Effectiveness and Mechanism of the In Situ Formed Iron Hydroxide (FeO_xH_y) towards the Removal of Phosphate by Coagulation and Adsorption

Abstract:

This study prepares the in situ formed iron hydroxide (In situ FeO_xH_y) by the interactions between Fe³⁺ and OH^- at different molar ratios of 1:0,1:1,1:2,and 1:3, and investigates the performance and mechanism involved in the removal of phosphate. The removal efficiency increases with elevated doses of FeO_xH_y and the maximum removal is observed to be in neutral pH ranges. The elevated ratios of OH^- to Fe³⁺ inhibit the removal of phosphate whereas at low alkalinity,the introduction of OH^- shows beneficial effects. The abovementioned four kinds of FeO_xH_y can rapidly adsorb most phosphate within 15 s, and the adsorption process can be well described by the Pseudo-second-order kinetic model. Freundlich model can well describe the adsorption of phosphorus onto these four FeO_xH_y. The adsorption of phosphate significantly decreases the zeta potential of these in situ FeO_xH_y. The MINITEQ software can indicate the species distribution of phosphate and iron salts, and the theoretical calculation indicates that the introduced OH^- can promote the hydrolysis of Fe³⁺ especially in low alkalinity system,which can easily adsorb H₂PO₄^- and HPO₄^2- and form the multinuclear hydroxy iron phosphate complexes thereafter.

• Periodical: Advanced Materials Research (Volumes 807-809)
• Pages: 1251-1257
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.807-809.1251
• Online since: September 2013
• Authors: Li Hua Sun, Xiao Lu Qi, Ya Jun Zhang
• Keywords: Adsorption, Coagulation, In Situ FeO_xH_y, Iron Phosphate Complexes, Phosphate

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