Synergistic Degradation of 2,4,4′-Trihydroxybenzophenone Using Carbon Quantum Dots, Ferrate, and Visible Light Irradiation: Insights into Electron Generation/Consumption Mechanism

Abstract

In this study, we reported a unique single-step synthesis of photocatalytic carbon quantum dots (CQDs) with high electron density, efficient aggregation-induced emission, and improved surface chemistry properties. As-synthesized CQDs were applied with ferrate (a reactive and green oxidant) to synergistically degrade 2,4,4′-trihydroxybenzophenone (2,4,4′-HBP). The restriction of molecular rotation, vibration in the crystal structure, modification of the surface chemistry, and the aggregation/ quenching of CQDs were highlighted by comprehensive characterization. Newly synthesized CQDs' generated electrons were consumed by ferrate, and this mechanism was highlighted by photoluminescence analyses. It was found that the photoluminescence intensity of CQDs was reduced by more than 96% when ferrate was introduced into the CQDs reaction system. The reaction kinetics of 2,4,4′-HBP degradation was inspected at different pH values (7.0, 8.0 and 9.0) using ferrate in a single dose and multipledose (sequential) additions. The CQDs + ferrate + visible light (Vis) was proven to be the best reaction system with a 99.9% degradation efficiency, as compared to CQDs alone (63%) and ferrate single dose (85%) and multiple-dose (96%) methods. In addition, 10 reaction intermediates were identified, implying that C−C cleavage, hydroxylation, self, cross, and end linkage were involved in the potential reaction mechanism. Besides, hydroxyl radicals were found to be the primary reactive species in electron paramagnetic resonance (EPR) analyses. The computational analyses including density functional theory and molecular orbital distribution elucidated the reaction sites of CQDs and 2,4,4′-HBP. These findings have important implications in understanding electron generation and consumption mechanisms with the synergetic contribution of CQDs and ferrate to degrade organic pollutants such as 2,4,4′-HBP.

How Should We Activate Ferrate(VI)? Fe(IV) and Fe(V) Tell Different Stories about Fluoroquinolone Transformation and Toxicity Changes

“…Generally, oxidation capacities of iron species are in the order of Fe­(V) > Fe­(IV) > Fe­(VI). The reaction rate constants of Fe­(IV) and Fe­(V) with typical MPs are generally two to five orders of magnitude higher than that of Fe­(VI). , Many studies have been conducted to activate Fe­(VI) to generate more Fe­(IV) and Fe­(V), through the utilization of photocatalysis, carbon-based materials, and other oxidants. − For example, ferrate has been used with biochar to generate more Fe­(IV) and/or Fe­(V) for sulfamethoxazole (SMX) oxidation . Ultraviolet (UV) has been used to enhance the contribution of Fe­(IV) to SMX oxidation compared with application of Fe­(VI) alone .…”

Synthesis and Characterization of a Tertiary Composite of Cu, Mn, and g-C3N4: An Efficient Visible Light-Active Catalyst for Wastewater Treatment

“…The synthesis can be easily done by heating nitrogen-rich organic compounds, for example, urea [CO­(NH 2 ) 2 ], thiourea (H 2 NCSNH 2 ), melamine (C 3 H 6 N 6 ), cyanamide (CN 2 H 2 ), and dicyanamide (C 2 N –3 ) . In the current study, we have used melamine as a precursor to synthesize GCN due to its low cost. , Although GCN is an efficient catalyst, its catalytic efficiency for the photodegradation of organic pollutants still needs to be improved. ,, Although many nonmetals such as B, C, N, O, S, P, F, and I have been doped on GCN to improve the photocatalytic activity, in comparison, doping of metals into GCN improves the catalytic efficiency 7–10 times. ,, …”

“… 6 , 7 Although GCN is an efficient catalyst, its catalytic efficiency for the photodegradation of organic pollutants still needs to be improved. 6 , 8 , 9 Although many nonmetals such as B, C, N, O, S, P, F, and I have been doped on GCN to improve the photocatalytic activity, in comparison, doping of metals into GCN improves the catalytic efficiency 7–10 times. 4 , 9 , 10 …”

“… 6 , 8 , 9 Although many nonmetals such as B, C, N, O, S, P, F, and I have been doped on GCN to improve the photocatalytic activity, in comparison, doping of metals into GCN improves the catalytic efficiency 7–10 times. 4 , 9 , 10 …”

Effects of Aging on Adsorption of Tetracycline Hydrochloride by Humin

“…As statistical data reveal, TC consumption in China in 2013 was as high as 1.2 × 10 5 t. The TC residue in the soil environment of northern China was found to be 0.021-0.105 mg/kg by Hu et al TCs are among the most frequently used antibiotics [16]. In addition, humin (HM) is selected as the absorbent here, because it is an important component of organic matter that is rich in oxygen-containing functional groups (e.g., hydroxy, carboxyl, and carbonyl) and can adsorb and thus bind with TCs [17][18][19]. This paper adopts the inorganic mineral coating method recommended by the International Humic Substances Society (IHSS) to simulate the aging process.…”