Preparation of High-phosphorus Iron Ore Reference Materials for Chemical Composition Analysis

BACKGROUNDThe analysis and testing process of high-phosphorus iron ore requires quality control of standard materials with similar matrix components, moderate content and fixed value components. At present, there are no certified reference materials available for high-phosphorus iron ore chemical composition analysis in China. The available iron ore reference materials in China and abroad have different matrix compositions and phosphorus contents. Phosphorus content is mostly less than 0.25%, while phosphorus content in high-phosphorus iron ore is higher than 0.25%. It is difficult to meet the analytical quality control requirements of high-phosphorus iron ore products with these reference materials.

OBJECTIVESTo develop three high-phosphorus iron ore reference materials with contents of iron and phosphorus forming a certain gradient and covering the content range of high phosphorus iron ore.

CANDIDATES CHARACTERISTICS The sample GPFe-1 is composed of 40% metallic minerals, 25% quartz, 15% colloidal phosphate, 20% oolitic chlorite, clay mineral, apatite, carbonate minerals, rock debris and a small amount of organic matter. The metal minerals are hematite, limonite and pyrite.The contents of iron and phosphorus are 31%-37% and 0.1%-0.5%, respectively. The sample GPFe-2 consists of 40% hematite, 5% limonite, 55% gangue mineral, and minor collophanite and pyrite. The iron and phosphorus contents in GPFe-2 are 38%-44% and 0.6%-1.0%, respectively. The sample GPFe-3 is composed of 70% metallic minerals (hematite, limonite, pyrite), 5% quartz, 1% collophane, 3% chlorite, 1% cuttings, and minor apatite and calcite. The contents of iron and phosphorus in this sample are 48%-55% and 1.4%-2.0%, respectively.

METHODSThe samples of high-phosphorus iron ores were collected from the western Hubei Yelangping mining area in Zigui county of Yichang city, the Enshi Changling mining area (Wuhan iron and steel corporation mining area), and the Huoshaoping mining area in Changyang county of Yichang city (Bao Steel Group Changyang mining area). Uniformity and stability were tested for 25 components of SiO₂, Al₂O₃, TiO₂, P, K₂O, Na₂O, Fe, MnO, CaO, MgO, FeO, LOI, S, Cu, Pb, Zn, Cr, Ni, Co, Cd, Sr, Ba, V, As and Hg. Uniformity test was evaluated by variance analysis F test and relative standard deviation of test results. Stability test was evaluated by linear fitting and t-test.

RESULTSThree samples were homogeneous and stable. The RSD of major elements and trace elements of 3 samples was less than 5%. The F value of variance test was less than the critical value F_0.05(24, 25)=1.96, indicating that all the components of 3 samples were homogeneous. The stability test showed that the components of 3 samples had no directional change and statistically significant differences, indicating that the elements in the 3 samples were stable. The verified value was tested by 11 laboratories and by two or more different principles. The verified value components included 25 major elements and trace elements. Three components of Na₂O, S and Hg of GPFe-1 had reference values, whereas other 22 components had certified values and uncertainties. The contents of iron and phosphorus in GPFe-1 were 35.18%±0.20% and 0.285%±0.010%, respectively. Two components of Cd and Hg in GPFe-2 had reference values, and other 23 components had certified values and uncertainties. The contents of iron and phosphorus in GPFe-2 were 41.46%±0.20% and 0.735%±0.020%, respectively. Two components of FeO and Hg in GPFe-3 had reference values, while other 23 components had certified values and uncertainties. The contents of iron and phosphorus in GPFe-3 were 51.44%±0.13% and 1.73%±0.05%, respectively.

CONCLUSIONSThe developed high-phosphorus iron ore reference materials meet the requirements for exploration, evaluation, and comprehensive utilization of high-phosphorus iron ore.