Removal of carbonate and oxalate pollutants in the Bayer process using thermal and chemical techniques

Application of ultrasonic-enhanced active seed crystals in the removal of sodium oxalate from alumina refinery waste liquor

“…During the digestion process, some organic compounds existing in the bauxite feed will also react with caustic solution and enter the flat plate washing liquor. It is reported that the organic matters such as carboxylic cellulose, polysaccharides, lipids, and humic acids existing in bauxite (the grade organic carbon of bauxites appears an overall average of 0.27 %) are considered to be the main source for organics, and generate some organic acid anions after reacting with sodium hydroxide, e.g., acetates, aromatic compounds, such as high molecular weight carboxylic acid and humates [7] , [8] , [9] , [10] . In addition to humic acids, a small number of organics from the used flocculant, flotation and anti-foam agents are also present in the flat plate washing liquor.…”

“…For example, it can lower seed decomposition rate, reduce alumina production yield, prolong seed induction period, loss sodium hydroxide, decrease the particle size of aluminum hydroxide, and generate odor gases, with lowering the alumina whiteness and even diminishing the red mud settling rate [19] , [22] , [23] , [24] , [25] , [26] , [27] . Given the considerable hazards caused by the organics to the Bayer process, much attention has been paid to the treatment of organic compounds from sodium aluminate solution including thermal treatment [25] , chemical precipitation [10] , photocatalytic degradation [28] , membrane separation [11] , and wet oxidation methods [29] . Among them, wet oxidation process is regarded as the common method available for the removal of organics from sodium aluminate liquor due to its efficient removal, extensive source of raw materials and green operation.…”

Archives of Mining Sciences

“…in the iran alumina plant, diasporic bauxite with sodium hydroxide and about 8 to 12% of lime (relative to the amount of bauxite) were inserted into tubular ball mills, and the produced slurry enters the pre-desilication stage. Mahmoudian et al (2015) mentioned two impurities of carbonate and oxalate as the main impurities in the process of this plant. they recommended using chemical methods by ba2Al4(oH)16 and heating as effective methods for removing carbonate and oxalate impurities, respectively [10].…”

“…Mahmoudian et al (2015) mentioned two impurities of carbonate and oxalate as the main impurities in the process of this plant. they recommended using chemical methods by ba2Al4(oH)16 and heating as effective methods for removing carbonate and oxalate impurities, respectively [10]. the lime for this process is produced in two parallel flow regenerative shaft kilns (pFr).…”