Ozonation of phenolic wastewaters in the presence of a perovskite type catalyst

Catalytic ozonation of phenolic acids over a Mn–Ce–O catalyst

“…This reactivity is enhanced when the ring is activated by the presence of electrondonating groups which is the case of hydroxyl (OH), a strong activating group, and methoxy (CH 3 O) a moderate activating group, present in the phenolic acids under study. Nevertheless, the accumulation of different refractory intermediates, such as low molecular weight carboxylic acids, during ozonation process leads to a low level of mineralization [1]. TPh is totally removed after 50 min when catalytic ozonation over Mn-Ce-O (70/30) is performed, which truly enhances mineralization with a high TOC removal even at early reaction times.…”

“…The presence of phenolic mixtures in wastewaters is a common factor shared by a number of industries mainly the agro-industries [1]. These organic compounds incorporate in the effluents a significant contaminant load due to their high toxicity, refractory character and high stability in aqueous medium [2].…”

“…In the context of phenolic wastewaters, Carbajo et al [1] studied the efficiency of a perovskite type catalyst for the abatement of a mixture of phenolic compounds as well as of industrial phenolic effluents: wine distillery, debittering stage to produce table olives and OMW.…”

Investigation of photocatalytic ozonation treatment of water over WO3 under visible light irradiation

“…Furthermore, according to the previous report on detailed investigation of phenol degradation process by ozonation, the TOC removal process may be achieved through the formation and decomposition of first intermediates (e.g., quinones, hydroquinones, and unsaturated open ring compounds), which are easily oxidized by direct molecular ozone attack, and secondary ozone refractory intermediates (e.g., pyrubic acid, ketomalonic acid, and oxalic acid) which are not easily oxidized by direct molecular ozone attack. 26) Accordingly, the effect of the initial phenol concentration on TOC removal was investigated to clarify how the combined effect of photocatalysis and ozonation contributes to complex phenol degradation process. Figure 3 shows time courses for TOC removal at different initial phenol concentrations using the O 3 /vis/WO 3 system.…”

“…An increase of temperature should lead to an increase in the rate of ozone self-decomposition, which generates active species for the TOC removal; therefore, the degradation rate of organic compounds is increased with increasing water temperature for water treatment with ozone. 26),30),32),33) On the other hand, an increase of water temperature should lead to a decrease of ozone solubility in water, which has a negative effect on the TOC degradation efficiency. 30),32),33) This is consistent with the decrease in the TOC removal efficiency at 45°C, compared with that at 35°C in the O 3 /dark/WO 3 system, from the second stage (from ca.…”