Mineral Weathering and Metal Leaching under Meteoric Conditions in F-(Ba-Pb-Zn) Mining Waste of Hammam Zriba (NE Tunisia)

Abstract

Mining waste is an obvious source of environmental pollution due to the presence of heavy metals, which can contaminate soils, water resources, sediments, air, and people living nearby. The F-(Ba-Pb-Zn) deposit of Hammam Zriba located in northeast Tunisia, 8 km southeast of Zaghouan was intensively exploited from 1970 to 1992. More than 250,000 m3 of flotation tailings were produced and stored in the open air in three dumps without any measure of environmental protection. Thus, in this paper, mineralogical and chemical characterization, especially the sulfide and carbonate phases, were carried out to evaluate the potential for acid mining drainage (AMD) and metal leaching (ML). Conventional analytical methods (XRD, XRF, SEM) have revealed that this mining waste contains on average 34.8% barite–celestine series, 26.6% calcite, 23% quartz, 6.3% anglesite, 4.8% fluorite, 2.1% pyrite, and 0.4% sphalerite. The content of sulfides is less important. The tailing leaching tests (AFNOR NFX 31-210 standard) did not generate acidic leachate (pH: 8.3). The acidity produced by sulfide oxidation was neutralized by calcite present in abundance. Furthermore, the leaching tests yielded leachates with high concentrations of heavy metals, above the authorized thresholds. This high mobilization rate in potential toxic elements (PTE) represents a contamination risk for the environment.

The Development of Innovated Complex Process for Treatment of Old Flotation Tailings of Copper-Zinc Sulfide Ore

“…Sulfide ore processing is characterized by significant losses of non-ferrous and precious metals into various wastes, which in turn pose an environmental problem, but also can be considered a technogenic source of metals due to the decline in metal content in ores as well as deficiency of conventional ores [1][2][3][4][5][6][7][8][9][10].…”

“…Sulfide ore flotation tailings, especially those containing large amounts of pyrite as well as other sulfide minerals (containing different non-ferrous metals), are sources of acid mine drainage (AMD) due to the complex process of sulfide oxidation via biotic or abiotic processes induced by water and oxygen availability. Sulfide oxidation results in the formation of secondary minerals, such as sulfates (poitevinite, melanterite, gypsum), hydroxides (goethite), hydroxysulfates (jarosite, alunite), carbonates (malachite, azurite, smithsonite, siderite), and arsenates (scorodite) and release of metal cations and sulfates into the liquid phase [7,[9][10][11][12][13][14][15][16].…”