Effect of Phosphate Buffer upon CuO/Al₂O₃and Cu (II) Catalyzed Ozonation of Oxalic Acid Solution

CuO/SBA-15 catalyst for the catalytic ozonation of mesoxalic and oxalic acids. Water matrix effects

“…It is reasonable to assume that both factors contribute to the faster depletion of oxalic and mesoxalic acids at basic pH. Similar results have previously been reported [21].…”

“…The effect of phosphate was also strong in spite of the low concentration (0.01 mmol/L). The results obtained suggest that under non-catalytic reaction, both acids are probably oxidised mainly by the hydroxyl radicals; the anions mentioned above to a greater or lesser extent, have been recognised as radical scavengers [21,[56][57][58] and their presence could affect the indirect reaction pathway. The presence of sulphate (using sodium sulphate as source) did not affect the non-catalytic depletion of mesoxalic acid, and the reaction of oxalic acid was only slightly affected.…”

“…However, at acidic pH the concentration of leached copper was as high as 15 mg/L (%40% of the total active phase). The presence of dissolved copper can increase the rate of the homogeneous catalytic reaction, which could contribute to accelerating the decomposition of oxalic acid [16,21].…”

“…Another aspect to take into consideration in catalytic water ozonation is that the main inorganic anions found in surface water and STP effluent, such as chloride, sulphates and phosphates, are commonly poisons for the catalysts blocking the active catalytic sites. The most frequently used catalysts in ozonation are those based on manganese, copper, alumina, titanium and iron oxides as well as activated carbon, which acts as a radical promoter and support [12,16,[18][19][20][21][22][23][24].…”

Pathway of the ozonation of 2,4,6-trichlorophenol in aqueous solution

“…Experiments were carried out in buffered and non-buffered solutions, where either phosphate buffer or NaOH was applied to adjust the pH value to be 7.5. The buffer was produced by blending 260 mmol/L KH 2 PO 4 and 260 mmol/L Na 2 HPO 4 with a volume ratio of 4:21 to make a buffer stock solution of pH = 7.5 [13]. N,N-diethyl-p-phenylenediamine (DPD) and horseradish peroxidase (POD) solutions were prepared according to the literature and used up within 6 h [14].…”