In-situ synthesis/purification integration strategy for simultaneous capture of ammonium and phosphorus from digested piggery wastewater using magnesium-doped tricalcium aluminate

Abstract

Simultaneous capture of ammonium (NH4+-N) and phosphate (PO43−-P) in digested piggery wastewater is of great urgency yet remains a challenge. Recently, the in-situ synthesis/purification integration (ISSPI) strategy, with the essence of converting contaminations to high value-added products, has aroused great enthusiasm in the environmental remediation realm. In the present work, we employed ISSPI method for simultaneous elimination and recovery of NH4+ and PO43- from digested piggery wastewater based on the construction of a novel material system, i.e., Mg-doped tricalcium aluminate (Mg-C3A), which coupled the features of cement-based material tricalcium aluminate (Ca3Al2O6, C3A) and Mg dopants. The released metal cations (Ca2+, Mg2+, and Al(OH)4−) of Mg-C3A were expected to act as precipitation agents to capture NH4+ and PO43− via the formation of Ca(NH4)2(HPO4)2, MgHPO4·3H2O or AlPO4; OH− established an alkaline environment for the enhancement of NH4+ removal via neutralization; Mg2+ played a major role in the recovery of NH4+ and PO43−, with the formation of valuable struvite as fertilizer. Benefited by these functions, Mg-C3A exhibited superior removal capacity for NH4+ (43.0 mg·g−1) and PO43− (20.2 mg·g−1). More importantly, the ISSPI method using Mg-C3A was prospective to be applied for authentic effluent treatment as demonstrated by response surface methodology (RSM), with the concentration of both ions down to the discharge standard of livestock and poultry breeding, China (80 mg·L−1 for NH4+; 8 mg·L−1 for PO43−). This research provided an alternative and promising approach for the simultaneous removal and recovery of NH4+ and PO43− from digested piggery effluent, shedding light on environmental remediation.