Phosphate removal during Fe(II) oxidation in the presence of Cu(II): Characteristics and application for electro-plating wastewater treatment

• Oxidation of Fe(II) enhanced by Cu(II) resulted in efficient phosphate removal.
• Cu(II) weakened the impact of the DO, pH and Fe(II) on the phosphate removal.
• The Fe(II)/Cu(II) process has application in real electro-plating wastewater.
• The Fe(II)/Cu(II) process has good phosphate removal and low cost, etc.

This study investigated the potential contribution of co-present Cu(II) on the phosphate removal by the addition of Fe(II), and compare Fe(II) with conventional lime dosing in phosphate removal from real-plating wastewater originally containing Cu(II). Though the phosphate removal during Fe(II) oxidation by DO was notable, the co-present Cu(II) remarkably promoted the phosphate removal by adding Fe(II). The process of phosphate removal during Fe(II) oxidation was affected by DO, [Fe(II)]0 and pH, respectively. The catalytic effect of Cu(II) as little as 0.5 mg/L significantly weakened the suppressed effect of the above mentioned factors on phosphate precipitation. Such enhanced phosphate removal was considered due to the facilitated generation of Fe(III) through catalytic oxidation of Fe(II) in the presence of Cu(II). For the real electro-plating wastewater, in contrast with lime, the process of phosphate removal by dosing Fe(II) combined with the original Cu(II) showed efficient performance, produced less sludge and demanded lower economic cost. These results announced that in the presence of co-existing DO and Cu(II) the Fe(II) may have application in the electro-plating wastewater treatment and important implication for its utilization.