Phosphorus Removal From Calcified Converter Vanadium Slag Acidic Leaching Liquor

The valence of vanadium is very important strategic mineral resources. Vanadium can improve the strength and toughness of steel. Just adding 0.1 wt% vanadium in structural steel can improve the strength of 10 20%, lower the structure weight 15 25%, and reduce the cost of 8 10%. About 90% of vanadium is used for iron and steel industry in our country. Because vanadium steel has good strength, toughness, wear resistance and corrosion resistance characteristics, it is widely used in the oil?gas? pipeline, buildings, bridges, steel and pressure containers in the engineering construction. In the new clean vanadium extraction technology, calcification of converter vanadium slag formed acidic vanadium leaching solution after roasting and acidic leaching, the preparation of vanadium leaching solution is one of the important process in cleaning process of vanadium extraction, and contains a certain amount of phosphorus. Phosphorus is the harmful element in the process of iron and steel production, and it will reduce the steel welding performance, plasticity, cold bending resistance, toughness, etc., then the quality of the steel products is poor. So developing the effective phosphorus removal technology, improving the purity and quality of the vanadium end products is of great significance to promote the sustainable development of vanadium industry.In this work, the converter vanadium slag used for calcified roasting was obtained from Pangang, Panzhihua City. The primary composition contained 4.57 wt% V, 0.29 wt% P, and a large number of impurities such as Fe, Si, Ti, Mn element. Vanadium in the converter slag mainly exists in the FeVO₄ spinel phase, and phosphorus is mainly in the form of focal calcium dihydrogen phosphate and calcium phosphate. When the calcification of converter vanadium slag was leached by sulfuric acid, the leaching solution mainly contained PO₄^3-, a small amount of P₃O₁₀^5- and polyphosphates.Chemical precipitation method was used to remove phosphorus from the calcification of converter vanadium slag sulfuric acidic leaching solution in this work. Reagents, reaction conditions were mainly studied. Phosphorus removal reagents, suitable reagent dosage and the optional reaction conditions on phosphorus removal efficiency were determined.The experimental results showed that the phosphorus removal efficiency were only 78% and 64.13% with CaSiO₃ and Al₂?SO₄?₃·18H₂O, and the phosphorus concentration is still very high in the phosphorus removed vanadium leaching solution. Phosphorus removal efficiency reached 88.76% under the conditions a Fe/P molar ratio of 1.0 at 50 °C for 60 min by using the polymeric ferric sulfate, the phosphorus concentration was decreased from 783 mg/L to 88 mg/L in the acidic leaching solution. Polymeric ferric sulfate and aluminum sulfate composed the composite phosphorus removal reagent. Al³⁺ can promote the hydrolysis and convert the complex-structured polyphosphates into simple-structured PO₄^3-. Phosphorous was removed by the co-precipitation of Al³⁺, Fe³⁺ and OH^-, and PO₄^3-, as well as by the adsorption effect of hydroxyl-containing iron complex compounds. The phosphorus removal efficiency was 91.09% under the optimum conditions, including a Fe/Al/P molar ratio of 0.6:0.4:1 at 50 °C for 60 min, and the phosphorus concentration was decreased from 874 mg/L to 76 mg/L.Phosphorus removal precipitates were analyzed and characterized by XRD, FT-IR to determine the mechanism of phosphorus removal. The hydrolysis of Fe³⁺ and Al³⁺ produced a large number of metal hydroxy complexes, which absorbed a mass of phosphate to generate the metal phosphates with amorphous structure.