Methyl Orange Concentration Research Articles

Adsorption Process of Methyl Orange Dye onto Zinc Hydroxide Nitrate: Kinetic and Thermodynamic Studies

Zinc hydroxide nitrate (ZHN) was used as an anionic adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. ZHN was characterized via X-ray diffraction (XRD) and infrared spectroscopy (FTIR) techniques. Investigations were carried out to see how the adsorption of MO was affected by factors such as initial MO concentration, contact time and temperature. Adsorption isotherms were analyzed using the Langmuir and Freundlich equations, with the first one being the better result for the equilibrium data. Adsorption kinetics was studied through applying pseudo-first and pseudo-second-order kinetic models, and the experimental data were better fitted to the pseudo-second-order model. The activation energy was determined using the Arrhenius equation to be 105.45 kJ mol−1, revealing the chemical nature of the adsorption process. The thermodynamic parameters were also determined, showing the adsorption of MO onto ZHN to be a non-spontaneous and exothermic process. The experimental results showed ZHN as a potential adsorbent with adsorption capacity for removing anionic dyes from water medium.

Characterization of a Ti/SnO2-Sb/Fe-PVP-PbO2 Electrode Deposited from Methanesulfonate Bath and Application in Electrocatalytic Degradation of MO

Ti/SnO2-Sb/PbO2 anodes were electrodeposited from methanesulfonate-based baths, and the effect of dopants such as PVP and Fe on the surface morphology, phase composition, electrocatalytic activity and stability was investigated. It is revealed that the inclusion of Fe effectively enhances the stability of PbO2 anode, while PVP can significantly improve its electrocatalytic activity. The Fe,PVP-codoped anode, Ti/SnO2-Sb/Fe-PVP-PbO2, exhibits the higher stability and electrocatalytic activity compared to the respective inclusion of Fe and PVP. The gradation efficiency of methyl orange (MO) on the Ti/SnO2-Sb/Fe-PVP-PbO2 anode is affected by the applied current density and the initial MO concentration. During degradation, the azo structure of MO is firstly cleaved, resulting in the rapid decolorization of solution. Demethylated MO and the anion of sulfanilic acid are detected as intermediates, and thus a plausible pathway of MO degradation is proposed.

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.

Controlling the Surface Morphology of Two-Dimensional Nano-Materials upon Molecule-Mediated Crystal Growth.

The surface morphology of Mg-Al-layered double hydroxide (LDH) was successfully controlled by reconstruction during systematic phase transformation from calcined LDH, which is referred to as layered double oxide (LDO). The LDH reconstructed its original phase by the hydration of LDO with expanded basal spacing when reacted with water, including carbonate or methyl orange molecules. During the reaction, the degree of crystal growth along the ab-plane and stacking along the c-axis was significantly influenced by the molecular size and the reaction conditions. The lower concentration of carbonate gave smaller particles on the surface of larger LDO (2000 nm), while the higher concentration induced a sand-rose structure. The reconstruction of smaller-sized LDH (350 nm) did not depend on the concentration of carbonate due to effective adsorption, and it gave a sand-rose structure and exfoliated the LDH layers. The higher the concentration of methyl orange and the longer the reaction time applied, the rougher the surface was obtained with a certain threshold point of the methyl orange concentration. The surface roughness generally increased with the loading mount of methyl orange. However, the degree of the surface roughness even increased after the methyl orange loading reached equilibrium. The result suggested that the surface roughening was mediated by not only the incorporation of guest molecules into the LDH but also a crystal arrangement after a sufficient amount of methyl orange was accommodated.

Rice husk charcoal and acid modified rice husk charcoal for efficient adsorption of methyl orange

Abstract In this study, methyl orange (MO) was removed from solution using rice husk charcoal (RHC) and acid modified rice husk charcoal (AMRHC). In batch adsorption mode, contact time (1–240 min), pH (3–10), adsorbent dose (1–30 g/L), and initial MO concentration (10–100 mg/L) were investigated. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the adsorbent's surface morphology and chemistry. At equilibrium, the highest removal of MO by RHC and AMRHC were 89 and 99%, respectively. Removal efficiency increased with increasing adsorbent dose, while the opposite was observed for adsorption capacity because of the availability of unsaturated adsorption sites. RHC and AMRHC were best described by the Freundlich and Langmuir isotherm models, with maximum adsorption capacities of 4.57 and 11.53 mg/g, respectively. The pseudo-second-order kinetic model fitted well for both adsorption and chemisorption, and the process was controlled by multi-step diffusion. Thermodynamic measurements proved that dye adsorption is a spontaneous endothermic process.

Microwave assisted zirconium oxide based catalytic activation of persulfate for methyl orange dye degradation

In this investigation, zirconium oxide (ZrO2) based activation of persulfate (PS) under microwave (MW) irradiation for methyl orange (MO) dye degradation was studied. ZrO2 was synthesized using facile hydrothermal method and it was characterized via XRD, FTIR, SEM, and TGA techniques. Subsequently, MW/ZrO2/PS experiments were conducted to explore the effect of ZrO2 dosage (0–1.5 g/L), initial MO concentration (15–250 mg/L), MW reactor temperature (60–90 ℃), MW power (240–700 W), PS dosage (50–250 mg/L), and presence of NaCl (0–5000 mg/L) on MO removal at pH ~ 7. Under the optimal conditions (ZrO2 ~ 0.5 g/L, MO concentration ~ 25 mg/L, MW temperature ~ 90 ℃, MW power ~ 560 W, and PS dose~250 mg/L), 99 % of MO removal and 85.9 % of TOC removal were observed. Moreover, the toxicity of the initial sample was reduced by 72.9 %. Interestingly, the catalytic oxidation of MO was not affected due to the presence of NaCl. Radical studies confirmed that SO4−⦁ radical was the major active species responsible for MO degradation. Subsequently, the central composite design (CCD) approach was used to find out the interaction effects between MO concentration (10–250 mg/L), PS dosage (50–500 mg/L), and MW treatment time (5–20 min) on MO removal. The CCD based response surface model was found to be significant and reliable (p < 0.0001). Moreover, the chemical cost and energy cost for MW/ZrO2/PS experiments under optimized condition was estimated as $22.5 and $30.3 per kg of MO removal. Overall, transition metal-based PS activation under MW irradiation could be one of the potential alternatives for dye wastewater treatment.

Polymeric Floating Photocatalysts Based on PE/TiO2 Composites for the Removal of Organic Pollutants in Water

Polymeric floating photocatalysts based on polyethylene (PE)/TiO2 compositions were synthesized by in situ ethylene polymerization in the presence of a titanium–magnesium catalyst synthesized by the sequential deposition of a magnesium–aluminum complex and TiCl4 on commercial TiO2 P25. The optical band gap of the synthesized PE/TiO2 composites was shown to be 3.1–3.3 eV, which allowed for their use as photocatalysts for the utilization of solar light. The photocatalytic activity of the PE/TiO2 composites was studied for the degradation of methyl orange (MO) under irradiation with UV light (λmax = 384 nm). The composites containing 20–50 wt.% of PE were found to have an optimum combination between floatability and photocatalytic activity. The maximum photodegradation rate was observed at an MO concentration below 5 ppm. The polymeric PE/TiO2 floating photocatalysts could be used repeatedly, but the long-term exposure of the composites to UV radiation was accompanied by oxidation of the polymer.

Removal of hazardous textile dye from simulated wastewater by municipal organic solid waste charcoal using machine learning approaches: Kinetics, isotherm, and thermodynamics

This study focuses on the probable use of municipal organic solid waste charcoal (MOSWC) as an adsorbent for Methyl orange (MO) adsorption. The prepared MOSWC is characterized by FE-SEM and FT-IR. Batch adsorption experiments were conducted with the influencing of different operational conditions namely time of contact (1–180 min), adsorbate concentration (60–140 mg/L), adsorbent dose (1–5 g/L), pH (3–11), and temperature (25–60 °C). The high coefficient value (R2 = 0.96) of the process optimization model suggests that this model was significant, where pH and adsorbent dose expressively stimulus adsorption efficiency including 40.11 mg/g at pH (3), MO concentration (100 mg/L), and MOSWC dose (1 g/L). Furthermore, the machine learning approaches (ANN and BB-RSM) revealed a good association between the tested and projected values. The highest monolayer adsorption capacity of MO was 90.909 mg/g. Pseudo-second-order was the well-suited kinetics, where Langmuir isotherm could explain better for equilibrium adsorption data. Thermodynamic study shows MO adsorption is favourable, exothermic, and spontaneous. Finally, this study indicates that MOSWC could be a potential candidate for the adsorption of MO from wastewater.

Adsorption of methyl orange by porous membranes prepared from deep eutectic supramolecular polymer-modified chitosan

The fabrication of an adsorbent with excellent performance has been a focus of attention because of the toxicity, mutagenicity and carcinogenicity of methyl orange (MO)-containing wastewater discharged from the textile, tannery and pharmaceutical industries. In this study, chitosan (CS) membranes were modified with a deep eutectic supramolecular polymer (DESP), and adsorbent membranes with porous structures were prepared with polyethylene glycol (PEG). Microstructural characterization of the CS-DESP-PEG composite membranes with FT-IR, XRD and SEM showed that the membranes had amorphous crystalline structures and that hydrogen bonding interactions weakened the crystallinity and formed loose porous structures. Optimization of the chitosan to β-cyclodextrin ratio, pH, PEG proportion, MO concentration and adsorbent dose significantly improved the adsorption efficiencies of the membranes. The adsorption behaviours of the membranes were fit with pseudo-second-order adsorption kinetics and the Freundlich adsorption isotherm model. Regeneration experiments showed that the membranes were reusable multiple times and maintained good adsorption capacities.

The role of tin species in doped iron (III) oxide for photocatalytic degradation of methyl orange dye under UV light

Iron (III) oxide, a stable semiconductor with versatile applications, was synthesized alongside Sn-doped Fe2O3 (Sn–Fe2O3) using the sol-gel technique. Characterization via X-ray diffraction, field-emission scanning electron microscopy, and UV–visible spectroscopy confirmed the presence of α- and γ-Fe2O3 phases in the synthesized powders. Incorporation of the dopant reduced the initial band gap energy of Fe2O3 (2.2 eV) by approximately 0.1 eV. To evaluate photocatalytic performance, Fe2O3 and Sn–Fe2O3 were tested for decolorization efficiency of a methyl orange solution. Results revealed the 5 wt% Sn-doped catalyst as optimal, achieving complete degradation of methyl orange within 120 min under simulated solar light. The addition of small amounts of Sn effectively reduced the Fe2O3 band gap and significantly enhanced photocatalytic performance. Investigation of pH and dye concentration impact on photocatalytic degradation revealed superior activity under acidic conditions compared to alkaline. Furthermore, maintaining a moderate concentration of methyl orange (10 ppm) ensured optimum photocatalytic activity.

A new 2D Zn(II)-based coordination polymer as photocatalyst for photodegradation of methyl orange in water: Effect of photocatalyst dosage and dye concentration

The metal-organic frameworks (MOFs) a sub-class of well-known coordination polymer are assorted multidimensional materials that could be employed as photocatalysts for dye decomposition present in the wastewater discharge. Herein, a new Zn(II)-based coordination polymer with formula [Zn(bpyp)(5-nip)] (1) (bpyp = 2,5-bis(pyrid-4-yl)pyridine and H2nip= 5-nitroisophthalic acid) has been synthesized and characterized. In 1, the two carboxyl groups of each 5-nip2− ligand adopts μ2-η1:η1 and μ1-η1:η1 coordination fashion to connect ZnII centers into a 1D chain along b direction, which alternately contains 8-membered rings and 16-membered rings. The newly synthesized compounds have been used as the photocatalyst for the photodegradation of methyl blue (MB), methyl orange (MO), rhodamine B (RhB) and methyl violet (MV) dyes under UV light irradiation. The results reveal that amongst all four dyes, 1 decomposes MO dye to maximum extent. The effects of concentration of dyes, and photocatalyst dosages have been monitored on the photocatalytic performance of 1. Under the optimal reaction condition, ∼89.03% photodegradation of MO has been observed at 20 ppm concentration of MO and 20 mg photocatalyst concentration in 50 min time span. The radical trapping experiments suggest that O2·− is the main active species that catalyzes the photodecomposition of dyes. The possible mechanism for the MO degradation of 1 is proposed using density of states (DOS) calculations and Hirshfeld surface analysis.

Biowaste-derived Ni/NiO decorated-2D biochar for adsorption of methyl orange

Eco-friendly carbothermal techniques were used to synthesize nanocomposites of biowaste-derived Ni/NiO decorated-2D biochar. The use of chitosan and NiCl2 in the carbothermal reduction technique was a novelty to synthesize the Ni/NiO decorated-2D biochar composite. Potassium persulfate (PS) was found to be activated by Ni/NiO decorated-2D biochar, which is thought to oxidize organic pollutants through an electron pathway designed by the reactive complexes formed between PS and the Ni/NiO biochar surface. This activation led to the efficient oxidation of methyl orange and organic pollutants. Analyzing Ni/NiO decorated-2D biochar composite before and after the methyl orange adsorption and degradation procedure allowed us to report on the process of its elimination. The Ni/NiO biochar with PS activation showed higher efficiency than Ni/NiO decorated-2D biochar composite as this material was able to degrade over 99% of the methyl orange dye. The effects of initial methyl orange concentration, dosages effect, solution pH, equilibrium studies, kinetics, thermodynamic studies, and reusability were examined and evaluated on Ni/NiO biochar.

Effect of Ag doping on photocatalytic activity of ZnO-Al2O3 derived from LDH structure: Synthesis, characterization and experimental study

In this research, Ag-ZnO-Al2O3 heterostructure catalyst was derived from the calcination of Ag-doped layered double hydroxide (LDH) through a solid-state process. With the aim of entirely understanding the structural and functional features, catalysts were analyzed by XRD, TGA/DTA, and FTIR techniques. The photocatalytic performance was evaluated by measuring the methyl orange (MO) photodegradation under UV irradiation. The impact of the key parameters, namely, irradiation time, catalyst dose, initial pH of solution, and the starting concentration of MO, were investigated and discussed. The characterization results exhibit a well crystallized hexagonal LDH structure. The experimental findings revealed approximately 95.8 % degradation yield after 210 min of irradiation for Ag-ZnO-Al2O3. The optimal conditions were found to be 20 mg/L of catalyst dose, 20 mg/L of MO initial concentration and initial pH of 4. In the whole, the results confirm that the Ag-ZnO-Al2O3 catalyst shows the highest adsorption and photocatalytic performances. After three recycling tests, the Ag-ZnO-Al2O3 photocatalyst maintained good recycling stability and a high photodegradation performance (90.7%). Finally, the use of Ag-ZnO-Al2O3 as heterostructure photocatalyst offer a promising approach for the degradation of more organic compounds in environmental remediation.

Synthesis of cuprous oxide/silver (Cu2O/Ag) hybrid as surface-enhanced Raman scattering probe for trace determination of methyl orange.

Recently, there have been publications on preparing hybrid materials between noble metal and semiconductor for applications in surface-enhanced Raman scattering (SERS) substrates to detect some toxic organic dyes. However, the use of cuprous oxide/silver (Cu2O/Ag) to measure the trace amounts of methyl orange (MO) has not been reported. Therefore, in this study, the trace level of MO in water solvent was determined using a SERS substrate based on Cu2O microcubes combined with silver nanoparticles (Ag NPs). Herein, a series of Cu2O/Agx ( 1-5) hybrids with various Ag amounts was synthesized via a solvothermal method followed by a reduction process, and their SERS performance was studied in detail. X-ray diffraction (XRD) and scanning electron microscopy results confirmed that 10 nm Ag NPs were well dispersed on 200-500 nm Cu2O microcubes to form Cu2O/Ag heterojunctions. Using the as-prepared Cu2O and Cu2O/Agx as MO probe, the Cu2O/Ag5 nanocomposite showed the highest SERS activity of all samples with the limit of detection as low to 1 nM and the enhancement factor as high as 4 × 108. The logarithm of the SERS peak intensity at 1389 cm-1 increased linearly with the logarithm of the concentration of MO in the range from 1 nM to 0.1 mM.

Adsorption Kinetics of Methyl Orange from Model Polluted Water onto N-Doped Activated Carbons Prepared from N-Containing Polymers.

This study aimed to assess the role of polymeric sources (polypyrrole, polyaniline, and their copolymer) of nitrogen (N)-doped activated carbons (indexed as PAnAC, PPyAC, and PnyAC, respectively) on their adsorption efficiency to remove methyl orange (MO) as a model cationic dye. The adsorbents were characterized using FTIR, SEM, TGA, elemental analysis, and surface area. The kinetic experiments were performed in batches at different MO concentrations (C0) and adsorbent dosages. The adsorption kinetic profiles of pseudo-first-order, pseudo-second-order (PSO), Elovich, intraparticle diffusion, and liquid film diffusion models were compared. The results showed a better fit to the PSO model, suggesting a chemisorption process. The adsorption capacity (qe, mg/g) was found to have increased as MO C0 increased, yet decreased as the adsorbent quantity increased. At the adsorption operating condition, including MO C0 (200 ppm) and adsorbent dose (40 mg), the calculated qe values were in the order of PAnAC (405 mg/g) > PPyAC (204 mg/g) > PnyAC (182 mg/g). This trend proved the carbon precursor's importance in the final properties of the intended carbons; elemental analysis confirmed that the more nitrogen atoms are in the activated carbon, the greater the number of active sites in the adsorbent for accommodating adsorbates. The diffusion mechanism also assumed a rate-limiting step controlled by the film and intraparticle diffusion. Therefore, such an efficient performance may support the target route's usefulness in converting nitrogenous-species waste into valuable materials.

Extraction and Determination of Sildenafil Citrate by Spectrophotometry: Classical Versus Factorial Design Optimization

In this work, the complexation and extraction processes of sildenafil citrate (SC) were evaluated by using classical optimization versus factorial design methodology. The selected factors were based on the reaction of sildenafil with methyl orange (MO) as a chromogenic reagent via the formation of ion-association complex in acidic buffer media, followed by extraction with chloroform and quantitatively measured by visible spectrophotometry at λmax of 427 nm. The optimization step was first carried out by classical one-factor-at-a-time (OFAT) from which the extracted results were exploited in the experimental design optimization by using 24-1 fractional factorial and 32 full factorial designs for the chosen variables such as pH, concentration of reagent, reaction time, extraction time and temperature. Results obtained from fractional factorial design 24-1 showed that only the variables pH, MO concentration and their interaction based on analysis of variance (ANOVA) in term of Pareto chart, were statistically significant at 95% confidence level. Under the optimized conditions, the assay method of SC was validated in term of the analytical figures of merit. SC can be determined in concentration range of 0.5-40 µg mL-1 with correlation coefficient of 0.9991, detection limit (S/N) of 0.15 µg mL-1, RSD (n=10) of 1.43%, accuracy as %Erel of -2.23% and mean percent recovery of 97.77±0.87. The proposed method was applied for the determination of SC in commercial medicaments without fear from excipients interferences with the assay procedure.

Statistical physics double-layer models for the experimental study and theoretical modeling of methyl orange dye adsorption on AlMnTiO nanocomposite

A Al2O3/MnO2/TiO2 (AlMnTiO) nanocomposite was synthesized using the thermal coprecipitation method and the adsorption performance of methyl orange (MO) dye from aqueous solution was carried out. Single-parameter optimization was used to explore the properties of AlMnTiO nanocomposite parameters on dye adsorption, including dose of adsorbent, solution pH, contact duration, and starting MO concentration. The model is the appropriate adsorption isotherm for the equilibrium process using a pseudo-second-order kinetic model property. Langmuir plot had a Q max (mg/g) of 198.4 and best fitted (R 2=0.990) among different isotherm models. The relevant parameters were computed using the dual-energy binary-layer statistical physics model. The statistical physics binary-layer model yield n (stoichiometric coefficient) values of 0.410, 0.440, and 0.453, all values are below 1, demonstrating the multi-docking process. AlMnTiO nanocomposite was regenerated up to six times, making the material extremely cost-effective. Using AlMnTiO nanocomposite, MO dye was removed from wastewater both in the laboratory and on the industrial scale.

Facile fabrication of graphitic carbon nitride by solvothermal method with hierarchical structure and high visible light photocatalytic activity

BackgroundAt present, graphitic carbon nitride(g-C3N4) has been tremendously investigated as a visible light photocatalyst due to its excellent physical and chemical stability, easy fabrication, diverse morphology and tunable band structure. However, small surface area and high recombination of photogenerated electron-hole pairs hinder the photocatalytic activity of the pristine g-C3N4. Up to now, most of the g-C3N4 is prepared by the time-consuming, cumbersome and energy-consuming methods such as template and high temperature calcination. MethodsA novel graphitic carbon nitride with hierarchical structure and high photocatalytic activity was first time synthesized by the solvothermal method without high-temperature calcination using two monomers (cyanuric chloride and melamine) as the reactants. Morphologies and structure of graphitic carbon nitride were characterized by FTIR, XRD, XPS, FESEM, BET, etc. Effects of monomer molar ratio on the microstructure, band structure and electron transfer process of the samples were systematically investigated. The radical trapping experiments and Mott-Schottky analysis were carried out to reveal the photocatalytic degradation mechanism. Significant findingsDue to the high activity of Cl group of cyanuric chloride, HCl generated by condensation dramatically influences the formation of the porous structure. With the increase of cyanuric chloride molar ratio, polymerization reaction between cyanuric chloride and melamine became more complete, structure of graphite carbon nitride gradually changed from 1D nanorods to 2D layered structures, and the band structure and electron transfer properties were effectively improved. Due to the synergistic effect of specific surface area and electron transfer performance, 2-CN-1 with microporous 1D and 2D structures showed excellent photocatalytic performance (96.5% after 30 min illumination) and stability (photocatalytic performance only decreased by 4.5% after five cycles) in the condition of methyl orange (MO) concentration as high as 20 mg/L and photocatalyst amount as low as 20 mg. In this study, the effective control of graphitic carbon nitride morphology by way of new condensation mode via solvothermal method without both template and high temperature calcination provides a new strategy for the graphitic carbon nitride with high visible light photocatalytic activity.

Adsorption of Methyl Orange Dyes on Oriented Co/Fe-MOF Bimetallic Organic Framework in Wastewater Treatment

The production of highly efficient and reusable adsorbents that can be used in pigment treatment has been of great scientific interest. Metallic organic frameworks (MOFs) are considered a new type of material with extremely diverse structures and can be used as adsorbents to remove environmental pollutants. The selected Co/Fe-MOF material was synthesized in this study by using the solvent-thermal method. Then, the effects of several influencing factors such as adsorbent dosage, pH, initial concentration of MO, and exposure time on the adsorption capacity of methyl orange (MO) dyes by Co/Fe-MOF were evaluated. Under acidic conditions (pH 4), the effective removal of MO from aqueous solution reached equilibrium after 60 min upon exposure to MO at the concentration of 200 mg/L, and the adsorption capacity was 137.6 mg/g. The two models of adsorption isotherms, Freundlich and Langmuir, showed good compatibility with the experimental data, and the calculated correlation coefficients (R2) were both greater than 0.96. The MO adsorption efficiency was proposed to fit the pseudo-quadratic and pseudo-first-order kinetic models. Therefore, MOF materials can be considered as a potential agent for wastewater treatment, thereby providing a possible solution to solve water pollution.

Recyclable Magnetic Iron Immobilized onto Chitosan with Bridging Cu Ion for the Enhanced Adsorption of Methyl Orange.

Chitosan (CS) is a natural and low-cost adsorbent for capturing metal ions and organic compounds. However, the high solubility of CS in acidic solution would make it difficult to recycle the adsorbent from the liquid phase. In this study, the CS/Fe3O4 was prepared via Fe3O4 nanoparticles immobilized onto a CS surface, and the DCS/Fe3O4-Cu was further fabricated after surface modification and the adsorption of Cu ions. The meticulously tailored material displayed the sub-micron size of an agglomerated structure with numerous magnetic Fe3O4 nanoparticles. During the adsorption of methyl orange (MO), the DCS/Fe3O4-Cu delivered a superior removal efficiency of 96.4% at 40 min, which is more than twice the removal efficiency of 38.7% for pristine CS/Fe3O4. At an initial MO concentration of 100 mg L-1, the DCS/Fe3O4-Cu exhibited the maximum adsorption capacity of 144.60 mg g-1. The experimental data were well explained by the pseudo-second-order model and Langmuir isotherm, suggesting the dominant monolayer adsorption. The composite adsorbent still maintained a large removal rate of 93.5% after five regeneration cycles. This work develops an effective strategy to simultaneously achieve high adsorption performance and convenient recyclability for wastewater treatment.