Phosphorus Removal From High-phosphorus Manganese Leach Liquor

The rapidly increasing development of steel and iron industries in China promotes the dramatically development of electrolytic manganese metal industry, and stimulates the daily increasing demand of the manganese ore resources. At present, poor-quality manganese ore resources, particularly high phosphorus manganese ores are increasing.Poor-quality ores contain complex mineral components, high amounts of harmful impurities and difficult exploitation, and the features severely restrict the industrial economic development. Phosphorus is the harmful substances during the steel and iron production process. Because it can reduce the steel welding performance, plasticity,cold bending resistance, toughness, etc., then influence the quality of the steel products.Therefore, it is great significant to develop the effective phosphorus removal technology and improve the utilization rate of low grade high phosphorus manganese ore resources to promote the sustainable development of the manganese industry.In this thesis, the high phosphorus manganese ore came from Cheng Kou in Chongqing. The primary composition contained 10.54% Mn, 6.39% P, 0.391 P/Mn and a large number of impurity elements. Manganese phase was mainly manganese carbonate. Phosphorus was mainly present in apatite and cellophane with the form of calcium phosphate, hydroxy calcium phosphate and calcium pyrophosphate. When high phosphorus manganese ore was leached by sulfuric acid, apatite dissolved and the p H reduced to increase the acidity, accelerating the pyrophosphate transform into orthophosphate. As a result, high phosphorus manganese ore leach liquor mainly contained PO43- and a small amount of P2O74-.Chemical precipitation method was used to remove phosphorus from the high phosphorus manganese ore leach liquor in this paper. Kinds and dosage of phosphorus removal reagent, reaction p H conditions were mainly studied. Phosphorus removal reagents, suitable reagent dosage and reaction p H conditions affecting on phosphorus removal efficiency were determined.Calcium oxide(Ca O) and ferrous sulfate(Fe2+) failed to facilitate phosphorus removal from the acidic high phosphorus manganese ore leach liquor. The optimal condition for phosphorus removal with Ferric sulfate(Fe3+) was attained at p H 3~5,Fe/P molar ratio of 1.5~2, and phosphorus removal efficiency reached over 99.64%.Phosphorus removal efficiency over 99.83% were obtained at p H 3~5, Fe/P molar ratioof 2, H2O2/Fe molar ratio of 0.5~1, and phosphorus concentration in mother liquor was less than 13.32 mg/L by using the ferrous sulfate/hydrogen peroxide method(Fenton method). Phosphorus removal efficiency over 99.76%~99.9% were obtained at p H 3~5,Fe/P molar ratio of 0.75~1.0 by using the polymeric ferric sulfate. Aluminum sulfate was used remove phosphorus to acquire phosphorus removal efficiency over 99.71%under the optimal condition of p H=4~5 and Al/P molar ratio of 1.0.Polymeric ferric sulfate and aluminum sulfate composed the composite phosphorus removal reagent. When added metal ions satisfied the condition of n(M/P)=n(Al/P)+n(Fe/P)>0.7, good phosphorus removal efficiency would be obtained;The less aluminum sulfate was added and the more polymeric ferric sulfate was added,phosphorus concentration in mother liquor was less than 21.7 mg/L and the higher phosphorus removal efficiency was reached to meet the requirement. The polymeric ferric sulfate, aluminum sulfate and lanthanum oxide composed the ternary phosphorus removal reagent. La3+ can effectively enhance the phosphorus removal efficiency compared with the polymeric ferric sulfate and aluminum sulfate composite under the same conditions.Phosphorus removal precipitates were analyzed and characterized by XRD, XRF,FT-IR to determine the mechanism of phosphorus removal. The hydrolysis of Fe3+,Al3+and La3+produced a large number of metal hydroxy complexs, which absorbed a mass of phosphate to generate the metal phosphates with amorphous structure.Meanwhile, some Mn2+ was inevitably lost because of the adsorption of metal hydroxy complexs.