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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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Abstract-Platinum and palladium were adsorbed onto grape stalk and activated grape stalk prepared by chemical activation process using phosphoric acid. The amount of platinum and palladium uptake (adsorbent loading) was quantified. Influence of contact time, pH were investigated. The results showed that the adsorption of metal ions is pH dependent. The presence of base metal ions in the solution did not affect the process of adsorption of palladium and platinum. Effect of temperature was taken into account during the determination of isotherms. Langmuir and Freundlich isotherm models were applied and compared.

In this pilot study, the circular economy concept in wastewater treatment was examined, through a zero liquid discharge (ZLD) process where struvite was recovered and drinking water was reclaimed. A stage wise approach was used for struvite formation and the subsequent reclamation of drinking water. Specifically, the early stages of treatment entail the synthesis of struvite via the chemical precipitation of nutrients (phosphate and ammonia), using thermally activated cryptocrystalline magnesite. Thence, reverse osmosis (RO) was employed for drinking water reclamation. With this dual approach, 3.5 m 3 of municipal wastewater were successfully treated at a pilot plant in South Africa, producing ~52.5 kg of struvite and ~3.4 m 3 of drinking water. The operating parameters were 30 min of residence time, 0.5 g : 500 mL solid to liquid (S/L) ratio, using ambient temperature and pH. X-ray diffraction (XRD) and High Resolution Scanning Electron Microscopy (HR-SEM) coupled with electron dispersion spectroscopy (EDS) confirmed the synthesis of struvite and the presence of notable Mg/P ratios. Fourier Transform Infrared Spectrometer (FTIR) further ascertained the obtained results. Moreover, it was identified that the reclaimed water meets the South African National Standard (SANS) 241 and the world health organisation (WHO) standards for drinking water. An economic analysis revealed the viability of the process, suggesting that the system could be self-sustainable. Therefore, the results of this work indicate that introducing the concept of circular economy in wastewater treatment can promote the sustainable management of the ever-increasing quantities of municipal wastewater and at the same time address problems of emerging concern, such as water scarcity and phosphate shortage.

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Computational models have been developed and solved by the use of a computer coded software Python on Spyder console. The models were developed to gain an improved insight of carbon dioxide capture process performance by concentrating on the volume flowrate of the flue gas. The models were based on chemical absorption method. The study was aimed at exploring the absorption capacity of monoethanolamine (MEA), chilled ammonia and potassium carbonate (K2CO3) systems by concentrating on the movement of flue gas volume. The profiling of volume was prepared in order to see how much of the flue gas will be lost at the end of absorption when the three mentioned absorbent are used to capture carbon dioxide (CO2). The results showed that high volume flow of the gaseous phase has led to poor absorption, whilst low volume flow yields higher CO2 absorption. Moreover, in comparison to K2CO3 and chilled ammonia, the MEA was found to have the best absorption capacity.