Pretreatment of 3-hydroxyacetophenone in pharmaceutical wastewater using combined salting-out crystallization+ Fenton system and subsequent impact analysis of effluent water

Abstract

ABSTRACTSelecting a suitable pretreatment process for pharmaceutical wastewater that is difficult to treat biochemically so that it can enter the subsequent biochemical treatment. In this study, pharmaceutical wastewater consisting of 45 g/L sodium bisulfate, 9 g/L 3-hydroxyacetophenone (3-HAP), and 36.75 g/L sulfuric acids,which is a kind of typical pharmaceutical wastewater, was used for the pretreatment case study, and the process was screened by technology. A salting-out crystallization+Fenton system(SC-F) was developed for the treatment of this wastewater. The salting-out agent is formed by the pH adjustment process without additional additions and the salting-out crystallization effect is significant for the precipitation of 3-HAP from the wastewater. Subsequently, the optimal operating conditions for SC-F were derived from experiments as H2O2 of 0.4692 mol/L, n(H2O2):n(Fe2+)=30:1, pH=3. Under optimal conditions, the reaction time of 2 h achieved a COD removal rate of 90% and a BOD/COD value of 0.56, confirming the effectiveness of the technology in treating this wastewater. Additionally, it was discovered that the Fenton treatment was not significantly impacted by the inorganic components of the effluent. Analysis of effluent properties and possible effects on subsequent treatment by LC-MS and toxicity analysis. The results show that the biodegradability are enhanced by the pretreatment technology. However, the effluent still suffers from high acidity and high salt content, and this study proposes a solution to this problem. Furthermore, research on the treatment of 3-HAP wastewater has not been reported and this study provides a new case study in the field of wastewater treatment.