Activated carbon‐supported cobalt molybdate as a heterogeneous catalyst to activate peroxymonosulfate for removal of organic dyes

Abstract

Activated carbon-supported cobalt molybdate (CoMoO 4 /AC) composite was conveniently fabricated using a simple hydrothermal route and hightemperature calcination, aiming to create a novel heterogeneous catalyst for activation of peroxymonosulfate (PMS) to degrade organic dyes. The CoMoO 4 /AC catalyst was characterized using scanning electron microscopy, powder X-ray diffraction, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, elemental mapping analysis and X-ray photoelectron spectroscopy. Efficient catalytic activity, high stability and superior reusability were observed. Additionally, the catalytic performance of CoMoO 4 /AC was systematically assessed through numerous controlled experiments and several operational factors, such as catalyst dosage, oxidant dosage, reaction temperature, initial pH and catalyst stability. Under the condition of CoMoO 4 /AC = 0.1 g l −1 , oxidant = 2.0 mM, dye = 100 mg l −1 , T = 25°C, the removal of methylene blue reached 90% within 60 min without pH adjustment. Batch experiment results showed that the degradation of organic dye relied upon the dosage of catalyst and oxidant and reaction temperature. Further, high catalyst and oxidant dosage, as well as high reaction temperature, were favorable for dye removal. Moreover, quenching experiments suggested that the CoMoO 4 /AC catalyst successfully activated PMS to generate sulfate and hydroxyl radicals. A rational mechanism is proposed based on a non-radical process and a free radical process. The result revealed that the enhanced active sites were mainly ascribed to the synergistic effects between Co species and oxygen-containing functional groups (especially ketone groups) on the catalyst surface. The findings of this study demonstrated the as-prepared CoMoO 4 /AC composite has potential superiority for refractory organic contaminant removal from water.

Accelerated ZnMoO4 photocatalytic degradation of pirimicarb under UV light mediated by peroxymonosulfate

“…As illustrated in Figure , the removal efficiency of pirimicarb increased from 63 to 97% within 4 h when the concentration of the catalyst increased from 0.1 to 1.0 g l −1 . This can be ascribed to the efficient generation of active radicals resulting from the provision of more active sites for PMS activation . However, the efficiency decreased slightly when the concentration of ZnMoO 4 was above 1.0 g l −1 .…”

“…The extant form of PMS depends mainly on the second acid dissociation constant (p K a = 9.4) and the pH value of the solution. The parent acid, H 2 SO 5 , forms the main species at a lower pH level, instead of HSO 5 − . In addition, the presence of hydrogen ions (H + ) acts as a scavenging medium for the hydroxyl and sulfate radicals at this lower pH, as shown in equations and .…”

“…Tao et al . have very recently described the activation of PMS using carbon‐supported cobalt molybdate for removal of organic dyes . To the best of our knowledge, studies of the photocatalytic oxidation performance of ZnMoO 4 in the presence of PMS have not been reported yet.…”