Acid–base properties and surface complexation modeling of phosphate anion adsorption by wasted low grade iron ore with high phosphorus

• Interaction mechanisms between wasted low grade iron ore and aqueous solution were elucidated.
• Protonation constants of wasted low grade iron ore were obtained.
• Surface adsorption complexation model of P onto wasted low grade iron ore was established.

The adsorption phenomena and specific reaction processes of phosphate onto wasted low grade iron ore with high phosphorus (WLGIOWHP) were studied in this work. Zeta potential and Fourier transform infrared spectroscopy (FTIR) analyses were used to elucidate the interaction mechanism between WLGIOWHP and aqueous solution. The results implied that the main adsorption mechanism was the replacement of surface hydroxyl groups by phosphate via the formation of inner-sphere complex. The adsorption process was characterized by chemical adsorption onto WLGIOWHP. The non-electrostatic model (NEM) was used to simulate the surface adsorption of phosphate onto WLGIOWHP. The total surface site density and protonation constants for NEM (NT = 1.6 × 10−4 mol/g, Ka1 = 2.2 × 10−4, Ka2 = 6.82 × 10−9) were obtained by non-linear data fitting of acid–base titrations. In addition, the NEM was used to establish the surface adsorption complexation modeling of phosphate onto WLGIOWHP. The model successfully predicted the adsorption of phosphate onto WLGIOWHP from municipal wastewater.

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