Removal of phosphate from brewery wastewater by cerium(III) chloride originating from spent polishing agent: Recovery and optimization studies

Abstract

This paper presents the possibility of using hydrated cerium(III) chloride (CeCl3∙7H2O) recovered from a spent polishing agent containing cerium(IV) dioxide (CeO2) to remove phosphate and other impurities from brewery wastewater (phosphate 43.0 mg/L, total P 19.8 mg/L, pH 7.5, COD(Cr) 827 mg O2/L, TSS 630 mg/L, TOC 130 mg/L, total N 46 mg/L, turbidity 390 NTU, colour 170 mg Pt/L. CCD (Central Composite Design) and RSM (Response Surface Methodology) were applied to optimise the brewery wastewater treatment process. The removal efficiency (mainly of PO43−) was the highest under optimal conditions (pH 7.0–8.5, Ce3+:PO43− molar ratio of 1.5–2.0). Applying recovered CeCl3 under optimal conditions yielded a treated effluent in which the concentration of PO43− decreased by 99.86 %, total P by 99.56 %, COD(Cr) by 81.86 %, TSS by 96.67 %, TOC by 60.38 %, total N by 19.24 %, turbidity by 98.18 %, and colour by 70.59 %. The Ce3+ ion concentration in the treated effluent was 0.058 mg/L. These findings suggest that CeCl3‧7H2O recovered from the spent polishing agent may constitute an optional reagent for phosphate removal from brewery wastewater. The sludge from wastewater treatment can be recycled for Ce and P recovery. The recovered cerium can be reused for wastewater treatment, creating a cyclic cerium cycle in the process, and the recovered phosphorus can be used, for example, for fertilization purposes. The optimised cerium recovery and application is in accordance with the ideas of circular economy.