Magnetic field effect on the photocatalytic degradation of methyl orange by commercial TiO2 powder

In this work, by taking commercial P25 hydrophilic titanium dioxide (TiO₂) as a photocatalyst, the magnetic field effect (MFE) on the photodegradation rate of methyl orange is studied. It is found that a relatively lower magnetic field B = 0.28 T can efficiently enhance the photodegradation efficiency of commercial TiO₂ by 24%. However, the photodegradation efficiency of commercial TiO₂ will be suppressed slightly by 7% under a magnetic field of 0.5 T. Moreover, such MFE on the photocatalyst is dependent on the settling state of the reaction solution. Additional experiments on the degradation of other pollutants (methylene blue) and with other photocatalysts (g-C₃N₄) indicate that the MFE is a ubiquitous phenomenon in the photocatalytic degradation process. These observations suggest that the magnetic field can be taken as an efficient strategy to regulate the catalytic process of commercial catalysts and improve the catalytic efficiency.

In this work, by taking commercial P25 hydrophilic titanium dioxide (TiO₂) as a photocatalyst, the magnetic field effect (MFE) on the photodegradation rate of methyl orange is studied.     

Photocatalytic degradation of methylene blue by a cocatalytic PDA/TiO2 electrode produced by photoelectric polymerization

This study reports a new method for photocatalysts to degrade organic dyes on organic semiconductors. A novel strategy is reported to form TiO₂ nanorod (NR)/polydopamine (PDA) electrodes with a photoelectric polymerization strategy for PDA (pep-PDA) to produce cocatalytic electrodes. Amperometric i–t curves and UV-vis diffuse reflectance spectra were recorded and showed that compared with traditional self-polymerization (sp-PDA) and electropolymerization (ep-PDA), TiO₂ NR/pep-PDA exhibited an enhanced photocatalytic activity under visible light. As expected, TiO₂ NR/pep-PDA showed a significant improvement for the degradation of methylene blue (MB) under visible light, which can be attributed to the strong absorption of PDA in the visible light region and the more complete and uniform coverage of the TiO₂ NRs by the pep-PDA film. This study not only proposes a novel and highly efficient way to load PDA on TiO₂ NRs but also provides useful insights for the loading of other photocatalysts on organic semiconductors to degrade organic dyes.

This study reports a new method for photocatalysts to degrade organic dyes on organic semiconductors.     

The adsorption characteristics and degradation mechanism of tinidazole on an anatase TiO2 surface: a DFT study

The adsorption characteristics and degradation mechanism of tinidazole on TiO₂(101) and (001) surfaces under vacuum and aqueous solution conditions were studied by density functional theory (DFT). The results show that tinidazole can adsorb on the surfaces of TiO₂(101) and (001) under different conditions. The hydrogen bond generated during the adsorption process can enhance the stability of the adsorption configuration, which makes the bond length of C–N of tinidazole longer and finally facilitates the ring-opening degradation reaction. As for the mechanism of the ring-opening degradation reaction, it was found that ring-opening can be carried out along reaction route II on both crystal surfaces, and the reaction activation energy is lower on (101) surface. Under the conditions of aqueous solution, the decrease of the activation energy of the ring-opening degradation reaction indicates that the solvent conditions can promote the degradation reaction.

The adsorption characteristics and degradation mechanism of tinidazole on TiO₂(101) and (001) surfaces under vacuum and aqueous solution conditions were studied by density functional theory (DFT).     

Adsorption and photocatalytic degradation of gas-phase UDMH under simulated sunlight by AgBr/TiO2/rGA

The degradation of UDMH has long been a concern for its harmful effects on humans and the environment. The current research on gas-phase UDMH treatment is limited and mainly focuses on ultraviolet light and high temperature environments, however the highly toxic substance NDMA is easily produced. In order to investigate the possibility of UDMH degradation in sunlight, AgBr/TiO₂/rGA composites were prepared with the addition of different amounts of silver bromide. The highest UDMH conversion of AgBr/TiO₂/rGA in humid air is 51%, much higher than the control group value of 24%, which can be ascribed to the synergy of adsorption and photocatalysis. The graphene and silver in AgBr/TiO₂/rGA not only enhance the adsorption of light and UDMH, but also inhibit charge recombination and enhance electron–hole separation. More importantly, the temperature of the AgBr/TiO₂/rGA composite was raised by the photothermal effect of graphene with promoted UDMH degradation efficiency. Furthermore, it is noted that NDMA was not detected in the optimal conditions.

An AgBr/TiO₂/rGA composite was prepared to degrade gas-phase UDMH under simulated sunlight by the synergistic effects of absorption and photocatalysis.     

Synthesis of V-modified TiO2 nanorod-aggregates by a facile microwave-assisted hydrothermal process and photocatalytic degradation towards PCP-Na under solar light

Herein, novel V-modified titania nanorod-aggregates (VTNA), consisting of fine individual nanorods in radial direction, were fabricated via an efficient microwave-assisted hydrothermal (MWH) route. VTNA with high crystallinity and homogeneous mesopores were obtained by 30 min MWH processing at 190 °C; moreover, a mixed rutile–anatase phase appeared after vanadium doping. XPS analysis revealed that vanadium existed in the forms of V⁴⁺ and V⁵⁺ on the surface of MWV05 with V⁵⁺ being the dominant component, the content of which was approximately 3.5 times that of V⁴⁺. Vanadium implanting was achieved efficiently by doping 0.5 and 1 at% V using a rapid MWH process and contributed towards the dramatic improvement of the visible-light response, with E_g decreasing from 2.91 to 2.71 and 2.57 eV with the increasing V doping content. MWV05 exhibited optimal photocatalytic degradation activity of water-soluble PCP-Na under solar light irradiation. The enhanced photodecomposition was attributed to the red-shift in the TiO₂ band-gap caused by vanadium impregnation, efficient charge separation due to the V⁴⁺/V⁵⁺ synergistic effects and the free migration of charge carriers along the radial direction of the nanorods arranged in a self-assembled VTNA microstructure.

V-modified titania nanorod-aggregates were fabricated by microwave hydrothermal route. MWV05 exhibited optimal solar activity towards PCP-Na, due to red-shift by V-doping, carriers separation by V⁴⁺/V⁵⁺ synergistic effects and charge migration along the nanorods.     

Preparation of Cu2O@TiOF2/TiO2 and its photocatalytic degradation of tetracycline hydrochloride wastewater

A new high-efficiency photocatalyst Cu₂O@TiOF₂/TiO₂ was synthesized by a hydrothermal method and applied to the degradation of tetracycline hydrochloride (TTCH). The samples were analyzed by SEM, EDS, XRD, BET, UV-vis DRS, Raman, PL, FT-IR. The Cu : Ti = 1 : 8 catalyst showed a narrow band gap of 2.10 eV, indicating that it can degrade TTCH as a novel photocatalyst capable of responding to sunlight. The average particle diameter is (2–6) nm, and the particle size distribution is narrow. When the reaction was carried out under simulated solar light for 3 hours, the efficiency for degrading 10 mg L⁻¹ tetracycline hydrochloride was as high as 96.83% when the catalyst dosage was 40 mg. It is shown from the capture experiments that ·O₂⁻ and ·OH play a major role in this reaction. In addition, it was found that the degradation of TTCH conforms to the first-order kinetic model.

Cu₂O@TiOF₂/TiO₂ composites with large surfaces were prepared by a hydrothermal method and exhibited excellent activity under simulated solar light, showing high efficiency for tetracycline hydrochloride photocatalytic degradation, and reusability.     

Enhanced photocatalytic activity of TiO2/UiO-67 under visible-light for aflatoxin B1 degradation

TiO₂ has great potential in photocatalytic degradation of organic pollutants, but poor visible light response and low separation efficiency of photogenerated electron–hole pairs limit its wide applications. In this study, we have successfully prepared TiO₂/UiO-67 photocatalyst through an in situ solvothermal method. The degradation rate of aflatoxin B1 (AFB1) is 98.9% in only 80 min, which is superior to the commercial P25, commercial TiO₂ and most of reported photocatalysts under visible light irradiation. In addition, the TiO₂/UiO-67 photocatalyst showed excellent recyclability. We demonstrated that the enhanced photocatalytic mechanism was owing to the heterojunction between TiO₂ and UiO-67, which enhanced effectively the separation photogenerated charge carriers and visible light response. The free radical trapping tests demonstrated that superoxide radicals (˙O₂⁻), holes (h⁺) and hydroxyl radicals (˙OH) were the main active species and then oxidized AFB1 to some small molecules.

Enhanced photocatalytic activity of TiO₂/UiO-67 under visible-light for aflatoxin B1 degradation.     

Highly efficient photocatalytic performance of BiI/Bi2WO6 for degradation of tetracycline hydrochloride in an aqueous phase

A series of novel BiI/Bi₂WO₆ nanosheets was successfully synthesized using a simple and efficient one-step hydrothermal method; the obtained specimens were subsequently characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectrophotometry, X-ray photoelectron spectroscopy, N₂ adsorption/desorption isotherms, Raman spectroscopy, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, photoluminescence, and electronic impedance spectroscopy testing. The results indicated that the photocatalytic performance of the BiI/Bi₂WO₆ composites for the degradation of tetracycline hydrochloride (TC) from aqueous media under visible light irradiation (λ > 420 nm) was higher than that of pure Bi₂WO₆. The 0.8I-BiI/BWO composite (where 0.8 is the I : W molar ratio) presented the best photocatalytic performance of all analyzed specimens, and was able to degrade approximately 90% of the TC in 80 min. In addition, radical-capture experiments have demonstrated that superoxide anion radicals and hydroxyl radicals were the main active species for degrading organic pollutants, and a photocatalytic mechanism for the BiI/Bi₂WO₆ system was proposed. This study not only provides a method for the simple preparation of BiI/Bi₂WO₆, but could also present important implications for ecological risk management and prevention against antibiotic pollution.

This study provides a method for the simple preparation of BiI/Bi₂WO₆, and present important implications for prevention against antibiotic pollution.     

Crystalline phase regulation of anatase–rutile TiO2 for the enhancement of photocatalytic activity

Biphasic TiO₂ with adjustable crystalline phases was prepared by the hydrothermal-calcination method assisted by nitric acid (HNO₃) and hydrogen peroxide (H₂O₂), using potassium titanate oxalate (K₂TiO(C₂O₄)₂) as the titanium source. The influences of H₂O₂ volume on anatase and rutile contents and photocatalytic activity of biphasic TiO₂ were investigated and the photocatalytic mechanism was explored. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and specific surface area (BET) were employed to characterize crystal structure, physical morphology, absorbable light, chemical composition, specific surface area and pore size distribution. The photocatalytic degradation efficiency towards a methylene blue (MB) solution under xenon light was tested, and the photocatalytic stability of the sample was investigated by photocatalytic cycle experiments. The prepared biphasic TiO₂ was nanorod-shaped and had a large specific surface area. The results showed the anatase TiO₂ content increased and the photocatalytic efficiency was enhanced as the H₂O₂ volume solution increased. Among the catalysts, the biphasic TiO₂ prepared with 30 mL of H₂O₂ had the best photocatalytic effect and could entirely degrade the MB solution after 30 minutes under irradiation. After three repeated degradations, the photocatalytic degradation rate was still estimated to be as high as 95%. It is expected that the work will provide new insights into fabricating heterophase junctions of TiO₂ for environmental remediation.

Biphasic TiO₂ with adjustable crystalline phases was prepared by the hydrothermal-calcination method assisted by nitric acid (HNO₃) and hydrogen peroxide (H₂O₂), using potassium titanate oxalate (K₂TiO(C₂O₄)₂) as the titanium source.     

Reduced graphene oxide-supported Ag-loaded Fe-doped TiO2 for the degradation mechanism of methylene blue and its electrochemical properties

Graphene oxide-based composites have been developed as cheap and effective photocatalysts for dye degradation and water splitting applications. Herein, we report reduced graphene oxide (rGO)/Ag/Fe-doped TiO₂ that has been successfully prepared using a simple process. The resulting composites were characterized by a wide range of physicochemical techniques. The photocatalytic activities of the composite materials were studied under visible light supplied by a 35 W Xe arc lamp. The rGO/Ag/Fe-doped TiO₂ composite demonstrated excellent degradation of methylene blue (MB) in 150 min and 4-nitrophenol (4-NP) in 210 min under visible light irradiation, and trapping experiments were carried out to explain the mechanism of photocatalytic activity. Moreover, electrochemical studies were carried out to demonstrate the oxygen evolution reaction (OER) activity on rGO/Ag/Fe-doped TiO₂ in 1 M of H₂SO₄ electrolyte, with a scan rate of 50 mV s⁻¹. The reductions in overpotential are due to the d-orbital splitting in Fe-doped TiO₂ and rGO as an electron collector and transporter.

Graphene oxide-based composites have been developed as cheap and effective photocatalysts for dye degradation and water splitting applications.     

SCIP: a new simultaneous vapor phase coating and infiltration process for tougher and UV-resistant polymer fibers

The physical properties of polymers can be significantly altered by blending them with inorganic components. This can be done during the polymerization process, but also by post-processing of already shaped materials, for example through coating by atomic layer deposition (ALD) or hybridizing through vapor phase infiltration (VPI), both of which are beneficial in their own way. Here, a new processing strategy is presented, which allows distinct control of the coating and infiltration. The process is a hybrid VPI and ALD process, allowing separate control of infiltrated and coated components. This new simultaneous vapor phase coating and infiltration process (SCIP) enhances the degrees of freedom for optimizing the properties of polymers, as shown on the example of Kevlar 29 fibers. The SCIP treated fibers show an increase of 17% of their modulus of toughness (MOT) in comparison to native Kevlar, through the nanoscale coating with alumina. At the same time their intrinsic sensitivity to 24 hours UV-irradiation was completely suppressed through another infiltrated material, zinc oxide, which absorbs the UV irradiation in the subsurface area of the fibers.

Simultaneous coating and infiltration of Kevlar fibers with two different inorganic materials significantly improves the modulus of toughness of the polymer and provides protection against UV-induced degradation.     

Effective photocatalytic degradation and physical adsorption of methylene blue using cellulose/GO/TiO2 hydrogels

Environmentally friendly cellulose/GO/TiO₂ hydrogel photocatalyst has been successfully fabricated via a green, simple, and one-step method and evaluated as the photocatalyst and adsorbent for the removal of methylene blue (MB). The XRD and FTIR analysis suggested the strong interaction among cellulose, GO and TiO₂, resulting from the formation of hydrogen bonds. Due to the unique porous structure of cellulose hydrogel and introduction of GO, the cellulose/GO/TiO₂ hydrogel showed superior (degradation ratio ∼ 93%) and reproducible (no significant change during the ten consecutive cycles) performance in the removal of MB under UV light. Consequently, the prepared cellulose/GO/TiO₂ hydrogel can be applied as an eco-friendly, high-performance, reproducible, and stable photocatalyst and adsorbent for the removal of MB. This green hydrogel is a promising candidate for dye wastewater treatment. Moreover, this work is expected to extend the scope of bio-templated synthesis of other nanomaterials for various applications.

New functional cellulose/GO/TiO₂ hydrogels are prepared via a simple method, showing superior and reproducible performance in the removal of MB.     

N/Fe/Zn co-doped TiO2 loaded on basalt fiber with enhanced photocatalytic activity for organic pollutant degradation

To avoid the loss of catalytic material powder, a loaded catalytic material of TiO₂ with basalt fiber as the carrier (TiO₂@BF) was synthesized by an improved sol–gel method. The TiO₂@BF was doped with different contents of N, Fe and Zn elements and was used to degrade rhodamine B (RhB) under ultraviolet light. The physical characterization analysis indicated that the co-doping of the N, Fe and Zn elements had the effects of reducing grain size, increasing sample surface area, and narrowing the electronic band gap. The electronic band gap of nitrogen–iron–zinc co-doped TiO₂@BF (N/Fe/Zn_TiO₂@BF) was 2.80 eV, which was narrower than that of TiO₂@BF (3.11 eV). The degradation efficiency of RhB with N/Fe/Zn_TiO₂@BF as a photocatalyst was 4.3 times that of TiO₂@BF and its photocatalytic reaction was a first-order kinetic reaction. Quenching experiments suggested that the reactive species mainly include photoinduced holes (h⁺), superoxide radicals (˙O₂⁻) and hydroxyl radicals (˙OH). In brief, this study provides a prospective loaded catalytic material and routine for the degradation of organic contaminants in water by a photocatalytic process.

The photocatalytic activity of N/Fe/Zn_TiO₂@BF, synthesized by a combined sol–gel calcination method, showed great improvement for the degradation of RhB. The reaction mechanism of N/Fe/Zn_TiO₂@BF for the degradation of RhB was proposed.     

Photocatalytic degradation of rhodamine B catalyzed by TiO2 films on a capillary column

TiO₂ films on a capillary column were prepared using tetrabutoxytitanium as a source of TiO₂via the sol–gel method. The film thickness showed a linear increase with tetrabutoxytitanium concentration. The specific surface area of the film was improved by adding polyethylene glycol with different molecular weights. Under optimal conditions, the prepared film had a good mesoporous structure with specific surface area of 47.72 m² g⁻¹, and showed nearly spherical nanoparticles with a 10 nm diameter and anatase phase. Influences of the thickness, specific surface area, and initial solution concentration on photodegradation of rhodamine B using TiO₂ films as a catalyst were investigated. The results showed that the photodegradation efficiency increased with an increasing thickness and specific surface area of TiO₂ films. For a rhodamine B solution of 15 mg L⁻¹, the photodegradation efficiency was 98.33% in 30 min under the optimal conditions. The catalysts could be reused up to eight times with almost the same efficiency, indicating a firm immobilization of films on the inner wall of the capillary. Therefore, TiO₂ films are promising for the treatment of wastewater.

TiO₂ films on a capillary column were prepared using tetrabutoxytitanium as a source of TiO₂via the sol–gel method.     

Rapid and selective electrochemical transformation of ammonia to N2 by substoichiometric TiO2-based electrochemical system

In this study, we have developed a continuous-flow electrochemical system towards the rapid and selective conversion of ammonia to N₂, based on a tubular substoichiometric titanium dioxide (Ti₄O₇) anode and a Pd–Cu co-modified Ni foam (Pd–Cu/NF) cathode, both of which are indispensable. Under the action of a suitable anode potential, the Ti₄O₇ anode enables the conversion of Cl⁻ to chloride radicals (Cl˙), which could selectively react with ammonia to produce N₂. The anodic byproducts, e.g. NO₃⁻, were further reduced to N₂ at the Pd–Cu/NF cathode. EPR and scavenger experiments confirmed the dominant role of Cl˙ in ammonia conversion. Complete transformation of 30 mg L⁻¹ ammonia could be obtained over 40 min of continuous operation under optimal conditions. The proposed electrochemical system also exhibits enhanced oxidation kinetics compared to conventional batch systems. This study provides new insights into the rational design of a high-performance electrochemical system to address the challenging issue of ammonia pollution.

A continuous-flow electrochemical system for rapid and selective conversion of ammonia to N₂ was proposed. The system consists of a tubular substoichiometric titanium dioxide (Ti₄O₇) anode and a Pd–Cu co-modified Ni foam (Pd–Cu/NF) cathode.     

TiO2 nanofibres decorated with green-synthesized PAu/Ag@CQDs for the efficient photocatalytic degradation of organic dyes and pharmaceutical drugs

Organic pollutants such as dyes and pharmaceutical drugs have become an environmental menace, particularly in water bodies owing to their unregulated discharge. It is thus required to develop an economically viable and environment-friendly approach for their degradation in water bodies. In this study, for the first time, we report green route-synthesized plasmonic nanostructures (P_M-CQDs (where M: Au and Ag)) decorated onto TiO₂ nanofibers for the treatment of toxic dye- and pharmaceutical drug-based wastewater. P_M-CQDs are efficaciously synthesized using carbon quantum dots (CQDs) as the sole reducing and capping agent, wherein CQDs are derived via a green synthesis approach from Citrus limetta waste. The characteristic electron-donating property of CQDs played a key role in the reduction of Au³⁺ to Au⁰ and Ag⁺ to Ag⁰ under visible light irradiation to obtain P_Au-CQDs and P_Ag-CQDs, respectively. Thus, the obtained CQDs, P_Au-CQDs, and P_Ag-CQDs are loaded onto TiO₂ nanofibers to obtain a P_M-CQD/TiO₂ nanocomposite (NC), and are further probed via transmission electron microscopy, scanning electron microscopy and UV-visible spectrophotometry. The degradation of organic pollutants and pharmaceutical drugs using methylene blue and erythromycin as model pollutants is mapped with UV-vis and NMR spectroscopy. The results demonstrate the complete MB dye degradation in 20 minutes with 1 mg mL⁻¹ of P_Au-CQD/TiO₂ NC, which otherwise is 30 minutes for P_Ag@CQD/TiO₂ dose under visible light irradiation. Similarly, the pharmaceutical drug was found to degrade in 150 minutes with P_Au-CQD/TiO₂ photocatalysts. These findings reveal the enhanced photocatalytic performance of the green-synthesized Au decorated with TiO₂ nanofibers and are attributed to the boosted SPR effect and aqueous-phase stability of Au nanostructures. This study opens a new domain of utilizing waste-derived and green-synthesized plasmonic nanostructures for the degradation of toxic/hazardous dyes and pharmaceutical pollutants in water.

Citrus limetta waste-derived plasmonic nanostructures for photocatalytic degradation of toxic dyes and pharmaceutical pollutants in water.     

Performance and mechanism of methylene blue degradation by an electrochemical process

An exciting electrochemical oxidation (EO) process has been developed. Compared with electro-Fenton (EF) and electro-coagulation (EC) processes, this process had more advantages in the degradation of methylene blue. It is observed that methylene blue can be quickly degraded by EO, in which an iron rod is used as an anode, graphite is used as a cathode, and fly ash–red mud particles are used as particle electrodes. Compared to EC and EF processes that are affected by specific pH values, EO has excellent performance in the pH range of 3.0–11.0. In addition, the electric energy consumption (EEC) of EF, EC and EO is 81.51, 36.55 and 21.35 kW h m⁻³ respectively, suggesting EO is more economical. The free radical scavenging mechanism of i-PrOH is studied, and the contribution of EC, EF and fly ash–red mud particle electrodes in EO is inferred. Particle electrodes before and after use are characterized by SEM, EDS and BET to illustrate the role of particle electrodes in the EO system. Analysis of flocs and solutions by FTIR and GC-MS proves that EO can effectively degrade methylene blue, and the degradation route of methylene blue is speculated. The particle electrode dissolution experiment shows that the prepared fly ash–red mud particle electrode is considered to be suitable and safe for wastewater treatment. Finally, in actual surface water experiments, the EO process still has great potential.

An exciting electrochemical oxidation (EO) process has been developed.     

A facile method for the preparation of black TiO2 by Al reduction of TiO2 and their visible light photocatalytic activity

Black TiO₂ has attracted widespread attention due to its visible light absorption and wide range of applications. However, the currently reported preparation methods for black TiO₂ are not suitable for large-scale production due to its being prepared under high vacuum and over a long time. We have successfully prepared black TiO₂ under normal pressure and short time conditions. The as-prepared black titanium dioxide was characterized by XRD, XPS, TEM, UV-visible absorption spectrum and other characterization methods. The result shows that the as prepared black titanium dioxide had a disordered structure and oxygen vacancy defects on the surface, and exhibits excellent visible and near infrared absorption performance. The black TiO₂ sample was prepared under 650 °C 60 min exhibits excellent visible light photocatalytic performance, and can degrade 56% MO after visible light irradiation for 120 min.

Black TiO₂ has attracted widespread attention due to its visible light absorption and wide range of applications.     

The effect of graphitized carbon on the adsorption and photocatalytic degradation of methylene blue over TiO2/C composites

The TiO₂/C composites with approximately 40 wt% of carbon were prepared by calcination of precursors, formed from a one-pot liquid phase reaction between Ti(SO₄)₂ and flour. All TiO₂/C composites displayed mesoporous structures with high BET surface areas (117–138 m² g⁻¹) and small crystal sizes of TiO₂ (8–27 nm). The contents of graphitic carbon and rutile TiO₂ increased, while the surface area and TiO₂ crystal size decreased for the TiO₂/C composite on increasing the calcination temperature from 650 to 800 °C; when calcinated at 800 °C, the anatase TiO₂ completely changed into rutile TiO₂ in the TiO₂/C composite. The TiO₂/C composite calcinated at higher temperatures exhibited better adsorptive and photocatalytic degradation performance in the removal of methylene blue (MB). For the entire rutile TiO₂/C-800 composite, the adsorption process of MB can be well described by the pseudo-second-order kinetic model and is governed by chemical adsorption with the maximum adsorption capacity value equal to about 15 mg g⁻¹. Under continuous illumination with a 254 nm UV lamp (15 W) for 3 h, the percentage of MB (14 mg l⁻¹) photocatalytic degradation on 50 mg of TiO₂/C-800 was 25.1% higher than that of the maximum adsorption removal. These results suggest that the graphitized carbon has a significant effect on the adsorptivity and photocatalytic activity of the TiO₂/C composite.

The TiO₂/C composites with approximately 40 wt% of carbon were prepared by calcination of precursors, formed from a one-pot liquid phase reaction between Ti(SO₄)₂ and flour.     

Layer-by-layer coating of MIL-100(Fe) on a cotton fabric for purification of water-soluble dyes by the combined effect of adsorption and photocatalytic degradation

Efforts have been made for sustainable development of adsorbents to purify organic contaminants from wastewater. In this study, a MIL-100(Fe) based textile that acts as a reusable adsorbent and photocatalytic agent was developed by synthesizing MIL-100(Fe) onto a cotton fabric by the layer-by-layer (LBL) process using water-based solutions. As the number of LBL cycles increased, the add-on''s of MIL-100(Fe) showed a drastic increase up to 8 cycles, then showed gradual increases with further treatments. The overall adsorption performance was enhanced with the increased MIL-100(Fe) add-on''s, but the specific adsorption efficiency per unit mass of MIL-100(Fe) was reduced as the LBL cycles increased, implying the reduced average adsorption efficiency with a thicker coating. To examine the reusability of the adsorbent, desorption efficiency of RhB was measured. The desorption after the first-time adsorption was not efficient due to the strong binding inside the pores. For the later cycles of adsorption–desorption, desorption occurred more efficiently, probably because RhB molecules were adhered mostly at the outer surface of the MOF layer. Simultaneously, MIL-100(Fe)@cotton demonstrated the photocatalytic degradation performance against RhB in the presence of H₂O₂ by the Fenton reaction. With the combined effect of adsorption and photodegradation, the developed fabric attained 96% removal efficiency for RhB dissolved in water. This study demonstrates an environmentally responsible process of developing a MIL-100(Fe) coated fabric that is readily available for effective removal of organic foulants in water. This fabrication method can be applied as a scalable manufacturing of metal–organic framework-based photocatalytic adsorbent textiles.

A MIL-100(Fe)-based water purifying textile that functions by dual action of adsorption and photocatalytic activity is designed via a layer-by-layer process without using toxic organic solvents.