RESUMEN
Identification of iron ore brand is one of the most important precautions against fraud in the international iron ore trade. However, the identification of iron ore brand can be sophisticated, due to fact that the role played by multi-component in iron ore brand identification was unclear. This study aims to establish an objective approach to identify iron ore brands based on their multi-component content. A total of 1469 batches of iron ore samples, covering 16 commonly consumed iron ore brands from 3 countries, were analyzed for multi-component content. It was investigated that 10 primary, minor, and trace chemical components varied significantly in contents according to different iron ore brands. This prospective relationship between the multi-component contents and the iron ore brand was then used to place 16 brands into 12 groups and 8 brands of them were correctly identified by a flowchart. Furthermore, chemometric tools such as linear discriminant analysis (LDA), k-nearest neighbor (k-NN), and support vector machine (SVM) were applied to construct models to simultaneously discriminate 16 iron ore brands. Both the training and test results proved that LDA performed best in this circumstance. In the LDA method, MgO, Fe, SiO2, and P are the feature components contributing the most to the identification of 16 brands of iron ore. Based on the findings, the multi-components are distinct variables to establish an internationally recognized model of iron ore brand identification.
RESUMEN
It has been 36 years since ISO 4298:1984 was published, yet the role of sodium pyrophosphate in the oxidation of manganese(II) by potassium permanganate in this standard has not been fully recognized. The sample and reagent dosages exceed the actual detection needs, which creates challenges in the test operation and waste liquid treatment. In this study, a more scientific expression for the principle and reaction and the dosage of pyrophosphate in ISO 4298:1984 are discussed. The pyrophosphate ligand is involved in the oxidation of manganese(II) by potassium permanganate, and plays a role in preventing Mn(II) precipitation or Mn(III) dismutation during the whole reaction. The most appropriate amount of saturated sodium pyrophosphate is 150 mL for the test of manganese ores and concentrates with manganese content from 15% to 60%. The method developed by reducing sample size and reagent consumption was evaluated with ten certified reference materials, showing high accuracy and meeting the analytical performance requirements. These results can provide technical support for the revision of ISO 4298:1984. Graphical abstract.
RESUMEN
Application of biochar-based fertilizers is increasingly being considered for its potential agronomic and environmental benefits. However, biochar may contain residues of polycyclic aromatic hydrocarbons (PAHs) as a result of its production by pyrolysis. The strong adsorption of PAHs to biochar makes extraction and analysis of biochar-based fertilizers difficult. This study optimizes the extraction of PAHs in biochar-based fertilizer samples by using an ultrasonic bath for quantification by gas chromatography-mass spectrometry. Among 12 solvents, acetone-cyclohexane (1:1) mixture was selected as the optimum solvent for extraction. Three variables affecting the extraction were studied by Box-Behnken design. The optimum conditions were 57 °C extraction temperature, 81 min extraction time, and two extraction cycles, which were validated by assessing the linearity of analysis, LOD, LOQ, recovery, and levels of PAHs in real biochar-based fertilizer samples. Results revealed that the 16 U.S. EPA PAHs had good linearity, with squared correlation coefficients greater than 0.99. LODs were low, ranging from 2.2 ng g(-1) (acenaphthene) to 23.55 ng g(-1) (indeno[1,2,3-cd]perylene), and LOQs varied from 7.51 ng g(-1) to 78.49 ng g(-1). The recoveries of 16 individual PAHs from the three biochar-based fertilizer samples were 81.8-109.4 %. Graphical Abstract Use of RSM to optimize UAE for extraction of the PAHs in biochar-based fertilizer.