Novel magnetic catalysts for organic pollutant degradation via contact electro-catalysis

Abstract

Contact-electro-catalysis (CEC) has been proposed as an efficient mechanism for organic pollutant degradation. However, the effects of chemical and physical properties of catalysts on the CEC efficiency have not been reported so far. Importantly, solving the secondary pollution caused by micro-nano catalysts due to the difficulty of recycling and inability to degrade is another bottleneck for achieving the commercial application of CEC. In this work, we synthesized a micro-nano catalyst with tunable chemical groups on the surface based on magnetic nanoparticles for the degradation of methyl orange (MO) via CEC. With the increase of the electronegativity of the chemical groups (R-F>R-CH3 >R-NH2), the degradation efficiency of MO also be improved obviously. The low surface energy of hydrophobic particles leads to the existence of a threshold (e.g., 20 mg R-F per 50 ml MO solution) for the exposed total surface area of the catalyst in aqueous solution, which is the main reason for the nonlinear increase of catalyst mass and CEC efficiency. Previously reported toxic non-degradable fluoride catalysts (e.g., FEP, PTFE) can be effectively replaced by catalysts R-CH3. Using the R-CH3 in CEC, the degradation efficiency of MO reaches 99% within 2 h. The micro-nano R-CH3 catalyst can be recycled by nearly 100% through the magnetic separator, and the catalytic efficiency can reach more than 97% after ten cycles of CEC. We expect this attractive catalyst to be a promising candidate for applications in large-scale organic pollutant degradation systems although more work on system parameter optimization needs to be further addressed.