Rice husk–based pyrogenic carbonaceous material efciently promoted peroxymonosulfate activation toward the non‑radical pathway for the degradation of pharmaceuticals in water

Abstract

ABSTRACT: Pristine pyrogenic carbonaceous material (BRH) obtained from rice husk and modifed with FeCl3 (BRH-FeCl3) were prepared and explored as carbocatalysts for the activation of peroxymonosulfate (PMS) to degrade a model pharmaceutical (acetaminophen, ACE) in water. The BRH-FeCl3/PMS system removed the pharmaceutical faster than the BRH/PMS. This is explained because in BRH-FeCl3, compared to BRH, the modifcation (iron played a role as a structuring agent mainly) increased the average pore diameter and the presence of functional groups such as -COO−, -Si–O−, or oxygen vacancies, which allowed to remove the pollutant through an adsorption process and signifcant carbocatalytic degradation. BRH-FeCl3 was reusable during four cycles and had a higher efciency for activating PMS than another inorganic peroxide (peroxy-disulfate, PDS). The efects of BRH-FeCl3 and PMS concentrations were evaluated and optimized through an experimental design, maximizing the ACE degradation. In the optimized system, a non-radical pathway (i.e., the action of singlet oxygen, from the interaction of PMS with defects and/or -COO−/-Si–O− moieties on the BRH-FeCl3) was found. The BRH-FeCl3/ PMS system generated only one primary degradation product that was more susceptible to biodegradation and less active against living organisms than ACE. Also, the BRH-FeCl3/PMS system induced partial removals of chemical oxygen demand and dissolved organic carbon. Furthermore, the carbocatalytic system eliminated ACE in a wide pH range and in simulated urine, having a low-moderate electric energy consumption, indicating the feasibility of the carbocatalytic process to treat water polluted with pharmaceuticals.