The removal of methyl orange using coal fly ash, which is a widely available low-cost adsorbent, has been investigated. Adsorption studies for dye removal were conducted using various configurations such as batch, column and heap adsorption at various temperatures and adsorbent dosages at neutral pH. The Langmuir, Freundlich and Tempkin isotherm models were used to describe the process. The Freundlich model best represented the adsorption. Kinetic studies show the adsorption followed pseudo-second-order kinetics. Thermodynamic studies show that the process is spontaneous, endothermic and random. Column configuration was found to be the most efficient with a dye removal percentage of 99.95%, followed by heap adsorption at 99.25% removal and lastly batch configuration with 96.68% removal. Economic analysis shows that column operation would be the most effective for practical implementation.

Refractory sulphidic ore with gold captured in pyrite has motivated researchers to find efficient means to break down pyrite to make gold accessible and, ultimately, improve gold extraction. Thus, the dissolution of pyrite was investigated to understand the mechanism and find the corresponding kinetics in a nitric acid solution. To carry this out, the temperature (25 to 85 °C), nitric acid concentration (1 to 4 M), the particle size of pyrite from 53 to 212 µm, and different stirring speeds were examined to observe their effect on pyrite dissolution. An increase in temperature and nitric acid concentration were influential parameters to obtaining a substantial improvement in pyrite dissolution (95% Fe extraction achieved). The new shrinking core equation (1/3ln (1 − X) + [(1 − X)^−1/3 − 1)]) = kt) fit the measured rates of dissolution well. Thus, the mixed–controlled kinetics model describing the interfacial transfer and diffusion governed the reaction kinetics of pyrite. The activation energies (E_a) were 145.2 kJ/mol at 25–45 °C and 44.3 kJ/mol at higher temperatures (55–85 °C). A semiempirical expression describing the reaction of pyrite dissolution under the conditions studied was proposed: 1/3ln(1 − X) + [(1 − X)^−1/3 − 1)] = 88.3 [HNO₃]^2.6 r₀^−1.3 e^−44280/RT t. The solid residue was analysed using SEM, XRD, and Raman spectrometry, which all identified sulphur formation as the pyrite dissolved. Interestingly, two sulphur species, i.e., S₈ and S₆, formed during the dissolution process, which were detected using XRD Rietveld refinement.

The syntheses, characterization and experimental solid state X-ray structures of five low-spin paramagnetic 2-pyridyl-(1,2,3)-triazole-copper compounds, [Cu(Lⁿ)₂Cl₂], are presented in this study, for the following five Lⁿ ligands: L¹ = 2-(1-(p-tolyl)-1H-(1,2,3-triazol-4-yl)pyridine), L² = 2-(1-(4-chlorophenyl)-1H-(1,2,3-triazol-4-yl)pyridine), L³ = 4-(4-(pyridin-2-yl)-1H-(1,2,3-triazol-4-yl)benzonitril), L⁴ = 2-(1-phenyl-1H-(1,2,3-triazol-4-yl)pyridine) and L⁵ = 2-(1-(4-(trifluoromethyl)phenyl)-1H-(1,2,3-triazol-4-yl)pyridine). These five [Cu(Lⁿ)₂Cl₂] complexes each contain two bidentate 2-pyridyl-(1,2,3)-triazole (Lⁿ) and two chloride ions as ligands, with the Cu–N(pyridine) bonds, Cu–N(triazole) and Cu–Cl bonds trans to each other. All five [Cu(Lⁿ)₂Cl₂] compounds display elongation Jahn–Teller distortion, either along opposite Cu–N(triazole) bonds, or along opposite Cu–Cl bonds, as indicated by their obtained solid state crystal structures. Quantum chemistry calculations, using density functional theory, indicated however that elongation Jahn–Teller distortion is in fact possible along any two opposite bonds in these octahedral compounds with the elongation distortion along the opposite Cu–N(triazole) bonds being the most stable structure.