Pd/MIL-100(Fe) as hydrogen activator for FeIII/FeII cycle: Fenton removal of sulfamethazine.

Masses of iron sludge generated from engineering practice of classic Fenton reaction constraints its further promotion. Accelerating the FeIII/FeII cycle may be conducive to reducing the initial ferrous slat dosage and the final iron sludge. Based on the reduction of Pd/MIL-100(Fe)-activated hydrogen, an improved Fenton system named MHACF-MIL-100(Fe) was developed at ambient temperature and pressure. 97.8% of sulfamethazine, the target pollutant in this work, could be degraded in 5 min under the conditions of 20 mM H2O2, 25 µM ferrous chloride, initial pH 3.0, 2 g·L-1 composite catalyst Pd/MIL-100(Fe) and hydrogen gas 60 mL·min-1. Combining density functional theory (DFT) calculation and intermediate detection, the degradation of this antibiotic was inferred to start from the cleavage of N-S bond. The catalytic of Pd/MIL-100(Fe), demonstrated by the removal efficiency of SMT and the catalyst morphology, remained intact after six reaction cycles. The present study provides an insight into the promotion of Fenton reaction.

Destruction of 4-chlorophenol by the hydrogen-accelerated catalytic Fenton system enhanced by Pd/NH2-MIL-101(Cr).

4-chlorophenol (4-CP) could be rapidly mineralized by using Fenton reaction. However, massive iron sludge will be generated because of the excessive consumption of iron salt and poor recycling of FeIII back to FeII. In this paper, by introducing hydrogen gas and solid catalyst Pd/NH2-MIL-101(Cr) to classic Fenton reactor, the novel system named MHACF-NH2-MIL-101(Cr) was constructed. Much less FeII was needed in this system because the hydrogen could significantly accelerate the regeneration of FeII. The catalyst improved the utilization of H2. The degradation reaction of 4-CP could be driven by using only trace amount of FeII. It could be rapidly degraded by the hydroxyl radical detected by the 4-Hydroxy-benzoicacid which is the oxidative product of benzoic acid and hydroxyl radical. The effects of dosage of ferrous salt, H2O2 and catalyst, H2 flow, Pd content, and initial pH of and concentration of 4-CP aqueous solution were investigated. The robustness and morphology changes of this catalytic material were also systematically analysed. By clarifying the role of this solid MOFs material in this hydrogen-mediated Fenton reaction system, it will provide a new direction for the research and development of advanced oxidation processes with high efficiency and low sludge generation in future.