Steel Scale Waste as a Heterogeneous Fenton-like Catalyst for the Treatment of Landfill Leachate

Coactivation of Hydrogen Peroxide Using Pyrogenic Carbon and Magnetite for Sustainable Oxidation of Organic Pollutants

Pyrogenic carbon and magnetite (Fe3O4) were mixed together for the activation of hydrogen peroxide (H2O2), aiming to enhance the oxidation of refractory pollutants in a sustainable way. The experimental results indicated that the straw-derived carbon obtained by pyrolysis at 500-800 °C was efficient on coactivation of H2O2, and the most efficient one was that prepared at 700 °C (C700) featured with abundant defects. Specifically, the reaction rate constant (kobs) for removal of an antibiotic ciprofloxacin in the coactivation system (C700/Fe3O4/H2O2) is 12.5 times that in the magnetite-catalyzed system (Fe3O4/H2O2). The faster pollutant oxidation is attributed to the sustainable production of •OH in the coactivation process, in which the carbon facilitated decomposition of H2O2 and regeneration of Fe(II). Besides the enhanced H2O2 utilization in the coactivation process, the leaching of iron was controlled within the concentration limit in drinking water (0.3 mg·L-1) set by the World Health Organization.

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.

Valorisation of residual iron dust as Fenton catalyst for pulp and paper wastewater treatment

In this work, the performance of residual iron dust (RID) from metallurgic industry was assessed as Fenton catalyst for the treatment of real pulp bleaching wastewater. The focus was on the removal of recalcitrant pollutants AOX (adsorbable organic halides), by a novel, cleaner, and cost-effective circular solution based on a waste-derived catalyst. The behaviour of RID as iron source was firstly assessed by performing leaching tests at different RID:wastewater w/v ratios and contact time. Afterwards, RID-catalysed homogeneous and heterogeneous Fenton processes were conducted to maximise AOX removal from the pulp bleaching wastewater. Reusability of RID was assessed by a simple collect-and-reuse methodology, without any modification. Similar AOX removal under less consumption of chemicals was achieved with the novel heterogeneous Fenton process. Reaction in the bulk solution was the main pathway of AOX removal, given that the low surface area and porosity of the material did not allow for a high contribution of surface reaction to the overall performance. Moreover, AOX removal was similar over two consecutive treatment cycles, with Fenton process being responsible for 56.7-62.1% removal of AOX from the wastewater, and the leaching step adding 11.4-13.2%. At the end of treatment, COD either decreased (1^st cycle) or remained unchanged (2^nd and 3^rd cycle). The operating cost of the optimised heterogeneous Fenton was 3-11% lower than under conventional Fenton process. This work presented a novel, circular solution based on a low-cost waste-derived catalyst, advancing the knowledge needed to foster industrial application of such technologies to increase industrial environmental performance and efficiency.