Efficient Generation Of Reactive Species Research Articles

Ascorbic acid enhanced CuFe2O4-catalyzed heterogeneous photo-Fenton-like degradation of phenol

CuFe2O4 particles were synthesized using the sol-gel self-combustion method and characterized for their compositional surface morphology and crystal structure. When compared to the photo-Fenton system without ascorbic acid (AA), the presence of AA significantly enhanced the catalytic degradation of phenol using CuFe2O4. The highest catalytic degradation efficiency was achieved at an AA concentration of 1 mmol/L, resulting in up to 98.6 % elimination of phenol in just 40 min. The reaction rate was found to be 31.7 times higher than that of the system without AA. The mechanism of AA enhancement in the CuFe2O4 photo-Fenton system was further investigated. Two key factors were found to contribute to the enhancing mechanism of AA introduction in the CuFe2O4 photo-Fenton system. Firstly, AA promoted the Cu/Fe redox cycle on the catalyst surface, leading to a more efficient generation of reactive species that are responsible for phenol degradation. Secondly, AA accelerated the leaching of metal ions from the catalyst surface, facilitating the homogenous Fenton effect. The Cu/Fe bimetallic cycle system offers new perspectives on effective Fenton catalyst design and provides crucial insights for reductant-enhanced photo-Fenton activation.

Intensified emission and afterglow burst in pulsed microwave plasma at atmospheric pressure

Dynamical properties of argon plasma jet at atmospheric pressure driven by microwave pulses with high repetition rate and fast rise time are investigated using time-resolved optical emission measurements in combination with fast imaging. Spectroscopic measurements reveal an emission burst at the pulse rise including electron continuum emission, hydroxyl molecular lines, and a large overshoot of argon atomic lines. The latter can be interpreted as a transient increase in electron temperature supported by a numerical simulation. At the pulse off, an afterglow burst of argon lines is observed with a time scale much faster than the conventional afterglow in low pressure discharges. The afterglow burst indicates dissociative recombination of argon dimer ions and generation of excited argon species, implying that the afterglow phenomenon can be used to optimize the pulse operation. Compared to continuous wave operation, the time-averaged emissions of Ar* and OH radical are enhanced by about 60% and 30%, respectively, in the pulsed microwave operation, suggesting more efficient generation of reactive species.