Higher Mineralization Efficiency Research Articles

Interface engineering of laminated redox-copolymers for electrochemical remediation of perfluoroalkyl substances

Redox polymers now show promise for selective removal of perfluoroalkyl substances from a complex aqueous matrix at high energy efficiency and no secondary pollution. However, self-agglomeration of redox polymers is a dominating barrier to constructing a low-cost, stable system in practical applications. Herein, we introduce polymer interface engineering strategy to enhance the activity of amine functionalities and nitrous oxide radicals in copolymers composed of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidin-1-oxyl and 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine. The grafted laminated redox polymer on multi-walled carbon nanotubes (termed MWCNT-g-P(TMPMA-co-TMA)) via free-radical polymerization demonstrated a 19.1–59.9 % increase in the electrosorption capacity with a maximum value (Qm) of 725.09 mg g−1 and a pseudo-first-order rate constant k1 = 1.46 min−1 and sustainable regeneration efficiency at ∼80 %. The core–shell structure of MWCNT-g-P(TMPMA-co-TMA) with a laminated redox polymer layer of ∼5 nm processed a low charge transfer resistance, which is expected to contribute to the enhanced capture performance and stability. An integrated system consisting of a MWCNT-g-P(TMPMA-co-TMA) electrode and a boron-doped diamond electrode can efficiently separate and degrade trace-concentration PFOA from industrial wastewater at high mineralization efficiency. This work provides insight into the design and optimization of redox active materials for water purification and beyond.

Efficient degradation of sulfadiazine by UV-triggered electron transfer on oxalic acid-functionalized corn straw biochar for activating peroxyacetic acid: Performance, mechanism, and theoretical calculation

A novel UV/oxalic acid functionalized corn straw biochar (OCBC)/peroxyacetic acid (PAA) system was built to degrade sulfadiazine from waters. 94.7 % of SDZ was removed within 30 min by UV/OCBC/PAA. The abundant surface functional groups and persistent free radicals (PFRs) on OCBC were responsible for these performances. Cyclic voltammetry (CV) and other characterization analysis revealed, under UV irradiation, the addition of OCBC served as electron donor, which might promote the reaction of electrons with PAA. The quenching and electron paramagnetic resonance (EPR) tests indicated that R-O•, 1O2 and •OH were generated. Theoretical calculations indicated sulfonamide bridge was vulnerable under the attacks of reactive species. In addition, high removal effect achieved by 5 reuse cycles and different real waters also suggested the sustainability of UV/OCBC/PAA. Overall, this study provided a feasible approach to remove SDZ with high mineralization efficiency, in addition to a potential strategy for resource utilization of corn straw.

Buffer-free ozone-ferrate(VI) systems for enhanced oxidation of electron-deficient contaminants: Synergistic enhancement effects, systematic toxicity assessment, and practical applications

The combination of ozone (O3) and ferrate (Fe(VI)) oxidation technology demonstrates substantial potential for practical applications, though it has been underreported, resulting in gaps in comprehensive activity assessments and thorough exploration of its mechanisms. This study reveals that the previous use of a borate buffer solution obscured certain synergistic reactions between O3 and Fe(VI), causing a reduction of activity by ∼40 % when oxidizing the electron-deficient pollutant atrazine. Consequently, we reassessed the activity and mechanisms using a buffer-salt-free O3/Fe(VI) system. Our findings showed that the hydroxyl radical (·OH) served as the predominant active species, responsible for an impressive 95.9 % of the oxidation activity against electron-deficient pollutants. Additional experiments demonstrated that the rapid production of neglected and really important superoxide radicals (·O2-) could facilitate the decomposition of O3 to generate ·OH and accelerate the reduction of Fe(VI) to Fe(V), reactivating O3 to produce ·OH anew. Intriguingly, as the reaction progressed, the initially depleted Fe(VI) was partially regenerated, stabilizing at over 50 %, highlighting the significant potential of this combined system. Moreover, this combined system could achieve a high mineralization efficiency of 80.4 % in treating actual coking wastewater, complemented by extensive toxicity assessments using Escherichia coli, wheat seeds, and zebrafish embryos, showcasing its robust application potential. This study revisits and amends previous research on the O3/Fe(VI) system, providing new insights into its activity and synergistic mechanisms. Such a combined technology has potential for the treatment of difficult-to-degrade industrial wastewater.

Radiation-induced preparation of nanoscale CoO@graphene oxide for activating peroxymonosulfate to degrade emerging organic pollutants

In this study, ionizing radiation was used to induce the in-situ formation of highly dispersed nanosized cobalt oxide on the surface of graphene oxide (R-Co-GO), which was highly effective for activating PMS to degrade sulfamethoxazole (SMX). R-Co-GO had the highest catalytic activity when 150 μL cobalt chloride hexahydrate solution was used in the precursor, and the pseudo first-order kinetic constant of SMX degradation was 0.07 min−1 with high mineralization efficiency (63.1 %) and high PMS utilization efficiency. The sulfate radicals and high-valent cobalt oxo were mainly responsible for SMX degradation. Mechanism analysis showed that cobalt active site dominated in PMS activation, which was responsible for the formation of sulfate radicals and high-valent cobalt oxo; while the carbon framework contributed to the formation of singlet oxygen. The R-Co-GO-150 had good catalytic activity and stability in five cycling experiments, in which SMX was completely degraded and the concentration of dissolved Co was below 0.1 mg/L. In addition, the R-Co-GO-150/PMS system could also degrade phenol, bisphenol A, atrazine and nitrobenzene effectively, confirming its wide applicability. This study provided a facile method to uniformly disperse the metal oxides on the surface of carbon materials, and an effective system for the removal of emerging organic pollutants from the actual wastewater.

A novel continuous-flow photocatalytic device for antibiotic degradation

The presence of antibiotic contaminants in water reservoirs and aquatic environments poses considerable risks to public and ecosystem health. Despite its high mineralization efficiency and environmental friendliness, photocatalytic technology has limited practical applications due to low energy efficiency, intermittent operation, and inconvenient catalyst recovery. Here, we developed a continuous-flow photocatalytic device (CFP-D) with outstanding activity, stability, and university towards antibiotic wastewater degradation. Complete removal of total organic carbon was achieved for multiple antibiotic wastewaters using CFP-D in a continuous flow process. The unique combination of continuous-flow reactor and highly photo-permeable F-Ti-SiO2 aerogel with abundant TiO5 active sites overcomes the limitations of conventional photocatalytic devices. This study provides new insights for the design of highly efficient monolithic catalysts and continuous flow reaction devices, and showcases the immense potential of CFP-D in medical and organic wastewater treatment.

“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.

New BaTi0.96Cu0.02X0.02O3 (X = V, Nb) Photocatalysts for Dyes Effluent Remediation: Broad Visible Light Response

The problem of industrial dyes depollution has pushed the scientific research community to identify novel photocatalysts with high performance. Herein, new photocatalysts composed of BaTiO3, BaTi0.96Cu0.04O3, BaTi0.96Cu0.02V0.02O3 and BaTi0.96Cu0.02Nb0.02O3 powders were prepared by solid-state reaction. The structural analysis of the samples confirmed the formation of the BaTiO3 structure. The splitting of (002) and (200) planes verified the formation of the tetragonal phase. The XRD peaks shifted, and the unit cell volume expansion verified the substitution of the Ti4+ site by Cu2+, V4+ and Nb5+ ions. The morphological measurements showed that the addition of (Cu, V) and (Cu, Nb) ions changes the particles’ morphology of BaTiO3, reducing its grains size. After the incorporation of (Cu, V) and (Cu, Nb) ions, the band gap of BaTiO3 was reduced from 3.2 to 2.84 and 2.72 eV, respectively. The modification of BaTiO3 by (Cu, Nb) ions induced superior photocatalytic properties for methyl green and methyl orange with degradation efficiencies of 97% and 94% during 60 and 90 min under sunlight irradiation, respectively. The total organic carbon results indicated that the BaTi0.96Cu0.02Nb0.02O3 catalyst has a high mineralization efficiency. In addition, it possesses a high stability during three cycles. The high photodegradation efficiency of Bi0.96La0.02Gd0.02FeO3 was related to the wide-ranging visible light absorption.

Waste rice noodle-based CQDs/ZnO composite nanorod array on steel wire mesh: Preparation and photocatalytic capability

In order to develop cost-effective photocatalytic devices, a nanorod array-structured carbon quantum dot/zinc oxide (CQDs/ZnO) composite was synthesized on a steel wire mesh substrate using waste rice noodle (WRN) as the raw material. The incorporation of CQDs derived from WRN played a crucial role in controlling the morphology of the ZnO-based array. By optimizing the loading of CQDs, the CQDs/ZnO composite achieved a regular hexagonal prism nanorod array distribution and exhibited highly efficient photocatalytic degradation of various organic pollutants. For instance, in the case of methylene blue, the CQDs/ZnO composite demonstrated a remarkable degradation rate of 99.4% within 90 min, with a high degradation rate constant of 0.033 min−1. Moreover, the composite material could be recycled and reused for five photocatalytic cycles without a significant decrease in its degradation performance, surpassing the performance of the pure ZnO array. Furthermore, the resulting CQDs/ZnO composite array exhibited effective photocatalytic degradation for other organic dyes such as malachite green, methyl violet, basic fuchsin, and rhodamine B. Additionally, this composite material was successfully applied to real water purification, achieving a high mineralization efficiency of 48% and a low leaching rate of Zn of 1.2% in a river water sample after a 90-minute photocatalytic process. The introduction of CQDs derived from WRN into the ZnO array led to efficient electron-hole pair separation, enabling more photogenerated electrons to reduce O2 and more photogenerated holes to oxidize H2O. This resulted in enhanced radical generation and improved photocatalytic degradation of organic pollutants, showcasing the superior performance of the CQDs/ZnO composite array.

Electrochemical oxidation coupled with hydrated electron reduction in ultraviolet (UV)-sulfite system for complete defluorination and mineralization of Perfluorooctanoic Acid (PFOA)

Hydrated electron reduction in an ultraviolet (UV)-sulfite system and electrochemical oxidation on a boron doped diamond (BDD) anode both are efficient processes for the degradation of perfluorooctanoic acid (PFOA). However, hydrated electron reduction has inherent deficiency in the mineralization (i.e., converting organic carbon into CO2) of PFOA. Furthermore, toxic byproducts such as partially hydrodefluorinated carboxylic acids (HDCAs) and perfluorosulfonic acids (PFSAs) might give secondary pollution if the wholly hydrodefluorination of PFOA is not achieved. BDD electrochemical oxidation can obtain a high mineralization efficiency, but it leads to a low defluorination (i.e., transforming C−F bonds into F− ions) efficiency due to the generation of toxic volatile fluorinated alkanes. Herein, we report a coupled process that is hydrated electron reduction as pre-treatment and BDD electrochemical oxidation as post-treatment to achieve a complete defluorination and mineralization of PFOA, the results demonstrate that 50 mg/L PFOA can be 100 % deluorinated and mineralized under 5 h UV-sulfite reduction followed by 10 h electrochemical oxidation. This coupled process strongly inhibits the production of the toxic volatile fluorinated pollutants and quickly converts the residual toxic sulfite in UV-sulfite system to the sulfate. Mechanism investigation demonstrates that BDD oxidation is able to transform HDCAs and PFSAs formed by hydrated electron reduction to the perfluorocarboxylic acids (PFCAs) with shorter carbon chain than PFOA, which can be further defluorinated and mineralized.

Novel self-sustained flow-through electrochemical advanced oxidation processes using nano-Fe0 confined B, N co-doped carbon nanotubes/graphite felt cathode: Higher mineralization efficiency under wider pH

To improve the mineralization efficiency of pollutants under wide pH ranges by self-sustained electrochemical advanced oxidation processes (EAOPs) without any reagent addition, a flow-through system based on the bifunctional cathode of B, N-doped carbon nanotubes embedded with nano-Fe0 particles that loaded on graphite felt (Fe@BN-C/GF) was developed. Dominant by 1O2 oxidation, the sulfamethazine (SMT) degradation rate and TOC removal in this recirculated flow-through system were 2.6 ∼ 3.3-folds and 1.4 ∼ 2.4-folds that of the batch system under the pH ranges of 3 ∼ 11, respectively. The SMT degradation performance was found not affected in the presence of HCO3–, NO3–, Cl-, K+, or humic acid (HA). The Fe@BN-C/GF cathode had more potential to treat enlarged wastewater by 5-folds during 10 h operation, and the SMT and TOC removal was 99% and 70.31%, respectively. The total phosphorus (TP), ammonia nitrogen (NH3-N) and TOC in reverse osmosis concentrate and secondary wastewater effluent could be simultaneously removed to <0.01 mg L-1 and 8 mg L-1 by this flow-through system with a low electric energy consumption (EEC) of 0.022 and 0.18 kWh gTOC-1, respectively. This EAOPs based on the flow-through Fe@BN-C/GF cathode was self-sustained, and had very promising application prospect of high mineralization of pollutants even for low-conductivity wastewater.

Three-dimensional graphene anchored nZVI hybrid MnO2 as a dissolved oxygen activated Fenton-like catalyst for efficient mineralization of oxytetracycline

This work is dedicated to achieving the high mineralization efficiency of oxytetracycline (OTC) in a dissolved oxygen (DO) activated Fenton-like system by constructing a catalyst with unique catalytic performance. Three-dimensional graphene anchored nZVI hybrid MnO2 (3D-rGO@nZVI/MnO2) with layered and porous structures was synthesized and characterized by field emission scanning electron microscopy coupled with an energy dispersive spectrometer (SEM-EDS), Brunner-Emmet-Teller (BET) analysis, X-ray diffraction (XRD) measurement and Raman spectroscopy. The experimental results showed that the removal efficiency of OTC could reach 100.0% with outstanding TOC decrease of 84.0% at natural pH in the 3D-rGO@nZVI/MnO2-DO system. Moreover, negligible harmful intermediates were detected by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) after the reaction in the 3D-rGO@nZVI/MnO2-DO system. Reactive oxygen species (ROSs) detection, electrochemical measurements and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the elimination mechanism of OTC was the unique catalytic degradation caused by the synergism of •OH and 1O2. The unprecedented synchronous generation of •OH and 1O2 by DO activation provides an innovative strategy for further exploration of Fenton-like system toward more effective degradation of organic pollutants.

Ball milling and acetic acid co-modified sludge biochar enhanced by electrochemistry to activate peroxymonosulfate for sustainable degradation of environmental concentration neonicotinoids.

Neonicotinoids pose potential serious risks to human health even at environmental concentration and their removal from water is considered as a great challenge. A novel ball milling and acetic acid co-modified sludge biochar (BASBC) was the first time synthesized, which performed superior physicochemical characteristics including larger surface area, more defect structures and functional groups (e.g., CO and -OH). Electrochemistry was introduced to enhance BASBC for peroxymonosulfate (PMS) activation (E/BASBC/PMS) to degrade environmental concentration neonicotinoids (e.g., imidacloprid (IMI)). The degradation efficiency of IMI was 95.2% within 60min (C0 (PMS)=1mM, E=25V, m (BASBC)=10mg). Solution pH and anionic species/concentrations were critical affecting factors. The scavenging and electron paramagnetic resonance experiments suggested that •OH and 1O2 were the dominant reactive oxygen species contributing to IMI degradation. Three degradation pathways were proposed and pathway Ⅲ was the main one. 86.1% of IMI were mineralized into non-toxic CO2 and H2O, and others were converted into less toxic intermediates. Also, E/BASBC/PMS system achieved the sustainable degradation of IMI in the cycle experiments. Additionally, it exhibited excellent degradation performance for other three typical neonicotinoids (96.6% of thiacloprid (THI), 96.5% of thiamethoxam (THX) and 82.6% of clothianidin (CLO)) with high mineralization efficiencies (87.8% of THI, 90.5% of THX and 75.4% of CLO).

Regeneration of methylene blue-saturated biochar by synergistic effect of H2O2 desorption and peroxymonosulfate degradation

Biochar, as an adsorbent, is widely used for the removal of organic pollutants in water body. Hence, after saturated adsorption, regeneration treatment is required to recover the adsorption performance of biochar. In this study, a biochar (P-GBC) prepared by phosphoric acid activation showed high adsorption capacity for methylene blue (MB) with the maximum adsorption capacity (Qm) of 599.66 mg/g. Then, regeneration treatments using 4 mM peroxymonosulfate (PMS), 0.2 M hydrogen peroxide (H2O2) and their mixture were used to regenerate MB-saturated biochar with regeneration efficiencies of 58.24%, 66.01% and 94.88%, respectively. Combining with degradation and quenching experiments, it is found that synergistic effect of H2O2 desorption and PMS degradation is responsible for the enhancement of regeneration efficiency of P-GBC in H2O2-PMS system and enables a high mineralization rate of 82.68% for the MB adsorbed on P-GBC. Furthermore, EPR tests indicate that singlet oxygen (1O2) is assigned as the primary activate species for the degradation of MB and XPS analyses confirm that graphite nitrogen and carbonyl on P-GBC are the main active sites for the activation of PMS. Compared with conventional regenerants, H2O2-PMS system has the advantages of low dosage, high mineralization efficiency, and easy accessibility, and is also effective, sustainable and environmentally friendly for the regeneration of organic pollutants-saturated biochar.

Hemin derived iron and nitrogen-doped carbon as a novel heterogeneous electro-Fenton catalyst to efficiently degrade ciprofloxacin

• Hemin derived iron and nitrogen-doped carbon catalyst exhibited high ciprofloxacin degradation and mineralization efficiency. • KHCO 3 -MgO dual-porogen improved the porous characteristics and exposed the iron sites. • Based on degradation intermediates analysis, a possible degradation pathway of CIP was proposed. • It exhibited good stability and potential for treatment of organic pollutants in wastewater. Heterogeneous electro-Fenton (HEF) technology has become a hot topic for degradation of organic pollutants in water. However, it remains a challenge to design effective catalysts for high H 2 O 2 utilization and pollutant degradation. In this work, we explored a novel iron and nitrogen-doped carbon catalyst derived from hemin (Fe-N-C) using KHCO 3 -MgO as dual-porogen. The results suggested that the KHCO 3 -MgO dual-porogen could not only improve the porous characteristics of catalyst, but also expose iron sites and change the proportion of nitrogen species. The pollutant degradation results demonstrated that the Fe-N-C-700/HEF system exhibited high ciprofloxacin degradation efficiency of 93.82% within 50 min and mineralization efficiency of 87.87% within 90 min by low energy consumption. Moreover, cycle experiments and metal ions leaching experiments revealed that the catalyst had good stability and recyclability. Electron spin resonance (ESR) test and radical capturing experiment showed that • OH was the dominant active species in this HEF system. In addition, the Fe-N-C-700/HEF system achieved satisfactory performance in the treatment of real water matrix, indicating the possibility for practical application in wastewater purification.

Synergistic degradation performance of UV/TiO2 photocatalysis and biotrickling filtration inoculated with Aspergillus sp. S1 for gaseous m‐xylene

AbstractBackgroundBiotricking filtration (BTF) based on absorption and biodegradation of waste gas by microorganisms in a biofilm can be used to degrade with difficulty hydrophobic volatile pollutants. Photocatalysis is a promising technology for the abatement of gaseous contaminants because of its nonselective oxidation of volatile organic compounds; however, photocatalysis technology has the limitations of high energy consumption and low mineralization efficiency. This study, therefore, aimed to investigate the synergistic effects of UV/TiO2 photocatalysis (PCO) pretreatment and BTF in treating gaseous m‐xylene.ResultsBTF incubated with a mold, Aspergillus sp. S1, was acclimated with m‐xylene as the sole carbon source. A combined system of PCO with BTF was developed to remove gaseous m‐xylene. The results showed that the startup period was shortened by 3 days in the PCO‐BTF combined system compared to that with BTF alone. The removal efficiency reached 73% and 91% for the BTF and PCO‐BTF systems respectively when the empty bed residence time was extended to 90 s. In addition, PCO‐BTF could withstand transient shock loading of m‐xylene of 5000 mg m−3 and gradually restore its decontamination performance.ConclusionsPCO pretreatment was effective in the enhancement of the removal capacity of BTF for m‐xylene. The PCO‐BTF system proposed in this study provides an attractive alternative to abate hydrophobic volatile pollutants. The integration of PCO essentially prompted the capability of Aspergillus sp. S1 in the BTF unit, which paves the way for the treatment of gaseous waste at an industrial scale. © 2022 Society of Chemical Industry (SCI).

Photocatalytic activity of visible-light-driven L-Proline-TiO2/BiOBr nanostructured materials for dyes degradation: The role of generated reactive species

L-Proline (2%)-TiO2/BiOBr (30%) nanocomposite was synthesized to obtain high photocatalytic performance in the visible light region and infrared radiation(IR) for methylene blue (MB) and congo red (CR) removal from the contaminated wastewater. L-Proline (2%)-TiO2/BiOBr (30%) photocatalyst with strong absorption near IR wavelength and high charge separation ability was fabricated for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field-emission scanning electron microscope (FESEM)/Energy Dispersive X-ray (EDX), UV–Vis diffuse reflectance spectrum (DRS), photoluminescence (PL) and Brunauer-Emmett-Teller (BET) characterization techniques show that the visible driven nanocomposite was successfully synthesized. According to the UV-DRS analysis, the estimated band gaps for the L-proline (2%)-TiO2 and L-Proline (2%)-TiO2/BiOBr (30%) nanostructures were respectively 2.3 eV and 2.1 eV.The nanoparticles exhibited enhanced photocatalytic activity (93–100%) and high mineralization efficiency (71–89% TOC removal) for both the dyes. The best photocatalytic activity was achieved by adding 2 wt% of L-Proline and 30 wt% of BiOBr into TiO2 sol. Response surface methodology (RSM) was employed to find significant parameters and their optimum values for maximum degradation, which show pH, dye concentration, irradiation time, and catalyst dosage for both the dyes are significant. The best photocatalytic degradation efficiency was achieved at the optimum conditions of pH = 7.7, catalyst dosage = 0.71 g/L, irradiation time = 142 and dye concentration = 11 mg/L for MB. Scavenger study showed that •OH radicals are responsible for the degradation process.

Photocatalytic Oxidation for Volatile Organic Compounds Elimination: From Fundamental Research to Practical Applications.

Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy efficiency, and high mineralization efficiency under ambient conditions. However, the practical applications of this technology are limited, despite considerable research efforts in recent decades. Until now, most of the works were carried out in the laboratory and focused on exploring new catalytic materials. Only a few works involved the immobilization of catalysts and the design of reactors for practical applications. Therefore, this review systematically summarizes the research and development on photocatalytic oxidation (PCO) of VOCs, with emphasis on recent catalyst's immobilization and reactor designs in detail. First, different types of photocatalytic materials and the mechanisms for PCO of VOCs are briefly discussed. Then, both the catalyst's immobilization techniques and reactor designs are reviewed in detail. Finally, the existing challenges and future perspectives for PCO of VOCs are proposed. This work aims to provide updated information and research inspirations for the commercialization of this technology in the future.

Bifunctional Ni@NiO catalyst supported on loofah sponge-derived carbon for electrocatalytic air oxidation of biorefractory pollutant in a coupling system.

Oxygen (O2) in the air is a green oxidant, and utilization of air for pollutant removal is highly desired. Herein, we report the preparation and utilization of a novel biomass-based three-dimensional (3D) Ni@NiO/carbon composite for the electro-activation of O2 under room condition. The carbon-coated Ni@NiO nanoparticles are fabricated on a hierarchical 3D porous loofah sponge-derived carbon (LSC) support as the bifunctional catalyst for the activation of O2 via both the electro-oxidation and electro-reduction reactions. An electrocatalytic air oxidation coupling system is constructed with the Ni@NiO/LSC shell-core electrodes for pollutant degradation. A variety of organic pollutants, including pharmaceutics and personal care products (PPCPs), dyes, phenolic compounds, and real waters are mineralized by more than 60% with significantly enhanced biodegradability. Notably, the coupling system obtains high mineralization efficiency of 70.2 ± 1.9% on landfill leachate with significant biodegradability enhancement. The specific energy consumptions of the coupling system are only 6.8 ± 0.7 to 60.2 ± 3.6 kWh kg-TOC-1 in mineralizing different pollutants. The hollow structure of the LSC fibers endows the loaded Ni@NiO with superior intrinsic catalytic activity, which is associated with low reaction resistance and facile electron transfer. The Ni@NiO on LSC presents an electrocatalytic wet air oxidation (ECWAO) catalytic activity higher by 35.8% and cathodic air oxidation (CAO) catalytic activity higher by 22.7% as compared to that loaded on commercial graphite felt.

Removal and mineralization of toluene under VUV/UV lamp irradiation in humid air: Effect of light wavelength, O2 and H2O

VUV/UV photodegradation is a promising method that utilizes energetic photons and reactive oxygen species (ROS) generated via the photo-dissociation of H2O and O2 to degrade VOCs. In the paper, we investigated the efficiency of removal and mineralization in humid air and the effects of key factors. Toluene of 4–20 ppm can be almost completely removed in 60 s and mineralization efficiency is above 55% at 25 min. 185 nm ultraviolet light plays a key role in the rapid removal and mineralization of toluene. Appropriate amount of O2 and H2O promote the removal of toluene due to the generation of ROS. Based on the intermediates and degradation pathway analysis, it is found that in the presence of O2, degradation pathways of toluene are more abundant and fewer linear-chain aldehydes are produced, thus resulting in higher mineralization efficiency. This work highlights the importance of practical application of VUV/UV photodegradation in humid air.

Role of SrCO3 on Photocatalytic Performance of SrTiO3-SrCO3 Composites

Perovskites such as SrTiO3 are interesting for photocatalytic applications due to their structure-related and electronic properties. These properties are influenced by the presence of SrCO3 which is often formed simultaneously during the hydrothermal synthesis of SrTiO3. In this study, SrTiO3-SrCO3 composites with different contents of SrCO3 (5–24 wt%) were synthesized. Their morphological, structural, and optical properties were investigated using complementary methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen sorption, and diffuse reflectance spectroscopy (DRS). Their photocatalytic activity was assessed during the degradation of diclofenac (DCFNa) in aqueous solution and CO2 photoreduction under Xe lamp irradiation. Improved photocatalytic efficiency in DCFNa degradation was observed for all the studied composites in comparison with SrTiO3, and the highest mineralization efficiency was obtained for the sample with 21 wt% SrCO3 content. The presence of SrCO3 led to an increased concentration of active species, such as •OH radicals. Otherwise, its presence inhibits CH4 and C2H6 production during CO2 photoreduction compared with pure SrTiO3.