Search

The widespread use of organic dyes that are discharged into wastewater from many sectors continues to be a top environmental issue today. The UV–Visible light driven photocatalytic environmental purification is a highly promising field, and spinel ferrites are the prime applicant for waste water purification. In this work, pure phase cobalt doped Mg–Zn nanoferrites with a composition of Mg0.5Zn0.4Co0.1Fe2O4, Mg0.4Zn0.5Co0.1Fe2O4, and Mg0.5Zn0.5Co0.1Fe1.9O4 were fabricated using economic and facile combustion process. The prepared catalysts were caharcteriazed for structural, optical and magnetic properties. The catalyst Z5C1 exhibits 97.76% crystal violet degradation in 90 min under UV–Visible light. The superior photocatalytic efficiency of the Z5C1 catalyst is attributed to the lowest charge carrier recombination rate and moderate band gap of the catalysts. The scavenging experiments revealed the role of holes as reactive species in the catalytic degradation of crystal violet dye. The reusability investigations and simplicity of magnetic separation of the manufactured catalyst show that catalysts have the potential to degrade crystal violet dye and other organic contaminants. [ABSTRACT FROM AUTHOR]

In this paper, we describe the creation of a moderate band gap Nd-substituted Ni-Zn ferrite as a nano photo catalyst via a simple and cost-effective process of solution combustion. Nd substitution alters the crystallite size, shape, band gap, and magnetic characteristics of Ni-Zn ferrite significantly. Investigations using X-ray diffraction revealed that all samples display a pure phase. The average crystallite size was determined to be between 31.34 and 38.67 nm. On Nd doping, morphology investigations indicated that the shape of nanoparticles changed from approximately spherical to stacked grains. Band gap experiments confirmed the red shift in optical band gap on Nd doping. The synthesized catalysts Ni0.5Zn0.5Fe2O4 (Nd0), Ni0.5Zn0.45Nd0.05Fe2O4 (Nd1), and Ni0.5Zn0.5Nd0.05Fe1.95O4 (Nd2) have been effectively used for the degradation of methylene blue dye under the solar light irradiation. The sample with Nd substitution on Fe sites had the highest methylene blue degradation efficiency. Nd2 photo catalyst degrades the methylene blue dye with a degradation efficiency of 98% in 90 min of solar light irradiation. The photocatalytic activity is triggered by the existence of oxygen vacancies and a mixed valence state of Ni, Fe, and Nd, as confirmed by the XPS investigation. In addition, the investigations on scavenging reveal that the hydroxyl radical is a reactive component in the degradation process. The degradation route has been investigated in relation to the many potential reactions and discovered reactive substances. [ABSTRACT FROM AUTHOR]

Constructing visible-light-active Z-scheme heterojunctions has proven fruitful in enhancing the photocatalytic activity of photocatalysts for superior water clean-up. Herein, we report the fabrication of a CoFe2O4@Bi2O3/NiO (CBN) Z-scheme nanoheterojunction. The obtained CBN heterojunction was used for visible-light-assisted degradation of ofloxacin (OFL) in water. The OFL degradation efficiency achieved by the CBN heterojunction was 95.2% in 90 min with a rate constant of kapp = 0.03316 min−1, which was about eight times that of NiO and thirty times that of CoFe2O4. The photocatalytic activity of a Bi2O3/NiO Z-scheme heterojunction was greatly enhanced by the visible activity and redox mediator effect of the cobalt ferrite co-catalyst. Higher charge-carrier separation, more visible-light capture, and the Z-scheme mechanism in the Z-scheme system were the important reasons for the high performance of CBN. The scavenging experiments suggested ●O2− as an active species for superior OFL degradation. The possible OFL degradation pathway was predicted based on LC-MS findings of degradation intermediate products. The magnetic nature of the CBN helped in the recovery of the catalyst after reuse for six cycles. This work provides new insights into designing oxide-based heterojunctions with high visible-light activity, magnetic character, and high redox capabilities for potential practical applications in environmental treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni 1-x Zn x Fe 2 O 4 inverse spinel ferrite photocatalyst prepared by combustion route. • Dopant determined CB shifting-higher thermodynamic O 2 − generation potential. • Superior photo-degradation of levofloxacin under visible and solar light. • Higher charge separation and transfer capacity-metal redox. • Suitable degradation pathway for levofloxacin proposed. Spinel ferrites with a compatible electronic band structure are always excellent candidates for photo-catalytic environmental detoxification employing visible light and solar energy. However, the potential is not harnessed to its fullest owing to unnerving charge carrier recombination. In this work, we report the synthesis of Ni 1-x Zn x Fe 2 O 4 (x = 0, 0.1, 0.3, & 0.5) mixed spinel ferrites via combustion route. As prepared samples were characterized for phase identification using X-ray diffraction (XRD) and Reitveld refined pattern confirms the formation of single phased cubic structure with a nano-metric crystallite size. The homogeneous distribution of grains and particles is evidenced by shape and size morphological studies. Raman spectroscopy reveals the presence of motion of oxygen in tetrahedral and octahedral voids. The dc electrical resistivity measured using the two probe method is found to be in the range of 107 to 108 Ω-cm. The optical band gap measured for all photo-catalysts resides at 2.11–2.53 eV. The ferrite photocatalyst exhibits high visible absorption, superior charge transfer capacity, and highly suppressed recombination as suggested by electrochemical impedance spectroscopy and photoluminescence results. The change in band structure with variable Zn content was monitored by shifting of conduction and valence bands. The photo-catalyst Ni 0.7 Zn 0.3 Fe 2 O 4 (N2) exhibited 96.8% levofloxacin (LEV) degradation in 90 min of visible light exposure. The effect of parameters such as pH, catalyst dosage, electrolytes and water matrix was analysed in detail. The photo-catalytic degradation rate was enhanced in the presence of persulfate and H 2 O 2. Furthermore, the high magnetic character of the catalysts aids in their retrieval post utilization in catalysis. In terms of band structure analysis, role of dopants, metal redox, and scavenging studies, a suitable photo-catalytic process was proposed. Degradation intermediates discovered by liquid chromatography–mass spectrometry analysis were also recommended as a pathway of degradation. These findings open up exciting possibilities for developing novel solar active photo-catalytic systems based on spinel ferrites for efficient environmental cleanup. [ABSTRACT FROM AUTHOR]

• Mg 0.5 Ni x Zn 0.5-x Fe 2 O 4 spinel ferrite photocatalyst prepared by facile route. • Dopant driven band shifting- Higher potential for O 2 − generation. • Excellent photo-degradation of RB-19 dye under visible and solar light. • Higher migration and reduced recombination-Role of dopant and redox cycles. • Photocatalytic mechanism and degradation route predicted. Focussing on visible light active ferrites for high performance removal of noxious pollutants, we report the synthesis of Mg 0.5 Ni x Zn 0.5-x Fe 2 O 4 (x = 0.1, 0.2, 0.3, 0.4, & 0.5) ferrite nanoparticle for degradation of reactive blue-19 (RB-19). Lattice parameters calculated using intense X-ray diffraction (XRD) peaks and Nelson-Riley plots (N-R plot) are in well agreement with each other. The sample Mg 0.5 Ni 0.4 Zn 0.1 Fe 2 O 4 (M5N4) exhibits best performance with 99.5% RB-19 degradation in 90 min under visible light. Photoluminescence (PL) results confirm that recombination of charge carriers is highly reduced in the photocatalyst. Scavenging experiments suggest that O 2 − radicals were the dominant species responsible for photocatalytic performance. The photocatalytic mechanism was explained in terms of dopant driven shifting of conduction bands and valence bands (calculated by Mott-Schottky plots). The thermodynamic probability of radical generation along with role of redox cycles of metal ions has been discussed in the mechanism. The dye degradation was ascertained by detection of intermediates via mass spectrometry analysis and a possible degradation route was also predicted. The findings in this work provide intriguing opportunities to modify the electronic band structure of spinel ferrites for visible and solar light photocatalytic activity for environmental detoxification. [ABSTRACT FROM AUTHOR]

In the present work, mixed-spinel ferrite anchored onto graphitic carbon nitride (GCN) was synthesized for mineralization of antibiotic pollutant from waste water. A Z-scheme g-C 3 N 4 /Ni 0.5 Zn 0.5 Fe 2 O 4 nano heterojunction was fabricated by three step procedure: pyrolysis, solution combustion and mechanical grinding followed by annealing. The prepared photocatlyst was tested for degradation of Doxycycline (DC) drug under the natural sun light. Results revealed that the prepared heterojunction has maximum degradation efficiency of 97.10% pollutant in 60 min experiment. The Z-scheme heterojunction between g-C 3 N 4 and Ni–Zn ferrite improves the photoinduced charges separation and protection of redox capability and therby increases the photo degradation efficiency. The scavenging experiments suggested that O 2 −● and h+ as main active species responsible for degradation of the antibiotic. In addition, the dopant variation can drive the shists in band gap and energy band positiong too which makes then excellent candidates for synthesizing tunable heterostructures with organic semiconductors. The work focusses on designing and developing of saimpler but efficient magnetic heterojunctions with superior redox capability for solar powered waste water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Co0.6Zn0.4Fe2O4 nanomagnetic system is prepared by solution combustion method. The powder sample is characterized by X-ray diffraction (XRD), transmission electron microscope analysis (TEM), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, and superconducting quantum interference device (SQUID; at low and room temperatures). The average crystallite sizes of the prepared samples obtained from XRD is 22 nm, which is well confirmed by the size obtained from TEM. The magnetic study shows that sample is ferromagnetic at room temperature. This result is also supported by Mössbauer spectrum obtained at room temperature. [ABSTRACT FROM AUTHOR]

• Novel Mg 0.5-x Cu x Zn 0.5 Fe 2 O 4 spinel ferrite prepared. • Dopant induced shifts in conduction bands-high potential. • High performance removal of carbamazepine under visible light. • ●O 2 – as active species. • High charge separation via metal redox cycle and dopants. Environmental friendly and robust Mg 0.5-x Cu x Zn 0.5 Fe 2 O 4 (x = 0, 0.01 & 0.02) nano-photocatalyst was prepared by facile solution combustion method for high performance photocatalytic removal of carbamazepine (CBZ). Mg 0.3 Cu 0.2 Zn 0.5 Fe 2 O 4 catalyst shows 94.3% degradation in 90 min visible exposure and 78.2% total organic carbon (TOC) removal. The Cu dopant driven conduction band shifting to more negative side leads to improved ●O 2 – formation supported by electron spin resonance (ESR) probe. The dopants and metal redox cycles lead to higher visible absorption and reduced recombination boosting the CBZ removal. The degradation pathway and photocatalytic mechanism is also predicted. [ABSTRACT FROM AUTHOR]

Fabricating magnetically recoverable solar-active photocatalysts with high performance capabilities for removal of recalcitrant and emerging pollutants has gained worldwide attention. Especially pharmaceutical pollutants as sulfonamides drugs which are now frequently detected in water systems are hard to remove because of their resistance to microbial and biological oxidation. This laboratory scale experiment presents synthesis of Mg substituted Zn nano-ferrite (Zn 1-x Mg x Fe 2 O 4) (x = 0, 0.2, 0.4) by facile modified sol-gel technique for sulfadiazine (SDZ) degradation. Effect of Mg doping on the zinc ferrite were investigated in this work which was analyzed by Transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. The UV-diffuse reflectance spectroscopy studies reveal higher visible absorption extending to longer wavelengths. The VB of the ferrite catalyst shifts to 2.30 eV in substituted ferrite M2Z8 (x = 0.2) capable of hydroxyl radicals generation from H 2 O, which is difficult in parent ferrite without any Mg substitution. The electrochemical impedance spectroscopy and photo-current response analysis also reveal low impedance, higher charge flow and separation in case of M2Z8 catalyst which is reflected in the 99.1% SDZ degradation in 90 min with 73.2% total organic carbon removal in 120 min. Scavenging experiments confirm that hydroxyl radicals are main active species involved in degradation with Mg2+ and Fe3+ catalyzing the generation of hydroxyl radicals by undergoing redox process. LC-MS and TOC analysis confirm the drug mineralization. The work aims at fabricating solar active tunable photocatalysts for photo-degradation and mineralization of pharmaceutical pollutants using cost-effective approach. Unlabelled Image • Magnetic solar active nano-Zn 1-x Mg x Fe 2 O 4 photocatalyst-facile synthesis • Mg enhances the degradation rate and radical generation. • Shifting of CB and VB-Changed dynamics of radical generation • High performance degradation of sulfadiazine drug-visible and solar light • Mechanism elucidation, high mineralization and magnetic recovery [ABSTRACT FROM AUTHOR]

Al doped Mn ferrite, MnAl x Fe 2-x O 4 (x = 0.1, 0.2, & 0.3), nanoparticles were synthsized by facile and simple solution combustion route. Effect of Al3+ ions substitution on the structural, optical, electrical and magnetic properties were explored. X-Ray diffraction (XRD) results confirm the formation of pure cubic phase for all the synthesized nanoparticles having spinel structure. Various structural parameters like crystallite size, lattice parameter, site radii and bond lengths were estimated from XRD data. For the strain analysis and consideration of contribution of every peak in XRD data, W-H and N-R plots were analysed. Scannining electron microscopy (SEM) revealed the compact surface morphology with grain size in nano meter range. FTIR spectra confirmed the presence of metal stretching vibrations at tetrahedral and octahedral sites for all MnAl x Fe 2-x O 4 nanoparticle compositions, which is typical of spinel ferrites with FCC structure. Raman spectroscopy helped in analysing metal stretching vibrations of the synthesized samples and obtained raman modes were found to be as predicted by group theory. Dielectric constant decreases with increase in frequency reflecting the normal behaviour of the ferrites. Dielectric loss also followed the same trend. Both the behaviours have been explained in view of Koop׳s theory and Maxwell–Wagner polarization-model. The synthesized ferrite samples exhibited the soft magnetic nature as confirmed by vibrating sample magnetometer. The room temperature hysteresis curves indicate the decrease in saturation magnetization as well as retentivity with the increase in Al3+ ions doping. The decrease in magnetic moment values have been explained on the basis of cation preference for the sites and also on weakening of exchange interaction upon aluminium doping. • Al3+ substituted MnFe 2 O 4 nanoferrites are synthesized for the first time by SC method. • Magnetic parameters suggest the utility for electromagnet application. • Low values of dielectric loss tangent are obtained. [ABSTRACT FROM AUTHOR]