The removal of Rhodamine B by H2O2 or ClO2 combined with hydrodynamic cavitation

Degradation of methyl orange using hydrodynamic Cavitation, H2O2, and photo-catalysis with TiO2-Coated glass Fibers: Key operating parameters and synergistic effects

Advanced oxidation processes (AOPs) are eco-friendly, and promising technology for treating dye containing wastewater. This study focuses on investigating the removal of methyl orange (MO), an azo dye, from a synthetic wastewater through the use of hydrodynamic cavitation (HC), both independently and in combination with hydrogen peroxide (H2O2), as an external oxidant, as well as photocatalysis (PC) employing catalyst coated on glass fibers tissue (GFT). The examination of various operating parameters, including the pressure drop and the concentration of H2O2, was systematically conducted to optimize the degradation of MO. A per-pass degradation modelwas used to interpret and describe the experimental data. The data revealed that exclusive employment of HC using a vortex-based cavitation device at 1.5 bar pressure drop, resulted in a degradation exceeding 96 % after 100 passes, equivalent to 230 min of treatment (cavitation yield of 3.6 mg/kJ for HC), with a COD mineralization surpassing 12 %. The presence of a small amount of H2O2 (0.01 %) significantly reduced the degradation time from 230 min to 36 min (16 passes), achieving a degradation of 99.8 % (cavitation yield of 6.77 mg/kJ for HC) with COD mineralization rate twice as much as HC alone, indicating a synergistic effect of 4.8. The degradation time was further reduced to 21 min by combining HC with PC using TiO2-coated glass fibers and H2O2, (cavitation yield of 11.83 mg/kJ for HC), resulting in an impressive synergistic effect of 9.2 and COD mineralization twice as high as the HC/H2O2 system. The results demonstrate that HC based hybrid AOPs can be very effective for treating and mineralizing azo dyes in water.

A novel method for the remediation of wastewater containing acid red 131 dye using acoustic cavitation combined with sulphur-doped TiO2 and oxidants

The present study investigated the degradation of Acid Red 131 (AR131) dye using a combination of ultrasound-induced cavitation, ultraviolet (UV) irradiation, chemical oxidants, and photocatalyst, focusing on the effect of operating parameters. It was established that acidic pH, higher input power, and lower initial concentration resulted in higher degradation. Sulphur-doped titanium dioxide (S-TiO2) synthesized using a novel ultrasound-assisted method showed an optimum dosage of 300 ppm for the AR131 degradation with sulphur to titanium ratio of 2:1. In the combination approach, the optimum dosage of hydrogen peroxide (H2O2) and potassium persulfate (KPS) was established as 100 ppm and 400 ppm respectively. The maximum degradation of 90.3% was obtained using a combined approach of US + KPS + UV/S-TiO2 whereas, a maximum synergetic coefficient of 1.57 was obtained for the approach of US + UV/S-TiO2 with degradation of 86.96%. It was also elucidated that for combination approaches of US + H2O2, US + H2O2 + KPS, and US + H2O2 + KPS + UV/S-TiO2, the synergetic coefficients were lower than one due to undesirable side reactions and radical scavenging. Scale-up studies performed at 15 times of the laboratory scale volume, elucidated that the maximum degradation was obtained as 58.01% for the approach of US + KPS + UV/S-TiO2. Therefore, the approach of US + KPS + UV/S-TiO2 was elucidated as the most efficient in degrading the AR131 dye at both small and large scale of operation. In terms of synergy, the approach of US + UV/S-TiO2 was more efficient. Overall, an optimized combination approach was successfully demonstrated for the effective degradation of AR131 dye with synergism and better results at a large scale.

Nanocomposite of graphene oxide decorated Al-waste sludge for removal of rhodamine B from water

The contamination of land and water resources is reaching its breaking point due to increased human activities. This research attempts to provide a smart solution based on the concept of waste to treat waste, in which solid waste from the aluminium anodizing industry is upcycled and used with graphene oxide to engineer a composite material to treat dye contaminated water. Here, highly porous upcycled aluminium waste sludge is combined with less than 1% (w/w) of graphene oxide and then thermally treated to partially reduce the graphene oxide within the nano matrix. Partial reduction enhances π-π interaction with dye molecules while preserving the hydrophilicity and porosity of the overall composite. Studies carried out with rhodamine B, a toxic dye with intense colour, show complete and efficient removal of the dye from water, independent of any pH adjustment. Moreover, the adsorbed material shows no leachate of the dye nor heavy metals back into water over a wide range of pH values. This facilitates alternative product developments such as building materials and eliminates secondary waste generation. Therefore, the composite described herein is sustainable in both material development and in its usage for wastewater treatment and solid waste management.

Rapid Degradation of Chlortetracycline Using Hydrodynamic Cavitation with Hydrogen Peroxide

Chlortetracycline (CTC), which has been frequently detected in surface water, is generated primarily by the discharge of high-concentration CTC wastewater from pharmaceutical and livestock plants. The development of effective CTC degradation technology is critical. In this study, the extent of CTC degradation at 80 mg/L was investigated by combining hydrodynamic cavitation (HC) and hydrogen peroxide (H₂O₂). The results indicate degradation ratios of 88.7% and 93.8% at 5 and 30 min, respectively. Furthermore, the possible mechanisms of CTC degradation were determined via HPLC-MS. The CTC degradation pathways include ring openings, C–N bond cleavage, demethylation, dehydroxylation, and desaturation in the sole system of HC, and a series of additional reactions, such as glycine conjugation and the cleavage of C–C double bonds, occurs in the binary system of HC + H₂O₂. Nevertheless, the treated water poses ecological risks and cannot be directly discharged into the environment. Therefore, HC + H₂O₂ treatment may be a rapid and effective primary method for the degradation of high-concentration CTC in pharmaceutical factories.