The Study On Electroplatingwastewater Containing Nickel Ions By Pre-precipitation And Fenton-Like-Precipitation Or Fenton-Precipitation Process

The electroplating industry is one of the three major polluting industries in the world.The composition of pollutants is complex in electroplating wastewater,and the electroplating etching mother liquor is particularly noticeable.This kind of wastewater is characterized by high concentration of heavy metals,micro-insoluble heavy metal ions in water,and part of heavy metal ions and EDTA?ethylenediaminetetraacetic acid?,CN^-?cyanide ion?,NH₄⁺?ammonium ion?complex to form a stable complex in wastewater,increasing the difficulty of the ion plating wastewater treatment.This paper briefly introduces the treatment status of electroplating nickel containing heavy metal wastewater,and discusses the treatment methods of various nickel wastewater.Taking the etching mother liquid of a electroplating plant as the research object,the experimental study on the treatment of Ni?II?in electroplating wastewater by the pre-precipitation combined with Fenton broken or Fenton-like and coagulation sedimentation technology has been studied.The following research achievements has been obtained.The nickel concentration was 2220 to 2260 mg/L the actual electroplating wastewater,the first step of pre-precipitation reaction of pH is 10,set free nickel ions settling time of 30min can be completely removed in water,the effluent concentration of nickel ions can reach15 mg/L,the introduction of sodium sulfide has little efficiency on the concentration of nickel ion in water.The best combination for hydrogen peroxide dosage is 3 mL/L,reaction pH 6,reaction time is 60 min,the Fe²⁺/H₂O₂ ratio of 0.15 for the fenton process,the best combination of for hydrogen peroxide dosage of 2.5 mL/L,reaction pH 6.5,reaction time is60 min,the Fe³⁺/H₂O₂ ratio of 0.1 for the fenton-like process,and then combined with chemical precipitation pH is set to 10,adding 80 mg/L coagulant polysilicate aluminum ferrite,20 mg/L anion PAM,The final concentration of nickel ion is 60%lower than 0.5mg/L.The primary standard of the Emission standard of pollutants for electroplating?GB21900-2008?,the local standards in Guangdong province-discharge limits of water pollutant?DB4426-2001?and Emission standard of pollutants for copper,cobalt,nickel?GB25467-2010?are all 0.5mg/L.The cost of Fenton reaction and the Fenton-like reaction experiment is 17.759 yuan/m³ and 17.648 yuan/m³ respectively for the two reaction combinations,and the cost is about the same.Therefore,these two treatment processes can be applied to this kind of electroplating wastewater.