Mineralization Efficiency Research Articles

Treatment of VOCs with a wet scrubbing – catalytic ozonation process: Efficiency, mechanism and pilot-scale application

A wet scrubbing – catalytic ozonation (WCO) process with activated carbon (AC) loaded MnOx (MnOx/AC) as the catalyst was developed, based on volatile organic compounds (VOCs) can be efficiently removed. The mineralization efficiency, degradation pathway and mechanism, and effects of the process operating parameters were investigated in detail using toluene as the target pollutant. The results show that the average removal efficiency of toluene reached 71.82 % within 90 min under optimal conditions (CToluene = 100 mg/m3; CO3 = 1 mg/L; catalyst loading = 5 g/L; pH = 7; gas flow = 500 mL/min), which outperformed that of the gaseous system. Quenching experiments and electron spin resonance spectroscopy indicate that OH and O2− are the two main reactive oxygen species (ROSs) in the system, which facilitate the opening of the benzene ring and significantly reduce by-products. The intermediates of toluene degradation were identified by proton-transfer reaction time-of-flight mass spectroscopy (PTR-TOF-MS). The results indicate that most of the intermediates generated in the system are captured in water rather than being emitted into the atmosphere. In the pilot-scale experiments, the WCO process exhibited a stable VOC removal efficiency (≥61.05 %) for 10 d in the treatment of actual low-concentration VOCs. Therefore, in this study, an effective process for the removal of low-concentration VOCs is proposed, which can be used for multiple VOC treatments.

Photo-electrocatalytic degradation of remdesivir from aqueous solutions using Ni-doped ZnO nanocomposite: Kinetic, degradation pathway, toxicity reduction and reusability

Currently, there has been increasing interest in developing active photocatalysts for the treatment of wastewaters. In this study, Nickel (Ni)-doped Zinc oxide on a fluorine tin oxide (ZnO/FTO) was synthesized and utilized as an electrocatalyst for efficient degradation and mineralization of remdesivir (REMD). Ni-ZnO/FTO electrode was characterized using XRD, SEM, EDX, LSV, and DRS analyses. The influence of operational parameters on the degradation efficiency procedure was explored in a batch photo-reactor and their optimum values were selected. At optimized conditions (e.g. initial REMD concentration = 1 mg/L, electrolyte concentration = 0.1 g/L, current intensity = 0.03 A, and pH = 7), within 2 h under UV-A, the removal efficiency of initial REMD concentration was 92 %, whereas TOC and COD removal efficiency were found as 80.1 % and 69.5 %, respectively. The assessment of the degradation rate within 2 h indicates that REMD degradation obeyed first order kinetic model. Additionally, in the comparison of degradation and mineralization efficiency of electrolysis, photolysis and photocatalytic and photoelectrocatalysis (PECP) processes for REMD removal, PECP gave the highest efficiency. The toxicity evaluations showed that the toxicity of solutions treated by the proposed PEC process significantly decreased in comparison with untreated controls. Based on reusability investigations, Ni-ZnO/FTO can be reused for at least five repetitive times with suitable efficiency. Moreover, by taking into account all results, it was concluded that the affordability, high potentiality, and well regenerability of Ni-ZnO/FTO make it an attractive electrocatalyst in terms of drug-containing wastewater treatment.

Controllable Synthesis, Formation Mechanism, and Photocatalytic Activity of Tellurium with Various Nanostructures.

Telluriums (Te) with various nanostructures, including particles, wires, and sheets, are controllably synthesized by adjusting the content of polyvinylpyrrolidone (PVP) in a facile solvothermal reaction. Te nanostructures all have complete grain sizes with excellent crystallinity and mesopore structures. Further, the formation mechanisms of Te nanostructures are proposed to be that the primary nuclei of Te are released from the reduction of TeO32- using N2H4·H2O, and then grow into various nanostructures depending on the different content of PVP. These nanostructures of Te all exhibit the photocatalytic activities for the degradation of MB and H2 production under visible light irradiation, especially Te nanosheets, which have the highest efficiencies of degradation (99.8%) and mineralization (65.5%) at 120 min. In addition, compared with pure Te nanosheets, the rate of H2 production increases from 412 to 795 μmol∙h-1∙g-1 after the introduction of Pt, which increases the output by nearly two times. The above investigations indicate that Te with various nanostructures is a potential photocatalyst in the field of degradation of organic pollutants and H2 fuel cells.

Sweety, salty, sour, and romantic biochar-supported ZnO: highly active composite catalysts for environmental remediation

AbstractThe present work focuses on valorizing the various biochar supports of nano-catalysts and investigates the effect of the type of the initial biomass on the deposition and salient physico-chemical features of the zinc oxide (ZnO) nanoparticles. In this regard, we have used four different biomasses, namely, sugarcane bagasse (Saccharum officinarum), algae (Phaeophyta), mandarin orange peels (Citrus reticulata), and China rose petals (Rosa chinensis) as sources of biochar. Their wet impregnation with zinc acetate was followed by pyrolysis at 500 °C. It led to biochar (nicknamed “sweety,” “salty,” “sour,” and “romantic” biochar, respectively) loaded with very well dispersed, 20–360 nm-sized (mostly) ZnO nanoparticles. Interestingly, depending on the type of biomass used, the size, shape (quartz-like, semi-spherical, spherical, semi-cauliflower, needle or rod-like), and degree of crystallinity of ZnO nanoparticles (hexagonal crystal system) vary, in spite of all other synthesis parameters being similar. Nanoparticle-induced graphitization and crystallization of biochar have been also observed by Raman spectroscopy. The malachite green dye mineralization efficiency in the presence of H2O2 and different biochar-supported ZnO nanocatalysts was 15.1%, 46.3%, 99.9%, 67.9%, and 66.4% for H2O2, china rose petals, algae, mandarin peels, and sugarcane bagasse-supported ZnO catalyst in the presence of H2O2, respectively. Malachite green removal fits in very well with a pseudo-first-order kinetic model with R2 = 0.9701 (at algae biochar-ZnO). 6.6 times enhancement in the mineralization efficiency is observed as compared to just H2O2. The recyclability test of algae biochar impregnated with ZnO after 5 cycles indicates the mineralization efficiency levels up to 81.4%. Beyond these scientific results, this work is based on the principle of biomass waste valorization for sustainable development and circular economy, on the one hand, and addresses the UN Sustainable Development Goals 6, 13, and 14, on the other hand. It is also very clear that biochar is the new romance in the field of materials science and for sustainable future. Graphical Abstract

Application of persulfate-assisted graphitic carbon, derived through pyrolysis of waste biomass, driven by visible light, for the removal of tetracycline from water: Mechanisms and performance influencing parameters

Sulfate radical based advanced oxidation process by using carbon-based materials has attracted widespread attention for removal of emerging contaminants in water. This paper reports the study on the efficacy of visible light activated persulfate (PS) – graphitic carbon (GC) system for the removal of tetracycline (TC) from water . Here GCs from residual agricultural biomass were synthesized via a facile and chemical-free pyrolysis route, and their characteristics were analyzed under varying thermal conditions, viz. temperature (550–950 °C) and heating rate (2.5–10 °C min−1). The GCs at high pyrolysis temperatures (> 700 °C) revealed graphitic and condensed aromatic carbon networks with enhanced textural properties, facilitating electron-mediated reactions through interconnected morphology. The methodology is derived from the research that shows certain pyrolysis derived carbon products are known to have transient photocurrent response, indicating semiconductor properties. Here, the visible light-driven GC/PS (950 °C, 5 °C min−1) system resulted in high TC removal efficiency of 91.23% within 180 min compared to other PS/GCs prepred under different conditions. The mass spectroscopy data shows that the GC/PS system successfully degraded TC into simpler products and achieved the highest mineralization efficiency of about 65.43 ± 3.62%. The radical scavenging experiments revealed that 1O2 and •OH were the dominant reactive oxygen species suppressing degradation of TC by 13% and 9%, respectively. It can be surmised that both radical and non-radical pathways facilitate TC degradation via dehydration, demethylation and oxidation of aromatic rings- due to both catalytic and physico-chemical properties of GC/PS .

Mechanism and performance evaluation of spent-coffee grounds-derived nanocomposite materials for highly efficient photocatalytic degradation of organic pollutant

The study demonstrates a facile and environmentally friendly method for synthesizing crystalline TiO2 nanoparticles on the surface of hydrochar generated from readily available biomass waste, i.e., spent coffee grounds (SCGs), using a simple sol–gel process. The hydrochar served as a support for TiO2, reducing the rate at which electrons and holes recombine during photocatalysis, thereby facilitating the effective binding of TiO2, enhancing its adsorption capacity, and the convenient separation of the photocatalyst after usage. The materials were tested in the photocatalytic degradation of an organic pollutant, methylene blue (MB) dye. TiO2-hydrochar obtained at 210 ⁰C has the best performance, giving a degradation efficiency of 98.5 % and a mineralization efficiency of 87.1 % in 90 min at neutral pH. Radical trapping experiments showed O2.-andh+ being the dominant species, followed by HO.. Besides, it showed superior stability with an activity loss of ∼ 9.2 % after five runs. The superior performance of the HCT210 was ascribed to the enhanced interfacial charge transfer kinetics between the TiO2 and hydrochar through Ti-O-C bond formation, better light absorption, and the high surface area of the materials. Performance metrics show that synthesized nanocomposites are promising photocatalysts, providing a biomass-assisted method for robust photocatalytic wastewater treatment.

Coupled Photocatalysis and Microalgal–Bacterial Synergy System for Continuously Treating Aquaculture Wastewater Containing Real Phthalate Esters

We developed a system combining visible-light photocatalysis with biological treatment for the continuous removal of phthalate esters (PAEs) from both synthetic and real aquaculture wastewater. We investigated the effects of different operating factors, including the coexistence of glucose or PAEs, on individual PAE removal by using a photobiological system (PBS). In wastewater containing a mixture of PAEs, that is, containing di-(2-ethylhexyl)phthalate (DEHP), dibutyl phthalate (DBP), and dimethyl phthalate (DMP), a coimmobilized bioreactor system comprising the bacterium Pseudomonas putida and the microalga Chlorella vulgaris demonstrated a higher removal efficiency than immobilized P. putida alone or a coculture of immobilized P. putida and suspended C. vulgaris did. The PBS employed for the continuous treatment of real aquaculture wastewater containing DEHP (0.62 ± 0.05 mg/L), DBP (8.7 ± 0.9 mg/L), and DMP (17.4 ± 1.5 mg/L) achieved at least 99.5% PAE removal and 99.2% mineralization efficiency under optimal operating conditions. After 42 days of treatment, inoculated Pseudomonas (98.12%) remained the predominant genus in the bioreactor. The results reveal that the symbiotic microalgal–bacterial system is a feasible alternative to a pure P. putida immobilized bioreactor for reducing CO2 emissions from mineralized PAEs through microalgal activity.

Long-term stable and efficient degradation of ornidazole with minimized by-product formation by a biological sulfidogenic process based on elemental sulfur

Conventional biological treatment processes cannot efficiently and completely degrade nitroimidazole antibiotics, due to the formation of highly antibacterial and carcinogenic nitroreduction by-products. This study investigated the removal of a typical nitroimidazole antibiotic (ornidazole) during wastewater treatment by a biological sulfidogenic process based on elemental sulfur (S0-BSP). Efficient and stable ornidazole degradation and organic carbon mineralization were simultaneously achieved by the S0-BSP in a 798-day bench-scale trial. Over 99.8 % of ornidazole (200‒500 μg/L) was removed with the removal rates of up to 0.59 g/(m3·d). Meanwhile, the efficiencies of organic carbon mineralization and sulfide production were hardly impacted by the dosed ornidazole, and their rates were maintained at 0.15 kg C/(m3·d) and 0.49 kg S/(m3·d), respectively. The genera associated with ornidazole degradation were identified (e.g., Sedimentibacter, Trichococcus, and Longilinea), and their abundances increased significantly. Microbial degradation of ornidazole proceeded by several functional genes, such as dehalogenases, cysteine synthase, and dioxygenases, mainly through dechlorination, denitration, N-heterocyclic ring cleavage, and oxidation. More importantly, the nucleophilic substitution of nitro group mediated by in-situ formed reducing sulfur species (e.g., sulfide, polysulfides, and cysteine hydropolysulfides), instead of nitroreduction, enhanced the complete ornidazole degradation and minimized the formation of carcinogenic and antibacterial nitroreduction by-products. The findings suggest that S0-BSP can be a promising approach to treat wastewater containing multiple contaminants, such as emerging organic pollutants, organic carbon, nitrate, and heavy metals.

Mineralization characteristics and behavior of polyethylene microplastics through ozone-based treatment

The elimination of microplastics (MPs) has become an urgent issue due to their large quantities and imperfect treatment technologies. In this work, polyethylene (PE), which is ubiquitous in the environment, was selected to study its removal by ozone-based treatment. Catalysts including α-MnO2 and α-FeOOH were synthesized for catalytic ozonation to improve efficiency. The study focused on simulating the conversion of CO2 in the off-gas via the detection of inorganic carbon produced. The morphology and structure of the remaining PE MPs were characterized using scanning electron microscope and Fourier-transform infrared spectroscopy-attenuated total reflection. Our results confirmed that fragmentation and oxidation occurred in the remaining PE MPs, which enhanced the adsorption capacity of ofloxacin (OF). Besides, the 20 mM α-FeOOH could better improve the mineralization efficiency by 3.27 folds with more production of •OH (1.09*10−12 M). Moreover, possible products identified by liquid chromatography-time-of-flight mass spectrometer confirmed the decomposition of main chains of MPs into low-molecular-weight organic compounds with functional groups such as C–OH, C–O–C, and CO. The finding that photoaged PE MPs could be efficiently mineralized under the attack of O3/•OH provides a solid foundation for the removal of natural MPs in the environment.

Water hyacinth derived hierarchical porous biochar absorbent: Ideal peroxydisulfate activator for efficient phenol degradation via an electron-transfer pathway

In this paper, a facile hydrothermal pretreatment and molten salt activation route was presented for preparing a self-doped porous biochar (HMBC) from a nitrogenous biomass precursor of water hyacinth. With an ultrahigh specific surface area (2240 m2 g−1), well-developed hierarchical porous structure, created internal structural defects and doped surface functionalities, HMBC exhibited an excellent adsorption performance and catalytic activity for phenol removal via peroxydisulfate (PDS) activation. Specifically, the porous structure promoted the adsorption of PDS on HMBC, forming a highly active HMBC/PDS* complex and thereby increasing the oxidation potential of the system. Meanwhile, the carbon defective structure, graphitic N and CO groups enhanced the electron transfer process, favoring the HMBC/PDS system to catalyze phenol oxidation via an electron transfer dominated pathway. Thus, the system degraded phenol effectively with an ultralow activation energy of 4.9 kJ mol−1 and a remarkable oxidant utilization efficiency of 8.2 mol mol-oxidant−1 h−1 g−1. More importantly, the system exhibited excellent resistance to water quality and good adaptability for decontaminating different organic pollutants with satisfactory mineralization efficiency. This study offers valuable insights into the rational designing of a low-cost biochar catalyst for efficient PDS activation towards organic wastewater remediation.

Compost of peanuts residue and rice straw compost on soil Nitrogen forms and upland rice yield

<p>This study provides an innovation in making compost from rice straw (low quality) mixed with peanut residue (high quality) to improve the quality of rice straw compost. The purpose of this research was to discover the optimum composition of a mixture of peanut residue and straw for mineralization, absorption, and Nitrogen Use Efficiency (NUE) and its effect on upland rice plants. The study was conducted in three stages. The first stage determined the quality of five compost mixtures: C1, C2, C3, C4, and C5. The second phase of testing for cumulative N minerals was performed after 1, 2, 4, and 8 weeks of incubation. The third stage examined the impact of the compost mixture on the growth and yield of upland rice in comparison with two treatments, namely the control and NPK fertilizer. The results showed a similarity in the forms of mineralization, where the cumulative N mineral increased with the addition of peanut residue to the compost mixture. The use of a mixture of peanut residue and rice straw compost increased net mineralization by 37.27% (C5) to 59.48% (C1), N uptake by 49.19% (C5) to 62.95% (C3), and NUE by 15.04% (C4) to 51.48% (C3). A strong relationship was detected between the quality of the compost and the forms of N in the soil, particularly the nitrate content, total N minerals, and N microbial biomass, with correlation coefficients of 0.92, 0.88, and 0.94, respectively. A strong to very strong relationship was detected between N form and N uptake (r = 0.84), plant height (r = 0.79), number of tillers (r = 0.78), yield of rice plants (r = 0.93 (plant total dry weight), and r = 0.76 (grain weight). The optimum N uptake, NUE, and yield of upland rice were shown by C3 treatment of 405.28 mg pot<sup>-1</sup>, 42.21%, and 6.19 tons ha<sup>-1</sup>, respectively.</p>

Intervention timing of H* and •OH determines the catalytical degradation of tribromophenol by palladium(II) doped green rust in redox-alternating environments

Atomic hydrogen (H*) and hydroxyl radicals (•OH) can synergistically realize efficient mineralization of halogenated organic pollutants, but it requires an electrocatalytic or photoelectrocatalytic system. In this work, we developed a simple synergetic reduction-oxidation system for the degradation of tribromophenol (TBP) using Pd(II) doped green rust (GR). GR reduced Pd(II) to Pd(0) which catalyzed H2O/H+ to produce H* . H* completely reduced TBP to phenol. Meanwhile, excess H* involved in the generation of •OH under oxic conditions. The synergistic involvement of H* and •OH realized the mineralization of TBP, which could not be achieved by H* or •OH alone. Furthermore, the diffusion rate of dioxygen into solution determined sequential or synchronous involvement of H* and •OH, which significantly affected the mineralization efficiency of TBP. We proposed that the most efficient way to mineralize TBP was initiating H*-involved nucleophilic hydrodebromination first and then initiating •OH-involved electrophilic oxidation.

Construction of a novel double S-scheme heterojunction CeO2/g-C3N4/Bi2O4 for significantly boosted degradation of tetracycline: Insight into the dual charge transfer mode

Constructing dual S-scheme heterojunction, as one kind of new strategy for the reinforcement of photocatalytic property, shows significant advantages in facilitating the migration of photoinduced charges and achieving high redox potentials. Herein, a novel double S-scheme heterojunction CeO2/g-C3N4/Bi2O4 was designed and synthesized successfully. The photodegradation of tetracycline (TC) over CeO2/g-C3N4/Bi2O4 was carried out under the irradiation of visible light. The double S-scheme interfacial charge transmission mode of CeO2/g-C3N4/Bi2O4 was investigated according to Fermi level, band structure, and the in-depth analysis of in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and electron spin resonance (ESR) spectra. The CeO2/g-C3N4/Bi2O4 exhibits excellent catalytic activity with a high TC removal efficiency of 94 % and a remarkable mineralization efficiency of 51 %. The rate constant (0.05811 min−1) of TC degradation for CeO2/g-C3N4/Bi2O4 is 12.9, 7.8, 4.3, 2.2, and 3.1 times those for g-C3N4, CeO2, Bi2O4, g-C3N4/Bi2O4 and CeO2/g-C3N4, separately. The prominently boosted activity may be due to two factors. Firstly, the successful creation of the double S-scheme electron migration channel greatly boosts the transmission of photogenerated carriers, represses the recombination of electrons with holes, and ensures the strongest redox potential of CeO2/g-C3N4/Bi2O4. Secondly, the introduction of Bi2O4 with excellent visible-light absorption broadens the optical absorption region of CeO2/g-C3N4/Bi2O4. Additionally, the influence of the typical environmental factors (pH, inorganic anions, cations, and natural humus) on the photodegradation of TC was explored. The three probable pathways for TC degradation were inferred via analyzing intermediates. The current work offers a novel outlook for enhancing the activity of ternary heterojunction photocatalysts applied in environmental restoration.

Residue recycling options and their implications for sustainable nitrogen management in rice–wheat agroecosystems

BackgroundIn the Indo-Gangetic Plain, rice–wheat is the most extensively practiced crop rotation. The escalating issue of crop residue burning, particularly rice straw, and the necessity to lower the exorbitant expenses associated with fertilizer inputs stand out as significant challenges for farmers in the region. A well-suited integrated nutrient management (INM) strategy that focuses on recycling crop residues can serve as a solution to address these issues. Such a strategy not only mitigates air pollution resulting from residue burning but also helps combat water pollution due to nitrate losses from agroecosystems. Field experiments were used to evaluate the suitability of eight INM-modules that included various combinations of inorganic fertilizer rates (50%, 100%, 150% of recommended dose), crop residues (wheat and rice stubble retention at 30 cm standing stubble equivalent to 1/3 the straw yield), rice straw compost (RSC), farmyard manure (FYM), and green manuring (GM), compared to 100% recommended dose of fertilizers (F) and no fertilizer application.ResultsThere was a considerable improvement in nitrogen mineralization, grain yields, and nitrogen use efficiency under GM + RSC-F50 and GM + FYM-F50. These INM modules would permit a 50% reduction in the use of chemical fertilizers. There was a little yield penalty with in situ rice residue incorporation at 100% F; however, this could be overcome with 150% F fertilizer application. In situ retention of wheat straw with a full application of fertilizer resulted in steadily rising crop yields over time. Changes in the redox potential, soil pH, and soil organic carbon best accounted for the observed trajectories in nitrogen use efficiency.ConclusionThe most promising INM modules for adoption by farmers in the Indo-Gangetic Plain to judiciously use crop residues and curtail chemical fertilizer inputs are green manuring with Sesbania aculeata + rice straw compost at 5 t ha−1 + only 50% of recommended dose of fertilizers (GM + RSC-F50), and green manuring with Sesbania aculeata + farmyard manure at 5 t ha−1 + only 50% of recommended dose of fertilizers (GM + FYM-F50). Sole incorporation of crop residues without nitrogen augmentation from other sources might not help curtail chemical fertilizer use. Composting rice straw, which otherwise is widely burnt, proved a useful nitrogen source and a vital component of INM. Waste rice straw composting at the community scale and its application as a nutrient source can help achieve sustainable nitrogen management in the agroecosystems of Indo-Gangetic Plain.

Single-step integrated CO2 absorption and mineralization using fly ash coupled mixed amine solution: Mineralization performance and reaction kinetics

Single-step integrated CO2 absorption and mineralization (IAM) using fly ash and mixed amine can reduce high energy consumption of absorbent regeneration while enabling the treatment of solid waste, however, the mineralization performance and kinetics are still unclear. This study adopted monoethanolamine (MEA)/N-Methyldiethanolamine (MDEA) mixed amine solution (MAS) as CO2 absorbent and fly ash as mineralizing materials to complete the IAM process in single-step, while realizing the regeneration of mixed amine. The mineralization performance was studied, and the reaction kinetics were analyzed by surface coverage model. The results demonstrated that fly ash effectively mineralized the absorbed CO2 in MAS and mixed amine regenerated. The mineralization efficiency reached maximum of 64.8 % at 40 °C, solid-liquid (S/L) ratio of 100 g/L, stirring rate of 500 r/min and 90 min, reaching 60.3 % after 10 cycles. The kinetic results demonstrated that surface coverage model exhibited excellent predictive capability for mineralization process (correlation coefficient (R2) > 0.99), with identification of surface reaction governed by calcium leaching as the primary rate-limiting factor. The regeneration of mixed amine was achieved by forming carbamate and protonated amine. The CO32−/HCO3− effectively reacted with the active Ca2+ ions in fly ash to realize mineralization, and the mineralization solid products was mainly CaCO3.

Boosting carrier separation over ultrathin g-C3N4 by f-ionic intercalation for improved photocatalytic activity

Reinforcing carrier separation is the key issue to improve the photocatalytic activity of graphitic carbon nitride (g-C3N4). Although tailoring layer dimension by exfoliation could shorten the diffusion paths, the transport of charge carriers between g-C3N4 adjacent layers still needs to conquer large resistance. Here, by virtue of gas-shocking triggered synthetic strategy, the F can be inserted into ultrathin g-C3N4 nanosheets via interlaminar C − F semi-ionic bond. Benefiting from the ultrathin 2D structure and interlayered F, the interlayered electronic channel has been established for F-intercalated g-C3N4 (xF-CNS) to promote charge cross the adjacent layers. All characterization results including XRD, FTIR, XPS and solid-state NMR approved the successful intercalation of F species in the interlayer of ultrathin g-C3N4 nanosheets, which induces improved light reception and accelerated photogenerated carriers transport-separation, thus achieving an improved photocatalytic mineralization efficiency of Ibuprofen. This work provides a new train of thoughts into modified ultrathin g-C3N4 materials to receive further improvement of photocatalytic efficiency.

Enhancement of water remediation by innovative photocatalytic luminous textiles reactor: Performance, kinetic modeling, and mechanistic insights

To address wastewater treatment, a photocatalytic process using luminous-textile has been proposed due to its high efficiency and non-toxicity. In the present work, the photodegradation of Ciprofloxacin (CIP) in the liquid phase was studied in a compact reactor with a luminous-textile catalyst in three different configurations: (i) “mono-face” (MF), (ii) “double-face” (DF) and (iii) “double-face without TiO2” (DF-without TiO2). The DF configuration exhibited the highest efficiency for CIP removal (99.7 %) and mineralization (40.3 %), followed by MF and DF-without TiO2. The DF luminous textiles, before and after CIP degradation, were characterized using scanning electron microscope and Fourier-transform infrared spectroscopy. The effect of operating parameters, such as CIP initial concentration (2–10 mg/L) and UV light intensity (0.08, 0.15 and 0.26 mW/cm2) on luminous-textile performance in terms of CIP degradation efficiency and mineralization yield was investigated. Good photocatalytic activity was found with 2 mg/L CIP initial concentration and 0.15 mW/cm2 UV light intensity. Moreover, the mineralization percentage reached 54.7 % and 61.2 % with the addition of 150 mg/L of H2O2 and 202 mg/L of PS, respectively. Additionally, the impact of radical scavengers was studied, proving that HO2˙, O2−˙, and especially radicals were the basic active species involved in CIP degradation mechanism.Furthermore, the degradation efficiency decreased from 99.7 % in ultra-pure water to 63.6 % in tap water (TW) and 46.1 % in synthetic water (SW), demonstrating the negative effects of nitrate, chloride, sulfate and bicarbonate ions on CIP degradation and mineralization efficiencies in TW and SW. In summary, the present study unraveled the mechanistic aspects of the excellent photocatalytic ability of the luminous-textile for the CIP mineralization.

“Floating Catalytic Foam” with prominent heat-induced convection for the effective photocatalytic removal of antibiotics

Immobilized photocatalysts represent a promising candidate for the wastewater treatments due to their good reusability, high stability and low eco-risk. Mass transfer within the immobilized catalytic bed is a crucial process that determines the contacting, adsorption, and degradation kinetics in the photodegradation. In this study, a floating catalytic foam (FCF) with a prominent pumping effect was designed to promote mass transfer. The polyurethane foam immobilized with rGO/TiO2/ultrathin-g-C3N4 photocatalyst (PRTCN) was prepared by a simple dip-coating and Uv-light aging process. It was found that the hydrophilic-hydrophobic interfaces could not only contribute to the floating of the catalyst but also establish a temperature gradient across the floating immobilized catalyst. In addition, the temperature gradient induced convection could serve as a built-in pump to effectively promote the diffusion and adsorption of target antibiotic molecules during the photocatalytic process. Therefore, the PRTCN demonstrated a high photodegradation and mineralization efficiency with excellent reusability and anti-interference capability. Moreover, the photodegradation mechanism and the intermediates’ toxicity of norfloxacin were detailly investigated by ultra-high resolution electrospray time-of-flight mass spectrometry, density functional theory simulation and ECOSAR estimation. This work proposed a facile and sustainable strategy to enhance the mass transfer problem on immobilized photocatalysts, which could promote the application of the immobilized photocatalysts in the real water-treatment scenarios.

Defects and plasma Ag co-modified S-scheme Ag/NVs-CN/Bi2O2-δCO3 heterojunction with multilevel charge transfer channels for boosting full-spectrum-driven degradation of antibiotics

The optimization of the photogenerated carriers’ relaxation dynamics process is critical for the improvement of photocatalytic performance. Herein, a ternary heterojunction with multilevel charge transfer channels was constructed by coupling plasma Ag, nitrogen vacancies carbon nitride (NVs-CN) and Bi2O2-δCO3. Ag/NVs-CN/Bi2O2-δCO3 heterojunction showed the S-scheme mechanism, which not only promoted the interfacial charge transfer, but also enhanced the driving force for redox reactions. The defect states induced by nitrogen vacancies and oxygen vacancies provided an additional energy level platforms for hot electrons relaxation of plasma Ag, resulting in the improved separation efficiency and utilization rate of the high-energy hot carriers. Hence, the prepared Ag/NVs-CN/Bi2-δO2CO3 heterojunction exhibited the markedly boosted full-spectrum driven catalytic activity for antibiotics degradation. 80.5% and 83.8% of tetracycline and ciprofloxacin could be mineralized into H2O and CO2 by the optimal heterojunction under visible light irradiation, and the corresponding mineralization efficiencies could reach 81.7% and 81.5% under NIR light irradiation. The proposed multichannel charge transfer mechanism provided a new insight into the design and preparation of high-active full-spectrum responsive heterojunction photocatalysts.

Hydrophobic fluorine-doped carbon-wrapped TiO2 particles as efficient and stable photocatalysts for gaseous toluene degradation

Moisture-resistant TiO2-based catalysts with high activity and stability are urgently needed to satisfy requirements for the treatment of volatile organic compounds (VOCs). In this work, a novel hydrophobic F-doped carbon-wrapped TiO2 catalyst (TiO2 @HFC) was synthesized by a facile method and used for the photocatalytic degradation of toluene. TiO2 @HFC displays significantly higher activity under UV/Vis irradiation than commercial P25 TiO2, and remains stable after six cycles. The removal efficiency of toluene was 81.7% after 210 min of reaction, corresponding to a mineralization efficiency of 74.5%. Benefiting from the hydrophobic F-doped carbon layer modification, the incorporation of F into TiO2 crystals, and increased Ti3+ content, TiO2 @HFC is characterized by efficient separation and utilization of photoexcited charge carriers, enhanced adsorption of toluene, and robust resistance towards water vapor. This work demonstrates the potential application of the TiO2-based photocatalyst to efficiently remove VOCs in a humid environment.