater, but both methods have disadvantages(e.g., large amount of sludge and high investment operating cost). In recent years, hydraulic fluid bed induced crystallization method could reduce cost and recover heavy metal from wastewater efficiently, but it showed low effeciency on high concentration of wastewater. The topic is about the crystallization of hydraulic fluid bed reactor for the high concentration of heavy metal, “air stirred & hydraulic fluid bed crystallization reactor + hydraulic fluid bed reactor crystallization + filtration column + ion exchange column" are proposed. High concentration of wastewater containing copper is used as the treatment object to study the efficiency of the crystallization of hydraulic fluid bed reactor through lab-scale experiments; and the treatment effect of different concentrations of wastewater containing copper by three kinds reactor is compared; meanwhile, the recovery rate of Cu2+ of the combination technology is investigated through experimental of continuous dynamic operation.The lab-scale results show that the basic operating parameters of the completely mixed crystallization reactor are as follows: using Na2CO3 as the precipitator, 80~120 mesh as the carrier particle size, 0.222 as the fill ratio of the carrier, 1.06 as the expansion of the fluidization. The influencing factors of induced crystallization is studied by labscale experimental reactor, the results show that when the influent concentration of Cu2+ is 300 mg/L, the operating parameters are as follows: 5 as the influent p H, the concentration of residual carbonate ion which is 80 mg/L as the inlet dosage, 30 minutes as HRT.In this study, 100 mg/L, 300 mg/L of wastewater containing copper are treated by the crystallization completely mixed reactor. The result confirms that the completely mixed reactor treating high concentration of crystalline copper wastewater stability and effectiveness. After 45 days’ operation, the carrier particle size increases from 0.166 mm to 0.322 mm, the crystals with high purity, the recovery rate of 80% to 90%; the appearance of crystalline product is grass green. It is suggested that the crystal product is cupric subcarbonate by SEM-EDS analysis.The effects of different concentrations of Cu2+ crystal are compared by using three kinds reactor of hydraulic fluid bed, sequencing batch-mechanical stirred reactor and hydraulic fluid bed-air stirred reactor. The results show that the hydraulic fluid bed reactor is more suitable for crystallization with flow conditions at low concentrations. While air stirred & hydraulic fluid bed crystallization reactor has good effect with higher concentrations of wastewater. The continuous dynamic tests show that the combination technologyhas the higher recovery rate when treating high concentration of wastewater containing copper. When the average influent concentration of Cu2+ is 300 mg/L and the influent p H is 1.5, the parameters in the flow water- air stirred crystallization reactor are 30 minutes of HRT, 200 L/h of back flow, 0.4 m3/h of the aeration rate. and the crystallization hydraulic fluid bed reactor residence time is 20 minutes under the return flow 210 L/h of conditions, the average effluent concentration of Cu2+ is 0.3mg/L or less, to meet the national emission requirements, and the recovery rate of Cu2+ can reach about 99%.