Method for preparing phosphorus and magnesium doped polyaluminum chloride flocculant by utilizing secondary aluminum ash

Abstract

The invention discloses a method for preparing a phosphorus and magnesium doped polyaluminum chloride flocculant by using secondary aluminum ash, which comprises the following steps: mixing sodium phosphate, calcium oxide and aluminum ash to obtain a phosphorus and calcium doped aluminum ash mixture; mixing a magnesium chloride aqueous solution and the phosphorus-calcium-doped aluminum ash mixture, and sealing and stirring to obtain fluorine-ammonia fixing mixed slurry; mixing a hydrochloric acid aqueous solution with the fluorine-fixing ammonia mixed slurry, sealing, heating and stirring to obtain acid leaching mixed slurry; and adding calcium aluminate into the acid leaching mixed slurry, mixing, stirring and aging, and drying and grinding in a roller to obtain the phosphorus and magnesium doped polyaluminum chloride flocculant. According to the phosphorus and magnesium doped polyaluminum chloride flocculating agent and the application thereof, efficient utilization of the secondary aluminum ash can be achieved, additional denitrification and desalination steps are not needed in the aluminum ash treatment process, and full utilization of all components in the aluminum ash can be achieved. Compared with the traditional polyaluminum chloride, the phosphorus and magnesium doped polyaluminum chloride flocculant prepared by the invention has higher adsorbability, and can adsorb 346.73 mg / g COD and 52.24 mg / L lead at most.

Description

technical field [0001] The invention belongs to the field of resource utilization of hazardous waste, and in particular relates to a method for preparing a phosphorus- and magnesium-doped polyaluminum chloride flocculant by using secondary aluminum ash. Background technique [0002] Every ton of aluminum products produced and processed (involving electrolysis, smelting, metal processing, recycling, etc.) will produce 180-290kg of aluminum ash. Based on the metal aluminum content, aluminum ash is further divided into primary aluminum ash and secondary aluminum ash. Primary aluminum ash (commonly known as white ash) mainly contains metallic aluminum and alumina, and its metallic aluminum content is high and has recycling value. In the industry, the metal aluminum particles in the primary aluminum ash are mainly recovered by crushing, grinding, and sieving. Secondary aluminum ash (commonly known as black ash) is produced by recycling aluminum or aluminum alloy refining proces...

AI Technical Summary

Problems solved by technology

Secondary aluminum ash mainly contains alumina, silicon oxide, salt flux and other substances, and the main phase includes Al 2 o 3 , Al, MgAl 2 o 4 , AlN, NaCl, Al(OH) 3 , CaF 2 etc., are reactive and toxic, and are likely to have adverse effects on the ecological environment

AlN in secondary aluminum ash easily reacts with water to form aluminum hydroxide and release ammonia, while NaCl and CaF in aluminum ash 2 The existence of aluminum ash limits the massive use of aluminum ash in cement building materials and other resource industries

In the past two years, the process of preparing PAC with aluminum ash as raw material is only to replace the aluminum source material and supplemented by the traditional acid leaching method. The preparation process needs to consider the problem of ammonia released by the AlN reaction. At the same time, the ammonium ion of the prepared PAC product , free fluorine, free chlorine and other harmful impurities are high, and the performance of PAC products is poor

These problems undoubtedly limit the application of aluminum ash in the field of flocculant recycling

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