Comparative Study of CoFe2O4 Nanoparticles and CoFe2O4-Chitosan Composite for Congo Red and Methyl Orange Removal by Adsorption

Hydrogels Based on Chitosan and Nanoparticles and Their Suitability for Dyes Adsorption from Aqueous Media: Assessment of the Last-Decade Progresses

Water is one of the fundamental resources for the existence of humans and the environment. Throughout time, due to urbanization, expanding population, increased agricultural production, and intense industrialization, significant pollution with persistent contaminants has been noted, placing the water quality in danger. As a consequence, different procedures and various technologies have been tested and used in order to ensure that water sources are safe for use. The adsorption process is often considered for wastewater treatment due to its straightforward design, low investment cost, availability, avoidance of additional chemicals, lack of undesirable byproducts, and demonstrated significant efficacious potential for treating and eliminating organic contaminants. To accomplish its application, the need to develop innovative materials has become an essential goal. In this context, an overview of recent advances in hydrogels based on chitosan and nanocomposites and their application for the depollution of wastewater contaminated with dyes is reported herein. The present review focuses on (i) the challenges raised by the synthesis process and characterization of the different hydrogels; (ii) the discussion of the impact of the main parameters affecting the adsorption process; (iii) the understanding of the adsorption isotherms, kinetics, and thermodynamic behavior; and (iv) the examination of the possibility of recycling and reusing the hydrogels.

An Updated Overview of Magnetic Composites for Water Decontamination

Water contamination by harmful organic and inorganic compounds seriously burdens human health and aquatic life. A series of conventional water purification methods can be employed, yet they come with certain disadvantages, including resulting sludge or solid waste, incomplete treatment process, and high costs. To overcome these limitations, attention has been drawn to nanotechnology for fabricating better-performing adsorbents for contaminant removal. In particular, magnetic nanostructures hold promise for water decontamination applications, benefiting from easy removal from aqueous solutions. In this respect, numerous researchers worldwide have reported incorporating magnetic particles into many composite materials. Therefore, this review aims to present the newest advancements in the field of magnetic composites for water decontamination, describing the appealing properties of a series of base materials and including the results of the most recent studies. In more detail, carbon-, polymer-, hydrogel-, aerogel-, silica-, clay-, biochar-, metal-organic framework-, and covalent organic framework-based magnetic composites are overviewed, which have displayed promising adsorption capacity for industrial pollutants.

Process Optimization and Equilibrium, Thermodynamic, and Kinetic Modeling of Toxic Congo Red Dye Adsorption from Aqueous Solutions Using a Copper Ferrite Nanocomposite Adsorbent

In the present investigation of copper ferrite, a CuFe2O4 nanocomposite adsorbent was synthesized using the sol-gel method, and its relevance in the adsorptive elimination of the toxic Congo red (CR) aqueous phase was examined. A variety of structural methods were used to analyze the CuFe2O4 nanocomposite; the as-synthesized nanocomposite had agglomerated clusters with a porous, irregular, rough surface that could be seen using FE-SEM, and it also contained carbon (23.47%), oxygen (44.31%), copper (10.21%), and iron (22.01%) in its elemental composition by weight. Experiments were designed to achieve the most optimized system through the utilization of a central composite design (CCD). The highest uptake of CR dye at equilibrium occurred when the initial pH value was 5.5, the adsorbate concentration was 125 mg/L, and the adsorbent dosage was 3.5 g/L. Kinetic studies were conducted, and they showed that the adsorption process followed a pseudo-second-order (PSO) model (regression coefficient, R2 = 0.9998), suggesting a chemisorption mechanism, and the overall reaction rate was governed by both the film and pore diffusion of adsorbate molecules. The process through which dye molecules were taken up onto the particle surface revealed interactions involving electrostatic forces, hydrogen bonding, and pore filling. According to isotherm studies, the equilibrium data exhibited strong agreement with the Langmuir model (R2 = 0.9989), demonstrating a maximum monolayer adsorption capacity (qmax) of 64.72 mg/g at pH 6 and 302 K. Considering the obtained negative ΔG and positive ΔHads and ΔSads values across all tested temperatures in the thermodynamic investigations, it was confirmed that the adsorption process was characterized as endothermic, spontaneous, and feasible, with an increased level of randomness. The CuFe2O4 adsorbent developed in this study is anticipated to find extensive application in effluent treatment, owing to its excellent reusability and remarkable capability to effectively remove CR in comparison to other adsorbents.

Production of Ni0.5Co0.5Fe2O4/activated carbon@chitosan magnetic nanobiocomposite as a novel adsorbent of methylene blue in aqueous solutions

Methylene blue is a cationic dye, not degraded naturally due to its aromatic rings. Accordingly, biological, chemical, and physical water treatment methods have been proposed for its removal. Adsorption is an economical and effective method in this regard. In this study, the nickel-cobalt ferrite/activated carbon@chitosan magnetic nanobiocomposite was synthesized as an adsorbent. The nano-adsorbent was evaluated with FESEM, which estimated the particle size at ~ 16.64 nm. According to EDAX analysis, the purity of particles was 99%. XRD characterization showed the successful coverage of chitosan, correct placement of nickel-cobalt ferrite, and the nono-structure of crystallites. The specific surface area was 316 m2/g using the BET theory and 285 m2/g using the Langmuir theory, and the porosity volume was 0.18 cm3/g. According to the VSM analysis, magnetic reluctance and coercive force were 1.1 emu/g and 499 Oe, respectively. The FTIR analysis showed that the reaction was successful, and methylene blue was present on the adsorbent surface. The methylene blue adsorption test indicated that 388 mg/g of the dye was adsorbed (97% dye removal), and the final concentration reached 6 mg/L after 8 h. The point of zero charge (pHpzc) was 6.8.

CoFe2O4@HaP as Magnetic Heterostructures for Sustainable Wastewater Treatment

The aim of this study was to synthesize a CoFe₂O₄@HaP nanocomposite (HaP-Hydroxyapatite) through the coprecipitation method in aqueous solution, with the purpose of using it in adsorption processes for the removal of Congo Red dye from aqueous solutions. Fourier Transform Infrared Spectroscopy (FT-IR) was used to characterize the synthesized material, identifying absorption bands specific to the functional groups of cobalt ferrite (Fe-O and Co-O at 603 and 472 cm^-1) and hydroxyapatite PO₄^3- at 1035, 962, 603 and 565 cm^-1. Powder X-ray diffraction confirmed the cubic spinel structure of cobalt ferrite (S.G Fd-3m) and the hexagonal structure of hydroxyapatite (S.G P63/m). The nanocomposite's crystallite size was calculated to be 57.88 nm. Nitrogen adsorption/desorption isotherms and BET specific surface area measurements were used to monitor textural parameters, revealing an increase in specific BET surface area when cobalt ferrite nanoparticles (15 m²/g) were introduced into the hydroxyapatite heterostructure (34 m²/g). Magnetic properties were investigated by interpreting hysteresis curves in the ±10 kOe range, with the nanocomposite showing a saturation magnetization of 34.83 emu/g and a coercivity value of 0.03 kOe. The adsorption capacity of the CoFe₂O₄@HaP nanocomposite is up to 15.25 mg/g and the pseudo-second-order kinetic model (Type 1) fits the data with a high correlation coefficient of 0.9984, indicating that the chemical adsorption determines the rate-determining step of the process. The obtained nanocomposite is confirmed by the analyses, and the absorption measurements demonstrate that it can be utilized to degrade Congo Red dye.

Adsorption Properties of Modified ATP-RGO Composite Aerogel for Removal of Malachite Green and Methyl Orange from Unitary and Binary Aqueous Solutions

In this paper, the modified attapulgite-reduced graphene oxide composite aerogel (ATP-RGO CA) was prepared by sol-gel method using modified attapulgite as silica source. The removal of the cationic dye malachite green (MG) and azo dye methyl orange (MO) onto ATP-RGO CA from unitary and binary systems was investigated. Morphology and microstructure studies of ATP-RGO CA were investigated by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and specific surface area and porosity analysis. Experiments were carried out as a function of pH, contact time, initial dye concentration, and temperature in unitary and binary systems. The adsorption kinetics, isotherms, thermodynamics, and dye desorption were studied in unitary and binary dye systems. The adsorption kinetics was modeled using the pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics equations. The equilibrium adsorption data of MG and MO dyes on ATP-RGO CA were analyzed. Thermodynamic parameters of dye adsorption were obtained. In addition, the regeneration of ATP-RGO CA was studied using dye desorption in unitary and binary dye systems. The adsorption kinetics of the dyes followed pseudo-second-order kinetics. The results indicate that the Langmuir model provides the best correlation of the experimental data. The thermodynamic studies showed that the dye adsorption onto ATP-RGO CA was a spontaneous and endothermic reaction. High desorption of MG and MO showed the regeneration of ATP-RGO CA. It can be concluded that ATP-RGO CA is suitable as an adsorbent material to remove MG and MO dyes from unitary and binary systems.

Reusable kaolin impregnated aminated chitosan composite beads for efficient removal of Congo red dye: isotherms, kinetics and thermodynamics studies

In this investigation, Kaolin (K) impregnated aminated chitosan (AM-CTS) composite beads were fabricated with multi-features including low-cost, high performance, renewable and ease of separation for adsorption of anionic Congo red (CR) dye. Characterization tools such as FTIR, XRD, SEM, TGA, BET, XPS and Zeta potential were thoroughly employed to confirm the successful formulation process. The results revealed that K@ AM-CTS composite beads displayed higher specific surface area (128.52 m²/g), while the thermal stability was prominently improved compared to pure AM-CTS. In addition, the adsorption equilibrium of CR dye was accomplished rapidly and closely gotten within 45 min. The removal efficiency was significantly enriched and reached 90.7% with increasing kaolin content up to 0.75%, compared to 20.3 and 58% for pristine kaolin and AM-CTS, respectively. Moreover, the adsorption process obeyed the pseudo-first order kinetic model, while data were agreed with the Freundlich isotherm model with a maximum adsorption capacity reached 104 mg/g at pH 6. Furthermore, D–R isotherm model demonstrated the physical adsorption process of CR dye, which includes the electrostatic interactions, ion exchange and H-bonding. Thermodynamics evidenced the spontaneous and endothermic nature of the adsorption process. Interestingly, the developed K@AM-CTS composites beads showed better reusability for eight consecutive cycles, suggesting their feasible applicability for adsorptive removal anionic dyes from polluted aquatic bodies.

Recent advances in magnetic composites as adsorbents for wastewater remediation

The scarcity of clean drinking water combined with other environmental and anthropogenic effects necessitates the demand for development of advanced technology for cleaning polluted water. Adsorption is one such technique that does not produce toxic byproducts and solves the problem of cleaning contaminated water at a lower cost. In recent years, magnetic composites, as adsorbent, have gained lot of attention due to their reusability which makes them sustainable and economical. This review article describes the challenges related to water quality, scarcity and then summarizes the current treatment technologies and advancement in the field of adsorption to resolve the prevailing concerns. The review includes an insight into the recent research being carried out in the field of magnetic composites and nanocomposites, as adsorbent, covering, probably, all aspects of what is going around the globe. Different materials, like polymers, biomaterials, clays and metal organic framework (MOF)-based magnetic composites and their applications in wastewater treatment processes have been included. The article is a comprehensive review on the application of different materials to detoxify various diverse pollutants with prime focus on magnetic composites. The thorough study of this review will surely bring upcoming researchers closer to the future possibilities of research in wastewater 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.

Magnetic Nitrogen-Doped Porous Carbon Nanocomposite for Pb(II) Adsorption from Aqueous Solution

We report in the present study the in situ formation of magnetic nanoparticles (Fe3O4 or Fe) within porous N-doped carbon (Fe3O4/N@C) via simple impregnation, polymerization, and calcination sequentially. The synthesized nanocomposite structural properties were investigated using different techniques showing its good construction. The formed nanocomposite showed a saturation magnetization (Ms) of 23.0 emu g-1 due to the implanted magnetic nanoparticles and high surface area from the porous N-doped carbon. The nanocomposite was formed as graphite-type layers. The well-synthesized nanocomposite showed a high adsorption affinity toward Pb2+ toxic ions. The nanosorbent showed a maximum adsorption capacity of 250.0 mg/g toward the Pb2+ metallic ions at pH of 5.5, initial Pb2+ concentration of 180.0 mg/L, and room temperature. Due to its superparamagnetic characteristics, an external magnet was used for the fast separation of the nanocomposite. This enabled the study of the nanocomposite reusability toward Pb2+ ions, showing good chemical stability even after six cycles. Subsequently, Fe3O4/N@C nanocomposite was shown to have excellent efficiency for the removal of toxic Pb2+ ions from water.

Polyethylenimine-Modified Magnetic Chitosan for the Uptake of Arsenic from Water

The removal of heavy metals from water has become a global environmental problem. Various materials have been applied as adsorbent to remove metals from water. In this field, nanomaterials have been gaining increasing interest due to their exceptional properties. In this work, we discuss the synthesis of a core-shell structure nanocomposite by the modification of magnetic chitosan (CS) (Fe3O4/CS) with polyethylenimine (PEI) to produce Fe3O4/CS/PEI composite for the adsorption of arsenic ions (As(V) and As(III)) from aqueous solution. The synthesized materials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). The results indicated the successful combination of three components of the nanocomposite. The adsorption conditions were optimized by studying the effect of different parameters included pH, contact time, initial concentration, and adsorbent dosage. The optimum adsorption pH was found to be 6.7 while the optimum adsorbent dosage was found to be 2.0 and 1.5 g/L for As(III) and As(V), respectively. The removal efficiency for the uptake of As(III) and As(V) ions over Fe3O4/CS/PEI nanocomposite at optimum conditions was found to be 99.5 and 99.7%, respectively. The experimental results were fitted using Freundlich’s and Langmuir’s isotherms. The data were more fitted to Langmuir isotherm providing a suggestion of monolayer adsorption with maximum adsorption capacity equal to 77.61 and 86.50 mg/g for the removal of As(III) and As(V), respectively. Moreover, linear regression coefficient (R2) indicated that the adsorption of arsenic ions over the synthesized magnetic nanocomposite obeyed pseudo 2nd order suggesting the chemisorption process. The reusability of the nanosorbent for arsenic uptake using sodium hydroxide as eluent was also assessed up to five cycles. Interestingly, Fe3O4/CS/PEI nanocomposite can be considered as a promising adsorbent for As ions’ removal from water and should be tested for the removal of other pollutants.