The effectivness of UV/H2O2 process, Fenton and photo-Fenton process at decolorization of commercially important textile dyes Reactive Orange 4 (RO4) and Reactive Blue 19 (RB19) was evaluated. The effect of operational condition such as initial pH, initial H2O2 concentration, initial Fe2+ concentration and initial dye concentration on decolorization of RO4 and RB19 was studied. The photo-Fenton process is found to be more efficient than UV/H2O2 and Fenton process for decolorization of simulated dye bath effluent and solutions of the dyes in water alone under optimum conditions. In simulated dye bath the removal efficiency was slightly lower than for the solutions of the dyes in water alone for both dyes types. The results revealed that the tested advanced oxidation processes were very effective for decolorization of RO4 and RB19 in aqueous solution.

Bismuth basic nitrates (BBNs) were synthesized via an electrochemical method, i.e., by electrodeposition from an acidic solution of bismuth nitrate, followed by thermal treatment in an air environment. For the first time, the influence of various electrochemical parameters on the morphology, crystal structure, and chemical structure of BBNs was examined. The following synthesis parameters were investigated: electrodeposition current density, thermal treatment temperature of the obtained deposit, and working electrode material (cathode). The obtained materials were characterized by SEM-EDX, XRD, FTIR, TG, and N₂ adsorption/desorption methods and were applied for the sorption of the textile dye RB19. The results showed that the electrodeposition current density and thermal treatment temperature affect the surface morphology, chemical composition, and crystal structure of the obtained materials, as well as the RB19 sorption efficiency. On the other hand, the working electrode material does not affect the properties of the synthesized materials mentioned. Kinetic, isotherm, and thermodynamic analysis of the sorption process were also examined.

Treatment of textile wastewater using heterogeneous photocatalysis began in the the last decade and attracted the attention of researchers due to its versatile application. The variety of applications of TiO₂ as a photocatalyst was due toits numerous positive properties, such as low operating temperature, biologically inert nature, low energy consumption, water insolubility, availability and photoactivity, low toxicity, high chemical stability, suitable flat band potential, narrow bandgap and the fact that it is environmentally benign. Heterogeneous UV-TiO₂ photocatalysis is capable of removing organic pollutants from textile wastewater; this has been widely studied, with the technology also having been commercialized in many developing countries. Decolorization of anthraquinone dye Reactive Blue 19 (RB 19) by heterogeneous advanced oxidation processes TiO₂/UV/H₂O₂, TiO₂/UV/KBrO₃ and TiO₂/UV/(NH₄)₂S₂O₈ was studied under different conditions and in the presence of electron acceptors such as hydrogen peroxide (H₂O₂), potassium bromate (KBrO₃) and ammonium persulphate ((NH₄)₂S₂O₈). Decolorization was very fast for all three processes, and complete dye decolorization was achieved in 10 min. The effect of various ions (Cl^–, SO₄^2– and HCO₃^–) on RB 19 decolorization was also studied. The optimal condition for the decolorization of the dye were determined to be: TiO₂ concentration 1 g∙dm^–3, electron acceptor concentration 30.0 mmol∙dm^–3, dye concentration 50.0 mg∙dm^–3, UV intensity 1 950 μW∙cm^–2, at temperature 25 ± 0.5°C. In addition, experiments were performed and compared in three different matrices. In the surface water and dyebath effluent water, the removal efficiency for RB 19 was lower than that achieved in the deionized water because of the interference of complex constituents in the surface water and effluent. LC-MS analysis was carried out and the detected intermediates were compared with the previously published data for anthraquinone dyes.

A new woodchips-ZrO₂ biosorbent (W-ZrO₂) was synthesized using wood residue material generated from the oak tree (Quercus robur) during furniture manufacturing. Biosorbent was tested for the simultaneous removal of both chromium (Cr) ions: Cr(III) and Cr(VI), in the binary component solution. Biosorbent characterization was performed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). To define optimal process parameters for simultaneous removal of both Cr species, effects of pH, temperature, sorbent dosage and Cr ions concentration on the sorption process were investigated. Sorption of Cr ions onto W-ZrO₂ was highly pH-dependent. Optimal pH for simultaneous removal of both Cr(III) and Cr(VI) ions is 4.0 with removal efficiency over 99.5 % in both cases. Equilibrium experimental results are the best fitted by the Langmuir sorption isotherm model. The maximal sorption capacities of the biosorbent for simultaneous removal of Cr(III) and Cr(VI) ions in binary-component system are 16.18 and 83.52 mg g⁻¹, respectively. The present study shows that using wood residue material to produce a low-cost sorbent can effectively decrease the water pollution simultaneously removing both chromium species from water and also reduce wood waste and increase reuse/recycling options.

Extensive utilization of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has resulted in contamination of the aquatic environment; this situation requires effective treatment technology. Ultraviolet-based advanced oxidation processes (UV-AOPs) are widely employed for the removal of organic contaminants from water. This study’s aim was to compare the degradation of the pesticide 2,4-D in UV-C-activated peroxide and peroxydisulfate systems. UV-C irradiation alone exhibited a negligible effect on pesticide degradation, whereas the addition of oxidants significantly enhanced the degradation efficiency relative to 2,4-D. Complete pesticide removal was achieved after 15 min of UV/H₂O₂ treatment, while twice as much time was required with the UV/S₂O₈²⁻ process. COD decreased by 74% and 28% for UV-C-activated peroxide and peroxydisulfate, respectively. Both investigated systems demonstrated good performance for 2,4-D dechlorination. Pesticide degradation rates increased with increasing dosages of the applied oxidants. Acidic conditions were more favorable for degradation of 2,4-D, compared to neutral and basic conditions, for both systems studied. The degradation efficiency relative to 2,4-D decreased in the presence of HA, Cl⁻ and HCO₃⁻ in water matrices. The predominant radical for the UV-C-activated peroxydisulfate was determined to be a sulfate radical. These findings are of fundamental and practical significance in understanding UV-C-activated 2,4-D degradation, paving the way for the selection of preferred processes for the optimal removal of pesticides from various aqueous matrices.