Doped TiO2 Catalysts Research Articles

Evaporation-induced self-assembly Al doped black TiO2 for the degradation of tetracycline hydrochloride under visible light

Light absorption range, recycling stability and charge transfer efficiency are key to the performance of photocatalytic material. Based on these targets, a Al doped TiO2 catalyst was synthesized by the evaporation-induced process, after processed by NaBH4 reduction, the black TiO2 doped with Al was finally prepared. Uv-vis DRS, EPR and XPS analyses confirm the expanded light absorption window (300 nm - 1000 nm) and the introduction of abundant oxygen vacancy after the reduction process. The final product BTiO2/Al-0.5 has a degradation rate of about 84 % over the tetracycline hydrochloride within 60 minutes, the reaction rate constant (k) is 10.6 times higher than the unreduced sample. The dramatic change of photocatalytic ability can be assigned to the broadened visible light absorption, increased charge separation efficiency, narrowed band gap and defect-enriched oxygen vacancy. This work offers insights into the fabrication of TiO2 catalyst and the introduction of oxygen defect.

Hydrothermally synthesized Nb -doped TiO2 nanosheets for efficient removal of methylene blue dye on photocatalytic performance

In this work, Niobium-doped (1%, 3%, and 5%) titanium dioxide (Nb-TiO2) nanosheets were successfully formed via the hydrothermal route and further characterized using TEM, XRD, XPS and UV–vis absorption spectroscopy techniques. Phase purity and structural information of the prepared materials were analysed by XRD measurements. The band gap values ranged from 3.27 to 2.98 eV as Nb doping increased, leading to improved photocatalytic activity by creating new energy levels close to the conduction band. The XPS results confirm the amalgamation of Nb5+ ions into TiO2 without affecting the crystallinity, structure or orientation of the occurrence of oxygen vacancies. In 3% Nb-doped TiO2, the degradation efficiency for removing (Methylene blue) MB dye increased by ∼96% for the removal of MB dye within 70 min in comparison to pure and other doped TiO2 catalysts The better photocatalytic activity of 3% Nb-TiO2 is due to the longer time between electron–hole pairs before they recombine into one pair. Hydroxyl radicals (HO•) and superoxide radicals (O2 •−) are the primary reactive entities responsible for the deterioration of MB dye. Therefore, incorporating Nb into TiO2 nanostructures represents an auspicious material for the decomposition of hazardous and toxic pollutants in aquatic environments.

Photocatalytic performance of Bi/Zn co‐doped sol–gel synthesized TiO2 nanoparticles

AbstractBACKGROUNDSemiconductor photocatalysts based on TiO2 nanoparticles were synthesized via the sol–gel method and subsequently modified using monometallic (Bi‐TiO2, Zn‐TiO2) and bimetallic (Bi/Zn‐TiO2) doping through the wet‐impregnation technique. The prepared photocatalysts underwent comprehensive characterization using X‐ray diffraction analysis, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse‐reflectance spectroscopy, field emission scanning electron microscopy, photoluminescence, and thermal gravimetric analysis. The photocatalytic performance of these well‐characterized photocatalysts was assessed for the degradation of the model organic pollutant, nitrobenzene.RESULTSAmong the various doped TiO2 catalysts, Bi/Zn co‐doping at a ratio of 0.25:0.75 (w/w) exhibited the most remarkable synergistic effect, achieving approximately 82% degradation of a 50 ppm nitrobenzene solution within just 90 min of reaction time under ultraviolet light irradiation. The rate constant for this process was determined to be 1.79 × 10−2 min−1, suggesting a pseudo‐first‐order kinetics model.CONCLUSIONThe successful co‐doping of Bi and Zn metals to TiO2 resulted in improved photocatalytic performance. The enhanced performance could be attributed to the improved charge transfer facilitated by the synergistic effect among doped metals and TiO2. This finding highlights the significance of bimetallic doping and its potential applications in improving the photocatalytic efficiency of TiO2 nanoparticles for environmental remediation. © 2023 Society of Chemical Industry (SCI).

Unraveling the high catalytic activity of single atom Mo-doped TiO2 toward NH3-SCR: Synergetic roles of Mo as acid sites and oxygen vacancies as oxidation sites

Herein, the single-atom Mo doped TiO2 catalysts with abundant oxygen vacancies (OVs) were fabricated to get a deep insight into the roles of Mo species and OVs for selectivity catalytic reduction (SCR) of NOx. The single-atom Mo doping largely enhances the catalytic activity of TiO2 even with the presence of 5 vol% H2O. Surface Mo species remarkably enhance the strength of Brønsted acid sites on TiO2, which further facilitates the adsorption and activation of NH3 to –NH2. Meanwhile, the in-situ generated OVs largely increase the concentration of monatomic species (O-), which facilitate the oxidation of NO to NO2, thus promoting the catalytic activity below 350 °C. Additionally, the surface polymeric Mo would lead to the side reaction at high-temperature range above 350 °C. This work gives a new insight into the effect of Mo species, and the synergistic role of Mo and OVs in the SCR reaction over Mo-based catalysts.

An efficient P3TA/Fe doped TiO2 catalyst for photo-degradation of Brilliant green dye and inactivation of pathogens under visible light

Brilliant green (BG) belongs to triarylmethane dyes which cause nausea, vomiting, abdominal pain, burning skin or eyes, irritation and diarrhoea. Advanced oxidation process (AOPs) is the ample to removal BG dye from its contamination using semiconductor. TiO2 has proved the benign photo-catalyst for UV light absorption. Doping or co-doping with metal increase the photocatalytic performance, so in this study, poly3-thenoic acid assisted P3TA/Fe doped TiO2 nano-hybrid was prepared via sol–gel approach to assist photocatalytic degradation of BG dye. Analytical instruments were employed in this study to characterize the prepared nano hybrid. BG dye is a model pollutant in this study to examine the photocatalytic performance of proposed P3TA/Fe doped TiO2 nano-hybrid under visible light irradiations and it degrade BG dye completely in 60 min under visible light illuminations. As a result, the results reveal that 0.20 g of P3TA/Fe-TiO2 at pH 10 is a good photo-catalyst for degrading 10 mg/L BG dye solution efficiently. In addition, antibacterial assay also determined over the pathogens of E.coli and S.aureus. This study helps in prepare more efficient photo-catalysts for the removal of dye pollutants from their contaminated water in a large-scale industry.

Fabrication of Ce doped TiO2 for efficient organic pollutants removal from wastewater

Pristine and Ce doped TiO2 nanoparticles were fabricated for toxic pollutants removal from wastewater. Pristine, 2% Ce and 4% Ce doped TiO2 photocatalysts were produced via hydrothermal route. 4% Ce doped TiO2 exhibited 2.41 eV bandgap which is smaller than pure TiO2. The morphology was also investigated and it was established that doping of Ce ions enhanced the surface roughness and reduced the particle size. The surface area was characterized through BET analysis and 4% Ce–TiO2 possess higher surface with large pore diameter which helped the photocatalytic activity. The prepared photocatalysts were investigated on reduction of pollutants from wastewater under visible light. Higher efficiency was obtained for 4% Ce–TiO2 photocatalyst for both model pollutants. The “k” value possessed was also higher for the doped TiO2 catalyst. These analysis reports the optimum level of ceria doping to enhance morphology, surface area and it increased activity than bare TiO2. 4% Ce–TiO2 will be the potential candidate for efficient wastewater management. The 4% Ce doped TiO2 photocatalyst provided 77% and 88% on reducing MB and RhB dyes. The dopant has developed higher surface area, morphology and good recombination rate which reduced the toxic pollutants and changed the wastewater to reuse.

A visible light illumination assistant Li-O2 battery based on an oxygen vacancy doped TiO2 catalyst

TiO2 is regarded as one of the most stable catalysts for Li-O2 battery cathodes, however, the inert surface and weak conductivity limit its catalytic ability. In the present work, a visible light assistant electrode-process on an oxygen vacancy doped TiO2 (TiO2-δ) catalyst is proposed to promote its performances in Li-O2 batteries. The TiO2-δ is prepared by an insufficient oxidation on Ti2O3 through a hydrothermal process and subsequent heat-treatment, and this method guarantees the homogeneous distribution of oxygen vacancies in obtained TiO2-δ catalysts. The TiO2-δ possess a narrow bandgap, leading to a visible light adsorption, which leads to remarkable suppression on overpotential under illumination by xenon lamp in Li-O2 batteries. The electrochemical measurements indicate that, the illumination can obviously enhance the catalytic currents and reduce the electrochemical reaction impedance, and these contributions are responsible for the overpotential decrease. The in-situ gas chromatography is used for inspecting the oxygen flow of a cyclic battery, and the results reveal that, the illumination results in apparent increase in oxygen consumption/evolution in discharge/charge processes. We suggest the photo-induced electrons/vacancies on catalyst surface in discharge/charge processes promote the performances and reversibility of Li-O2 batteries.

Modified-TiO2 Photocatalyst Supported on β-SiC Foams for the Elimination of Gaseous Diethyl Sulfide as an Analog for Chemical Warfare Agent: Towards the Development of a Photoreactor Prototype

In the context of the increase in chemical threat due to warfare agents, the development of efficient methods for destruction of Chemical Warfare Agents (CWAs) are of first importance both for civilian and military purposes. Amongst possible methods for destruction of CWAs, photocatalytic oxidation is an alternative one. The present paper reports on the preparation of Ta and Sn doped TiO2 photocatalysts immobilized on β-SiC foams for the elimination of diethyl sulfide (DES) used as a model molecule mimicking Yperite (Mustard Gas) in gaseous phase. Photo-oxidation efficiency of doped TiO2 catalyst has been compared with TiO2-P25. Here, we demonstrate that the Sn doped-TiO2 with a Polyethylene glycol (PEG)/TiO2 ratio of 7 exhibits the best initial activity (up to 90%) but is deactivates more quickly than Ta doped-TiO2 (40% after 800 min). The activity of the catalysts is strongly influenced by the adsorption properties of the support, as β-SiC foams adsorb DES and other sulfur compounds. This adsorption makes it possible to limit the poisoning of the catalysts and to maintain an acceptable conversion rate even after ten hours under continuous DES flow. Washing with NaOH completely regenerates the catalyst after a firs treatment and even seems to “wash” it by removing impurities initially present on the foams.

Photocatalytic and photosensitization reactions of surface modified W6+ and N3‒ doped TiO2 with curcumin/potassium curcuminate molecules

Curcumin and potassium curcuminate molecules were anchored on W6+ and N3‒ doped TiO2 catalyst (WNT) surface by wet impregnation method and were designated as Cur-WNT and K3Cur-WNT. The XPS and FTIR techniques confirm the surface anchoring of curcumin and potassium curcuminate molecules on the surface of WNT through enolate linkage. K3Cur-WNT catalyst possesses multiple charge trapping states involving dopant energy levels, inherently created defect levels/surface states. Hence the mean free path of the photogenerated electrons is decreased in this catalyst by trapping and detrapping events. The energy band positions of valence band (EVB), conduction band (ECB) and Fermi energy (EF) were determined from the electronegativity values of the atoms present in the catalyst sample and also from the valence band X-ray photoelectron spectroscopic (VBXPS) studies. Energetically the position of conduction band (CB) and W 5d dopant energy levels were found to be located below the lowest unoccupied molecular orbital (LUMO) of curcumin and potassium curcuminate molecules in Cur-WNT and K3Cur-WNT samples. This suitable excited singlet energy band position (S1) of sensitizer molecule facilitates the electron transfer process to the CB/W 5d energy levels of the WNT catalyst. The accumulated electrons in CB/W6+ dopant energy level influence the position of EF within the band gap. The observed higher quantum efficiency of K3Cur-WNT sample compared to all the other catalysts can be accounted to the narrowed band gap, generated shallow traps, reduced particle size, enhanced photosensitivity and its higher capability in generating reactive singlet oxygen species.

An investigation of transition metal doped TiO2 photocatalysts for the enhanced photocatalytic decoloration of methylene blue dye under visible light irradiation

Photocatalytic decolouration of dyes/pollutants using semiconducting materials has grabbed great attention in recent days. The current study focuses on a sol-gel method for preparing semiconducting materials such as TiO2 (titanium oxide) and transition metal (Zn, Zr, Cu) doped TiO2, which were characterized by X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), UV–visible Diffuse Reflectance Spectroscopy (DRS) and UV–visible spectrophotometer, respectively. The photocatalytic behaviour of samples was tested with Methylene blue (MB) dye by observing the decolouration of the MB dye in aqueous solutions under visible light irradiation. The UV-DRS spectra showed that Zn doped TiO2 demonstrated a better photocatalytic efficiency than TiO2 and Zr, Cu doped TiO2 catalysts. The effect of Zn doped TiO2 has a lesser band gap would probably lead to enhance the MB dye degradation in aqueous solutions under visible light irradiation compared to TiO2 and Zr, Cu doped TiO2 catalysts. UV–vis spectrum varied with the irradiation time between 10 and 60 min and the concentration of MB decreased with the increasing irradiation time. UV–vis study revealed that the Zn (0.01) doped TiO2 exhibited 99.64% MB decolouration as compared to 90.4% by pure TiO2. The absorbance spectrum of Zn doped TiO2 exhibited the lighter harvest in the visible light region, which facilitated more light energy for the utilization of the photocatalytic activity for the decoloration of MB. Zn doped TiO2 catalyst exhibited a greater photocatalytic activity than pure TiO2 and the other metal doped TiO2 catalysts.

Performance of Ag-Cu/TiO2 photocatalyst prepared by sol-gel method on the inactivation of Escherichia coli and Salmonella typhimurium

The photocatalytic performance of Ag-Cu/TiO2 materials was evaluated on the inactivation of two gram-negative bacteria that are commonly present in wastewater, namely Escherichia coli and Salmonella typhimurium. The Ag-Cu/TiO2 catalysts at incorporation percentages of 0.3, 1.2 and 2.1 wt.% of each metal were prepared by the sol-gel method. Copper and silver incorporated as Cu2+ and Ag° were analyzed by X-ray photoelectron spectroscopy (XPS) technique. The incorporation of the metal ions causes the reduction of the band gap energy that was evidenced by UV–Vis diffuse reflectance spectroscopy measurements, allowing the activation of the catalyst in the visible region. Complete inactivation of both microorganisms was achieved in 10 min using the co-doped materials at a catalyst load of 0.5 g/L under simulated solar radiation. The co-doped photocatalysts also showed high antimicrobial activity in the absence of light, allowing the treatment to remain effective even in dark conditions. Heterogeneous photocatalysis with Ag-Cu/TiO2 materials demonstrated to be more effective in eliminating from water the gram-negative bacteria than solar disinfection and undoped or individually doped TiO2 catalysts (TiO2, Ag-TiO2 and Cu-TiO2).

A Cu doped TiO2 catalyst mediated Catalytic Thermo Liquefaction (CTL) of polyolefinic plastic waste into hydrocarbon oil

Plastic waste has been identified as a potent feedstock for liquefaction to produce hydrocarbon liquid oil (HC-Oil) by employing Catalytic Thermo Liquefaction (CTL). The resulting process for liquefaction of plastic was termed as Poly-Urja process and produced hydrocarbon oil was termed as HC-Oil. The CTL explores copper doped TiO2 (Cu@TiO2) catalyst as a selective, robust, non-toxic, inexpensive and promising material for liquefaction of polyolefinic plastic waste with minimum char and gas formation. The use of simple, non-expensive and non-complex co-precipitation method has provided a series of Cu@TiO2 catalysts with variable composition of the metal. Of the synthesized catalysts, Cu@TiO2 with 5% metal loading gave maximum conversion and yield of HC-Oil in laboratory batch reactor. The physicochemical and surface morphological properties of the catalyst were studied by using ATR-FTIR, XRD, SEM-EDX, BET and ICP-MS. Process intensification study was conducted to obtain maximum conversion and yield. The intensified CTL process gave >85% conversion and >80% yield of HC-Oil at less stringent conditions. HC-Oil is a carbon rich substrate comprises of 75–85% carbon, 5–15% hydrogen, 5–10% other elements and have a calorific value of ~42 MJ/kg thus it can be used for multiple applications of energy, fuels and chemicals etc. Physicochemical characterization of HC-Oil showed the presence of long and short; straight and branched chains of hydrocarbons (C8-C28). Moreover, CTL can convert any combination of plastic waste into HC-Oil with minimum carbon loss and >80% yield. Thus, the CTL process for polyolefinic waste provides an efficient, sustainable and environmentally friendly alternative to convert plastic waste into energy.

Ni-Bi co-doped TiO2 as highly visible light response nano-photocatalyst for CO2 photo-reduction in a batch photo-reactor

Photocatalytic reduction of CO2 is considered as a promising strategy for production of a wide range of renewable hydrocarbon fuels by solar energy. In this investigation, a series of Ni and Bi doped TiO2 catalysts with different Ni and Bi contents were synthesized by the conventional sol-gel method and tested for CO2 photo-reduction under visible light irradiation. Synthesized nano-photo-catalysts were characterized by XRD, FESEM, TEM, DRS, PL, FTIR and BET analyses. BET results indicated that the doping of Ni or/and Bi in the TiO2 framework resulted in BET specific surface area increment with respect to pure TiO2. DRS analysis showed that Ni doped TiO₂, Bi doped TiO2, and co-doped samples had narrower band gap energy and consequently considerably higher light absorption in the visible region compared with pure TiO₂. Doping Ni and Bi in TiO2 suppressed the rate of electron-hole recombination as indicated by PL spectra. CO2 adsorption capacity were increased in presence of Bi ions in comparison with pure TiO2 and Ni doped sample as a result of reactant adsorption increase on the surface of catalyst. The yield of methane considerably increased in the presence of Ni and Bi doped samples. The highest methane production (21.13 μmol/gcat) was obtained for 1 wt% Ni–3 wt% Bi co-doped TiO₂, which was almost 6.5 times greater than that for pure TiO2.

Visible-light-driven deep oxidation of NO over Fe doped TiO2 catalyst: Synergic effect of Fe and oxygen vacancies

A Fe doped TiO2 catalyst (Fe-TiO2) was evaluated for NO oxidation reaction under visible light irradiation. The Fe-TiO2 not only exhibited better catalytic activity and stability, but also suppressed the production of nitrogen dioxide (NO2) than the undoped TiO2. The results of in situ DRIFTS indicated that visible light benefited the adsorption and activation of NO at Fe sites (Fe-(NO)2) and Ti sites (Ti3+-NO) as well as the formation of active intermediates (e.g. Fe3+-NO3− and Ti4+-NO−). After EPR, DRS, PL and XPS testing, it was proposed that incorporating Fe ions into TiO2 induced the formation of more oxygen vacancies (OVs), while visible light further facilitated this process, resulting in an enhanced adsorption & activation of NO and also a promoted formation of reactive oxygen species (ROS). Thus, a strengthened photo-driven effect for oxidizing NO into NO2− and NO3− occurred on Fe-TiO2.

PREPARATION OF NOVEL X% Li/TiO2 (x = 1%, 2% and 4%) AND THEIR ACTIVITIES UNDER VISIBLE LIGHT

Series of metal doped titanium dioxide were synthesized with the aim to enhance the photocatalytic activity under visible irradiation. x% Li doped TiO2 catalysts (x = 1%, 2% and 4%) were prepared using hydrothermal method. The samples were characterised by specific surface area SBET, X-ray diffraction XRD, diffuse reflectance spectroscopy DRS and photocatalytic activity.We succeeded to obtain high specific surface area samples. In fact, it increases to reach an optimum at 2%dopant amount. XRD analysis showed that all samples are single Anatse phase whatever dopant amount level. The photocatalytic activity was tested in methylene blue degradation under visible irradiation. Two different power lamps were used in order to investigate effect of irradiation condition. These new photocatalysts exhibited visible light activity similar to PC500 to degradated MB. The results were discussed in terms of donor electron level creation in the band gap.

Photocatalytic degradation of ciprofloxacin & norfloxacin and disinfection studies under solar light using boron & cerium doped TiO2 catalysts synthesized by green EDTA-citrate method

The presence of antibiotic residues in water bodies is an emerging global concern due to its potential development of antimicrobial resistance. Hence, it is essential to develop photocatalysts that not only degrade the antibiotics but can also simultaneously disinfect. Four different boron and cerium doped TiO2 photocatalysts, synthesized by the EDTA-citrate method, are studied for the degradation of two common fluoroquinolone-based antibiotics: ciprofloxacin (CIP) and norfloxacin (NOR) under sunlight. The catalysts are characterized by SEM, TEM, Raman spectroscopy, XPS, DRS, BET surface area and particle size analyzer. At optimized conditions, the synthesized catalysts showed 90–93% degradation for both CIP and NOR. The effects of catalyst loading and initial concentration are studied, and the reaction is found to be pseudo-first-order. The degradation is analyzed by COD reduction and LC–MS, and the by-products of degradation determined. The recycle studies showed that the catalysts are stable up to three consecutive runs. The scavenging experiments indicated e― and OH˙ as the dominant species responsible for the photocatalytic activity. The disinfection studies using these catalysts under solar light gave 95–99.99% efficiency for E.coli confirming that they are very efficient and can be further exploited for large scale treatment.

Photocatalytic degradation of ethylbenzene in gas phase over N or NF doped TiO2 catalysts

TiO2 nanoparticles were synthesized via sol–gel method using different N or NF doping precursors. The prepared samples were characterized by UV–Vis-DR Spectroscopy (DRS), X-ray diffraction (XRD), N2 physisorption and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated in the degradation of ethylbenzene in the gas phase at atmospheric pressure and room temperature. The results showed that nitrogen and fluorine were successfully doped in TiO2 leading to a clear narrowing of the band gap energy (red shift). This narrowing was especially observed for N–TiO2 (2.91 eV) when using urea as nitrogen precursor. The sample prepared with 4-fluorobenzyleamine as precursor showed the smallest pore size (around 10 nm) and crystallite size (about 12 nm) compared to the other prepared catalysts. Additionally, it showed the highest efficiency for the photocatalytic conversion of 1000 ppm ethylbenzene, reaching around 32% under UV light and 17% under visible light.

Photocatalytic degradation of flumequine with B/N codoped TiO2 catalyst: Kinetics, main active species, intermediates and pathways

N doped and B/N codoped TiO2 photocatalysts were synthesized by liquid phase precipitation combined with solid phase thermal decomposition method. For comparison, the same method was also used to prepare undoped TiO2 samples. The prepared catalysts were characterized using various techniques including XRD, BET, FT-IR, UV–vis DRS, XPS, SEM and Raman spectroscopy. BET results showed that 300B-N/TiO2 sample has higher BET surface area than undoped TiO2 and N-TiO2 samples. XPS analysis indicated that the B atoms mainly occupy the interstitial position of the TiO2. The photocatalytic performance of prepared undoped and doped TiO2 catalysts was evaluated under simulated sunlight irradiation by employing flumequine (FLU) as a target compound. The photocatalytic performance of TiO2 catalyst can be obviously enhanced by B/N codoping. In addition, B/N codoped TiO2 catalysts exhibit excellent cycling stability. The photocatalytic activity remained 90.1% for 300B-N/TiO2 after four repeated runs. The scavenger study shows that the main reactive species in the photocatalytic degradation process of FLU were superoxide radical (O2−) and photogenerated electrons (e−). Based on detected degradation intermediates of FLU, three possible degradation pathways for FLU were proposed. The degradation of FLU occurs mainly by means of hydroxyl addition and subsequent demethylation and decarboxylation reactions, substitution of fluorine atom by hydroxyl and ring opening of quinolone ring. This work offers a simple method for fabrication of B/N codoped TiO2 photocatalysts, which will be effective in the removal of fluoroquinolones (FQs) in real wastewater.

Doping TiO2 with CuSO4 enhances visible light photocatalytic activity for organic pollutant degradation.

Photocatalysis is one of the most promising advanced oxidation processes due to the capability of solid catalyst to continuously produce oxidant species under light irradiation. The use of conventional UV lamps is high cost intensive, which undermines the possible implementation in developing countries. Visible light active photocatalysts can overcome these challenges and find a market opportunity for competitive technology implementation. This work proposes the synthesis of visible light active catalyst following a facile sol-gel synthesis that introduces CuSO4 as dopant in TiO2. Results present complete abatement of methylene blue in 120min of treatment under 50mWcm-2 of blue light (λ = 450nm), while commercial P25 TiO2 presented null abatement under identical conditions. Synthesis parameters including dopant level and calcination temperature allowed defining optimum synthesis conditions based on material characteristics modification and catalytic activity enhancement. A doping level of 0.21mol% CuSO4 was identified as optimum condition to enable visible light photocatalysis of doped TiO2 catalysts calcined at 300°C. Finally, operational parameters were evaluated defining a wide range of pH operation under 3.0gL-1 of catalyst dose to treat up to 20gL-1 of highly recalcitrant phenothiazine dye. These optimum conditions allowed complete dye removal under visible light after 120min of treatment.

Synthesis of TiO2 catalysts doped with Cu, Fe, and Fe/Cu supported on clinoptilolite zeolite by an electrochemical-thermal method for the degradation of diclofenac by heterogeneous photocatalysis

Aqueous solutions of diclofenac (DCF) were treated by heterogeneous photocatalysis using TiO2 catalysts doped with Cu, Fe, and Cu/Fe supported on the zeolite clinoptilolite, which were prepared by a photo/electrochemical method combined with thermal treatment. The parameters evaluated in the preparation of doped TiO2 catalysts were the treatment time (30 and 60 min), current intensity (0.5 and 1 A), and presence/absence of UV light. The doped materials were characterized by X-ray diffraction, scanning electron microscopy in conjunction with energy dispersive spectroscopy, absorption atomic and infrared spectroscopy, as well as point of zero charge measurements. The concentration of metal in the modified materials was 2.3 g Fe/g for TiFeZ-7, 2.3 g Cu/g TiCuZ-2, and 3.3 g Fe/g and 1.4 g Cu/g for TiFeCuZ-7. The photocatalysis process was carried out at different pH values (4, 5, 7, and 9) and aqueous DCF concentrations (20, 40, 60, 80, and 100 mg/L). The results indicated that the optimal pH for the oxidation of DCF was 4 with efficiencies over 97%. The degradation kinetics at 10 mg/L indicated the mineralization of DCF during the treatment, where the materials doped with copper afforded superior removal of organic matter with efficiencies of 89.5%, 82.2%, and 84.3% for the TOC, COD, and DCF concentration, respectively, as determined by HPLC, revealing the interesting catalytic effect of this metal in such a photocatalysis process.