Study On Recycling Nickel From Plating Wastewater

The disposal technique used in electroplating nickel wastewater and the membrane technique were reviewed in the paper. Through the experiment, a new technique recycling nickel from plating wastewater by chemical precipitation-membrane filtration was proposed. The experiment results showed that: this technique not only has the advantages of the chemical process but also can solve the difficulties in deposit separation. The purity of the recycled nickel is high. After dissolved by sulfuric acid, it can be reused to production process. The concentration of Ni2+ is low and the effluent quality can meet the national discharge requirements. This method actually reaches the goal of simple technique process, small occupation of land, no need of settling tank, steady operation and easy management. Especially, inorganic ceramic membrane filtration has the outstanding advantages in efficient separation, resistance to acid and alkali, large flux, high mechanical strength, easy regeneration, having the foreground of industrialization, it also can spread to apply in the similar technique for solid-liquid separation. The main technique parameters were determined by the experiment: Controlling pH≥9.2, the reaction of sedimentation of Ni(OH)2 can finish completely. In organic membrane filtration the appropriate operation pressure is 0.2MPa, temperature<40℃, cyclic flow rate is 3.6 m/s, concentration ratio<25 multiple. Stop to clean in chemical method when the flux reduces to 30% of the original so that the flux can be recovered to 95% about. Whereas in inorganic ceramic membrane filtration, the membrane pore size is 0.5μm. The suitable operation pressure is 0.2-0.3MPa. Operation temperature is not confined by the equipment itself, usually, the temperature ≤70℃, flow rate is 5.0 m/s ,concentration ratio <50 multiple. Controlling the polluted membrane by online gas-liquid backwashing. Stop to clean in chemical method so that the flux can be recovered to 99% about. This paper has put forward a mathematical model for the membrane filtration process. It was tested to be correct by the experimental data. The main conditions of the membrane filtration process have been discussed according to the model theory and calculated data.