Treatment Of HEDP Copper-electroplating Wastewater With Combined Process Of Ferric Precipitation And Fenton Oxidation

HEDP copper-electroplating is a non-cyanide copper plating process which with great development potentialities. While, as the concentration of TP, COD and Cu²⁺ in the wastewater from HEDP copper-electroplating is very high, and the chemical property of HEDP and HEDP-Cu chelating complex is very stable,it is very difficult to purify this kind of water.The research was about the HEDP copper-electroplating wastewater treatment. New methods that could remove both HEDP and Cu were developed,and the main factor and mechanism using combined process of iron ion precipitation and Fenton oxidation were researched. What's more,this technic was put into engineering practice. The conclusions of this paper were as follows:(1)The wastewater of HEDP copper-electroplating almost couldn't be treated by Alkali deposition method using NaOH. The removal rate of Cu²⁺ and TP was 14.0% and 13.2% respectively using Ca(OH)₂. The removal rate of TP , COD and Cu²⁺ was 81%, 92%, and 93% respectively by the method of Fenton oxidation when H₂O₂ dosage was 40 mg·L^-1,while the dosage of reagent by this method was too high. The usage of iron chips sends the drainage to reach the standard of pollutants for electroplating. But when run continuously, there arise a number of problem by this method such as lumps of iron chips, the surface passivation of iron chips , and so on, which led to a decline of the removal rate. The removal rate of TP,COD both reached above 92% by the method of ferric precipitation when pH value was 2.5 and this method could be used in the pretreatment of the wastewater.(2)The optimum conditions of ferric precipitation process were as follows: initial pH value 2.5, M³⁺ dosage1100 mg·L^-1 and reacting time 10 min. Under the optimal conditions, The removal rate of TP, COD and Cu²⁺ was up to 95%, 94% and 31% respectively. The mechanism of the treatment might be that Cu²⁺ of the chelating complex were displaced by Fe³⁺ and formed precipitation. The reacting proportion of Fe³⁺and HEDP increased as the increasing of Fe³⁺ dosage.(3)The wastewater could be also treated efficiently by ferric precipitation process through oxiding Fe²⁺ to Fe³⁺ at first. What's more, it could reduce the reagent cost.(4)HEDP copper-electroplating wastewater could be further treated efficiently by the method of Fenton oxidation. The optimum conditions of Fenton oxidation process were as follows: initial pH value 2.5, H₂O₂ dosage 0.5 ml·L^-1 and [Fe²⁺]/[H₂O₂] 1.0. The removal rate of COD, TP and Cu²⁺ could be up to 98.3%, 99.97% and 99.87% and the drainage reached the standard of pollutants for electroplating.(5)By the running results of practical engineering of HEDP copper-electroplating waste water treatment with combined process of ferric precipitation and Fenton oxidation,it is indicated that the process was efficient, and the facility was simple, and convenient to handle and the cost was low.