Abstract
The saturated magnetization (σ) of the ferrite sludge formed by two-step treatment of wastewater containing heavy metal (cadmium sulfate) and potassium dihydrogen phosphate was measured over a wide concentration range of potassium dihydrogen phosphate. Simultaneously, the concentration of cadmium and iron ions in treated water was measured. From the results of measurement, the effect of the two-step treatment on the above parameters was quantitatively discussed by comparing the three different process treatment : conventional, excess-iron and two-step treatments.
The σ value of ferrite sludge formed by the two-step treatment was larger than that by conventional treatment in phosphate ion concentration above 330 mg·l-1. The ferrite sludge formed by conventional treatment was reformed to the sludge from which cadmium ion was not easily eluted by the ferrite coating effect of two-step treatment. The pre-treatment by sodium hydroxide was effective in removing phosphate ion and increasing the σ of ferrite sludge. The concentration of cadmium ions in treated water produced by ferrite process was lower than that in treated water produced by neutralization method. The two-step treatment is favorable for steady operation of the ferrite process, industrial utilization of the sludge and good quality of the treated water.
