An optimal laboratory two-step procedure was developed for sodium/potassium O-alkyl carbonodithioate (sodium/potassium alkyl xanthates) production in the form of aqueous solutions. Sodium isopropyl xanthate (Na-iPrX), as the most effective salt in a real ore flotation process, was also produced at an industrial level and introduced as a collector for copper ores. In order to reduce toxicity of the flotation process and improve sustainability by minimising environmental impacts, collector efficiency and selectivity in the flotation process were studied in relation to possible synergism of xanthates combined with the derived biomass and biodegradable green reagents levulinic acid, 5-hydroxymethyl-2-furanacrylic acid (HMFA), and condensation product of hydroxymethylfurfural and levulinic acid. Optimal content of 30% of HMFA in the collector pointed to the possibility of substitution of commercial xanthate collector without significantly affecting its efficiency/selectivity. The density functional theory (DFT) calculations provided insights into the interaction mechanism of Na-iPrX and HMFA with cooper. The benefits of the presented method highlight production simplicity, mild reaction conditions, high purity and yield of products, no by-products, and technological applicability on an industrial scale.

The removal of the As(V) and Iprodione fungicide onto EGS@APTES-GT, obtained by amino-modified expanded glass spheres (EGS) modified with goethite, was studied in this work. Material characterization was performed using SEM/EDS, XRD, and FTIR techniques. The adsorption capacities of 51.01 and 94.28 mg g⁻¹, for As(V) and Iprodione removal at 25 °C, respectively, were achieved. A kinetic study indicated lower intraparticle diffusional transport resistance. Physisorption is the dominant mechanism for Iprodione removal, while surface complexation is for As(V). The disposal of effluent water after five adsorption–desorption cycles was attained through Iprodione photocatalytic degradation and arsenate precipitation. Exhausted EGS@APTES-GT, processed by goethite acidic dissolution and grinding, was used as a reinforcing filler in composites production based on commercial unsaturated polyester resin (UPe). An improvement in the mechanical properties was observed, with a gradual increase in the tensile strength, reaching a maximum of 25.9% for UPe with 10 wt.% of ground exhausted adsorbent compared to pure UPe. The overarching concept is defined by the aspiration to develop technologies that address all output flows of advanced processes. Thus, the combination of wastewater treatment technologies and the production of potentially marketable composites successfully achieved both a low environmental impact and the implementation of a circular economy.

The increase in waste polymer recycling has helped in promoting sustainability, and together with the use of renewable raw materials, it has become a widespread concept with positive effects on both the economy and ecology. Accordingly, the aim of this study was the synthesis of “green” plasticizers, marked as LA/PG/PET/EG/LA, formed from waste poly(ethylene terephthalate) (PET) and bio-based platform chemicals propylene glycol (PG) and levulinic acid (LA). The structure of the obtained plasticizers was complex, as confirmed by results from nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR) analysis. The LA/PG/PET/EG/LA plasticizers and waste poly(vinyl chloride) (PVC) were used in an optimized technology for PVC re-granulate production. The hardness of the PVC-based material with “green” plasticizers, in comparison to commercial plasticizer dioctyl terephthalate (DOTP), increased by 11.3%, while migration decreased. An improved material homogeneity and wettability of the fibers by the matrix were observed using SEM analysis of the material’s fracture surface, with a higher efficiency of intermolecular interactions leading to better mechanical performances of the newly designed materials. Thus, LA/PG/PET/EG/LA are unique materials with good compounding and plasticizing potential for PVC, as revealed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). In that manner, the use of bio-renewable resources and recycled polymers will contribute to diminishing waste polymer generation, contributing to a lower carbon footprint.

The specific objectives of the presented study were related to the optimization of the production process of N-alkyl-, N,N-dialkyl-, and N-cycloalkyl-O-isobutyl thiocarbamate; trial industrial production of N-ethyl-O-isobutyl thiocarbamate; and the evaluation of flotation efficiency of N-ethyl-O-isobutyl thiocarbamate using a real ore sample. The optimization of thiocarbamate syntheses were performed by varying the molar ratio of isobutyl alcohol, carbon disulfide, potassium hydroxide, reaction time, and reaction temperature. In the first step, one-pot reaction took place to produce alkyl xanthate and was followed with chlorination to give alkyl chloroformate (O-alkyl carbonochloridothioate); finally, thiocarbamates were obtained by the reaction with corresponding amines. N-alkyl-O-ethyl thiocarbamate was synthesized as a comparative flotation agent. The structure of the synthesized compounds was confirmed by IR, ¹H and ¹³C NMR, and MS instrumental methods, and the purity was determined by gas chromatographic method and elemental analysis. The optimized methods gave high-purity products in a significant yield that was also confirmed by semi-industrial production of N-ethyl-O-isobutyl thiocarbamate. The optimized thiocarbamate synthesis, without isolation of intermediates, is of great importance from the aspect of green technologies. Flotation efficiency test results, using real copper and zinc ores, showed the highest activity of N-ethyl-O-isobutyl thiocarbamate. The optimal one-pot thiocarbamate synthesis provides a simple procedure with a high conversion degree, and, thus, offers valuable technology applicable at the industrial scale.

Styrene-butadiene (SBR) and acrylonitrile-butadiene (NBR) rubber blends with tetramethyl thiuram disulfide (TMTD) and tetramethyl thiuram monosulfide (TMTS) accelerators and environmentally friendly plasticizers, obtained from PET recycling and biobased resources (LA/PG/PET/EG/LA), were prepared. The mechanical properties of the obtained rubber products were tested and compared with those of commercial dioctyl terephthalate (DOTP). TMTS was prepared by simple and efficient one-pot synthesis from dimethylamine, carbon disulfide, potassium cyanide, and ammonium chloride as catalysts in recycled isopropanol/water azeotrope as solvent. In a comparative study, methoxide, ethoxide, iodide, and amide ions were also used. The two-step reaction mechanism of TMTS synthesis involves the oxidation of the amine salt of dimethyldithiocarbamic acid to TMTD by hydrogen peroxide and sulfur elimination from the TMTD disulfide bond. Potassium cyanide appears to be the most efficient nucleophile. The simplicity of operation, mild reaction conditions, solvent recycling, high yields, and applicability to the industrial level are the advantages of this process. Shore hardness, tensile strength, and compression test results of vulcanized blends before and after aging showed similar properties for both accelerators, while somewhat better results were obtained with LA/PG/PET/EG/LA plasticizer.

Melanin-based biosorbents (MiCS), derived from chestnut shells, were encapsulated in sodium alginate to obtain MiCS@Alg, useful in a column adsorption study. MiCS contains various acidic surface groups able to participate in the removal of cationic pollutants from aqueous solutions. The MiCS and MiCS@Alg were characterized by Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Dynamic Light Scattering (DLS), while zeta potential and particle size analyses were performed to gain deeper insight into surface charge behavior. Batch adsorption experiments were carried out at three different temperatures, demonstrating that the adsorption kinetics followed a pseudo-second-order (PSO) model and that the Freundlich model best described the equilibrium data. The process was found to be endothermic and spontaneous, with maximum adsorption capacities of 300.2 mg g⁻¹ (BR2), 201.5 mg g⁻¹ (BY28) and 73.08 mg g⁻¹ (NH₃) on MiCS, and 189.3 mg g⁻¹ (BR2), 117.1 mg g⁻¹ (BY28) and 50.06 mg g⁻¹ (NH₃) on MiCS@Alg at 45 °C and compared with the unmodified chestnut shell. The MiCS and MiCS@Alg exhibited good adsorption performance, improved environmental compatibility, and greater reusability. Overall, these results highlight MiCS@Alg as a cost-effective, sustainable, and highly promising novel biosorbent for the removal of cationic pollutants (BR2, BY28, and NH₃) from water.