Nanocrystalline ferrihydrite activated peroxymonosulfate for butyl-4-hydroxybenzoate oxidation: Performance and mechanism

Structure Evolution of Iron (Hydr)oxides under Nanoconfinement and Its Implication for Water Treatment

In the development of nanoenabled technologies for large-scale water treatment, immobilizing nanosized functional materials into the confined space of suitable substrates is one of the most effective strategies. However, the intrinsic effects of nanoconfinement on the decontamination performance of nanomaterials, particularly in terms of structural modulation, are rarely unveiled. Herein, we investigate the structure evolution and decontamination performance of iron (hydr)oxide nanoparticles, a widely used material for water treatment, when confined in track-etched (TE) membranes with channel sizes varying from 200 to 20 nm. Nanoconfinement drives phase transformation from ferrihydrite to goethite, rather than to hematite occurring in bulk systems, and the increase in the nanoconfinement degree from 200 to 20 nm leads to a significant drop in the fraction of the goethite phase within the aged products (from 41% to 0%). The nanoconfinement configuration is believed to greatly slow down the phase transformation kinetics, thereby preserving the specific adsorption of ferrihydrite toward As(V) even after 20-day aging at 343 K. This study unravels the structure evolution of confined iron hydroxide nanoparticles and provides new insights into the temporospatial effects of nanoconfinement on improving the water decontamination performance.

Exploration on the role of different iron species in the remediation of As and Cd co-contamination by sewage sludge biochar

Numerous studies have explored the adsorption of cadmium (Cd) and arsenic (As) by iron (Fe)-modified biochar, but few studies have examined in-depth the similarities and differences in the adsorption behavior of different iron types on Cd and As. In this study, sewage sludge biochar (BC) was co-pyrolyzed with self-made Fe minerals (magnetite, hematite, ferrihydrite, goethite, and schwertmannite) to treat Cd and As co-contaminated water. The adsorption of Cd and As on the Fe-modified biochar was further analyzed by adsorption kinetics, adsorption isotherms, and adsorption thermodynamics combined with a series of characterization experiments. Both SEM-EDX and XRD results confirmed the successful loading of iron minerals onto BC. Both adsorption kinetics and adsorption isotherms experiments showed that the adsorption of Cd and As by BC and the other five Fe-modified biochar was mainly controlled by chemical interactions. The results also indicated that goethite biochar (GtBC) was the most effective for the adsorption of Cd among the five Fe-modified biochar. Ferrihydrite biochar (FhBC) formed more diverse complexes, coupled with the relatively stronger electrons accepting ability, thus making it more effective for As adsorption than the others. Additionally, GtBC and hematite biochar (HmBC) were found effective for the adsorption of both Cd and As, whereas MBC was not found effective for either metal. Furthermore, combined with XPS results, the adsorption of Cd by the materials was mainly governed by Cd²⁺-π interactions, complexation precipitation, and co-precipitation, while oxidation reactions also existed for As.

Zero-Valent Copper-Mediated Peroxymonosulfate Activation for Efficient Degradation of Azo Dye Orange G

Zero-valent metal (ZVMs)-based persulfate activation systems are extensively applied for the elimination of organic pollutants in aqueous environments. In this study, for the first time, zero-valent copper (ZVC) was employed as the peroxymonosulfate (PMS) activator for the efficient degradation of Orange G (OG). The physicochemical properties of ZVC were systematically characterized by FESEM, EDX, TEM, XRD and XPS measurements. Furthermore, the effects of catalyst loading, PMS dosage, OG concentration and inorganic anions on the ZVC/PMS system were, respectively, investigated and explicated. The formation of •OH and SO4•− in the system was verified by quenching experiments and then the possible reaction mechanism was proposed. This work can provide insight into water treatment technology based on ZVMs.