Removal of toxic malachite green dye from aqueous environment using reduced magnetic graphene oxide as an efficient and reusable adsorbent

Rare Earth Doped ZnO Nanoparticles as Spintronics and Photo Catalyst for Degradation of Pollutants

Antibiotic water contamination is a growing environmental problem in the present day. As a result, water treatment is required for its reduction and elimination. Due to their important role in resolving this issue, photocatalysts have drawn a great deal of interest over the past few decades. When non-biodegradable organic matter is present in polluted water, the photo catalytic process, which is both environmentally friendly and an improved oxidation method, can be an effective means of remediation. In this regard, we report the successful synthesis of pure phased rare earth doped ZnO nanoparticles for tetracycline degradation. The prepared catalysts were systematically characterized for structural, optical, and magnetic properties. The optical band gap was tailored by rare earth doping, with redshift for Sm and Dy doped nanoparticles and blueshift for Nd doped ZnO nanoparticles. The analysis of photoluminescence spectra revealed information about the defect chemistry of all synthesised nanoparticles. Magnetic studies revealed that all synthesized diluted magnetic semiconductors exhibit room temperature ferromagnetism and can be employed for spintronic applications. Moreover, Dy doped ZnO nanoparticles were found to exhibit a maximum degradation efficiency of 74.19% for tetracycline (TCN) removal. The synthesized catalysts were also employed for the degradation of Malachite green (MG), and Crystal violet (CV) dyes. The maximum degradation efficiency achieved was 97.18% for MG and 98% for CV for Dy doped ZnO nanoparticles. The degradation mechanism involved has been discussed in view of the reactive species determined from scavenging experiments.

Photocatalytic assessed adsorptive removal of tinidazole from aqueous environment using reduced magnetic graphene oxide-bismuth oxychloride and its silver composite

Antibiotics (tinidazole (TNZ)) in wastewater, exhibit adverse effects on humans and ecosystem. The current study was aimed to synthesize photocatalysts mrGO/BiOCl and mrGO/BiOCl/Ag. mrGO was coupled with BiOCl by hydrothermal method and Ag was deposited over it. The synthesized mrGO/BiOCl and mrGO/BiOCl/Ag were confirmed by Pzc analysis (5.5 and 4.4 for mrGO/BiOCl and mrGO/BiOCl/Ag, respectively), surface area analysis (380 m² g^-1, 227.7 m² g^-1, 220 m² g^-1 for mrGO, mrGO/BiOCl and mrGO/BiOCl/Ag respectively), elemental analysis (Ag, O, Bi, Fe), surface morphology (rough ball like sphere of mrGO/BiOCl and cubic Ag nanoparticles in mrGO/BiOCl/Ag), functional groups and band gap (Eg) determination. The Eg was determined using Kubelka-Munk equation as 3.5 and 2.8 eV for mrGO/BiOCl and mrGO/BiOCl/Ag respectively. During the adsorption study, the best experimental conditions for various operating parameters such as pH (2), contact time (5 min for mrGO/BiOCl and 10 min for mrGO/BiOCl/Ag under UV irradiation), TNZ concentration (18 μgL^-1) and catalyst dosage (0.001 g) were achieved. Kinetic study revealed that both composites followed pseudo second order kinetics (R² = 0.9979 and 0.9986, respectively). Data of rGO/BiOCl was fitted to Freundlich adsorption model (R² = 0.9687) and rGO/BiOCl/Ag fitted to Langmuir adsorption model (R² = 0.9994). Moreover, thermodynamic parameters confirmed that a photodegradation phenomenon was spontaneous and exothermic. The results confirmed that rGO/BiOCl and rGO/BiOCl/Ag are appropriate composites for TNZ removal from the aqueous environment with removal efficiency of 97 and 24%, respectively.

Facile synthesis of multifunctional zinc vanadate/polyaniline composite for photocatalytic degradation and supercapacitor applications

Multifunctional Zn₃V₂O₈/Polyaniline (ZnV/PANI) composite was prepared by in-situ oxidative polymerization method. The formation of ZnV and ZnV/PANI composite was proved by various characterization tools including such as FTIR, XRD, SEM, BET, VSM, TEM and XPS analysis. The average crystalline size calculated using Scherrer equation of ZnV and ZnV/PANI were found to be 45 nm and 92 nm respectively. From the Tauc plots the bandgap values (E_g) were found to be 2.4 eV and 2.0 eV for ZnV and ZnV/PANI respectively. The FE-SEM images clearly show the flakes incorporated cluster-like morphology. The BET surface area of ZnV and ZnV/PANI was found to be 22 m² g^-1 and 40 m² g^-1. The XPS results also confirm the successful formation of ZnV/PANI composite. The as-prepared samples were utilized as photocatalyst and electrode materials for energy applications. The ZnV/PANI composite showed an outstanding photocatalytic activity (94%) in the degradation of aqueous RhB dye under visible light irradiation. The optimum catalyst dosage for the degradation of 50 mL of 1 × 10^-5 M RhB dye aqueous solution was 50 mg. The Langmuir-Hinselwood (L-H) kinetic model proves that the photodegradation mechanism follows pseudo-first order kinetics. Further, the supercapacitive behavior of the ZnV/PANI composite was tested using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) techniques in 1 M KOH electrolyte at the potential window of 0-0.55 V. ZnV/PANI electrode displayed a specific capacitance (C_sp) of 664 F g^-1 at 1 A/g. The satisfactory performance of ZnV/PANI composite is mainly ascribed to the synergistic effect of ZnV-PANI matrixes with the occurrence of multiple electroactive sites in the composite. The cycling stability test proved that ZnV/PANI electrode material retained 92% of its initial capacitance even after 6000 GCD cycles at 2 A/g. The finding of this study will help to determine the most efficient and cost-effective method for the removal of dyes from textile industry wastewater and also as an effective material for supercapacitor applications.

Fabrication, characterization, and photocatalytic degradation potential of chitosan-conjugated manganese magnetic nano-biocomposite for emerging dye pollutants

The release of toxic dyes from different industries through industrial effluents cause hazardous effects to human and aquatic life. Therefore, the detoxification of such toxic pollutants is very important for a clean environment. In this regard, chitosan conjugated Mn-magnetic nano-biocomposite (Mn-CCMN) was synthesized, characterized, and applied for the photocatalytic decontamination of crystal violet (CV) dye in the contaminated aqueous system and industrial wastewater. The characterization was performed using SEM, XRD, EDX and FTIR spectroscopic techniques and determine PZC. The data shows the successfully synthesis of the resultant nano-biocomposite with amorphous nature and Fe and Mn were present therein. The SEM study revealed the flat and irregular shaped structure with porous surface and 87 ± 4 nm as mean particle size. The application of as-synthesized nano-biocomposite was determined as a photocatalyst for the eradication of CV in the aqueous environment under UV light illumination. The different photocatalysis conditions were studied for maximum degradation of CV and under the best experimental factors, tremendous CV degradation was attained in the real samples and industrial wastewater. The synthesized Mn-CCMN sustain excellent photocatalytic performance for four successive batches. The photocatalytic data was fitted to the pseudo-first-order kinetic model (R² = 0.992) having 0.007672 min^-1 and 0.0549 ppm/min as k and reaction rate, respectively. The statistical models such as response surface methodology (RSM) and artificial neural network-genetic algorithm (ANN-GA) were also applied for confirmation of the experimental data and the results showed a good agreement. It is deduced that the synthesized Mn-CCMN could be an excellent alternative to the present photocatalysts for the decontamination of toxic organic dyes from contaminated water and industrial wastewater.

Efficient removal of selected fluoroquinolones from the aqueous environment using reduced magnetic graphene oxide/polyaniline composite

In the present study, reduced magnetic graphene oxide/polyaniline (RmGO/PANI) composite was synthesized via in-situ oxidative polymerization method. The synthesized RmGO/PANI was characterized by fourier transform infrared, scanning electron microscope, X-ray diffraction and energy dispersive X-rays techniques. The synthesized RmGO/PANI was explored as an adsorbent for the removal of moxifloxacin (MOX) and ofloxacin (OFL) from the aqueous samples. To inflate removal efficiency of RmGO/PANI, various adsorption effecting parameters such as effect of pH (2-12), RmGO/PANI dosage (2-14 mg), analyte concentration (150-525 μg mL^-1 for MOX and 15-40 μg mL^-1 for OFL), contact time (10-120 min) and temperature (293-343 K) were studied. Moreover, kinetic study exhibits that adsorption of MOX/OFL using RmGO/PANI follows pseudo second order kinetic model. The adsorption of MOX/OFL well-fitted to the Langmuir adsorption isotherm which demonstrates mono-layer adsorption of MOX/OFL on the surface of RmGO/PANI with maximum adsorption capacity of 47.7 mg g^-1 and 27.33 mg g^-1 for OFL and MOX, respectively. Thermodynamic study indicates that the adsorption process was spontaneous and exothermic in nature with the decrease of randomness of the system during the adsorption. On account of its practical applications, RmGO/PANI is considered an excellent adsorbent with 99% and 96% removal efficacy for MOX and OFL, respectively. The synthesized RmGO/PANI was reused for ten consecutive batches as well as applied to the real samples, maintain an excellent removal capacity. The reusable nature of RmGO/PANI declare this solid medium as an innovative adsorbent for real sample applications and wastewater treatment.

Adsorption of Cationic Contaminants by Cyclodextrin Nanosponges Cross-Linked with 1,2,3,4-Butanetetracarboxylic Acid and Poly(vinyl alcohol)

Cationic organic pollutants (dyes and pesticides) are mainly hydrosoluble and easily contaminate water and create a serious problem for biotic and abiotic species. The elimination of these dangerous contaminants from water was accomplished by adsorption using cyclodextrin nanosponges. These nanosponges were elaborated by the cross-linking between 1,2,3,4-butanetetracarboxylic acid and β-cyclodextrin in the presence of poly(vinyl alcohol). Their physicochemical characteristics were characterized by gravimetry, acid-base titration, TGA, 13C NMR, ATR-FTIR, Raman, X-ray diffraction, and Stereomicroscopy. The BP5 nanosponges displayed 68.4% yield, 3.31 mmol/g COOH groups, 0.16 mmol/g β-CD content, 54.2% swelling, 97.0% PQ removal, 96.7% SO removal, and 98.3% MG removal for 25 mg/L of initial concentration. The pseudo-second-order model was suitable for kinetics using 180 min of contact time. Langmuir isotherm was suitable for isotherm with the maximum adsorption of 120.5, 92.6, and 64.9 mg/g for paraquat (PQ), safranin (SO), and malachite green (MG) adsorption, respectively. Finally, the reusability performance after five regeneration times reached 94.1%, 91.6%, and 94.6% for PQ, SO, and MG adsorption, respectively.

Preparation, characterization, and application of a homemade graphene for the removal of Congo red from aqueous solutions

Ethylene diaminetetraacetic acid (EDTA)-functionalized graphene was synthesized from Nigerian coal using a chemical exfoliation method and the graphene was applied for the removal of Congo red dye from aqueous solutions. The synthesized coal graphene and the raw coal were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM)-energy-dispersive X-ray (EDX) spectroscopy, measurement of pHpzc (pH of point of zero charge), and Boehm titrations. The SEM data revealed surface roughness which is enhanced in the prepared graphene while the EDX revealed an increase in carbon content, the main constituent of graphene, from about 26% in the raw coal to about 80% in the prepared graphene. Various adsorption variables, such as pH, contact time, concentration of Congo red, and temperature, were varied for the removal of the dye using raw coal and the synthesized coal graphene. The Liu isotherm gave the best fit of the equilibrium data than the Langmuir, Freundlich, and Dubinin-Radushkevich models. The maximum adsorption capacities of the raw coal and synthesized coal graphene at 25°C are 109.1 mg/g and 129.0 mg/g, respectively. The Avrami fractional-order kinetic model was the best model for description of the kinetic data. The model had the lowest values of standard deviation than the pseudo-first-order and pseudo-second-order models. The adsorption process of the two materials occurred via two stages as proved by intraparticle diffusion model. The adsorption process of the Congo red removal was spontaneous, feasible, and endothermic. The study conclusively revealed the graphene nanomaterial to be a viable adsorbent for textile wastewater treatment.