Fate of inorganic contaminants post treatment of acid mine drainage by cryptocrystalline magnesite: Complimenting experimental results with a geochemical model

Masindi, Vhahangwele; Gitari, Wilson M.; Tutu, Hlanganani; Beer, Marinda De

doi:10.1016/j.jece.2016.03.020

Cited by 28 publications

(9 citation statements)

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“…Due to its high Mg content, amorphous and cryptocrystalline magnesite could be a possible source of Mg 2+ and Ca 2+ for the removal of phosphate and ammonia from aqueous matrices. These materials have been explored for mine water treatment and the management of other contaminants (Masindi, 2017;Masindi et al, 2016a;Masindi et al, 2018a;Masindi et al, 2018b;Masindi et al, 2016b). Specifically, Masindi et al (2016a) highlighted that cryptocrystalline magnesite, and its pre-treated derivative (Magagane et al, 2019), are characterised of Mg, Ca, Fe and Si sandwiched together, hence giving it an up-hand due to hybrid properties therein.…”

Section: Introductionmentioning

confidence: 99%

Wastewater treatment valorisation by simultaneously removing and recovering phosphate and ammonia from municipal effluents using a mechano-thermo activated magnesite technology

Mavhungu

Mbaya

Masindi

et al. 2019

Journal of Environmental Management

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Phosphate and nitrate enrichment largely impair aquatic ecosystem functions and services, thus comprising an emerging problem of environmental concern. The problem pertains to developing countries where phosphate and nitrate discharge to surface water is on the rise due to a rapid growth in population. Herein, these pollutants (phosphate and ammonia) were removed from real municipal wastewater using a simple, fast, and cost-effective process. Raw cryptocrystalline magnesite, a mineral abundant in South Africa, was simply milled and calcined (mechano-thermo processing) in order to produce the activated magnesite (feed). The feed was then used in batch processing for pollutants adsorption and precipitation from real wastewater. The process was optimised by varying the treatment or contact time, feed dosage, concentration, pH, and temperature. The feed and product mineral (produced sludge) were characterised using X-ray Diffraction (XRD), field emission scanning electron microscopy (FESEM) compatible with energy dispersive spectroscopy (EDS), and Fourier Transform Infrared Spectrometer (FTIR). It was identified that the optimal conditions differed for each pollutant, highlighting the importance of tailoring the process to fit the local wastewater characteristics and as part of a treatment train system. Specifically, maximum P removal was achieved after 5 min of mixing, using 1 g L-1 of feed, 123 mg L-1 initial phosphate concentration, pH 8-10, and was not affected by temperature variations; whereas, for ammonia removal, optimal conditions were 180 min, 16 g L-1 feed dosage, 80 mg L-1 initial concentration, pH 10 and temperature > 45 °C. The optimal conditions for the removal of both pollutants from real wastewater were 30 min, 8 g L-1 dosage, 7.5 pH, 35 o C. Furthermore, Mg and Ca concentration was found to influence the process. Reduction in total dissolved solids and electrical conductivity suggest an attenuation of chemical species. Characterisation revealed that the product mineral obtained under the optimal conditions for pollutants removal is rich in quartz, periclase, brucite, calcite, magnesite, and struvite. This was further supported by the FTIR results, which indicated the presence of Mg-O, PO 4 3− , N-H and-OH stretches. In addition, the EDS verified the presence of Mg, Ca and P in product mineral. Results are suggestive of the high efficiency of the mechano-thermo activated magnesite treatment process for P and N removal and struvite crystallization. Thus, this technology could valorise municipal wastewater effluents and open new horizons for the

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Section: Introductionmentioning

confidence: 99%

Wastewater treatment valorisation by simultaneously removing and recovering phosphate and ammonia from municipal effluents using a mechano-thermo activated magnesite technology

Mavhungu

Mbaya

Masindi

et al. 2019

Journal of Environmental Management

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“…From the FTIR spectra of raw and MB, DR81, MO and CV reacted calcined magnesite it can be affirmed that these spectra are more similar, they only differ on the development of a new band at 3694 cm −1 . Raw magnesite shows a system of bands characteristic of periclase stretching vibration corresponding to band 1450 and 880 cm −1 ( Masindi et al., 2015 ). The vibration at 1450 cm −1 , also supports the presence of carbonate materials including CaCO 3 (calcite) and MgCO 3 (magnesite).…”

Section: Resultsmentioning

confidence: 99%

Calcined magnesite as an adsorbent for cationic and anionic dyes: characterization, adsorption parameters, isotherms and kinetics study

Ngulube

Gumbo

Masindi

et al. 2018

Heliyon

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The ability of calcined magnesite for Methylene Blue (MB), Direct Red 81 (DR81), Methyl Orange (MO) and Crystal Violet (CV) dye removal was evaluated in this study. The experiments were designed to test the hypothesis that alkaline earth carbonates can remove dyes from water through a combination of sorption and coagulative reactions involving Mg2+. To achieve that, several operational factors like residence time, dosage, adsorbent concentration and temperature were appraised. The batch study proved that calcined magnesite is effective in the treatment of MB, DR81, CV and MO contaminated water and moreover it performed well in terms of color removal. The adsorption equilibrium data were analysed by the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin isotherm models, and the Dubinin–Radushkevich and Temkin models were found to be the most appropriate fit to MB and MO dyes respectively. The adsorption kinetics process primarily followed the Elovich and Pseudo-second order model, a possible indication that chemisorption was the rate limiting step during the dye uptake process. With the adsorption–desorption cycle repeated four times, the calcined magnesite regeneration efficiency for DR81 and MO loaded dyes remained very high. According to the results of this study, it can be concluded that calcined magnesite can be used effectively for the adsorption of MB, DR81, CV and MO from wastewater.

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“…The calcined magnesite was then remilled (15 min at 500 rpm) and passed through a 32 microns perforated sieve to obtain the desired particle sizes suitable for struvite precipitation. The thermally activated magnesite (feed thereafter) is rich in MgO, while after calcination new phases are formed in the feed, such as periclase, brucite, and calcite (Masindi et al, 2016a;Mavhungu et al, 2019). These will be dissolved in the wastewater, leading to an increase in the pH of the supernatant (Masindi, 2017), which is favourable for struvite precipitation (Mavhungu et al, 2019).…”

Section: Thermal Activation Of the Raw Cryptocrystalline Magnesitementioning

confidence: 99%

“…calcination reduces the particle size of the non-reactive magnesite and increases the surface area and reactive sites (Magagane et al, 2019). Due to its large surface area and reactive sites the feed has been also used for the remediation of acid mine drainage (AMD) as well (Masindi et al, 2016a). The mineralogical characteristics, along with the elemental and microstructural properties of the feed can be found elsewhere (Masindi et al, 2016b;Masindi et al, 2018b).…”

Section: Thermal Activation Of the Raw Cryptocrystalline Magnesitementioning

confidence: 99%

Environmental sustainability of municipal wastewater treatment through struvite precipitation: Influence of operational parameters

Mavhungu

Foteinis

Mbaya

et al. 2021

Journal of Cleaner Production

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Fate of inorganic contaminants post treatment of acid mine drainage by cryptocrystalline magnesite: Complimenting experimental results with a geochemical model

Cited by 28 publications

References 50 publications

Wastewater treatment valorisation by simultaneously removing and recovering phosphate and ammonia from municipal effluents using a mechano-thermo activated magnesite technology

Wastewater treatment valorisation by simultaneously removing and recovering phosphate and ammonia from municipal effluents using a mechano-thermo activated magnesite technology

Calcined magnesite as an adsorbent for cationic and anionic dyes: characterization, adsorption parameters, isotherms and kinetics study

Environmental sustainability of municipal wastewater treatment through struvite precipitation: Influence of operational parameters

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