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This article will focus on the alkaline leaching of gold-bearing tetrahedrite concentrate in a solution containing sodium sulfide and sodium hydroxide. This selective leaching is followed by the leaching of heavy and waste metals into the solution, which may influence the physical properties and quality of the desired product, possibly causing environmental toxicity. At the same time, the amount of gold was observed during the leaching process to increase its content in the solid phase for the possibility of recovery and subsequent extraction of the precious metal. Sodium sulfide works very effectively on sulfide minerals which include tetrahedrite, and sodium hydroxide eliminates the hydrolysis of sulfur which slows leaching. The leaching kinetics were carried out with a duration of five hours, and based on volume sampling at certain time intervals from three samples, with the characteristic NaOH concentration, the leaching efficiency was observed from the results with atomic absorption spectrometry. The solid residue containing the tetrahedrite concentrate was analyzed through X-ray photoelectron analysis spectrometry, from which the % solids content was determined, and it is also known to deduce the leached amount of metals for each sample.

Geopolymers can improve environmental protection and are therefore considered a 21st-century material that requires special attention. The main objective of this study was to examine the utilization of fly ash deposited on a heap as a potential raw material for the geopolymerization process. In this work, flexural and compressive strengths, as well as water absorption of geopolymers, were evaluated based on alkaline activator properties. Na2O content, SiO2/Na2O molar ratio and fly ash-to-water ratio were key observed factors. Mechanical strengths tests were conducted after 7, 28, 90, 180, and 360 days. The research findings showed that geopolymer cured at appropriate conditions and with a suitable alkaline activator can reach a compressive strength of more than 55 MPa. The presented study highlighted the possibility of the efficient use of fly ash to produce useful materials, i.e., geopolymers, which contribute to environmentally friendly solutions. This approach is fully in line with the principles of sustainable development.