Study On Membrane Separation Of Ni²⁺/Cu²⁺ In Electroplating Rinse Water And Its Rejection Rate Prediction By Neural Network Model

The membrane technology has a good application prospect in the field of electroplating waste water recovery.In consideration of the high cost to process the terminal electroplating waste water and recycle heavy metal by the membrane technology.Therefore,this experiment is based on the post-plating rinse water produced by small electroplating plants,adopt the PTFE hollow fiber filtration system in the cleaning line of electroplating process to separate and recycle the nickel and copper ions in the electroplating rinse water and investigate a clean and economical production method to recycle the heavy metals and water.Therefore,the paper aims to perform researches in the operating pressure,pH value and effects on the rejection rate of heavy metal ion sediments by the pure water flux,and predict therejection rate of neural network model for the membrane system.The results are shown as below.First,by filtrating the simulated water samples with the membrane system,we conclude that the membrane flux is positively related to the operating pressure.While the reject rate is positively related to the operating pressure within 0.1MPa-0.7MPa,effects of the operating pressure begin to fade at 0.7MPa above and no significant difference in the reject rates of different metal ion water samples has been observed when the operating pressures are strengthened.Since the membrane surface with high pH value is attached with more OH^-,the negative electricity of the membrane surface largely increase the gra?tation between metal ions.Therefore,the pH value of the water sample is high,the reject rate of the membrane on metal ions will increase.From?ew point of reducing the impact of membrane fouling,decreasing the energy consumption of the membrane system and impro?ng the membrane filtration efficiency,the optimal operating pressure for the membrane system is 0.7MPa.While keeping the initial membrane flux consistent,the average reject rates of Ni ions and Cu ions are 94.02%and97.09%respectively.In the short term,the recovery rate of the membrane flux can be over98%by backwash.Through evaluating the rejection effect and comprehensive benefits of the Ni?OH?₂/Cu?OH?₂ recovery by the membrane system in the small-scale electroplate factory that produce the Nickel plating rinse water and coppering rinse water 1350t,the results showed that the reject rate will be larger than 90%when the membrane system is used to separate Nickel plating rinse water with the concentration at the scope of 56.58mg/L-364.11mg/L.Meanwhile,the reject rate will be larger than 90%when separating the coppering rinse water with the concentration at the scope of 43.06mg/L-366.6mg/L.The results meet the requirements of"Iron Utilization Rate"and"Copper Utilization Rate"with a Class I benchmark value of 90%?95%in Cleaner Production Evaluation Index System of Electroplating Industry.Within a short time of the air and water backwash,the high metal ion recovery can be remained and the economic benefit can be improved.Therefore,in the constant filter operation,the backwash cycle is 80min.The total investment of the membrane system equipment is 5490 yuan,the profit of recycling Ni?OH?₂ is 17,000 yuan per ton,and the profit of recycling Cu?OH?₂ is 19,700 yuan per ton.By comparing ceramic membrane separation wastewater and nanofiltration-reverse osmosis separation wastewater process,the PTFE hollow fiber membrane separation process is more applicable to small electroplating enterprises.due to small investment,less equipment and simple operation.The overall efficiency indicator shows that it is very practical in small electroplating companies.Based on the experimental samples and training data samples by BP neural network model and WNN neural network model,the results show that WNN neural network can precisely predict the reject rates of the rinse water containing Ni ions and Cu ions and solve the hysteresis of the reject rate of the membrane system in the practical application,which pro?des a good prediction tool for the membrane system to separate the heavy metal ions and has certain value for industry use.