Synthesis and photocatalytic activity of Na+ co-doped CaTiO3:Eu3+ photocatalysts for methylene blue degradation

The Na⁺ co-doped CaTiO₃:Eu³⁺ powders were produced through the solution combustion method. The phase structure and optical properties of the synthesized samples were adequately characterized by X-ray diffraction (XRD), photoluminescence (PL) spectra, ultraviolet–visible (UV–vis) diffuse reflection spectroscopy and scanning electron microscopy (SEM). The XRD patterns revealed that a low level of Eu³⁺ doping could not cause lattice distortion of CaTiO₃. Photoluminescence (PL) displayed the CaTiO₃:0.5% Eu³⁺ sample synthesized at 900 °C has the weakest PL emission and the low electrons and holes recombination rate. The morphology of the sample was small nanoscale spherical particles. The UV–vis diffuse reflection spectra proved that doping Na⁺ and Eu³⁺ enlarged the absorption region and reduced band energy of pure CaTiO₃. The photocatalytic properties of Na⁺ co-doped CaTiO₃:Eu³⁺ samples were investigated via degrading methylene blue (MB) under ultraviolet light irradiation. The CaTiO₃:0.5% Eu³⁺, 0.5% Na⁺ sample, by contrast, exhibited the greatest photocatalytic property and the degradation rate was as high as 96.62%, which makes it a promising multi-functional material (photocatalytic material and red phosphor) for decreasing organic pollution in water.     

Green synthesis of reduced graphene oxide supported TiO2/Co3O4 nanocomposite for photocatalytic degradation of methylene blue and crystal violet

The hybrid rGO-TiO₂/Co₃O₄ nanocomposite was successfully synthesized through co-precipitation method. The structural, morphological, compositional and optical properties of the as synthesized nanocomposite were characterized by X-ray diffraction (XRD), Field Emission scanning electron microscopy (FESEM), energy dispersive X-Ray Spectroscopy (EDS), Fourier transformation infrared spectroscopy (FTIR), UV–visible spectrophotometer (UV–vis) and photoluminescence (PL). XRD, EDS and FTIR confirms the existence of rGO-TiO₂/Co₃O₄ in the prepared nanocomposite. FESEM confirms that the TiO₂/Co₃O₄ nanocomposite are adsorbed on the surface of the rGO. UV–Vis and PL spectra revealed that the absorbance and emission occurred at visible region, which greatly supports the photocatalytic dye degradation through the electron-hole separation. The percentage decolorization of methylene blue dye solution was higher with lesser time compared to crystal violet dye. This result concludes that the commercialization of rGO/TiO₂/Co₃O catalyst may useful for treating various dyes in industries.     

掺锌纳米TiO_2光催化降解亚甲基蓝研究

选用掺杂锌的纳米TiO2作为光催化剂对亚甲基蓝进行降解研究。制备工艺参数对样品光催化降解亚甲基蓝的活性具有很大影响,焙烧温度为500℃,Zn2+掺入量为0.5%,催化剂的加入量为1 g/L时光催化剂对亚甲基蓝的降解效果最好;亚甲基蓝的初始浓度为5 mg/L降解速率较快。     

A novel cellulose-derived carbon aerogel@Na2Ti3O7 composite for efficient photocatalytic degradation of methylene blue

A scale-up and sustainable method was developed to fabricate novel photocatalyst cellulose-derived carbon aerogel@Na₂Ti₃O₇ composite (CAT) by in situ growth of Na₂Ti₃O₇ nanowhisker on the surfaces of fibers. With a three-dimensional (3D) mesoporous network interconnected structure and a high specific surface area (248.92 m²/g), CAT exhibited excellent photocatalytic activity and methylene blue (MB) removal rate (98.3%). The photocatalytic experimental results showed that the CAT could degrade MB in the aqueous solution within 90 min. Compared with most reported catalysts, CAT exhibited a higher MB removal rate and shorter catalytic time. Therefore, the photocatalyst CAT based on environmentally friendly and low-cost cellulose displayed great application potential in the degradation of MB.     

Electro-catalytic degradation of methylene blue wastewater assisted by Fe2O3-modified kaolin

The electrochemical oxidation of methylene blue (MB) wastewater assisted by Fe₂O₃-modified kaolin in a 200 mL electrolytic batch reactor with graphite plate as electrodes was investigated. The catalyst was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of pH, current density and introduction of NaCl on the efficiency of the electrochemical degradation process were also studied. It was found that Fe₂O₃-modified kaolin has higher catalytic activity in the electrochemical degradation of MB wastewater. 96.47% chemical oxygen demand (COD) removal was obtained in 40 min of electrochemical treatment of MB wastewater at pH 3, current density was equal to 69.23 mA cm⁻².     

Electrophoretic deposition of titania nanostructured coatings for photodegradation of methylene blue

The suspensions of titania nanoparticles were prepared in different alcohols (methanol, ethanol, isopropanol and butanol) using polyethyleneimine (PEI) as dispersant. The results of sedimentation, conductivity, zeta potential, FTIR and thermal analysis showed that PEI macromolecules are protonated in the suspensions and then adsorbed on the particles enhancing their positive surface charge and so colloidal stability. Optimum concentration of PEI (PEI^*) was lower in large molecular size alcohols due to its higher adsorption efficiency. PEI^* was 0.75, 0.5, 0.5 and 0.25?g/l in methanolic, ethanolic, isopropanolic and butanolic suspensions, respectively. Electrophoretic deposition (EPD) was performed at 60?V in different alcoholic suspensions. EPD rate was the fastest in the suspensions with PEI^* due to the highest mobility of particles. In contrast to the coatings deposited for 1?min from isopropanolic and butanolic suspensions, those deposited at same conditions from methanolic and ethanolic ones severely cracked during drying owing to their higher thickness and lower PEI contents (acting as the binder). The coatings deposited from methanolic and ethanolic suspensions with PEI^* had finer and rougher microstructures. The sintered coating deposited at 60?V for 10?s from ethanolic suspension with PEI^* had crack-free microstructure with the thickness of ≈?130?μm. This coating degraded ≈?24% of methylene blue from its aqueous solution (30?ml with the concentration of 5?mg/l) within 2?h under UV illumination. Photodegradation of MB on the surface of titania coating obeyed the first order kinetics law.     

Adsorption of selected dyes on Ti3C2Tx MXene and Al-based metal-organic framework

MXene and metal organic framework (MOF) were used as the main adsorbents to remove synthetic dyes from model wastewater. Methylene blue (MB) and acid blue 80 (AB) were used as the model cationic and anionic synthetic dyes, respectively. To investigate the physicochemical properties of the adsorbents used, we carried out several characterizations using microscopy, powder X-ray diffraction, a porosimetry, and a zeta potential analyzer. The surface area of MXene and MOF was 9 and 630 m² g⁻¹, respectively, and their respective isoelectric points were approximately pH 3 and 9. Thus, MXene and MOF exhibited high capacity for MB (~140 mg g⁻¹) and AB (~200 mg g⁻¹) adsorption, respectively due to their electrostatic attractions when the concentrations of the adsorbents and adsorbates were 25 and 10 mg L⁻¹. Furthermore, the MOF was able to capture the MB due mainly to hydrophobic interactions. In terms of the advantages of each adsorbent according to our experimental results, MXene exhibited fast kinetics and high selectivity. Meanwhile, the MOF had a high adsorption capacity for both MB and AB. The adsorption mechanisms of both adsorbents for the removal of MB and AB were clearly explained by the results of our analyses of solution pH, ionic strength, and the presence of divalent cation, anion, or humic acids, as well as other characterizations (i.e., Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy). According to our results, MOF and MXene can be used as economical treatments for wastewater containing organic pollutants regardless of charge (e.g., MB and AB), and positively charged one (e.g., MB), respectively.     

Photocatalytic degradation of methylene blue and sulfisoxazole from water using biosynthesized zinc ferrite nanoparticles

The extensive occurrence of textile and pharmaceutical contaminants and their metabolites in water systems has posed significant concerns regarding their possible threat to human health and the environmental system. As a result, herein ZnFe₂O₄ nanoparticles were synthesized through the use of Monsonia burkeana plant extract. The synthesized nanoparticles were characterized using XRD, FTIR, UV–vis, SEM, EDS, TGA, BET, PL, EPR and VSM. XRD showed that the crystalline structure of ZnFe₂O₄ nanoparticles with a calculated crystal size of 25.03 nm was formed. FT-IR confirmed the characteristic functional groups contained within the M. burkeana plant were deposited on the formed ferrite nanoparticles. BET analysis confirmed the mesoporous nature of ZnFe₂O₄ with an average pore diameter of 31.6 nm. Morphological studies demonstrated that the formed nanoparticles had spherical as well as rod-like shapes. ZnFe₂O₄ photocatalyst illustrated that it may be effortlessly detached by an external magnetic field. The optimum conditions for the 99.8% removal of Methylene Blue was obtained at pH12, within 45min and at the optimum dosage of 25 mg of the catalyst. The as-prepared ZnFe₂O₄ nanoparticles proved to be easily separated and recycled, and remained efficient even after 5 reuses, proving that the material is highly stable. The ROS studies also demonstrated that electrons are the main factors contributing to the degradation of MB. Upon testing the photocatalytic performance of the sulfonamide antibiotic, sulfisoxazole in water showed a degradation of 67%. This study has shown that these materials can be used in targeting textile and pharmaceutically polluted water.     

Electrophoretically deposited halloysite nanotubes coating as the adsorbent for the removal of methylene blue from aqueous solution

Halloysite nanotubes (HNTs) coatings were prepared by electrophoretic deposition (EPD) from different alcoholic suspensions using polyethyleneimine (PEI) as the dispersant. The results of conductivity, zeta potential, FTIR and thermal analysis showed that PEI is protonated in alcoholic suspensions and then adsorbed on the surface of HNTs enhancing their zeta potential and so colloidal stability. Optimum concentration of PEI decreased with molecular size of alcohol due to the more adsorption of PEI on HNTs. Kinetics of EPD was the fastest from the suspensions with the highest zeta potential. HNTs coatings exhibited high resistance against cracking during their drying due to the self-reinforcement provided by long HNTs and the presence of PEI in their composition which acts as the binder. The coating (6cm²) deposited from ethanolic suspension with 0.5?g/l of PEI (optimum suspension) removed 36% of MB from its aqueous solution (concentration: 5?mg/l and volume: 30?ml) within 2?h.     

Synthesis,characterization, photocatalytic and antibacterial properties of copper Ferrite/MXene (CuFe2O4/Ti3C2) nanohybrids

The synthesis of CuFe₂O₄/MXene nanohybrids was carried out via an ultrasonication approach. The prepared composite material exhibited an outstanding photocatalytic performance and antibacterial activity compared to individual CuFe₂O₄ (CF) and MXene. The CF nanonuts (Nns) assisted the reduced aggregation of MXene layers. The structural and morphological analysis of the presented nanohybrids were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), Electrochemical impedance spectroscopy (EIS), and ultraviolet (UV)-visible spectroscopy. The obtained sheet-to-sheet linkage provided an opportunity for the degradation of organic dyes. The photocatalyst CF/MXene nanohybrids exhibited 4.5-fold higher photocatalytic activity than pristine CF. The mechanism of degradation of methylene blue dye by CF/MXene was explained through kinetic studies. This work will offer significant scientific contributions to researchers working on water desalination.     

Fabrication of novel SnWO4/ZnO using Muntingia calabura L. leaf extract with enhanced photocatalytic methylene blue degradation under visible light irradiation

In this study, SnWO₄/ZnO heterostructure has been successfully constructed using Muntingia calabura L. leaf extract (MCE). We conducted phytochemical tests to qualitatively detect the presence of secondary metabolites such as alkaloids, saponins, flavonoids, and tannins, which play an essential role in the formation of SnWO₄/ZnO. The photocatalytic activities of pristine SnWO₄, pristine ZnO, and SnWO₄/ZnO heterostructure were evaluated for the degradation of methylene blue (MB) under visible light irradiation. To investigate the photocatalytic activity of SnWO₄/ZnO heterostructure in the visible region, the adsorption effect of SnWO₄/ZnO was also studied. SnWO₄/ZnO heterostructure shows the highest degradation percentage of 82.86% within 120 min compared to pristine SnWO₄ and ZnO, which exhibit the degradation percentage of 69.48 and 40.41%, respectively. The enhanced photocatalytic of MB degradation is attributed to the formation of SnWO₄/ZnO heterostructure as a result of the decreased optical bandgap from 3.06 to 2.68 eV due to the low recombination rate of photogenerated electron-hole pairs. SnWO₄/ZnO shows a remarkable photocatalyst for dyes degradation with remarkable stability after four consecutive cycles. Importantly, this work demonstrates a simple eco-friendly, and low-cost green synthesis method to produce SnWO₄/ZnO with excellent photocatalytic activity and stability for dyes degradation under visible light irradiation.     

超声-S/TiO_2纳米颗粒可见光催化协同降解亚甲基蓝

采用共沉淀-浸渍法制备掺杂S的TiO2光催化剂,利用XRD,TEM,UV-Vis-DRs,XPS等方法对其结构、元素组成和光谱学特征进行研究,以亚甲基蓝(MB)的光催化降解反应为模型,探讨高效利用可见光降解亚甲基蓝的反应体系。实验结果表明,S掺杂最佳热处理温度为500℃。掺杂光催化剂晶型仍为锐钛矿型,其粒径变小,比表面积增大,热稳定性增加,对可见光的吸收增强。超声波对光催化降解反应有协同作用,S/TiO2在可见光下对亚甲基蓝的降解率明显高于纯TiO2。     

Preparation of aerochitin‐TiO2 composite for efficient photocatalytic degradation of methylene blue

An aerochitin–titania (TiO₂) composite was successfully synthesized and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and N₂ adsorption isotherms. The photocatalytic activity of the composite was investigated on the degradation of the model organic pollutant, methylene blue (MB) dye, under UV irradiation. The aerochitin–TiO₂ composite showed excellent adsorptive and photocatalytic activity with a degradation degree of 98% for MB. The first‐order rate constants for the photodegradation MB by TiO₂ nanoparticles and aerochitin–TiO₂ composite were found to be (3.49 ± 0.04) × 10^?3 and (1.82 ± 0.02) × 10^?2 min^?1. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45908.     

聚丙烯酸/聚丙烯酰胺/凹凸棒复合材料对亚甲基蓝的吸附性能

将聚(丙烯酸-co-丙烯酰胺)/凹凸棒复合吸附剂用于亚甲蓝的吸附,研究了时间、浓度、酸度、表面活性剂和离子强度等因素对吸附性能的影响。复合吸附剂对亚甲蓝的吸附是吸热过程,60℃时吸附量达到1 273.3 mg.g-1,吸附过程符合Langmuir单分子层吸附等温模式,并计算了热力学常数ΔG、ΔH和ΔS。在实验考察范围内吸附过程均符合准二级动力学特征。该复合吸附剂具有高吸附容量和较快的吸附速率,是良好的亚甲蓝吸附剂。     

Photoelectric catalytic degradation of methylene blue by C60-modified TiO2 nanotube array

Fullerene (C₆₀)-modified TiO₂ nanotube array (TNA) was prepared by the electrophoresis deposition technique. The as-prepared samples showed the high efficiency for the photoelectric catalytic (PEC) degradation of nonbiodegradable azodyes methylene blue (MB). The highest PEC activity of C₆₀-modified TNA (TNA/C₆₀) was achieved at a lower bias potential (4.0 V), which was 2.3 times of the highest activity of TNA at 5.0 V. The high PEC activity came from the synergetic effect between C₆₀ and TiO₂, which promoted the charge separation, influenced the charge distribution of the electrical double layer and reduced the impedances of the Helemholtz and depletion layers. Moreover, the oxidation of MB was a quick process during the PEC degradation, and the process began with the oxidation of the dimethylamino group, which was different from the photocatalytic (PC) process began with the oxidation of S atom; MB was mineralized completely during PEC degradation.     

Sunlight assisted photoelectrocatalytic degradation of benzoic acid using stratified WO3/TiO2 thin films

The stratified WO₃/TiO₂ thin films have been deposited onto glass and FTO coated glass substrates using simple chemical a spray pyrolysis method. The structural, morphological, compositional and photoelectrocatalytic properties of the stratified WO₃/TiO₂ thin films are studied. The photoelectrochemical (PEC) study shows that, both short circuit current (I_sc) and open circuit voltage (V_oc) are (I_sc =1.192 mA and V_oc =0.925 V) relatively high at 50 ml spraying quantity of TiO₂ solution on pre-deposited WO₃. XRD analysis confirms that films are polycrystalline with monoclinic and tetragonal crystal structures for WO₃ and TiO₂ respectively. Specific surface area of 72.14 m² g⁻¹ is measured by Brunauer-Emmett-Teller (BET) technique. Photoelectrocatalytic degradation of benzoic acid (BA) dye in aqueous solutions is studied. The end result shows that the degradation percentage of benzoic acid (BA) using stratified WO₃/TiO₂ photoelectrode has reached 66% under sunlight illumination after 320 min. The amount of degradation is confirmed by COD analysis.     

微波诱导催化氧化水钠锰矿降解亚甲基蓝

系统研究了水钠锰矿在微波的作用下催化降解亚甲基蓝(MB)的效果和影响因素,并结合X射线衍射技术(XRD)、傅里叶变换红外光谱分析(FTIR)、紫外-可见分光光谱(Uv-vis)等技术,深入探讨了该反应体系的作用机理。结果表明:水钠锰矿(δ-MnO2型锰矿物)是一种优良的微波催化剂,在功率400 W和酸性的条件下,微波辅助0.1 g水钠锰矿催化降解50 mL浓度为500 mg/L的亚甲基蓝30 min再静置5 h后,去除率可达到99.7%;体系的作用机理是,微波诱导氧化水钠锰矿,可产生活性氧化物MnO4,进而将体系中的亚甲基蓝氧化分解。     

Effects of I and F codoped TiO2 on the photocatalytic degradation of methylene blue

Nanocrystalline I-F-codoped TiO₂ was prepared by a sol-gel-impregnation method, using tetrabutylorthotitanate in a mixed NH₄I-NH₄F aqueous solution. The as-prepared TiO₂ was characterized with UV-vis diffuse reflectance spectra, X-ray diffraction and nitrogen adsorption. The degradation of methylene blue (MB) over as-prepared TiO₂ in aqueous solution under simulated sunlight irradiation was remarkably enhanced by codoping with I and F. The effects of codoping and calcination temperature on the photocatalytic activity and microstructures were investigated. The photocatalytic activity of as-prepared I-F-codoped TiO₂ was remarkably higher than that of pure, I-doped, and F-doped TiO₂ when the molar ratios of I and F to Ti were kept in the value of 10. The influence of I-F-modification on the photocatalytic activity was discussed by considering the higher surface area, entire anatase phase, effective dopant content, and stronger absorbance of sunlight, corresponding to the higher quantum efficiency. In addition to a complete removal of color, the as-prepared TiO₂ was simultaneously able to oxidize MB and small amounts of intermediates such as formic acid and phenol were detected. After prolonged sunlight irradiation some intermediates almost vanished, and MB appeared to be eventually mineralized to NH₄⁺, NO₃⁻ and SO₄²⁻.     

Characterization and evaluation of ZnO/CuO catalyst in the degradation of methylene blue using solar radiation

Catalysts based on the combination of zinc oxide and copper oxide were synthesized at a 80:20 mass ratio by the Pechini method and calcined at 500, 600 and 700 °C for 1 h. These catalysts were characterized by XRD, SEM, FT-IR, BET, UV-Vis, TGA and XRF. They were subsequently tested for the removal of methylene blue dye by means of heterogeneous catalysis combined with solar radiation through a RCCD experimental design, analyzing the concentrations of H₂O₂ and methylene blue, as well as radiation exposure time and pH. The average crystallite size obtained was of 26.21, 28.21 and 35.91 nm for the respective calcined samples. The XRF was effective in determining the elements present in the catalyst, consisting of 75% zinc oxide and 25% copper oxide. The values of surface area were of 7.54, 7.19 and 3.92 m²/g, respectively. The experimental design showed that the catalyst calcined at 500 °C exhibited the highest removal efficiency (93%) of methylene blue with a dye concentration of 20 mg/L. Despite the need to carry out new studies to optimize the process, results suggest that the application of solar photocatalysis in the treatment of methylene blue with ZnO/CuO is a feasible alternative.