Rapid degradation of Congo red wastewater by Rhodopseudomonas palustris intimately coupled carbon nanotube - Silver modified titanium dioxide photocatalytic composite with sodium alginate

Interface dependent electron shunting in graphene-integrated intimately coupled photocatalytic biodegradation

Intimately coupled photocatalytic biodegradation (ICPB) has been recently developed as an efficient wastewater treatment technique, particularly for removing persistent organic pollutants. However, photocatalyst/biofilm interaction in terms of photoelectron transfer and its effect on the overall performance of ICPB has not been explored. To investigate these points, interface-engineered composites of bismuth vanadate and reduced graphene oxide with low degree (BiVO4/rGO-LC) and high degree of their contact (BiVO4/rGO-HC) were fabricated and applied for ICPB. As a result, the composites displayed interface-dependent optical, structural and charge carrier separation properties. The photoelectrochemical measurements confirmed the presence of photoelectron shunting between photocatalyst and biofilm, while the current density was higher (smaller Nyquist arc) for BiVO4/rGO-HC than BiVO4/rGO-LC and BiVO4 in ICPB protocol, confirming the crucial role of intimate interfacial contact for photoelectron shunting from BiVO4 to biofilm. Consequently, the presence of graphene and its interfacial quality dictated the photoelectron shunting between photocatalyst and biofilm, enhancing photoelectron-holes separation and achieving superior degradation rate of tetracycline hydrochloride for BiVO4/rGO-HC (0.035 h-1) compared to BiVO4/rGO-LC (0.0128 h-1) and BiVO4 (0.011 h-1) in ICPB protocol. The electrical energy per order required for removal of tetracycline hydrochloride in the ICPB protocol exhibited the lowest value for BiVO4/rGO-HC among the tested materials and treatment protocols. These results highlight the importance of photoelectron shunting in enhancing efficiency of ICPB by engineering graphene at the interface of photocatalyst and biofilm. This unveiled mechanism may serve as an excellent potential in designing energy-efficient ICPB systems targeting wastewater matrices.

Study on photocatalytic degradation and antibacterial properties of conjugated microporous polymers/TiO2 composite membranes

Conjugated microporous polymers (CMPs) are widely used in the field of photocatalysis due to their unique conjugated structures and various synthesis methods. Herein, we report the design and synthesis of conjugated microporous polymers hollow spheres (CMPs-HS) superhydrophilic modified by acetylcysteine (CMPs-HS-S) and compounded with the inorganic semiconductor material titanium dioxide (CMPs-HS-S/TiO2) for efficient photocatalytic degradation. To facilitate recycling, the composite membrane material was prepared by combining the materials mentioned above with PVDF membrane. The composite membrane materials had good hydrophilic and photocatalytic properties. Under visible light, the degradation rate of tetracycline (TC) (10 mg/L 180 min) reached 90 %, and the bactericidal rates for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 89 % and 99.99 %, respectively. The efficient photocatalytic performance of the composite membranes could be attributed to the hollow sphere structure of CMPs and the role of TiO2 as a photogenic electron transfer platform. Additionally, the hydrophilicity of the membrane also helped to accelerate the occurrence of photocatalytic reactions. After electron paramagnetic resonance (EPR) detection, h+, 1O2 and O2- were proved to be important reactive substances, which played a major role in degradation. These studies reflect the versatility of CMPs-based photocatalysts and provide a new idea for the future development of CMPs-based photocatalysts.

Novel MOF-based vanadium and 2,2 -bipyridine-4,4 -dicarboxylic acid as phenomenal dye adsorbent and antimicrobial agent

In this study, a new MOF (metal-organic framework) based on vanadium and 2,2-bipyridine-4,4-dicarboxylic acid (V/BP-MOF) was synthesized. Synthesized V/BP-MOF was introduced as a strong adsorbent of Congo Red (CR) and an effective agent in eliminating microbial species. In the investigation of CR absorption activity, several factors such as concentration of V/BP-MOF, pH, time, and temperature were investigated. Antimicrobial evaluations were carried out on Common bacterial strains in wastewater and values of MIC (minimum inhibitory concentration) and MBC (Minimum Bactericidal Concentration) were reported. The V/BP-MOF was confirmed and characterized by EA, EDS, EDS mapping, FT-IR, XRD, TGA, BET, SEM, and TEM. In checking the characteristics of V/BP-MOF, size, specific surface area, and thermal stability were obtained, respectively, 68 nm, 325 m2/g, and 320°C. The highest adsorption of CR, at 94%, was obtained at natural pH, ambient temperature, and after 150 min. In kinetic studies, a correlation coefficient of 0.99 was observed with the pseudo-second-order kinetic model, while in isotherm studies, a correlation coefficient of 0.97 was observed with the Freundlich isotherm model. In the biological evaluations, the best inhibition was against Escherichia coli, and MIC and MBC were observed as 4 μg/mL and 2 μg/mL, respectively. As a general result, V/BP-MOF can be introduced as a potent absorbent agent of CR dye and antimicrobial properties. Therefore, the compound synthesized in this study can be introduced as a suitable option for the wastewater treatment industry, with multiple capabilities including the removal of chemical pollutants and pathogenic agents.

Enhanced nitrate reduction in hypotrophic waters with integrated photocatalysis and biodegradation

Addressing nitrate contamination in water bodies is a critical environmental challenge, and Intimately Coupling Photocatalysis and Biodegradation (ICPB) presents a promising solution. However, there is still debate about the effectiveness of ICPB in reducing nitrate under hypotrophic conditions. Further research is needed to understand its microbial metabolic mechanism and the functional changes in bacterial structure. Here we explored microbial metabolic mechanisms and changes in bacterial structure in ICPB reactors integrating a meticulously screened TiO2/g-C3N4 photocatalyst with biofilm. We achieved a 26.3% increase in nitrate reduction using 12.2% less organic carbon compared to traditional biodegradation methods. Metagenomic analysis of the microbial communities in ICPB reactors revealed evolving metabolic pathways conducive to nitrate reduction. This research not only elucidates the photocatalytic mechanism behind nitrate reduction in hypotrophic conditions but also provides genomic insights that pave the way for alternative approaches in water remediation technologies.

Synergistic molecular mechanism of degradation in dye wastewater by Rhodopseudomonas palustris intimately coupled carbon nanotube - Silver modified titanium dioxide photocatalytic composite with sodium alginate

The intimately coupled photocatalysis and biodegradation (ICPB), which combined the advantages of high oxidation capacity of photocatalysis and high mineralization rate of biodegradation, has demonstrated excellent removal performance in the degradation of azo dyes with highly toxic, refractory, mutagenic and carcinogenic. In order to explore the metagenomics mechanism of the ICPB system, a novel ICPB was prepared by coupling Rhodopseudomonas palustris (R. Palustris), carbon nanotube - silver modified titanium dioxide photocatalytic composite (CNT-Ag -TiO2, CAT) and sodium alginate (SA) (R. palustris/CAT@SA, R-CAT). Metagenomics sequencing was used to investigate the molecular mechanism of adaptation and degradation of dyes by photosynthetic microorganisms and the adaptive and synergistic interaction between photosynthetic microorganisms and photocatalyst. Experiments on the adaptability and degradability of photosynthetic microorganisms have proved that low concentration azo dyes could be utilized as carbon sources for growth of photosynthetic microorganisms. Metagenomics sequencing revealed that R. palustris was the main degrading bacterium in photosynthetic microorganisms and the functional genes related to carbohydrate metabolism, biological regulation and catalytic activity were abundant. It was found that the addition of photocatalyst significantly up-regulated the functional genes related to the catabolic process, electron transport, oxidoreductase activity and superoxide metabolism of organic matter in the photosynthetic microorganisms. Moreover, many key gene such as alpha-amylase, 1-acyl-sn-glycerol-3-phosphate acyltransferase, aldehyde dehydrogenase enrichment in microbial basal metabolism, such as enoyl-CoA hydratase, malate dehydrogenase, glutathione S-transferase enrichment in degrading azo dyes and electron transport, and many key gene such as undecaprenyl-diphosphatase, carbon storage regulator, DNA ligase enrichment in response to dyes and photocatalysts were discovered. These findings would contribute to a comprehensive understanding of the mechanism of degradation of dye wastewater by ICPB system, a series of genes was produced to adapt to environmental changes, and played synergistic role in terms of intermediate product degradation and electron transfer for degrading azo dyes. The photosynthetic microorganisms might be a promising microorganism for constructing ICPB system.

Laser-cum-KOH activation allows interfacial engineering of cardboard-derived carbon, tunable ionic states, and universal dye adsorption

In this study, we demonstrate the preparation of laser-cum KOH-activated porous carbon with tunable ionic states, unique surface chemistry, and physical texture from renewable and environmentally friendly precursors (waste cardboard boxes). The adsorption performance of the engineered adsorbents is examined on the adsorption of methyl blue (MB, anionic) and methylene blue (MeB, cationic). The adsorption mechanism was determined using detailed batch adsorption, and the MB was adsorbed via the formation of ternary complexes, whereas the MeB was adsorbed through cation-π interaction. Furthermore, the non-activated laser-induced carbon (LIC100) and the KOH-activated carbon (KAC(L)) exhibit superior dye adsorption capacities of 9610 (MB) and 1882 mg g-1 (MeB), respectively. To the best of our knowledge, this is the highest ever reported at dye removal in the field of adsorptive dye removal. Langmuir isotherm model and pseudo-second-order are fitted well for both MB and MeB adsorption. Lastly, the carbons generated through this modern technique can be remodeled into a more secure device to obtain clean and microorganism-free water. This study showed the potential of laser-induced carbonization of KOH-activated substrate and provided unique insights into future development for universal dye adsorption and other possible applications.

Anoxygenic phototrophic purple non-sulfur bacteria: tool for bioremediation of hazardous environmental pollutants

The extraordinary metabolic flexibility of anoxygenic phototrophic purple non-sulfur bacteria (PNSB) has been exploited in the development of various biotechnological applications, such as wastewater treatment, biohydrogen production, improvement of soil fertility and plant growth, and recovery of high-value compounds. These versatile microorganisms can also be employed for the efficient bioremediation of hazardous inorganic and organic pollutants from contaminated environments. Certain members of PNSB, especially strains of Rhodobacter sphaeroides and Rhodopseudomonas palustris, exhibit efficient remediation of several toxic and carcinogenic heavy metals and metalloids, such as arsenic, cadmium, chromium, and lead. PNSB are also known to utilize diverse biomass-derived lignocellulosic organic compounds and xenobiotics. Although biodegradation of some substituted aromatic compounds by PNSB has been established, available information on the involvement of PNSB in the biodegradation of toxic organic pollutants is limited. In this review, we present advancements in the field of PNSB-based bioremediation of heavy metals and organic pollutants. Furthermore, we highlight that the potential role of PNSB as a promising bioremediation tool remains largely unexplored. Thus, this review emphasizes the necessity of investing extensive research efforts in the development of PNSB-based bioremediation technology.

Bioremediation of Azo Dye Brown 703 by Pseudomonas aeruginosa: An Effective Treatment Technique for Dye-Polluted Wastewater

Dye-polluted wastewater poses a serious threat to humans’, animals’ and plants’ health, and to avoid these health risks in the future, the treatment of wastewater containing dyes is necessary before its release to environment. Herein, a biological approach is used; the textile azo dye brown 703 is degraded utilizing Pseudomonas aeruginosa. The bacterial strain was isolated from textile wastewater dumping sites in Mingora, Swat. The optimization for bacterial degradation was carried out on the nutrient broth medium, which was then subjected to a variety of environmental physicochemical conditions and nutritional source supplementation before being tested. Under micro-aerophilic circumstances, the maximum decolorization and degradation of dye occurred at a 20 ppm dye concentration within 3 days of incubation at a neutral pH and 38 °C. The decrease in the intensity of the absorbance peak in the UV–Vis spectrum was used to measure the extent of decolorization. Initially, 15 bacterial strains were isolated from the textile effluent. Out of these strains, Pseudomonas aeruginosa was found to be the most potent degrading bacteria, with a degradation extent of around 71.36% at optimum conditions. The appearance and disappearance of some new peaks in the FT-IR analysis after the degradation of brown 703 showed that the dye was degraded by Pseudomonas aeruginosa. The GC–MS analysis performed helped in identifying the degraded compounds of azo dye that were utilized in illustrating the under-study process of brown 703 degradation. The biodegradation brought about by Pseudomonas aeruginosa can be employed successfully in the future as an eco-friendly approach with far reaching results.

ZnWO4 nanorod-colloidal SnO2 quantum dots core@shell heterostructures: Efficient solar-light-driven photocatalytic degradation of tetracycline

Zinc tungsten oxide (ZW) and colloidal SnO₂ quantum dots (CS) were synthesized individually by hydrothermal and wet chemical methods. ZW-CS core@shell nanorods were prepared using a sonochemical method for the enhanced photocatalytic activity of tetracycline (TC) degradation. ZW-CS core@shell nanorods were systematically characterized by structural, morphological mapping and optical techniques. All characterization techniques were synchronized to confirm the construction of core@shell nanorods. Optical absorption studies indicate an increased light-capturing efficiency along with a reduced bandgap from 3.56 to 3.23 eV, which is further supported by photoluminescence. Mapping analysis from SEM and HR-TEM evidence the presence of elements as well as a core@shell nanostructure. The optimized sample of ZW-CS 1.0 shows improved photocatalytic degradation of TC under stimulated solar light. The TC degradation efficiency by ZW-CS 1.0 core@shell nanorods was about 97% within 2 h. The formation of core@shell nanorod structure might be the reason for the better photocatalytic tetracycline degradation performance.

Fabrication of an intimately coupled photocatalysis and biofilm system for removing sulfamethoxazole from wastewater: Effectiveness, degradation pathway and microbial community analysis

Sulfamethoxazole (SMX) is an extensively applied antibiotic frequently detected in municipal wastewater, which cannot be efficiently removed by conventional biological wastewater processes. In this work, an intimately coupled photocatalysis and biodegradation (ICPB) system consisting of Fe³⁺-doped graphitic carbon nitride photocatalyst and biofilm carriers was fabricated to remove SMX. The results of wastewater treatment experiments showed that 81.2 ± 2.1% of SMX was removed in the ICPB system during the 12 h, while only 23.7 ± 4.0% was removed in the biofilm system within the same time. In the ICPB system, photocatalysis played a key role in removing SMX by producing hydroxyl radicals and superoxide radicals. Besides, the synergism between photocatalysis and biodegradation enhanced the mineralization of SMX. To understand the degradation process of SMX, nine degradation products and possible degradation pathways of SMX were analyzed. The results of high throughput sequencing showed that the diversity, abundance, and structure of the biofilm microbial community remained stable in the ICPB system at the end of the experiments, which suggested that microorganisms had accommodated to the environment of the ICPB system. This study could provide insights into the application of the ICPB system in treating antibiotic-contaminated wastewater.

Progresses in lignin, cellulose, starch, chitosan, chitin, alginate, and gum/carbon nanotube (nano)composites for environmental applications: A review

Water sources are becoming increasingly scarce, and they are contaminated by industrial, residential, and agricultural waste-derived organic and inorganic contaminants. These contaminants may pollute the air, water, and soil in addition to invading the ecosystem. Because carbon nanotubes (CNTs) can undergo surface modification, they can combine with other substances to create nanocomposites (NCs), including biopolymers, metal nanoparticles, proteins, and metal oxides. Furthermore, biopolymers are significant classes of organic materials that are widely used for various applications. They have drawn attention due to their benefits such as environmental friendliness, availability, biocompatibility, safety, etc. As a result, the synthesis of a composite made of CNT and biopolymers can be very effective for a variety of applications, especially those involving the environment. In this review, we reported environmental applications (including removal of dyes, nitro compounds, hazardous materialsو toxic ions, etc.) of composites made of CNT and biopolymers such as lignin, cellulose, starch, chitosan, chitin, alginate, and gum. Also, the effect of different factors such as the medium pH, the pollutant concentration, temperature, and contact time on the adsorption capacity (AC) and the catalytic activity of the composite in the reduction or degradation of various pollutants has been systematically explained.

Enhanced antibiotic wastewater degradation by intimately coupled B-Bi3O4Cl photocatalysis and biodegradation reactor: Elucidating degradation principle systematically

Intimately coupled photocatalysis and biodegradation (ICPB) is an emerging technology that has potential applications in the degradation of bio-recalcitrant pollutants. However, the interaction principles between photocatalysts and biofilms in ICPB have not been well developed. This article covers a cooperative degradation scheme coupling photocatalysis and biodegradation for efficient degradation and mineralization of ciprofloxacin (CIP) using ICPB with B-doped Bi₃O₄Cl as the photocatalyst. In consequence, a removal rate of ∼95 % is reached after 40 d. The biofilms inside the ICPB carriers can mineralize the photocatalytic products, thus improving the removal rate of total organic carbon (TOC) by more than 20 %. Interior biofilms are not destroyed by CIP or photocatalysis, and they adapt to ICPB of CIP by enriching in Pseudoxanthomonas, Ferruginibacter, Clostridium, Stenotrophomonas and Comamonas and reconstructing their microbial communities using energy produced by the light-excited photoelectrons. Furthermore, this research gives new opinion into the degradation principles of the ICPB system.

Research progresses on the application of perovskite in adsorption and photocatalytic removal of water pollutants

The problem of global water pollution and scarcity of water resources is becoming increasingly serious. Multifunctional perovskites can well drive adsorption and photocatalytic reactions to remove water pollutants. There are many advantages of perovskites, such as abundant oxygen vacancies, easily tunable structural morphology, stable crystal state, highly active metal sites, and a wide photo response range. However, there are few reviews on the simultaneous application of perovskite to adsorption and photocatalytic removal of water pollutants. Thus, this paper discusses the preparation methods of perovskite, the factors affecting the adsorption of water environmental pollutants by perovskite, and the factors affecting perovskite photocatalytic water pollutants. The particle size, specific surface area, oxygen vacancies, electron-hole trapping agents, potentials of the valence band, and conduction band in perovskites are significant influencing factors for adsorption and photocatalysis. Strategies for improving the performance of perovskites in the fields of adsorption and photocatalysis are discussed. The adsorption behaviors and catalytic mechanisms are also investigated, including adsorption kinetics and thermodynamics, electrostatic interaction, ion exchange, chemical bonding, and photocatalytic mechanism. It summarizes the removal of water pollutants by using perovskites. It provides the design of perovskites as high-efficiency adsorbents and catalysts for developing new technologies.

Historical development and prospect of intimately coupling photocatalysis and biological technology for pollutant treatment in sewage: A review

Through the synergistic effect of photocatalysis and biodegradation, intimately coupling photocatalysis and biological (ICPB) technology could improve the removal rate and mineralization rate of refractory pollutants and reduce the toxicity of intermediate products. ICPB system was characterized with the advantages of simple operation, low energy consumption and high treatment efficiency. As a new sewage treatment technology, ICPB system has shown great potential in the treatment of refractory pollutants, and has been widely concerned. In this study, the research progress of photocatalyst, carrier and biofilm in ICPB system were discussed, and the degradation mechanism was introduced. The shortcomings of the current ICPB system were pointed out, and the possible research directions of ICPB in the future were proposed. This review aimed to deepen the understanding of ICPB technology and promoted the further development of ICPB technology in the treatment of refractory pollutants.