New breakthrough in rapid degradation of lignin derivative compounds · A novel high stable and reusable green organic photocatalyst.

The pulp and paper sectors are thriving yet pose significant environmental threats to water bodies, mainly due to the substantial release of pollutants. Lignin-derived compounds are among the most problematic of these contaminants. To address this issue, we present our initial results on utilizing organic semiconductor photocatalysis under visible light for treating lignin-derived compounds. Our investigation has been centered around creating a green and cost-effective organic semiconductor photocatalyst. This catalyst is designed using a structure of bagasse cellulose spheres to support PM6 (poly[(2,6-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene))-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)-benzo[1,2-c:4,5-c']dithiophene-4,8-dione))]: MeIC (3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-cyclopentane-1,3-dione[c]-1-methyl-thiophe))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']-dithiophene)). This photocatalyst demonstrates remarkable efficiency, achieving over 91 % degradation of lignin-derived compounds. The superior photocatalytic performance is attributed to three main factors: (1) The ability of PM6 to broaden MeIC's absorption range from 300 to 800 nm, allowing for effective utilization of visible light; (2) the synergistic interaction between PM6 and MeIC, which ensures compatible energy levels and a vast, evenly spread surface area, promoting charge mobility and extensive donor/acceptor interfaces. This synergy significantly enhances the generation and transport of carriers, resulting in a high production of free radicals that accelerate the decomposition of organic materials; (3) The deployment of PM6:MeIC on biomass-based carriers increases the interaction surface with the organic substances. Notably, PM6: MeIC showcases outstanding durability, with its degradation efficiency remaining between 84 % and 91 % across 100 cycles. This study presents a promising approach for designing advanced photocatalysts aimed at degrading common pollutants in papermaking wastewater.

Bagasse cellulose-based S-type Bi2O3/Zn3In2S6 photocatalyst for efficient and stable degradation of 2,4-dichlorophenol under visible light.

The environmental and human health hazards posed by 2,4-dichlorophenol (2,4-DCP) call for effective degradation technologies. This research investigates the design and application of a Bi2O3/Zn3In2S6 heterojunction photocatalyst, a 'S scheme', which was constructed via a simple hydrothermal method. The photocatalyst was then embedded in a sugarcane bagasse cellulose carrier (SBC/BO/ZIS), demonstrating excellent 2,4-DCP degradation capacity. The results show that S-type Bi2O3/Zn3In2S6 promotes the separation of photogenerated carriers. The SBC/BO/ZIS complex, in comparison with Bi2O3 and Zn3In2S6 alone, amplifies specific surface area (91.7880 m2/g) and broadens the light absorption range (570 nm) of materials, showing robust photocatalytic performance. The degradation rate of 50 mg/L 2,4-DCP reached an impressive 97% within 120 min. The encapsulation of BO/ZIS in SBC not only increases the efficiency of material recovery and recycling but also allows for continuous degradation of 2,4-DCP in cyclic manners, maintaining a degradation rate between 90% and 97%. XRD characterization shows that the physical properties of the material are not affected. The degradation of 2,4-DCP was dominantly controlled by active species (·OH and ·O2-) identified by electron paramagnetic resonance analysis and free radical trapping experiments. This innovative design significantly enhances sunlight utilization and effectively curbs charge carrier recombination, while also promoting material recovery and utilization. These attributes establish a foundation for a cost-effective and efficient means of treating actual wastewater containing 2,4-DCP.

Visible-light photocatalytic degradation of water-soluble polyvinyl alcohol in aqueous solution by Cu2O@TiO2: Optimization of conditions, mechanisms and toxicity analysis.

Polyvinyl alcohol (PVA), a water-soluble synthetic polymer, is one of the most prevalent non-native polyvinyl alcohols found in the environment. Due to its inherent invisibility, its potential for causing severe environmental pollution is often underestimated. To achieve efficient degradation of PVA in wastewater, a Cu2O@TiO2 composite was synthesized through the modification of titanium dioxide with cuprous oxide, and its photocatalytic degradation of PVA was investigated. The Cu2O@TiO2 composite, supported by titanium dioxide, facilitated photocarrier separation and demonstrated high photocatalytic efficiency. Under alkaline conditions, the composite exhibited a 98% degradation efficiency for PVA solutions and a 58.7% PVA mineralization efficiency. Radical capture experiments and electron paramagnetic resonance (EPR) analyses revealed that superoxide radicals primarily drive the degradation process within the reaction system. Throughout the degradation process, PVA macromolecules are broken down into smaller molecules, including ethanol, and compounds containing aldehyde, ketone, and carboxylic acid functional groups. Although the intermediate products exhibit reduced toxicity compared to PVA, they still pose certain toxic hazards. Consequently, further research is necessary to minimize the environmental impact of these degradation products.

Study on Degradation of 1,2,4-TrCB by Sugarcane Cellulose-TiO2 Carrier in an Intimate Coupling of Photocatalysis and Biodegradation System.

1,2,4 trichlorobenzene (1,2,4-TrCB) is a persistent organic pollutant with chemical stability, biological toxicity, and durability, which has a significant adverse impact on the ecological environment and human health. In order to solve the pollution problem, bagasse cellulose is used as the basic framework and nano TiO2 is used as the photocatalyst to prepare composite carriers with excellent performance. Based on this, an intimate coupling of photocatalysis and biodegradation (ICPB) system combining photocatalysis and microorganisms is constructed. We use the combined technology for the first time to deal with the pollution problem of 1,2,4-TrCB. The biofilm in the composite carrier can decompose the photocatalytic products so that the removal rate of 1,2,4-TrCB is 68.01%, which is 14.81% higher than those of biodegradation or photocatalysis alone, and the mineralization rate is 50.30%, which is 11.50% higher than that of photocatalysis alone. The degradation pathways and mechanisms of 1,2,4-TrCB are explored, which provide a theoretical basis and potential application for the efficient degradation of 1,2,4-TrCB and other refractory organics by the ICPB system.

Coupling of photocatalysis and biological treatment for elemental chlorine free bleaching wastewater: Application of factorial design methodology.

In this study, the visible-light-induced intimately coupled photocatalysis and biodegradation (ICPB) technology was fabricated using the TiO2/bagasse cellulose composite as the carrier and Phanerochaete mixed activated sludge as the biological source. The ICPB degradation effect of elemental chlorine free (ECF) bleaching wastewater was evaluated via the response surface design. Then, the wastewater was characterized, including absorbable organic halogen (AOX), dissolved organic carbon (DOC), chemical oxygen demand (COD), chroma, pH, suspended solids, and the organic compound changes in wastewater were analyzed by fourier transform infrared spectroscopy (FT-IR). Under the optimal conditions of pH 7, carrier filling rate of 5%, aeration rate of 2 L/min, and reaction time of 7 h, the degradation efficiencies of AOX, COD, and DOC were 95%, 91%, and 82%, respectively. The X-ray photoelectron spectroscopy (XPS) results of the ICPB carrier after the reaction were almost identical to those before the reaction. The biomass and its activity on the ICPB system were analyzed by the dominant bacteria during degradation (Curaneotrichosporon, Paenibacillus, Cellulonas, Phanerochaete, Dechlorobacter, Rhodotorula, Sphingobacterium, and Ruminiclostridium), which had a good degradation effect on wastewater. This study affords a novel method for the degradation of ECF bleaching wastewater and a new idea for ICPB technology optimization.

Degradation of chlorine dioxide bleaching wastewater and response of bacterial community in the intimately coupled system of visible-light photocatalysis and biodegradation.

Intimate coupling of visible-light photocatalysis and biodegradation (ICPB) offers potential for degrading chlorine dioxide bleaching wastewater. In this study, we reported a TiO2-coated sponge biofilm carrier with significant adhesion of TiO2 and the ability to accumulate biomass in its interior. Four mechanisms possibly acting in ICPB were tested separately: adsorption of chlorine dioxide bleaching wastewater to the carrier, photolysis, photocatalysis, and biodegradation by the biofilm inside the carrier. The carrier had an adsorption capacity of 17% and 16% for CODcr and AOX, respectively, in the wastewater. The photodegradation rate of wastewater was very low and could be ignored. Both biodegradation (AOX 30.1%, CODcr 33.8%, DOC 26.2%) and photocatalysis (AOX 65.1%, CODcr 71.2%, DOC 62.3%) possessed a certain degradation efficiency of wastewater. However, the removal rate of AOX, CODcr, and DOC in wastewater treatment by protocol ICPB reached 80.3%, 90.5%, and 86.7%. FT-IR and GC-MS analysis showed that the ICPB system had photocatalytic activity on the surface of the porous carrier in vitro, which could transform organic into small molecules for microbial utilization or complete mineralization. Moreover, the biofilm in the interior of the TiO2-coated sponge carrier could mineralize the photocatalytic products, which enhanced the removal of AOX, CODcr, and DOC by more than 15.2%, 20.0%, and 24.0%, respectively. The biofilm in the carrier of the ICPB system evolved, enriched in Proteobacteria, Chloroflexi, Bacteroidetes, and Actinobacteria, microorganisms known to play active roles in the biodegradation of papermaking wastewater.

Preparation and Photocatalytic Properties of a Bagasse Cellulose-Supported Nano-TiO2 Photocatalytic-Coupled Microbial Carrier.

Intimate coupling of photocatalysis and biodegradation (ICPB) has shown promise in removing unwanted organic compounds from water. In this study, bagasse cellulose titanium dioxide composite carrier (SBC-TiO2) was prepared by low-temperature foaming methods. The optimum preparation conditions, material characterization and photocatalytic performance of the composite carrier were then explored. By conducting a single factor test, we found that bagasse cellulose with a mass fraction of 4%, a polyvinyl alcohol solution (PVA) with a mass fraction of 5% and 20 g of a pore-forming agent were optimum conditions for the composite carrier. Under these conditions, good wet density, porosity, water absorption and retention could be realized. Scanning electron microscopy (SEM) results showed that the composite carrier exhibited good biologic adhesion. X-ray spectroscopy (EDS) results confirmed the successful incorporation of nano-TiO2 dioxide into the composite carrier. When the mass concentration of methylene blue (MB) was 10 mg L-1 at 200 mL, 2 g of the composite carrier was added and the initial pH value of the reaction was maintained at 6, the catalytic effect was best under these conditions and the degradation rate reached 78.91% after 6 h. The method of preparing the composite carrier can aid in the degradation of hard-to-degrade organic compounds via ICPB. These results provide a solid platform for technical research and development in the field of wastewater treatment.