PHOSPHATE REMOVAL BY FERROUS IRON IN THE PRESENCE OF DISSOLVED OXYGEN: CHARACTERISTICS AND KINETICS INVESTIGATIONS.

This study examined the kinetics of phosphate re- moval during Fe(II) oxidation, and the quantitative relationship between phosphate removal and Fe(II) oxidation in synthetic wastewater. The phosphate removal rate increased with the increase of DO and Fe(II)0 but firstly increased and then decreased with pH. The reaction kinetics of phosphate removal as a function of DO, Fe(II)0 and pH all followed pseudo-first-order kinetics. For the tested DO conditions, quantitative relationship between k_p and k_Fe was described by the equation: k_p 0.6024 k_Fe+0.0004. For the tested Fe(II)0 conditions, the evolution of k_p versus kFe was expressed by two equations: k_p = 1.9573 k_Fe - 0.0233 (Fe(II)0 from 10 to 30 mg/L) and k_p =13.252 k_Fe - 0.2215 (Fe(II)o from 30 to 45 mg/L). For the tested pH conditions, relationship between k_p and k_Fe followed two equations: k= 0.5911 k_Fe 0.0001 (pH from 6.0 to 8.0) and k_p = 0.2274 k_Fe + 0.4401 (pH from 8.0 to 9.0). The precipitates formed at higher DO tended to be more compact, and featured by relatively bigger size, thus it resulted in better solid-liquid separation. [ABSTRACT FROM AUTHOR]