Enhancement of bauxite residue as a low-cost adsorbent for phosphorus in aqueous solution, using seawater and gypsum treatments

Abstract

address: 18 mark.healy@nuigalway.ie 19 20Highlights 21  Separate size fractions of bauxite residue were treated with gypsum and seawater. 22  Alkalinity was reduced following treatment with the gypsum and seawater. 23  The effect on composition and P adsorption of the treated samples were examined. 24  Gypsum was found to be the most successful in enhancing the P adsorption capacity. 25 26 2 Abstract 27Bauxite residue (red mud), the by-product produced in the alumina industry, is being 28 produced at an estimated global rate of approximately 150Mt per annum. Due to its highly 29 alkaline nature, many refineries use neutralisation techniques such as mud farming 30 (atmospheric carbonation), direct carbonation using carbon dioxide or reactions with 31 seawater, to treat the bauxite residue and reduce its alkalinity prior to disposal in the BRDA 32 (bauxite residue disposal area). Applying a treatment can render the bauxite residue non-33 hazardous and may also prepare the bauxite residue for reuse, particularly as an adsorbent. In 34 this study, gypsum and seawater treatments were applied to the various bauxite residue 35 samples obtained and the effects on its mineral, elemental and physiochemical properties 36 were examined, as well as the effect on its phosphorus (P) adsorption capacity. It was found 37 that in addition to reducing the alkalinity of all bauxite residue samples used, the P adsorption 38 capacity was also enhanced following amendment with seawater or gypsum, particularly with 39 gypsum. A positive correlation was detected between P adsorption and both Ca and CaO. A 40 negative correlation was detected between the P adsorption and pH of the media. Fitting the 41 data obtained from a batch adsorption experiment to the Langmuir adsorption isotherm, the 42 maximum adsorption capacity was estimated to range from 0.345 to 2.73 mg P per g bauxite 43 residue, highlighting the re-use potential for bauxite residue as an adsorbent for P. 44 45 Keywords: bauxite residue; adsorption; bauxite residue filter; aqueous solution; phosphate 46 removal 47 48 49 50 51 421 18

Soil quality and vegetation performance indicators for sustainable rehabilitation of bauxite residue disposal areas: a review

“…Phosphate adsorption increases with decreasing pH (Phillips and Chen 2010). This high P fixation capacity of residues has led to pilot trials on its use as an absorbent to remove P from P-rich wastewaters (López et al 1998;Snars et al 2004;Cusack et al 2018) and for land application to sandy soils to prevent leaching losses of P (Summers et al 1996). The low P content and high P fixation capacity of most residues means that P status is low and tends to decline over time (Bendfeldt et al 2001).…”

A Review on Comprehensive Utilization of Red Mud and Prospect Analysis

“…CaO/Ca(OH)2 is used to replace Na2O Equations (6) and (7) in sodalite and cancrinite. Then, CO3 2− and Al(OH) 4− in RM are cemented out in the form of CaCO3 and hydrocalumite.…”

“…For 1 t of alumina produced, approximately 1.5 t of RM is discharged [4]. According to the statistics, the global stock of RM has reached nearly 4 billion tons by 2015 [5], and also with the annual production increasing by approximately 150 million tons [6,7]. In China, the amount of RM discharged is 88 million tons per year, and the total stock of RM is over 0.6 billion tons [8].…”

Investigation of Phosphate Removal Capability of Blast Furnace Slag in Wastewater Treatment

“…Although considered as a waste product, the slag has specific properties and chemical content that makes it valuable in several applications. According to the European Commission, management of by-products of the industry is important for the circular economy, therefore emphasis is placed to investigate alternative methods for waste management of industry by-products 2 . The reuse of BFS as a part of other industries reduces environmental contaminants, energy consumption 3 and production costs 2,4 .…”