| A large number of nickel-containing waste water will be produced during the process of nickel plating rinse. Nickel ions are very toxic to human and expensive, so an efficient technique for recovery of nickel ions and water from the rinse wastewater will achieve good benefit and has great significance to environmental protection.This paper introduces nanofiltration for nickel plating rinse water treatment in small-scale test, industrial practice and preliminary purification of nickel sulfate, respectively. The study evaluate the effect of temperature, feed flow rate, TMP on flux, as well as the retention rate for Ni2+,organtic additives and boric acid. Further the separation characters were compared of three types of membrane. Experimental data indicate that flux was increased with increasing temperature, feed flow rate and TMP. Then temperature had no significant influence on the retention rate of Ni2+, and higher feed flow and TMP help increase the retention rate of Ni2+. Moreover S membrane was the best performance on separation of nickel-containing waste water. WFR is over 85% after recycle operation for 30 min with 2% citric acid, and the best cleaning condition is: cleaning temperature 35℃, TMP 0.1Mpa, feed flow 2400L/h.The industrial practice of nickel plating rinse water treatment by nanofiltration and recovery was carried out in electroplating factory. The results showed that the rinse water in sealed nickel electroplating was concentrated to 20000 mg/L, and the average flux was greater than 40 L/ (m2·h) At an operating pressure of 2.2 Mpa and feed flow rate of 1800 L/h; In addition, Ni2+ retention rate was greater than 99%, organic additives retention rate was greater than 90%, boric acid retention rate was about 35%, and micropore agent was completely retained. A 60 day continuous plant running result shows that concentrate and permeate were completely recycled back to electroplating bath and washing tank respectively, as required in electroplating. Membrane fouling was overcome by using 5 min water cycle operation after each batch, followed by a 30 min recirculation with 2% citric acid every five days. This technology meets the requirement for industrial operation.To enlarge application range of concentrated, chemical solution were used that includes precipitation, acidolysis and water washing to purify NiSO4. The results show that NaOH was the best precipitator of chemical precipitation method and nickel irons can be completely deposited through controlling pH value at 10 upwards. Precipitation conditions: speed 120r/min, temperature 60℃and reaction time 1 h. After 3 times washing at a liquid-solid ratio of 2∶1, Ni(OH) 2 filter cake reacted with concentrated sulfuric acid to produce NiSO4,whose nickel content are 21.2%>20.5% and meet the National Standard. Ni2+ recovery rate is more than 96%. |
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