Undoped TiO2 Research Articles

Cu(II) Doped TiO2 for Photodegradation of Remazol Black B in Aqueous Solution

In the present investigation, Cu(II) doped TiO2 was prepared by a precipitation method. The precipitate was calcined at 300 ºC for2 hours. The prepared doped catalyst was characterized by scanning electron microscope (SEM), energy dispersive X-ray (EDX)spectroscopy and X-ray diffractometry (XRD). SEM images revealed that the morphology of the doped catalyst was different fromthat of TiO2. Elemental analysis was accomplished by EDX that indicated the presence of Cu, Ti and O atoms in the prepared sample.XRD analysis confirmed that TiO2 was present as anatase with almost no distortion in peak position due to the presence of Cu(II)in some interstitial sites. Photodegradation of remazol black B (RBB) was carried out at different experimental conditions underdifferent light sources. The catalytic efficiency of Cu(II) doped TiO2 increased up to a certain dosage then reduced with a furtherincrease in the amount of photocatalyst. The optimum conditions for degradation was found at pH 3.0 under UV light. Under theseexperimental conditions, Cu(II) doped TiO2 degraded 98.8% of RBB, on the other hand, undoped TiO2 degraded only 80.0% of RBB. Dhaka Univ. J. Sci. 70(1): 64-69, 2022 (January)

Black TiO2 Photoanodes for Direct Methanol Photo Fuel Cells.

Photocatalytic fuel cells (PFCs) are considered the next generation of energy converter devices, since they can harvest solar energy through relatively low-cost semiconductor material to convert the chemical energy of renewable fuels and oxidants directly into electricity. Here, we report black TiO2 nanoparticle (NP) photoanodes for simple single-compartment PFCs and microfluidic photo fuel cells (μPFCs) fed by methanol. We show that Ti3+ and oxygen vacancy (OV) defects at the TiO2 NPs are easily controlled by annealing in a NaBH4-containing atmosphere. This optimized noble-metal-free black TiO2 photoanode shows superior PFC performance for methanol oxidation and O2 reduction with a maximum power density (Pmax) ∼2000% higher compared to the undoped TiO2. At flow conditions, the black TiO2 photoanode showed a Pmax ∼90 times higher than the μFC equipped with regular TiO2 in the dark. The PFC and μPFC operate spontaneously with little activation polarization, and black TiO2 photoanodes are stable under light irradiation. The improved photoactivity of the black TiO2 photoanode is a consequence of the self-doping with Ti3+/OV defects, which significantly red-shifted the bandgap energy, induced intragap electronic states, and widened both the valence band and conduction band, enhancing the overall absorption of visible light and decreasing the interfacial charge transfer resistance.

Temperature-dependent photoluminescence of anatase Li-doped TiO2 nanoparticles [Invited

TiO2 is currently one of the most employed material in photocatalysis and optoelectronic applications. By doping with different elements, tailored luminescent and optoelectronic properties can be obtained, which further enhances its applicability. The achievement of deeper knowledge and control on the recombination processes via light-metal doping engineering promises a wider use in optoelectronic applications. In this work, the luminescent properties of undoped and Li-doped anatase TiO2 nanoparticles obtained by hydrolysis process are studied, by means of photoluminescence (PL) measurements from 10 K to room-temperature. TiO2 presents a wide emission which covers the visible range, while Li-doping quenches the emission on the low visible region. By terms of time-resolved luminescence (TR-PL), lifetime of the recombination processes can be obtained, in which a decrease on lifetime values can be observed for the doped samples.

Solar driven photocatalysis using iron and chromium doped TiO2 coupled to moving bed biofilm process for olive mill wastewater treatment

TiO2 based-photocatalysts doped with Fe and/or Cr was evaluated as pre- and post-treatment method of a moving bed biofilm reactor (MBBR) as possible solution for the treatment of real olive oil mill wastewater (OMW). Photocatalysts were synthesized by wet chemical method and their chemical-physical properties were accurately investigated through X-ray diffraction (XRD), Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) and specific surface area measurements. UV–Vis DRS measurements evidenced that the simultaneous doping of TiO2 lattice with Fe and Cr improves the optical absorption into the visible region leading to a narrow band gap (2.1 eV) with respect to undoped TiO2 (3.2 eV) and Fe-doped TiO2 (2.8 eV) while, Cr-doped TiO2 showed the lowest bandgap value (1.9 eV). XRD patterns and Raman spectra showed that anatase is the predominant crystalline phase for all the prepared photocatalysts and Fe and Cr ions were effectively inserted into the TiO2lattice. The TiO2 doping with Cr did not change the average crystallites size that was equivalent to that of TiO2(8 nm), whereas, for Fe- doped TiO2, it was lower than the others and equal to 6 nm. The specific surface area values of doped catalysts were higher than TiO2 and the value for Fe-Cr-codoped TiO2 resulted to be 97 m2g−1. Photocatalytic treatment of OMW was evaluated in terms of total polyphenols (TPHs), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD5) and biodegradability (as BOD5/COD ratio) in 3 h of treatment under simulated solar light irradiation. Fe-doped TiO2 showed the highest TPHs removal for both un-treated and biologically treated OMW. When H2O2 was added (optimum dosage 0.5 gL-1), Fe-Cr-TiO2 resulted in the best photocatalytic performance with TPHs removal as high as 97% and increased biodegradability (0.22 to 0.33), making the effluent suitable for the subsequent biological process. When photocatalytic process was investigated as post-treatment of OMW, Fe-TiO2 showed the best activity and the addition of 0.5 g L-1 of H2O2 was sufficient to make the effluent in compliance with Italian regulation for effluent disposal into surface water.

Degradation of 4-Tert-Butylphenol in Water Using Mono-Doped (M1: Mo, W) and Co-Doped (M2-M1: Cu, Co, Zn) Titania Catalysts.

Mono-doped (Mo-TiO2 and W-TiO2) and co-doped TiO2 (Co-Mo-TiO2, Co-W-TiO2, Cu-Mo-TiO2, Cu-W-TiO2, Zn-Mo-TiO2, and Zn-W-TiO2) catalysts were synthesized by simple impregnation methods and tested for the photocatalytic degradation of 4-tert-butylphenol in water under UV (365 nm) light irradiation. The catalysts were characterized with various analytical methods. X-ray diffraction (XRD), Raman, Diffuse reflectance (DR) spectroscopies, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Energy dispersive spectroscopy (EDS) were applied to investigate the structure, optical properties, morphology, and elemental composition of the prepared catalysts. The XRD patterns revealed the presence of peaks corresponding to the WO3 in W-TiO2, Co-W-TiO2, Cu-W-TiO2, and Zn-W-TiO2. The co-doping of Cu and Mo to the TiO2 lattice was evidenced by the shift of XRD planes towards higher 2θ values, confirming the lattice distortion. Elemental mapping images confirmed the successful impregnation and uniform distribution of metal particles on the TiO2 surface. Compared to undoped TiO2, Mo-TiO2 and W-TiO2 exhibited a lower energy gap. Further incorporation of Mo-TiO2 with Co or Cu introduced slight changes in energy gap and light absorption characteristics, particularly visible light absorption. In addition, photoluminescence (PL) showed that Cu-Mo-TiO2 has a weaker PL intensity than undoped TiO2. Thus, Cu-Mo-TiO2 showed better catalytic activity than pure TiO2, achieving complete degradation of 4-tert-butylphenol under UV light irradiation after 60 min. The application of Cu-Mo-TiO2 under solar light conditions was also tested, and 70% of 4-tert-butylphenol degradation was achieved within 150 min.

Role of Titanium replacement with Pd atom on band gap reduction in the anatase Titanium Dioxide: First-Principles calculation approach

Titanium dioxide (TiO2) is one of the highly promising energy materials. Nevertheless, it has a wide energy bandgap that restricts its absorption capacity within the visible light spectrum. To investigate the effects of doping the transition-metal Palladium (Pd) into anatase TiO2, we perform first-principles calculations in the framework of density functional theory (DFT). All calculations are carried out in the scheme of Hubbard potential (U) correction to account for the correlated effects in TiO2. For this purpose, the first-principles calculations are carried out with the CASTEP code in the formalism of GGA + U. The Pd-doped TiO2 was examined in detail for its electronic structure, lattice parameters, E-K representation, the density of states and optical properties. The results showed that lattice parameters of TiO2 changed after doping. The band structure, partial density of state (PDOS), total density of state (TDOS), complex dielectric function, refractive index, optical absorption, and energy loss function of Pd-doped anatase are improved drastically. It was observed that the doping process adds Pd 4d electronic states into different energy ranges and thus reduces middle states within the band gap region. Our electronic structure calculations indicate augmentation of d-states around the Fermi level, induced by doping Pd. Additionally, compared with the undoped TiO2, the absorption edges of Pd-doped TiO2 show a shift from the UV spectrum towards the visible light region. The results indicate that the GGA + U approach is unique in determining the real band structure of semiconductors which is close enough to empirical results.

Third-order optical nonlinearity of indium-doped rutile TiO2 thin films

Rutile TiO2 and Ti0.9In0.1O2 thin films were fabricated using a pulsed laser deposition method. We employed the optical transmission spectra to reveal the good transparency of the films in the visible spectral range of 330 to 900 nm. The absorption edge of the Ti0.9In0.1O2 film is blue-shifted compared with that of undoped TiO2 film. The third-order optical nonlinearity of the films was investigated by using a z-scan method with a pulse laser operating at 532 nm with a duration of 55 ps. The results show that the Ti0.9In0.1O2 and TiO2 films exhibit nonlinear saturable absorption and negative nonlinear refraction. The doping of In ions does not change the nonlinear optical absorption of the TiO2 film significantly. However, the nonlinear refractive index of Ti0.9In0.1O2 film is about two times larger than that of undoped TiO2 film. The local electron-pinned defect-dipoles and widening bandgap in the Ti0.9In0.1O2 film can be used to explain the observed results.

Photocatalytic Study of Mo/N co-doped Titanium Dioxide (TiO2) Nanoparticles Under Visible Light Irradiation

Undoped TiO2 and Mo/N co-doped TiO2 nanoparticles have been fabricated by sol gel technique. The average particle size of nanoparticles was calculated from the line broadening of (101) peak of XRD pattern and further verified by High Resolution Transmission Electron Microscopy (HRTEM) are in good agreement. The decrease in particle size 28.5 to 15.0 nm was observed with increase of molybdenum concentration. The surface morphology of all samples was studied by Field Emission Scanning Electron Microscopy shows small agglomeration. The optical band gap energy was calculated using UV-visible absorption spectroscopy and found to decrease in increase of doping concentration. The presence of defect levels caused by oxygen vacancies has been confirmed by Photoluminescence spectra. The emission bands observed at 453.9, 470.6, 485.7, 495.8 and 535 nm could be arising from surface states. The phase composition and elemental analysis of synthesized samples was estimated from Energy dispersive X-ray spectroscopy. The effect of doping concentration on structural formation was studied by FTIR spectroscopy. The Photocatalytic activity of synthesized samples for degradation of Congo red (CR) and Methyl orange (MO) dyes as standard pollutants was investigated under visible light source. The increase in doping concentration causes enhance in photocatalytic activity of the synthesized nanoparticles which is attributed from the decrease in electron-hole pair recombination rates. The degradation efficiency against congo red dye is very high compared to methyl orange dye. These observations suggest that co-doped synthesized nanoparticles are suitable for complete degradation of congo red dye and are not able to degrade methyl orange dye.

Photocatalytic activity of Al/Ni doped TiO2 films synthesized by sol-gel method: Dependence on thickness and crystal growth of photocatalysts

Al and Ni doped TiO2 thin films were prepared via sol-gel dip-coating method. The effect of the photocatalysis process on the properties of TiO2 based thin films was investigated. The TiO2 based films were annealed at 450 °C. XRD results show that un-doped TiO2 films were grown with anatase phase, whereas, the Ni and Ni/Al doped TiO2 films show anorthic structure of Ti4O7 single phase. The presence of Al preferred the rutile phase. No phases related to NiO or Al2O3 were detected. Ni/TiO2 photocatalyst shows high photocatalytic activity (∼93%) of Methylene blue (MB) breakdown thanks to the high content of O and Ti, wide band gap (3.35 eV), low crystalline size (6.87 nm), high film thickness (288 nm), and high surface roughness (44.5 nm). After photocatalysis, all the films show a decrease in O content and thickness, whereas the indirect band gap values were increased which suggests the reuse with low photocatalytic activity.

Preparation and photocatalytic application of terbium and sulfur co-doped titanium nanomaterials.

Titanium-based nanomaterials co-doped with terbium (Tb) and sulfur (S) were synthesized by sol-gel method via a facile step. Physicochemical properties of the resulting composites were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), X-ray photo-electron spectroscopy (XPS) and UV-Vis diffused reflectance spectroscopy (DRS). Methylene blue (MB) was used as a degradation target for evaluating the photocatalytic performance. The factors which influence the photocatalytic activity were investigated, including calcined temperatures and S doping amount. Tb, S (2 wt%) co-doped TiO2 composite calcined at 500°C exhibited the highest photocatalytic activity with a degradation rate of 72.4% in 3h. The reaction constant was 0.11529, 0.26025, 0.35038 and 0.41462h-1 for undoped TiO2, Tb-doped TiO2, S-doped TiO2 and Tb, S co-doped TiO2, respectively. Importantly, the synergistic effect of terbium and sulfur dopants was profoundly discussed. Furthermore, recycling tests and acute toxicity experiments were carried out to confirm the reusability and biosafety of Tb, S co-doped TiO2.

Degradation of cefadroxil by photoelectrocatalytic ozonation under visible-light irradiation and single processes

Here, we investigate the degradation of 20 mg L-1 Cefadroxil (CFX) in water using photoelectrocatalytic ozonation (PECO), and compared against its individual processes. A carbon nitrogen-codoped titanium dioxide (CN-TiO2) anode is synthesized using ethylene glycol and ethylenediamine as carbon and nitrogen source, respectively. The X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM) analysis conducted to this material indicate a crystalline phase anatase with irregular morphology formed on the electrode surface; while the diffuse reflectance spectroscopy (DRS) shows a shift in the photoanode absorbance towards the visible region, unlike undoped TiO2 structure. This behavior results from the inclusion of Carbon and Nitrogen species on the CN-TiO2 electrode in weight percentages of 14.5 and 1.61 wt%, respectively, according to Energy Dispersive Spectroscopy (EDS) analysis. The Cefadroxil (CFX) abatement is monitored UV–Vis spectroscopy, high-performance liquid chromatography (HPLC), and total organic carbon (TOC). All techniques reveal that the highest CFX removal occurs with PECO (Photoelectrocatalytic Ozonation) process, decreasing TOC by 57.6% (96% degradation by HPLC) after 90 min of treatment. The main by-products formed from oxidation with the PECO, PCO (Photocatalytic Ozonation) and O3 (Ozonation) systems were acid species presumably corresponding to short chain carboxylic acids. Finally, the germination of lettuce sativa is carried out in water contaminated with the drug, and compared with water treated by PECO and PCO processes, showing that PECO process improves germination by 23.5% on the contaminated sample and 7.4% on the sample treated with PCO. These findings confirm that synergism of oxidation techniques could be a tractable way to resolve the problems related to recalcitrant compounds contained in wastewater.

Synthesis of Fe-doped TiO2 nanotubes by hydrothermal method for photodegradation of methylene blue from aqueous solutions

Fe-doped TiO2 nanotubes were prepared by hydrothermal method using ferric nitrate and commercial TiO2 powder. The obtained materials were characterized by means of XRD, TEM, BET, FT-IR and UV-Vis-DRS. The photocatalytic activity was evaluated based on photodegradation of methylene blue under visible light irradiation. The results show that Fe3+ ions might incorporate into the lattice of TiO2 nanotubes. Fe-doped TiO2 materials showed narrower band gap energies, higher specific surface areas, more hydroxyl groups on the surface and significantly improved photocatalytic activity. The optimum Fe doping at the molar ratios of Fe/Ti = 0.5% showed the highest photocatalytic activity and was 3.08 times higher than that of undoped TiO2. The kinetic studies showed the decomposition of MB followed pseudo first-order kinetics with the rate constant were determined kapp = 5.64×10-2 min−1.

Self-assembled titanium-deficient undoped anatase TiO2 nanoflowers for ultralong-life and high-rate Li+/Na+ storage

Anatase TiO2 is a promising safe and high-rate anode for Li- and Na-ion batteries owing to its moderate redox potential and multi-dimensional ion diffusion paths. However, the capacity, rate and cycle life of anatase TiO2 are severely hindered by the low Li+/Na+ diffusion coefficients. Ti vacancies have been predicted to significantly improve Li+ diffusion kinetics by previous theoretical calculations. However, experimental evidence is still lacking because the existing methods to create Ti vacancies commonly rely on aliovalent doping, i.e., the co-existence of Ti vacancies and foreign anions precludes revelation of the true role and contribution of Ti vacancies alone. The current work reports the synthesis of mesoporous flower-like titanium-deficient anatase TiO2 (TDAT). The formation mechanisms of the Ti vacancies and the micro-architectures are tentatively discussed. Its undoped nature allows elucidation of the unambiguous roles of Ti vacancies on Li+/Na+ storage. Electrochemical results show high capacity, high rate and ultra-long cycle stability for both Li+/Na+ storage in TDAT. DFT calculations reveal that the presence of Ti vacancies results in reduced energy barrier for Li+/Na+ intercalation, enhanced diffusion kinetics, additional Li+/Na+ storage sites and diffusion pathways. For Na+ storage, it achieves a high capacity of 219.9 mAh g−1 at 50 mA g−1, and superior stability over ultra-long 15,000 cycle test at 2000 mA g−1. This work complements with the prevailing view of anion vacancy for improved Li+/Na+ storage.

Characteristics of Mg doped TiO2 thin film based deep UV photodetector

Co-doping of Mg into chemically stable TiO2 thin film is attractive for deep UV detection. In this report, we have fabricated ∼110 nm undoped TiO2 thin film and Mg doped TiO2 thin film based photodetectors on p-type Silicone substrates. The Mg doped TiO2 thin film shows good hydrophobicity. The undoped TiO2 thin film shows low deep UV besides high responsivity in the visible region. The Mg:TiO2 photodetector shows a maximum of four times superior light sensitivity as compared to undoped TiO2 thin film at 200 nm illumination. The Mg:TiO2 thin film shows the countable temporal response at 290 nm but the detector possesses low responsivity in the visible region.

Effect of Fe doping on the microstructure, optical and dispersion energy characteristics of TiO2 thin films prepared via spray pyrolysis technique

In this study, we have delineated the preparation and influence of Fe doping on microstructural and optical properties of the undoped and Fe-doped TiO2 thin film with different Fe concentrations (0, 2, 4, 6, and 8 at.%). The samples are prepared by a simple and cost-effective spray pyrolysis technique (SPT) using Ti(OCH2CH2CH2CH3)4 as a precursor of mother material. The effect of Fe on the microstructure and phase formation of TiO2 thin films is investigated by XRD analysis. XRD investigation depicts that the undoped product corresponds to anatase phase of TiO2 and remains uncontaminated with addition of 2 at.% Fe impurity. It is also observed that Fe introduces a phase transition from anatase to rutile after adulterating more Fe contents (4, 6 and 8 at.%). In order to study the optical characteristics, UV–vis spectroscopy has been employed, which reveals that UV absorption for the Fe incorporated TiO2 products are observed to move to a longer wavelength (red shift) and lower bandgap energy from 3.81 eV (0 at.% Fe) to 3.70 eV (8 at.% Fe) of the TiO2 thin films. The optical constants such as refractive index, complex dielectric constants, tanδ, volume energy loss (VELF) and surface energy loss (SELF) functions, dispersion parameters of synthesized titanium dioxide samples has been studied. The results of optical constant values and the dispersion enegy parameters depicts the influence of Fe on microstructural and optical transportation properties of the as prepared samples more appropriately and effectively.

Synthesis of new C,N,S,Fe-multidoping nanoparticles with potential photochemical response

New multidoped TiO2 nanomaterials with potential photochemical response were synthesized through an uncomplicated sol–gel process, and their structures and properties were evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (DRS) and specific surface area (N2 adsorption-desorption). The results showed that the crystallite size of doped TiO2 nanomaterials was smaller than undoped TiO2 P25 and the surface area of these nanomaterials was found to average 800 m2/g for C,N,S-0.3Fe-TiO2. Their optical properties shifted from UV into visible light region and induced visible light absorption between 394 − 918 nm. The photochemical response of these TiO2 doped nanomaterials was followed using methyl orange (MO) dye under visible light irradiation. In fact, doped TiO2 nanomaterials with nitrogen, carbon, iron and/or sulfur exhibited a photochemical response 2 to 3 folds greater than TiO2 P25, and the photocatalytic efficiency depends on the doses and nature of dopants. In addition, the synergetic of S,N,C, and iron has shown significant effects on the crystalline structure, optical properties, pore volume and surface area.

Theoretical investigation on un-doped and doped TiO2 for solar cell application

Enhancing solar cell efficiency is one of the most challenging and demanding topics for PV researchers. An ab initio study is done here on the structure of crystal, formation energies, electronic structure, the density of states, effective mass, and optical properties of pure and S-doped, Fe-doped, and Fe-/S-doped anatase TiO2. Co-doping causes a significant reduction in the bandgap, suppresses the charge carrier’s recombination rate, and shifted absorption spectra from UV to the visible region. Hence, co-doped anatase TiO2 with Fe and S is more favorable as a buffer layer of the solar cell compared to S-doped and Fe-doped TiO2. The forecasted values of all quantities will benefit researchers to examine these materials for further photovoltaic applications.

Sensing Enhancement of Gold Nanoparticles Doped-TiO<sub>2</sub> Thin Films as H<sub>2</sub>S Gas Sensor

Titanium dioxide and gold nanoparticles were synthesized using an environmentally friendly method to deposit undoped and Au-doped TiO2thin films on silicon and glass substrates via the spray pyrolysis technique. The effect of the Au nanoparticles concentrations on structural, morphological, and hydrogen sulfide (H2S) gas sensing characteristics of TiO2thin films were investigated. An X-ray diffraction pattern confirmed the polycrystalline structure of the films deposited on glass and Si substrates with a dominant rutile phase and the formation of additional mixed-phases of Ti-Au bonding. According to a Field Emission-Scanning Electron Microscopy investigation, the cluster size ranged from 20 to 180 nm depending on the concentration of AuNPs. The sensing response of the prepared films was tested against H2S at different operating temperatures. The effect of growing a mixture of titanium-gold phases as a suitable catalyst for hydrogen sulfide sensitivity is also discussed.

Enhanced Photocatalytic and Photokilling Activities of Cu-Doped TiO2 Nanoparticles.

In this work, metal-doped titanium dioxide (TiO2) was synthesised with the aim of improving photocatalytic degradation and antimicrobial activities; TiO2 was doped with copper (Cu) ranging from 0.1 to 1.0 wt%. The physical and chemical properties of the Cu-doped TiO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), the Brunauer–Emmett–Teller method (BET) and diffuse reflection spectroscopy (DRS). The results revealed that the anatase phase of TiO2 was maintained well in all the Cu-doped TiO2 samples. No significant difference in the particle sizes or the specific surface areas was caused by increasing Cu doping. However, the band gap decreased continuously from 3.20 eV for undoped TiO2 to 3.12 eV for 1.0 wt.% Cu-doped TiO2. In addition, the 0.1 wt.% Cu-doped TiO2 displayed a much greater photocatalytic degradation of methylene blue (MB) and excellent antibacterial ability for Escherichia coli (E. coli) compared to undoped TiO2. On the other hand, the high Cu doping levels had negative impacts on the surface charge of nanoparticles and charge transfer for OH• generation, resulting in decreasing MB degradation and E. coli photokilling for 1.0 wt.% Cu-doped TiO2.

Treatment of a poultry slaughterhouse wastewater using advanced oxidation processes

In the present study, different chemical species such as hydrogen peroxide, potassium persulfate, titanium dioxide, and iron salts were employed for the treatment of a real poultry slaughterhouse wastewater (poultry-SWW) under UV-C light (254 nm). The experiments lasted 150 min and were carried out in a batch photoreactor aiming at investigating the most efficient operating conditions in terms of total organic carbon (TOC) removal. UV photolysis or Fe-doped TiO2 photocatalysis were practically inefficient, while application of un-doped TiO2 resulted in 44% TOC removal after 60 min of UV irradiation. The use of 98 mM H2O2 under UV light led to 74% TOC removal after 150 min. The addition of Fe(II) ions to this system coupled with initial pH adjustment to 3 increased the TOC removal to 82.5% after 150 min. Finally, the combination of UV with 15 mM of K2S2O8 resulted in 85% TOC removal. This was the first time when the persulfate oxidation was successfully applied for SWW treatment. To assess the energy efficiency of the various photochemical treatment processes tested, estimation of the electric energy per order (EEO, kWh/m3/order) was conducted. The lowest EEO value of 226 kWh/m3/order was observed for the UV/K2S2O8 process and compared with other photochemical treatment technologies. The effluent quality of UV/K2S2O8 treatment complies with the discharge water quality standards of the developed countries. Therefore, it is possible to use UV/K2S2O8 process as a post-treatment after biological treatment of SWW to meet the discharge water standards and reuse the wastewater.