Mechanochemical synthesis of Ca-Al-La layered double hydroxide for efficient soluble phosphorus immobilization in...

Direct utilization of phosphogypsum generated through phosphorus fertilizer production is challenging due its complex composition. The water-soluble phosphorus content in phosphogysum is one of the main parameters limiting its application. In this study, Ca/Al/La layered double hydroxide(LDH) materials were synthesized through a mechanochemical method to immobilize the phosphorus in phosphogypsum. Parameters including Ca/Al/La molar ratio, ball-milling time, and milling intensity were selected to study the impacts on phosphorus adsorption performance using Ca/Al/La LDH materials. Phosphorus adsorption mechanism was revealed through a series of characterization techniques. The maximum phosphorus adsorption capacity of Ca/Al/La LDH was 345.6 mg/g. After reacting with phosphogypsum, Ca/Al/La LDH exhibited a higher phosphorus fixation efficiency (89.95 %) compared with Ca/Al layered double hydroxide (76.1 %). Moreover, the mechanical strength for the plaster products prepared by calcination of the Ca/Al/La LDH treated phosphogypsum showed improved mechanical strength (flexural strength: 6.6 MPa, compressive strength: 9.30 MPa) than that of Ca/Al LDH (flexural strength: 3.9 MPa, compressive strength: 6.50 MPa). The mechanochemically synthesized Ca/Al/La LDH exhibited high efficiency in immobilizing phosphorus within phosphogypsum. The conversion of this treated phosphogypsum into building plaster powder resulted in a substantial enhancement of its physicochemical properties, thereby presenting a viable technological pathway for the utilization of phosphogypsum.