Abstract
Pyrite-rich cyanide tailings (CTs) are industrial hazardous solid wastes arising from the gold mining industry. Every year, hundreds of millions of tons of cyanide tailings are produced and discharged to tailings dams. It is of great significance to dispose of cyanide tailings harmlessly and resourcefully. The feasibility of calcination of calcium sulphoaluminate (CSA) cement clinker using pyrite-rich cyanide tailings as Fe2O3 and SO3 sources was investigated for this paper. The behavior of pyrite during the calcination of cyanide tailings under various calcination conditions and the properties of calcium sulphoaluminate cement clinker were examined. The results show that it is feasible to produce calcium sulphoaluminate cement clinker using pyrite-rich cyanide tailings. The optimal conditions for the calcination of calcium sulphoaluminate cement using pyrite-rich cyanide tailings are confirmed. During the calcination process, the cyanides decompose into carbonate, CO2, and N2. The pyrite decomposes into Fe2O3 and SO2, and they react with CaO and Al2O3 to form the intermediates of CaSO4, 2CaO·Fe2O3, and CaO·2Al2O3, which further react to form 3CaO·3Al2O3·CaSO4, 4CaO·Al2O3·Fe2O3, and 12CaO·7Al2O3. The calcium sulphoaluminate cement prepared by pyrite-rich cyanide tailings exhibits excellent mechanical properties and meets the compressive strength criteria of 42.5 grade calcium sulphoaluminate cement.
Highlights
Calcium sulphoaluminate (CSA) cement was essentially developed in China in the 1970s [1,2]
55.91% CaO, whereas that of alumina mainly consists of 94.60% Al2 O3 and 5.09% loss on ignition (LOI)
55.91% CaO, whereas that of alumina mainly consists of 94.60% Al2O3 and 5.09% loss on ignition (LOI)
Summary
Calcium sulphoaluminate (CSA) cement was essentially developed in China in the 1970s [1,2] It is usually produced by limestone, clay, and bauxite in addition to natural gypsum at 1250–1350 ◦ C, about. CSA cement is considered as a sustainable and eco-friendly alternative to OPC due to the lower energy consumption and fewer CO2 emissions during the production [6]. This cement is widely used in architecture engineering, emergency maintenance, permeability resistance engineering, cement manufacturing, and other fields owing to its low alkalinity, rapid hardening, high early-age strength, high impermeability, chemical resistance/freeze–thaw corrosion, and low shrinkage [5,7]. In recent years, increasing attention has been paid to the recycling of industrial by-products such as fly ash [9,10], gypsum [4,11], slag [12], and other solid wastes [13,14] for CSA production
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