Development of a Polyaluminum Ferric Titanium Chloride for Phosphorous Removal in Water

Abstract

Phosphorus removal is a promising means to effectively prevent and control the eutrophication of natural waters. Coagulation can achieve phosphorus removal with high efficiency, and therefore the preparation of coagulants has recently garnered increasing attention. Ferric chloride, aluminum chloride, and titanium tetrachloride were used to prepare polyaluminium ferric titanium chloride (i.e., PCAFT) by changing the molar ratio of trivalent iron, trivalent aluminum, and tetravalent titanium and adjusting the alkalization degree. The resulting compounds were characterized via X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) to clarify their phosphorus removal mechanisms. Single-factor and orthogonal tests were conducted to determine the optimum conditions for phosphorus removal, after which the phosphorus-removing properties of the proposed material were assessed in actual wastewater. The optimum conditions for phosphorus removal were the following: coagulant dosage of 40 mg, wastewater pH of 9, and phosphorus wastewater concentration of 2 mg · L−1. Our proposed method could reduce the total phosphorus concentration of the secondary sedimentation tank effluent to below the detection limit. Moreover, the characterization results indicated that the synthesized PCAFT was a complex hydroxyl polymer of aluminum, iron, and titanium bridged by a hydroxyl group with good crystallinity and a cluster structure on its crystal surface, which enhanced the coagulation and phosphorus removal properties of the material.