Cobalt ferrite nanoparticles prepared by microwave hydrothermal synthesis and adsorption efficiency for organic dyes: Isotherms, thermodynamics and kinetic studies

Enhanced degradation of Direct Red 80 dye via Fenton-like process mediated by cobalt ferrite: generated superoxide radicals and singlet oxygen

Azo dyes, widely used in the textile industry, contribute to effluents with significant organic content. Therefore, the aim of this work was to synthesize cobalt ferrite (CoFe2O4) using the combustion method and assess its efficacy in degrading the azo dye Direct Red 80 (DR80). TEM showed a spherical structure with an average size of 33 ± 12 nm. Selected area electron diffraction and XRD confirmed the presence of characteristic crystalline planes specific to CoFe2O4. The amount of Co and Fe metals were determined by ICP-OES, indicating an n(Fe)/n(Co) ratio of 2.02. FTIR exhibited distinct bands corresponding to Co-O (455 cm-1) and Fe-O (523 cm-1) bonds. Raman spectroscopy detected peaks associated with octahedral and tetrahedral sites. For the first time, the material was applied to degrade DR80 in an aqueous system, with the addition of persulfate. Consistently, within 60 min, these trials achieved nearly 100% removal of DR80, even after the material had undergone five cycles of reuse. The pseudo-second-order model was found to be the most fitting model for the experimental data (k2 = 0.07007 L mg-1 min-1). The results strongly suggest that degradation primarily occurred via superoxide radicals and singlet oxygen. Furthermore, the presence of UV light considerably accelerated the degradation process (k2 = 1.54093 L mg-1 min-1). The material was applied in a synthetic effluent containing various ions, and its performance consistently approached 100% in the photo-Fenton system. Finally, two degradation byproducts were identified through HPLC-MS/MS analysis.

Deciphering the photocatalytic degradation of polyaromatic hydrocarbons (PAHs) using hausmannite (Mn3O4) nanoparticles and their efficacy against bacterial biofilm

Polyaromatic hydrocarbons (PAHs) are life-threatening organic pollutants that severely threaten ecosystems worldwide due to their poisonous qualities, cancer-causing properties, and mutation-causing qualities. Water and soil together form a critical component of the ecosystem that supports all life. Due to the pollutants that are being disposed of in them, their characteristics have changed, and their toxicity has increased. The goal of this study was to investigate the ability of hausmannite nanoparticles to degrade fluorene from soil and water. Using the chemical method, hausmannite nanoparticles were synthesized and further characterization was performed using UV-Vis, FTIR, DLS, XRD, and SEM-EDAX. Hausmannite significantly degraded fluorene using the batch adsorption method. The degradation was also confirmed by performing reactive kinetics using Freundlich's isotherm model and Langmuir's pseudo-second-order model of soil and water. In addition to the degradation efficacy, hausmannite was also proved to inhibit biofilm formation by Pseudomonas aeruginosa. The findings of the experiments confirmed the presence of hausmannite nanoparticles, as well as their physical properties, chemical properties, degradation properties, and parameters of the kinetic study. As a result, synthesized nanoparticles have been extensively utilized as a low-cost option for removing pollutants and microbial biofilm.

Statistically Analyzed Heavy Metal Removal Efficiency of Silica-Coated Cu0.50Mg0.50Fe2O4 Magnetic Adsorbent for Wastewater Treatment

Even low concentrations of pollutants in water, particularly heavy metals, can significantly affect the ecosystem and human health. Adsorption has been determined to be one of the most effective techniques of removing pollution from wastewater among the various strategies. To remove heavy metals such as Zn2+ and Pb2+, we prepared a silica-coated CuMgFe2O4 magnetic adsorbent using sol-gel method and tested it for wastewater treatment. X-ray diffraction investigation validated the creation of cubic spinel structure, while morphological analysis showed that silica coating reduces the particle size but boosts the surface roughness of the nanoparticles and also reduces the agglomeration between particles. UV-visible spectroscopy indicates a rise in bandgap and magnetic characteristics analysis indicates low values of magnetization due to silica coating. The kinetic and isotherm parameters for heavy metal ions adsorption onto silica-coated Cu0.50Mg0.50Fe2O4 nanoparticles are calculated by applying pseudo-first-order, pseudo-second-order, Langmuir and Freundlich models. Adsorption kinetics revealed that the pseudo-second-order and Langmuir models are the best fit to explain adsorption kinetics. Synthesized adsorbent revealed 92% and 97% removal efficiencies for Zn2+ and Pb2+ ions, respectively.

A simple microwave-assisted synthesis of cobalt ferrite nanoparticles and its application for the determination of lead ions in rooibos (Aspalathus linearis) tea

In this study, a magnetic sorbent assisted dispersive solid phase extraction (DSPE) method was used to preconcentrate lead ions from rooibos tea samples for determination by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS). Cobalt ferrite magnetic nanoparticles (CoFe2O4 MNPs) were synthesized by microwave assisted digestion. Limits of detection and quantification were calculated as 5.3 and 17.6 µg/L, respectively, in a linear dynamic range of 20-800 µg/L. The enhancement factor of the developed method was found to be 80-folds when compared to the detection limit of the regular FAAS system. The percent recoveries obtained for rooibos tea samples spiked at different concentrations were in the range of 77 - 125%, with high repeatability as indicated by low standard deviations. The findings of the study demonstrated that the CoFe2O4 MNPs-based extraction method is a straightforward, fast, affordable, safe, and eco-friendly approach to qualifying/quantifying lead with high precision in the selected beverage sample.

Synthesis and characterization of nanoparticles of cobalt and nickel ferrites for elimination of hazardous organic dyes from industrial wastewater

This study presents the results of synthesis and characterization of nanoparticles of cobalt ferrite (CoFe₂O₄) and nickel ferrite (NiFe₂O₄) using co-precipitation method followed by application for removal of hazardous organic textile dyes of thiazole yellow G (TYG) and alizarin yellow R (AYR). XRD analysis confirmed formation of cubic spinel structure with average crystallite sizes at 16.07 nm and 13.84 nm for CoFe₂O₄ and NiFe₂O₄, respectively. Field emission scanning electron microscopy (FESEM) analysis showed agglomeration of spherical shape morphology with uniformly distributed Co, Ni, Fe, and O elements. The surface area calculated from Brunauer-Emmett-Teller (BET) analysis was 64 m²/g and 62 m²/g for CoFe₂O₄ and NiFe₂O₄, respectively. Vibrating sample magnetometer (VSM) showed super-paramagnetic behavior for all samples with magnetic saturation (M_s) at 7.269 and 6.61 emu/g for CoFe₂O₄ and NiFe₂O₄, respectively. The adsorption influencing parameters such as pH of solution, quantity of adsorbent, and contact time on dye removal efficiency were thoroughly investigated. Overall, acidic condition of samples with pH at 4 favored the maximum removal efficiency by CoFe₂O₄ as 98, 97, and 93%, and by NiFe₂O₄ as 96, 93, and 92%, respectively, for TYG, AYR, and mixture sample. The Langmuir adsorption isotherm model describes the equilibrium of all samples with the best fit of coefficient of determination (R²). The adsorption results fitted well with a pseudo-second-order kinetic model for all samples. The regeneration-reuse ability of adsorbents and cost estimation analysis of the dye removal process suggested that the economic suitability of nano-adsorbents for remediation of textile effluents was favored. The estimated thermodynamic parameters inferred that the removal of organic dyes onto the surface of CoFe₂O₄ and NiFe₂O₄ is a spontaneous, favorable, and exothermic physical adsorption process.

Green synthesis of CuO nanoparticles using Peganum harmala extract for photocatalytic and sonocatalytic degradation of reactive dye and organic compounds

 The present study was performed to evaluate the effectiveness of photocatalytic and sonocatalytic processes for the removal of reactive blue 5 dye and organic compounds of textile effluent in the presence of copper oxide nanoparticles (CuO NPs). CuO NPs were synthesized using Peganum harmala seed extract. The structure of NPs was confirmed using SEM, TEM, XRD, EDX, and FTIR techniques. The tests were carried out in a batch system to assess factors affecting the dye removal efficiency, including contact time, pH, NPs dosage, and initial dye concentration. The experimental results showed that the photocatalytic process (98.42%) produced a higher degradation percentage than the sonocatalytic process (76.16%). While, the dye removal efficiency was not significant in the dark conditions (without UV or US waves). The maximum removal of reactive blue 5 dye under photocatalytic and sonocatalytic conditions occurred at the presence of 0.15 g of CuO NPs and dye concentration of 40 and 60 mg/L, respectively. The kinetic data followed a pseudo-second-order model in both photocatalytic and sonocatalytic processes with a correlation coefficient higher than 0.99. Isotherm studies showed that the Langmuir model was the best isothermal model to describe the adsorptive behavior of CuO NPs in a dark condition. The results obtained from GC-MS showed that the photocatalytic process had a degradation efficiency of over 87% in the removal of organic compounds.

A feasible biochar derived from biogas residue and its application in the efficient adsorption of tetracycline from an aqueous solution

The recovery of carbon materials from biogas residue (BR) could efficiently promote the efficient utilization of waste and the preparation of novel materials. In this study, a green and feasible reagent of citric acid was introduced and applied in the modification of biogas residue biochar (BRC). The modified biogas residue biochar (CABRC) showed a superior adsorption ability due to its higher specific surface area (approximately 6 times that of the BRC). Additionally, the adsorption capacities of CABRC and BRC for TC were 58.25 mg/g and 20.77 mg/g, respectively, while the TC adsorption performance of CABRC was 2.8 times that of BRC. The adsorption of TC by both BRC and CABRC was primarily controlled by physical adsorption and chemical adsorption (including pore filling, hydrogen bonding, π-π DEA interaction, and electrostatic interaction). Therefore, CABRC should be considered an environmentally friendly material due to its higher adsorption performance, which could expand its application in wastewater treatment.

Effective mitigation of single-component and mixed textile dyes from aqueous media using recyclable graphene-based nanocomposite

The present study reported the synthesis and utilization of a graphene-based hybrid nanocomposite (MnFe₂O₄/G) to mitigate several synthetic dyes, including methylene blue, malachite green, crystal violet, and Rhodamine B. This adsorbent was structurally analyzed by several physicochemical techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, N₂ adsorption-desorption isotherm measurement, point of zero charge, and Boehm titrations. BET surface area of MnFe₂O₄/G was measured at 382.98 m²/g, which was substantially higher than that of MnFe₂O₄. MnFe₂O₄/G possessed diverse surface chemistry properties with the presence of many functional groups such as carboxylic acid, phenolic, lactone, and basic groups. MnFe₂O₄/G was used to remove synthetic dyes in the aqueous media. The effect of many factors, e.g., concentration (5-50 mg/L), pH (4-10), dose (5-20 mg), and temperature (25-45 °C) on adsorption performance of MnFe₂O₄/G was conducted. Kinetic, isotherm, intraparticle, and thermodynamic models were adopted for investigating adsorption phenomenon of dyes on MnFe₂O₄/G. The maximum adsorption capacity of dyes over MnFe₂O₄/G was found as Rhodamine B (67.8 mg/g) < crystal violet (81.3 mg/g) < methylene blue (137.7 mg/g) < malachite green (394.5 mg/g). Some tests were performed to remove mixed dyes, and mixed dyes in the presence of antibiotics with total efficiencies of 65.8-87.9% after 120 min. Moreover, the major role of π-π stacking interaction was clarified to gain insight into the adsorption mechanism. MnFe₂O₄/G could recycle up to 4 cycles, which may be beneficial for further practical water treatment.

Facile Synthesis of Cobalt Ferrite (CoFe2O4) Nanoparticles in the Presence of Sodium Bis (2-ethyl-hexyl) Sulfosuccinate and Their Application in Dyes Removal from Single and Binary Aqueous Solutions

A research study was conducted to establish the effect of the presence of sodium bis-2-ethyl-hexyl-sulfosuccinate (DOSS) surfactant on the size, shape, and magnetic properties of cobalt ferrite nanoparticles, and also on their ability to remove anionic dyes from synthetic aqueous solutions. The effect of the molar ratio cobalt ferrite to surfactant (1:0.1; 1:0.25 and 1:0.5) on the physicochemical properties of the prepared cobalt ferrite particles was evaluated using different characterization techniques, such as FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption analysis, and magnetic measurements. The results revealed that the surfactant has a significant impact on the textural and magnetic properties of CoFe₂O₄. The capacity of the synthesized CoFe₂O₄ samples to remove two anionic dyes, Congo Red (CR) and Methyl Orange (MO), by adsorption from aqueous solutions and the factors affecting the adsorption process, such as contact time, concentration of dyes in the initial solution, pH of the media, and the presence of a competing agent were investigated in batch experiments. Desorption experiments were performed to demonstrate the reusability of the adsorbents.

Enhanced Adsorption of Rhodamine B on Modified Oil-Based Drill Cutting Ash: Characterization, Adsorption Kinetics, and Adsorption Isotherm

In this paper, phosphoric acid (H₃PO₄), hydrochloric acid (HCl), and hydrogen peroxide (H₂O₂) were employed for the modification of oil-based drill cutting ash (OBDCA) for the first time. The adsorption of rhodamine B (RhB) on modified oil-based drill cutting ash (MOBDCA) in an aqueous medium was investigated. H₂O₂-modified OBDCA had the optimal adsorption efficiency for RhB. The physical and chemical properties of MOBDCA were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ζ-potential, N₂ adsorption-desorption isotherm, and pore size distribution. The effect of the pH value (3-11), reaction time (10-720 min), and initial RhB concentration (10-200 mg/L) on RhB adsorption was discussed. The adsorption kinetics highly fitted with the pseudo-second-order model (R ² > 0.99), which indicated that the adsorption process was dominated by chemisorption. The adsorption isotherm fitted well with the Langmuir and Freundlich models (R ² > 0.97), which indicated the monolayer adsorption process and the heterogeneous adsorption process, respectively. The theoretic adsorption capacity (50 mg/g) for RhB was achieved by H₂O₂-modified OBDCA. This paper provides a promising method of resource utilization of OBDCA to treat organic pollutants.

Development of highly efficient and reusable magnetic nitrogen-doped carbon nanotubes for chlorophenol removal

Nitrogen-doped carbon nanotubes (N-CNTs) were synthesized via a hydrothermal method and further modified with magnetic Co_0.5Cu_0.5Fe₂O₄ nanoparticles following a one-pot solvothermal method. The characterization data show that the distribution of the magnetic materials and the adsorption characteristics of the CNTs can be tailored as a function of the N doping amount. The N-CNT adsorption isotherms as a function of N content and chlorophenol uptake show that a N doping level of 6% is optimum. After loading the N-CNTs with the magnetic Co_0.5Cu_0.5Fe₂O₄ nanoparticles (M-N-CNTs), the resulting materials were easily dispersed in aqueous media with specific surface area reaching 95.64 m²/g. The M-N-CNTs exhibit high affinities toward the adsorption of different chlorophenols following the order: Pentachlorophenol (PCP) > 2,4,6-trichlorophenol (2,4,6-TCP) > 2,4-dichlorophenol (2,4-DCP) > 2,4-dichlorophenoxyacetic acid (2,4-D) > phenol. Additionally, the M-N-CNTs exhibit good microwave absorption performance and can be regenerated by microwave irradiation with high efficiencies (> 90%) maintained with high stabilities.