A Review of the Commercial Uses of Sulphate Minerals from the Titanium Dioxide Pigment Industry: The Case of Huelva (Spain)

• Main Authors: Manuel Jesús Gázquez, Manuel Contreras, Silvia María Pérez-Moreno, Jose Luis Guerrero, Melquiades Casas-Ruiz, Juan Pedro Bolívar
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Minerals
• Subjects: TiO₂ industry; ferrous sulphate heptahydrate; ferrous sulphate monohydrate; red gypsum; uses of sulphate minerals; NORM industries
• Online Access: https://www.mdpi.com/2075-163X/11/6/575

This study was focused on the historical evolution of the waste management policy carried out by the Spanish industry devoted to titanium dioxide pigments manufacturing for minimising its environmental impact. This challenge was achieved by modifying the original chemical process and converting the originally dissolved sulphate and sulphuric acid present in the final streams of the factory into sulphate minerals (melanterite FeSO₄·7H₂O, szomolnokite FeSO₄·H₂O, and gypsum CaSO₄·2H₂O). These by-products were physicochemically, mineralogically and radiologically characterised in order to gain basic information for its subsequent commercial use. Some of the uses summarised in this study for both ferrous sulphates are as a supplier of iron to prevent chlorosis, animal food, manufacture of cement (to reduce Cr VI), primary flocculants for ferrous sulphates, magnetite nanoparticle and nano-Fe₂O₃ formation, production of magnetite concentrate, remediation of polluted soils with metals, and treatment of wastewaters. Red gypsum was analysed as a substitute for natural gypsum in the manufacture of cement, construction materials, inhibitor in soil erosion, and the immobilisation of heavy metals in agricultural soils and carbonation processes.