Fe/HO-Strengite method with the enhanced settlement for phosphorus removal and recovery from pharmaceutical effluents.

Phosphorus excessively discharged into the water body is a primary cause of eutrophication, but phosphorus resource is limited and non-renewable. If phosphorus could be recovered from wastewaters, it can not only prevent phosphorus pollution but also achieve the recycling of phosphorus resources. This work proposed a novel strategy, Fe/HO-strengite method with the enhanced settlement, for phosphorus removal and recovery from pharmaceutical wastewater containing organic phosphorus (OP). In this scheme, OP could be converted into inorganic phosphorus (IP) in the Fe/HO oxidation system, and then IP was recovered in the strengite system. This approach possessed the advantages of simple operation, high efficiency and valuable recovery products, besides, reducing the consumption of reagents, and hardly resulting in secondary pollution. Sixty cycles of phosphorus removal and recovery experiments were conducted, in which pH value was 4 and the initial molar ratio of Fe/P was 1.5. This process achieved a satisfactory and steady phosphorus removal performance, with soluble phosphate and total phosphorus removal efficiencies of 95.3% ± 1.7% and 91.4% ± 2.5%, respectively, and phosphorus was recovered. Possible mechanisms involved: the formation of amorphous strengite (FePO·2HO) analogue, the adsorption of hydrous ferric oxide (HFO) to phosphorus, and the flocculation of ferric salts. Besides, the presence of quartz as carriers could enhance the settling efficiency of products. Also, via various characterizations, products included amorphous strengite analogue and goethite mixed with phosphorus. This work provided an effective method to reduce OP pollution and recover phosphorus, and supplied thoughts for the treatment of refractory pollutants and the recycling of limited resources.