Pretreatment of actual high-strength phenolic wastewater by manganese oxide method

This paper deals with treating high phenol-concentrated wastewater from coal gasification by manganese oxide method. Mixed-phase manganese oxides of manganite and hausmannite were synthesized with industrial MnSO4 and NaOH by air oxidation. The effects of sulfuric acid dosage, reaction time, temperature, manganese oxide grain size and concentration on removal efficiency of total phenols were studied with laboratory bench-scale experiments. The results indicated that the removal process was more effective under the experimental conditions, i.e. acidified media at pH < 4 and an excessive amount of fine particles with a long reaction time. Solution pH and manganese oxide concentration were two of the most important factors which should be well regulated to guarantee higher removal rate. The mixture of manganite and hausmannite showed improved activity for removal of total phenols, TOC and CODCr as compared with MnO2 (AR) but similar to cryptomelane and K-birnessite. Most of organic contaminants especially phenol which occupied absolute predominance in initial wastewater were removed to enhance the biodegradability for further biological treatment. This investigation will provide fundamental method for developing a pretreatment method of industrial phenolic wastewater with flexibility, simplicity and high activity.