Phosphorus removal from aqueous solutions containing low concentration of phosphate using pyrite calcinate sorbent

Natural pyrite was modified by calcination under nitrogen (N₂) atmosphere to produce a novel sorbent for removing phosphorus (P) with low concentration from aqueous solutions. The crystallinity, porous texture, magnetic susceptibility and performance in P removal of pyrite calcinates depended on calcination temperatures. The sorbent obtained at calcination temperature of 500–600 C possessed the most efficient P removal. Solution ph in the range of 3.0–9.0 and anions of chloridion (Cl^-), nitrate (NO₃)^- and sulfate (SO₄^2-) had ignorable effect on P removal. The batch adsorption experiment shows that the maximum sorption capacities for P of this novel sorbent (qm) were up to 1.61–5.36 mg P/g at adsorption temperatures of 15–35 C. Dynamic sorption and regeneration experiments were conducted in an adsorption column filled with pyrite calcined at 600 C. The study found that oxygen was an important control factor responsible for P adsorption because the oxidization of Fe²⁺ to Fe³⁺ on the surface of the sorbent followed by P being bound to a ferric hydroxide surface film was the crucial processes. The mechanism was confirmed with surface characterization techniques including field emission scanning electron microscope and X-ray photoelectron spectroscopy. This research potentially provides a cheap, abundant sorbent for P removal from the secondary effluent of municipal wastewater treatment plant.