Reusable iron magnetic catalyst for organic pollutant removal by Adsorption, Fenton and Photo Fenton process

Synergistic effect of Fenton oxidation and adsorption process in treatment of azo printing dye: DSD optimization and reaction mechanism interpretation

The main challenges to overcome within the Fenton process are the acidic pH as an optimal reaction condition, sludge formation in neutral pH medium and high toxicity of treated printing wastewater due to the generation of contaminating by-products. This research discusses the catalytic activity of homogeneous (FeSO4/H2O2) and heterogeneous (Fe2(MoO4)3/H2O2) Fenton processes in treatment of Yellow azo printing dye in synthetic aqueous solution and real printing effluent, with an integration of adsorption on functionalized biochar synthesized from wild plum kernels. The definitive screening design (DSD), was used to design the experiment. Independent variables were initial dye concentration (20-180 mg L-1), iron concentration (0.75-60 mg L-1), pH (2-10) and hydrogen peroxide concentration (1-11 mM). Higher decolourization efficiency of 79% was obtained within homogeneous Fenton treatment of printing wastewater, in comparison to heterogeneous Fenton treatment (54%), after a reaction time of 60 min. Same trend of mineralization degree was established: COD removal was 59% and 33% for homogeneous and heterogeneous Fenton process, respectively. The application of adsorption treatment has achieved significant advantages in terms of toxicity reduction (95%) and decolourization efficiency (90% of TOC removal and 22% of dye removal) of treated samples, even at neutral pH medium. Degradation mechanisms within Fenton and adsorption processes were proposed based on the qualitative gas chromatography/mass spectrometry analysis, physico-chemical properties of dye degradation products and functionalized biochar. Overall, the homogeneous Fenton/adsorption combined process can be potentially used as a treatment to remove azo dyes from contaminated water.

Applying bottom ash as an alternative Fenton catalyst for effective removal of phenol from aqueous environment

In this study, coal bottom ash from a thermoelectric plant was tested as an alternative Fenton catalyst for phenol degradation in water. The effect of operating parameters such as initial pH, catalyst dosage and H2O2 concentration were evaluated. The characterization results indicated that the material has a mesoporous structure, with active species (Fe) well distributed on its surface. Under the optimal reaction conditions (6 mM H2O2, 1 g L-1 of catalyst and pH = 3), 98.7% phenol degradation efficiency was achieved in 60 min, as well as 71.6% TOC removal after 150 min. Hydroxyl radical was identified as the main oxidizing agent involved on the cleavage of the phenol molecule. After four consecutive reuse cycles, phenol degradation efficiency was around 80%, indicating good reusability and stability of the catalyst. Therefore, the obtained results demonstrated that the bottom ash presents remarkable activity for application in the Fenton reaction towards phenol degradation.

Effect of Pharmaceutical Sludge Pre-Treatment with Fenton/Fenton-like Reagents on Toxicity and Anaerobic Digestion Efficiency

Sewage sludge is successfully used in anaerobic digestion (AD). Although AD is a well-known, universal and widely recognized technology, there are factors that limit its widespread use, such as the presence of substances that are resistant to biodegradation, inhibit the fermentation process or are toxic to anaerobic microorganisms. Sewage sludge generated by the pharmaceutical sector is one such substance. Pharmaceutical sewage sludge (PSS) is characterized by high concentrations of biocides, including antibiotics and other compounds that have a negative effect on the anaerobic environment. The aim of the present research was to determine the feasibility of applying Advanced Oxidation Processes (AOP) harnessing Fenton's (Fe²⁺/H₂O₂) and Fenton-like (Fe³⁺/H₂O₂) reaction to PSS pre-treatment prior to AD. The method was analyzed in terms of its impact on limiting PSS toxicity and improving methane fermentation. The use of AOP led to a significant reduction of PSS toxicity from 53.3 ± 5.1% to 35.7 ± 3.2%, which had a direct impact on the taxonomic structure of anaerobic bacteria, and thus influenced biogas production efficiency and methane content. Correlations were found between PSS toxicity and the presence of Archaea and biogas yields in the Fe²⁺/H₂O₂ group. CH₄ production ranged from 363.2 ± 11.9 cm³ CH₄/g VS in the control PSS to approximately 450 cm³/g VS. This was 445.7 ± 21.6 cm³ CH₄/g VS (1.5 g Fe²⁺/dm³ and 6.0 g H₂O₂/dm³) and 453.6 ± 22.4 cm³ CH₄/g VS (2.0 g Fe²⁺/dm³ and 8.0 g H₂O₂/dm³). The differences between these variants were not statistically significant. Therefore, due to the economical use of chemical reagents, the optimal tested dose was 1.5 g Fe²⁺/6.0 g H₂O₂. The use of a Fenton-like reagent (Fe³⁺/H₂O₂) resulted in lower AD efficiency (max. 393.7 ± 12.1 cm³ CH₄/g VS), and no strong linear relationships between the analyzed variables were found. It is, therefore, a more difficult method to estimate the final effects. Research has proven that AOP can be used to improve the efficiency of AD of PSS.

Magnetic Zinc Oxide/Manganese Ferrite Composite for Photodegradation of the Antibiotic Rifampicin

In this study, a composite of zinc oxide and manganese ferrite was synthesized using co-precipitation and hydrothermal routes, to be used as photocatalysts in reactions with UV/Vis light source. The synthesized materials were characterized by FTIR, XRD, and SEM, where it was possible to verify the efficiency of the syntheses performed, through the identification of the resulting phases, the evaluation of the structural morphology of the particles, and the analysis of the detachments of the main vibration bonds present in these materials. The composite ZnO/MnFe₂O₄ was used in photodegradation reactions of the antibiotic rifampicin, with catalyst dosage of 0.20; 0.40, and 0.60 g and 10 ppm of rifampicin, reactions using pure ZnO as a catalyst were also performed as a comparative parameter of the influence of MnFe₂O₄ in this system. The composite ZnO/MnFe₂O₄ showed a maximum percentage of rifampicin decontamination of 94.72% and ZnO, 74.20%using 0.20 g of photocatalyst after 90 min, which indicates a positive influence on this process. The solution treated with ZnO/MnFe₂O₄ was subjected to magnetic field induction for attraction and consequently accelerated removal of the solids present, successfully, compacting for the application of ZnO/MnFe₂O₄ to be presented as a promising material for decontamination of emerging pollutants through photocatalytic reactions.

Resource Utilization of Acid Mine Drainage (AMD): A Review

Acid mine drainage (AMD) is a typical type of pollution originating from complex oxidation interactions that occur under ambient conditions in abandoned and active mines. AMD has high acidity and contains a high concentration of heavy metals and metalloids, posing a serious threat to ecological systems and human health. Over the years, great progress has been made in the prevention and treatment of AMD. Remediation approaches like chemical neutralization precipitation, ion exchange, membrane separation processes, and bioremediation have been extensively reported. Nevertheless, some limitations, such as low efficacy, excessive consumption of chemical reagents, and secondary contamination restrict the application of these technologies. The aim of this review was to provide updated information on the sustainable treatments that have been engaged in the published literature on the resource utilization of AMD. The recovery and reuse of valuable resources (e.g., clean water, sulfuric acid, and metal ions) from AMD can offset the cost of AMD remediation. Iron oxide particles recovered from AMD can be applied as adsorbents for the removal of pollutants from wastewater and for the fabrication of effective catalysts for heterogeneous Fenton reactions. The application of AMD in beneficiation fields, such as activating pyrite and chalcopyrite flotation, regulating pulp pH, and leaching copper-bearing waste rock, provides easy access to the innovative utilization of AMD. A review such as this will help researchers understand the progress in research, and identify the strengths and weaknesses of each treatment technology, which can help shape the direction of future research in this area.