Persulfate Activation Using Biochar from Pomegranate Peel for the Degradation of Antihypertensive Losartan in Water: The Effects of Pyrolysis Temperature, Operational Parameters, and a Continuous Flow Reactor

Abstract

Biochar derived from pomegranate peel at different pyrolysis temperatures (450, 600, and 850 °C) was synthesized and characterized by BET, XRD, FTIR, and SEM-EDX. Its catalytic efficiency in the degradation of the antihypertensive losartan (LOS) in the presence of sodium persulfate was examined. The biochar pyrolyzed at 850 °C exhibited higher catalytic activity, which was correlated with the greater surface area and higher concentration of minerals on its surface. Interestingly, despite adsorption being favored at alkaline pH, pH 3 showed the highest LOS degradation. LOS decomposition followed pseudo-first-order kinetics. The addition of persulfate significantly increased LOS reduction, while the presence of inorganic and organic water matrix constituents such as sodium chloride, bicarbonate, and humic acid inhibited the oxidation. Experiments conducted with radical scavengers revealed that both hydroxyl and sulfate radicals, as well as singlet oxygen, participated in LOS decomposition, with the former being the dominant species. Using a continuous flow reactor, the system exhibited a satisfactory steady-state performance of 90% LOS removal for 114 h. Afterward, a moderate decrease in performance was observed, which can be attributed to the alteration of the catalyst’s surface and mineral dissolution due to acidity.