Experimental Simulation of Long Term Weathering in Alkaline Bauxite Residue Tailings

Abstract

Abstract:Bauxite residue is an alkaline, saline tailings material generated as a byproduct of the Bayer process used for alumina refining. Developing effective plans for the long term management of potential environmental impacts associated with storage of these tailings is dependent on understanding how the chemical and mineralogical properties of the tailings will change during weathering and transformation into a soil-like material. Hydrothermal treatment of bauxite residue was used to compress geological weathering timescales and examine potential mineral transformations during weathering. Gibbsite was rapidly converted to boehmite; this transformation was examined with in situ synchrotron XRD. Goethite, hematite, and calcite all precipitated over longer weathering timeframes, while tricalcium aluminate dissolved. pH, total alkalinity, and salinity (electrical conductivity) all decreased during weathering despite these experiments being performed under "closed" conditions (i.e., no leaching). This indicates the potential for auto-attenuation of the high alkalinity and salinity that presents challenges for long term environmental management, and suggests that management requirements will decrease during weathering as a result of these mineral transformations. OPEN ACCESSMetals 2015, 5 1242

Development of alkaline electrochemical characteristics demonstrates soil formation in bauxite residue undergoing natural rehabilitation

“…Hydrogarnet is the primary alkaline mineral (Table ), and quantification reveals that this mineral was gradually dissolved and converted to stable gibbsite (Equation ) due to its persistent dissolution characteristics (Santini, Fey, & Gilkes, ). For fresh bauxite residue, the calcite concentration was 10.0%, compared to 8.2% in the 20‐year‐old residue.…”

“…Transformations of hydrogarnet, cancrinite, and sodalite resulted in an increasing concentration of gibbsite (Table ). The gibbsite to diaspore transformation is well‐known (Murray, Kirwan, Loan, & Hodnett, ; Santini et al, ), naturally increasing diaspore concentrations in the aged residues. Results indicate that the concentration of diaspore was maintained at approximately 6.0%, suggesting that the transformation of gibbsite to diaspore was not activated through natural conditions (Table ).…”

“…Hydrogarnet is the primary alkaline mineral (Table 1), and quantification reveals that this mineral was gradually dissolved and converted to stable gibbsite (Equation 3) due to its persistent dissolution characteristics (Santini, Fey, & Gilkes, 2015 However, there was no obvious change to cancrinite until this period (Table 1) and may be attributed to its dissolution (Equation 2) during time from disposal. Tri-calcium aluminate dissolved more slowly than other buffering alkaline minerals.…”

Modelling Hydrological Performance of a Bauxite Residue Profile for Deposition Management of a Storage Facility

“…Bauxite residue is a caustic and high alkaline by-product of the Bayer process, where bauxite ore (aluminium containing mineral) is digested with high concentrations of NaOH (sodium hydroxide) under high pressure and heat to produce alumina, raw material for the production of aluminium [1][2][3]. Bauxite residue production can fluctuate from 0.3 to 2.5 tonnes per tonne of alumina produced, and as the utilization of bauxite residue is low, the majority of the material is discharged into a storage facility [4].…”

Hydrometallurgy

“…With a total of 22 papers covering both fundamental and applied research, this issue covers all aspects of hydrometallurgy from comprehensive review articles [1,2], theoretical modelling [3] and experimental simulations [4], surface studies of dissolution mechanisms and kinetics [5], pre-treatment by roasting [6] or carbonation [7] to enhance recovery, aqueous carbonation as a means of CO 2 sequestration [8], biological systems [9][10][11], solvent and liquid-liquid extraction [12][13][14], nanoparticle preparation [15,16] and the development of novel and/or environmentally sustainable methods for the treatment of wastes and effluents for the recovery of valuable metals and products [17][18][19][20][21][22]. The number and of quality of submissions makes this Special Issue of Metals the most successful to date.…”