Dual-functional heterogeneous Fenton catalyst Cu/Ti co-doped Fe3O4@FeOOH for cyanide-containing wastewater treatment: Preparation, performance and mechanism.

The dual-functional heterogeneous Fenton catalyst Cu/Ti co-doped iron-based Fenton catalyst (Cu/Ti -Fe3O4@FeOOH, FCT) were successfully prepared by precipitation oxidation method and characterized by XRD, XPS and XAFS. The prepared Cu/Ti co-doped Fe3O4@FeOOH nanoparticles consisted of goethite nanorods and magnetite rod octahedral particles, with Cu and Ti replacing Fe in the catalyst crystal structure, leading to the formation of the goethite structure. The heterogeneous Fenton catalyst FCT exhibited excellent degradation activity for cyanide in wastewater and showed different reaction mechanisms at varying pH levels. When treating 100 mL of 12 mg L-1 NaCN solution, complete degradation occurred within 40 min at 30 °C and pH ranging from 6.5 to 12.5 without external energy. Compared to Fe3O4, FCT shows superior degradation activity for cyanide. The surface Cu(Ⅰ) facilitated the electron transfer and significantly improved the catalytic activity of the catalyst. Additionally, the magnetic properties of the Ti-doped catalyst samples were greatly enhanced compared to the Cu@FeOOH catalyst doped with Cu, making them favorable for recycling and reuse. FCT maintains 100% degradation of cyanogen after three cycles, indicating its excellent stability. Furthermore, electron spin resonance spectroscopy, free radical quenching experiments and fluorescence probe techniques using terephthalic acid (TA) and benzoic acid (BA) confirmed that the presence of •OH and FeⅣ=O reactive species was responsible for the catalysts exhibiting different mechanisms at different pH conditions. Compared with other heterogeneous Fenton catalysts, FCT exhibits intentional degradation activity for cyanide-containing wastewater under different acid-base conditions, which greatly broadened the pH range of the heterogeneous Fenton reaction.

Efficient extraction performance and mechanisms of Cd2+ and Pb2+ in water by novel dicationic ionic liquids.

Ten novel hydrophobic dicationic ionic liquids (DILs) were synthesized and applied for the extraction of heavy metals in aqueous solutions. Their physicochemical properties were measured at ambient temperature, and the leaching behaviors of the as-prepared DILs in water were assessed by TOC analysis. Metal extraction experiments were carried out to evaluate the extraction performances of the DILs. It was found that the extraction rates of up to 0.45 and 0.53 mg·(g·min)-1 were achieved with 100 mg DILs for 5 mL of 5 mg/L Cd2+ and Pb2+ solutions. Besides, the extraction efficiencies of Cd2+ and Pb2+ were respectively up to 95.48% and 98.46%, when the volumes of the simulated wastewater were expanded by a factor of 20 at a constant extraction phase ratio (1000 mg DILs for 50 mL of 5 mg/L Cd2+ or Pb2+ solutions). The reusability of the novel DILs was successfully proved by the back-extraction experiments with 0.5 M HNO3. Finally, taking Cd2+ extraction as an example, the extraction mechanism based on FTIR analysis and quantum chemical calculations showed that both S and O atoms in the anions of DILs had physical and quasi-chemical interactions with Cd2+, which were stronger than the electrostatic attraction.