The aim of this work was to investigate the removal of a heavy metal from aqueous solutions using a natural adsorbent, with the prospect of its future application in wastewater treatment. Batch adsorption experiments were carried out in a closed reactor at room temperature (23 ± 2 °C) under continuous stirring at 160 rpm using raw pozzolan as an adsorbent for Pb(II) removal. The influence of experimental parameters, including contact time, solution pH, adsorbent dosage, and initial Pb(II) concentration, on the adsorption performance was systematically considered. The obtained results showed that the maximum Pb(II) removal efficiency reached 99% under the optimum conditions of 70 min equilibrium time, pH 4, adsorbent dosage of 0.1 g, and an initial Pb(II) concentration of 1 mg·L–1. The equilibrium data were analyzed using several adsorption isotherms models, namely Freundlich, Langmuir, Dubinin–Radushkevich, and Temkin. The results indicated that the adsorption process was best described by the Freundlich and Langmuir models, with a maximum monolayer adsorption capacity of 137 mg·g–1. Furthermore, the kinetic study revealed that the adsorption process followed the pseudo-second-order kinetic model, with correlation coefficients close to unity. Overall, the findings demonstrate that natural pozzolan is an economical and eco-friendly adsorbent with high potential for the effective removal of lead from wastewater.
This study investigates the kinetics of polyester fabric dyeing with a disperse dye in a betaine-based deep eutectic solvent (DES). The dyeing process was monitored by measuring the decrease in dye concentration in the dye bath over time under varying initial dye concentrations (200–1000 mg/dm3) and dyeing times (10–60 min). The adsorption behavior was analyzed using Jovanović, Harkin–Jura, and Temkin isotherm models. The results indicate that dye uptake increases with dyeing time, while the degree of exhaustion decreases with increasing initial dye concentration. Among the applied models, the Harkin–Jura model showed the best fit (R² = 0.99), suggesting multilayer adsorption on a heterogeneous surface. The Jovanović model also showed a high correlation (R² = 0.98), indicating possible monolayer contributions. SEM analysis confirmed no morphological changes, while TGA confirmed the thermal stability of the dyed fabric, without any degradation behavior occurring.
This paper briefly summarizes the vast experimental and theoretical material resulted from the detailed multi-annual studies of the condition, composition and evolution of the natural water bodies, with special focus on water pollution and self-purification through the chemical reduction-oxidation processes with the involvement of oxygen, hydrogen peroxide and transition metal ions and complexes, performed at the Faculty of Chemistry and Chemical Technology of Moldova State University. The role and different pathways of hydrogen peroxide formation in natural waters and subsequent H2O2 decomposition, free radicals’ generation and oxygen activation are discussed, along with the detailed mechanisms of pollutants’ transformations with the involvement of series of active species and catalysts.
The first thio-debranone strigolactone mimic containing a hetaryl moiety was obtained by S-alkylation of 2-mercaptobenzothiazole with 5-bromo-3-methylfuran-2(5H)-one in the presence of potassium carbonate. The structure of the S-alkylation product was deduced by NMR spectroscopy and confirmed by X-ray analysis.
Apple pomace is an agro-industrial by-product known to be rich in phenolic compounds. Instead of being discarded, it could be capitalized into novel food ingredients and products. The aim of this study was to evaluate the optimal processing order in a sequential two-step eco-friendly extraction consisting of one hydroalcoholic (ethanolic) step and one enzymatic step. The highest content of phenolic compounds, as measured by TPC, TFC, and THA was obtained in the case of the order – hydroalcoholic extraction (HE) followed by the enzymatic extraction (EE). High positive correlations were observed between the phenolic content and the antioxidant activity, especially THA with FRAP, and negative correlations with most polyphenol-normalized AOA. The proposed method for recovery of antioxidant compounds from apple pomace stands out as a green, environmentally friendly method for valorization of this agro-industrial by-product and each step can be further optimized in order to maximize the content of polyphenols. The generalizability of the results for other apple cultivars and economic feasibility will have to be established in future studies.
