Performance of algal activated carbon/Fe3O4 magnetic composite for cationic dyes removal from aqueous solutions

Photocatalytic activity of ZnO doped Nano hydroxyapatite/GO derived from waste oyster shells for removal of Methylene blue

Hydroxyapatite (HAp) stands as an inorganic compound, recognized as a non-toxic, bioactive ceramic, and its composition closely resembles that of bone material. In this study, nHAp was prepared from waste oyster shells, which are biowaste rich in calcium carbonate. nHAp with its unique catalytic property can be used as an adsorbent in various fields, including wastewater treatment. nHAp with an exceptional surface adsorbent with excellent chemical stability, enabling its catalytic function. Nano hydroxyapatite doped with Zinc oxide (ZnO) by wet chemical precipitation and made into a composite with Graphene oxide (GO) by modified hummers method followed by grinding, which was taken as 9:1 ratio (nHAp/ZnO and GO) of weight, enhances its tensile and mechanical strength. The energy band gap of nHAp photocatalyst was evaluated as 3.39 eV and that of the in nHAp/ZnO/GO photocatalyst was narrowed to 1.77 eV. The ternary nanocomposites are very efficient in generating the photogenerated electrons and holes, thereby improving the degradation potential of dye effluents to by-products such as CO2 and H2O. The nanocomposites photocatalyst were characterized by FTIR, XRD, SEM, TEM, EDS, XPS, DRS, and BET techniques. The UV-visible study shows the complete dye degradation efficiency of the prepared nanocomposites photocatalyst. In this study, the prepared nanocomposites nHAp/ZnO/GO have studied their efficiency for the removal of MB dye in a batch process by varying the dosage from 0.1 to 0.5 g, and the effects of dosage variations, pH, kinetic, scavenger study were evaluated at a time interval of 30 min. The removal of dye was found to be 99% at 150 min of 0.3 g dosage and pH = 12 is most favorable as it reached the same percentage at 90 min. The as-prepared nanocomposite nHAp/ZnO/GO fits the kinetic rate constant equation and shows a pseudo-first-order reaction model. This study indicates the suitability for dye removal due to the synergistic effect and electrostatic interaction of the synthesized ternary nanocomposite, which shows the potential, socially active, low-cost-effective, eco-friendly, and safe for photocatalytic degradation of MB from wastewater.

Effective removal of microplastics by filamentous algae and its magnetic biochar: Performance and mechanism

In recent years, filamentous algae blooms and microplastics (MPs) pollution have become two major ecological and environmental problems in urban water systems. In order to solve these two problems at the same time, this study explored the loading capacity of MPs on fresh filamentous algae, and successfully synthesized magnetic filamentous algae biochar loading with Fe3O4 by hydrothermal method, with the purpose of removing MPs from water. The magnetic filamentous algal biochar was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and so on. Experiments on adsorption kinetics, adsorption isotherms and optimum pH were carried out to explore the adsorption mechanism of MPs on magnetic filamentous algal biochar. The adsorption kinetics and adsorption isotherm models were evaluated, and the selection criterion for the appropriate model was determined by using the residual sum of squares (RSS) and Bayesian information criterion (BIC). Microscope images revealed that fresh filamentous algae could interact with MPs in the form of entanglement, adhesion and encapsulation. The average load of MPs in filamentous algae samples was 14.1 ± 5 items/g dry weight. The theoretical maximum adsorption capacities of polystyrene MPs (PS-MPs) by raw biochar (A500) and magnetic biochar with Fe3O4 (M2A500) were 176.99 mg/g and 215.58 mg/g, respectively. The adsorbent materials gave better reusability because they could be reused up to five times. Overall, these findings have provided new insights into the use of filamentous algae for in situ remediation of fluvial MPs pollution, as well as feasible strategies for the recycling of algal waste.

Biogenic magnetic nanocomposite of hydroxyapatite and dextran: synthesis, characterization, and enhanced removal of 2,4-D from aqueous environment

In this study, a biogenic magnetic nanocomposite, HAP@DEX@MNP, using hydroxyapatite from eggshell waste and dextran was developed to efficiently remove 2,4-D from aqueous solutions. The magnetic nano biocomposite underwent rigorous characterization using a comprehensive suite of analytical techniques, including FTIR, XRD, FESEM, EDX, TEM, and VSM. FTIR analysis was used to validate the existence of pivotal functional groups, such as phosphate, carbonyl, hydroxyl, and iron oxide. XRD analysis verified both the crystalline nature of hydroxyapatite and the successful integration of dextran and hematite within the composite structure. FESEM and EDX examinations provided valuable insights into the surface morphology and elemental composition. TEM observations elucidated the existence of nano-sized particles underscoring the unique structural characteristics of the nanocomposite. Batch adsorption experiments were conducted under optimized conditions, highlighting the critical role of pH 2 for efficient 2,4-D removal. The mechanisms driving the binding of 2,4-D to HAP@DEX@MNP were found to encompass diverse interactions, encompassing electrostatic forces, hydrogen bonding, π-π interactions, and van der Waals forces. Adsorption isotherm studies revealed both monolayer and multilayer adsorption, with the Langmuir and Freundlich models fitting well, indicating a maximal adsorption capacity of 217.39 µg/g at 25 °C. Kinetic investigations supported the pseudo-second-order model for efficient adsorption dynamics, and thermodynamic analysis emphasized the versatility of HAP@DEX@MNP across different temperatures. Importantly, the study highlighted the remarkable regenerative capacity of the nanocomposite using a 0.1 M NaOH solution, positioning it as an environmentally friendly option for water treatment. In conclusion, HAP@DEX@MNP holds significant potential for diverse applications in addressing global water treatment and environmental challenges.

A review on sustainable management of biomass: physicochemical modification and its application for the removal of recalcitrant pollutants-challenges, opportunities, and future directions

Adsorption is one of the most efficient methods for remediating industrial recalcitrant wastewater due to its simple design and low investment cost. However, the conventional adsorbents used in adsorption have several limitations, including high cost, low removal rates, secondary waste generation, and low regeneration ability. Hence, the focus of the research has shifted to developing alternative low-cost green adsorbents from renewable resources such as biomass. In this regard, the recent progress in the modification of biomass-derived adsorbents, which are rich in cellulosic content, through a variety of techniques, including chemical, physical, and thermal processes, has been critically reviewed in this paper. In addition, the practical applications of raw and modified biomass-based adsorbents for the treatment of industrial wastewater are discussed extensively. In a nutshell, the adsorption mechanism, particularly for real wastewater, and the effects of various modifications on biomass-based adsorbents have yet to be thoroughly studied, despite the extensive research efforts devoted to their innovation. Therefore, this review provides insight into future research needed in wastewater treatment utilizing biomass-based adsorbents, as well as the possibility of commercializing biomass-based adsorbents into viable products.

Polypyrrole-decorated bentonite magnetic nanocomposite: A green approach for adsorption of anionic methyl orange and cationic crystal violet dyes from contaminated water

In the presented study, a novel polypyrrole-decorated bentonite magnetic nanocomposite (MBnPPy) was synthesized for efficient removal of both anionic methyl orange (MO) and cationic crystal violet (CV) dyes from contaminated water. The synthesis of this novel adsorbent involved a two-step process: the magnetization of bentonite followed by its modification through in-situ chemical polymerization. The adsorbent was characterized by SEM/EDX, TEM/SAED, BET, TGA/DTA-DTG, FTIR, VSM, and XRD studies. The investigation of the adsorption properties of MBnPPy was focused on optimizing various parameters, such as dye concentration, medium pH, dosage, contact time, and temperature. The optimal conditions were established as follows: dye concentration of Co (CV/MO) at 100 mg/L, MBnPPy dosage at 2.0 g/L, equilibrium time set at 105 min for MO and 120 min for CV, medium pH adjusted to 5.0 for MO dye and 8.0 for CV dye, and a constant temperature of 303.15 K. The different kinetic and isotherm models were applied to fit the experimental results, and it was observed that the Pseudo-2nd-order kinetics and Langmuir adsorption isotherm were the best-fitted models. The maximal monolayer adsorption capacities of the adsorbent were found to be 78.74 mg/g and 98.04 mg/g (at 303.15 K) for CV and MO, respectively. The adsorption process for both dyes was exothermic and spontaneous. Furthermore, a reasonably good regeneration ability of MBnPPy (>83.45%/82.65% for CV/MO) was noted for up to 5 adsorption-desorption cycles with little degradation. The advantages of facile synthesis, cost-effectiveness, non-toxicity, strong adsorption capabilities for both anionic and cationic dyes, and easy separability with an external magnetic field make MBnPPy novel.

Synthesis and efficiency comparison of reed straw-based biochar as a mesoporous adsorbent for ionic dyes removal

The reed straw is assessed as a potential source of widely available renewable biomass for biochar production and compared with two other waste-based biomasses, namely fruit stones blend, and brewery spent grains. The biochars were activated via steam and CO2. While steam activation yielded 12 % carbon from reed biomass, CO2 activation resulted in biomass degradation. The characterization of reed biochar showed a mesoporous structure and a high surface area of 514 m2/g. The adsorption tests displayed a decent adsorption capacity of biochar, with values of 92.6 mg/g for methylene violet dye and 35.7 mg/g for acid green dye. Only 1 g/L dosage of reed biochar was able to remove 99 % of the 50 mg/L methylene violet solution in 15 min and 60 % of the 50 mg/L acid green solution in 10 min. The obtained results demonstrate reed biomass as a suitable source for biochar production as well as reed-based biochar as a promising dye adsorbent.

Novel rod-like [Cu(phen)2(OAc)]·PF6 complex for high-performance visible-light-driven photocatalytic degradation of hazardous organic dyes: DFT approach, Hirshfeld and fingerprint plot analysis

A novel octahedral distorted coordination complex was formed from a copper transition metal with a bidentate ligand (1,10-Phenanthroline) and characterized by Ultraviolet-visible spectroscopy, Ultraviolet-visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller, Field emission scanning electron microscopy, and Single-crystal X-ray diffraction. The Hirshfeld surface and fingerprint plot analyses were conducted to determine the interactions between atoms in the Cu(II) complex. DFT calculations showed that the central copper ion and its coordinated atoms have an octahedral geometry. The Molecular electrostatic potential (MEP) map indicated that the copper (II) complex is an electrophilic compound that can interact with negatively charged macromolecules. The HOMO-LUMO analysis demonstrated the π nature charge transfer from acetate to phenanthroline. The band gap of [Cu(phen)2(OAc)]·PF6 photocatalyst was estimated to be 2.88 eV, confirming that this complex is suitable for environmental remediation. The photocatalytic degradation of erythrosine, malachite green, methylene blue, and Eriochrome Black T as model organic pollutants using the prepared complex was investigated under visible light. The [Cu(phen)2(OAc)]·PF6 photocatalyst exhibited degradation 94.7, 90.1, 82.7, and 74.3 % of malachite green, methylene blue, erythrosine, and Eriochrome Black T, respectively, under visible illumination within 70 min. The results from the Langmuir-Hinshelwood kinetic analysis demonstrated that the Cu(II) complex has a higher efficiency for the degradation of cationic pollutants than the anionic ones. This was attributed to surface charge attraction between photocatalyst and cationic dyes promoting removal efficiency. The reusability test indicated that the photocatalyst could be utilized in seven consecutive photocatalytic degradation cycles with an insignificant decrease in efficiency.

Electrophoretically deposited sulfonated poly(styrene-co-divinylbenzene) on a screw for microextraction of cationic dyes from aqueous solutions

In the present work, a novel solid-phase microextraction on a screw (MES) was employed to extract cationic dyes (malachite green, methylene blue, and rhodamine B) from food samples and fish breeding pool water. The sulfonated poly(styrene-co-divinylbenzene) was electrophoretically deposited on the surface of the grooves of a screw. Then the screw was placed inside a silicon tube as a holder to create a channel to run a test solution through it. The extracted dyes on the coated screw were eluted by a suitable eluent. High-performance liquid chromatography with an ultraviolet/visible detector was utilized for the separation and analysis of the analytes. The effective parameters of the analyte extraction efficiency were optimized. Under optimum conditions, the limits of detection were 0.15 μg/L, and calibration curves were linear in the range of 0.50-250.00 μg/L, with coefficients of determination > 0.989 for all studied dyes. The relative standard deviations of intra and inter-day (n = 3) were in the range of 2.8%-7.0% and 7.0%-9.5%, respectively. The MES was applied as a simple and repeatable method with acceptable relative recoveries (82.0%-103.0%) for the determination of cationic dyes in grape nectar, ice pop, jelly powder, and fish breeding pool water.

Magnetic Fe3O4 nanoparticles loaded guava leaves powder impregnated into calcium alginate hydrogel beads (Fe3O4-GLP@CAB) for efficient removal of methylene blue dye from aqueous environment: Synthesis, characterization, and its adsorption performance

In the present work, a novel Fe3O4-GLP@CAB was successfully synthesized via a co-precipitation procedure and applied for the removal of methylene blue (MB) from aqueous environment. The structural and physicochemical characteristics of the as-prepared materials were explored using a variety of characterization methods, including pHPZC, XRD, VSM, FE-SEM/EDX, BJH/BET, and FTIR. The effects of several experimental factors on the uptake of MB using Fe3O4-GLP@CAB were examined through batch experiments. The highest MB dye removal efficiency of Fe3O4-GLP@CAB was obtained to be 95.2 % at pH 10.0. Adsorption equilibrium isotherm data at different temperatures showed an excellent agreement with the Langmuir model. The adsorption uptake of MB onto Fe3O4-GLP@CAB was determined as 136.7 mg/g at 298 K. The kinetic data were well-fitted by the pseudo-first-order model, indicating that physisorption mainly controlled it. Several thermodynamic variables derived from adsorption data, like as ΔGo, ΔSo, ΔHo, and Ea, accounted for a favourable, spontaneous, exothermic, and physisorption process. Without seeing a substantial decline in adsorptive performance, the Fe3O4-GLP@CAB was employed for five regeneration cycles. Because they can be readily separated from wastewater after treatment, the synthesized Fe3O4-GLP@CAB was thus regarded as a highly recyclable and effective adsorbent for MB dye.

Modeling of methylene blue removal on Fe3O4 modified activated carbon with artificial neural network (ANN)

In this study, AC/Fe3O4 adsorbent was first synthesized by modifying activated carbon with Fe3O4. The structure of the adsorbent was then characterized using analysis techniques specific surface area (BET), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), and Fourier Transform Infrared Spectroscopy (FTIR). Equilibrium, thermodynamic and kinetic studies were carried out on the removal of methylene blue (MB) dyestuff from aqueous solutions AC/Fe3O4 adsorbent. The Langmuir maximum adsorption capacity of AC/Fe3O4 was 312.8 mg g-1, and the best fitness was observed with the pseudo-second-order kinetics model, with an endothermic adsorption process. In the final stage of the study, the adsorption process of MB on AC/Fe3O4 was modeled using artificial neural network modeling (ANN). Considering the smallest mean square error (MSE), The backpropagation neural network was configured as a three-layer ANN with a tangent sigmoid transfer function (Tansig) at the hidden layer with 10 neurons, linear transfer function (Purelin) the at output layer and Levenberg-Marquardt backpropagation training algorithm (LMA). Input parameters included initial solution pH (2.0-9.0), amount (0.05-0.5 g L-1), temperature (298-318 K), contact time (5-180 min), and concentration (50-500 mg L-1). The effect of each parameter on the removal and adsorption percentages was evaluated. The performance of the ANN model was adjusted by changing parameters such as the number of neurons in the middle layer, the number of inputs, and the learning coefficient. The mean absolute percentage error (MAPE) was used to evaluate the model's accuracy for the removal and adsorption percentage output parameters. The absolute fraction of variance (R2) values were 99.83, 99.36, and 98.26% for the dyestuff training, validation, and test sets, respectively.

Alginate@Fe3O4@Bentonite nanocomposite for formaldehyde removal from synthetic and real effluent: optimization by central composite design

In this study, Alginate@ Fe₃O₄/Bentonite nanocomposite was utilized to eliminate formaldehyde from wastewater. Structural features of bentonite, bentonite@Fe₃O₄, and Alginate@Fe₃O₄@Bentonite were determined using FT-IR, PXRD, Mapping, EDX, TEM, SEM, VSM, and BET analyses. The central composite design method was employed to find the optimal conditions for formaldehyde removal using Alg@Fe₃O₄@Bent nanocomposite. The maximum formaldehyde uptake efficiency (94.56%) was obtained at formaldehyde concentration of 10.69 ppm, the nanocomposite dose of 1.28 g/L, and pH of 9.96 after 16.53 min. Also, Alginate@Fe₃O₄@Bentonite composite was used to eliminate formaldehyde from Razi petrochemical wastewater and was able to eliminate 91.24% of formaldehyde, 70% of COD, and 68.9% of BOD₅. The isotherm and kinetic investigations demonstrated that the formaldehyde uptake process by the foresaid adsorbent follows the Langmuir isotherm and quasi-first-order kinetic models, respectively. Also, the maximum uptake capacity was obtained at 50.25 mg/g. Moreover, the formaldehyde uptake process by the aforementioned nanocomposite was exothermic and spontaneous. Furthermore, the formaldehyde adsorption efficiency decreased slightly after six reuse cycles (less than 10%), indicating that Alginate@Fe₃O₄@Bentonite nanocomposite has remarkable recyclability. Besides, the influence of interfering ions like nitrate, carbonate, chloride, phosphate, and sulfate was studied on the formaldehyde removal efficiency and the results displayed that all ions except nitrate ion have low interaction with formaldehyde (less than 3% reduction in removal efficiency).

Modification of Chlorella vulgaris carbon with Fe3O4 nanoparticles for tetracycline elimination from aqueous media

Tetracycline (TTC) is an antibiotic commonly prescribed to treat bacterial infections in animals and humans because of its low toxicity and antibacterial activity. This study focuses on the removal of TTC from an aqueous media using an activated carbon of Chlorella vulgaris modified with Fe₃O₄ magnetic composite (ACCV/Fe₃O₄ mc). The isothermal and kinetic models were studied to understand the adsorption mechanism. The Box-Behnken model was used for experimental design, and the main research parameters were ACCV/Fe₃O₄ mc mass (0.2-0.8 g/L), reaction time (10-60 min), TTC concentration (5-30 mg/L), and pH (3-11). The highest TTC removal rate of 90.47% was obtained at a pH of 7, a time of 60 min, an ACCV/Fe₃O₄ mc mass of 0.5 g/L, and an antibiotic concentration of 5 mg/L. TTC removal was fitted with the pseudo-second-order and the Langmuir model. The Langmuir adsorption capacity of TTC was computed to be 26.18 mg/g. The results show that the ACCV/Fe₃O₄ mc adsorbent significantly removes TTC from the aqueous solution.

One-step in-situ sustainable synthesis of magnetic carbon nanocomposite from corn comb (MCCC): agricultural biomass valorisation for pollutant abatement in wastewater

This study explored a novel, eco-friendly, sustainable, low-cost, and abundantly available corn comb (CC) agricultural biomass waste-derived one-step in-situ synthesis of magnetic carbon (MCCC) as an efficient adsorbent for water decontamination applications. Herein, we developed a robust and easily separable MCCC by carbonization of Fe(NO₃)₃.9H₂O single iron salt-soaked CC at 500 °C for 5 h. The as-synthesized MCCC was confirmed for their physicochemical properties by various characterization techniques viz. scanning electron microscopy (SEM), high-resolution transmission emission microscopy (HR-TEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface area measurements by Brunauer-Emmett-Teller (BET) study, Raman analysis, and magnetic behavior by VSM analysis. The adsorption properties of MCCC on prototypical pollutant methylene blue (MB) was monitored depending on the effect of pH, adsorbent dose, contact time, and varying concentrations of MB. Especially, the π-π interactions played important role in the adsorption of MB at acidic pH (pH = 4). The MCCC displayed a maximum uptake capacity of 120.73 ± 0.63 mg/g toward MB. The Langmuir, Freundlich, and Temkin adsorption isotherm models were fitted with determined coefficient (R²) values of 0.99, 0.95, and 0.96 respectively. The kinetics of the adsorption process was well fitted with a pseudo-second-order model (R² = 0.99). Most significantly, the as-designed easily separable, and reusable adsorbent, MCCC was effectively applied for the abatement of pollutants, different kinds of dyes, pesticides, and industrial wastewater samples. The sustainable, affordable, and waste to wealth-based MCCC with a simple synthesis methodology can be fruitfully applicable for environmental remediation and water decontamination.

2,4-Dichlorophenoxyacetic acid (2,4-D) adsorptive removal by algal magnetic activated carbon nanocomposite

In the present study, ferric oxide nanoparticles impregnated with activated carbon from Ulva prolifera biomass (UPAC-Fe₂O₃) were prepared and employed to remove 2,4-Dichlorophenoxyacetic acid (2,4-D) by adsorption. The UPAC-Fe₂O₃ nanocomposite was characterized for its structural and functional properties by a variety of techniques. The nanocomposite had a jagged, irregular surface with pores due to uneven scattering of Fe₂O₃ nanoparticles, whereas elemental analysis portrayed the incidence of carbon, oxygen, and iron. XRD analysis established the crystalline and amorphous planes corresponding to the iron oxide and carbon phase respectively. FT-IR analyzed the functional groups that confirmed the integration of Fe₂O₃ nanoparticles onto nanocomposite surfaces. VSM and XPS studies uncovered the superparamagnetic nature and presence of carbon and Fe₂O_3, respectively, in the UPAC-Fe₂O₃ nanocomposite. While the surface area was 292.51 m²/g, the size and volume of the pores were at 2.61 nm and 0.1906 cm³/g, respectively, indicating the mesoporous nature and suitability of the nanocomposites that could be used as adsorbents. Adsorptive removal of 2,4-D by nanocomposite for variations in process parameters like pH, dosage, agitation speed, adsorption time, and 2,4-D concentration was studied. The adsorption of 2,4-D by UPAC-Fe₂O₃ nanocomposite was monolayer chemisorption owing to Langmuir isotherm behavior along with a pseudo-second-order kinetic model. The maximum adsorption capacity and second order rate constant values were 60.61 mg/g and 0.0405 g/mg min respectively. Thermodynamic analysis revealed the spontaneous and feasible endothermic adsorption process. These findings confirm the suitability of the synthesized UPAC-Fe₂O₃ nanocomposite to be used as an adsorbent for toxic herbicide waste streams.

Adsorption of methylene blue by Nicandra physaloides(L.) Gaertn seed gum/graphene oxide aerogel

In this study, a novel composite aerogel of Nicandra physaloides(L.) Gaertn seed, gum/graphene oxide (NPG/GO), was prepared by using a vacuum freeze drying method for methylene blue (MB) adsorption. The techniques, including Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), were adopted for studying the structure and surface characteristics of NPG/GO, with thermogravimetric analysis (TGA) being adopted for testing thermal properties. The effects of pH value, initial dye concentration, temperature and adsorbent dosage on adsorption performance were elaborately analysed. The adsorption kinetic studies showed that the process of adsorption follows Langmuir isotherm and a pseudo-second-order kinetic model. When the mass ratio of NPG to GO was 1.25:1, the adsorption capacity was the highest. According to Langmuir isotherm, the maximum adsorption capacity of 408.16 mg/g was higher than that of NPG. The specific surface area and average pore diameter of NPG/GO was measured as 2.70 m²/g and 4.8 nm, respectively. Thermodynamic analysis revealed that the adsorption process of methylene blue on NPG/GO was a spontaneous and endothermic process. In general, the prepared nanocomposites were excellent candidates for adsorption and removal process because of simple synthesis, low cost, high efficiency, non-toxicity, environment protection and degradability.

A comparative study on adsorption behavior of iodinated X-ray contrast media iohexol and amidotrizoic acid by magnetic-activated carbon

As persistent and ubiquitous contaminants in water, iodinated X-ray contrast media (ICM) pose a non-negligible risk to the environment and human health. In this study, we investigated the adsorption behavior of two typical ICM compounds, iohexol (IOH) and amidotrizoic acid (DTZ), on magnetic activated carbon. Theoretical investigations, using density functional theory, identified the molecule structures and calculated the molecular diameters of IOH (1.68 nm) and DTZ (1.16 nm), which revealed that ICM could be adsorbed by mesopores and larger micropores. Therefore, magnetic activated carbon with a porous structure was prepared by the co-precipitation method to investigate the adsorption mechanism of IOH and DTZ. MAC--5 (magnetic activated carbon with a theoretical iron oxide content of 37%) showed the best adsorption ability for both IOH and DTZ, with maximum adsorption capacities of 86.05 and 43.00 mg g^-1, respectively. Adsorption kinetics and isotherm models were applied to explore the mechanisms involved, and the effects of solution pH, initial concentration, temperature, ionic strength, and natural organic matter were also investigated. The pore filling effect, π-π stacking, hydrogen bonding, and electrostatic interaction, were found to be the main adsorption mechanisms. The co-adsorption data showed that competition may occur in ICM coexisting environments. Interestingly, the used MAC--5 could be successfully regenerated and its adsorption efficiency did not decrease significantly after five cycles, indicating that it is a promising adsorbent for ICM. The results from this study provide some new insights for the treatment of water containing ICM.

Application of waste chalk/CoFe2O4/K2CO3 composite as a reclaimable catalyst for biodiesel generation from sunflower oil

This investigation aimed to produce a new composited catalyst from a waste chalk powder, a waste generated by the construction industry, to produce biodiesel from sunflower oil. The waste chalk was modified by CoFe₂O₄ nanoparticles and K₂CO₃. The surface tests showed that the obtained catalyst has been successfully synthesized with desired surface properties. The surface areas of waste chalk, waste chalk/CoFe₂O₄, and waste chalk/CoFe₂O₄/K₂CO₃ were determined 20.8, 77.8, and 5.8 m²/g, respectively. This indicates that the waste chalk/CoFe₂O₄/K₂CO₃ catalyst has a lower surface area due to K₂CO₃ being placed on the catalyst. Results showed the efficiency of RSM-CCD (R² = 0.992) compared to ANN (R² = 0.974). It was shown that a contact time of 180 min, a temperature of 65 °C, a waste chalk/CoFe₂O₄/K₂CO₃ mass of 2 wt%, and methanol to oil mole ratio of 15:1 gave the highest efficiency (98.87%) of biodiesel production at the laboratory conditions. The kinetic results of the process showed the energy of activation and frequency factor of 11.8 kJ/mol and 0.78 min^-1, respectively. Also, the values of ΔH°, ΔS°, and ΔG° at 65 °C was calculated to be 9010.7 J/mol, -256.3 J/mol and 95.7 kJ/mol, respectively, indicating that the biodiesel production process is endothermic requiring high energy for proceeding. The generated catalyst has an efficiency of over 90% up to 6 steps of reuse. The generated biodiesel was met most of the international standard levels.

Taguchi-based process optimization for activation of agro-food waste biochar and performance test for dye adsorption

The optimization of process parameters for biochar activation is crucial for enhancing its surface area and adsorptive potentials. This work attempts to investigate the influence of activating agent (e.g., steam and KOH), temperature (700-900 °C) and activation time (60-120 min) using Taguchi L₁₈ (2¹ × 3²) experimental design for the activation of biochar derived from food waste and agricultural crop residues such as canola hull and oat hull. Among all the factors, activating agent and temperature influenced surface area considerably. KOH-assisted chemical activation of biochar at 800 °C for 90 min was found to be optimal with higher specific surface areas of 1760, 1718 and 1334 m²/g for food waste, canola hull and oat hull derived biochar, respectively. Finally, the comparative evaluation of the performances of biochar and activated carbon samples was achieved through the adsorption of common dyes such as methylene blue, methyl violet and rhodamine B. Activated carbon samples derived from food waste biochar and canola hull biochar exhibited a complete removal of methylene blue and methyl violet from model aqueous solution within 1-2 h of contact time at room temperature, whereas in case of rhodamine B only 91-94% removal was achieved.

Synthesis of novel adsorbent by incorporation of plant extracts in amino-functionalized silica-coated magnetic nanomaterial for the removal of Zn2+and Cu2+from aqueous solution

Magnetic nanoparticles owing to their superparamagnetic behaviour and specific reactive sites are facilitated to regenerate and reuse. Our present study determines the cointegration of the plant extracts of Cynodon dactylon and Muraya koenigii with the magnetic nanoparticle coated with silica layer and surface engineered with a specific amine group. The cointegrated magnetic nano adsorbent is characterized for its analytical feature and batch studies are performed to remove zinc (Zn²⁺) copper (Cu²⁺) metal ions. Fourier transform infrared spectroscopy reveals the presence of functional entities such as NH₂, Si-O-Si, C=C. The size of the cointegrated nano adsorbent (12-30 nm) was confirmed by field emission scanning electron microscopy whereas, a high-resolution transmission electron microscope affirms the nanosize of the particle constituted around 20 nm. Energy dispersive x-ray analysis confirms the presence of elements like Fe, N, Si and was confirmed by X-ray diffraction analysis and vibrating sample magnetometer affirms the superparamagnetic nature with the high magnetic saturation value (M_s - 30 emug^-1). The cointegrated nano adsorbent reveals the maximum adsorption capacity of Zn²⁺ as 78.24 mg.g^-1 and Cu²⁺ as 81.76 mg.g^-1 of the adsorbent under the optimized conditions of contact time 45 min, pH 6.0 and temperature 35 °C. Kinetics such as pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion and isotherm studies like Langmuir, Freundlich, Dubinin-Radushkevich and Temkin were performed to understand the mechanism of interaction between the nanoadsorbent and metal ions. The reaction system follows the pseudo-second-order kinetics and Langmuir isotherm model for both the Cu²⁺ and Zn²⁺ metal ions. To determine the reusing capacity of the cointegrated nanoadsorbent, the adsorption efficiency was studied for continuous twelve cycles with 80% recovery after subsequent acid treatment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00696-9.

Preparation of clinoptilolite/starch/CoFe2O4 magnetic nanocomposite powder and its elimination properties for cationic dyes from water and wastewater

A new magnetic nanocomposite clinoptilolite (CLT)/Starch/CoFe₂O₄ was synthesized using co-precipitation method. The prepared magnetic composite powder was utilized for decontamination of methylene blue dye (MBD), methyl violet dye (MVD), and crystal violet dye (CVD) from water media. The BET analysis showed that CLT modification using starch and CoFe₂O₄ nanoparticles improved its specific surface and the amount of specific surface area for CLT, CoFe₂O_4, and CLT/Starch/CoFe₂O₄ powder was reported to be 18.82 m².g^-1, 151.4 m².g^-1, and 104.75 m².g^-1, respectively. Experimental results showed that pH 9 had a vital role in the adsorption process of all three types. Langmuir and Redlich-Petersen isotherm models were well fitted with experimental data. Also, the maximum adsorption capacity of CVD, MBD, and MVD to the desired composite was determined as 32.84 mg.g^-1, 31.81 mg.g^-1, and 31.15 mg.g^-1, respectively. In addition, the kinetic data of the removal process followed a pseudo-first order (PFO) kinetic model. Negative thermodynamic parameters were indicated that the process is spontaneous and exothermic. Finally, ad(de)sorption experiments' results showed that the synthesized nanocomposite adsorbent has an excellent ability to adsorb cationic dyes after several consecutive cycles.

Removal of malachite green and mixed dyes from aqueous and textile effluents using acclimatized and sonicated microalgal (Oscillatoria sp.) biosorbents and process optimization using the response surface methodology

Synthetic dyes are toxic and their release into the environment harms the ecosystem. Phycoremediation of synthetic dyes with acclimatized and native species has advantages over other methods. In this study, textile effluent-acclimatized microalgae species of Oscillatoria were grown in Bold's Basal Medium (BBM), dried, powdered using sonication, and optimized the removal malachite green (MG), using the response surface methodology (RSM). The effects of algal biosorbent concentration (AC), pH, and contact time (CT) were studied with 1 g L^-1 MG in an aqueous solution, and the interaction model exerted significance (p < 0.001). The removal of MG was higher at alkaline pH (90% at pH 8.5) than at acidic pH (70% at pH 4). Under the optimized conditions of 1.2 g L^-1 AC, 8.5 pH, and 30 min CT, the MG removal was documented at 90.8% with the biosorption capacity of 757 mg g^-1. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis revealed the occurrence of different electronegative functional groups, aromatic vibrations, and the crystalline nature of the biosorbent. The algal sorbent exhibited a good performance of 80.9% for the removal of the crude color in real textile effluents. This microalgal sorbent is an attractive option for promoting large-scale applications.

Facile preparation of taurine modified magnetic chitosan nanocomposites as biodegradable adsorbents toward methylene blue

A novel magnetic Fe₃O₄@chitosan@taurine adsorbent (MCT) was prepared by surface modification of magnetic chitosan nano-composites with taurine-glutaraldehyde solution. The adsorbents were characterized by FTIR, SEM, TEM, XRD, TGA and VSM techniques, respectively. According to the FTIR spectrum of MCT, the characteristic peaks of the SO₃^-group on MCT were observed to have a shift after adsorption of the cationic dye, which indicates that there may be electrostatic attraction between the MCT and the cationic dye. Moreover, the saturation magnetization of MCT was found to be 20.797 emu g^-1, suggesting that MCT has sufficient magnetic response to meet the need of magnetic separation. The adsorption properties of cationic dyes by MCT were further investigated by using methylene blue (MB) as a representative. The adsorption behaviour of MB by MCT was well described by the pseudo-second order kinetic model and the Langmuir isotherm model, respectively. The maximum adsorption capacity of MB calculated from the Langmuir model fitting was 204.1 mg g^-1 at pH 5 and 384.6 mg g^-1 at pH 9, respectively, and the adsorption equilibrium could be reached within 10 min. Besides, the negative values of ΔG° and ΔH° suggested that the adsorption process was spontaneous and exothermic, and the good reusability indicated that MCT could act as a recyclable adsorbent for dye adsorption. All of these results illustrate that MCT has great potential for practical application in removal of cationic dyes from aqueous solutions.

Progress and prospects of magnetic iron oxide nanoparticles in biomedical applications: A review

Nanoscience has been considered as one of the most substantial research in modern science. The utilization of nanoparticle (NP) materials provides numerous advantages in biomedical applications due to their unique properties. Among various types of nanoparticles, the magnetic nanoparticles (MNPs) of iron oxide possess intrinsic features, which have been efficiently exploited for biomedical purposes including drug delivery, magnetic resonance imaging, Magnetic-activated cell sorting, nanobiosensors, hyperthermia, and tissue engineering and regenerative medicine. The size and shape of nanostructures are the main factors affecting the physicochemical features of superparamagnetic iron oxide nanoparticles, which play an important role in the improvement of MNP properties, and can be controlled by appropriate synthesis strategies. On the other hand, the proper modification and functionalization of the surface of iron oxide nanoparticles have significant effects on the improvement of physicochemical and mechanical features, biocompatibility, stability, and surface activity of MNPs. This review focuses on popular methods of fabrication, beneficial surface coatings with regard to the main required features for their biomedical use, as well as new applications.

Phycoremediation of Synthetic Dyes: An Effective and Eco-Friendly Algal Technology for the Dye Abatement

Rapid industrialization leads to serious environmental hazards due to the increase in the release of pollutants into the environment. Industries that use synthetic dyes for different applications are a predominant source for dye contaminants by releasing the dye in wastewater with pretreatment or without treatment directly into the water bodies, making serious water pollution in the environment. Therefore, it is imperative to safeguard the environment from such contaminants and their associated negative impacts. The conventional treatment method that is used to treat dye-contaminated wastewater is generally costly and has a possibility to produce secondary metabolites. Due to the above problems, the biological method is preferable to treat effluent or dye-contaminated wastewater. Phycoremediation is an algae-based eco-friendly dye abatement technique from contaminated environments. This review highlights the phycoremediation of dyes and its underlying mechanisms along with the information on synthetic dyes, classification, hazardous effects, and other major techniques of dye abatement. This review provides a comprehensive insight into several influencing factors such as pH, temperature, contact time, the dose of algae biomass, and agitation speed, as well as functional groups involved in the phycoremediation process.

The removal of anionic and cationic dyes from an aqueous solution using biomass-based activated carbon

In this study, two biomass-based adsorbents were used as new precursors for optimizing synthesis conditions of a cost-effective powdered activated carbon (PAC). The PAC removed dyes from an aqueous solution using carbonization and activation by KOH, NaOH, and H₂SO₄. The optimum synthesis, activation temperature, time and impregnation ratio, removal rate, and uptake capacity were determined. The optimum PAC was analyzed and characterized using Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), a field emission scanning electron microscope (FESEM), Zeta potential, and Raman spectroscopy. Morphological studies showed single-layered planes with highly porous surfaces, especially PAC activated by NaOH and H₂SO₄. The results showed that the experimental data were well-fitted with a pseudo-second-order model. Based on Langmuir isotherm, the maximum adsorption capacity for removing methylene blue (MB) was 769.23 mg g⁻¹ and 458.43 mg g⁻¹ for congo red (CR). Based on the isotherm models, more than one mechanism was involved in the adsorption process, monolayer for the anionic dye and multilayer for the cationic dye. Elovich and intraparticle diffusion kinetic models showed that rubber seed shells (RSS) has higher α values with a greater tendency to adsorb dyes compared to rubber seed (RS). A thermodynamic study showed that both dyes’ adsorption process was spontaneous and exothermic due to the negative values of the enthalpy (ΔH) and Gibbs free energy (ΔG). The change in removal efficiency of adsorbent for regeneration study was observed in the seventh cycles, with a 3% decline in the CR and 2% decline in MB removal performance. This study showed that the presence of functional groups and active sites on the produced adsorbent (hydroxyl, alkoxy, carboxyl, and π − π) contributed to its considerable affinity for adsorption in dye removal. Therefore, the optimum PAC can serve as efficient and cost-effective adsorbents to remove dyes from industrial wastewater.

Unique Adsorption Properties of Malachite Green on Interlayer Space of Cu-Al and Cu-Al-SiW12O40 Layered Double Hydroxides

Cu-Al layered double hydroxide (LDH) was intercalated with Keggin ion of polyoxometalate           K4[a-SiW12O40] to form Cu-Al-SiW12O40 LDH. The obtained materials were analyzed by X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR) spectroscopy, and Brunaur-Emmett-Teller (BET) surface area analysis. Furthermore, the materials were used as adsorbents of malachite green from aqueous solution. Some variables for adsorption, such as: effect of adsorption times, malachite green concentration, and also adsorption temperature, were explored. The results showed that diffraction at 11.72° on Cu-Al LDH has interlayer distance of 7.56 Å. The intercalation of that LDH with [a-SiW12O40]4− ion resulted increasing interlayer distance to 12.10 Å. The surface area of material was also increased after intercalation from 46.2 m2/g to 89.02 m2/g. The adsorption of malachite green on Cu-Al and          Cu-Al-SiW12O40 LDHs followed pseudo second order kinetic and isotherm Langmuir model with adsorption capacity of Cu-Al and Cu-Al-SiW12O40 LDHs was 55.866 mg/g and 149.253 mg/g, respectively. That adsorption capacity is equal with increasing interlayer space and surface area properties of material after intercalation. Thus, the adsorption of malachite green on Cu-Al and Cu-Al-SiW12O40 LDHs is unique and dominantly occurred on interlayer space of LDH as active site adsorption. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Dye removal from water and wastewater by nanosized metal oxides - modified activated carbon: a review on recent researches

The conventional water and wastewater treatment methods are unable to provide up-to-data organized standards for drinking water and discharging effluents into natural ecosystems. Therefore, developing advanced and cost-effective methods to achieve published standards for water and wastewater and population needs are nowadays necessity. The important parts of this article are providing literature information about dyes and their effects on the environment and human health, adsorption properties and mechanism, adsorbent characteristics, and recent information on various aspects of modified activated carbons with nanosized metal oxides (AC- NMOs) in the removal of dyes. This review also summarized the effect of main environmental and operational parameters such as adsorbent dosage, pH, initial dye concentration, contact time, and temperature on the dye adsorption using AC-NMOs. Furthermore, the applied isotherm and kinetic models have been discussed.

Performance of photocatalytic ozonation process for pentachlorophenol (PCP) removal in aqueous solution using graphene-TiO2 nanocomposite (UV/G-TiO2/O3)

The aim of this study was to evaluate the efficiency of photocatalytic ozonation process using graphene-dioxide titanium nanocomposite in removing Pentachlorophenol (PCP) from aqueous solutions. In this study, nanocomposites with graphene to TiO2(G/T) ratios of 1:10 and 1:20 were synthesized by hydrothermal method, and its characteristics were assessed using various analyses, SEM, XRD, FTIR, TEM, BET and TGA. In this process, the effects of parameters including O3 concentration (0.25-1.25 mg/L), nanocomposite concentration (50-500 mg/L), initial PCP concentration (10-100 mg/L), and time (10-60 min), were studied. The results showed that PCP removal efficiency was increased by decreasing solute concentration. Increasing nanocomposite dose to 100 mg/L was led to an increase in efficiency (99.1%), but then a decreasing trend was observed. Increasing the concentration of ozone, up to specific value, also enhanced the efficiency but then had a negative effect on process efficiency. Furthermore, the optimum ratio of the catalyst was determined to be 1:20. The highest efficiency of the process for initial pentachlorophenol concentration of 100 mg/L was obtained 98.82% in optimum conditions (catalyst dose of 100 mg/L and 60 min). It is concluded that the photocatalytic ozonation process using graphene-dioxide titanium nanocomposite had the highest efficiency in removal and mineralization of PCP.

Modification of bio-hydroxyapatite generated from waste poultry bone with MgO for purifying methyl violet-laden liquids

In the present work, biological hydroxyapatite (Bio-HAp) was generated from waste poultry bone and modified with magnesium oxide (MgO) nanoparticles (Bio-HAp/MgO) and used in the adsorption process of methyl violet (MV). The Bio-HAp and Bio-HAp/MgO mesoporous composites were characterized using physicochemical techniques. Bio-HAp and Bio-HAp/MgO composites had crystalline and mesoporous structures. The specific surface area of Bio-HAp/MgO mesoporous composites (14.7 m²/g) was higher and lower than that of Bio-HAp (4.6 m²/g) and MgO (154.9 m²/g), respectively. The effect of pH (2-10), temperature (25-45 °C), contact time (10-50 min), initial MV concentration (5-25 mg/L), and Bio-HAp/MgO quantity (0.5-2.5 g/L) on the adsorption efficiency was optimized through response surface methodology-central composite design (RSM-CCD). Among four isotherm models, the Freundlich isotherm (R² > 0.98) was better matched with the equilibrium data. Based on the isotherm parameters (E, n, and R_L), the MV adsorption process using Bio-HAp particles and Bio-HAp/MgO mesoporous composites is physical and desirable. The pseudo-second-order (R² > 0.97) was more potent than the other models for modeling kinetic data. According to the thermodynamic investigation, the MV adsorption was an exothermic and spontaneous process. The mesoporous composite had good reusability to remove MV dye from liquid media up to 5 steps. Bio-HAp particles and Bio-HAp/MgO mesoporous composites were tested for treatment, which significantly reduced the dye content of the real sample.

Magnetic methacrylated gelatin-g-polyelectrolyte for methylene blue sorption

The presence of organic dyes in wastewater is a problem of growing interest due to its effect on the environment and human health. The aim of this work was to obtain magnetic hydrogels of methacrylated gelatin-g-polyelectrolyte to be used for the removal of methylene blue (MB) used as a model contaminant dye. Grafted gelatins with two degrees of functionalization (48% and 76%) were obtained and subsequently crosslinked using 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) and sodium 4-vinylbenzenesulfonate (SSNa) monomers. Magnetic nanoparticles were formed by an in situ precipitation method to easily remove the hydrogel from the adsorption medium. Our data show that the hydrogel with a low degree of methacrylation displayed a high degree of swelling and decreased stiffness due to its less connected polymer network. MB adsorption experiments showed that neither the low degree of methacrylation nor the presence of the aromatic group in the PSSNa polyelectrolyte generated an increase in the adsorption capacity of the hydrogel. However, a significant increase in the adsorption capacity was observed when dry hydrogels were combined compared to that of previously swollen hydrogel. The experimental data were non-linearly fitted to the pseudo-first and pseudo-second order models and in both cases, the highest q_e values were obtained for the GelMA-HF/PAMPS and GelMA-LF/PAMPS hydrogels. The Freundlich isotherm model was the one with the best correlation with the data (r² > 0.9700). Higher k_f values were obtained for the GelMA-HF/PAMPS and GelMA-LF/PAMPS hydrogels at 20 °C. The results obtained from this study demonstrated that magnetic polyelectrolyte-grafted gelatins are an efficient option for the removal of contaminant dyes from aqueous solutions.

Magnetic methacrylated gelatin grafted with anionic polyelectrolytes hydrogels removes methylene blue efficiently and easily separate with a magnet.

Role of phosphate concentration in control for phosphate removal and recovery by layered double hydroxides

Phosphorus removal from wastewater has become urgent because of eutrophication control. Phosphate concentration in control for phosphate removal and recovery by Mg-Fe oxide has been investigated. The results show that the adsorption capacity of phosphate by Mg-Fe oxide calcined at 450 °C was 28.3 mg/g, and it was kept at wide optimal adsorption pH ranges (4-10). The coexisting ions had influenced phosphate adsorption process and the order is CO₃^2- > SO₄^2- > NO₃^- > Cl^-, with the inhibition rate of CO₃^2- being 43%. Interestingly, phosphate concentration plays an important role in phosphate removal by Mg-Fe oxide. Under higher initial phosphate concentrations (200-800 mg/L), Sips model was well fitted. In addition, the adsorption kinetics was well described by the pseudo-second-order kinetic model before 25 min and the pseudo-first-order kinetic model after 25 min. In contrast, Langmuir model and pseudo-second-order kinetic model were fitted under lower initial phosphate concentrations (20-200 mg/L). The results of XRD, XPS, SEM, and TEM characterization show that Mg₃(PO₄)₂ was formed by surface precipitation under 800 mg/L phosphate solution, and Mg-Fe layered structure was present via the unique memory effect under 20 mg/L phosphate solution. Mg-Fe oxide can be recovered through CO₃^2- ion exchange, and the removal efficiency of phosphate was 56% after seven cycles.

The role of bentonite clay and bentonite clay@MnFe2O4 composite and their physico-chemical properties on the removal of Cr(III) and Cr(VI) from aqueous media

In this investigation, bentonite clay (BC) and bentonite clay@MnFe2O4 composite (BCMFC) were applied as efficient adsorbents for adsorbing Cr(III) and Cr(VI) ions from aqueous media. Different analyses such as FTIR, SEM, EDX, Map, BET, and XRD were used to characterize the adsorbents. The results showed that the removal efficiency of Cr(III) and Cr(VI) using BC were found to be 95.21 and 95.74%, while the corresponding values to the BCMFC were 97.37 and 98.65%, respectively. Also, the equilibrium and kinetic studies showed that the Freundlich isotherm model and the quasi-second-order kinetic model could better describe the equilibrium and kinetic behaviors of the adsorption process. The maximum adsorption capacity of the BC for the adsorption of Cr(III) and Cr(VI) ions were evaluated as 151.5 mg/g (25oC, pH 6, 90 min, and 1 g/L) and 161.3 mg/g (25oC, pH 3, 90 min, and 1 g/L), respectively, while the BCMFC showed the maximum capacities of 175.4 mg/g (25oC, pH 6, 60 min, and 1.5 g/L) and 178.6 mg/g (25oC, pH 3, 60 min, and 1.5 g/L) for Cr(III) and Cr(VI) ions, respectively, which were remarkable amounts. In addition, the thermodynamic study indicated that the adsorption process was physical, spontaneous, and exothermic. High removal efficiency, high chromium adsorption capacity, and low-cost magnetic adsorbent were significant features of the BCMFC for removal of Cr (III) and Cr (VI).

In Situ Synthesis of MIL-100(Fe) at the Surface of Fe3O4@AC as Highly Efficient Dye Adsorbing Nanocomposite

A new magnetic nanocomposite called MIL-100(Fe) @Fe3O4@AC was synthesized by the hydrothermal method as a stable adsorbent for the removal of Rhodamine B (RhB) dye from aqueous medium. In this work, in order to increase the carbon uptake capacity, magnetic carbon was first synthesized and then the Fe3O4 was used as the iron (III) supplier to synthesize MIL-100(Fe). The size of these nanocomposite is about 30-50 nm. Compared with activated charcoal (AC) and magnetic activated charcoal (Fe3O4@AC) nanoparticles, the surface area of MIL-100(Fe) @Fe3O4@AC were eminently increased while the magnetic property of this adsorbent was decreased. The surface area of AC, Fe3O4@AC, and MIL-100(Fe) @Fe3O4@AC was 121, 351, and 620 m2/g, respectively. The magnetic and thermal property, chemical structure, and morphology of the MIL-100(Fe) @Fe3O4@AC were considered by vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), zeta potential, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Brunner-Emmet-Teller (BET), and transmission electron microscopy (TEM) analyses. The relatively high adsorption capacity was obtained at about 769.23 mg/g compared to other adsorbents to eliminate RhB dye from the aqueous solution within 40 min. Studies of adsorption kinetics and isotherms showed that RhB adsorption conformed the Langmuir isotherm model and the pseudo second-order kinetic model. Thermodynamic amounts depicted that the RhB adsorption was spontaneous and exothermic process. In addition, the obtained nanocomposite exhibited good reusability after several cycles. All experimental results showed that MIL-100(Fe) @Fe3O4@AC could be a prospective sorbent for the treatment of dye wastewater.

Efficient arsenic(V) removal from contaminated water using natural clay and clay composite adsorbents

The natural clay is an abundant, accessible, and low-cost material that has the potential for use in the water and wastewater industry. In this paper, Iranian natural clay and clay/Fe-Mn composite were used to remove toxic arsenic from the liquid environment. The natural clay and clay/Fe-Mn composite were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX), X-ray diffractometry (XRD), thermo-gravimetric analysis (TGA), and atomic force microscopy (AFM) techniques. The effects of parameters (initial pH, temperature, sorption dose, and contact time) on the efficiency and behavior of the arsenic(V) adsorption process were studied. Freundlich (R² = 0.945 and 0.989), Langmuir (R² = 0.922 and 0.931), modified Langmuir (R² = 0.921 and 0.929), and Dubinin-Radushkevich (R² = 0.706 and 0.723) models were fitted to evaluate the equilibrium data of arsenic(V) adsorption process by natural clay and clay/Fe-Mn composite, respectively. The Langmuir adsorption capacity of arsenic(V) by the natural clay and clay/Fe-Mn composite was determined to be 86.86 mg/g and 120.70 mg/g, respectively. The arsenic(V) adsorption process followed the pseudo-second-order model. Negative values of ΔG° and ΔH° showed that the arsenic(V) sorption by the studied materials is thermodynamically spontaneous and exothermic. According to the findings, the natural clay and clay/Fe-Mn are suitable and recyclable sorbents for arsenic(V) adsorption from aqueous solutions. Also, the composite of clay with iron and manganese can improve the efficiency of clay in the removal of arsenic.