Ferrite Photocatalyst Research Articles

Development of cost effective, solar light active Cu1-xCaxFe2O4 nanocomposite catalysts for water treatment

Novel, efficient and magnetically recyclable calcium substituted copper ferrite photocatalysts were synthesized via a facile green approach. As prepared Cu1-xCaxFe2O4 composites were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electronic microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS) and UV–Vis spectrophotometer. The result shows that there is an enhancement in electron transfer and charge separation efficiency of calcium substituted copper ferrites leading to a significant improvement in photocatalytic efficiency. As prepared samples shows high visible light absorption which favors catalytic activity and also shows good magnetic separation for reuse. UV–Vis spectrophotometer was used for the destruction of model organic pollutant. Under natural sun light irradiation the as prepared samples exhibit superior photocatalytic activity toward malachite green (MG). The model organic pollutant inactivation mechanism was investigated in a scavenger study, and •O2, H2O2, and h+ were identified as the major reactive species for organic pollutant inactivation. The calcium substituted copper ferrite exhibit excellent stability and reusability. The experimental results indicate that calcium substituted copper ferrites have great potential in large scale photocatalytic disinfection operations.

Studies on the Preparation and Photocatalytic Performance of Bismuth Ferrite

Iron oxide and bismuth oxide powder are synthesized by the liquid phase precipitation method. Then a certain proportion of iron oxide, bismuth oxide and sodium chloride are mixed and ground to prepare the bismuth ferrite precursor by the molten salt method. The bismuth ferrite precursors are calcined at different temperatures to obtain bismuth ferrite photocatalyst. By studying the degradation performance of bismuth oxide, iron oxide and bismuth ferrite photocatalysts for methyl orange dyes, the best conditions for the degradation of methyl orange dyes by bismuth ferrite photocatalysts are found. The experimental results show that the bismuth ferrite prepared by calcining at 750°C has the best degradation. Compared with a single oxide, the photocatalytic performance of bismuth ferrite is better.

Effect of Precursors on the Growth and Physiochemical Properties of Bio-mimetic ZnFe2O4 Nanocomposites for Photoelectrochemical Application

Zinc ferrite (ZnFe2O4) photocatalysts have been prepared with different types of zinc precursors using the bio-mimetic synthesis method. The kapok fibre (Ceiba pentandra (L.) Gaertn) used as a sacrificial template. The physiochemical of prepared bio-mimetic materials were carried out thoroughly in this work. The FESEM analysis in mimetic zinc ferrite catalysts shows a distinctly different structural transition under different precursors conditions. The acetate precursor formed a hollow tubular structure while other precursors formed a hierarchal fibril structure. X-ray diffraction analysis showed a distinctly different phase transition while UV-Vis spectroscopy recorded variable optical properties beneath different precursor conditions. The EDX and ATR-FTIR spectroscopy confirmed the formation of the pure composite after the annealing process. Different type of precursors that used have leads to tuneable of the magnetic properties of the prepared materials. Electrophoretic deposition (EPD) method has been used to fabricate the synthesized materials as photo-electrodes on the FTO substrate then evaluated for photoelectrochemical (PEC) application. Changing the precursors in the preparation method show a significant effect on physicochemical and PEC performance. The morphology and surface structure of the prepared catalysts are correlated with the alteration of the precursors, then attributed to the charge transfer properties of the photocurrent density in PEC system. The bio-templated zinc ferrite catalysts are promising photoanode in the photocatalytic activities. It is interesting to note that the various forms of multi-structure such as hollow fibril core-shell offers an enormous impact in designing active photocatalyst with superior performance.

Studies on the Synthesis and Photocatalytic Properties of Zinc Ferrite Materials

Zinc ferrite precursors are prepared by coprecipitation method using zinc nitrate and ferric nitrate as reactants, monohydrate ammonia and citric acid as precipitants and dispersants respectively. And zinc ferrite precursors are calcined at high temperature to obtain zinc ferrite photocatalysts at different temperatures(350°C, 450°C, 550°C). Methylene blue is used as substrates. The quality of the catalyst, the type of catalyst and the temperature of calcining are measured to study the photocatalytic performance. The results show that the preparation of zinc ferrite under 450°C has an optimal effect on the degradation of methylene blue dye. Compared with iron oxide and zinc oxide, the photocatalytic properties of zinc ferrite are superior to that of single oxide.

Novel g–C3N4–carbon dots-aggregation/ferrite hybrid heterojunction photocatalyst with excellent visible-light-driven photodegradation performance toward organic pollutants

Abstract In water pollution treatment, photocatalytic technology is attracting intensive attention and photocatalysts have extensively been focused on, but high efficiency still remains expected. Herein, a spherical uniformly-dispersed aggregation photocatalyst of carbon dots (CDs) with g-C3N4 was hydrothermally synthetized through employing glucose as carbon sources for CDs and employing cyanuric chloride and dicyandiamine for the formation of g-C3N4, and then coupling with 10 wt% of new hydrothermal ferrite photocatalyst Ni0.1Co0.9Fe2O4 to fabricate a novel g–C3N4–CDs-aggregation/ferrite hybrid heterojunction photocatalyst through post sintering process. Various techniques including SEM, HRTEM, XRD, XPS, UV–vis and EIS spectroscopy were employed to analyze the as-fabricated ternary hybrid photocatalyst. Due to the uniformly-dispersed modification of CDs to g-C3N4 and the hybrid heterojunction between g–C3N4–CDs aggregation with Ni0.1Co0.9Fe2O4, the targeted hybrid photocatalyst presented excellent visible-light-driven photocatalytic degradation efficiency towards methylene blue, with a high degradation ratio of up to 96.6% in 1 h, corresponding to a photodegradation rate constant k value of up to 0.05127 min−1. Our targeted hybrid photocatalyst shows good structural and photocatalytic stability and electronic radical (e−) is the main active species during photocatalytic process.

Photocatalytic heterostructures-based BiFeO3 embedded liquid natural rubber (LNR) for highly removal of cationic dye under direct sunlight

Abstract In this study, the composite consists of bismuth ferrite (BiFeO3) photocatalyst embedded into macroporous liquid natural rubber (LNR) matrices was fabricated to assess the removal efficiency of methylene blue (MB) dye under direct sunlight. The structural properties and morphology of LNR-BiFeO3 composite were thoroughly characterised using spectroscopic and microscopic methods. X-Ray diffractogram of the composite demonstrated successful inclusion of BiFeO3 into the LNR network. During solar-driven photocatalytic activity of LNR-BiFeO3, the effects of selected operating parameters on removal efficiency, such as catalyst dose, irradiation time, initial dye concentration, and solution pH, were determined. At optimum catalyst dose (0.15 g BiFeO3) and irradiation time (3 h), degradation of 10 ppm MB was remarkably efficient as 98.9 + 0.09 % have been successfully discarded from the system. The composite had managed to degrade up to 75 ppm MB with degradation efficiency exceeding 89.0 %. In order to investigate the mechanism of MB removal using LNR-BiFeO3, monitoring of removal mode, kinetics and scavenger study were carried out. The outcomes revealed that MB removal did fit well with Langmuir-Hinshelwood kinetic model, in which BiFeO3 (Ebg = 1.76 eV) is responsible for photodegradation process using OH―, O2― and h+ with assistance of adsorption by the composite. The composite could be reused for five cycles without any post-treatment or separation step, and most importantly, no significant loss noted in its activity. This eco-friendly and economical approach will render new opportunities for this advanced photocatalyst as great potential in environmental remediation for wastewater treatment.

Development of heterojunction in N-rGO supported bismuth ferrite photocatalyst for degradation of Rhodamine B

A nitrogen-doped graphene oxide (N-rGO) supported bismuth ferrite (BiFeO3/N-rGO) exhibited a superior photocatalytic activity toward degradation of Rhodamine B, which was synthesized by the sol–gel method followed by hydrothermal method. Catalysts were characterized by HR-TEM, X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared (FT-IR), Diffused reflectance spectroscopy (DRS), Electrical impedance spectroscopy (EIS), Photoluminescence (PL) and Mott-Schottky (M−S) analyses. Photoluminescence (PL) spectroscopy confirmed that nitrogen-doped graphene efficiently inhibits recombination of electron-hole pairs in BiFeO3/N-rGO. FTIR, DRS, and XPS analyses confirmed a chemical interaction between graphene and bismuth ferrite leading to the formation of heterojunction. This interaction led to the enhancement of charge transfer for photocatalytic activity. EIS and M−S analyses showed low resistance for charge mobility, high charge carrier density, and high band bending in BiFeO3/N-rGO. A fivefold improvement was observed in the photocatalytic activity of Rhodamine B by using the catalyst as compared to that of bare bismuth ferrite.

Fabrication of Ce3+ substituted nickel ferrite-reduced graphene oxide heterojunction with high photocatalytic activity under visible light irradiation

In the current investigation, graphene (rGO)-supported cerium substituted nickel ferrite (NiCeyFe2-yO4 y = 0.05) photocatalyst was prepared via two-step wet chemical approach. The resulting NiCeyFe2-yO4/rGO nanocomposite exhibited excellent photocatalytic performance and stability. Moreover, the photocatalytic activity of NiCeyFe2-yO4/rGO nanocomposite was also investigated comparatively with NiCeyFe2-yO4 nanoparticles. As compared to the NiCeyFe2-yO4 nanoparticles, NiCeyFe2-yO4/rGO nanocomposite showed superior photocatalytic efficiency and recycling stability for MB degradation, which is two times that of bare NiCeyFe2-yO4 nanoparticles. After visible light irradiation for 70 min, 94.67 % of MB dye was removed by NiCeyFe2-yO4/rGO nanocomposite whereas only 50 % of MB dye was removed by NiCeyFe2-yO4 nanoparticles. The increase in photocatalytic performance is mainly ascribed to formation of NiCeyFe2-yO4/rGO heterojunction which not only assist in separation of photo-induced charge carriers, but also sustain a strong redox ability. Moreover, the photo-corrosion of NiCe0.05Fe1.95O4 nanoparticles is inhibited through transfer of photo-induced electrons of NiCe0.05Fe1.95O4 nanoparticles to rGO. A possible photo-degradation mechanism based on reactive species trapping experiments has been proposed. The effect of various factors like pH, temperature and catalyst dosage has also been explored. Facile synthesis method, excellent photocatalytic performance for organic pollutants and superior reusability suggest that NiCeyFe2-yO4/rGO photocatalyst possesses high potential for large-scale pollutant treatment.

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M\u2009=\u2009Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

In this study, we report a surfactant-mediated synthesis of ferrites (MFe2O4: M = Co, Ni, Cu, Zn) using the co-precipitation-oxidation method. The band gap calculated from UV-Visible diffuse reflectance spectra were found in the range of 1.11–1.81 eV. These ferrite nanocatalysts were studied for the photocatalytic degradation of multiple organic dyes in a 32 W UV-C/H2O2 system. All the four ferrites showed an excellent dye degradation rate in the range of 2.065–2.417 min−1 at neutral pH. In the optimized condition, NiF was found to degrade 89%, 92%, 93%, and 78% of methylene blue, methyl orange, bromo green, and methyl red, respectively within 1 min of UV-irradiation. A 40% TOC removal was recorded after 5 min of degradation reaction, which increased to 60% after 50 min. Mechanism elucidated by scavenger studies and fluorescence spectroscopy revealed that •OH and holes were the primary reactive radicals responsible for the degradation process. Ferrite photocatalysts showed an insignificant performance loss in seven consecutive cycles. The photocatalyst was found efficient in the presence of a high concentration of salts. Thus, it was concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.

Environmentally friendly synthesized and magnetically recoverable designed ferrite photo-catalysts for wastewater treatment applications

Fenton processes are promising wastewater treatment alternatives for bio-recalcitrant compounds. Three different methods (i.e., reverse microemulsion, sol-gel, and combustion) were designed to synthesize environmentally friendly ferrites as magnetically recoverable catalysts to be applied for the decomposition of two pharmaceuticals (ciprofloxacin and carbamazepine) that are frequently detected in water bodies. The catalysts were used in a heterogeneous solar photo-Fenton treatment to save the cost of applying high-energy UV radiation sources, and was performed under a slightly basic pH to avoid metal leaching and adding salts for pH adjustment. All the developed catalysts resulted in the effective treatment of ciprofloxacin and carbamazepine in both synthetic and real domestic wastewater. In particular, the sol-gel synthesized ferrite was more magnetic and more suitable for reuse. The degradation pathways of both compounds were elucidated for this treatment. The degradation of ciprofloxacin involved attacks to the quinolone and piperazine rings. The degradation pathway of carbamazepine involved the formation of hydroxyl carbamazepine and dihydroxy carbamazepine before yielding acridine by hydrogen abstraction, decarboxylation, and amine cleavage, which would be further oxidized.

Synthesis of multiferroic BiFeO3 microcrystals for photocatalytic activity and stability performance

Bismuth ferrite (BiFeO3) photocatalysts were synthesized via simple hydrothermal technique, in which the morphology and size were tailored by using different KOH concentrations in precursor solution. The phase evolution, particle size and morphologies reported with respect to different concentrations of KOH as Mineralizer. And the photocatalytic activity and stability test of prepared samples was evaluated by degrading rhodamine B (Rh B) under visible light irradiation. 4 M KOH concentrations is the optimum condition to get single phase BiFeO3 and degradation efficiency was improved. The material shows strong stability and photocatalytic activity even after five recycling tests without losing it’s properties.

Magnetic properties and photocatalytic mechanism of magnetic separable M-type strontium ferrite photocatalyst

M-type strontium ferrite photocatalysts were successfully synthesized by three different methods including combustion assisted sol-gel method, microwave irradiation assisted sol-gel method and conventional sol-gel method. The phase structure, surface morphology, optical properties, magnetic properties and photocatalytic activity of the M-type strontium ferrite photocatalyst are strongly dependent on the synthetic route. The effects of the irradiation time, catalyst loading, initial dye concentration and pH value on the photocatalytic activity of the M-type strontium ferrite photocatalyst have been systematically studied. The M-type strontium ferrite photocatalyst synthesized by a microwave irradiation assisted sol-gel method exhibits an excellent optical properties, magnetic properties and photocatalytic activity. The optimum irradiation time, catalyst loading, initial dye concentration and pH value of the M-type strontium ferrite photocatalyst is 180 min, 3 g l−1, 25 mg l−1 and 10, respectively. The recycle experiments show that the M-type strontium ferrite photocatalyst has good magnetic separation recovery ability. The hydroxyl radicals (•OH) play a key role for the M-type strontium ferrite photocatalyst for photocatalytic degradation of the rhodamine B dye.

Synthesis of Titania Doped Copper Ferrite Photocatalyst and Its Photoactivity towards Methylene Blue Degradation under Visible Light Irradiation

This paper reports the photocatalytic decomposition of methylene blue (MB) over titania doped copper ferrite, CuFe2O4/TiO2 with 50 wt% loading, synthesized via sol-gel method. The synthesized photocatalyst was characterized by X-ray diffraction, UV-vis diffuse reflectance, and photoluminescence, Mott-Schottky (MS) analysis and linear sweep voltammetry (LSV). The catalyst loadings were varied from 0.25 – 1.0 g/L and the optimum catalyst loading found to be 0.5 g/L. At the optimum loading, the conversion achieved was 83.7%. The other loadings produced slightly lower conversions at 82.7%, 80.6% and 80.0%, corresponding to 0.25, 1 and 0.75 g/L after 3 hours of irradiation. The study on the effect of initial concentration indicated that 20 ppm as the optimum concentration, tested with 0.5 g/L catalyst loading. The spent catalyst was used for the recyclability test and demonstrated a high longevity with a degradation efficiency less than 6 % for each time interval. The novelty of this study lies on the new application of photocatalytic material, CuFe2O4/TiO2 on thiazine dye that shows remarkable activity and reusability performance under visible light irradiation.

Perovskite-type LaFeO3: Photoelectrochemical Properties and Photocatalytic Degradation of Organic Pollutants Under Visible Light Irradiation

Perovskite-type oxides lanthanum ferrite (LaFeO3) photocatalysts were successfully prepared by a facile and cost-effective sol-gel method using La(NO)3 and Fe(NO)3 as metal ion precursors and citric acid as a complexing agent at different calcination temperatures. The properties of the resulting LaFeO3 samples were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (IR), transmission electron microscopy (TEM), N2 adsorption/desorption and photoelectrochemical tests. The photoactivity of the LaFeO3 samples was tested by monitoring the photocatalytic degradation of Rhodamine B (RhB) and 4-chlorophenol (4-CP) under visible light irradiation, the highest photocatalytic activity was found for LaFeO3 calcined at 700 °C, which attributed to the relatively highest surface area (10.6 m2/g). In addition, it was found from trapping experiments that the reactive species for degradation were superoxide radical ions (O2−) and holes (h+). Photocurrent measurements and electrochemical impedance spectroscopy (EIS) proved the higher photo-induced charge carrier transfer and separation efficiency of the LaFeO3 sample calcined at 700 °C compared to that that calcined at 900 °C. Band positions of LaFeO3 were estimated using the Mott-Schottky plots, which showed that H2 evolution was not likely.

Sunlight photocatalytic performance of Mg-doped nickel ferrite synthesized by a green sol-gel route

Abstract We report an environmentally friendly synthetic strategy to synthesize new nickel ferrite and Mg doped nickel ferrite photocatalysts under modified green sol-gel route in which Aloe Vera gel acts as a natural template. The crystalline phase, surface morphology and size of the prepared photocatalysts were characterized by PXRD, SEM, TEM and HRTEM analysis. The energy band gap of the nanoparticles (NPs) can be tuned in the range of 2.55–2.34 eV by varying the dopant concentration. The photoluminescence analysis indicates that the present NPs are an effective white component in display applications. These synthesized NPs were used for photocatalytic decomposition of recalcitrant pollutants in aqueous media under sunlight irradiation. Among investigated samples, the NiFe2O4: Mg2+ (1 mol %) exhibits the highest photocatalytic efficiency for the decomposition of recalcitrant pollutants, which is higher than that of the commercial P25. This enhancement in photocatalytic performance can be mainly attributed to the balance between the parameters, crystallanity, band gap, morphology, crystallite size, defects, dopant amount and combined facets of photocatalysis. It opens a new window to use this simple greener route to synthesize bi-functional NPs in the area of photocatalysis particularly waste water treatment and display applications.

Enhanced photodegradation of methylene blue with alkaline and transition‐metal ferrite nanophotocatalysts under direct sun light irradiation

It is highly desired to synthesize low‐cost photocatalysts for the degradation of colored dyes to safeguard our environment for the future generations. Here, we report an extremely efficient and low‐cost synthesis of alkaline earth and transition‐metal ferrite photocatalysts (MgFe2O4, CaFe2O4, BaFe12O19, CuFe2O4, and ZnFe2O4) from their chloride salts and their applications for the degradation of methylene blue (MB) dye under UV–visible and direct sunlight irradiation. The as‐prepared photocatalysts displayed enhanced photoactivities under both conditions of irradiation. After calcination at 600°C, the photocatalytic degradation increased significantly, and 96 and 85% MB was removed with ZnFe2O4 under UV–visible and direct sunlight irradiation, respectively. Moreover, large amounts of hydroxyl free radicals were produced under both irradiation conditions, which participated in the degradation of MB. The enhanced photodegradation activities of these photocatalysts are attributed to their extended visible light absorption and low bandgaps. This work will provide a feasible route to the synthesis of efficient and low‐cost photocatalysts to utilize sunlight for environmental remediation.

Enhanced Photocatalytic Activity and Biosensing of Gadolinium Substituted BiFeO3 Nanoparticles

AbstractGadolinium (Gd3+) substituted bismuth ferrite (BF) photocatalysts were synthesized using sol‐gel method and the effect of Gd3+ substitution was investigated on the structural, optical and surface properties of Gd3+ substituted BF nanoparticles. Different techniques such as X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM) with Selected area electron diffraction pattern (SAED), Fourier transform infrared spectra (FTIR), ultraviolet‐visible diffuse reflection spectra (UV‐DRS), field emission scanning electron microscopy (FESEM), Brunauer‐Emmett‐Teller (BET), and photoluminescence spectra (PL) were employed to characterize the nanoparticles. Compared to nascent BF, the Gd3+ substituted BF nanoparticles showed improved long‐range ordering, smaller pore diameter, higher porosity and redshift of the band gap. These properties were responsible for their improved photocatalytic activity, when tested for the photodegradation of organic dyes. It was found that 3 % Gd3+ substituted BF nanoparticles exhibited enhanced the photocatalytic activity of indigo carmine dye with a degradation ranging from 34 % to 69 %, while for Congo red dye the degradation varied from 37 % to 73 % under the visible light. Furthermore, bio‐sensing properties of BF materials were improved as detected by the uric acid using cyclic voltammogram technique.

A co-catalyst free, eco-friendly, novel visible light absorbing iron based complex oxide nanocomposites for enhanced photocatalytic hydrogen evolution

This study exposes enhanced hydrogen evolution capability of Mg doped Calcium ferrite nanocomposite without any co-catalysts under natural sunlight irradiation. Structural studies of this chemically (sol-gel) synthesised nanocomposite revealed the co-existence of two or three complex oxide ferrites along with iron oxide phases. Optical studies confirmed its narrower bandgap suitable for visible light absorbance. Elemental analysis shows the presence and oxidation state of elements in all undoped and doped calcium ferrite photocatalysts. Hydrogen evolution rate of undoped and Mg doped Calcium ferrite calcined at three different temperatures is discussed. It was found that doping of Mg in calcium ferrite resulted in 19.6 times higher hydrogen evolution ratethan undoped calcium ferritedue to the co-operative assistance of each individual phase present in the nanocomposite.

Magnetically Separable Rice Husk Char-Supported Nickel Ferrite Photocatalyst with High Photoactivity under Visible-Light Irradiation

A specific strategy is presented for the preparation of a NiFe2O4-rice husk char (RHC) nanocatalyst with different RHC contents. The recombination of nano-NiFe2O4 with RHC leads an opposite transformation of the unreactive NiFe2O4 to an upper active photocatalyst, which can be used for the photodegradation of methylene blue in the presence of H2O2 under visible light. In comparison with neat NiFe2O4 as a catalyst, the NiFe2O4-RHC plays a dual function as the photocatalyst for both the electrochemical photodegradation of methylene blue and the producer of the important oxidant hydroxyl radical from the electrochemical dissociation of H2O2 under visible-light irradiation. The photocatalyst displays such excellent stability in the reaction that it can be magnetically separated and recycled for more than five consecutive cycles without any significant loss of activity and degradation.

Scalable Green Method to Fabricate Magnetically Separable NiFe2O4-Reduced Graphene Oxide Nanocomposites with Enhanced Photocatalytic Performance Driven by Visible Light

A reduced graphene oxide (RGO)-supported nickel ferrite (NiFe2O4) photocatalyst was prepared by a simple mechanical ball-milling method. No additional solvents, toxic chemical reductants, or ultrasonic or high-temperature heat treatments were needed. The exfoliation and reduction of graphite oxide (GO) and the in situ anchoring of NiFe2O4 nanoparticles on graphene sheets were fulfilled simultaneously under the strong shear force. The structure characterization shows that the NiFe2O4 nanoparticles were uniformly dispersed on RGO sheets. Amazingly, after coupling with an appropriate amount of RGO, the photocatalytically inert NiFe2O4 exhibited superior photodegradation performance and recycling stability for the degradation of organic pollutant under visible-light irradiation at room temperature. It suggested that the synergistic effect between RGO and NiFe2O4 improved the photocatalytic performance of the composite. Moreover, the NiFe2O4-RGO is magnetically separable for recycling. Hopefully, this work cou...