Photodegradation Of Malachite Green Research Articles

Efficient photocatalytic degradation of malachite green dye from wastewater using facilely synthesized ternary ZIF-8/Ag/Ag2S nanocomposite: Optimization by RSM (CCD)

The current study compares the photocatalytic potential of zeolitic imidazolate framework-8 (ZIF-8) with ZIF-8 nanocomposites doped with two forms of silver (referred to as AgNPs/ZIF-8 and AgNPs/Ag2S/ZIF-8). Their physicochemical characteristics were evaluated using Fourier-transform infrared, X-ray diffraction, energy-dispersive X-ray, Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), photocurrent density, Mott-Schottky, and Brunauer Emmett Teller techniques. The photocatalytic activity of the composites was assessed for degradation of malachite green (MG) under visible light irradiation in a solar-based staircase photoreactor for the first time. The optimization of the photodegradation process was achieved by employing central composite design, 0.020 g of AgNPs/ZIF-8 and ZIF-8photocatalyst (in 20 ml of solution), MG Concentration of 7 mg/l, pH of 8, and the irradiation time of 50 min. The predicted model had R2 and R2adj correlation coefficients of 0.987 and 0.975 respectively, which showed experimental results were very close to the predicted values. The results indicated remarkable efficiency in both degradation and mineralization, achieving the degradation rate of up to 98.6 %, a high-rate constant value of 0.0701 min-¹, and an 80 % mineralization efficiency. AgNPs/Ag2S/ZIF-8 exhibited superior photocatalytic performance in comparison to both AgNPs/ZIF-8 and ZIF-8. Different scavengers were used in the experiment and demonstrated that O2− played a crucial role in the photodegradation of MG. Moreover, the nanocomposite AgNPs/Ag2S/ZIF-8 exhibited robust stability and could be repeatedly utilized up to five cycles without notable decline in efficacy, rendering it an environmentally sustainable photocatalyst with promising prospects for industrial utilization.

Synthesis of novel TiO2/CeFeO3 heterojunction using Mugwort (Artemisia vulgaris) leaves extracts with enhanced photocatalytic activity under visible light irradiation

TiO2 is a low-cost and biocompatible material with high oxidizing ability. However, their photocatalytic activity is limited to UV light irradiation. In this research, for the first time, a novel TiO2/CeFeO3 heterojunction was synthesized by the green synthesis method using an aqueous fraction of Artemisia vulgaris leaf extracts. TiO2/CeFeO3 shows enhanced photocatalytic performance under visible light irradiation. The vibrational, structural, optical, and compositional properties of TiO2/CeFeO3 were characterized. The as-prepared TiO2/CeFeO3 has spherical-shaped particles and shows a significantly diminished bandgap energy (3.25 eV to 2.75 eV). The photocatalytic performance of TiO2/CeFeO3 was investigated to degrade malachite green (MG) with an efficiency of up to 93.53% under its optimum dose. TiO2/CeFeO3 shows stable photocatalytic performance until the fourth cycle. The kinetics of the photodegradation of MG followed the pseudo-first-order reaction with a rate constant (kapp) of 2.14×10−2 min−1. The enhanced photocatalytic activity of TiO2/CeFeO3 was attributable to the creation of heterojunction, which suppresses the recombination rate of photogenerated electron-hole validated by the photoluminescence analysis. This work presents an eco-friendly approach to synthesizing novel heterojunction material with enhanced photocatalytic dye degradation.

The study of copper oxide nanoparticles based on the pH varying during propolis-mediated synthesis: structure, optical properties, UV-block ability, and malachite green photodegradation

The study of copper oxide nanoparticles based on the pH varying during propolis-mediated synthesis: structure, optical properties, UV-block ability, and malachite green photodegradation

Removal of malachite green from water: Comparison of adsorption in a residue-derived AC versus photocatalytic oxidation with TiO2 and study of the adsorption-photocatalysis synergy

The literature rarely compiles studies devoted to the removal of pollutants in aqueous media comparing adsorption and photocatalytic degradation, and does not pay enough attention to the analysis of combined adsorption-photocatalytic oxidation processes. In the present manuscript, the removal of malachite green (MG) from aqueous solutions has been investigated in three different sustainable scenarios: i) adsorption on activated carbon (AC) derived from a residue, luffa cylindrica, ii) photocatalytic oxidation under simulated solar light using titanium dioxide (TP) and iii) combined adsorption-photocatalytic oxidation using TP-AC (70/30 wt./wt.) under simulated solar light. The study has revealed that in the three scenarios and studied conditions, the total removal of this endocrine-disrupting dye from the solution takes place in the assayed time, 2 h, in some cases just in a few minutes. MG adsorption in the AC is a very fast and efficient removal method. MG photocatalytic oxidation with TP also occurs efficiently, although the oxidized MG is not totally mineralized. MG removal using the TP-AC composite under simulated solar light occurs only slightly faster to the MG adsorption in the AC, being adsorption the dominating MG removal mechanism for TP-AC. Thus, more than 90% of the removed MG with TP-AC under simulated solar light is adsorbed in this carbon-containing composite. The obtained results highlight the interest in adsorption, being the selection of the most suitable removal method dependent on several factors (i.e., the cost of the AC regeneration, for adsorption, or the toxicity of the intermediate oxidation species, for photooxidation).Paying attention to MG photooxidation with TiO2, comparison of two working photodegradation schemes shows that the direct photodegradation of MG from solution, avoiding any initial dark equilibrium period, is more efficient from a time perspective. The use of scavengers has proved that MG photodegradation occurs via an oxidation mechanism dominated by superoxide anion radicals.

Developing the novel model for kinetics and mass transfer in sun-light-driven photodegradation of malachite green over Bi2O2CO3/CuBi2O4 (50:50) flower-like nanophotocatalyst: Machine and deep-learning algorithms

The flower-like Bi2O2CO3-CuBi2O4 (50:50) nanocomposite was fabricated using the sono-hydrothermal procedure, including the nanosheets as Bi2O2CO3 and spherical clusters as CuBi2O4), and was employed for photodegradation of malachite green with the high-concentration under the visible light region that the high elimination percentage of nearly 91.6% was achieved in 180 min. Various analyses were carried out using XRD, DRS, BET-BJH, FESEM, TEM, and pHpzc techniques over Bi2O2CO3-CuBi2O4 (50:50). Furthermore, for the modeling of the photodegradation process, simplifying the complexity of the photodegradation process, and the influence of operating parameters on the process, advanced intelligent techniques, including deep learning algorithms and machine learning algorithms such as Gaussian Process Regression (GPR) and Support Vector Machines (SVM) were employed that was achieved remarkable accuracy with coefficients of determination (R2) exceeding 0.99. In these models, the initial concentration of MG, pH solution, photocatalyst loading, and process time served as inputs, while the conversion of MG was the output. Subsequently, based on the AOP fundamentals (active species and radicals), a novel kinetic model was developed, and the optimization of kinetic parameters for our novel kinetic model using the Genetic algorithm was conducted (R2 =0.9862). In continuation, to explore other aspects and kinetic parameters for a comprehensive understanding of the complexity of the process, the power polynomial model (R2 =0.9446) and previously developed kinetic models were investigated using the Genetic algorithm. Besides, a novel modelling approach was introduced, employing a combination of Computational Fluid Dynamics (CFD) and Genetic Algorithm (GA) techniques. This innovative method was utilized to accurately estimate the physical properties of synthetic nanophotocatalysts without the need for traditional laboratory analysis based on the transport phenomena. Furthermore, with this model, we successfully have determined mass transfer parameters in both the adsorption and photodegradation processes. Moreover, this model enabled the determination of the surface reaction rate of the nanophotocatalyst −Rdye=(8.9874e−8)Cpr;r=Rp1.0381 [ug/(cm2.s)], contributing to a thorough comprehension of photocatalytic activity with high accuracy.

Utilization of Synthesized Copper Ferrite/Calcium Alginate Nanocomposite for Adsorption and Photocatalytic Degradation of Malachite Green

In this article, the effectiveness of two different application methods (photocatalytic degradation and adsorption) onto the created solid nanomaterials for the removal of malachite green (MG) was investigated. Copper ferrite nanoparticles (CF) and copper ferrite/calcium alginate composite (CG) were synthesized as two studied solid samples. By using XRD, TGA, FTIR, DRS, nitrogen adsorption/desorption isotherm, pHPZC, SEM, and TEM, the physicochemical and morphological properties of the solid samples were tested. Sample dose, pH, initial MG concentration, shaking time, ionic strength, UV light power, and temperature were the key experimental parameters that were established. The obtained results demonstrated that at 40 °C, CG reached a greater adsorption capacity (297.62 mg/g). The spontaneous, endothermic, and advantageous adsorption process of MG was proved by the best fitting of pseudo-second order, Elovich, intra-particle diffusion, Langmuir, Dubinin-Radushkevich, and Temkin models onto all the produced materials. The maximum percentage of MG degradation by CG (89.9%) was accomplished by utilizing 1.0 g/L of catalyst mass, an initial MG concentration of 10 mg/L, and 33 W. Arrhenius and Eyring–Polanyi models well applied the MG photodegradation onto the catalyst surface.

Fabrication of titania/calcium alginate nanocomposite matrix for efficient adsorption and photocatalytic degradation of malachite green

This work aims to examine the two techniques' efficiency for the elimination of malachite green (MG) by photocatalytic degradation and adsorption onto synthesized solid nanomaterials. Three solid samples were prepared as calcium alginate (AG), nanotitania (NT), and nanotitania/calcium alginate composite (TG). The morphological and physicochemical characteristics of the solid nanomaterials were investigated by XRD, TGA, DRS, FTIR, pHPZC, nitrogen adsorption/desorption isotherm, SEM, and TEM. The main experimental conditions were determined for sample dose, shaking time, pH, initial malachite green concentration, temperature, ionic strength, and UV lamp power. The resulting data proved that TG attained the higher adsorption capacity (252.52 mg/g) at 40 °C. The adsorption of MG was well fitted by Langmuir, Temkin, Dubinin-Radushkevich, pseudo-second order, intra-particle diffusion, and Elovich models onto all the prepared samples, confirming the endothermic, spontaneous, and favorable adsorption process. The maximum degradation percent (99.6 %) of MG was achieved by using 1.0 g/L as a catalyst dose, 10 mg/L of initial MG concentration, and 33 W for TG. The photodegradation of MG was well fitted by Eyring–Polanyi and Arrhenius models onto the surface of catalyst. The TG reusability resulted in a decrease in the degradation efficiency by 9.8 %, indicating its great capacity as the first nanotitania/calcium alginate nanocomposite used in removing MG from wastewater by two technologies in the same article.

Sonochemical reassembling of Acacia nilotica bark extract mediated Mg doped WO3@g-C3N4 ternary nanocomposite: A robust nanophotocatalyst

One of the most significant environmental issues of the modern era is malachite green dye wastewater due to its high toxicity, susceptibility for mutagenicity, and carcinogenicity. In order to tackle this problem, we prepared Z-scheme type Mg-doped WO3 supported onto g-C3N4 ternary photocatalyst by sonochemical intercalating Mg into WO3@g-C3N4 binary composite in the Acacia nilotica bark extract medium. X-ray diffraction, SEM, EDS, HR-TEM, photoluminescence, and BET surface area analysis were used to explore the structural, morphological and surface characteristics. The findings indicated that the formation of highly crystalline with aggregated lump-based flakiness and various nano-sized crystals in stacked layers with smooth assemblies were taken place. The photoluminescence spectra illustrated that the annihilation of the plasmonic excitons was sufficiently suppressed in ternary composite. Under solar light irradiation, the designed Mg doped WO3@g-C3N4 ternary nanocomposite shown better photocatalytic activity for Malachite green (MG) degradation than undoped g-C3N4 and WO3@g-C3N4 binary composite. It was also investigated how physical parameters like pH, and catalyst dose affected the photo-degradation of MG as well as examined the recyclability up to 4 cycles. The radical scavenging studies suggested that the primary species responsible for the breakdown of MG by the Mg doped WO3@g-C3N4 ternary nanophotocatalyst materials is the •O2– radicals. Photodegradation of MG followed pseudo-first order kinetics with highest rate constant 0.090 min−1 using ternary composite. The superior visible radiation absorption, enhanced surface area, improved separation efficacy of excited e--h+ couples, and the photo-generated electron movement from g-C3N4 to WO3 bands via Mg can all be contributed to the ternary WO3@g-C3N4 nanocomposite’s excellent photocatalytic performance as well as recyclability.

ZnAl2O4/sulfur-doped g-C3N4 S-scheme heterojunction for efficient photocatalytic degradation of malachite green

In this study, ZnAl2O4 and sulfur-doped g-C3N4 (SCN) S-Scheme heterojunctions were successfully prepared by in situ self-assembly method for the efficient removal of malachite green (MG). The composite structure was formed by loading ZnAl2O4 nanoscale particles onto SCN nanosheets. The results showed that the 30 wt% ZnAl2O4/SCN composite exhibited the best photocatalytic properties. The degradation of malachite green (MG) by 30 wt% ZnAl2O4/SCN composite reached 98.3% after 120 min of simulated solar illumination. Photo-induced •O2− was regarded as the primary active substance in the MG photodegradation. This study is expected to provide new possible strategies for the removal of contaminants MG in water.

Highly efficient photocatalytic degradation of malachite green dye over copper oxide and copper cobaltite photocatalysts under solar or microwave irradiation

• Copper oxide and Copper Cobaltite have been successfully synthesized using Co-precipitation method. • Both prepared oxides show efficient photocatalytic activity in the degradation of malachite green dye under solar or microwave irradiation. • Photocatalyst amount and dye concentration significantly affected the rate of MG photodegradation. Advanced Oxidation Processes (AOPs) have been developed in the field of environmental technologies. The aim of this study was to verify the efficiency of heterogeneous photocatalysis in the AOPs for the degradation of organic pollutants. The photocatalytic degradation processes were carried out under sunlight and microwave irradiation in remediation of malachite green (MG) dye taken as model organic pollutant. The copper oxide and copper-cobalt bimetallic oxide (Cu-500 and CuCo-500) were prepared by a simple coprecipitation method and calcined at 500 °C. The synthesized photocatalysts were characterized by X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM-EDX), and Diffuse Reflectance Spectroscopy (DRS) analysis for optical properties (band gap of 1.49 and 1.44 eV for Cu-500 and CuCo-500, respectively). Thereafter, the catalytic activities of the prepared photocatalysts for MG photodegradation were investigated. The influence of different parameters on the photocatalytic reactions, such as photocatalyst mass, initial dye concentration, and irradiation source, was studied. The results reveal the efficiency of the synthesized photocatalysts in the photodegradation of MG with higher rate and good reusability. Hence, the monometallic Cu-500 photocatalyst exhibited better catalytic performance compared to bimetallic CuCo-500.

SmMnO3-decorated ZnO in a hexane-water interface for enhancing visible light-driven photocatalytic degradation of malachite green.

Malachite green (MG) contributes to water contamination because its accumulation adversely impacts aquatic systems. For the first time, we prepare a high photoresponse of ZnO/SmMnO3 heterojunction via a high-speed stirring method at the nonpolar-polar interface assisted by Alstonia scholaris leaves extract (ASLE) as natural hydrolyzing and stabilizing agents. The heterojunction formation boosts the photocatalytic activity of ZnO up to 91.74% under visible light irradiation. Photoluminescence analysis confirmed that modification with SmMnO3 increases the separation of photogenerated charges and plummets the recombination rates of electron-holes, which induces high photodegradation of MG. With 3mg of catalyst, the %TOC removal efficiency for MG degradation over ZnO/SmMnO3 was found to be 53.09%, which is higher than that over ZnO. The kinetics model for the photocatalytic reaction was a pseudo-first-order with excellent stability in four consecutive cycles with no structural change. The radical trapping experiment suggests that h+ was the major species in the MG photodegradation reaction. Additionally, morphology and elemental analyses clearly present the formation of ZnO/SmMnO3 heterojunction without any impurities. The current research demonstrates a simple and advanced technique to design heterojunction photocatalyst at the interface of hexane-water.

Preparation of rGO/FeMoO4 as high-performance photocatalyst for degradation of malachite green, phenol and H2 evolution under natural sunlight

FeMoO4 and rGO/FeMoO4 nanocomposites were successfully prepared by a facile hydrothermal method. The XRD results confirmed that the FeMoO4 has a monometallic β-FeMoO4 crystalline phase while the rGO/FeMoO4 showed both monometallic α- and β-FeMoO4 phases where β-FeMoO4 is the predominant phase. The reduction of graphene oxide (GO) to reduced graphene oxide (rGO) was performed without using any chemical reductions. UV–Vis results showed that the visible light absorption and band gap energy were enhanced after the addition of rGO. The prepared samples were successfully applied for degradation of malachite green (MG) and phenol (Ph) and for H2 evolution under natural solar light irradiation. All the nanocomposites showed higher photocatalytic activities compared with pure FeMoO4 photocatalyst, and the 10%rGO/FeMoO4 gave the highest photodegradation performance for MG and Ph and for H2 evolution. The photodegradation results revealed that the rGO content played the crucial factor in the photodegradation of MG and Ph, and H2 evolution. The mineralization (TOC), photodegradation mechanism and degradation kinetics of MG and Ph were discussed.

Facile combustion synthesis of highly active Mo doped BiVO4 for photocatalytic dye degradation, photo-oxidation of alcohols, antifungal and antioxidant activities

ABSTRACT This work represents the facile and green synthesis of Molybdenum (Mo)-doped bismuth vanadate (BiVO4). Green synthesis of Mo-doped BiVO4 was done using combustion technique using Mangifera indica (Mango) leaf extract as the fuel for combustion. The material synthesised was pure and characterised using X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and photoluminescence (PL). It was found that Mo-doped BiVO4 had monoclinic scheelite phase, with a bandgap of 3.71 eV. Various application was possible from the synthesised material like photodegradation of Malachite Green, a typical organic which showed excellent degradation efficiency of 99% under 120 minutes. The catalyst also gave up to 95% yields in the light-assisted oxidation of aromatic alcohols to corresponding aldehydes. The material also showed excellent antioxidant properties showing 6.7 µg of ascorbic acid equivalence (AAE). It gave an excellent minimum lethal dosage (MLD) of 500 µg against Penicillium and Trichoderma fungal strains and showed maximum of 32 mm zone of inhibition. These applications show the versatility of the material to be used in various fields.

Enhanced photocatalytic degradation of malachite green dye by highly stable visible-light-responsive Fe-based tri-composite photocatalysts.

A novel visible-light-sensitive ZnVFeO4 photocatalyst has been fabricated by the precipitation method at different pH values for the enhanced photocatalytic degradation of malachite green (MG) dye as a representative pollutant under visible light irradiation at neutral pH conditions. The structure and optical characteristics of the prepared photocatalysts were investigated by XRD, FTIR, N2 adsorption–desorption, TEM, diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) analyses. In addition, the photocatalytic activity of ZnVFeO4 photocatalysts superior the efficiency to be more than that of the mono and bi-metal oxides of iron and iron zinc oxides, respectively. The best sample, ZnVFeO4 at pH 3, significantly enhances the degradation rate under visible light to be 12.7 × 10−3 min−1 and can retain a stable photodegradation efficiency of 90.1% after five cycles. The effect of the catalyst dose and the initial dye concentration on the photodegradation process were studied. This promising behavior under visible light may be attributed to the low bandgap and the decreased electron–hole recombination rate of the ZnVFeO4 heterostructures. The scavenger experiment confirmed that the hydroxyl radicals induced the MG photodegradation process effectively. Hence, the ZnVFeO4 is a reliable visible-light-responsive heterostructure photocatalyst with excellent potential for the photodegradation of organic pollutants in wastewater treatment.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-20745-6.

Multiple cobalt active sites evenly embedded in mesoporous carbon nanospheres derived from a polymer-metal-organic framework: efficient removal and photodegradation of malachite green.

A series of robust photocatalysts of mesoporous carbon nanospheres embedded with multiple cobalt active sites (Co/Co x O y @mC) have been constructed for efficient removal and photodegradation of malachite green (MG). Here, a cobalt-based polymeric-metal-organic framework (polyMOF(Co)) was constructed by using a polyether ligand containing 1,4-benzenedicarboxylic acid units. Afterward, polyMOF(Co) was calcined into a series of Co/Co x O y @mC hybrids at diverse high temperatures (400, 600, and 800 °C) under a N2 atmosphere. Therefore, Co coordination centers were transformed into various active sites such as Co, CoO, and Co3O4, which were embedded within the mesoporous carbon network derived from the polymeric skeleton. Considering the even distribution of Co-related active species and high porosity inherited from polyMOF(Co), the constructed Co/Co x O y @mC hybrid obtained at 600 °C illustrated higher removal ability (79%) with a maximum adsorption capacity of 314 mg g-1 within 120 min and better photodegradation performance (degradation rate of 95%) toward MG than those of the other photocatalysts obtained at 400 and 800 °C. Moreover, the possible photocatalytic reaction mechanisms, including the transfer behavior of charge carriers, generation of reactive species, and intermediate degradation of products, were provided. The present work showed an alternative strategy for the feasible and efficient preparation of photocatalysts based on MOFs.

Photocatalytic performance of β-Ga2O3 microcubes towards efficient degradation of malachite green

In this work, the photocatalytic degradation of malachite green (MG) solutions by β-Ga2O3 was investigated. The latter was synthetized by reacting gallium nitrate with concentrated formic acid, which produced gallium formate. The thermal decomposition of this compound at 850 °C produced single-phase β-Ga2O3. The resulting morphology corresponds to non-agglomerated microcubes, with a size in the range of 0.8 and 2.3 μm. The surface chemical composition and bandgap energy of this oxide were determined by X-ray photoelectron spectroscopy (XPS) and the Tauc method, respectively. The photodegradation of MG was carried out under violet light (λ = 405 nm), at room temperature, using the as-prepared powder. The results revealed a fast degradation of the dye during the first 20 min, which attenuates over time. The rate of photodegradation depends on the amount of β-Ga2O3 used and can be fitted by an exponential equation. The role of free hydroxyl radicals and reactive oxygen species in photocatalysis was addressed by using analytic techniques (FTIR and XPS).

Oxygen-doped carbon nitride/red phosphorus composite photocatalysts for effective visible-light-driven purification of wastewater

In this study, broad-spectral-responsive photocatalysts O-doped g-C3N4/Red P (OCN/RP) heterojunctions were prepared by mechanical grinding at room temperature, which is a simple and green synthesis process. The OCN nanosheets are fixed on the red P particles to form intimate I-type heterojunctions. The OCN/RP heterojunctions show extended excitation wavelength to 700 nm and enhanced photocatalytic activity against organic pollutant malachite green (MG). The enhancement benefits from the migration of photogenerated e− from OCN to RP, which facilitates effective charge separation at the interface between OCN and RP. ‧O2−, and ‧OH are proved to be the main active substances of MG photo-degradation on OCN/RP. This experiment provides a general strategy for the preparation of non-metal photocatalysts with broad-spectral responsibility and improved catalytic activity.

Enzymes and phytochemicals from neem extract robustly tuned the photocatalytic activity of ZnO for the degradation of malachite green (MG) in aqueous media

The malachite green (MG) is very difficult to degrade in water; thus, it needs an efficient photocatalyst. In this study, neem extract was used to tune the surface and crystal properties of ZnO nanostructures for the photodegradation of MG. The biosynthesized ZnO samples were prepared by hydrothermal method in the presence of 5, 10 and 15 mL of neem extract. The structural characterization has shown nanoparticle like morphology of ZnO as revealed by scanning electron microscopy (SEM) and hexagonal phase was confirmed by powder X-ray diffraction (XRD) technique. The XRD analysis has shown a shift in the 2 theta towards lower angle for ZnO with increasing amount of neem extract. Also, the crystallite particle size of ZnO was decreased with increasing neem extract. The UV–visible spectroscopy has shown the decrease in the optical band gap of ZnO, and the lowest band gap is possessed by ZnO sample produced with 15 mL of neem extract. The ZnO sample obtained with 15 mL of neem extract has shown approximately 99% degradation efficiency for MG for 70 min in aqueous solution. The superior photocatalytic activity of ZnO sample with 15 mL of neem extract could be attributed from the decrease in charge recombination rate due to the decreased optical band gap and particle size.

Facile chemical fabrication of Ni doped CoAl2O4 nano-spinel photocatalysts: Physico-chemical properties and photodegradation of toxic malachite green dye under visible light

ABSTRACT In this present study, we report the facile chemical fabrication of Ni-doped CoAl2O4 (NCA) (Co1-xNixAl2O4-δ, where x = 0.0, 0.05, 0.10, 0.15 and 0.20) nano-spinel photocatalyst materials by a simple chemical precipitation route. The XRD data revealed the presence of cubic crystal structure for CoAl2O4 and Ni-doped CoAl2O4 samples. Presence of vibration modes of M − O, Al−O, and M − O− Al in the spinel lattice structure in the materials was found out by FTIR analysis. The particle size analysis and SEM confirmed the presence of nanosized grains in the samples. The occurrence of appropriate amount of Co, Al, O and Ni was detected by EDAX analysis. The optical characteristics of Co1-xNixAl2O4-δ were studied using UV spectral studies. The band gap energy (Eg) of NCA was found to be in the range of 2.14 to 2.32 eV. The photocatalytic activity studies confirmed that the fabricated NCA nanoparticles have good photocatalytic behaviour in the degradation of malachite green (MG) dye solution under visible light irradiation. Further, the obtained results revealed that the doping of Ni has influenced the structural, spectral, morphology and the photocatalytic properties of the CoAl2O4 spinel materials to a greater extent. In addition, the factors affecting the photo-degradation of MG including composition of photocatalyst, photocatalyst loading, pH of the dye solution and the irradiation time were investigated and reported. The studies indicate that the 15% Ni-doped CoAl2O4 is a promising candidate material among all for the photocatalytic degradation of highly toxic dyes such as MG.

Highly efficient sunlight-driven photocatalytic degradation of malachite green dye over reduced graphene oxide-supported CuS nanoparticles

A facile co-precipitation technique, including in-situ reduction of graphene oxide (GO), is used to synthesize rGO/CuS nanocomposites. The photocatalytic performance of CuS was enhanced by loading reduced graphene oxide (rGO). Several instrumentations depicted the obtained nanostructures. The photocatalytic performance of the rGO/CuS nanocomposites was evaluated, for the first time, to eliminate malachite green (MG) dye under direct sunlight radiance. The experimental results revealed that the (rGO/CuS-7) composite achieved the highest efficiency of 97.6% for MG after exposure to sunlight for 90 min Also, the photocatalyst could recycle for five times without any loss in the activity. The result showed that rGO/CuS has the highest total organic Carbon (76%) compared to the published reports for the photodegradation of MG. The research outcomes develops a new one-pot synthesis avenue to prepare a promising rGO/CuS nanocomposites for the photocatalytic degradation of organic contaminants under direct sunlight.