Reactive oxygen species‐induced heterogeneous photocatalytic degradation of organic pollutant Rhodamine B by copper and zinc aluminate spinels

Abstract

BACKGROUND: The importance of potable water is immeasurable and its contamination by pollutants is a serious environmental problem. Rhodamine B (RhB), one such pollutant, is highly toxic to various organisms and may cause long-term undesirable effects when improperly disposed of. Thus, development of an efficient treatment technique is necessary. Among the new oxidation methods, heterogeneous photocatalysis is an emerging pollutant destructive technology. RESULTS: The photocatalytic activities of copper (Cu) and zinc (Zn) aluminate spinels (CuAl 2 O 4 and ZnAl 2 O 4 ) was evaluated.Chemical and physical properties were considered, and ZnAl 2 O 4 showed higher RhB degradation efficiency (73.90% in only 10 min) than CuAl 2 O 4 (51.95% in 10 min), reaching up to 100% in 30 min. According to results, a further RhB catalytic degradation pathway by ZnAl 2 O 4 was monitored by UV-visible spectrometry and ultra-high performance liquid chromatography coupled to diode array detection (UHPLC-DAD) analysis. When applied to wastewater from gemstone beneficiation, containing elevated RhB concentration, the ZnAl 2 O 4 caused 88% color removal in 120 min and its pollutant removal rate was 18 times greater than the commonly used ZnO.CONCLUSION: The superior performance of ZnAl 2 O 4 can be attributed to better pore properties, responsible for providing more active sites. These identified reactive oxygen species (ROS)-induced interactions and the species demonstrated that degradation occurs due to generation of O 2•and h + . Thus, ZnAl 2 O 4 proved to be an efficient photocatalyst for quick RhB pollutant degradation with promising potential for real wastewater treatment applications. CONCLUSIONBoth Cu and Zn aluminate spinels presented elevated catalytic performance, but when compared, ZnAl 2 O 4 presented higher J Chem Technol Biotechnol 2020; 95: 791-797

Solar light‐induced photocatalytic degradation of methylparaben by g‐C3N4 in different water matrices

“…NHE) than the potential of OH • formation (1.99 V vs . NHE), 31 excluding their participation in the degradation mechanism. Thus, it is believed that the formation of photogenerated holes plays a leading role in the photocatalytic decomposition of MeP on g‐C 3 N 4 , while O 2 • − can also promote the degradation of MeP molecules.…”

“…These results show that the contribution of hydroxyl radicals was excluded from the MeP degradation mechanism, as no significant change was observed. This was expected since g-C 3 N 4 valence band (VB) oxidation potential is located higher (1.4 V vs. NHE) than the potential of OH • formation (1.99 V vs. NHE), 31 excluding their participation in the degradation mechanism. Thus, it is believed that the formation of photogenerated holes plays a leading role in the photocatalytic decomposition of MeP on g-C 3 N 4 , while O 2…”

“…During photocatalysis, organic molecules can react either directly, by the photogenerated holes (h + ) on the surface of photocatalysts, or indirectly, through the intermediate formation of several kinds of active oxygen species by h + and e − redox reactions. [27][28][29][30][31][32] In recent years, researchers seem to agree that in order to increase the practical application of the photocatalytic process, major efforts need to be focused on the development of visible lightresponsive photocatalytic materials. Recently, graphitic carbon nitride (g-C 3 N 4 ) has received much attention because it absorbs a significant portion of visible light, due to its medium band gap of ∼2.7 eV, and because it is easy to fabricate, economic, nontoxic, and chemically and thermally stable for photocatalytic and photoelectrochemical applications.…”

“…This process uses photocatalysts, which are semiconductor materials, and artificial or solar light energy to decompose organic and hazardous pollutants, and changing them into harmless products. During photocatalysis, organic molecules can react either directly, by the photogenerated holes (h + ) on the surface of photocatalysts, or indirectly, through the intermediate formation of several kinds of active oxygen species by h + and e − redox reactions 27–32 . In recent years, researchers seem to agree that in order to increase the practical application of the photocatalytic process, major efforts need to be focused on the development of visible light‐responsive photocatalytic materials.…”

Visible‐light driven photodegradation of phenol over niobium oxide‐loaded fibrous silica titania composite catalyst

“…Its highly efficient degradation performance and mineralisation, led to formation of carbon dioxide (CO 2 ) and water (H 2 O) as end products. [9][10][11][12][13] In this perspective, photocatalysis has been widely explored as a technology for removing phenol from wastewaters. Out of the many semiconductor photocatalysts, titanium dioxide (TiO 2 ) is a favoured material to be utilized as photocatalyst for aqueous pollutant degradation and water splitting, owing to practical merits such as nontoxicity, good photochemical stability, and low material cost.…”