Solar light photocatalytic transformation of heptachlorobiphenyl (PCB 180) using g-C3N4 based magnetic porous photocatalyst

Investigation of fullerene and non-fullerene materials in organic photocatalysts on the efficiency of photocatalytic degradation of polychlorinated biphenyls

The photocatalytic degradation of polychlorinated biphenyls (PCBs) is advancing, yet the efficiency of degradation within the visible spectral range continues to encounter significant challenges. In this study, two biochar-based organic semiconductor photocatalysts, Active Carbon@PTQ10 (5,8-Dibromo-6,7-difluoro-2-(2-hexyldecoxy)quinoxaline; trimethyl-(5-trimethylstannylthiophen-2-yl)stannane): ITIC-Th (Propanedinitrile,2,2'-[[6,6,12,12-tetrakis(5-hexyl-2-thienyl)-6,12-dihydrodithieno[2,3-d: 2',3'-d'] -s-indaceno[1,2-b:5,6-b'] dithiophene-2,8-diyl] bis[methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]] bis-) (AC@PI) and Active Carbon@PTQ10: PC71BM (6,6)-phenyl C71 butyric acid methyl ester), were synthesized using a wide bandgap material, PTQ10, as the electron donor, along with a non-fullerene material, ITIC-Th, and a fullerene material, PC71BM, as the acceptors, respectively. Under optimized conditions, AC@PI degraded 93.4 % of 2,2 ',4,4 '-tetrachlorobiphenyl (PCB 47) within 60 min. By incorporating a non-fullerene acceptor (ITIC-Th), AC@PI exhibits a larger surface photopressure, a lower hole-electron transfer ratio, a broader absorption spectrum (400 - 1000 nm), and enhanced structural stability. AC@PI can generate photogenerated electrons and holes, as well as superoxide anions (O2-) and hydroxyl radicals (OH), through type II heterojunctions, which contributes to its exceptional properties. This study synthesized novel organic semiconductor catalysts that offer a green, efficient, and non-toxic method for the degradation of aromatic pollutants, such as polychlorinated biphenyls.

Structural design of thiadiazole-based donor-acceptor COF/Fe-doped N vacancy g-C3Nx nanosheets for photocatalytic nitrogen fixation under visible light

The rational design of efficient photocatalysts to achieve artificial nitrogen fixation is an urgent challenge. Herein, we combined donor-acceptor covalent organic framework with iron-doped nitrogen vacancy graphitized carbon nitride (D-A COF/Fe-g-C3Nx) for photocatalytic nitrogen fixation. The photocatalyst exhibited good crystallinity, high porosity, and a large specific surface area. Without a sacrificial agent, the optimal 40 % D-A COF/Fe-g-C3Nx exhibited an excellent rate of ammonia production (646 μmol h-1 g-1) at 420 nm, and durable stability after successive cycling. Exhaustive experimental research and theory calculations verified that the D-A unit and Fe doping redistributed the distribution of the charge, which enhanced the visible light utilization and provided chemisorption sites for further polarization. Besides N-vacancies can serve as electron-trapping active sites to promote the directional migration of carriers. The reaction mechanism demonstrated that superoxide radical and hydrogen peroxide were formed by electron and hole, respectively, which promote the reduction of nitrogen to ammonia. This work provides a new idea for the rationalizing design of efficient catalysts for photocatalytic nitrogen fixation under mild conditions.

Photocatalytic Degradation of Dielectric Mineral Oil with PCBs Content Coupled with Algae Treatment

Insulating oil contaminated with polychlorinated biphenyls (PCBs) is an environmentally important pollutant. This research focused on the establishment of the optimum conditions under which photocatalytic oxidation can be used together with biotreatment using the Nostoc sp. microorganism to degrade PCBs present in used dielectric oils. Among the optimal conditions studied were PCB concentration, initial pH, and titanium dioxide (TiO₂) concentration for the photocatalytic step, and PCB concentration and photoperiod for the biotreatment step. The results indicate that the optimal conditions necessary for photocatalytic degradation were a pH of 6.10, 113 mg/L TiO₂, and 765 mg/L PCBs, achieving close to 90% removal. For the biotreatment step, the results showed that PCBs progressively inhibited the microbiological growth, with the lowest cellular growth observed in the medium with the highest PCB concentration.