Mine tailings from an abandoned metal mine in Korea contained high concentrations of arsenic (As) and heavy metals [e.g., As: 67,336, Fe: 137,180, Cu: 764, Pb: 3,572, and Zn: 12,420 (mg/kg)]. US EPA method 6010 was an effective method for analyzing total arsenic and heavy metals concentrations. Arsenic in the mine tailings showed a high residual fraction of 89% by a sequential extraction. In Toxicity Characteristic Leaching Procedure (TCLP) and Korean Standard Leaching Test (KSLT), leaching concentrations of arsenic and heavy metals were very low [e.g., As (mg/L): 0.4 for TCLP and 0.2 for KSLT; cf. As criteria (mg/L): 5.0 for TCLP and 1.5 for KSLT].

This research virus carried put to recycle the aggregates in the waste concrete. The recycled aggregates below 25 mm produced by the company I. a construction waste processing company were divided into several pans. According as the particle size was decreased, the amount of cement mortar, absorption ratio and abrasion ratio of recycled aggregate were increased. When they were heated at 200~500°C and ground by ball mill, the amount of cement mortar separated from the recycled aggregates was increased according to increase in temperature. When the aggregates such as granite and gneiss were heated above 550°C, their compressive strength was declined for α-SiO₂ contained in them was transformed into β-SiO₂. Thus, the waste concrete was heated at 400~500°C and ground by ball mill for 1 hr not to deteriorate the aggregate in concrete. As a result, the specific gravity, the absorption ratio, and the abrasion ratio of the aggregates become above 2.5, below 3.0%, and below 40%.

Inside the finest fractions of aggregates, usually wasted by ready mix concrete companies, valuable heavy minerals content is substantial. The concentration and recovery of valuable heavy minerals contained in dredged fine aggregates waste, located in Pyeongtaek South Korea, were investigated to develop a process that can recover and concentrate most of each heavy mineral. The raw material contains ilmenite, magnetite, monazite, and zircon. A gravity separation, recirculating the middlings recovered ilmenite, magnetite, monazite, and zircon with 44.05%, 36.90%, 53.76%, and 69.7% respectively. Nevertheless, a magnetic separation followed by gravity separation of the non-magnetic fraction further improved the recovery of ilmenite, magnetite, monazite, and zircon to 86.96%, 85.09%, 91.06%, and 90.82% respectively. This concentrate was separated at different magnetic intensities. Magnetite was concentrated at 0.05 T, resulting in a recovery of 23.4% and grade of 95.1 wt%. Ilmenite was at 0.4 T, with a recovery of 55.2% and grade of 84.2 wt%. Monazite was at 0.9 T, with a recovery of 59.3% and rare earth oxide content of 45.2%, the non-magnetic fraction has a high zircon content, the recovery was 70.6% and grade of 91.8 wt%.

This study was carried out to identify the conditions of formation of calcium sulphoaluminate (3CaO·3Al₂O₃·CaSO₄) by the sintering of a limestone (CaCO₃) and alunite [K₂SO₄·Al₂(SO₄)₃·4Al(OH)₃] mixture with the following reagents: K₂SO₄, CaCO₃, Al(OH)₃, CaSO₄·2H₂O, and SiO₂. When K₂SO₄, CaCO₃, Al(OH)₃, CaSO₄·2H₂O were mixed in molar ratios of 1:3:6:3 and sintered at 1,200~1,300 °C, only 3CaO·3Al₂O₃·CaSO₄ and calcium langbeinite (2CaSO₄·K₂SO₄) were generated. With an amount of CaO that is less than the stoichiometric molar ratio, 3CaO·3Al₂O₃·CaSO₄ was formed and anhydrite (CaSO₄) did not react and remained behind. With the amount of CaSO₄ that is less than the stoichiometric molar ratio, the amounts of 3CaO·3Al₂O₃·CaSO₄ and 2CaSO₄·K₂SO₄ decreased, and that of CaO·Al₂O₃ increased. In the K₂SO₄-CaO-Al₂O₃-CaSO₄-SiO₂ system, to stabilize the formation of 3CaO·3Al₂O₃·CaSO₄, 2CaSO₄·K₂SO₄, and β-2CaO·SiO₂, the molar ratios of CaO: Al₂O₃: CaSO₄ must be kept at 3:3:1 and that of CaO/SiO₂, over 2.0; otherwise, the generated amount of 3CaO·3Al₂O₃·CaSO₄ decreased and that of gehlenite (2CaO·Al₂O₃·SiO₂) with no hydration increased quantitatively. Therefore, if all SO₃(g) generated by the thermal decomposition of alunite reacts with CaCO₃ (or CaO, the thermal decomposition product of limestone) to form CaSO₄ in an alunite- limestone system, 1 mol of pure alunite reacts with 6 mol of limestone to form 1 mol of 3CaO·3Al₂O₃·CaSO₄ and 1 mol of 2CaSO₄·K₂SO₄.

Titanium's importance as a mineral resource is increasing, but the Korean industry depends on imports. Ilmenite is the principal titanium ore. However, research and development from raw materials have not been investigated yet in detail. Hence, measures to secure a stable titanium supply chain are urgently needed. Accordingly, through beneficiation technology, we evaluated the possibility of technological application for the efficient recovery of valuable minerals. As a result of the experiments, we confirmed that mineral particles existed as fine particles due to weathering, making recovery through classification difficult. Consequently, applying beneficiation technologies, i.e., specific gravity separation, magnetic separation, and flotation, makes it possible to recover valuable minerals such as hematite and rutile. However, there are limitations in