Acid Red Research Articles

Magnetically stimulated azo dye biodegradation by a newly isolated osmo-tolerant Candida tropicalis A1 and transcriptomic responses

A recently isolated osmo-tolerant yeast Candida tropicalis A1, which could decolorize various azo dyes under high-salinity conditions, was systematically characterized in the present study. Stimulating dye-decolorization effectiveness and osmo-tolerance of the yeast by static magnetic field (SMF) was investigated and transcriptomic responses of the yeast to SMF was analyzed to propose possible mechanisms. The results demonstrated that the yeast A1 effectively decolorized (≥ 97.50% within 12 h) and detoxified (from high toxicity to low toxicity within 24 h) 70 mg/L Acid Red B (ARB) under the optimized conditions through a series of steps including naphthalene-amidine bond cleavage, reductive or oxidative deamination/desulfurization, open-loop of hydroxy-substituted naphthalene or benzene and TCA cycle. Moreover, dye decolorization performance and osmo-tolerance of the yeast A1 were further improved by 24.6 mT SMF. Genes encoding high-affinity hexose/glucose transporter proteins and NADH-ubiquinone oxidoreductase were up-regulated by 24.6 mT SMF, which might be responsible for the increase of dye decolorization. Significant up-regulation of glycerol-3-phosphate dehydrogenase and cell wall protein RHD3 suggested that osmo-tolerance was enhanced by 24.6 mT SMF through promoting production and intracellular accumulation of glycerol as compatible solute, as well as regulation of cell wall component. In conclusion, 24.6 mT SMF led to the up-regulation of related genes resulting in enhanced dye biodegradation efficiency and osmo-tolerance of the yeast A1.

Insight into the effect of surfactant modification on the versatile adsorption of titanate-based materials for cationic and anionic contaminants

The new challenges to adsorption are imposed for the diversity of contaminants in wastewater in recent years. Herein, titanate-based materials (peroxide sodium titanate, PST) were modified by three different kinds of surface charged surfactant: dodecyl dimethyl betaine (BS-PST), sodium dodecyl sulphate (SDS-PST) and dodecyltrimethyl ammonium chloride (DTAC-PST) to enhance the versatile adsorption performance for four typical contaminants including ammonia nitrogen (NH4+, inorganic and cationic), phosphate (H2PO4−, inorganic and anionic), methylene blue (MB, organic and cationic) and Acid Red G (ARG, organic and anionic). The batch adsorption experiments showed that the DTAC-PST exhibited better in the removal of MB, ARG and H2PO4− than that of other adsorbents. The theoretical maximum adsorption capacity of DTAC-PST is 49.28 mg g−1 for NH4+, 34.74 mg g−1 for TP, 81.87 mg g−1 for MB and 545.81 mg g−1 for ARG. The simultaneous adsorption results showed that the concentration (10 mg L−1 of NH4+, 3 mg L−1 of TP, 50 mg L−1 of MB and 50 mg L−1 of ARG) of all the four chemicals in simulated wastewater could be controlled to be below the discharge levels in China (GB, 18918–2002) by DTAC-PST at the pH of 3.0. The FT-IR spectra demonstrated that ion exchange was the main way for NH4+ removal, however, electrostatic attraction and ligand exchange were the reason for MB adsorption. In addition, C–N+ from DTAC modification made main contribution to the excellent adsorption performance for ARG and H2PO4−. The saturated DTAC-PST could be conveniently regenerated by 0.5 mol L−1 NaOH solution and maintained about 80% of adsorption capacity after five cycles.

Synthesis of copper (I, II) oxides/hydrochar nanocomposites for the efficient sonocatalytic degradation of organic contaminants

Herein, novel Cu2O–CuO/HTC composites were prepared by hydrothermal precipitation employing as carrier sawdust hydrochar carbonized at 200°C for 2, 6, and 12h. The composites were used for the effective sonocatalytic degradation of three dyes (Acid Blue 92 (AB 92), Acid Red 14 (AR 14) and Acid Orange 7 (AO 7)) with different molecular structure. To gain insight into the functional groups, crystalline structure, elemental composition and optical characteristics of the Cu2O–CuO/HTC composites, FT-IR, XRD, EDX and UV–vis analyses were carried out. Also, the surface morphology and area of the Cu2O–CuO/HTC composites were investigated by SEM and BET analysis. The effect of different parameters, such as dye concentration, solution pH, and catalyst dosage on the sonodegradation process was examined. Among the as-prepared composites, the Cu2O–CuO/HTC-2h sample exhibited the best performance, offering a degradation efficiency of 85.43% after 90min. GC-MS analysis was in addition employed to determine potential intermediates. To assess the mineralization of dye solution under optimum conditions, COD analysis was performed implying 77.77% removal efficiency. Additionally, the reusability and stability of the as-prepared composites were verified. The leaching copper concentration in the aqueous phase was measured within four consecutive runs.

Recyclable magnetic ZnCo2O4-based ceramic nanostructure materials fabricated by simple sonochemical route for effective sunlight-driven photocatalytic degradation of organic pollution

Solar light assisted degradation of unfavorable contaminants has been illustrated to be a very good way to obviate environmental contamination and remedy wastewater. Although a wide range of compounds have been suggested as catalysts for this aim, highly efficient removal of organic contaminants with usage of visible radiation remains a challenging issue. Herein, we represent a novel, fast and proper way to successfully create ZnCo2O4/Co3O4 nanocomposite with usage of the sonochemical process, functioning as a very appropriate compound for the elimination of organic contaminants. As a novel kind of base agent, 2,2-dimethyl-1,3-propanediamine was employed to create ZnCo2O4/Co3O4 nanocomposite. The impacts of usage of diverse capping agents as well as ultrasonic time on the size, catalytic functionality and shape of ZnCo2O4/Co3O4 were considered. Applying diverse detection techniques, the sonochemically created nanocomposite was explored. Based on the outcomes, CTAB was chosen as a very appropriate capping agent as well as 10 min as a very beneficial ultrasonic time to create the tiniest particles possessing the highest uniformity. The created nanocomposites were applied to eliminate unfavorable contaminants (methyl violet, Acid Red 14 and erythrosine) and their capability was compared. The sonochemically created nanocomposite with usage of CTAB at 10 min as optimized sample was able to demonstrate highly efficient performance, since 100, 95.6 and 100% removal of methyl violet, Acid Red 14 and erythrosine in 65 min under visible radiation was observed. Further, the optimized sample possesses very proper durability and can be easily retrieved without appreciable loss of catalytic yield up to eleven runs. Considering its simple fabrication and highly efficient performance, ZnCo2O4/Co3O4 nanocomposite (sonochemically created with usage of CTAB at 10 min) can be a helpful and competitive compound as a visible-light-driven catalyst to obviate environmental contamination.

Removal of Dye Acid Red 1 from Aqueous Solutions Using Chitosan-iso-Vanillin Sorbent Material

Sorption of Acid Red 1 (AR1) from aqueous solutions utilizing low-cost sorbent material; (chitosan-iso-vanillin) is studied under batch conditions. The remaining concentrations of the azo dye are measured at λmax = 546 nm by UV spectrophotometric method. Langmuir data reveal that the maximum removal capacity was 555.556 mg/g at pH 3. Freundlich isotherm represents the best fitting model on the removal of AR1 using chemically modified chitosan verifying the sorption takes place on heterogeneous surfaces with multilayer adsorption. Kinetic studies of the sorption process revealed that intraparticle diffusion is not only the rate-determining step but also a chemical reaction takes place as well. The results indicate that high sorption rapidness with almost 90% achieved within 90 min. Thermodynamic investigations suggest that the process favours an exothermic nature. The polymer utilized in the present study is being considered as a feasible sorbent material for the removal of AR1 from waste effluent.

Strong enhancement effect of bisulfite on MIL-68(Fe)-catalyzed Fenton-like reaction for organic pollutants degradation

Metal organic frameworks (MOFs) have shown a great potential to act as heterogeneous Fenton-like catalysts. However, the lower catalytic efficiency and reaction rate are limiting their practical applications. Herein, a facile and efficient strategy was studied to boost the catalytic oxidation performance of MIL-68(Fe)-mediated Fenton-like process with the addition of a minor amount of bisulfite. The factors affecting the catalytic oxidation capacity of the MIL-68(Fe)/HSO3−/H2O2 system were investigated using methyl orange (MO) as model pollutant. Under the optimal condition, the degradation rate of MO could be increased by 11.5 times compared to that in MIL-68(Fe)/H2O2 system, and the total organic carbon (TOC) removal in 120 min reached 46.8%. The MIL-68(Fe)/HSO3−/H2O2 system also displayed a wide applicable pH range. Besides MO, other organic contaminants such as acid red 18 (AR18), rhodamine B (RhB), methylene blue (MB), xylenol orange (XO) and tetracycline hydrochloride (TC) could be effectively degraded in the MIL-68(Fe)/HSO3−/H2O2 system as well. The quenching tests and electron paramagnetic resonance (EPR) spectrometry confirmed that OH, SO4−, HO2, and 1O2 were the main reactive species for MO degradation in the MIL-68(Fe)/HSO3−/H2O2 system. The coumarin fluorometry further disclosed that much more hydroxyl radicals were generated in the MIL-68(Fe)/HSO3−/H2O2 system than in MIL-68(Fe)/H2O2 system. Cyclic voltammetry analysis, on the other hand, indicated that the presence of HSO3− facilitated the Fe(III)/Fe(II) cycle in the MIL-68(Fe)/HSO3−/H2O2 system. Based on these results, the enhancement mechanism of the Fenton-like MIL-68(Fe)/HSO3−/H2O2 system was proposed. Finally, the cyclic experiments manifested the MIL-68(Fe)/HSO3−/H2O2 system had good stability and reusability. This study suggests that the addition of bisulfite being an excellent approach to construct the Fe-MOFs mediated Fenton systems for eliminating organic contaminants in water with high efficiency.

Photocatalytic and superior ascorbic acid sensor activities of PVA/Zn-Fe-Mn ternary oxide nanocomposite

The sol-gel method followed by accidental self-propagation procedures was used for the synthesis of optimized high surface area and porous Zn/Fe/Mn oxide nanocomposites. The synthesized single and ternary nanomaterials were characterized by DTG-DSC, UV–vis-DRS, XRD, FT-IR, SEM-EDAX, BET, TEM-HRTEM-SAED, and CV-EIS-Amperometric analytical techniques. Compared to single ZnO, the characterization results revealed the surface area, porosity, and charge transfer property improvement on the ternary nanocomposite (TNC) material. The DTG/DSC result substantiated that the calcination temperature of 500 °C was sufficient to degrade the impurities and PVA polymers after serving the role of a capping agent. The decent stability of the TNC material was further confirmed on the amperometric technique. Using a TEM image and XRD pattern analysis, the approximate particle size of ZnO and TNC was determined to be 59 and 10 nm, respectively. The porosity characteristics of the optimized TNC was explored by SEM images and BET analysis. This is consistent with the result obtained from HRTEM (IFFT) and SAED pattern analysis. The presence of noble charge transfer property by TNC material against single ZnO had been witnessed from CV/EIS analysis. This decent charge transfer properties of the material were also further confirmed on the photocatalytic decomposition of Congo red and Acid Red 8 dyes and novel ascorbic acid sensing activity. The sensing capability of the material was understood from CV and amperometric analysis.

Enhancement of wool fabric dyeing via treatment with AgNPs

Nanoparticles are a successful material for fibers and textiles functionality. In this work, silver nanoparticles (AgNPs) were synthesized by the chemical reduction of Ag+ and then the AgNPs were investigated by UV–visible (UV–vis) spectrophotometer, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The synthesized nanoparticles were used for the surface improvement of the fabric, and the fabric was then dyed with C.I. Acid Red 18 (AR 18) at different temperatures. The physical properties, tensile strength, wrinkle rate, color strength, and colorfastness to perspiration of wool fabric were studied in dyed wool and raw wool fabric. It was found that the nanoparticle-treated fiber was stronger than untreated yarn. The corresponding rate of adsorption was analyzed and calculated according to different kinetic models. Furthermore, diffusion coefficients, the activation energy, and thermodynamic parameters were calculated. Treatment with AgNPs produces a wool fabric with excellent color fastness and antibacterial properties enables enhanced health care and reduced environmental impacts.

Removal of textile dyes from water by jute stick activated carbon: process optimization and isotherm studies

In this study, jute stick derived activated carbon (JSAC) has been evaluated as an adsorbent to remove textile dyes namely acid red-1 (AR-1), reactive orange-16 (RO-16), and methylene blue (MB) from water using the Box–Behnken model of response surface methodology (RSM). The direct and interaction effects of four independent process parameters namely solution pH, initial dye concentration, adsorbent dose, and time were investigated and optimized for textile dye by using ANOVA. The optimum conditions for maximum % dye removal were found to be pH-3, initial dye concentration-500 mg L−1, adsorbent dose-0.9 gL−1, and time-110 min for AR-1; pH-3, initial dye concentration-350 mg L−1, adsorbent dose-1.5 g L−1, and time-110 min for RO-16, and pH-11, initial dye concentration-415 mg L−1, adsorbent dose-0.7 g L−1, and time-86 min for MB, respectively. Adsorption equilibrium investigations were carried out with Langmuir, Freundlich, and Jovanovic models. Based on error analysis, Langmuir isotherm was found the best-fitted model with maximum adsorption capacities of 588.2, 156.3, and 384.6 mg g−1 for AR-1, RO-16, and MB, respectively. The dimensionless factor, RL values (range: 0.0152–0.2665) also indicated spontaneous and favorable adsorption of studied dyes onto JSAC. Dye loaded adsorbents were easily regenerated with 0.1 M HCl (for MB) and 0.1 M NaOH (for AR-1/RO-16) and reused up to the 4th cycle. The present investigation indicated that JSAC, with a highly porous and stable structure coupled with various functional groups, holds immense potential as a new adsorbent for textile dyes.

Application of Functionalized DVB-co-GMA Polymeric Microspheres in the Enhanced Sorption Process of Hazardous Dyes from Dyeing Baths.

Intensive development of many industries, including textile, paper, plastic or food, generate huge amounts of wastewaters containing not only toxic dyes but also harmful auxiliaries such as salts, acid, bases, surfactants, oxidants, heavy metal ions. The search for effective pollutant adsorbents is a huge challenge for scientists. Synthesis of divinylbenzene copolymer with glycidyl methacrylate functionalized with triethylenetetramine (DVB-co-GMA-TETA) resin was performed and the obtained microspheres were evaluated as a potential adsorbent for acid dye removal from dyeing effluents. The sorption capacities were equal to 142.4 mg/g for C.I. Acid Green 16 (AG16), 172 mg/g for C.I. Acid Violet 1 (AV1) and 216.3 mg/g for C.I. Acid Red 18 (AR18). Non-linear fitting of the Freundlich isotherm to experimental data was confirmed rather than the Langmuir, Temkin and Dubinin-Radushkevich. The kinetic studies revealed that intraparticle diffusion is the rate-limiting step during dye adsorption. Auxiliaries such as Na2SO4 (5–25 g/L), CH3COOH (0.25–1.5 g/L) and anionic surfactant (0.1–0.5 g/L) present in the dyeing baths enhance the dye adsorption by the resin in most cases. Regeneration of DVB-co-GMA-TETA is possible using 1 M NaCl-50% v/v CH3OH.

MgNb2O6:Dy3+ nanophosphor: A facile preparation, down conversion photoluminescence and UV driven photocatalytic properties

Series of (1–9 mol %) dysprosium (Dy3+) ions doped MgNb2O6 (MNO) nanophosphors were synthesized by chemical combustion process and their photo luminescent and photocatalytic behaviours were examined. Powder X-ray diffraction (PXRD) reveals the columbite structure and crystal structure parameters were calculated. The average crystallite size was found to be in the range of 20–30 nm as calculated by Scherrer's method. The photoluminescence (PL) of MgNb2O6:Dy3+ (λexc-393 nm) reflects white emission for the prepared samples as confirmed by CIE and CCT. The photocatalytic activities of these nanophosphors were probed for the decolorization of acid red 88 (AR-88) under UV light irradiation. The photocatalyst with MgNb2O6:Dy3+ (5 mol %) showed enhanced activity of 97%, attributed to effective separation of charge carriers. All the above experimental results confirm that, the optimized phosphor is quite useful for WLEDs, solid-state lighting applications and as a photocatalyst.

An intensified ozonation system in a tank reactor with foam block stirrer: Synthetic textile wastewater treatment and mass transfer modeling

A novel multiphase tank reactor with foam block stirrer, also called rotating foam stirrer reactor (RFSR), was used to intensify ozone mass transfer and oxidation of synthetic textile wastewater processes for the first time. Results show that the RSFR can improve the ozone mass transfer process by adjusting operation conditions and gas hydromechanics. In order to predict the volumetric mass transfer coefficient, a set of correlation was developed within ±15% deviation. Further, based on an Acid Red B (ARB) solution used as simulated synthetic textile wastewater, it was found that the removal efficiency was improved by intensifying ozone mass transfer process, and changing operation conditions can promote the transformation of the ozone oxidation path to an indirect reaction way. Finally, results show that the Fe-Co oxides coated on the foam block stirrer can further intensify the degradation processes in the ARB solution. This study gives a fundamental understanding of the intensification mechanism of the RFSR and shows the promising prospect of an RFSR used in in the wastewater treatment.

Preparation of Acid Red73 adsorbed on chitosan-modified sepiolite with SiO2 coating as a highly stable hybrid pigment

The application of organic dyes in industry is severely limited due to its insolubility and instability. The adsorption of organic dyes by inorganic materials to form hybrid pigment is a valid method to improve its stability, thus widening its applications in industries. A simple method for preparing stable hybrid pigment by adsorpting Acid Red 73 (AR73) on the chitosan (CTS) modified sepiolite with a SiO2 coating is explored in this work. Sepiolite modified by the CTS was used to immobilize AR73 (CTS-sep/AR73) uniformly to form a hybrid pigment. The effects of the dosage of CTS, the concentration of acetic acid (HAc) and the pH of AR73 solution for CTS-sep adsorption of AR73 were investigated. CTS-sep/AR73 was further coated with a layer of SiO2 to form the CTS-sep/AR73@SiO2 pigment, which enhanced the stabilities of the hybrid pigment. The CTS-sep/AR73@SiO2 pigment shows excellent stability in strong acid, strong alkali and anhydrous ethanol environment, along with the improved thermal ageing, intensified UV resistance, and enhanced thermal stability (more than 220 °C) which is higher than that of CTS-sep/AR73 hybrid pigment.

The preparation of nano-MIL-101(Fe)@chitosan hybrid sponge and its rapid and efficient adsorption to anionic dyes

The polymer adsorbents in the sponge form have the porous structure and high elasticity that endow them with good adsorption capacity and recyclability. The immobilization of nano-materials in the sponges can improve their adsorption properties evidently. The nano-MIL-101(Fe)@chitosan(CS) hybrid sponge was prepared by freeze-drying method. Characterization results indicated that rhombic nano-MIL-101(Fe) particles were uniformly dispersed throughout the hybrid sponge. The hybrid sponge showed higher efficiency for the adsorption of anionic dyes compared with the pristine CS sponge. The maximum adsorption capacity of MIL-101(Fe)@CS sponge for Acid Red 94 reached 4518 mg/g and the rapid suction experiments on different dyes showed that the hybrid sponge could be used as a filter for the quick removal of anionic dyes in low concentration solution.

Structural, morphological and optical studies of sol-gel engineered Sm3+ activated ZnO thin films for photocatalytic applications

Rare earth (RE) ions activated ZnO thin films were prepared via sol-gel route and the thin films be categorized by various techniques. X-ray diffraction (XRD) studies display the hexagonal wurtzite structure of the prepared thin films. Scherrer's formula was utilized to calculate the average crystallite size (25–40 nm) with different Sm3+ concentrations. The optical energy gap was calculated by Diffused Reflectance spectra (DRS). The Acid Red (AR) dye was degraded under ultraviolet (UV) light irradiation with ZnO: Sm3+(1-9 mol %) nanostructured thin films and the highest photodegradation (95 %) was observed for 7 mol % of Sm3+ doped ZnO catalyst. All the obtained results suggest that prepared material could be a prominent material as photocatalyst.

Cool and photocatalytic reddish-brown nanostructured Fe2O3@SiO2@TiO2 pigments

In the present study, the influence of the crystalline structure of Fe2O3(amorphous) @TiO2, α-Fe2O3@TiO2 and α-Fe2O3 @SiO2 @TiO2 nanocomposites on the NIR-reflectance and photocatalytic properties have been investigated. The nano-sized α-Fe2O3, SiO2 and TiO2 were prepared via co-precipitation, Stober and sol-gel methods, respectively. The photocatalytic performance of the nanoparticles was examined by the photodegradation of Acid Red18 under UV irradiation after 120 min of reaction. NIR-diffuse reflectance and colorimetric parameters were measured. The results showed that the TiO2 coating has considerably enhanced the photocatalytic activity and the NIR-reflectance. Fe2O3 (amorphous)@TiO2 nanocomposite possesses the highest NIR- reflection and α-Fe2O3 @TiO2 reveals the maximum photocatalytic degradation. Silica coating in the α-Fe2O3@SiO2@TiO2 nanocomposite has been boosted both of the NIR-reflectance and photocatalytic degradation to their maximum level. As a result, this multipurpose composite is suitable to be simultaneously developed for both photocatalytic and cool pigment applications.

Effective removal of organic pollutants by adsorption onto chitosan supported graphene oxide-hydroxyapatite composite: A novel reusable adsorbent

A hetero-structured adsorbent with outstanding adsorption performance has acquired an increased attention due to their excellent behaviour in environmental applications. Tailoring of graphene oxide and hydroxyapatite with suitable biopolymeric adsorbents would enhance the porosity, stability, specific surface area and shows high sorption performance. Herein, chitosan reinforced graphene oxide-hydroxyapatite (CS@GO-Hap) matrix was fabricated efficiently in the atmosphere of nitrogen by co-precipitation technique. Here, chitosan acted as a host in the preparation and provided the surface for a composite generation. The batch mode method was applied to investigate the adsorption performance of CS@GO-Hap composite, showed an adsorption efficiency of 43.06, 41.32 and 40.03 mg/g for the removal of the toxic Congo Red (CR), Acid Red 1 (AR1) and Reactive Red 2 (RR2) dyes from water, respectively. The composite showed enhanced adsorption at the pH of 2 and the removal efficiency of CS@GO-Hap composite decreased with increase in pH. The adsorption kinetic and isotherm fitted well with pseudo-second-order and the Freundlich model, respectively. The thermodynamic study of the adsorption of dyes showed that the process was spontaneous. The regeneration experiments emphasized that the desorption was ideal, and exhibited more than 65% regeneration ability with 0.1 M NaOH solution. The mechanism of dyes adsorption on CS@GO-Hap composite involved the electrostatic force interaction, surface complexation, hydrogen bondings and π−π stacking interactions. The findings of the study revealed the exceptional behaviour of CS@GO-Hap composite in removing the azo dyes from aqueous solutions and the great significance of the composite in the future application in water/wastewater treatment process.

Performance of electrocoagulation for food azo dyes treatment in aqueous solution: optimization, kinetics, isotherms, thermodynamic study and mechanisms

ABSTRACT Electrocoagulation process was applied for the removal of Acid Red 14 in bath essays. Under optimal operating conditions: current density of 70 mA/cm2, 60–90 min of reaction, natural pH, and an initial concentration of 50 mg/L, the decolorization and COD removal efficiencies were 95% and 90%, respectively. The electrical energy consumption was 110 kWh/kgAR.14removed. These experimental results are well modeled by the Langmuir and Freundlich isotherms and follow first-order reaction kinetics. The thermodynamic parameters indicated that the nature of the adsorption process was endothermic and spontaneous. The mud formed after electrocoagulation was characterized by FTIR and SEM coupled to EDS.

CBD grown pure and Ce-doped ZnO nanorods: Comparison of their photocatalytic degrading efficiencies on AR88 azo dye under visible light irradiation

A seed-mediated approach was utilized in growing of pure and cerium-doped ZnO nanorods via a low-temperature (∼95 °C) chemical bath deposition (CBD) method. The aqueous solutions with different Ce molar ratios (Ce/(Ce + Zn), which were equal to 0, 0.01, 0.05, 0.1 or 0.2) were prepared. An excess amount of cerium ions (≥0.1 in the present study) caused the formation of a new phase, identified as CeO2. Cerium doping induces lattice strains due to the difference in radius of the anions. With doping, the 2θ angle of X-ray diffraction (XRD) peaks slightly shifted towards lower values. Inserting cerium atoms brings about decrease, as well, in the band gap, which was confirmed by the redshifts at the absorption edges in their UV–vis spectra. In addition, the photoluminescence (PL) spectra of the samples were measured at room temperature revealed the enhanced visible emission intensities from the Ce-doped nanorods. This indicates the formation of defect levels below the conduction band. Finally, the photocatalytic degrading efficiencies of the samples on Acid Red 88 (AR88) azo dye were determined under visible light irradiation. The highest degradation rate was measured for the doped samples prepared using the CBD solution with the Ce/(Ce + Zn) ratio equal to 0.01.

Perceptive removal of toxic azo dyes from water using magnetic Fe3O4 reinforced graphene oxide–carboxymethyl cellulose recyclable composite: Adsorption investigation of parametric studies and their mechanisms

A magnetic FGC composite was prepared using Fe3O4 particles and graphene oxide–carboxymethyl cellulose which were blended as the source materials. The adsorptive interactions of FGC matrix with dye molecules like Congo Red (CR), Acid Red 1 (AR1) and Reactive Red 2 (RR2) were examined and explained through various analytical techniques. The optimum conditions for the adsorption of dyes include the initial concentration of dyes (50 mg/L), volume of dyes (50 mL), adsorbent dosage (100 mg) and solution pH (3-6). In these conditions, the FGC showed extreme adsorption efficiency of 45.09, 47.32 and 46.21 mg/g for the removal of CR, AR1 and RR2 dye molecules, respectively. The Freundlich isotherm data shows better fit for dye molecules adsorption. The thermodynamic results confirmed the endothermic and spontaneous nature in adsorption. The mechanism of CR, AR1 and RR2 dyes adsorption on FGC composite follows the interactions such as electrostatic attraction, hydrogen bonding, π−π stacking, and surface complexation. The FGC composite was regenerated over 65% after five consecutive cycles using an aqueous 0.1 M NaOH solution. The FGC composite showed an enhanced adsorption capacity for the removal of toxic azo dyes. Hence, the prepared composite could be used as a potential adsorbent for the removal of dye molecules from contaminated water.