A Study Of Acid Picking Wastewater Recovery By Electrodialysis

Picking waste water is common industrial waste water. Each year the picking workshop in electroplating, mechanical processing, silicon carbide, steel manufacturing and other industries will produce a large number of picking wastewater. The annual acid picking wastewater emissions are above 106m3. If they discharge directly, they will pollute the environment and waste the energy. Therefore, resource recovery and utilization of the acid picking wastewater have become a hot issue of industrial wastewater treatments today. This topic is about the single membrane electrodialysis treatment of sulfuric acid picking wastewater which is based on the emerging technology of membrane processing. This topic aims to explore the influence factors of the single membrane electrodialysis, look for optimal electrodialysis process parameters and build the combined device of sulfuric acid picking wastewater. The picking waste water can be recycled which can reduce the pollution degree of the environment, obtain some economic benefits and provide reliable theoretical basis and practical guidance for its industrial application.The experiment is divided into two parts: the static electrodialysis experiment and the dynamic electrodialysis experiment. Through the static electrodialysis experiment, we find the optimal design parameters and operating parameters of the single membrane electrodialysis. Then according to the optimal parameters of the static electrodialysis experiment, we build a dynamic single membrane electrodialysis combined equipment and optimize it.The static electrodialysis experiment explores five parameters which influence the iron ion removal rate and anode effluent pH. They are the voltage, the effective depth, the concentration of iron ion, the anion exchange membrane and the volume ratio of negative and positive poles. The experimental results show that, the static electrodialysis processing technology can recover the acid picking wastewater effectively. The voltage, the concentration of iron ion, the anion exchange membrane and the volume ratio of negative and positive pole impact electrodialysis treatment effect significantly, but the effective depth has only little effect. The changes of the parameters mainly affect the removal rate of iron ion, which has little effect on the pH of the anode effluent water. The removal rate of iron ion increases with the increase of voltage, but after 24 V, the removal rate of iron ion varies with the increase of voltage tinily. With the concentration of iron ion increases, the removal rate reduces. When the concentration of iron ion is 100mg/L, the removal rate of iron ion is the biggest. The rank-ordering of the four kinds of anion exchange membrane by removing the iron ion's rate is: HC-06>MC-01>AAM>HC-08. Under the condition of constant voltage and time, the smaller cathode chamber, the higher the removal rate of iron ion. In the static electrodialysis experiment, when the operating voltage is 24 V, the cathode chamber volume is 13.34 L, the anode chamber volume is 8.004 L and the effective depth is 21 cm, choosing HC-06 anion exchange membrane, the treatment effect is the best. At 80 min, the removal rate of iron ion in the cathode chamber has reached 99.16% and the effluent concentration of iron ion is 0.8mg/L.In the dynamic electrodialysis experiment, basing on the optimum parameters of the static electrodialysis experiment, we design combined process of “electrodialysis+ filtration” to dispose the sulfuric acid picking wastewater. The experimental results show that combined process of “electrodialysis+ filtration” can effectively recover the acid picking wastewater. When the voltage is 40 V and the water flow rate is 6.3 L/h, the treatment effect is the best. At this moment, we dispose the acid picking wastewater including 100m/L iron ion concentration. The removal efficiencies of iron ion in the cathode chamber, filter and anode chamber were 83.42%, 89.95% and 88.22%. The tons of water consumption is 17.08kwh/t and the unit energy consumption of removing the iron ion is 0.1916kwh/g. Then under the optimal voltage and the water flow conditions, changing the concentration of iron ion, we find when the concentration of iron ion is 100mg/L, electrodialysis treatment effect is the best and the tons of water consumption is minimum. But the unit energy consumption of removing the iron ion is too high. When the concentration of iron ion is 300mg/L, the unit energy consumption of removing the iron ion is optimal, but removal rate of iron ion is low, less than 70%.