Mechanistic insights into nature of complexation between aluminum and phosphates in polyaluminum chloride treated sludge for sustainable phosphorus recovery

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Efficiency of phosphorus recovery from polyaluminum chloride sludge is determined by chemical interactions between Al and P. Chemical structure of Al–P complex and their binding mechanisms in the PAC sludge were investigated with spectroscopy and chemical fractionation. More than 98% of the P was bound with Al, out of which 70% was strongly bound. The ATR-FTIR analysis indicates that the majority of the P formed inner sphere complex with Al through ligand exchange. The availability of highly protonated surface for P sorption at low pH also supports the formation of Al–P outer sphere complex.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PAC sludge contained AlPO<SUB>4</SUB> or related Al–phosphate complex. </LI> <LI> Results showed that 2 types of Al–P bonds are formed in PAC sludge. </LI> <LI> 70% of total Al–P, strongly bound, while 29% was moderate to strongly bound. </LI> <LI> Al–P complex are formed majorly by ISC through ligand exchange mechanism. </LI> <LI> Bidentate binuclear complex followed by monodentate mononuclear and bidentate mononuclear formed at acidic and alkaline pH respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>