China 
Africa 
Explore chapters and articles related to this topic
Fabrication and application areas of mixed matrix flat-sheet membranes
Published in Alberto Figoli, Jan Hoinkis, Sacide Alsoy Altinkaya, Jochen Bundschuh, Application of Nanotechnology in Membranes for Water Treatment, 2017
Derya Y. Koseoglu-Imer, Ismail Koyuncu
Aslan and Bozkurt (2014) prepared proton conducting nano-titania composite membranes. They also discussed the production and characterization of proton conducting super acid membranes. During membrane fabrication, sulfated nano-titania was firstly synthesized by hydrolysis and precipitation of titanyl sulfate (TS) and was then blended with sulfonated polysulfone (SPSU). The maximum proton conductivity of the prepared membrane was obtained as 0.002 S cm−1 at 150°C.
Preparation technology of Ti-rich material from ilmenite via method of vacuum carbothermal reduction
Published in Canadian Metallurgical Quarterly, 2019
Ke-Han Wu, Guo-Hua Zhang, Kuo-Chih Chou
Ilmenite and rutile are the main minerals for extraction of metallic titanium or titanium dioxide [1]. However, high-grade titanium minerals such as rutile have been substantially exhausted on earth. Therefore, utilisation of low-grade ilmenite should become the trend of the industry [2]. For upgrading the quality of Ti-rich material, several methods have been proposed, primarily focusing on destroying the structure of anosovite [3–5]. The treatments basically include oxidation roasting, reduction roasting, sulfuration, chlorination and salt roasting [6–12]. By these methods, impurities were subsequently removed by water or diluted hydrochloric acid leaching. Among them, two processes have been widely applied: sulfate technology and chloride technology [13–16]. The former one is acidolysis of ilmenite with sulfuric acid to obtain titanyl sulfate and then hydrolysis of titanyl sulfate to produce titanium dioxide [17]. In this process, a large amount of acid mist such as SO3 is produced, causing the problems of equipment corrosion and environmental pollution. The latter one is chlorination of ilmenite with chlorine gas at high temperatures and then condensation of TiCl4 [18]. It has the advantages of high quality of product and environmentally friendly. However, the chloride process has a high requirement for the quality of raw materials, especially low contents of elements Ca and Mg [19]. Ca or Mg could form liquid chlorides in the chlorination process, which could block fluidised bed, resulting in abnormal production or shutdown.
Red mud valorization an industrial waste circular economy challenge; review over processes and their chemistry
Published in Critical Reviews in Environmental Science and Technology, 2022
Basudev Swain, Ata Akcil, Jae-chun Lee
Piga et al. have reported a pyro- and hydro-metallurgical hybrid process flow sheet (depicted in Figure 12) for the recovery of Al, Fe, and Ti (Mishra & Gostu, 2017; Piga et al., 1993). In this process, the red mud was wet-mixed with CaCO3 and coal and then dried. The dried mixture was ground and sintered at 800–1,000 °C for reduction. The sintered mixture after the reduction was ground and water-leached at 65 °C for an hour. After separation from the liquid filtrate, Al was recovered/produced through the Bayer process by returning it to the ore processing step and closing the loop. The solid residue fraction contains Fe, Ti, and other metals. From the magnetic separation of the solid residue, the Fe can be separated and treated through the conventional smelting process, whereas the nonmagnetic fraction containing Ti can be leached by sulfuric acid as titanyl sulfate. From titanyl sulfate, TiO2 can be obtained by calcination. As represented in Figure 12, only Fe, Al, and TiO2 can be recovered from the red mud. The process emphasized the recovery of pig iron, titanium dioxide, and aluminum that existed in the red mud but failed to address the recovery of other important metals (Piga et al., 1993). Considering various issues associated with red mud and resource scarcity, important metals like REMs have never been focused by Piga et al. which opens the door for further recovery process development. The process chemistry reported by Piga et al. is quite similar to the process chemistry reported by Alkan et al. The Fe2O3 reduction chemistry is the same as explained by Equations (1–4). Aluminum recovery goes back to Brayer’s process and the process chemistry is very well understood. In the Ti recovery process, hydrolysis of Titanyl sulfate followed by calcination can be explained using Equations (38) and (39) given below. One should not be confused with different species for TiO(OH)2 in Equations (36–38) as it is dependent on the pH.