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Papers by Francis Moyo

International Journal of Environmental Research, Oct 1, 2014

Ecotoxicity of rhodium (Rh) from the model of mining waste water side stream was examined in this... more Ecotoxicity of rhodium (Rh) from the model of mining waste water side stream was examined in this paper. Rh was extracted from the model of the mining waste water using an emulsion liquid membrane (ELM). The extractions were done at pH of 1.87 and pH 2.92 and 41.6 % and 46.2 % of Rh was extracted respectively. The side streams of pH of 1.87 and pH 2.92 after the extractions were examined for ecotoxicity using Daphnia pulex in the acute toxicity testing. All test organisms died after 48 hours of exposure to the side stream effluent with the original pH = 1.87, while 10-60 % survival rates were observed at the mining spent effluent with original pH of 2.92 if the strength of the effluent ranged from 12.5 to 62.5 %. Results for ethylenediaminetetraacetic acid tetrasodium salt dehydrate (EDTA) showed that an increase in concentration of EDTA in the test concentrations lead to the death of D. pulex. It was concluded that the very dilute water side streams are toxic hence the discharge of the spent Rh side-stream should thus be discouraged and prevented at all costs.

Liquid Waste Recovery, 2015

Journal of Bioremediation & Biodegradation, 2014

The current mini-review focuses on the use of liquid membranes in the platinum group metal (PGM/P... more The current mini-review focuses on the use of liquid membranes in the platinum group metal (PGM/PGMs) extraction from various types of wastewaters to prevent environmental pollution; and for the metal recovery to address the scarcity of the PGMs in the industrial cycles. The bulk liquid membranes have been used to the extracted PGMs from the (acidic) aqueous media with recoveries of up to 96.3 ± 2.5% of the original PGM amount. The extraction time generally ranges from 2 to 24 hours. The bulk membrane liquid in the PGM extraction will depend on the covalent structure of the extractant, the feed phase PGM concentration and the complex of the PGM in question that is actually extracted from the aqueous environment. The advantages of this type of liquid membrane include its operational simplicity, but the disadvantages include limited possibility to improve the extraction performance of the system. Literature data are encouraging as they indicate that extraction of PGMs from mining and metal-refinery side-streams does not suffer from interference from metal contaminants that are commonly found in the mining and metal refinery side-streams, e.g. iron. Thus further research should focus on the application of ELM to extraction of PGMs from said wastewaters and major research drive should focus on the use of the Taylorvortex column and the non-Newtonian ELMs. With the supported liquid membranes, 78-82% of the original PGM content could be recovered from model side-streams. The selectivity of the extraction for individual PGMs can be controlled by the extractant used.

Abstract: Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surf... more Abstract: Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of t...

International journal of environmental research and public health, Jan 9, 2014

Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and s... more Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of the concent...