Characterization of Strength and Quality of Cemented Mine Backfill Made up of Lead-Zinc Processing Tailings

Predicting the reactions of the backfill materials exposed to the effects of air and groundwater will eventually ensure an efficient and accurate mine fill system for sustainable mining operations. This paper reveals the effect of the mobility of sulfur ions within lead-zinc processing tailings on strength and quality of cemented mine backfills. Some laboratory tests such as X-ray diffraction, ion chromatography, scanning electron microscopy, combustion tests, chemical analysis, pH and zeta potential measurements were performed to better characterize the backfill’s mechanical and microstructural properties. Moreover, CEM II/A-P Portland pozzolan and CEM IV/A pozzolanic cements as ready-to-use cement products were used for cemented mine backfill preparation. To ensure the carrier of the lead-zinc tailings and to prevent the mobility of the sulfurous components, a binder content ranging from 3 to 7 wt% were employed in mine backfills. The experimental findings demonstrate that the used cement type and proportions were insufficient and some fractures are occurred in the samples due to the sulfur ion mobility. Accordingly, one can state clearly that the elemental analysis through the combustion test method can provide fast and reliable results in the determination of sulfur within lead-zinc processing tailings.

Extraction of Non-ferrous Metals from Underspoil Waters

he focus of the study was the acidic underspoil waters of Safyanovskaya copper JSC containing 0.17 g/l of copper and 1.8 g/l of zinc (pH 2.8–2.9). The purpose of the work was research and development of water purification technology from impurities (copper, zinc, aluminum, iron, manganese), suggesting the possibility of copper and zinc extraction in the form of commercial products. The process of copper extraction by cementation with metallic iron was studied. It was shown that this method could allow to extract 94–95 % copper into a concentrate. The zinc extraction from solution after copper removal was studied by precipitation with NaHS, Na2CO3, NaOH and CaO. For economic reasons it is recommended to make zinc precipitation in two stages with CaO in order to produce cake containing 15–21 % Zn with extraction 80–87 %. This cake can be utilized at zinc processing plant. A process flowsheet for acidic underspoil waters, including copper cementation and the precipitation of zinc cake, has been developed. According to this scheme, mother liquor from zinc precipitation should be treated with lime until pH reaches 10–10.5, followed by pulp settling. As a result, purified water of the following composition is obtained, mg/l: zinc – 0.05, copper – 0.01, aluminum – 0.02, iron – 0.02, manganese – 0.05. Keywords: underspoil water, copper, zinc, iron, cementation, calcium oxide, concentrate, precipitation

Nutritive Value and Inherent Anti-Nutritive Factors in Processed Peanut (Arachis hypogaea)

Processing conditions and even the form of the food being processed as they affect nutrient availability is critical to develop structured foods to meet the nutritional needs of end users. The effect of heat treatments (roasting, boiling and autoclaving) on the physical, nutritional and functional properties of in-shell and shelled peanut (Arachishypogaea) was determined. Unprocessed shelled peanut served as the control. Nutrient and anti-nutrient compositions of peanut samples were determined by standard methods, while physical (colour) and functional properties were also carried out. Analysis of variance was used to analyze the treatment groups and Duncan's multiple range tests to determine significant difference at p≤0.05. The result of proximate composition revealed that raw peanut had protein (32.7%), ash (1.37%), fibre (5.15%), fat (42.9%) and carbohydrate (12.1%). However, processing methods significantly increased the fat and ash contents. Peanut is high in calcium, magnesium and potassium but low in iron and zinc; processing significantly increased the elemental concentration of peanut. Phytate, tannin, oxalate, alkaloid, trypsin inhibitor and flavonoid were determined in the peanut samples and all were significantly affected by the processing method employed. However, boiling of shelled peanut was more effective in reducing the anti-nutrients than roasting and autoclaving. The aflatoxin concentration was in a range of 2.06-8.05 ppb. Shelled peanuts subjected to the processing methods had lower aflatoxin levels compared with in-shell processed peanuts. There exist variation in bulk densities (packed and loosed), water and oil absorption capacities as a result of processing method employed. The colour of peanut was significantly affected by the processing method. In general, processing of shelled peanut resulted in flour with better nutritional quality and functionality than in-shell peanut. The findings showed that boiling has proved to be an efficient method in processing of peanut.

Geochemical barriers to elemental migration in sulfide-rich tailings: three case studies from Western Siberia

This study describes geochemical barriers that have developed at three different localities in sulfiderich tailings in the Kemerovo region of Western Siberia, Russia. Iron oxyhydroxides, gypsum, malachite, chalcanthite, goslarite, bianchite, gunningite and copper and zinc chlorides crystallized in the sequence specified at an evaporative barrier around glassy slag produced by the Belovo zinc processing plant. A complex cemented barrier that has developed within the old Salair sulfide tailings contains two well defined layers: an upper layer containing Fe(III) minerals and gypsum as cements in which Pb, As, Mo, Ni and Co have been deposited; and (2) a lower calcite- and gypsum-bearing layer, in which phases containing Zn, Cd and Cu have been deposited. A complex organic-mineral barrier below the Ursk sulfide tailings consists of peaty organic matter, clay minerals and iron oxyhydroxides cemented by gypsum. Elements that have leached from the tailings are present in this barrier in a variety of different forms: Ca and Mn are present as water-soluble species; Cu, Fe and Zn are present as species produced by interaction with organic matter via ion-exchange, metal humate formation and cation bridging in organic-mineral complexes; Pb and As are co-precipitated with and/or adsorbed onto iron oxyhydroxides; gold has been deposited as minute particles of native metal. The mechanisms for the formation of the different geochemical barriers are discussed.