Effect of pH on Advanced Treatment of Mid-stage Pulping Effluent with Potassium Ferrate

The effects of pH on the advanced treatment of mid-stage pulping effluent with potassium ferrate were studied. Firstly, the effect of pH on the stability of the potassium ferrate solution was studied, which indicated that potassium ferrate was more stable in alkaline conditions than in acidic and neutral conditions, and the most stability was achieved at pH of 9-10. Then the effect of pH on the rnid-stage pulping effluent treatment with potassium ferrate showed that the oxidation increased firstly and then decreased with the increase of the pH. The best treatment efficiency was at pH=4, under which COD removal efficiency reached 40%. The flocculation experiment was conducted using Fe3+ produced by the oxidation reaction as flocculant and PAC as extra flocculant and PAM as coagulant aid. Effect of pH on the flocculation process was studied, which showed that the flocculation effect first increased and then decreased with pH increasing. When pH was 9, COD removal efficiency reached 60%. The final effluent of COD concentration was less than 60mg/L, which met the requirements from the national first-order discharge standard.