This study explores the enhanced photocatalytic performance of boron-doped zinc oxide (ZnO) nanoparticles synthesized via a scalable mechanochemical route. Utilizing X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), the structural and morphological properties of these nanoparticles were assessed. Specifically, nanoparticles with 1 wt%, 2.5 wt%, and 5 wt% boron doping were analyzed after calcination at temperatures of 500 °C, 600 °C, and 700 °C. The obtained results indicate that 1 wt% B-ZnO nanoparticles calcined at 700 °C show superior photocatalytic efficiency of 99.94% methyl orange degradation under UVA light—a significant improvement over undoped ZnO. Furthermore, the study introduces a predictive model using the artificial neural network (ANN) technique, developed in Python, which effectively forecasts photocatalytic performance based on experimental conditions with R² = 0.9810. This could further enhance wastewater treatment processes, such as heterogeneous photocatalysis, through ANN-guided optimization.

This paper is focused on cobalt valorization from the cathode material of spent lithium-ion batteries (LIBs) by using leaching and electrochemical deposition methods. During the leaching experiments, the degrees of cathode material dissolution in H2SO4-N2 and H2SO4-O2 systems were compared. Maximal degrees of cobalt extraction were 40 % in the former and 47 % in the latter system under following experimental conditions: H2SO4 concentration of 2 mol dm-3, nitrogen/oxygen volumetric flow of 2 L min-1, solid phase concentration of 33 g L-1, and temperature of 85?C. The rate of cobalt extraction from the cathode material in both investigated systems was the most favorable in the first 15 min, after which there was a sudden decrease in the reaction rate. Cobalt from the leaching solution was deposited on a copper substrate by galvanostatic electrochemical deposition with a current efficiency of 84 %. The energy consumption was 5.8 kWh kg-1 of deposited Co. The cyclic voltammetry (CV) method was used to determine the potential of cobalt deposition, as well as side reactions taking place in the system. Scanning electron microscopy with energy dispersive spectrometry has shown that during the process of electrochemical deposition agglomeration of cobalt particles occurred (in the shape of cauliflower), while the metal was deposited in its elemental state, which was also confirmed by the results of X-ray diffraction analysis.

In this study, the potential of the walnut shell as a biosorbent for biosorption of Cu(II), Pb(II), and As(III)/(V) ions from river water samples was investigated. The effects of various conditions of water samples such as the initial ion concentration, sample pH, and contact time at a constant temperature and biosorbent dosage, on biosorption of Cu(II), Pb(II), and As(III)/(V) were investigated. Walnut shells, as the material with a high potential for removal of investigated ions, have biosorption efficiency of up to 99.6%, under the applied experimental conditions. The best adsorption time was obtained at 4 h for Cu(II), Pb(II), and As(III)/(V) ions. The maximum removal of 97.6% (Cu(II)), 82.9% (Pb(II)), and 99.6% (As(III)/(V)) was obtained at pH=4.43, pH=8.55, and pH=7.84, respectively. Hence, the walnut shell shows potential of a cost-effective biosorbent that could be used for the treatment of contaminated rivers. However, further investigation is needed to fully explore this potential.

The recycling of spent lithium-ion batteries (LIBs) requires efficient and sustainable methods for recovering critical metals. In this study, the leaching behavior of LiCoO₂ cathode material obtained from spent LIBs was investigated in phosphoric acid, using copper powder recovered from waste LIBs as a reducing agent. Leaching experiments were conducted under various conditions (temperature, solid-to-liquid ratio, agitation rate) and compared with systems without copper. In the absence of copper, lithium and cobalt, recoveries after 30 min were approximately 77% and 23%, respectively. The addition of copper significantly enhanced leaching, achieving >96% recovery for both metals at 80 °C, with most extraction occurring within the first 30 min. Kinetic analysis using the shrinking core model indicated a mixed-control mechanism involving both surface chemical reaction and product layer diffusion. The calculated activation energies were 20.2 kJ·mol⁻¹ for lithium and 16.1 kJ·mol⁻¹ for cobalt. Solid residues were characterized by X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). XRD results revealed that the composition of the residues varied with leaching temperature: Co₃O₄ was consistently detected, whereas Cu₈(PO₃OH)₂(PO₄)₄·7H₂O appeared only when leaching was performed above 50 °C. Thermodynamic calculations supported the reductive role of copper and provided insight into possible reaction pathways. These findings confirm the effectiveness of copper-mediated leaching in phosphoric acid and demonstrate that temperature strongly influences residue phase evolution, thereby offering valuable guidance for the design of sustainable LIB recycling processes.

The aim of this study is to evaluate mullein (Verbascum thapsus) as a cost-effective and sustainable adsorbent for the biosorption of Pb(II) ions from synthetic wastewater samples. Biosorption of mullein was investigated as a function of initial Pb(II) concentration (25–400 mg L⁻¹), biosorbent dosage (2–20 g L⁻¹), solution pH (3–7), and contact time (10–120 min). Mullein as a material with a high affinity for Pb(II) ions had a biosorption efficiency of 98.56% under the optimal conditions: pH 6, initial concentration of Pb(II) at 100 mg L⁻¹, contact time of 90 min, and biosorbent dosage of 20 g L⁻¹. The FTIR spectra of mullein leaves showed that oxygen-containing functional groups on the surface are potentially active sites for the biosorption of Pb(II) ions. EDS analysis and the pH_PZC value confirmed the adsorption of Pb(II) ions at the active sites of the mullein. Kinetic and isotherm data enabled insights into the modes of Pb(II) biosorption on the mullein surface which were best explained with the pseudo-second-order kinetic model and the Freundlich adsorption isotherm. Biosorption occurs on the mullein surface via multilayer adsorption. The reusability of mullein showed that the native biosorbents can be reused five times, showing the economic and sustainable benefit of this low-cost biosorbent material.