Slobodan Najdanović

Electrochemical oxidation is an effective method for degrading environmentally harmful textile dyes that are difficult to remove by conventional treatments. The novel graphite–Co₃O₄ anode, prepared by electrochemically modifying recycled graphite tubes for AAS samples and characterized by SEM, EDX, FTIR, XRD, and BET, was used for electrochemical degradation of RB 4 dye in model solutions and textile dyeing effluent. Modification did not disrupt the graphite crystal structure but altered its surface properties, improving its dye degradation performance. It increased the decolorization rate constant of a model solution from 0.0148 min⁻¹ to 0.0753 min⁻¹ and maximum COD decay from 59% to 91%, reducing decolorization energy consumption from 3.26 kWh m⁻³ to 0.89 kWh m⁻³. Degradation at the graphite–Co₃O₄ anode proceeded via ·OH radicals and most likely the Co³⁺/Co²⁺ redox couple. It followed the pseudo-first-order kinetics. Pastel- and dark-shade dyeing textile effluents (containing 53 mg dm⁻³ and 159 mg dm⁻³ RB 4, respectively) were decolorized in about 70 and 110 min; COD decay reached about 87% and 80% after 180 min of electrolysis, respectively. The corresponding energy consumption was 1.75 kWh m⁻³, 2.39 kWh m⁻³, 2.97 kWh m⁻³, and 2.91 kWh m⁻³, respectively. The anode was efficient and stable in the given working conditions.

Threatening environmental resources such as water, air and soil, and thus indirectly threatening biodiversity, through rapid, uncontrolled and non-ecological industrial production systems must be prevented through appropriate purification methods. In this research, the sorption of Reactive blue 19 anthraquinone dye from aqueous solution was carried out in a batch system using nano zinc–manganese ferrite carbonate (ZnMn–Fe₂O₄–CO₃) synthesized by the co-precipitation method. Various factors affecting the sorption activity of the material were examined, and the most suitable conditions were determined to be pH 2 and ZnMn–Fe₂O₄–CO₃ concentration of 0.25 g/L, whereby an equilibrium sorption capacity of 1463.10 mg/g was achieved. The ZnMn–Fe₂O₄–CO₃ removal efficiency was found to be 88.48% in effluent from a textile manufacturing industry. Utilizing FTIR, SEM, EDS, XRD, TGA and BET methods, the material’s morphological and structural characteristics were thoroughly investigated and reported. Regarding the kinetic and isotherm models that were analyzed, the Langmuir and pseudo-second-order (PSO) models provided the best fit to the aforementioned sorption system. Thermodynamic data confirmed the spontaneity of the sorption reaction and the exothermic nature of the process. An extensive study of ZnMn–Fe₂O₄–CO₃ demonstrated its high efficiency in removing RB19 dye, as well as the safety and simplicity of the synthesis, the cost-effectiveness of the sorption process, and the possibility of regeneration and reuse over multiple cycles. These findings highlight the potential of ZnMn–Fe₂O₄–CO₃ for advanced water and wastewater purification technologies targeting anthraquinone dyes.

This study examines the potential degradation of the anthraquinone textile dye Reactive Blue 19 (RB 19) and the azo dye Reactive Orange 16 (RO 16) through the application of thermally activated peroxydisulfate. The influence of basic operating parameters, such as the initial pH value of the solution, initial peroxydisulfate concentration, and temperature, was investigated. The degradation reaction followed pseudo-first-order kinetics for both dyes under investigated conditions. The degradation rate constants for these dyes increased with a rise in the concentration of peroxydisulfate up to a certain threshold, as well as with an increase in temperature, and in an acidic environment. The findings offer significant insights into the implementation of advanced oxidation processes utilizing thermally activated persulfate for the remediation of textile dye contaminated wastewater.

A self-made pulsating atmospheric-pressure corona plasma reactor was tested for the degradation of textile dye Reactive Blue 4. The reactor generated a corona-type discharge in air with low-intensity streamers, without sparks. The effect of the initial dye concentration, input reactor voltage, and pH was examined using model dye water solutions. A 50 mg dm-3 dye solution was completely decolorized at 18 kV and its native pH of 6.8 in less than 40 minutes. The chemical oxygen demand (COD) was reduced by 82% and 85% after 120 and 180 minutes of treatment, respectively. Decolorization rate and efficiency decreased with increasing initial dye concentration and with decreasing input voltage. Decolorization proceeded slightly faster in acid-neutral media than in alkaline media. The major degrading agent was determined to be the hydroxyl radical, generated by plasma. Textile effluent, containing 56 mg dm-3 RB 4, sulphates and carbonates, with pH 11.8, after removing the dyed fabric, was completely decolorized in 85 minutes, and the COD was reduced by about 76% and 78% after 120 and 180 minutes of treatment, respectively, which demonstrated the high potential of the reactor.

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.

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.

The removal of Reactive Blue 19 (RB19) by Layered double hydroxide (NiFe-LDH) was investigated. The study examined the influence of various sorption parameters, including contact time, initial concentration, and pH. Adsorption isotherm data under optimal conditions indicated that the adsorption of RB19 by NiFe-LDH followed the Langmuir monolayer adsorption model. The sorption capacity of NiFe-LDH was found 414.03 mg g-1 at an optimal pH of 3.

The bismuth basic nitrate (BBN) was synthesized by precipitation method from bismuth nitrate as precursor. Precipitation was done at pH 3.5 at room temperature. Characterization was done by Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray diffraction (XRD) methods. Morphologically the BBN consisted of plane-like structures with nanometric particles on their surface. Results of XRD analysis show that bismuth basic nitrate with chemical formula Bi6O5(OH)3(NO3)5 ⋅ 3H2O crystallizes in the monoclinic space group P21/c (14) with a = 17.15200, b = 9.18100, c = 17.75200, β = 127.830 and V = 2207.94. The obtained material showed a certain adsorption activity for textile dye Reactive Blue 19 (RB19), and a very high photocatalytic activity for the same dye. Photocatalytic decolorization of RB19 was achieved in 15 minutes. The findings clearly demonstrated the applicability of BBN for the photocatalytic decolorization of RB19.

ZnO was synthesized by potentiostatic electrodeposition, characterize by XRD, SEM and EDX, and used as a catalyst for degradation of Reactive Blue 19 (RB 19) dye by non-thermal atmospheric pressure corona plasma discharge. The principle of degradation and the role of the catalyst were presented. ZnO improved the degradation rate by 2.35 times by enhancing decomposition of plasma-generated H2O2 into ⋅OH radical, which was found to be a major degradation reagent.