A comprehensive review of applications of magnetic graphene oxide based nanocomposites for sustainable water purification

Recent advancements on 2D nanomaterials as emerging paradigm for the adsorptive removal of microcontaminants

Water reservoirs are facing increasing prevalence of microcontaminants originating from agricultural runoff, industrial effluents, and domestic wastewater. The persistence of microcontaminants leads to disruptions in aquatic ecosystems and poses potential long-term health risks to humans, even at minimal concentrations. However, traditional wastewater treatment methods are inefficient to eliminate the microcontaminants because of their intricate chemical structures and low concentration. In this regard, nano-adsorption employing nanomaterials as adsorbents presents a viable alternative, offering enhanced efficiency and specificity towards the removal of microcontaminants. Amongst all, two-dimensional (2D) nanomaterials, including graphene oxide (GO), layered double hydroxides (LDHs), MXenes, and boron nitrides (BNs), exhibit distinctive characteristics such as a high surface area, remarkable chemical stability, and tendency of diverse surface functionalization, rendering them particularly effective in adsorbing pollutants from water. Therefore, the present review provides an exhaustive literature and comparative analysis of the aforementioned 2D nanomaterials-based adsorbents concerning their efficacy in adsorbing microcontaminants of pharmaceuticals and personal care products origin such as antibiotics, steroids, bisphenols, phthalates, parabens, and benzophenones. The different aspects of 2D adsorbents including adsorption capacity, mechanisms involved, kinetic and isotherm models followed for removal of a variety of microcontaminants have been congregated. Also, the information on recyclability, reusability, and stability of the adsorbents has been summarized to highlight their viability. Further, the limitations and future aspects related to the use of 2D nanomaterials-based adsorbents towards pollutant removal have been discussed. Overall, 2D nanomaterials holds great promise as efficient adsorbents for environmental remediation and can also be explored for industrial adsorption applications.

Efficient adsorption and photocatalytic removal of hexavalent chromium using chitosan-functionalized graphene oxide-MnO2 nanocomposite

Graphene oxide/MnO2/chitosan (GO/MnO2/CS) nanocomposite showed distinct morphological changes and improved adsorption properties in wastewater treatment as compared to individual GO. GO was synthesized using modified Hummer's method and then functionalized with MnO2 nanoparticles and chitosan to prepare two nanocomposites: GO/MnO2 and GO/Mn2/CS. Nanocomposites characterized by UV/Visible spectroscopy, XRD, FTIR, SEM, and TGA. The average crystallite sizes calculated from XRD analysis were 30 nm for GO/MnO2 and 31 nm for GO/MnO2/CS. The nanocomposite showed a red shift in band gap from 3.85 eV (GO) to 2 eV (GO/MnO2/CS), which led to enhanced adsorption capacity and photocatalytic activity. Adsorption experiments were conducted to assess the elimination of Cr (VI) ions by synthesized nanomaterials at various operational conditions. The maximum adsorption capacities (qmax) were 131.58, 150.64 and 179.28 mg/g for GO, GO/MnO2, and GO/MnO2/CS respectively, at pH 2. The adsorption behavior of Cr (VI) onto the synthesized nanocomposites followed the Freundlich isotherm model, indicating multilayer adsorption on a heterogeneous surface. Kinetic studies revealed that the process followed a pseudo-second-order model, suggesting chemisorption as the dominant mechanism.

Zinc oxide-loaded chitosan-graphene oxide hydrogel nanocomposite as a potential catalyst for photocatalytic dye degradation

In this work, a novel in-situ approach was employed to incorporate the zinc oxide (ZnO) nanoparticles into the hybrid chitosan-graphene oxide (CSGO) hydrogel network, forming ZnO-embedded hydrogel nanocomposites (CSGOZnO). This endeavor offered a uniform dispersion of ZnO nanoparticles within the 3D polymeric hydrogel structure, as confirmed by FE-SEM and HR-TEM analyses. The XRD spectrum of CSGOZnO exhibited eleven characteristic crystal planes at 31.8, 34.5, 36.3, 47.6, 56.6, 62.9, 66.4, 68.0, 69.1, 72.6 and 77.0 (2θ), corresponding to enhanced crystallinity and structural integrity. The as-prepared hydrogel nanocomposite demonstrated outstanding potential to act as a catalyst for the photocatalytic degradation of cationic methylene blue (MB), anionic alizarin red (AR), and mixed dyes under visible-light. The dye degradation process followed the pseudo-second-order model, with rate constants of 5.0 × 10-3, 3.0 × 10-3, and 1.0 × 10-3 min-1 for MB, AR, and mixed dyes, respectively. The exceptional performance was attributed to the synergistic effects of the CSGO 3D gel network and the embedded ZnO nanoparticles, facilitating superior adsorption and photocatalytic degradation. To elucidate the degradation mechanism, a number of batch experiments were conducted in line with studying different parameters such as catalyst dosage, initial dye concentration, contact time and pH of the solution. Hence, the newly developed multifunctional CSGOZnO hydrogel nanocomposites, synthesized via an in-situ approach, demonstrate significant promise for photocatalytic degradation of organic dye molecules in contaminated water.

Advances in graphene-based nanomaterials for heavy metal removal from water: Mini review

The environment and public health are seriously at risk from the increasing levels of heavy metal (HM) pollution in water bodies, hence efficient remediation techniques must be developed. Unique physicochemical properties of graphene (Gn) such as its enormous surface area, chemical stability, and extraordinary adsorption capabilities have made it a promising candidate for application in various adsorption processes. Recent studies indicate the heavy metal removal capabilities of Gn-based materials such as Gn oxide (GO) and reduced GO (rGO) reach 99% efficiency rates for lead (Pb2+), cadmium (Cd2+), and mercury (Hg2+) through strong electrostatic bonds and metal coordination along with π-π stacking interactions. In addition, the selective nature of Gn-based adsorbents grows better through functionalization because it incorporates thiol, amine, and sulfonic acid groups. The integration of Gn-based materials with metal-organic frameworks (MOFs) combined with magnetic nanoparticles along with bio-based polymers enhances adsorption efficiency and increases stability while offering recyclability features. The conclusion of this study discusses the current obstacles such as cost, scalability, environmental impact, and selectivity and potential future developments for the widespread use of Gn-based adsorbents in water treatment, highlighting the significance of continued research to improve these substances for useful environmental applications. PRACTITIONER POINTS: Graphene-based materials exhibit high capacity for adsorbing various heavy metals, enhancing water purification. Functionalization of graphene improves its ability to selectively target and remove specific heavy metals like mercury and lead. Graphene derivatives can achieve heavy metal removal within minutes, making them efficient for water treatment. Despite high synthesis costs, graphene's superior performance may lower long-term operational costs in wastewater treatment.

Preparation, characterization, and pesticide adsorption capacity of chitosan-magnetic graphene oxide nanoparticles with toxicological studies

This study investigated magnetic graphene oxide nanoparticles (MGO-NPs) and functionalized with chitosan (CS-MGO-NPs) for removing florasulam, metalaxyl, and thiamethoxam pesticides from water. A comprehensive characterization employing Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), zeta potential measurements, XRD analysis, and surface area/porosity determinations confirmed the successful synthesis of the composites with the desired properties. Factorial experimental design was applied to identify the most significant factors of pesticide concentration, adsorbent amount, temperature, pH, agitation time, and ionic strength on the efficiency of removal of tested pesticides from water samples. CS-MGO-NPs exhibited superior removal efficiencies for all three pesticides compared to MGO-NPs. They achieved high removal rates for florasulam (average 92.94%) and metalaxyl (average 88.95%), while demonstrated moderate effectiveness against thiamethoxam (average 64.04%). Different kinetic and isotherm models described how well the nanoparticles adsorbed each pesticide. According to these models, the pseudo-first-order kinetic model interpreted well the adsorption of florasulam, and thiamethoxam onto CS-GO-NPs. While the pseudo-second-order kinetic model interpreted well the adsorption of metalaxyl. The Freundlich isotherm model gave the best fit with florasulam onto CS-GO-NPs. While the Langmuir isotherm model gave the best fit with metalaxyl and thiamethoxam. Finally, the toxicological studies of CS-MGO-NPs in rats were performed, and it was found negative effects at high doses, suggesting caution is needed for practical applications. Overall, this study shows promise for CS-MGO-NPs in water purification, but safety needs further investigation.

Photocatalytic Degradation of Dyes in Wastewater Using Solar Enhanced Nickel Oxide (NiO) Nanocatalysts Prepared by Chemical Methods

This study examined the surface morphology and photocatalytic activity of nickel oxide (NiO) nanoparticles prepared through a chemical method. The synthesized nanoparticle was characterized by using spectroscopic and microscopic techniques. Photocatalytic degradation of hazardous Eriochrome Black T (EBT) was carried out using the synthesized nanoparticle and the efficiency of the NiO used was determined. Highest degradation efficiency of 70% at 25 mg loading was observed at 40 min exposure time. The study concluded that the synthesized nanoparticles could be used in industrial wastewater treatment containing organic dyes.

Facile fabrication of novel magnetic chitosan-alginate @ pomegranate peel extract nanocomposite for the adsorptive removal of naphthalene from aqueous solutions

The prevalent presence of naphthalene contamination in aquatic ecosystems is a significant concern due to its carcinogenic and priority pollutant properties. This study focuses on the synthesis of magnetized chitosan/alginate/pomegranate peel extract nanocomposites (Fe3O4/PPE/Cs-Alg), was characterized by Zeta potential, vibrating sample magnetometer (VSM), Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The results predicted that the successfully synthesis of Fe3O4/PPE/Cs-Alg. The study evaluates the efficacy of the nanocomposite in naphthalene removal, considering operational parameters like pH, varied initial naphthalene concentrations, nanocomposite doses and contact time . The maximum adsorption capacities of naphthalene optimal conditions were 88.12 mg/g for 50 ppm initial naphthalene concentration. The Langmuir, Freundlich, Temkin and Sips isotherms were applied to analyze the experimental equilibrium data. The Sips isotherm was identified as the most suitable model, as evidenced by the highest (R2 = 0.97), Also, the adsorption data conformed well to the pseudo-second-order kinetics model (R2 = 0.99). The thermodynamic study showed positive values for ΔH° and ΔS° throughout the adsorption process respectively, implying an endothermic behavior. Therefore, we found that it can significantly remove naphthalene in aqueous environments and hence could be useful for cleaning up the environment from Poly Aromatic Hydrocarbon.

From Corn Starch to Nanostructured Magnetic Laser-Induced Graphene Nanocomposite

Laser-Induced Graphene (LIG) is a 3D, conductive, porous material with a high surface area, produced by laser irradiation of synthetic polymers with high thermal stability. Recently, the focus has shifted toward sustainable bioderived and biodegradable precursors, such as lignocellulosic materials. Despite starch being an abundant and cost-effective biopolymer, direct laser scribing on starch-derived precursors has not yet been explored. This study demonstrates that corn starch bioplastic (SP) can be converted into LIG through iron-catalyzed laser-induced pyrolysis, using Fe(NO₃)₃ as an additive. The impact of iron additive concentration on LIG formation and on its properties is investigated, with only certain concentrations yielding reliable and reproducible results. The investigation of LIG's crystal structure reveals magnetic and non-magnetic iron phases: γ-Fe₂O₃, Fe₃C, and Fe(C). The LIG nanocomposite exhibits soft magnetic properties, with a coercive field of Hc ≈ 200 Oe and a saturation magnetization of Ms ≈ 67 emu g⁻¹. The SP substrate degrades almost entirely in soil within 12 days and is unaffected by the addition of Fe(NO₃)₃, allowing for material compostability in line with circular economy principles. Consequently, SP stands out as a promising "green" precursor for magnetic LIG, paving the way for sustainable applications in environmental remediation.

Advances in magnetic analytical extraction techniques for detecting antibiotic residues in edible samples

The widespread use of antibiotics in agricultural and animal husbandry to treat bacterial illnesses has resulted in a rise in antibiotic-resistant bacteria. These bacteria can grow when antibiotic residues are present in food items, especially in edible animal products. As a result, it is crucial to monitor and regulate the amounts of antibiotics in food. Magnetic analytical extractions (MAEs) have emerged as a potential approach for extracting antibiotic residues from food using magnetic nanoparticles (MNPs). Recent improvements in MAEs have resulted in the emergence of novel MNPs with better selectivity and sensitivity for the extraction of antibiotic residues from food samples. Consequently, this review paper addresses current developments in MAE for extracting antibiotic residues from edible samples. It also provides a critical analysis of contemporary MAE practices. The current issues and potential future developments in this field are also discussed, thereby providing a framework for future study paths.

Fabrication of a novel graphene oxide based magnetic nanocomposite and its usage as a highly effectual catalyst for the construction of N,N'-alkylidene bisamides

At first, a novel graphene oxide-based magnetic nanocomposite namely Si-propyl-functionalized N 1,N 1,N 2,N 2-tetramethylethylenediamine-N 1,N 2-diium hydrogen sulfate anchored to graphene oxide-supported Fe3O4 (nano-[GO@Fe3O4@R-NHMe2][HSO4]) was fabricated. After full characterization of the nanocomposite, its catalytic performance was examined for the solvent-free construction of N,N'-alkylidene bisamides from aryl aldehydes (1 eq.) and primary aromatic and aliphatic amides (2 eq.), in which the products were acquired in short times (15-30 min) and high to excellent yields (89-98%). Nano-[GO@Fe3O4@R-NHMe2][HSO4] could be magnetically isolated form the reaction medium, and reused three times without remarkable loss of catalytic activity.

Effect of a solvothermal method using DMF on the dispersibility of rGO, application of rGO as a CDI electrode material, and recovery of sp2-hybridized carbon

Graphene is prized for its large surface area and superior electrical properties. Efforts to maximize the electrical conductivity of graphene commonly result in the recovery of sp2-hybridized carbon in the form of reduced graphene oxide (rGO). However, rGO shows poor dispersibility and aggregation when mixed with other materials without hydrophilic functional groups, This could lead to electrode delamination, agglomeration, and reduced efficiency. This study focuses on the impact of solvothermal reduction on the dispersibility and capacitance of rGO compared with chemical reduction. The results show that the dispersibility of rGO-D obtained through solvothermal reduction using N,N-dimethylformamide improved compared to that obtained through chemical reduction (rGO-H). Furthermore, when utilized as a material for CDI, an improvement in deionization efficiency was observed in the AC@rGO-D-based CDI system compared to AC@rGO-H and AC. However, the specific surface area, a key factor affecting CDI efficiency, was higher in rGO-H (249.572 m2 g-1) than in rGO-D (150.661 m2 g-1). While AC@rGO-H is expected to exhibit higher deionization efficiency due to its greater specific surface area, the opposite was observed. This highlights the effect of the improved dispersibility of rGO-D and underscores its potential as a valuable material for CDI applications.

Photoassisted Water Purification through an Electrochemically Artificially Adjusted p-Cu2O Light Absorption Layer

The implementation of photoelectrochemical water purification technology can address prevailing environmental challenges that impede the advancement and prosperity of human society. In this study, Cu, which is abundant on Earth, was fabricated using an electrochemical deposition process, in which the preferential orientation direction and carrier concentration of the Cu-based oxide semiconductor were artificially adjusted by carefully controlling the OH- and applied voltage. In particular, Cu2O grown with a sufficient supply of OH- ions exhibited the (111) preferred orientation, and the (200) surface facet was exposed, independently achieving 90% decomposition efficiency in a methyl orange (MO) solution for 100 min. This specialized method minimizes the recombination loss of electron-hole pairs by increasing the charge separation and transport efficiency of the bulk and surface of the Cu2O multifunctional absorption layer. These discoveries and comprehension not only offer valuable perspectives on mitigating self-photocorrosion in Cu2O absorbing layers but also provide a convenient and expeditious method for the mass production of water purification systems that harness unlimited solar energy. These properties enable significant energy saving and promote high-speed independent removal of organic pollutants (i.e., MO reduction) during the water purification process.

A simple graphene oxide-based DNA purification strategy for plant pathogen detection

BACKGROUND

The on-site molecular detection of plant pathogens is particularly important for the development of sustainable agriculture. Extracting DNA from plant tissues, microbes or coexisting environments is complex, labor-intensive and time-consuming. To facilitate this process, we propose a DNA purification strategy based on graphene oxide (GO).

RESULTS

The excellent adsorption ability of GO was verified by visualizing changes in its microscopic surface and macroscopic mixture. To further optimize the DNA purification, we determined the optimal GO concentration and treatment time at 95 °C (2 mg mL-1 and 2 min, respectively). We confirmed that our strategy is effective on plant tissues and various microorganisms, and that the obtained DNA can be directly used for polymerase chain reaction amplification. Combining the proposed GO-based DNA purification method with the loop-mediated isothermal amplification method is superior, in terms of the required steps, time, cost and detection effect, to the cetyltrimethylammonium bromide method and a commercial kit for detecting plant pathogens.

CONCLUSION

We present a feasible, rapid, simple and low-cost DNA purification method with high practical value for scientific applications in plant pathogen detection. This strategy can also provide important technical support for future research on plant-microbial microenvironments. © 2024 Society of Chemical Industry.

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.

Recent advances in the application of magnetic materials for the management of perfluoroalkyl substances in aqueous phases

Perfluoroalkyl substances (PFASs) are a class of artificially synthesised organic compounds extensively used in both industrial and consumer products owing to their unique characteristics. However, their persistence in the environment and potential risk to health have raised serious global concerns. Therefore, developing effective techniques to identify, eliminate, and degrade these pollutants in water are crucial. Owing to their high surface area, magnetic responsiveness, redox sensitivity, and ease of separation, magnetic materials have been considered for the treatment of PFASs from water in recent years. This review provides a comprehensive overview of the recent use of magnetic materials for the detection, removal, and degradation of PFASs in aqueous solutions. First, the use of magnetic materials for sensitive and precise detection of PFASs is addressed. Second, the adsorption of PFASs using magnetic materials is discussed. Several magnetic materials, including iron oxides, ferrites, and magnetic carbon composites, have been explored as efficient adsorbents for PFASs removal from water. Surface modification, functionalization, and composite fabrication have been employed to improve the adsorption effectiveness and selectivity of magnetic materials for PFASs. The final section of this review focuses on the advanced oxidation for PFASs using magnetic materials. This review suggests that magnetic materials have demonstrated considerable potential for use in various environmental remediation applications, as well as in the treatment of PFASs-contaminated water.

An efficient magnetic nanoadsorbent based on functionalized graphene oxide with gellan gum hydrogel embedded with MnFe layered double hydroxide for adsorption of Indigo carmine from water

The primary objective of this investigation was to synthesize a novel antibacterial nanocomposite consisting of natural gellan gum (GG) hydrogel, MnFe LDH, GO, and Fe3O4 nanoparticle, which was developed to adsorb Indigo carmine (IC). The GG hydrogel/MnFe LDH/GO/Fe3O4 nanocomposite was characterized through different analytical, microscopic, and biological methods. The results of adsorption experiments reveal that 0.004 g of the nanocomposite can remove 98.38 % of IC from a solution with an initial concentration of 100 mg/L, within 1 h at room temperature and under acidic pH conditions. Moreover, the nanocomposite material effectively suppressed the in vitro growth of both E. coli and S. aureus strains, with inhibitory rates of 62.33 % and 53.82 %, respectively. The isotherm data obtained in this investigation were fitted by linear and non-linear forms of Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms equations. The results of the adsorption kinetics study indicated that the pseudo-second-order model best described the experimental data. The findings of this study suggest that the synthesized nanocomposites hold great potential as effective adsorbents for removing IC and bacteria from aqueous solutions.

Graphene Oxide-Polyphenylsulfone Nanocomposite Beads for Paracetamol Removal from Aqueous Solution

This study introduces a promising and practical method for the removal of paracetamol from aqueous environments, employing graphene oxide-polymer nanocomposite beads. The approach involves the utilization of a straightforward and facile phase inversion method, offering a convenient and efficient one-step process for the creation of adsorbent beads by integrating polymers and graphene oxide (GO). The synthesized nanocomposite beads are tailored for the removal of paracetamol from simulated wastewater in batch systems. Extensive characterization techniques including XPS, FTIR, SEM, TGA, and zeta potential analysis are employed to scrutinize the chemical properties and structural attributes of the prepared beads. The investigation explores the impact of critical parameters such as adsorbent dosage, adsorption duration, initial paracetamol concentration, and solution pH on the adsorption process. These nanocomposite beads exhibit an exceptional paracetamol removal efficiency, achieving up to 99% removal. This research not only contributes to the advancement of efficient and sustainable adsorbent materials for pollutant removal but also underscores their potential for environmentally friendly and cost-effective solutions in the domain of wastewater treatment.

An influence of temperature jump and Navier's slip-on hybrid nano fluid flow over a permeable stretching/shrinking sheet with heat transfer and inclined MHD

This research article, explores the influence of an inclined magnetic field on the fluid flow over a permeable stretching/shrinking surface with heat transfer. The study use water as a conventional base fluid, with graphene oxide (GO) and Aluminum oxide (Al2O3) nanoparticles submerged to create a nanofluid, the system of governing nonlinear partial differential equations converted into ordinary differential equations via suitable similarity conversions. This allow for the unique solution for stretching sheet/shrinking sheets to be obtained, along with the corresponding temperature solution in terms of the hypergeometric function, several parameters are included in the investigation and their contribution is graphically explained to examine physical characteristics such as radiation, inclined magnetic field, solution domain, volume fraction parameter, and temperature jump. Increasing the volume fraction and thermal radiation increases the thermal boundary layer, increasing the magnetic field parameter and inverse Darcy number increases the temperature and decays the velocity profile. The present work has many useful applications in engineering, biological and physical sciences, as well as in cleaning engine lubricants and thrust-bearing technologies.

Green synthesis of Ag nanoparticle supported on graphene oxide for efficient nitrite sensing in a water sample

Water is essential for conserving biodiversity, ecology, and human health, but because of population growth and declining clean water supplies, wastewater must be treated to meet demand. Nitrite is one of the contaminants in wastewater that is well-known. It is crucial to identify nitrite since it can be fatal to humans in excessive doses. Utilizing a straightforward and effective electrochemical sensor, nitrite in actual water samples may be determined electrochemically. The sensor is created by coating the surface of a GC electrode with a thin layer of graphene oxide (GO), followed by a coating of silver nanoparticles. The modified electrode reached a linear detection range of 1-400 µM. thus, the activity of the electrode was investigated at different pH values ranging from 4 to 10 to cover acidic to highly basic environments. However, the electrode recorded limit of detection (LOD) is equal to 0.084, 0.090, and 0.055 µM for pH 4, 7, and 10, respectively. Additionally, the electrode activity was utilized in tap water and wastewater that the LOD reported as 0.16 and 0.157 µM for tape water and wastewater, respectively.

Photocatalytic behavior for removal of methylene blue from aqueous solutions via nanocomposites based on Gd2O3/CdS and cellulose acetate nanofibers

Efficient cleaning of contaminated water by photocatalysis has become an effective strategy in recent years due to its environmental and ecological designation. Cadmium sulfate (CdS) is an excellent photocatalyst in the visible region but has low quantum efficiency. In order to increase the photocatalytic efficiency, CdS was modified with gadolinium oxide (Gd2O3) and combined with graphene oxide (GO) nanoparticles. The estimated crystallite size (Ds) for Gd2O3, CdS/Gd2O3, and CdS/Gd2O3@GO was 29.6, 11.6, and 11.5 nm, respectively. The degradation of methylene blue (MB) reaches the highest values after 60 min under visible light irradiation with a dye concentration of (0.25 ppm). Whereas in powdered composition the efficiency of dye removal has been enhanced under UV irradiation, it reduced by increasing the MB concentration to 0.50 ppm with visible light irradiation. In addition, the CdS with/without Gd2O3 and GO were integrated into electrospun nanofibrous cellulose acetate (CA) through the electrospinning technique. The compounds of Gd2O3, CdS/Gd2O3, and CdS/Gd2O3/GO were encapsulated into CA nanofibers for the degradation of MB under visible and UV irradiation. The apparent rate constant (k) achieves a value of 0.006, 0.007, and 0.0013 min-1 while the removal efficiency reaches 41.02%, 54.71%, and 71.42% for Gd2O3@CA, CdS/Gd2O3@CA, and CdS/Gd2O3/GO@CA, respectively, after 60 min under UV irradiation.

Adsorption of chloroquine, propranolol, and metformin in aqueous solutions using magnetic graphene oxide nanocomposite

The work proposes the application of a nanocomposite formed by graphene oxide and magnetite to remove chloroquine, propranolol, and metformin from water. Tests related to adsorption kinetics, equilibrium isotherms and adsorbent reuse were studied, and optimization parameters related to the initial pH of the solution and the adsorbent dosage were defined. For all pharmaceuticals, adsorption tests indicated that removal efficiency was independent of initial pH at adsorbent dosages of 0.4 g L-1 for chloroquine, 1.2 g L-1 for propranolol, and 1.6 g L-1 for metformin. Adsorption equilibrium was reached within the first few minutes, and the pseudo-second-order model represented the experimental data well. While the equilibrium data fit the Sips isotherm model at 298 K, the predicted maximum adsorption capacities for chloroquine, propranolol, and metformin were 44.01, 16.82, and 12.23 mg g-1, respectively. The magnetic nanocomposite can be reused for three consecutive cycles of adsorption-desorption for all pharmaceuticals, being a promising alternative for the removal of different classes of pharmaceuticals in water.

Ultra-purification of heavy metals and robustness of calcium silicate hydrate (C-S-H) nanocomposites

For the sake of remediating the contamination of heavy metal ions (HMs) that poses high risk to the global environment, a novel inorganic nanocomposite with excellent robustness, calcium silicate hydrate (C-S-H), is synthesized at extremely low cost yet presents rapid adsorption rate and superhigh adsorption capacity. High concentrations of Cu(Ⅱ), Cd(Ⅱ), Co(Ⅱ) and Cr(Ⅲ) in wastewater can be purified to ultra-low level (∼0.008 mg L^-1) within 60 min at low C-S-H dosage, the concentration and pH indexes of which meet the standard for direct discharge in China. The adsorption processes are spontaneous, following the Langmuir adsorption isotherm model, and its kinetics conforms to pseudo-second order model. Meanwhile, C-S-H presents excellent anti-interference performance during the ultra-purification of HMs when exposed to the acid environments, solutions with various HMs as well as high salinity. The ultra-purification of HMs and robustness of C-S-H is realized through multiple mechanisms based on adsorption, involving hydrolysis of HMs, electrostatic interaction, chemical microprecipitation, surface complexation and interlayer complexation, among which interlayer complexation is dominant. All these verify the robust performance and broad applicability of C-S-H to complex aqueous systems.

Salt Transport in Crosslinked Hydrogel Membranes Containing Zwitterionic Sulfobetaine Methacrylate and Hydrophobic Phenyl Acrylate

Produced water is a by-product of industrial operations, such as hydraulic fracturing for increased oil recovery, that causes environmental issues since it includes different metal ions (e.g., Li+, K+, Ni2+, Mg2+, etc.) that need to be extracted or collected before disposal. To remove these substances using either selective transport behavior or absorption-swing processes employing membrane-bound ligands, membrane separation procedures are promising unit operations. This study investigates the transport of a series of salts in crosslinked polymer membranes synthesized using a hydrophobic monomer (phenyl acrylate, PA), a zwitterionic hydrophilic monomer (sulfobetaine methacrylate, SBMA), and a crosslinker (methylenebisacrylamide, MBAA). Membranes are characterized according to their thermomechanical properties, where an increased SBMA content leads to decreased water uptake due to structural differences within the films and to more ionic interactions between the ammonium and sulfonate moieties, resulting in a decreased water volume fraction, and Young’s modulus increases with increasing MBAA or PA content. Permeabilities, solubilities, and diffusivities of membranes to LiCl, NaCl, KCl, CaCl2, MgCl2, and NiCl2 are determined by diffusion cell experiments, sorption-desorption experiments, and the solution-diffusion relationship, respectively. Permeability to these metal ions generally decreases with an increasing SBMA content or MBAA content due to the corresponding decreasing water volume fraction, and the permeabilities are in the order of K+ > Na+ > Li+ > Ni2+ > Ca2+ > Mg2+ presumably due to the differences in the hydration diameter.

Adsorptive removal of aromatic diamines from water using metal-organic frameworks functionalized with a nitro group

Adsorptive removal of aromatic diamines such as methylenedianiline (MDA) and p-phenylenediamine (PPD) was firstly investigated with nitro-functionalized metal-organic frameworks (MOFs, MIL-101(Cr)-NO₂). The MIL-101(Cr)-NO₂ showed much better performances in the removal of MDA and PPD, in both adsorption capacity and kinetics, than any other adsorbents. For example, MIL-101(Cr)-NO₂ had a much higher maximum adsorption capacity for MDA (1111 mg·g^-1) than activated carbon (208 mg·g^-1) or a reported adsorbent (391 mg·g^-1). Based on experimental results, hydrogen bonding (especially, via the formation of a 6-membered ring (6-MR) between -NO₂ of the adsorbent and -NH₂ of the adsorbates) could be suggested as the main mechanism to interpret the noticeable adsorption of the diamines. Importantly, this is the first example to confirm that MOFs with nitro group can be a competitive adsorbent to remove organics composed of amino group, especially via making 6-MR through hydrogen bonding. Higher adsorption of MDA than that of PPD over MIL-101(Cr)-NO₂ might be explained with π-π interaction between aromatic rings (π-lean aromatics of MOF and π-rich aromatics of the adsorbates). Moreover, MIL-101(Cr)-NO₂ could be recycled after simple washing, suggesting the potential use of the MOF in adsorptive purification of contaminated water with organics with amino groups.

Stable and recyclable lanthanum hydroxide-doped graphene oxide biopolymer foam for superior aqueous arsenate removal: Insight mechanisms, batch, and column studies

In this study, a graphene oxide-based lanthanum hydroxide/chitosan foam (CSGOL foam) was synthesized for arsenate (As(V)) remediation in surface water. The synthesized CSGOL foam texture and purity was assessed using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) studies. The results proved that the foam was highly porous, stable, and had high surface functionality that facilitated adsorption for water pollutant removal. The sorption results proved that the As(V) removal was high (146.20 mg/g at pH 6 with 0.5 g/L CSGOL foam) when compared to the similar type of materials, endothermic chemisorption due to the production of monodentate and bidentate inner-sphere complexes. Furthermore, continuous column results indicated that the As(V) concentration in real surface waters was reduced to WHO standards (less than 10 μg As/L of water) of As(V) in drinking water for up to 10,000 bed volume. Further it can be used up to four cycles without loss of efficacy less than 93%. Because of its excellent removal capabilities and simple synthesis technique, CSGOL foam shows significant promise for treating As(V)-containing water. Further, the XPS analysis and batch studies results suggests that As(V) removal mechanism was involved electrostatic and surface complexation through chemical interaction predominately.

Self-Assembled Nanofibrous Membranes by Electrospinning as Efficient Dye Photocatalysts for Wastewater Treatment

Water pollution has become a leading problem due to industrial development and the resulting waste, which causes water contamination. Different materials and techniques have been developed to treat wastewater. Due to their self-assembly and photocatalytic behavior, membranes based on graphene oxide (GO) are ideal composite materials for wastewater treatment. We fabricated composite membranes from polylactic acid (PLA) and carboxylic methyl cellulose (CMC)/carboxyl-functionalized graphene oxide (GO-f-COOH) using the electrospinning technique and the thermal method. Then, a nanofibrous membrane (PLA/CMC/GO-f-COOH@Ag) was produced by loading with silver nanoparticles (Ag-NPs) to study its photocatalytic behavior. These membranes were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in order to investigate the behavior of the fabricated membranes. The degradation kinetics studies were conducted using mathematical models, such as the pseudo first- and second-order models, by calculating their regression coefficients (R²). These membranes exhibited exceptional dye degradation kinetics. The R² values for pseudo first order were PCGC = 0.983581, PCGC@Ag = 0.992917, and the R² values for pseudo second order were PCGC = 0.978329, PCGC@Ag = 0.989839 for methylene blue. The degradation kinetics of Rh-B showed R² values of PCGC = 0.973594, PCGC@Ag = 0.989832 for pseudo first order and R² values of PCGC = 0.994392, PCGC@Ag = 0.998738 for pseudo second order. The fabricated nanofibrous membranes exhibited a strong π-π electrostatic interaction, thus providing a large surface area, and demonstrated efficient photocatalytic behavior for treating organic dyes present in wastewater. The fabricated PLA/CMC/GO-f-COOH@Ag membrane presents exceptional photocatalytic properties for the catalytic degradation of methylene blue (MB) dye. Hence, the fabricated nanofibrous membrane would be an eco-friendly system for wastewater treatment under catalytic reaction.

Novel synthesis of multicomponent porous nano-hybrid composite, theoretical investigation using DFT and dye adsorption applications: disposing of waste with waste

Extensive studies have shown that doping can enhance the properties of graphene, but the application to real industrial wastewater treatment and theoretical calculations are limited. In this study, the hybrid nanoadsorbent Cu, N co-doped graphene (Cu@NG) was successfully synthesized via green route using carbon rods from waste dry batteries, human urine and copper nitrate, then multiple characterizations, detailed density functional theory (DFT) theoretical calculations and comprehensive actual wastewater tests are performed in environmental applications to investigate the adsorption properties and mechanism. The results showed that Cu@NG surface is mesoporous, decorated with CuO crystals and doped with N atoms. The isotherms and kinetics were simulated by Langmuir and pseudo-second-order models, respectively. The theoretical maximum sorption for MB and CV on Cu@NG is 116.28 mg·g^-1 and CV is 86.96 mg·g^-1, respectively. Pilot tests with Cu@NG on real textile wastewater showed that COD, BOD and color were removed by 54.2%, 55.2% and 86.4%, respectively. The desorption rate of Cu@NG is approximately above 90% for both MB and CV on Cu@NG after six cycles of treatment. The DFT calculations confirmed the experimental results as MB is more reactive than CV molecules. Besides, interactions have been systematically investigated via topology and natural bond orbital (NBO) analyses. The process mechanism involved mainly electrostatic adsorption, π-π stacking interactions and H-bonding interactions and ion exchange.

Insights into manganese ferrite anchored graphene oxide to remove Cd(II) and U(VI) via batch and semi-batch columns and its potential antibacterial applications

The bioaccumulation, non-biodegradability, and high toxicity of Cd(II) and U(VI) in water is a serious concerns. Manganese ferrite/graphene oxide (GMF) nanocomposites were synthesized, characterized, and used to efficiently remove Cd(II) and U(VI) from an aqueous solution in this study. X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) analyses, respectively, confirmed the formation of GMF and the adsorptive removal mechanism. The XRD results revealed an amorphous structure when MnFe₂O₄ was loaded onto the GO surface. XPS results suggest that C = C, C-OorOH, and metal oxides are responsible for the removal of Cd(II) and U(VI) via electrostatic and chemical interaction. According to the Brunauer Emmett and Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) characterization analysis, GMF has a high surface area (117.78 m²/g) and a spherical shape with even distribution. The kinetics data were successfully reproduced by a pseudo-second-order non-linear model indicating the complexity of the sorption mechanism was rate-limiting. The maximum Langmuir uptake ability of GMF for Cd(II) and U(VI) was calculated to be 232.56 mg/g and 201.65 mg/g, respectively. Using external magnetic power, the prepared GMF can easily separate from the aqueous solution and can keep both metal ions under Environmental protection agency standards in water for up to six cycles of re-use of GMF. Finally, the GMF nanocomposite demonstrated significant promise as an adsorbent for removing Cd(II) and U(VI) from actual contaminated water samples. The antibacterial test was expanded to include gram-negative E. coli and gram-positive S. aureus to better understand GMF's bacterial inhibition efficacy.

Unexpectedly efficient ion desorption of graphene-based materials

Ion desorption is extremely challenging for adsorbents with superior performance, and widely used conventional desorption methods involve high acid or base concentrations and large consumption of reagents. Here, we experimentally demonstrate the rapid and efficient desorption of ions on magnetite-graphene oxide (M-GO) by adding low amounts of Al³⁺. The corresponding concentration of Al³⁺ used is reduced by at least a factor 250 compared to conventional desorption method. The desorption rate reaches ~97.0% for the typical radioactive and bivalent ions Co²⁺, Mn²⁺, and Sr²⁺ within ~1 min. We achieve effective enrichment of radioactive ⁶⁰Co and reduce the volume of concentrated ⁶⁰Co solution by approximately 10 times compared to the initial solution. The M-GO can be recycled and reused easily without compromising its adsorption efficiency and magnetic performance, based on the unique hydration anionic species of Al³⁺ under alkaline conditions. Density functional theory calculations show that the interaction of graphene with Al³⁺ is stronger than with divalent ions, and that the adsorption probability of Al³⁺ is superior than that of Co²⁺, Mn²⁺, and Sr²⁺ ions. This suggests that the proposed method could be used to enrich a wider range of ions in the fields of energy, biology, environmental technology, and materials science.

Innovative progress in graphene derivative-based composite hybrid membranes for the removal of contaminants in wastewater: A review

Graphene derivatives (graphene oxide) are proved as an innovative carbon materials that are getting more attraction in membrane separation technology because of its unique properties and capability to attain layer-to-layer stacking, existence of high oxygen-based functional groups, and generation of nanochannels that successively enhance the selective pollutants removal performance. The review focused on the recent innovations in the development of graphene derivative-based composite hybrid membranes (GDHMs) for the removal of multiple contaminants from wastewater treatment. To design GDHMs, it was observed that at first GO layers undergo chemical treatments with either different polymers, plasma, or sulfonyl. After that, the chemically treated GO layers were decorated with various active functional materials (either with nanoparticles, magnetite, or nanorods, etc.). By preparing GDHMs, properties such as permeability, porosity, hydrophilicity, water flux, stability, feasibility, mechanical strength, regeneration ability, and antifouling tendency were excessively improved as compared to pristine GO membranes. Different types of novel GDHMs were able to remove toxic dyes (77-100%), heavy metals/ions (66-100%), phenols (40-100%), and pharmaceuticals (74-100%) from wastewater with high efficiency. Some of GDHMs were capable to show dual contaminant removal efficacy and antibacterial activity. In this study, it was observed that the most involved mechanisms for pollutants removal are size exclusion, transport, electrostatic interactions, adsorption, and donnan exclusion. In addition to this, interaction mechanism during membrane separation technology has also been elaborated by density functional theory. At last, in this review the discussion related to challenges, limitations, and future outlook for the applications of GDHMs has also been provided.

Greener synthesis of nanostructured iron oxide for medical and sustainable agro-environmental benefits

Nanoscale iron oxide-based nanostructures are among the most apparent metallic nanostructures, having great potential and attracting substantial interest due to their unique superparamagnetic properties. The green production of nanostructures has received abundant attention and been actively explored recently because of their various beneficial applications and properties across different fields. The biosynthesis of the nanostructure using green technology by the manipulation of a wide variety of plant materials has been the focus because it is biocompatible, non-toxic, and does not include any harmful substances. Biological methods using agro-wastes under green synthesis have been found to be simple, environmentally friendly, and cost-effective in generating iron oxide-based nanostructures instead of physical and chemical methods. Polysaccharides and biomolecules in agro-wastes could be utilized as stabilizers and reducing agents for the green production of nanostructured iron oxide towards a wide range of benefits. This review discusses the green production of iron oxide-based nanostructures through a simple and eco-friendly method and its potential applications in medical and sustainable agro-environments. This overview provides different ways to expand the usage of iron oxide nanomaterials in different sectors. Further, provided the options to select an appropriate plant towards the specific applications in agriculture and other sectors with the recommended future directions.

Visible-light-driven photocatalytic degradation of dye and antibiotics by activated biochar composited with K+ doped g-C3N4: Effects, mechanisms, actual wastewater treatment and disinfection

To improve the performance of graphitic carbon nitride (g-C₃N₄), a hotly researched metal-free photocatalyst, for better application in the efficient removal of organic pollutants, adsorption synergistically enhanced photocatalysis mechanism was thoroughly explored. Based on KOH pore-forming activated biochar (ACB) and K⁺ doped g-C₃N₄ (K-gC₃N₄), the novel activated biochar-based K-gC₃N₄ composite (ACB-K-gC₃N₄) was synthesized via the innovative ultrasonic-milling method. Rhodamine B (RhB), tetracycline (TC), norfloxacin (NOR), and chloramphenicol (CAP) were selected as target pollutants, and the effects of environmental factors, recycling and actual wastewater tests, disinfection effects, and various enhancement strategies were investigated. The results showed that K-gC₃N₄ was successfully composited with ACB by various characterizations, where the loading mass ratio of 1:2 exhibited the best performance. ACB-K-gC₃N₄ possessed a larger specific surface area, richer functional groups, suitable band gap (2.29 eV), and broader visible light absorption (~716 nm) than K-gC₃N₄. ACB-K-gC₃N₄ presented effective removal efficiency over K-gC₃N₄ for four pollutants, in which the removal efficiency of RhB reached 93.26%, and the degradation rate constant of 0.0119 min^-1 was four times higher than K-gC₃N₄ (0.0029 min^-1). Moreover, ACB-K-gC₃N₄ was superior to K-gC₃N₄ in disinfecting S. aureus and E. coli, with a sterilization rate of exceeding 90% for 12 h. The photodegradation activity was dominated by ·O₂^-, h⁺, and ·OH, and the mechanisms involved in the three stages. This was attributed to the unique structure and surface properties (defects and persistent free radicals) of ACB, as evidenced by improved adsorption stage and transfer of degradation intermediates, facilitated the generation of active species, accelerated migration of photogenerated electrons, and inhibited photogenerated carriers recombination by the heterojunction. The good reusability and stability, enhancement strategies (blowing air and heating), and satisfactory feasibility for actual wastewater allow ACB-K-gC₃N₄ possible to promote high-concentration wastewater treatment and disinfection.

Electrochemical Synthesis of Reduced Graphene Oxide/Gold Nanoparticles in a Single Step for Carbaryl Detection in Water

In this study, an in situ synthesis approach based on electrochemical reduction and ion exchange was employed to detect carbaryl species using a disposable, screen-printed carbon electrode fabricated with nanocomposite materials. Reduced graphene oxide (rGO) was used to create a larger electrode surface and more active sites. Gold nanoparticles (AuNPs,) were incorporated to accelerate electron transfer and enhance sensitivity. A cation exchange Nafion polymer was used to enable the adhesion of rGO and AuNPs to the electrode surface and speed up ion exchange. Cyclic voltammetry (CV), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), electrical impedance spectroscopy (EIS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were performed to study the electrochemical and physical properties of the modified sensor. In the presence of differential pulse voltammetry (DPV), an rGO/AuNP/Nafion-modified electrode was effectively used to measure the carbaryl concentration in river and tap water samples. The developed sensor exhibited superior electrochemical performance in terms of reproducibility, stability, efficiency and selectivity for carbaryl detection with a detection limit of 0.2 µM and a concentration range between 0.5µM and 250 µM. The proposed approach was compared to capillary electrophoresis with ultraviolet detection (CE-UV).

Magnesium ferrite-nitrogen-doped graphene oxide nanocomposite: effective adsorptive removal of lead(II) and arsenic(III)

Magnetic nanocomposites have received immense interest as adsorbents for water decontamination. This paper presents adsorptive properties of nitrogen-doped graphene oxide (N-GO) with magnesium ferrite (MgFe₂O₄) magnetic nanocomposite for removing lead(II) (Pb(II)and arsenite As(III) ions. Transmission electron microscope (TEM) image of synthesized nanocomposite revealed the wrinkled sheets of N-GO containing MgFe₂O₄ nanoparticles (NPs) with particle size of 5-15 nm distributed over its surface. This nanocomposite displayed higher BET surface area (72.2 m²g^-1) than that of pristine MgFe₂O₄ NPs (38.4 m²g^-1). Adsorption on the nanocomposite could be described by the Langmuir isotherm with the maximum adsorption capacities were 930 mg/g, and 64.1 mg/g for Pb(II) and As(III), respectively. Whereas, maximum removal efficiencies were observed to be 99.7 [Formula: see text] 0.2% and 93.5 [Formula: see text] 0.1% for Pb(II) and As(III), respectively. The study on the effect of coexisting anions on the adsorption of metal ions showed that the phosphate ions were potential competitors of Pb(II) and As(III) ions to adsorb on the nanocomposite. Significantly, the investigation on adsorption of metal ion in the presence of coexisting heavy metal ions indicated the preferential adsorption of Pb(II) ions as compared to Cd(II), Zn(II) and Ni(II) ions. The effectiveness of the nanocomposite to remove the metal ions in electroplating wastewater was demonstrated.

Highly efficient surface sequestration of Pb2+ and Cr3+ from water using a Mn3O4 anchored reduced graphene oxide: Selective removal of Pb2+ from real water

Owing to the ubiquitous existence of detrimental heavy metals in the environment, simple adsorption-oriented approaches are becoming increasingly appealing for the effective removal of Pb²⁺ and Cr³⁺ from water bodies. These techniques use nanocomposites (NC) of reduced graphene oxide (rGO) and Mn₃O₄ (rGO-Mn₃O₄), they employ a hydrothermal technique featuring NaBH₄ and NaOH solutions. Here, spectroscopic and microscopic instrumental techniques were used to evaluate the morphological and physicochemical characteristics of prepared reduced graphene oxide manganese oxide (rGO-Mn₃O₄), revealing that it possessed a well-defined porous structure with a specific surface area of 126 m² g^-1. The prepared rGO-Mn₃O₄ had significant adsorption efficiencies for Pb²⁺ and Cr³⁺, achieving maximum sequestration capacities of 130.28 and 138.51 mg g^-1 for Pb²⁺ and Cr³⁺, respectively, according to the Langmuir model. These adsorption capacities are comparable to or greater than those of previously reported graphene-based materials. The Langmuir isotherm and pseudo-second-order models adequately represented the experimental results. Thermodynamic analysis revealed that adsorption occurred through spontaneous endothermic reactions. Recycling studies showed that the developed r-GO-Mn₃O₄ had excellent recyclability, with <70% removal at the 5th cycle; its feasibility was evaluated using industrial wastewater, suggesting that Pb²⁺ was selectively removed from Pb²⁺ and Cr³⁺ contaminated water. The instrumental analysis and surface phenomena studies presented here revealed that the adsorptive removal processes of both heavy metals involved π electron donor-acceptor interactions, ion exchange, and electrostatic interactions, along with surface complexation. Overall, the developed rGO-Mn₃O₄ has the potential to be a high-value adsorbent for removing heavy metals.

Lead ferrite-activated carbon magnetic composite for efficient removal of phenol from aqueous solutions: synthesis, characterization, and adsorption studies

A novel lead ferrite-magnetic activated carbon (lead ferrite-MAC) composite was developed using the chemical co-precipitation method. Instrumental analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis were performed to characterize adsorbent. The uptake of phenol from aqueous solutions using the developed adsorbent was compared to that of pristine activated carbon. The maximum adsorption capacity of lead ferrite-MAC composite (145.708 mg/g) was more than that of pristine activated carbon (116.606 mg/g) due to the metal hydroxides coated on activated carbon since they improve the retention of phenol on the available active sites of adsorbent and create an additional electrostatic interaction with the phenol adsorbate. Regarding the high value of the coefficient of determination (R2) and adjusted determination coefficient (R2adj), coupled with the lower values of average relative error (ARE) and minimum squared error (MSE), it can be found that the isothermal data for the lead ferrite-MAC adsorbent were in agreement with the isotherm models of Redlich-Peterson and Langmuir. From the kinetic viewpoint, pseudo-second-order and linear driving force models explained the phenol adsorption data for both adsorbents. The reusability tests for lead ferrite-MAC composite revealed that after six cycles, 85% of the initial adsorption capacity was maintained. The developed adsorbent can be successfully applied to uptake phenol from aqueous solutions.

Adsorptive removal of organic dyes via porous materials for wastewater treatment in recent decades: A review on species, mechanisms and perspectives

Organic dyes, a type of high toxic and carcinogenic chemicals that present severe threats to human and aquatic life, are the most commonly seen organic pollutants in wastewater of industries such as textile, rubber, cosmetic industry etc. Various techniques for the removal of dyes are compared in this review. Adsorption has proven to be a facile and promising approach for the removal of dyes in wastewater. This work focuses on the latest development of various porous materials for the adsorption of organic dyes. The characteristics, functionalization and modification of different porous materials are also presented. Furthermore, adsorption behaviors and mechanism of these adsorbents in the adsorption of organic dyes are critically reviewed. Finally, challenges and opportunities for future research in the development of novel materials for the highly efficient removal of dyes are proposed.

Predictive capability evaluation and optimization of Pb(II) removal by reduced graphene oxide-based inverse spinel nickel ferrite nanocomposite

Pb(II) is a heavy metal that is a prominent contaminant in water contamination. Among the different pollution removal strategies, adsorption was determined to be the most effective. The adsorbent and its type determine the adsorption process's efficiency. As part of this effort, a magnetic reduced graphene oxide-based inverse spinel nickel ferrite (rGNF) nanocomposite for Pb(II) removal is synthesized, and the optimal values of the independent process variables (like initial concentration, pH, residence time, temperature, and adsorbent dosage) to achieve maximum removal efficiency are investigated using conventional response surface methodology (RSM) and artificial neural networks (ANN). The results indicate that the initial concentration, adsorbent dose, residence time, pH, and process temperature are set to 15 mg/L, 0.55 g/L, 100 min, 5, and 30 °C, respectively, the maximum removal efficiency (99.8%) can be obtained. Using the interactive effects of process variables findings, the adsorption surface mechanism was examined in relation to process factors. A data-driven quadratic equation is derived based on the ANOVA, and its predictions are compared with ANN predictions to evaluate the predictive capabilities of both approaches. The R² values of RSM and ANN predictions are 0.979 and 0.991 respectively and confirm the superiority of the ANN approach.

Synthesis and application of graphene oxide as a nanoadsorbent to remove Cd (II) and Pb (II) from water: adsorption equilibrium, kinetics, and regeneration

In this work, graphene oxide (GO) was synthesized by the modified Hummers method. The nanomaterial was characterized by FTIR and Raman spectroscopy, SEM, and pH at the point of zero charge. GO exhibited typical characteristics of graphene-based materials, indicating that graphite oxidation and exfoliation occurred successfully. Cd (II) and Pb (II) adsorption onto GO was carried out in batch systems, in which the effect of adsorbent dosage, contact time, and initial adsorbate concentration were evaluated. Langmuir, Freundlich, and Sips isotherm models, as well as pseudo order models and Elovich kinetic equation were applied to adsorption experimental data. Results indicated that increasing adsorbent mass, the removal efficiency of Cd (II) and Pb (II) increased. Freundlich isotherm better described Pb (II) adsorption (R² = 0.96), while Cd (II) isotherm showed linear behavior. From the Akaike's AIC parameter, kinetic data were satisfactorily described by pseudo-first order (Cd (II)) and pseudo-n order (Pb (II)) models. GO was successfully subjected to five regeneration cycles, maintaining high efficiency (> 90%) in all cycles. GO showed high potential for the adsorption of Cd (II) and Pb (II) from aqueous solution, due to its high adsorption capacity, rapid Cd (II) and Pb (II) intakes, and great regeneration performance.

The application of GO-Fe3O4 nanocomposite for chromium adsorption from tannery industry wastewater

The discharge of untreated tannery industrial wastewater into the environment has resulted in an adverse effect on the ecosystem and public health. Therefore, this work aimed to remove chromium ions from tannery wastewater through magnetite graphene oxide-nanocomposite (GO-Fe₃O₄). The experimental design of the study was a full factorial 2⁴ approach using pH, adsorbent dose, contact time, and initial chromium concentrations. The results of FTIR analysis revealed the presence of functional groups such as hydroxyl (3438 cm^-1), alcohol (1230 cm^-1), aromatic (1467 cm^-1), ketone (1629 cm^-1), and ether (1120 cm^-1). Similarly, GO-Fe₃O₄ acquired a high surface area of 296.2 m²/g whereas the XRD analysis showed the presence of predominant peaks which are attributed to the magnetite component. Moreover, the SEM image showed many ups and downs on the surface of the adsorbent. These cracks of morphology can create a conducive environment for the interaction of adsorbent and adsorbate. The maximum chromium removal of 95.9% was achieved at the optimum conditions of the initial chromium concentration of 40 mg/L, pH 4, adsorbent dose 1 g/100 mL, and contact time of 120 min whereas the removal of chromium from real tannery wastewater was found to be 90.3%. Based on the adsorption isotherm, the Langmuir model was the best fit for experimental data at R² 0.99, indicating homogeneous and monolayer adsorption. Finally, it can be concluded that GO-Fe₃O₄ was effective for chromium removal, which is a promising technology to be scaled up at the industrial level for wastewater treatment.

Graphene Oxide/Fe3O4/Chitosan−Coated Nonwoven Polyester Fabric Extracted from Disposable Face Mask for Enhanced Efficiency of Organic Dye Adsorption

Owing to the COVID-19 pandemic, huge amounts of disposable face masks have been manufactured and used, and these discarded face masks have to be treated. In this study, we propose a simple approach for reusing the nonwoven polyester fabric (NWPF) from disposable face masks. In this approach, NWPF is utilized as a supporter for coating of a layer of graphene oxide/Fe3O4/chitosan (GFC) to form a GFC/NWPF adsorbent at room temperature via a simple spray coating method that does not require any solvent. The specific properties of GFC, NWPF, and the GFC/NWPF adsorbent were analysed via X-ray diffraction, transmission electron microscopy, ultraviolet–visible spectroscopy, vibrating sample magnetometry, and field-emission scanning electron microscopy. Results showed that the presence of NWPF enhanced the adsorption capacity of GFC towards organic dyes. At high concentrations of the organic dyes, the adsorption efficiency of the GFC/NWPF adsorbent to the dyes reached 100% within 24 h. The adsorption capacity ( $q_{\max }$ ) of the GFC/NWPF adsorbent to methylene blue, methyl orange, Congo red, and moderacid red was 54.795, 87.489, 88.573, and 29.010 mg g−1, respectively, which were considerably higher than that of bulk GFC (39.308, 82.304, 52.910, and 21.249 mg g−1, respectively).

Development of artificial neural networks software for arsenic adsorption from an aqueous environment

Arsenic contamination is a global problem, as it affects the health of millions of people. For this study, data-driven artificial neural network (ANN) software was developed to predict and validate the removal of As(V) from an aqueous solution using graphene oxide (GO) under various experimental conditions. A reliable model for wastewater treatment is essential in order to predict its overall performance and to provide an idea of how to control its operation. This model considered the adsorption process parameters (initial concentration, adsorbent dosage, pH, and residence time) as the input variables and arsenic removal as the only output. The ANN model predicted the adsorption efficiency with high accuracy for both training and testing datasets, when compared with the available response surface methodology (RSM) model. Based on the best model synaptic weights, user-friendly ANN software was created to predict and analyze arsenic removal as a function of adsorption process parameters. We developed various graphical user interfaces (GUI) for easy use of the developed model. Thus, a researcher can efficiently operate the software without an understanding of programming or artificial neural networks. Sensitivity analysis and quantitative estimation were carried out to study the function of adsorption process parameter variables on As(V) removal efficiency, using the GUI of the model. The model prediction shows that the adsorbent dosages, initial concentration, and pH are the most influential parameters. The efficiency was increased as the adsorbent dosages increased, decreasing with initial concentration and pH. The result show that the pH 2.0-5.0 is optimal for adsorbent efficiency (%).