A review of the production cycle of titanium dioxide pigment

Titanium is a very important element for several industrial applications, being one of the ninth most abundant elements in the Earth’s crust (0.63% wt). In this work it will discuss the different mining and industrial activities involved in the production of titanium dioxide. The first step ana-lyzed will treat about the beneficiation mining process of titanium mineral, and secondly, it will discuss the two main processes of the TiO2 manufacturing (sulphate and chloride routes). In addi-tion, we will show different uses of the titanium dioxide pigment as filler in paper, plastics and rubber industries and as flux in glass manufacture, etc. Finally, we will show that the old wastes are currently called co-products since they were valorized, being commercialized by the Spanish industry of TiO2 production in different fields such as agriculture, civil engineering, or cement manufacturing.Government of Andalusia’s project “Characterization and modelling of the phosphogypsum stacks from Huelva for their environmental management and control” (Ref.: RNM-6300

Use of the red gypsum industrial waste as substitute of natural gypsum for commercial cements manufacturing

El objetivo de esta investigación ha sido analizar la valorización de un residuo generado en el proceso de producción de dióxido de titanio (vía sulfato), denominado yeso rojo, en la producción de cementos. Dicho residuo está compuesto fundamentalmente por sulfato de calcio di-hidratado e hidróxidos de hierro. Para ello, ha sido necesaria la caracterización físico-química del yeso rojo, así como la de los otros componentes fundamentales en la fabricación de cementos y de los cementos generados con el mencionado residuo. Además, en el caso del yeso rojo, se ha analizado su contenido radiactivo al generarse éste en una industria NORM (Natural Occurring Radioactive Materials). Posteriormente, se han estudiado las propiedades más importantes de los cementos producidos con diferentes porcentajes de yeso rojo añadido, comparando estas mezclas con las propiedades de un cemento Portland comercial, comprobándose que se cumplen todas las normas europeas de calidad exigibles.The main objective of this research has been the valorisation of a waste from the TiO2 production process (sulphate method), called red gypsum, in the production of cements. This waste is mainly formed by di-hydrate calcium sulphate and iron hydroxides. To cover this objective it has been necessary to perform the physicochemical characterisation of the red gypsum as well as the main components in the production of cements and of the new cements generated. Moreover, for the red gypsum, has been analyzed its radioactive content because it is generated in a NORM (Naturally Occurring Radioactive Materials) industry. Finally, the most important properties of the obtained cements with different proportions of red gypsum in their composition have been studied by comparing them with the standard ones obtained in a Portland cement. Lastly, we have demonstrated that the new cements fulfil all the quality tests imposed by the European legislation.This work has been supported by the PROFIT Project “Valorization of red gypsum from the industrial production of titanium dioxide” (CIT-310200-2007-47)

Characterization and applications of industrial wastes with highcontent of gypsum

The recycling of inorganic wastes generated by different industrial processes is a research field of high interest because the minimization of waste disposal, avoiding its potential release into the environment, can generate environmental and economical benefits for these industries and the general population. The appropriate treatment of industrial wastes could even lead to the generation of co-products of economic value and broad application. Obviously, the environmental and health impact of these co-products should comply with existing regulations.In this direction, the present study describes first the used raw materials ilmenite (ILM) and slag (SLAG) and a wasteknown as ―red gypsum‖ (RG) coming from a titanium dioxide industrial facility located at the province of Huelva (Spain), in terms of their elemental composition, radioactive contents,granulometry, mineralogy, microscopic morphology and physical composition. The main goal was to obtain basic information for future potential applications of the RG waste in construction, civil engineering, etc. One of these applications has been studied in the second part of our study: we have analysed the main properties of cements produced with different proportions of red gypsum, and their obtained improvements, in relation to Ordinary Portland Cements (OPC). In the produced RG cements, it has been also demonstrated that the levels of pollutants associated always remain within safety limits

Valorisation diagnosis of waste from the decontamination of phosphogypsum leachates through a combined calcium carbonate/hydroxide process

Phosphogypsum is an industrial waste considered as naturally occurring radioactive material. Stack disposal and exposure to the environmental condition involve the production of acid leachates with high potential pollutant loads as heavy metals and radionuclides. In this study, a sequential neutralisation process was applied for cleaning the generated releases, and the two obtained residues were characterised from the physical-chemical and radiological point of view before their valorisation. The cleaning process was made up of two steps: the first one using calcium carbonate until pH = 3.5, and the second one using calcium hydroxide until pH = 12. The residue obtained in the first step was mostly calcium fluoride, while in the second step most phosphates were precipitated, mainly as hydroxyapatite. The final liquid was treated to reduce pH lower than 9, which is the limit included in the current directive for discharges of liquid effluents into coastal waters. The main conclusion was that the solids from the first step could be valorised as an additive in the manufacture of commercial Portland cements and ceramics, while the solids from the second step could be used as raw material for the phosphoric acid manufacture