Removal of fluconazole from aqueous solution by magnetic biochar treated by ball milling: adsorption performance and mechanism.

The problem of low adsorption capacity of pristine magnetic biochar for organic pollutants always occurs. It is of great significance to select a suitable method to improve the adsorption performance of magnetic biochar. In this study, magnetic biochar was treated by ball milling and tested for its fluconazole adsorption capacity. The maximum adsorption capacity of ball-milled magnetic biochar (BMBC) for fluconazole reached nearly 15.90 mg/g, which was approximately five times higher than that of pristine magnetic biochar (MBC). Fluconazole adsorption by BMBC was mainly attributed to π-π interactions, hydrogen bonding, and surface complexation with oxygen-containing functional groups. The enhancement in fluconazole adsorption by BMBC was attributed to an increase in oxygen-containing functional groups. Batch adsorption experiments also illustrated that BMBC could be successfully applied in a wide range of pH values. The high efficiency of fluconazole removal confirmed that ball milling was an effective strategy to enhance the adsorptive performance of magnetic biochar.

Iron-nitrogen co-doped carbon nanotubes decorated with Cu2O possess enhanced electronic properties for effective peroxymonosulfate activation.

Exploiting the full potential of copper-based nanoparticles in the activation of peroxymonopersulfate (PMS) is a great challenge due to their insufficient dispersity and electronic properties. We report here a novel iron­nitrogen co-doped carbon nanotube (FNC) modified with a Cu2O nanocomposite (Cu2O/FNC) that exhibits ultrahigh catalytic performance in the activation of PMS to degrade fluconazole (~95%). Catalytic performance evaluation illustrated that Cu2O/FNC also has wide pH applicability (3.0-11.0), long-term stability and excellent adaptability. In addition, luminescent bacteria toxicity tests confirm that Cu2O/FNC/PMS significantly reduced the acute biotoxicity of various recalcitrant pollutants (reduced by 45-83%). By identifying the reactive oxygen species (ROS) and catalytic performance for various pollutants, we propose that pollutants that interact weekly with activators are mostly destroyed by sulfate radicals and hydroxyl radicals, whilst both radical and non-radical routes were involved in the degradation of pollutants that were easily adsorbed. By modifying Cu2O with FNC, several crucial properties such as the specific surface area, surface defects, active sites and the charge transfer rate were significantly improved, leading to excellent catalytic performance for pollutant removal. Finally, a reasonable reaction mechanism is advanced for the fluconazole degradation pathway. This study not only develops a novel PMS oxidation system for fluconazole degradation, but also provides a new strategy to improve the reactivity and applicability of PMS activators by combining radical and non-radical activation pathways.

Effective degradation of tetracycline by magnetic palygorskite synthesized with different dosages of NaOH.

In the process of preparing magnetic palygorskite from waste pickling liquor of the steel industry, the dosage of NaOH will affect the properties of the magnetic palygorskite. The experimental results showed that magnetic palygorskite can be effectively prepared when NaOH dosage is between 255 and 330 g/L. Vibration sample magnetometry proved that different NaOH dosages can affect the saturation magnetization of magnetic palygorskite. The catalytic performance of five catalysts synthesized with different NaOH dosages hardly changed after five cycles of Fenton-like catalytic degradation of tetracycline (TC). The magnetic palygorskite prepared by this method had good catalytic performance even when the catalyst preparation conditions were magnified ten times, which can provide a reference for large-scale preparation of magnetic palygorskite.

Critical role of oxygen vacancies in heterogeneous Fenton oxidation over ceria-based catalysts.

This study examined the relationship between surface oxygen vacancies (OVs) and ceria-based heterogeneous Fenton catalytic activity. Compared with pure iron oxide and ceria, iron-doped ceria with abundant OVs (FeCeOx) exhibits higher rhodamine B (RhB) degradation efficiency (98%) and has a wider applicable pH range (3.0-9.0). The surface hydroxyl radicals are proved to be the predominant reactive species in the oxidation of RhB. Annealing the FeCeOx in an oxygen atmosphere appears to eliminate the OVs, significantly inhibiting the decomposition of H2O2 and the degradation of target pollutants. As multifunctional active sites, OVs are energetically more favorable for the adsorption of reactants than other sites, due to their high electron density. They not only accelerate the Fe(III)/Fe(II) cycle, they also immediately activate H2O2, dissolved oxygen or even water molecules to produce oxidative species, which accounts for the ideal degradation of RhB in the heterogeneous Fenton system. This study clarifies the mechanism of the ceria-based heterogeneous Fenton and provides a better understanding of the surface design of heterogeneous Fenton catalysts.

In situ remediation of hexavalent chromium contaminated soil by CMC-stabilized nanoscale zero-valent iron composited with biochar.

In this study, the remediation experiments were performed outdoors in natural conditions. Carboxymethyl cellulose (CMC)-stabilized nanoscale zero-valent iron (CMC-nZVI), biochar (BC) and CMC-stabilized nanoscale zero-valent iron composited with biochar (CMC-nZVI/BC) were synthesized and investigated for their effect on the in situ remediation of hexavalent chromium [Cr(VI)] contaminated soil and the concentration of available iron was tested after the remediation, compared with the untreated soil. The results of toxicity characteristic leaching procedure (TCLP) test showed that CMC-nZVI and CMC-nZVI/BC used as remediation materials could obviously improve the remediation rate of Cr contaminated soil and when the ratio of CMC-nZVI to Fe0 was 2.5 g/Kg, the leachability of Cr(VI) and Crtotal can be reduced by 100% and 95.8% simultaneously. Moreover, sequential extraction procedure (SEP) showed that most exchangeable Cr converted to carbonate-bound and Fe-Mn oxides-bound, reducing the availability and leachability of Cr in the soil.