Recovery of Phosphoric Acid and Calcium Phosphate from Dephosphorization Slag

Abstract

We previously reported that by adding aqueous ammonia to the nitric acid extract of dephosphorization slag, a solid with relatively high concentrations of calcium and phosphorus could be obtained. However, the solid contains considerable amounts of manganese and iron, which hinder its application in production processes. In the present study, the obtained solid was again dissolved in nitric acid, and the resultant ltrate was passed through a cation exchange resin that removed most unwanted cations from the aqueous phosphoric acid solution. The recovery of phosphoric acid was con rmed via phosphorus nuclear magnetic resonance. Furthermore, when calcium nitrate was added to this aqueous solution, calcium hydroxyapatite was obtained, which was converted into calcium phosphate after calcination at 1073 K. Phosphoric acid, calcium hydroxyapatite, and calcium phosphate are raw materials used to produce various industrial products containing phosphorus, and our suggested process signi cantly improves the technology for recovering phosphorus-containing materials, which are mostly used as fertilizers.

Study on Mechanism of MSWI Fly Ash Solidified by Multiple Solid Waste-Based Cementitious Material Using the Rietveld Method

“…Desulfurization ash (DA) is a solid waste generated during the dry flue gas desulfurization process, with CaO and SO 3 as the main components [29,30]. Phosphoric acid sludge (PAS) is an industrial solid waste obtained from the production of wet phosphoric acid [31,32]. PAS can be used to immobilize MSWI fly ash due to the widespread use of phosphate as a curing agent [33][34][35].…”

Key Factors for the Separation of Silicon and Iron During Phosphorus Recovery From Slag Discharged From the Double-Slag Refining Process

“…Compared with the processes used by conventional plants, this new approach reduces the amount of CO2 generated by increasing the amount of scrap used in converters. 20 The method of recovering phosphorus from DRP slag is similar to that from dephosphorization slag [12][13][14] and sewage-sludge molten slag, 19 and is a technique that combines acid-dissolution, alkali-precipitation, and ion-exchange. As a typical example, in the first acid-elution process (Process (1)), 1.0 g of DRP slag (particles less than 74 m) was dissolved in 100 mL of 0.5 M HNO3 at 298 K. This aqueous solution was stirred at 130 rpm for 24 min, which was determined to be optimal processing in the present study.…”

“…However, our laboratory aims to recover phosphorus in a form that could be used as a raw material for manufacturing foods, pharmaceuticals, and advanced materials. Thus far, our laboratory has investigated the recovery of phosphorus from slag released by a chemical factory, 11 dephosphorization slag, [12][13][14] solid unused resource collected in a filter bags during the recycling of used fluorescence tubes, 15 composted chicken manure, 16 incineration ash of chicken manure, 17,18 and sewage-sludge molten slag. 19 As part of a series focused on this study, this paper reports the results of phosphorus recovery from the double-slag refining process slag discharged from a modern steelmaking process.…”