Recent advances in magnetic composites as adsorbents for wastewater remediation

Magnetic Biochar as a Revolutionizing Approach for Diverse Dye Pollutants Elimination: A Comprehensive Review

The term "biomass" encompasses all substances found in the natural world that were once alive or derived from living organisms or their byproducts. These substances consist of organic molecules containing hydrogen, typically oxygen, frequently nitrogen, and small amounts of heavy, alkaline earth and alkali metals. Magnetic biochar refers to a type of material derived from biomass that has been magnetized typically by adding magnetic components such as magnetic iron oxides to display magnetic properties. These materials are extensively applicable in widespread areas like environmental remediation and catalysis. The magnetic properties of these compounds made them ideal for practical applications through their easy separation from a reaction mixture or environmental sample by applying a magnetic field. With the evolving global strategy focused on protecting the planet and moving towards a circular, cost-effective economy, natural compounds, and biomass have become particularly important in the field of biochemistry. The current research explores a comparative analysis of the versatility and potential of biomass for eliminating dyes as a sustainable, economical, easy, compatible, and biodegradable method. The elimination study focused on the removal of various dyes as pollutants. Various operational parameters which influenced the dye removal process were also discussed. Furthermore, the research explained, in detail, adsorption kinetic models, types of isotherms, and desorption properties of magnetic biochar adsorbents. This comprehensive review offers an advanced framework for the effective use of magnetic biochar, removing dyes from textile wastewater.

Rapidly reducing cadmium from contaminated farmland soil by novel magnetic recyclable Fe3O4/mercapto-functionalized attapulgite beads

Reducing cadmium (Cd) content from contaminated farmland soils remains a major challenge due to the difficulty in separating commonly used adsorbents from soils. This study synthesized novel millimeter-sized magnetic Fe3O4/mercapto-functionalized attapulgite beads (MFBs) through a facile one-step gelation process incorporating alginate. The MFBs inherit the environmental stability of alginate and enhance its mechanical strength by hybridizing Fe3O4 and clay mineral components. MFBs can be easily separated from flooded soils by magnets. When applied to 12 Cd-polluted paddy soils and 14 Cd-polluted upland soils, MFBs achieved Cd(II) removal rates ranging from 16.9% to 62.2% and 9.8%-54.6%, respectively, within a 12-h period. The MFBs predominantly targeted the exchangeable and acid soluble, and reducible fractions of Cd, with significantly enhanced removal efficiencies in paddy soils compared to upland soils. Notably, MFBs exhibited superior adsorption performance in soils with lower pH and organic matter (OM) content, where the bioavailability and mobility of Cd are heightened. The reduction of Cd content by MFBs is a sustainable and safe method, as it permanently removes the bioavailable Cd from soil, rather than temporarily reducing its bioavailability. The functional groups such as -SH, -OH, present in attapulgite and alginate of MFBs, played a crucial role in Cd(II) adsorption. Additionally, attapulgite and zeolite provided a porous matrix structure that further enhanced Cd(II) adsorption. The results of X-ray photoelectron spectroscopy suggested that both chemical precipitation and surface complexation contributed to Cd(II) removal. The MFBs maintained 87.6% Cd removal efficiency after 5 regeneration cycles. The surface of the MFBs exposed new adsorption sites and increased the specific surface area during multiple cycles with Cd-contaminated soil. This suggests that MFBs treatment with magnetic retrieval is a potentially effective pathway for the rapid removal of Cd from contaminated farmland soils.

Efficient Selective Adsorption of Rubidium and Cesium from Practical Brine Using a Metal-Organic Framework-Based Magnetic Adsorbent

Rubidium (Rb) and cesium (Cs) have important applications in highly technical fields. Salt lakes contain huge reserves of Rb and Cs with industrial significance, which can be utilized after extraction. In this study, a composite magnetic adsorbent (Fe3O4@ZIF-8@AMP, AMP = ammonium phosphomolybdate) was prepared and its adsorption properties for Rb+ and Cs+ were studied in simulated and practical brine. The structure of the adsorbent was characterized by SEM, XRD, N2 adsorption-desorption, FT-IR, and vibrating sample magnetometer (VSM). The adsorbent had good adsorption affinity for Rb+ and Cs+. The Langmuir model and pseudo-second-order dynamics described the adsorbing isotherm and kinetic dates, respectively. The adsorption capacity and adsorption rate of Fe3O4@ZIF-8@AMP were increased by 1.86- and 2.5-fold compared with those of powdered crystal AMP, owing to the large specific surface area and high dispersibility of the adsorbent in the solution. The adsorbent was rapidly separated from the solution within 17 s using an applied magnetic field owing to the good magnetic properties. The composite adsorbent selectively adsorbed Rb+ and Cs+ from the practical brine even in the presence of a large number of coexisting ions. The promising adsorbent can be used to extract Rb+ and Cs+ from aqueous solutions.

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.

An Updated Overview of Silica Aerogel-Based Nanomaterials

Silica aerogels have gained much interest due to their unique properties, such as being the lightest solid material, having small pore sizes, high porosity, and ultralow thermal conductivity. Also, the advancements in synthesis methods have enabled the creation of silica aerogel-based composites in combination with different materials, for example, polymers, metals, and carbon-based structures. These new silica-based materials combine the properties of silica with the other materials to create a new and reinforced architecture with significantly valuable uses in different fields. Therefore, the importance of silica aerogels has been emphasized by presenting their properties, synthesis process, composites, and numerous applications, offering an updated background for further research in this interdisciplinary domain.

Recent progress in magnetic polydopamine composites for pollutant removal in wastewater treatment

Various water pollution issues pose a significant threat to human water safety. Magnetic polydopamine composites (MPCs), which can be separated by magnetic fields after the adsorption process, exhibit outstanding adsorption capacity and heterogeneous catalytic properties, making them promising materials for water treatment applications. In particular, by modifying the polydopamine (PDA) coating, MPCs can acquire enhanced high reactivity, antibacterial properties, and biocompatibility. This also provides an attractive platform for further fabrication of hybrid materials with specific adsorption, catalytic, antibacterial, and water-oil separation capabilities. To systematically provide the background knowledge and recent research advances in MPCs, this paper presents a critical review of MPCs for water treatment in terms of both structure and mechanisms of effect in applications. Firstly, the impact of different PDA positions within the composite structure is investigated to summarize the optimization of properties contributed by PDA when acting as the shell, core, or bridge. The roles of various secondary modifications of magnetic materials by PDA in addressing water pollution problems are explored. It is anticipated that this work will be a stimulus for further research and development of magnetic composite materials with real-world application potential.

Recent advances in metal organic frameworks-based magnetic nanomaterials for waste water treatment

Magnetic nanoparticle-incorporated metal organic frameworks (MOF) are potential composites for various applications such as catalysis, water treatment, drug delivery, gas storage, chemical sensing, and heavy metal ion removal. MOFs exhibits high porosity and flexibility enabling guest species like heavy metal ions to diffuse into bulk structure. Additionally, shape and size of the pores contribute to selectivity of the guest materials. Incorporation of magnetic materials allows easy collection of adsorbent materials from solution system making the process simple and cost-effective. In view of the above advantages in the present review article, we are discussing recent advances of different magnetic material-incorporated MOF (Mg-MOF) composite for application in photocatalytic degradation of dyes and toxic chemicals, adsorption of organic compounds, adsorption of heavy metal ions, and adsorption of dyes. The review initially discusses on properties of Mg-MOF, different synthesis techniques such as mechanochemical, sonochemical (ultrasound) synthesis, slow evaporation and diffusion methods, solvo(hydro)-thermal and iono-thermal method, microwave-assisted method, microemulsion method post-synthetic modification template strategies and followed by application in waste water treatment.

Facile synthesis of ZnO/Hal nanocomposite for arsenite (As(III)) removal from aqueous media

Arsenite (As(III)) is the most toxic form of arsenic that is a serious concern for water contamination worldwide. Herein a ZnO/Halloysite (Hal) nanocomposite was prepared by the chemical bath deposition method (CBD) through seed-mediated ZnO growth on the halloysite for eliminating As(III) from the aqueous solution. The growth of ZnO on seeded halloysite was investigated based on the HMTA: Zn2+ molar ratio in the solution. An optimum molar ratio of HMTA:Zn for nucleation and growth of ZnO upon halloysite was obtained 1:2 based on morphological analysis. The TGA results confirmed that thermal stability of HNT was enhanced by ZnO decoration. The prepared ZnO/Hal nanocomposite at optimal conditions was employed for arsenite (As(III)) removal from aqueous solutions. Experimental data were evaluated with different isothermal, thermodynamic, and kinetic models. Based on the zeta potential results, Hal nanocomposites had a greater negative value than pure Hal. Therefore, the ZnO/Hal nanocomposite exhibited efficient As(III) adsorption with a removal efficiency of 76% compared to pure Hal with a removal efficiency of 5%. Adsorption isotherm was well correlated by both non-linear Langmuir and Sips models, exhibiting maximum adsorption capacity of As(III) at 42.07 mg/g, and 42.5 mg/g, respectively. As a result of the study, it was found that the fabricated Hal nanocomposite with low toxicity can be used effectively in water treatment.

A review on the lignocellulosic derived biochar-based catalyst in wastewater remediation: Advanced treatment technologies and machine learning tools

Wastewater disposal in the ecosystem affects aquatic and human life, which necessitates the removal of the contaminants. Eliminating wastewater contaminants using biochar produced through the thermal decomposition of lignocellulosic biomass (LCB) is sustainable. Due to its high specific surface area, porous structure, oxygen functional groups, and low cost, biochar has emerged as an alternate contender in catalysis. Various innovative advanced technologies were combined with biochar for effective wastewater treatment. This review examines the use of LCB for the synthesis of biochar along with its activation methods. It also elaborates on using advanced biochar-based technologies in wastewater treatment and the mechanism for forming oxidizing species. The research also highlights the use of machine learning in pollutant removal and identifies the obstacles of biochar-based catalysts in both real-time and cutting-edge technologies. Probable and restrictions for further exploration are discussed.

Tuning the surface functionality of polyethylene glycol-modified graphene oxide/chitosan composite for efficient removal of dye

There has been a lot of attention on water pollution by dyes in recent years because of their serious toxicological implications on human health and the environment. Therefore, the current study presented a novel polyethylene glycol-functionalized graphene oxide/chitosan composite (PEG-GO/CS) to remove dyes from aqueous solutions. Several characterization techniques, such as SEM, TEM, FTIR, TGA/DTG, XRD, and XPS, were employed to correlate the structure-property relationship between the adsorption performance and PEG-GO/CS composites. Taguchi's (L25) approach was used to optimize the batch adsorption process variables [pH, contact time, adsorbent dose, and initial concentration of methyl orange (MO)] for maximal adsorption capacity. pH = 2, contact time = 90 min, adsorbent dose = 10 mg/10 mL, and MO initial concentration = 200 mg/L were found to be optimal. The material has a maximum adsorption capacity of 271 mg/g for MO at room temperature. With the greatest R2 = 0.8930 values, the Langmuir isotherm model was shown to be the most appropriate. Compared to the pseudo-first-order model (R2 = 0.9685), the pseudo-second-order model (R2 = 0.9707) better fits the kinetic data. Electrostatic interactions were the dominant mechanism underlying MO sorption onto the PEG/GO-CS composite. The as-synthesized composite was reusable for up to three adsorption cycles. Thus, the PEG/GO-CS composite fabricated through a simple procedure may remove MO and other similar organic dyes in real contaminated water.

Adsorption of anionic dye from aqueous environment using surface-engineered Zn/Cu hydroxy double salt-based material: mechanistic, equilibrium and kinetic studies

Herein, ethylene glycol (EG)-modified Zn/Cu hydroxy double salts (HDS) were synthesized using a facile synthetic approach. The formation of layered structure and presence of EG in the interlayer region were confirmed using PXRD and FTIR techniques. Furthermore, XPS analysis was used to confirm presence of metal ions in synthesized HDS. The surface area and pore size diameter of the HDS was found to be 32.30 m2 g-1 and 2.22 nm, respectively, using BET. The role of HDS was evaluated for its potential application as a sorbent for Congo red (CR) dye uptake. Batch studies were conducted to examine the impact of key variables, i.e., pH, time, adsorbent dosage and dye concentration on adsorption efficiency of HDS. Linear-nonlinear isotherm and kinetic models were employed for detailed analysis of experimental data. Langmuir, Freundlich and Temkin isotherm models were subsequently utilized to fit equilibrium data, among which Langmuir demonstrated to be most accurate. The maximum monolayer adsorption capacity estimated using Langmuir model was computed to be 181.81 mg g-1. The kinetic data follows pseudo-second-order model having good R2 value (0.999). Additionally, thermodynamic study suggested spontaneous and endothermic nature of adsorption process having reusability up to 5 cycles with removal efficiency more than 85%.

Characterisation of kapok fibre's biochar for arsenate adsorption removal from aqueous solution

Al-KBC was produced through the simple pyrolysis of Al-modified kapok fibres at high temperatures. Using the N₂ adsorption Brunauer Emmett Teller (BET) process, Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), the energy-dispersive X-ray spectroscopy (EDS) spectroscopy, and X-ray photoelectron spectroscopy (XPS), the sorbent changes and characteristics were analysed. As a result of Al's addition to the fibre's surface, Al-KBC exhibited superior As(V) adsorption performance compared to KBC due to better pore structures. Experiments on the kinetics of As(V) adsorption revealed that the adsorption followed the pseudo-second-order model and that intradiffusion was not the only factor governing the adsorption. Experiments with isotherms indicated that the adsorption mechanism corresponded to the Langmuir model, and the adsorption capacity Q_m of Al-KBC at 25 °C was 483 μg/g. The thermodynamic experiments suggested that the adsorption reactions were spontaneous endothermic with a random approach at the adsorption interface. 25 mg/L of coexisting ions such as sulphate and phosphate reduced the sorbent As(V) removal ability to 65% and 39%. After seven cycles of adsorption/desorption, Al-KBC demonstrated satisfactory performance in terms of reusability, adsorbing 53% of 100 μg/L As(V) from the water. This novel BC can probably be used as a filter to purify groundwater with high As(V) concentration in the rural zone.

Effective aqueous chromate treatment using triethanolamine anacardate coated magnetic nanoparticles

Low-cost adsorbents derived from agricultural by-products incorporated magnetic nanoparticles (NPs) are promising for wastewater treatment. They are always preferred due to their great performance and easy separation. This study reports cobalt superparamagnetic (CoFe₂O₄) nanoparticles (NPs) incorporated with triethanolamine (TEA) based surfactants from cashew nut shell liquid, namely TEA-CoFe₂O₄, for the removal of chromium (VI) ions from aqueous solutions. To have detailed characteristics of the morphology and structural properties, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometry (VSM) were employed. The fabricated TEA-CoFe₂O₄ particles exhibit soft and superparamagnetic properties, which make the nanoparticles easily recycled by using a magnet. Chromate adsorption on the TEA-CoFe₂O₄ nanomaterials reached an optimal efficiency of 84.3% at pH = 3 with the initial adsorbent dose of 10 g/L and chromium (VI) concentration of 40 mg/L. The TEA-CoFe₂O₄ nanoparticles can maintain the effective adsorption of chromium (VI) ion (by 29% of efficiency loss) and retain the magnetic separation using a magnet up to three cycles of the regeneration, which promise a high potential of this low-cost adsorbent for long-term treatment of heavy metal ions from polluted waters.

Adsorption of methylene blue dye from aqueous solution using low-cost adsorbent: kinetic, isotherm adsorption, and thermodynamic studies

Fig leaf, an environmentally friendly byproduct of fruit plants, has been used for the first time to treat of methylene blue dye. The fig leaf-activated carbon (FLAC-3) was prepared successfully and used for the adsorption of methylene blue dye (MB). The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the Brunauer-Emmett-Teller (BET). In the present study, initial concentrations, contact time, temperatures, pH solution, FLAC-3 dose, volume solution, and activation agent were investigated. However, the initial concentration of MB was investigated at different concentrations of 20, 40, 80, 120, and 200 mg/L. pH solution was examined at these values: pH3, pH7, pH8, and pH11. Moreover, adsorption temperatures of 20, 30, 40, and 50 °C were considered to investigate how the FLAC-3 works on MB dye removal. The adsorption capacity of FLAC-3 was determined to be 24.75 mg/g for 0.08 g and 41 mg/g for 0.02 g. The adsorption process has followed the Langmuir isotherm model (R² = 0.9841), where the adsorption created a monolayer covering the surface of the adsorbent. Additionally, it was discovered that the maximum adsorption capacity (Qm) was 41.7 mg/g and the Langmuir affinity constant (KL) was 0.37 L/mg. The FLAC-3, as low-cost adsorbents for methylene blue dye, has shown good cationic dye adsorption performance.

Green synthesis of highly efficient and stable copper oxide nanoparticles using an aqueous seed extract of Moringa stenopetala for sunlight-assisted catalytic degradation of Congo red and alizarin red s

Environmental pollution by organic pollutants because of population growth and industrial expansion is a global concern. Following this, the fabrication of single and efficient nanomaterials for pollution control is highly demanded. Under this study, highly efficient and stable copper oxide nanoparticles (CuO NPs) were synthesized through the green method using Moringa stenopetala seed extract. XRD, UV-vis, FT-IR, and SEM were applied to characterize the synthesized material. From XRD data, the average particle size was found to be 6.556 nm, and the nanoparticles are crystalline in nature. The formation of CuO NPs was demonstrated by FT-IR spectra of Cu-O in different bending vibration bands at 535 cm-1 and 1122 cm-1, as well as stretching vibration of Cu-O at 1640 cm-1. From UV-visible spectroscopic measurements, the energy band gap of greenly synthesized CuO NPs was found to be 1.73 eV. The SEM result shows that the nanoparticles' surfaces are rough, with some of the particles having spherically random orientation. The photodegradation efficiency of green synthesized CuO NPs photocatalyst was found to be 98.35% for Congo red at optimum experimental parameters (initial concentration, 25 mg/L; exposure time, 120 min; catalyst dose, 0.2 g; and pH, 5) and 95.4% for Alizarin Red S at optimum experimental parameters (catalyst dose, 0.25 g; initial concentration, 40 mg/L; exposure time, 120 min; and pH, 4.6). The COD values determined for the degraded product strongly support the complete mineralization of the dyes toward nontoxic materials. Reusability of the catalyst was investigated for five cycles, and the results clearly indicate the green synthesized CuO NPs are highly stable, can be used for several times, and are cost-effective as well. The degradation of Congo red and Alizarin red S on the surface of the CuO NPs follows the MBG kinetic model.

Design and development of novel magnetic Lentinan/PVA nanocomposite for removal of diazinon, malathion, and diclofenac contaminants

Increasing population growth and rapid expansion of the industrialization of the world society have caused severe environmental pollution to the planet. This study was carried out in order to investigate the synthesis of biopolymeric texture nano adsorbent based on the Lentinan (LENT), Poly Vinyl Alcohol (PVA) and Iron Oxide nanoparticles for the removal of environmental pollutants. The spherical structural morphology of Fe₃O₄@LENT/PVA nanocomposite has been determined by FE-SEM analyses. According to the obtained results from FTIR analyses, all absorption bands of the Fe₃O₄, LENT, and PVA, had been existed in nanocomposite and approved the successful formation of it. From EDS analysis, it has been revealed that 57.21 wt% Fe, 17.56 wt% C and 25.23 wt% O. Also, the XRD pattern of the nanocomposite, approved the presence of polymeric and magnetic parts with card no. JCPDS, 01-075-0033. The BET analysis has defined specific surface area (47 m²/g) and total pore volume (0.15 cm³/g). Moreover, high heterogeneity and structural stability of the fabricated Fe₃O₄@LENT/PVA nanocomposite have been proven by TGA. Besides, VSM analysis measured great magnetic property of the nanocomposite (48 emu/g). Also, the Fe₃O₄@LENT/PVA nanocomposite potential for effective removal of malathion (MA), Diazinon (DA), and Diclofenac (DF) from watery solution has studied by an experiment based on the efficacy of adsorbent dosage, pH, and temperature. The adsorption kinetics of three pollutants had investigated using pseudo-first-order (PFO), pseudo-second-order (PSO) and intra-particle diffusion (IPD) velocity equations, the results showed that the kinetics followed PSO velocity equations. Also, the Langmuir, Freundlich, Dubbin-Radushkevich (D-R) and Temkin isotherm models had investigated, and the adsorption isotherm was adopted from the Langmuir model. The results demonstrated that in the presence of Fe₃O₄@LENT/PVA nanocomposite, at the optimal conditions (contact time = 180 min, pH = 5, nanocomposite dosage = 0.20 g/L and temperature of 298 K) the maximum adsorption capacity of MA, DF, and DA were 101.57, 153.28, and 102.75 mg/g, respectively. The antibacterial features of the Fe₃O₄@LENT/PVA nanocomposite, had evaluated by Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, but the result did not show any antibacterial activity.

Removal of heavy metals from binary and multicomponent adsorption systems using various adsorbents - a systematic review

The ecosystem and human health are both significantly affected by the occurrence of potentially harmful heavy metals in the aquatic environment. In general, wastewater comprises an array of heavy metals, and the existence of other competing heavy metal ions might affect the adsorptive elimination of one heavy metal ion. Therefore, to fully comprehend the adsorbent's efficiency and practical applications, the abatement of heavy metals in multicomponent systems is important. In the current study, the multicomponent adsorption of heavy metals from different complex mixtures, such as binary, ternary, quaternary, and quinary solutions, utilizing various adsorbents are reviewed in detail. According to the systematic review, the adsorbents made from locally and naturally occurring materials, such as biomass, feedstocks, and industrial and agricultural waste, are effective and promising in removing heavy metals from complex water systems. The systematic study further discovered that numerous studies evaluate the adsorption characteristics of an adsorbent in a multicomponent system using various important independent adsorption parameters. These independent adsorption parameters include reaction time, solution pH, agitation speed, adsorbent dosage, initial metal ion concentration, ionic strength as well as reaction temperature, which were found to significantly affect the multicomponent sorption of heavy metals. Furthermore, through the application of the multicomponent adsorption isotherms, the competitive heavy metals sorption mechanisms were identified and characterized by three primary kinds of interactive effects including synergism, antagonism, and non-interaction. Despite the enormous amount of research and extensive data on the capability of different adsorbents, several significant drawbacks hinder adsorbents from being used practically and economically to remove heavy metal ions from multicomponent systems. As a result, the current systematic review provides insights and perspectives for further studies through the thorough and reliable analysis of the relevant literature on heavy metals removal from multicomponent systems.

Adsorption of 2,4-dichlorophenoxyacetic acid and glyphosate from water by Fe3O4-UiO-66-NH2 obtained in a simple green way

In this study, a green adsorbent (Fe₃O₄-UiO-66-NH₂) with the ability of addressing the issues of separation and recovery of UiO-66-NH₂ is obtained using a simple co-precipitation method under environmentally benign conditions. Various characterization techniques are utilized for evaluating the properties of the developed adsorbent. The capability of Fe₃O₄-UiO-66-NH₂ towards 2,4-dichlorophenoxyacetic acid (2,4-D) and glyphosate (GP) from solution is explored. The results revealed that the magnetization process did not destroy the crystal structure of UiO-66-NH₂, which ensured that Fe₃O₄-UiO-66-NH₂ had good adsorption performance for 2,4-D and GP. The adsorption processes showed a wide pH application range, high salt tolerance, and regeneration performance as well as an excellent adsorption rate. Results from thermodynamic study showed that both processes were spontaneous and endothermic. The unit uptake ability of Fe₃O₄-UiO-66-NH₂ for 2,4-D and GP reached up to 249 mg·g^-1 and 183 mg·g^-1 from Langmuir model at 303 K, respectively. When solid-liquid ratio was 2 g·L^-1, Fe₃O₄-UiO-66-NH₂ can reduce the content of 2,4-D or GP with the initial density of 100 mg·L^-1 below the drinking water requirement limit. In addition, the reusability efficiency of Fe₃O₄-UiO-66-NH₂ towards 2,4-D and GP was found to be 86% and 80% using 5 mmol·L^-1 NaOH as eluent. Analysis of simulated water samples indicated that Fe₃O₄-UiO-66-NH₂ could achieve the single or simultaneous removal of 2,4-D and GP from wastewater. Summarily, Fe₃O₄-UiO-66-NH₂ as a green adsorbent can serve as an alternative for removing 2,4-D and GP from water body.

Effective decontamination of methylene blue from aqueous solutions using novel nano-magnetic biochar from green pea peels

The conversion of agricultural waste into high-value carbon products has been an attractive area in waste management strategy. This study highlighted the synthesis and effectiveness of green pea peels (GPP), green pea biochar (GPBC), and nano-ferromagnetic green pea biochar (NFGPBC) by the ferrous/ferric co-precipitation synthesis method for eliminating cationic dyes molecules from solutions. The morphological, physicochemical, and structural properties of GPP, GPBC, and NFGPBC were approved by Scanning Electron Microscopy (SEM), Transmission Emission Microscopy (TEM), Energy Dispersive X-ray (EDX), Bruneau Emmett Teller (BET), Fourier Transform Infrared spectroscopy (FTIR), and X-ray Diffraction (XRD) techniques. Vibrating Sample Magnetometry (VSM) analysis confirmed the NFGPBC magnetization performance. The capacity of each adsorbent for methylene blue removal was evaluated at various parameters of material dosage (50-250 mg/150 mL), pH (2-12), initial concentration (50-250 mg/L), contact time (0-90 min) and temperature (20-60 °C). The three developed adsorbent materials GPP, GPBC, and NFGPBC, possessed reasonable BET surface areas of 0.6836, 372.54, and 147.88 m2g-1, and the corresponding monolayer adsorption capacities of 163.93, 217.40, and 175.44 mg/g, respectively. The superior performances of GPBC and NFGPBC were due to their increased surface area compared with the parent green pea peels (GPP). The results from adsorption kinetics studies of all prepared materials were pseudo-second-order and Elovich kinetics models. The thermodynamic parameters exhibited MB sorption's favorability, spontaneity, and endothermic nature. The NFGPBC material experienced Vander Waal forces, electrostatic interaction, hydrogen bonding, and hydrophobic interactions as predominant modes of the solid-liquid interaction. The regeneration, recycling, and reusability of the synthesized GPP, GPBC, and NFGPBC performed at five adsorption cycles revealed that NFGPBC demonstrated excellent cyclical performances attaining a minimum 8.9% loss in capacity due to paramagnetic properties. Thus, NFGPBC is a green, efficient, and eco-friendly material recommended for large-scale production and application in wastewater.

Origanum vulgare manganese ferrite nanocomposite: An advanced multifunctional hybrid material for dye remediation

The purpose of the study was to fabricate sustainable and cost-effective material for the thorough cleansing of polluted water. In this context, an economical, phytogenic and multifunctional Origanum vulgare plant-based nanocomposite material, MnFe₂O₄/OV, was prepared via one-pot synthetic technique. The synthesized nanocomposite with a band gap of 2.02 eV behaved as an efficient nano-photocatalyst for the degradation of both cationic (crystal violet) and anionic (congo red) dyes under direct sunlight irradiation. The material also inhibited the growth of E. coli and S. aureus bacteria and simultaneously adsorbed both cationic and anionic dyes from water through adsorption. A variety of techniques have been used to characterize the nanocomposite, including X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Additionally, the kinetics of photodegradation of the aforementioned organic dyes has also been investigated. The MnFe₂O₄/OV exhibited excellent photocatalytic performance, leading to 43% and 72% degradation within 3 h at rate constants of 2.0 × 10^-3 min^-1 and 6.0 × 10^-3 min^-1 for crystal violet and congo red, respectively. The crystal violet and congo red were used to testify to the composite's potential for adsorption under the influence of several process variables, including initial solution pH, contact time, temperature, initial dye concentration, and amount of MnFe₂O₄/OV. The Langmuir maximum adsorption capacity Q_max as in the range 14.06-14.59 mgg^-1 for crystal violet and 34.45-23.93 mgg^-1 for congo red at pH 7 within 90 min contact time in the temperature range of 30-50 °C. The phenomenon of adsorption was found feasible and endothermic at all the investigated temperatures. Also, E. coli and S. Aureus bacteria have shown growth suppression activity when exposed to MnFe₂O₄/OV.As a result, the synthesized nanocomposite, MnFe₂O₄/OV, proved to be an antimicrobial, multifunctional novel nanocomposite, which is in high demand, and could serve as an affordable, and sustainable material for comprehensive water filtration.

Overview on recent advances of magnetic metal-organic framework (MMOF) composites in removal of heavy metals from aqueous system

Developing a novel, simple, and cost-effective analytical technique with high enrichment capacity and selectivity is crucial for environmental monitoring and remediation. Metal-organic frameworks (MOFs) are porous coordination polymers that are self-assembly synthesized from organic linkers and inorganic metal ions/metal clusters. Magnetic metal-organic framework (MMOF) composites are promising candidate among the new-generation sorbent materials available for magnetic solid-phase extraction (MSPE) of environmental contaminants due to their superparamagnetism properties, high crystallinity, permanent porosity, ultrahigh specific surface area, adaptable pore shape/sizes, tunable functionality, designable framework topology, rapid and ultrahigh adsorption capacity, and reusability. In this review, we focus on recent scientific progress in the removal of heavy metal ions present in contaminated aquatic system by using MMOF composites. Different types of MMOFs, their synthetic approaches, and various properties that are harnessed for removal of heavy metal ions from contaminated water are discussed briefly. Adsorption mechanisms involved, adsorption capacity, and regeneration of the MMOF sorbents as well as recovery of heavy metal ions adsorbed that are reported in the last ten years have been discussed in this review. Moreover, particular prospects, challenges, and opportunities in future development of MMOFs towards their greener synthetic approaches for their practical industrial applications have critically been considered in this review.

Enhanced elemental mercury removal in coal-fired flue gas by modified algal waste-derived biochar: Performance and mechanism

A novel biochar involving pyrolysis of dewatered algal waste combined with KOH and residual FeCl₃ co-activation was synthesized as an efficient sorbent specifically for Hg⁰ removal from coal-fired flue gas. It was found that the S_BET of biochar co-activated by KOH and FeCl₃ (BCFK) was 195.82 m² g^-1, much higher than that of single FeCl₃ activated biochar (BCF) of 133.38 m² g^-1 and un-activated biochar (UBC) of 20.36 m² g^-1. Furthermore, BCFK exhibited higher magnetization characteristics as well as elemental Fe and Cl contents of 2.71% and 10.33%, respectively, based on the combined characterization of XPS and VSM, etc., which is a jump of about 10-fold compared to BCF. This allows BCFK to show the best Hg⁰ removal capability of 689.66 μg g^-1 under the inlet Hg⁰ concentration of 100 μg m^-3 and 150 °C, according to pseudo-second-order kinetic model. Further analysis by XPS and Hg-TPD (Temperature Programmed Desorption) revealed that oxidation by Cl∗ radicals and C-Cl as well as weak chemisorption contributed to the removal of Hg⁰. Eventually, this efficient, simply prepared, low-cost and easily separable biochar distinguished itself in comparison to other materials. This will undoubtedly promote the valorization of algae and provide a reliable alternative material for the treatment of coal-fired flue gas.

"Magnetic Ni-Zn ferrite anchored on g-C3N4 as nano-photocatalyst for efficient photo-degradation of doxycycline from water"

In the present work, mixed-spinel ferrite anchored onto graphitic carbon nitride (GCN) was synthesized for mineralization of antibiotic pollutant from waste water. A Z-scheme g-C₃N₄/Ni_0.5Zn_0.5Fe₂O₄ nano heterojunction was fabricated by three step procedure: pyrolysis, solution combustion and mechanical grinding followed by annealing. The prepared photocatlyst was tested for degradation of Doxycycline (DC) drug under the natural sun light. Results revealed that the prepared heterojunction has maximum degradation efficiency of 97.10% pollutant in 60 min experiment. The Z-scheme heterojunction between g-C₃N₄ and Ni-Zn ferrite improves the photoinduced charges separation and protection of redox capability and therby increases the photo degradation efficiency. The scavenging experiments suggested that O₂^-● and h⁺ as main active species responsible for degradation of the antibiotic. In addition, the dopant variation can drive the shists in band gap and energy band positiong too which makes then excellent candidates for synthesizing tunable heterostructures with organic semiconductors. The work focusses on designing and developing of saimpler but efficient magnetic heterojunctions with superior redox capability for solar powered waste water treatment.

Towards a win-win chemistry: extraction of C.I. orange from Kamala fruit (Mallotus philippensis), and simultaneous exercise of its peels for the removal of Methylene Blue from water

Kamala fruit (Mallotus philippensis), hereinafter MP, has been simultaneously exercised for the extraction of a natural dye, C.I. orange and its peels were converted into an efficient adsorbent for the rapid removal of methylene blue (MB) dye from aqueous solutions. The material has been characterized by Fourier Transform Infra-red (FTIR),Field Emission Scanning Electron Microscopy- Electron dispersive spectroscopy (FESEM-EDS), Brunauer-Emmett-Teller (BET) surface area, and pH_ZPC. FTIR suggests the presence of polyphenolic moieties responsible for adsorption, whereas FESEM confirms the porous texture. Optimization of process variables such as contact time, pH, adsorbent dose, and temperature of operation indicates that the adsorption gets modulated by the pH, with a best at 11. The Freundlich model (R² = 0.994), and pseudo-second-order kinetics (R² = 0.999) best describe the adsorption pathway. Dilute hydrochloric acid is sufficient to induce >66% regeneration, which ensures reusability. With the maximal uptake for MB is 30.2 mg/g at ambient conditions, the superiority over the existing materials has been confirmed. Treatment of dye containing industrial effluent suggests about a 50% reduction in one cycle. It can be concluded that both-way benefits, namely natural dye extraction and preparation of a peel-based adsorbent for methylene blue removal from aqueous solution, can be achieved using the kamala fruit peels.

Recent developments of magnetic nanoadsorbents for remediation of arsenic from aqueous stream

One of the emerging environmental concerns is the high levels of arsenic ions found in groundwater and other water sources. Decontaminating water that contains arsenic is crucial for environmental and health reasons. Nano-adsorbents have gained much interest recently for the adsorptive removal of arsenic species from wastewater. On the other hand, for their prospective use in natural water treatment, current nano-adsorbents must be separated from treated fluids. Researchers studied nanocomposite iron oxide-based adsorbents to overcome these problems and to design effective sorbents for removing arsenic. This study provides a summary of current developments in the field of magnetic nanoadsorbents for the removal of various arsenic compounds from wastewater. Adsorption of arsenic from groundwater has been found to be very promising for magnetic nanoadsorbents. In order to eliminate arsenic from the aqueous phase, magnetic nanocomposite adsorbents may offer practical and affordable water purification solutions.

Synergetic effect of green synthesized reduced graphene oxide and nano-zero valent iron composite for the removal of doxycycline antibiotic from water

In this work, the synthesis of an rGO/nZVI composite was achieved for the first time using a simple and green procedure via Atriplex halimus leaves extract as a reducing and stabilizing agent to uphold the green chemistry principles such as less hazardous chemical synthesis. Several tools have been used to confirm the successful synthesis of the composite such as SEM, EDX, XPS, XRD, FTIR, and zeta potential which indicated the successful fabrication of the composite. The novel composite was compared with pristine nZVI for the removal aptitude of a doxycycline antibiotic with different initial concentrations to study the synergistic effect between rGO and nZVI. The adsorptive removal of bare nZVI was 90% using the removal conditions of 25 mg L^-1, 25 °C, and 0.05 g, whereas the adsorptive removal of doxycycline by the rGO/nZVI composite reached 94.6% confirming the synergistic effect between nZVI and rGO. The adsorption process followed the pseudo-second order and was well-fitted to Freundlich models with a maximum adsorption capacity of 31.61 mg g^-1 at 25 °C and pH 7. A plausible mechanism for the removal of DC was suggested. Besides, the reusability of the rGO/nZVI composite was confirmed by having an efficacy of 60% after six successive cycles of regeneration.

Electrospun tannin-rich nanofibrous solid-state membrane for wastewater environmental monitoring and remediation

Heavy metal, organic dyes, and bacterial contamination in water endanger human/animals' health, and therefore, the detection, adsorption, and capturing of contaminants are essential for environmental safety. Ligand-rich membranes are promising for sensors, adsorption, and bacterial decontamination. Herein, tannin (TA)-reinforced 3-aminopropyltriethoxysilane (APTES) crosslinked polycaprolactone (PCL) based nanofibrous membrane (PCL-TA-APTES) was fabricated via electrospinning. PCL-TA-APTES nanofibers possess superior thermal, mechanical, structural, chemical, and aqueous stability properties than the un-crosslinked membrane. It changed its color from yellowish to black in response to Fe^2+/3+ ions due to supramolecular iron-tannin network (FeTA) interaction. Such selective sensing has been noticed after adsorption-desorption cycles. Fe³⁺ concentration, solution pH, contact time, and ligand concentration influence FeTA coordination. Under optimized conditions followed by image processing, the introduced membrane showed a colorimetric linear relationship against Fe³⁺ ions (16.58 μM-650 μM) with a limit of detection of 5.47 μM. The PCL-FeTA-APTES membrane could restrain phenolic group oxidation and result in a partial water-insoluble network. The adsorption filtration results showed that the PCL-FeTA-APTES membrane can be reused and had a higher methylene blue adsorption (32.04 mg/g) than the PCL-TA-APTES membrane (14.96 mg/g). The high capture efficiency of nanocomposite against Fe³⁺-based S. aureus suspension than Fe³⁺-free suspension demonstrated that Fe³⁺-bounded bacterium adhered to the nanocomposite through Fe³⁺/TA-dependent biointerface interactions. Overall, high surface area, rich phenolic ligand, porous microstructure, and super-wetting properties expedite FeTA coordination in the nanocomposite, crucial for Fe^2+/3+ ions sensing, methylene blue adsorption-filtration, and capturing of Fe³⁺-bounded bacterium. These multifunctional properties could promise nanocomposite membrane practicability in wastewater and environmental protection.

Analytical perspective and environmental remediation potentials of magnetic composite nanosorbents

The synthesis and application of magnetic nanosorbents to remove emerging pollutants have been considered the best environmental remediation and sustainability option. Incorporating magnetism shortens the treatment time and allows the sorbent to be recovered quickly using external magnetic with many cycles. The implementation of magnetic solid-phase extraction (MSPE) using magnetic materials of different shapes, sizes, and surface morphology can be a valuable tool in applying materials to prepare analytical samples. In MSPE applications, materials with strong magnetic domain can be used as precursors for constructing magnetic composite as a promising sorbent. This article focuses on the most recent and exceptional applications of magnetic adsorbents for preconcentration and removal purposes. Magnetic adsorbents, such as nanoparticles (NPs), foam, sponges, nanocomposites, hydrogels, and beads with multifunctional attributes have been comprehensively studied in terms of preparation procedures, limitations, advantages, and interactions between pollutants and magnetic composites. The role of magnetic sorbents in sample preparation methods, such as simple solid-phase extraction and microextraction, as well as sorptive extraction using a stir bar, was also examined. The use of magnetic adsorbents with analytical techniques, such as solid-phase extraction and solid-phase microextraction improves the method for preparing samples concerning the influential role of magnetic adsorbents. Towards the end, promising features and future outlook are also directed.

Economic and facile approach for synthesis of graphene-titanate nanocomposite for water reclamation

Graphene and its composites with semiconductor materials have been received highly attention in many research areas because of their unique properties. Efficient application of graphene is hindered by the lack of cost-effective synthesis methods. In this work, an economic and facile route for mass production of graphene-titanate nanocomposite has been discussed. Graphene was prepared by exfoliation of graphite powder in 40% ethanol aqueous solution. Titanate nanotubes were grown on graphene sheets by hydrothermal method, where the dispersed graphene sheets were mixed with titanate solution and then placed in autoclave and placed in oven for 16 h at 160 °C. The prepared composite was characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR), thermogravimetric analysis (TGA). All the obtained results confirmed the synthesis of graphene and its composite with titanate in highly uniform and pure form. The adsorption efficiency of the prepared composite was tested using methylene blue (MB) as a model dye. The adsorption isotherm was investigated using Freundlich and Langmuir models. The adsorption capacity of MB was 270.27 mg/g. The obtained correlation coefficients (R²) by Freundlich and Langmuir model were 0.996 and 0.973, respectively. The adsorption kinetics was investigated and discussed using different models. The thermal stability of the developed composite is improved after MB adsorption.

Recent advances in starch-based magnetic adsorbents for the removal of contaminants from wastewater: A review

Considerable concern exists regarding water contamination by various pollutants, such as conventional pollutants (e.g., heavy metals and organics) and emerging micropollutants (e.g., consumer care products and interfering endocrine-related compounds). Currently, academics are continuously exploring sustainability-related materials and technologies to remove contaminants from wastewater. Magnetic starch-based adsorbents (MSAs) can combine the advantages of starch and magnetic nanoparticles, which exhibit unique critical features such as availability, cost-effectiveness, size, shape, crystallinity, magnetic properties, stability, adsorption properties, and excellent surface properties. However, limited reviews on MSAs' preparations, characterizations, applications, and adsorption mechanisms could be available nowadays. Hence, this review not only focuses on their activation and preparation methods, including physical (e.g., mechanical activation treatment, microwave radiation treatment, sonication, and extrusion), chemical (e.g., grafting, cross-linking, oxidation and esterification), and enzymatic modifications to enhance their adsorption properties, but also offers an all-round state-of-the-art analysis of the full range of its characterization methods, the adsorption of various contaminants, and the underlying adsorption mechanisms. Eventually, this review focuses on the recycling and reclamation performance and highlights the main gaps in the areas where further studies are warranted. We hope that this review will spark an interdisciplinary discussion and bring about a revolution in the applications of MSAs.

Structure and magnetization of a magnetoactive ferrocomposite

This work is devoted to the theoretical study of the structural and magnetic properties of an ensemble of single-domain interacting magnetic nanoparticles immobilized in a non-magnetic medium. This model is typical for describing magnetically active soft materials, "smart" polymer ferrocomposites, which have been applied in science-intensive industrial and biomedical technologies. It is assumed that the ferrocomposite is obtained by solidification of the carrier medium in a ferrofluid under an external magnetic field, the intensity of which is determined by the Langevin parameter α_p; after the solidification of the carrier liquid, the nanoparticles retain the spatial distribution and orientation of their easy magnetization axes. The features of the orientational texture formed in the sample are analyzed depending on the intensity of the magnetic field α_p and interparticle dipole-dipole interactions. The magnetization of a textured ferrocomposite in the magnetic field α is also investigated. Our results show that in the case of a co-directional arrangement of the considered fields and if α < α_p, the ferrocomposites are magnetized much more efficiently than ferrofluids due to their texture. In the fields α > α_p, the ferrocomposite is magnetized less efficiently than the ferrofluid due to the internal magnetic anisotropy of the nanoparticles. The analytical expressions presented here make it possible to predict the magnetization of a ferrocomposite depending on its internal structure and synthesis conditions, which is the theoretical basis for the synthesis of ferrocomposites with a predetermined magnetic response in a given magnetic field.

Kanchan Arsenic Filters for Household Water Treatment: Unsuitable or Unsustainable?

This article critically evaluates the conventional Kanchan Arsenic Filter (KAF) in order to determine the main reasons for its reported poor performance. The KAF was introduced in 2004 in Nepal and makes use of non-galvanized nails as a Fe0 source for As removal. As early as 2009, the KAF was demonstrated to be ineffective for As removal in many cases. This was unambiguously attributed to the Fe0 layer which is placed on top of a sand filter instead of being incorporated into a sand matrix. Despite this conceptual mistake, the conventional KAF has been largely distributed in Asia, and recent articles have assessed its sustainability. This study reiterates that the suitability of the technology, rather than its sustainability, should be addressed. Evidence shows that the KAF has the following design limitations: (i) uses iron nails of unknown reactivity, and (ii) operates on the principle of a wet/dry cycle. The latter causes a decrease in the corrosion rate of the used nails, thereby limiting the availability of the iron corrosion products which act as contaminant scavengers. Taken together, these results confirm the unsuitability of the conventional KAF. Besides correcting the design mistakes, more attention should be paid to the intrinsic reactivity of the used iron nails, including using alternative Fe0 materials (e.g., iron filings, steel wool) for filters lasting for just 6 or 18 months. Specific design considerations to be addressed in the future are highlighted.

Continuous antibiotic attenuation in algal membrane photobioreactor: Performance and kinetics

The attenuation of 10 mixed antibiotics along with nutrients in a continuous flow mode by four freshwater microalgae (Haematococcus pluvialis, Selenastrum capricornutum, Scenedesmus quadricauda, and Chlorella vulgaris) was examined in membrane photobioreactors (MPBRs). At lab-scale, consistent removal of both antibiotic and nutrient was shown by H. pluvialis and S. quadricauda, respectively. The system exhibited better performance with enhanced removal at HRT 24 h compared to 12 h and 48 h. The highest removal efficiency of antibiotics was observed in H. pluvialis MPBR, with the mean antibiotic removal values of 53.57%- 96.33%. Biodegradation was the major removal pathway of the antibiotics in the algal-MPBR (AMPBR), while removal by bioadsorption, bioaccumulation, membrane rejection, and abiotic was minor. Then, the bacterial feature was studied and showed significant influence from system hydrodynamics. The kinetics of continuous flow antibiotic removal followed Stover-Kincannon and Grau second-order models, which revealed great potential of AMPBR to withstand antibiotic load. The latter coupled with the computational fluid dynamic simulation was successfully applied for the residual antibiotic prediction and potential system optimization. Overall, these results provide an important reference for continuous flow antibiotic removal using AMPBR.

Investigation the adsorption behavior of functional biochar-based porous composite for efficient removing Cu(Ⅱ) in aqueous solution

Biochar was modified by acylation reaction using EDTA. Then, a novel biochar-based porous composite was prepared successfully using modified biochar as base to remove Cu(Ⅱ) in wastewater. In addition, functional...