Membrane Technology Optmization And Membrane Fouling Control For Electroplating Wastewater Reuse

Printed circuit board(PCB)electroplating wastewater is a heavy metal content of high wastewater,if not properly handled,will cause secondary pollution.The application of ultrafiltration + reverse osmosis process PCB plating wastewater treatment,to achieve its standard discharge or reuse.On the basis of the small test,the pilot scale system optimization was carried out,and the membrane pollution characteristics and control measures were also studied.First of all,the pretreatment process is optimized.The effect of effluent and running stability under the optimal operating conditions were compared with the pretreatment of alkali pretreatment,coagulation sedimentation and flocculation.Alkali precipitation under optimal operating conditions(pH=10),the average turbidity of the effluent is 19.7 NTU,and the average concentration of copper and nickel ions is 2.61 mg/L and 1.98 mg/L.Coagulation sedimentation under optimal operating conditions(pH=10,PAC=18 mg/L,PAM=2.0 mg/L),the average turbidity of the effluent is 13.0 NTU,the average concentration of copper and nickel ions is 0.97 mg/L and 0.69 mg/L.Loading flocculation under the optimum operating conditions(pHl=10.5,pH2=9.5,PAC=12 mg/L,PAM=1.0 mg/L,reflux sludge 3500 mg/L),the average turbidity of the effluent is 4.0 NTU,and the average concentration of copper and nickel ions is 0.36 mg/L and 0.24 mg/L.The pretreatment process is better than that of coagulation sedimentation and alkali precipitation pretreatment.The pretreatment process is better than that of coagulation sedimentation and alkali pretreatment.Furthermore,the pretreatment effluent was subjected to ultrafiltration + reverse osmosis treatment.For the ultrafiltration system,the main study of two ultrafiltration membrane(flat ceramic membrane and hollow fiber membrane)water quality and operational stability.The results show that the flocculation-ultrafiltration process is better.The total copper and total nickel concentrations were reduced to 0.07 mg/L and 0.06 mg/L,respectively.The removal rates were 81.1%and 75.7%,respectively.The transmembrane pressure difference(TMP)was stable at 5-6 KPa.After the flocculation-hollow fiber membrane was loaded,total copper and total nickel concentration were reduced to 0.06 mg/L,0.05 mg/L,respectively,the removal rate reached 83.8%and 79.6%,TMP stable at 20-25 KPa.In order to reverse osmosis system,the desalination rate,recovery rate and running stability of reverse osmosis membrane in series and parallel connection were studied.The results showed that the desalination rate of the reverse osmosis membrane was 45.5%,and the TMP was stable at 1200-1500 KPa.On the basis of the above research,the process of PCB electroplating wastewater is connected and optimized.Finally,the membrane fouling analysis and control research were carried out.Firstly,the ultrafiltration membrane was analyzed by scanning electron microscopy and energy dispersive spectroscopy.It was found that the membrane fouling of the flat ceramic membrane was mainly due to the adsorption of organic matter on the membrane surface.The hollow fiber membrane is mainly caused by the accumulation of hydroxide precipitated particles.Membrane pollution control measures are mainly anti-washing,aeration and acid-base alternate cleaning.The optimum cleaning conditions were as follows:anti-cleaning intensity 25 L/h,anti-washing time 60 s,anti-washing cycle 60 min.The optimum chemical cleaning conditions were:first pickling(HCl + EDTA,0.20%w/v),after alkaline washing(NaOH + NaCIO,0.20%w/v).Aeration is conducive to the prevention of the formation of flat ceramic membrane cake layer,gas to water ratio=15 for the best gas to water ratio.The optimum anti-cleaning conditions of the hollow fiber membrane are:anti-cleaning intensity 30 L/h,anti-cleaning time 90 s,anti-cleaning period 30 min;The optimum chemical cleaning conditions were:first pickling(HCl + EDTA,0.20%w/v),after alkaline washing(NaOH +NaCIO,0.20%w/v).