Degradation of refractory dibutyl phthalate by peroxymonosulfate activated with novel catalysts cobalt metal-organic frameworks: Mechanism, performance, and stability: Mechanism, performance, and stability

In this work, a new effective and relatively stable heterogeneous catalyst of Metal-Organic Framework Co₃(BTC)₂·12H₂O (Co-BTC) has been synthesized and tested to activate peroxymonosulfate (PMS) for removal of refractory dibutyl phthalate (DBP). Co-BTC(A) and Co-BTC(B) were synthesized by different methods, which resulted in different activity towards PMS. The results indicated that Co-BTC(A) showed better performance on DBP degradation. The highest degradation rate of 100% was obtained within 30 min. The initial pH showed respective level on DBP degradation with a rank of 5.0 > 2.75 > 9.0 > 7.0 > 11.0 in PMS/Co-BTC(A) system. No remarkable reduction of DBP was observed in the catalytic activity of Co-BTC(A) at 2nd run as demonstrated by recycling. However, the DBP degradation efficiency decreased by 8.26%, 10.9% and 25.6% in the 3rd, 4th, and 5th runs, respectively. The loss of active catalytic sites of Co(II) from Co-BTC(A) is responsible for the activity decay. Sulfate radicals (SO₄^−•) and hydroxyl radicals (^•OH) were found at pH 2.75. Here, we propose the possible mechanism for activation of PMS by Co-BTC(A), which is involved in homogeneous and heterogeneous reactions in the solutions and the surface of Co-BTC(A), respectively.