Experimental Research Of Mining And Metallurgical Waste Residues As Water Pollution Amendments

Effective removal of organic pollutants, nutrients and metals and neutralisation of acidity in industrial, agricultural and domestic wastewater is pivotal to water re-use. Utilisation of abundant, low-cost mining and metallurgical waste residue materials potentially offers a cost-effective wastewater treatment option. Steel and iron-, titanium-, and aluminium-based mining and metallurgical waste residues were selected for this research, including:magnetite ore processing residue (MPR); Ti-containing blast furnace slag (TiBFS); blast furnace slag (BFS); steel slag (SS); magnetite-containing TiO2 processing residue (TiPR) and red sand (RS).The physical, chemical, and mineralogical characteristics of these mining and metallurgical waste residues were characterised. Physico-chemical characterization of these mineral-based waste residues showed that the materials were largely dominated by Fe, Al, Mn-oxides/(oxy)hydroxides and calcium-and/or magnesium-based minerals. The identified mineral phases indicated that the selected waste residues may have capacity for attenuation of contaminants in wastewater via adsorption, precipitation, redox reactions, ion-exchange, physical sequestration, structural incorporation, crystal formation or other mechanisms. Adsorption, precipitation, redox reactions, and ion-exchange processes are likely the most important attenuation mechanisms.A series of column sorption experiments were conducted to examine the removal of dissolved organic carbon (DOC), soluble reactive phosphorus (phosphate, PO4-P), ammonia (NH3-N), nitrate/nitrite (NOx-N), dissolved organic nitrogen (DON) and total nitrogen (TN) from surface water using the selected steel and iron-, titanium-and aluminium-based mining and metallurgical waste residues. Bassendean Sand, comprised of>98% SiO2, was selected for use as a reference material and comprised the nominally unreactive solid phase in all experimental columns. These column experiments demonstrated that steel slag and magnetite ore processing residue exhibited good attenuation of DOC and nutrients, especially phosphorus. Other selected mining and metallurgical waste residues exhibited good attenuation of phosphorus and some attenuation of DOC and nitrogen.A second series of column sorption experiments were conducted to examine the attenuation of Cd2+, Co2+, Cu2+, Mn2+, Ni2+ and Zn2+ and the neutralisation of acidity in synthetic acid drainage water using the selected steel and iron-, titanium-and aluminium-based mining and metallurgical waste residues. Bassendean Sand was again selected for use as a reference material and comprised the nominally unreactive solid phase in all expeirmental columns. These column experiments demonstrated that the selected mineral-based mining and metallurgical waste residues have substantial capacity for attenuation of metals and acid neutralisation. The steel slag, red mud, and Ti-containing blast furnace slag exhibited the best attenuation of metals. The blast furnace slag, steel slag and magnetite ore processing residue exhibited the best acid neutralisation.Geochemical modelling was undertaken to estimate the saturation index (SI) of a suite of mineral phases, in particular, relevant Al, Fe, Mn, Ca, and Mg minerals. Minerals comprised of these elements were modelled as it is likely that they will strongly influence the speciation of the majority of other major and trace elements in the column experiments or in a permeable reactive barrier application. Geochemical modelling using PHREEQC yielded information about the dissolution of mineral-based waste residues and the precipitation or in situ formation of secondary minerals in experimental columns during pollutant removal. This information provided a basis for understanding geochemical changes in the practical application. The potential dominating minerals influencing the pollutant removing are also derived in every selected mining and metallurgical waste residues column.This research demonstrated that the of Fe, Al, and Mn oxide/(oxy)hydroxide and calcium and magnesium content strongly influenced pollutant removal ability of steel and iron-, titanium-, and aluminium-based mining and metallurgical waste residues. The steel slag, which had high contents of both Fe, Al, and Mn oxide/(oxy) hydroxide and calcium-and magnesium-based minerals, exhibited the best pollutant removal ability. Steel and iron-, titanium-and aluminium-based mining and metallurgical waste residues exhibited potential for application in the treatment of wastewater. The mineral-based by-products examined in this study may be effective for the attenuation of nutrients and DOC in surface water, ground water, or other urban and agricultural water sources; the prevention of pollutant diffusion from dumps and sewers; or treatment of acidic, metal-rich industrial or mining wastewater. The use of mining and metallurgical waste residues in environmental remediation is largely influenced by the design of treatment structures. Mineral-based waste residues such as those examined in this report may be particularly useful as treatment media in constructed wetlands, drain liners, permeable reactive barriers or similar applications.