Mechanism of phosphorus removal by activated alumina adsorption

Phosphorus in sewage wastewater is one of the important pollutants of water eutrophication in China, and reducing phosphorus discharge and strengthening the comprehensive treatment of phosphorus-containing wastewater is an important way to reduce eutrophication of inland rivers, lakes and other water bodies in China and ensure the safety of drinking water sources. In China, because the content of organic pollutants in surface water is high, it still contains higher organic matter after treatment by the water plant, and it is easy to form bacteria in the drinking water pipe network system, affecting the quality of drinking water. When the mass concentration of orthophosphate in drinking water is reduced to less than 10g/L, it can be useful to control the growth of bacteria in drinking water. In recent years, China has done a lot of effective operations in the treatment of phosphorus-containing wastewater, and has also achieved a good treatment role, but it will mainly focus on the research of medium and high concentrations of phosphorus-containing wastewater, and the treatment methods are mostly biological and chemical, but it is difficult to reduce the phosphorus mass concentration to less than 0.1mg/L, which is not suitable for the treatment of low-concentration phosphorus-containing wastewater and the phosphorus reduction and bacteriostasis of drinking water. The adsorption method has gradually attracted people's attention because of its simple equipment, reliable operation, recoverable phosphorus resources, no secondary pollution, high efficiency and low consumption, and is suitable for the treatment of low-concentration phosphorus-containing wastewater. Among the many varieties of adsorbents, synthetic adsorbents have outstanding adsorption capacity advantages. As a synthetic solid adsorbent with large surface area, good adsorption performance, good strength and chemical stability, and good thermal stability, activated alumina is gradually used in the treatment of low-concentration phosphorus-containing wastewater and the process of phosphorus lowering and bacteriostasis in drinking water.

Activated alumina has strong adsorption and hygroscopicity, and is a relatively complete and practical phosphorus removal adsorbent. It is generally thought that the mechanism of activated alumina adsorption and dephosphorization is: the surface molecules of activated alumina combine with water to form aluminum hydroxide, and then generate ion exchange with phosphate ions to generate phosphate. The surface complexation adsorption theory believes that the aluminum ions on the solid surface of activated alumina first complexe with the ligand water molecules, and the complexed ligand water molecules produce a proton migration process on the oxide surface to form the surface hydroxyl group. With the difference of pH value of aqueous solution, hydroxylated oxide surface adsorbs H+ or OH- ions without characteristics, resulting in a charged phenomenon, and the adsorption of activated alumina has the dual role of ion exchange and electrostatic adsorption.