Cleaner alumina production from coal fly ash: Membrane electrolysis designed for sulfuric acid leachate. (10th January 2020)

• Record Type: Journal Article
• Authors: Shi, Yuan; Jiang, Kai-xi; Zhang, Ting-an; Lv, Guo-zhi
• Is Part Of: Journal of cleaner production. Volume 243(2020)
• Publication Date: 2020-01-10
• Subjects: Coal fly ash -- Membrane -- Electrolysis -- Aluminum hydroxide -- Sulfuric acid; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2019.118470
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: The clean and efficient extraction of alumina from coal fly ash renders environmental and economic benefits. The current study mainly aimed to develop a nonhazardous approach to conduct electrolysis with two-membrane and three-chamber cell for alumina extraction from coal fly ash. The influences of the aluminum sulfate concentration, distance between electrodes, current density, temperature and electrolysis duration were systematically explored. The results revealed that Al(OH)3 was a main electrolytic product with a yield of 64.48% and the energy consumption was 4.88 kWh/kg Al(OH)3 after 20 h of electrolysis process. The concentrations of ions were determined by inductively coupled plasma atomic emission spectrometry, indicating that Al 3+ in the middle chamber migrated to the cathodic chamber to form Al(OH)3 precipitate under the combined action of direct current and the exchange membranes. The electrolysis mechanism was analyzed by cyclic voltammetry, which showed that H2 O gained electrons and reacted with Al 3+ on the cathode to form Al(OH)3 and H2 . On the anode side, H2 SO4 and O2 were generated due to the oxidation of H2 O. Al(OH)3 is an alumina resource, H2 is a clean energy, and H2 SO4 is a common coal fly ash leaching agent and can be returned to the leaching process to promote zero pollution discharge. The solution in the middle chamber can be refreshed to attain continuous electrolysis. The proposed electrolysis process provides an efficient and environmentally friendly approach for the extraction of high-quality Al(OH)3 from coal fly ash. Highlights: A specific scheme was designed to recover alumina from coal fly ash by membrane electrolysis. The mechanism of membrane electrolysis was deeply analyzed by cyclic voltammetry. The product sulfuric acid can return to the leaching process to promote zero pollution discharge.