Blue TiO2 Research Articles

Periodic polarity reversal triggered sequential electrochemical redox of blue TiO2 nanotube arrays for efficient removal of antibiotics and inorganic nitrogen from actual mariculture wastewater

Using blue TiO2 nanotube arrays (Ti/BTNAs) as both anode and cathode, a novel bipolar system that is suitable for operating in periodic polarity reversal (PR) and flow-through mode was established, aiming to effectively remove antibiotics and inorganic nitrogen from actual mariculture wastewater. Under optimal conditions of 4.0 mA/cm2 current density, 3.0 mL/min water flow rate and 2.0 cycles/h polarity reversal frequency, the PR-induced synergistic effect endows Ti/BTNAs abundant oxygen vacancies (20.53 %), high activity and extended service lifetime (5.25 years), realizing continuous production of surface-adsorbed active hydrogen (Hads∗) at cathode and reactive chlorine species (Cl, ClO, Cl2−, ClO−) over anode through Cl− reacting with reactive oxygen species (HO, SO4−, O2−) and ∼0.7 kWh/gTOC energy consumption. Bipolar system can also flexibly regulate denitrification mechanism through the PR-triggered sequential electrochemical redox of Ti/BTNAs in water flow direction, achieving minimum energy consumption of ∼43.4 ± 3.2 kWh/kg(NH4+-N) and 33.7 ± 2.3 % current efficiency. Berberine antibiotic degradation pathway was suggested by DFT calculations and LC-MS/MS analyses. This study provides a long-acting and low-consuming strategy for comprehensive treating mariculture wastewater.

Enhanced 1,2-dichloroethane removal using g-C3N4/Blue TiO2 nanotube array photoanode in microbial photoelectrochemical cells

The compound 1,2-dichloroethane (1,2-DCA), a persistent and ubiquitous pollutant, is often found in groundwater and can strongly affect the ecological environment. However, the extreme bio-impedance of C–Cl bonds means that a high energy input is needed to drive biological dechlorination. Biotechnology techniques based on microbial photoelectrochemical cell (MPEC) could potentially convert solar energy into electricity and significantly reduce the external energy inputs currently needed to treat 1,2-DCA. However, low electricity-generating efficiency at the anode and sluggish bioreaction kinetics at the cathode limit the application of MPEC. In this study, a g-C3N4/Blue TiO2-NTA photoanode was fabricated and incorporated into an MPEC for 1,2-DCA removal. Optimal performance was achieved when Blue TiO2 nanotube arrays (Blue TiO2-NTA) were loaded with graphitic carbon nitride (g-C3N4) 10 times. The photocurrent density of the g-C3N4/Blue TiO2-NTA composite electrode was 2.48-fold higher than that of the pure Blue TiO2-NTA electrode under light irradiation. Furthermore, the MPEC equipped with g-C3N4/Blue TiO2-NTA improved 1,2-DCA removal efficiency by 45.21% compared to the Blue TiO2-NTA alone, which is comparable to that of a microbial electrolysis cell. In the modified MPEC, the current efficiency reached 69.07% when the light intensity was 150 mW cm−2 and the 1,2-DCA concentration was 4.4 mM. The excellent performance of the novel MPEC was attributed to the efficient direct electron transfer process and the abundant dechlorinators and electroactive bacteria. These results provide a sustainable and cost-effective strategy to improve 1,2-DCA treatment using a biocathode driven by a photoanode.

Indoor-Light-Activated Blue TiO2-Molecule-WO3 Visible Photocatalyst for Antibacterial Performance against Escherichia coli.

Currently used visible light catalysts either operate with high-power light sources or require prolonged periods of time for catalytic reactions. This presents a limitation regarding facile application in indoor environments and spaces frequented by the public. Furthermore, this gives rise to elevated power consumption. Here, we enhance photocatalytic performance with blue TiO2 and WO3 complexes covalently coupled through an organic molecule, 3-mercaptopropionic acid, under indoor light. Antibacterial experiments against 108 CFU/mL Escherichia coli (E. coli) suspensions were conducted under indoor light exposure conditions. They showed a sterilization effect of almost 90% within 70 min and nearly 100% after 110 min. The complex generates reactive oxygen species (ROS), such as •OH and O2•-, under natural air conditions. We also showed that h+ and •OH are important for sterilizing E. coli using common scavengers. This research highlights the potential of these complexes to generate ROS, effectively playing a crucial role in antibacterial effects under indoor light.

A TiO2 nanotube photoanode (blue TiO2 nanotube/RuO2/BiVO4) for efficient acetaminophen degradation and nitrogen removal

To simultaneously remove organic carbon and nitrogen, especially from wastewater containing organic amine compounds, a nanotube photoanode was prepared by depositing RuO2 and BiVO4 nanoparticles in and on a blue TiO2 nanotube substrate (BTNT/RuO2/BiVO4). The synthesized materials were systematically characterized by scanning electron microscope, energy-dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical tests. Acetaminophen, a commonly used pharmaceutical with an amine group, was used as the model pollutant to examine the performance of the prepared electrodes. The results indicated that acetaminophen could be degraded by 100 % in 180 min over BTNT/RuO2/BiVO4 with a rate constant of 0.0338 min−1, which was 25.0 and 1.1 times higher than those obtained over BTNT/BiVO4 and BTNT/RuO2, respectively. Meanwhile, 81.3 % of total nitrogen could be removed. Compared with BTNT/BiVO4 and BTNT/RuO2, BTNT/RuO2/BiVO4 had a significant synergistic effect, and the synergy index reached to 47.7 %. Additionally, BTNT/RuO2/BiVO4 exhibited good stability, high current efficiency (63.2 %) and low energy consumption (0.020 kWh·g COD−1). The good performance of BTNT/RuO2/BiVO4 was mainly attributed to the enhanced formation of ClO· resulted from the synergistic interaction between RuO2 and BiVO4 due to the spatial confinement effect. Lastly, a possible reaction mechanism via ClO· over BTNT/RuO2/BiVO4 was proposed.

Photoelectrochemical properties of anatase TiO2 nanostructures prepared by hydrothermal method: Effect of illumination and external bias on charge transport

A systematic study of photoelectrochemical properties in terms of carrier transport was conducted for TiO2 nanostructure films fabricated on Ti foil at different temperatures (130 °C–210 °C) through alkaline hydrothermal technique, along with the morphological, structural, and optical properties. For samples, the morphology transformed from nanosheets to nanowires, the phase converted from bi-phase of brookite and anatase to pure anatase along with the reduction in the amount of oxygen vacancies as temperature increases. Among them, the dark blue bi-phased TiO2 (brookite and anatase) prepared at 130 °C of hydrothermal treatment (TiO2-130) with nanosheets morphology displayed the optimum photoelectrochemical performance with the highest photocurrent density of 265 μA/cm2 at 1 V (vs. Ag/AgCl), largest carrier density of 1.809 × 1019cm−3 and narrowest space charge region of 11.73 nm. Besides, the large reduction in charge transfer resistance and the width of space charge region caused by simulated solar illumination facilitate the charge transport in photoelectrode especially the TiO2-130 with the largest reduction, indicating the great influence of illumination on carrier dynamics. Moreover, the external bias caused the reduction of resistance under irradiation, the increase in the resistance in the dark. Importantly, the TiO2-210 showed p-type conductivity under illumination inferred from the negative slope of Mott-Schottky plots, which is first observed and further confirm the influence of light on the charge transfer process.

Enhanced degradation of refractory organics in ORR-EO system with a blue TiO2 nanotube array modified Ti-based Ni-Sb co-doped SnO2 anode

Recently, a novel 2-electron oxygen reduction reaction (ORR) based electro-oxidation (EO) system was developed, which utilizes a H2O2 generation cathode instead of H2 evolution cathode. A Ti-based Ni-Sb co-doped SnO2 (Ti/NATO) anode was selected for efficient degradation of refractory organics and O3 production. The synergistic reaction of O3/H2O2 further accelerated the generation of hydroxyl radicals (•OH) in the ORR-EO system. However, the catalytic activity and long-term effectiveness of the Ti/NATO anode limited the large-scale application of the ORR-EO process. In this study, a blue TiO2 nanotube array (blue-TiO2-NTA) inter-layer was introduced into the fabrication process between the Ti substrate and NATO catalyst layer. Compared to the Ti/NATO anode, the Ti/blue-TiO2-NTA/NATO anode achieved higher efficiency of organic removal and O3 generation. Additionally, the accelerated lifetime of the Ti/blue-TiO2-NTA/NATO anode was increased by 7 times compared to the Ti/NATO anode. When combined with CNTs-C/PTFE air cathode in ORR-EO system, all anodic oxidation and O3/H2O2 processes achieved higher •OH production. Over 92% of TOC in leachate bio-effluent was effectively eliminated with a relatively low energy cost of 45 kWh/t.

Highly stable and durable ZnIn2S4 nanosheets wrapped oxygen deficient blue TiO2(B) catalyst for selective CO2 photoreduction into CO and CH4

Developing new and highly stable efficient photocatalysts is crucial for achieving high performance and selective photocatalytic CO2 conversion. In this paper, we designed a one-dimensional oxygen-deficient blue TiO2(B) (BT) catalyst for improved electron mobility and visible light accessibility. In addition, hexagonal ZnIn2S4 (ZIS) nanosheets with a low bandgap and great visible light accessibility are employed to produce effective heterostructures with BT. The synthesized materials are tested for photocatalytic conversion of CO2 into solar fuels (H2, CO and CH4). The optimized composite yields 71.6 and 10.3 μmol g−1h−1 of CO and CH4, three and ten times greater than ZIS, respectively. When ZIS nanosheets are combined with a one-dimensional oxygen-deficient BT catalyst, improved electron mobility and visible light accessibility are achieved, charge carriers are effectively segregated, and the transfer process is accelerated, resulting in efficient CO2 reduction. The photocatalytic CO2 conversion activity of the constructed BT/ZIS heterostructures is very stable over a 10-day (240-hour) period, and CO and CH4 production rates increase linearly with time; however, as time goes on, the rates of H2 production decrease. Further, a five-time recycling test confirmed this, revealing essentially equal activity and selectivity throughout the experiment. As a result, CO2 to CO and CH4 conversion has high selectivity and longer durability. The band structure of the BT/ZIS composite is determined using Mott-Schottky measurement, diffuse reflectance spectroscopy, and valence band X-ray photoelectron spectroscopy. This research demonstrates a novel approach to investigating effective, stable, and selective photocatalytic CO2 reduction systems for solar-to-chemical energy conversion.

One-step hydrothermal generation of oxygen-deficient N-doped blue TiO2–Ti3C2 for degradation of pollutants and antibacterial properties

In this study, TiO2 was generated in situ on the surface of Ti3C2 by a hydrothermal process, and urea was added to form N-doped TiO2–Ti3C2. The surface morphology and functional group properties of the prepared materials were analyzed by SEM, TEM, XRD, XPS, etc. The results showed that anatase TiO2 formed on the surface of the Ti3C2 monolayer. Nitrogen-doped nanomaterials show good phenol degradation and good recyclability under visible light. At a urea content of 0.5 g, the photocatalytic degradation of phenol under visible light is best, reaching 88.9% in 3 h, with ·OH and ·O2− holes playing the leading role. However, at lower pH and higher ion concentration, the degradability of N–TiO2–Ti3C2 for phenol is reduced. Furthermore, the material prepared in this work is a two-dimensional layered material, and the adsorption of phenol best fits the Langmuir adsorption isotherm model and the pseudo-second-order kinetic equation. In terms of the antibacterial performance of the material, the N-doped TiO2–Ti3C2 nanomaterial made with 0.2 g of urea has an Escherichia coli scavenging efficiency of about 97.86%, which is an excellent antibacterial material. This study shows that the N–TiO2–Ti3C2 produced in this experiment can be used for environmental applications.

Electrocatalytic dechlorination of florfenicol using a Pd-loaded on blue TiO2 nanotube arrays cathode

Electrocatalytic hydrodechlorination technology provides an attractive strategy to effectively eliminate the biotoxicity of halogenated organic pollutants (HOPs). Herein, we demonstrated a highly dispersed Pd loaded on blue TiO2 nanotube arrays (Pdx-BTNA) cathode that can achieve efficient dechlorination and detoxification toward florfenicol (FLO). Characterization results indicated that strong interaction between Pd and BTNA was achieved through Pd-O bonds, which facilitated the electron transfer rate. Pdx-BTNA significantly outperformed other cathodes (i.e., BTNA, Pdx-TNA and Pdx-Ti) in the electrocatalytic dechlorination of FLO due to enhanced utilization of active H*. The dechlorination performances of FLO well followed the pseudo-first-order kinetic, and the reaction constant rate on Pdx-BTNA cathode (0.035 min−1) was 17.5, 1.94, 7.0 times higher than that on BTNA, Pdx-TNA and Pdx-Ti cathodes, respectively. Quenching experiments and electrochemical characterization indicated that both direct electron transfer and indirect reduction process mediated by H* were involved in the dechlorination of FLO. The optimal dechlorination efficiency of 98.79% was obtained by Pdx-BTNA cathode within 120 min at 1 mM PdCl2, applied cathode potential of −1.2 V. In addition, Pdx-BTNA exhibited superior stability and durability with almost no Pd leaching (0.0011 mg/L) during five dechlorination cycles. Our research proposed a novel strategy to design low noble Pd-loaded cathode material for efficient dechlorination and detoxification of HOPs.

Complementary conjugated piezo-phototronic polarized blue TiO2 - KNN for piezophotocatalytic degradation of tetracycline enhanced under gentle oscillatory hydrodynamic disturbances

Recently, tetracycline (TC) is classified as an emerging contaminant due to its rapid discharge into the environment from anthropogenic sources. Piezophotocatalysis offers a unique solution to degrade TCs by collaboratively harnessing both solar and hydro energy. However, practical applications have been hampered by the necessitation of high energy requirement ultrasonic baths. In this work, BT-KNN conjugates were investigated for piezophotocatalytic TC degradation. Under agitation conditions, characterization studies demonstrated an amplified photocurrent, diminished charge transfer resistance and reduced radiative recombination. Concomitantly, BT-KNN composites exhibit enhanced TC degradation and apparent rate constant with increased fluid disturbance frequencies, illustrating 91.3% degradation in 3 h under gentle 4 Hz oscillations. These hydrodynamic disturbances engender a propitious piezopolarization which modulated the junction band bending and ameliorated the interfacial charge transfer, intensifying its performance. Optimization studies further illustrates the tradeoff dynamics between high photoactivity of BT and high piezo-enhancement of KNN.

Enhancement of CO2 photoreduction efficiency by supporting blue TiO2 with photonic crystal substrate

Enhancement of CO2 photoreduction efficiency by supporting blue TiO2 with photonic crystal substrate

Electrochemical activation of peroxymonosulfate by 3D printed blue TiO2 nanotube arrays reactive electrochemical membrane for efficient degradation of acetaminophen

Electrocatalytic technology (EC) is a promising strategy for peroxymonosulfate (PMS) activation due to its environmental safety and energy conservation. Herein, 3D printed blue TiO2 nanotube arrays (3DP-BTNAs) reactive electrochemical membranes (REM) were designed as anode and cathode in EC and EC/PMS systems. EC/PMS system displayed superior performance for acetaminophen (ACT) degradation and detoxication. The ACT degradation in EC/PMS system was 3.70 times faster than that in EC system. Quenching experiments suggested that singlet oxygen (1O2) mediated nonradical pathway was responsible for ACT degradation in EC/PMS system, while hydroxyl radical (•OH) was the predominant reactive oxygen species (ROS) in EC system. Our study first provided direct evidence that PMS activation on cathode was mainly triggered by superoxide radical (O2•-). PMS was reduced by O2•- derived from O2 reduction on cathode, and subsequently converted into ROS for organics oxidation. However, PMS tended to adsorb on anode and formed 3DP-BTNAs-PMS* complex for organics degradation. The influencing factors (e.g., PMS dosage, flow rate) on ACT degradation in EC/PMS system were evaluated, and the obtained optimal kinetic constant and lowest energy consumption were 0.135 min−1 and 0.27 Wh/L, respectively. In addition, eight degradation products were identified and possible degradation pathways of ACT were proposed to be the cleavage of C-N bonds and benzene ring. This study is dedicated to the rational design of highly porous REM material by 3DP technology for wastewater treatment and the in-depth mechanism of PMS activation over BTNAs electrode in EC/PMS system.

Electrochemical oxidation of carbamazepine in water using enhanced blue TiO2 nanotube arrays anode on porous titanium substrate

In this study, a blue TiO2 nanotube arrays anode on porous titanium substrate (Ti-porous/blue TiO2 NTA) was successfully fabricated by facile anodization and in situ reduction, and was used to investigate the electrochemical oxidation of carbamazepine (CBZ) in aqueous solution. The surface morphology and crystalline phase of the fabricated anode were characterized by SEM, XRD, Raman spectroscopy and XPS, and the electrochemical analysis confirmed that blue TiO2 NTA on Ti-porous substrate had larger electroactive surface area, better electrochemical performance and higher ⋅OH generation ability than that on Ti-plate substrate. The removal efficiency of 20 mg L−1 CBZ in 0.05 M Na2SO4 solution reached 99.75% at 8 mA cm−2 after 60 min electrochemical oxidation, and the rate constant was 0.101 min−1 with low energy consumption. EPR analysis and free radical sacrificing experiments showed that ⋅OH played a key role in the electrochemical oxidation. The possible oxidation pathways of CBZ were proposed through the identification of degradation products, and the main reactions may involve deamidization, oxidization, hydroxylation and ring-opening. Compared with Ti-plate/blue TiO2 NTA anode, Ti-porous/blue TiO2 NTA anode displayed excellent stability and reusability, and is promising to be used in the electrochemical oxidation of CBZ in wastewater.

Unterscheidung zwischen sauren und basischen Oberflächenhydroxylgruppen auf Metalloxiden durch Fluoridsubstitution: Eine Fallstudie am Beispiel von defektreichem, blauem TiO2 aus der laserbasierten Defekterzeugung

AbstractSowohl oberflächennahe Sauerstofffehlstellen als auch Hydroxylgruppen an der Oberfläche spielen eine entscheidende Rolle in der Katalyse. Dennoch bleiben die genauen Zusammenhänge durch die limitierte analytische Zugänglichkeit dieser Struktureigenschaften oft wenig verstanden. Zur selektiven Quantifizierung der sauren und basischen Oberflächenhydroxide wurde in dieser Studie deshalb eine Fluoridsubstitution am Beispiel zweier Serien von TiO2 (Rutil und P25) untersucht, welche eine zunehmende Dichte an Ti3+‐Sauerstofffehlstellen aufwiesen. Die Materialien sind durch gepulster Laserdefekt‐Engineering in Flüssigkeit (PUDEL) hergestellt worden. Aus EPR‐ und EEL‐Spektroskopie geht hervor, dass sich die lasergenerierten Ti3+ beim Rutil potentiell in der Nähe der Partikeloberfläche befinden, während diese beim P25 tiefer in den Partikeln vorzuliegen scheinen. Anhand der pH‐abhängigen Fluoridsubstitution zeigt sich, dass sich auf dem laserbehandelten Rutil zunehmend saure (verbrückende) Hydroxylgruppen gebildet haben, welche potentiell auf die Hydrierung der lasergenerierten, oberflächennahen Ti3+‐Zentren zurückgeht. Beim P25 blieb die Dichte an Hydroxylgruppen trotz nachweislicher Bildung von Ti3+‐Zentren bei der Laserbehandlung unverändert. Wir gehen davon aus, dass die hier eingesetzte pH‐abhängige Substitutionsmethode von Hydroxiden durch Fluoride zukünftig eine einfache und robuste Charakterisierung von Oberflächen‐OH und deren Korrelation mit Defekten in Metalloxiden zulassen wird.

Electrochemical oxidation of bio-treated landfill leachate using a novel dynamic reactive electrochemical membrane (DREM)

Bio-treated landfill leachate contains complex refractory organics, which lead to short membrane life for subsequent membrane processes. In this work, a blue TiO2 nanotubes (TiO2-BNTs) reactive electrochemical membrane combined with dynamic SnO2-Sb magnetic composite particles (MCPs), i.e., dynamic reactive electrochemical membrane (DREM) technology, was developed to enhance contaminant removal and improve antifouling performance under harsh water quality. A 98% removal of ammonia as well as 67% and 78% reduction in nitrate and total nitrogen were achieved, respectively. An increase of nearly 45% and 20% COD removal in a 2.0 g MCP-loaded DREM was found upon a 0 g MCP-loaded DREM and static TiO2-BNTs/SnO2-Sb membrane electrode (SREM), respectively. The synergetic mechanism revealed the inner dynamic MCP layer (adjacent to TiO2-BNTs surface) played a key role in organic degradation, and the outer layer (adjacent to bulk solution) acted as a protective layer to diminish fouling. Additionally, DREM provided a more optimized distribution and effective usage for reactive oxygen species (ROS). A high and stable COD removal of > 75% was confirmed in repeated experiments. A > 24% lower energy consumption was found with the DREM compared with other electrochemical technologies, which proved the DREM is a viable method for practical applications.

Au nanoparticle sensitized blue TiO2 nanorod arrays for efficient Gatifloxacin photodegradation.

TiO2 nanorod arrays have been widely used in photocatalytic processes, but their poor visible light absorption and rapid carrier recombination limit their application. Both introducing oxygen vacancies and using precious metals as surface plasmon resonance (SPR) stimulators are effective strategies to enhance their photocatalytic performance. Herein, Au nanoparticle sensitized blue TiO2 nanorod arrays (Au/B-TiO2) were successfully fabricated for efficient Gatifloxacin photodegradation. The degradation efficiency of Gatifloxacin was up to 95.0%. Moreover, the corresponding reaction rate constant (Ka) was up to 0.02007 min-1. Additionally, it was suggested that Gatifloxacin could be subject to three different degradation pathways. The superior catalytic activity of Au/B-TiO2 is a result of the combined effect of the two components. Firstly, TiO2 nanorod arrays provide a larger surface area for Au deposition and act as efficient transfer channels. Secondly, the presence of oxygen vacancies in blue TiO2 nanorod arrays enhances the catalytic activity. Thirdly, Au acts as a SPR activator, providing a large number of high-energy electrons in the photocatalysis process. Lastly, the improved light capture capabilities are essential for efficient removal of Gatifloxacin. This work provides a new approach for the construction of a high-performance heterojunction photocatalyst in advanced oxidation processes.

Electrochemical activation of persulfate by Al-doped blue TiO2 nanotubes for the multipath degradation of atrazine

The combination of electrolysis and persulfate activation (E/PDS) is a cost-effective method for the treatment of refractory organics. However, persulfate is difficult to be activated into radicals at the anode, resulting in insufficient electro-activation efficiency. Herein, Al doped blue TiO2 nanotube electrodes (Al-bTNT) were first employed as cost-effective anode materials to fully activate PDS to radicals. In E/PDS, the kinetic constant of atrazine removal by Al-bTNT (0.048 min−1) substantially outperformed the other anodes, including the blue TiO2 nanotube electrodes (bTNT) (0.024 min−1), Ti4O7 (0.02 min−1), and B doped diamond (BDD) anodes (0.023 min−1). The Al-bTNT-E/PDS exhibited a low energy consumption (EEO = 0.72 kWh m−3) and a high mineralization rate. Based on the results of electron paramagnetic resonance, quenching experiments, and probe experiments, we propose that atrazine degrades in the Al-bTNT-E/PDS system mainly via a novel radical pathway that involves both·OH and SO4·- and the generated SO4·- is responsible for the enhanced removal rate. The oxygen vacancies (VO) generated from interstitial Al may serve as the active sites to adsorb and dissociate the persulfate molecules based on extensive characterizations. The attempt at soil-washing wastewater disposal indicated the synergistic system possessed good potential for future practical application.

Blue TiO2 with tunable oxygen-vacancy defects for enhanced photocatalytic diesel oil degradation

The proliferation of marine petroleum exploitation has culminated in the undesired release of oils into the aquatic ecosystem, causing detrimental environmental effects. Photocatalysis proffers a solution to degrade recalcitrant diesel oil utilizing abundant solar energy, in which TiO2 is the perennial photocatalyst of choice. However, it suffers from the low utilization of the light spectrum and the rapid recombination of photogenerated charge carriers. In this work, oxygen-vacancy-rich blue TiO2 was employed to overcome the shortcomings of TiO2 in diesel oil degradation which has historically not been attempted. These oxygen vacancies induce favourable mid gap states to extend the optical absorption capabilities and enrich the photocatalyst charge density. Additionally, oxygen vacancies enhance the separation of electron hole pairs by acting as trap states, evident from increased trap-mediated capture fluorescence. Consequently, a 1.60-fold enhancement of diesel oil degradation performance compared to pristine TiO2 was observed. Mechanistic insights revealed the restructuring of diesel alkane distribution upon degradation corollary to the cleavage of hydrocarbon chains, illustrating that short alkanes experience a greater susceptibility to degradation compared to long alkanes. GC–MS analysis elucidates that shorter chained alkanes, alkenes, alcohols and cycloalkanes were produced as a product of the degradation.

Efficient electro-catalyzed PMS activation on a Fe-ZIF-8 based BTNAs/Ti anode: An in-depth investigation on anodic catalytic behavior

Phenanthrene (PHE), mainly released from coal tar and petroleum distillation, is an important kind of prevalent polycyclic aromatic hydrocarbons (PAHs) contamination in China (up to 2.38 ± 0.02 mg/kg in soil and 8668 ng/L in surface water) and other countries in the world. Metal–organic frameworks (MOFs) show promising application prospects in the decontamination field, however, suffering from the intrinsic fragility and fine powder forms. Therefore, macroscopic MOFs architecture-sandwich-like Fe-ZIF-8/blue TiO2 nanotube arrays (BTNAs)/Ti substrate (FBTT) anode with strong interfacial bonding (Fe-O-Ti and Fe-2-MIM-Ti coordination) was constructed using innovative in situ growth, condensation-crystallization-deposition, and pyrolysis methods, aiming at exploring the feasibility of MOFs-based anode/peroxymonosulfate (PMS) mediated PHE elimination, revealing the in-depth mechanisms, simultaneously overcoming the intrinsic drawbacks of MOFs. The FBTT-4 (doping content of 30 %) efficiently degraded PHE by 90.01 % and 74.5 % within 10 min at 350 μg/L and 3 mg/L, respectively, mediated by the ·OH compared to the SO4·-, 1O2, and O2·-. Post-optimized range of anodic potential enabled (i) anodic oxidation, (ii) activation of water and PMS molecules to produce active species, (iii) capture of electrons in reactants to reduce Fe3+/Ti4+ to Fe2+/Ti3+, maintaining the proportion of Fe/Ti with low valence and thus stable PMS activation capacity, and (iv) regulation of the Fe/Ti d-band center to modulate the anode adsorption capacity. The further increment in anodic potential could promote “dark photocatalysis” with a Z-scheme-like mechanism. Thus, it is proposed that the development of macroscopic MOFs-based anode, especially those with small band gaps, represents vast potentials in electrocatalytic contamination elimination. Simultaneously, the MOFs-based anode is expected to fully exploit their catalytic capacities and solve their intrinsic defects as well.

A Gd3+-doped blue TiO2 nanotube array anode for efficient electrocatalytic degradation of iohexol

A Gd3+-doped blue TiO2 nanotube array anode (Gd-BTNA) was successfully fabricated by the processes of anodization, Gd doping and cathodization. The electrocatalytic activity of a blue TiO2 nanotube array anode (BTNA) can be improved by Gd doping, which introduced oxygen vacancies into the material and increases the specific surface area of the anode. Gd-BTNA is used to eliminate iohexol (IOH) in water, and the optimal operating parameters for electrochemical degradation of IOH are a current density of 15 mA cm−2, initial solution pH of 6.5 and initial IOH concentration of 10 ppm. Coexisting components in wastewater have adverse effects on the treatment process, including Cl–, HCO3–, NH4+ and humic acid. Under the optimal conditions, complete degradation of IOH was obtained within 18 min and more than 52.1% total organic carbon (TOC) was removed after 60 min of reaction time, which outperforms the BTNA and several commercial electrodes. The excellent efficiencies in electrochemical degradation of iohexol show that Gd-BTNA was a promising anode to treat iodinated contrast media contaminants.