Biocompatible G-Fe3O4/CA nanocomposites for the removal of Methylene Blue

A graphene oxide based composite granule for methylene blue separation from aqueous solution: Adsorption, kinetics and thermodynamic studies

Graphene oxide and chitosan composite material using as a high-efficiency and low-cost granular adsorbent for methylene blue removal was fabricated via self-assembling method. The effects of pH value, contact time, initial concentration, adsorbent dose, temperature, and recyclic stability on the adsorption performance of methylene blue in aqueous solution were investigated in detail. Desorption process with the effects of solvents, contact time, and temperature were also conducted carefully in this study. The adsorption kinetics and adsorption isotherm of dye adsorption process showed that dye adsorption process was fitted to the pseudo-second-order kinetic model and the Freundlich adsorption isotherm, indicating a physical adsorption process with multilayer adsorption. The intra-particle diffusion model indicated that the dye adsorption by the granular adsorbent was strongly happened during the first 4 h. The thermodynamic study showed that the adsorption was a spontaneous and exothermic process and dye ions were condensed onto the surface of adsorbent. The maximum adsorption capacity of dye on the granular adsorbent was calculated as 951.35 mg/g and the adsorbent could maintain its adsorption performance after six cycles. In general, this study provided an efficient, cost-effective, and recyclable the granular adsorbent for dye separation from aqueous solution.

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.

Fenton degradation of ofloxacin antibiotic using calcium alginate beads impregnated with Fe3O4-montmorillonite composite

The primary aim of this study is to develop an economical, stable, and effective heterogeneous catalyst for wastewater remediation via the Fenton oxidation process. For this purpose, Fe₃O₄-montmorillonite alginate (FeMA) composite beads were synthesized by entrapping Fe₃O₄-montmorillonite in calcium alginate beads. The performance of the catalysts was evaluated via the Fenton degradation of ofloxacin (OFL), an antibiotic that is frequently detected in water bodies. The physiochemical properties of the FeMA composite beads were characterized using X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope/energy dispersive X-ray (FESEM/EDX), Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). FeMA composite beads were found to have a higher surface area, higher porosity, and better thermal stability compared to pristine alginate beads. The composite beads were subsequently used for Fenton degradation of ofloxacin (OFL) in an aqueous solution. The effects of Fe₃O₄-montmorillonite loading on alginate, FeMA composite beads dosage, initial solution pH, initial OFL concentration, different oxidants, H₂O₂ dosage, reaction temperature, and inorganic salts on Fenton degradation of OFL in aqueous solution was investigated. The results revealed that the percentage of OFL degradation reached about 80 % under optimized conditions, while the total organic carbon (TOC) removal reached about 53 %. The entrapment of Fe₃O₄-montmorillonite in alginate beads results in less iron ions leaching compared to previous observation, and the efficiency remains constant over the five cycles investigated. The kinetics of the Fenton degradation process are best fitted to the pseudo-first-order kinetic model. It is therefore believed that FeMA composite beads can be a promising material for wastewater remediation via the Fenton oxidation process.

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

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

Environmentally Friendly Polyvinyl Alcohol-Alginate/Bentonite Semi-Interpenetrating Polymer Network Nanocomposite Hydrogel Beads as an Efficient Adsorbent for the Removal of Methylene Blue from Aqueous Solution

Hazardous chemicals like toxic organic dyes are very harmful to the environment and their removal is quite challenging. Therefore there is a necessity to develop techniques, which are environment friendly, cost-effective and easily available in nature for water purification and remediation. The present research work is focused on the development` and characterization of the ecofriendly semi-interpenetrating polymer network (semi-IPN) nanocomposite hydrogels composed of polyvinyl alcohol (PVA) and alginate (Alg) hydrogel beads incorporating natural bentonite (Bent) clay as a beneficial adsorbent for the removal of toxic methylene blue (MB) from aqueous solution. PVA-Alg/Bent nanocomposite hydrogel beads with different Bent content (0, 10, 20, and 30 wt%) were synthesized via external ionic gelation method. The designed porous and steady structure beads were characterized by the use of Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The performance of the beads as MB adsorbents was investigated by treating aqueous solutions in batch mode. The experimental results indicated that the incorporation of Bent (30 wt%) in the nanocomposite formulation sustained the porous structure, preserved water uptake, and increased MB removal efficiency by 230% compared to empty beads. Designed beads possessed higher affinity to MB at high pH 8, 30 °C, and fitted well to pseudo-second-order kinetic model with a high correlation coefficient. Moreover, the designed beads had good stability and reusability as they exhibited excellent removal efficiency (90%) after six consecutive adsorption-desorption cycles. The adsorption process was found be combination of both monolayer adsorption on homogeneous surface and multilayer adsorption on heterogeneous surface. The maximum adsorption capacity of the designed beads system as calculated by Langmuir isotherm was found to be 51.34 mg/g, which is in good agreement with the reported clay-related adsorbents. The designed semi-IPN PVA-Alg/Bent nanocomposite hydrogel beads demonstrated good adsorbent properties and could be potentially used for MB removal from polluted water.

Study on the Adsorption Performance of Casein/Graphene Oxide Aerogel for Methylene Blue

Casein (CS) and graphene oxide (GO) were employed for the fabrication of a casein/graphene oxide (CS/GO) aerogel by vacuum freeze drying. Fourier transform infrared spectroscopy, scanning electron microscopy, surface area and micropore analysis (BET), and thermogravimetric analysis were used to characterize the specific surface area, structure, thermal stability, and morphology of the CS/GO aerogel. The influence of experimental parameters such as the GO mass fraction in the aerogel, metering of the adsorbent, pH, contact time, and temperature on the adsorption capacity of the CS/GO aerogel on methylene blue (MB) was also investigated. According to Langmuir isotherm determination, the maximum removal rate of MB from the CS/GO aerogel was 437.29 mg/g when the temperature was 293 K and pH was 8. Through kinetic and thermodynamic studies, it is found that adsorption follows a pseudo-second-order reaction model and is also an exothermic and spontaneous process.

A novel Fe3+-stabilized magnetic polydopamine composite for enhanced selective adsorption and separation of Methylene blue from complex wastewater

Herein, a novel Fe³⁺-stabilized magnetic polydopamine composite (Fe₃O₄/PDA-Fe³⁺) was facilely constructed, systematically characterized, and subsequently applied for the first time as a versatile adsorbent for treatment of Methylene blue (MB) in complex wastewater. Results showed that as-prepared material had prominent adsorption ability toward MB in its single dye solution over a wide pH range (3-10) with q_max value of 608.8 mg/g at 318 K. More interestingly, MB could be selectively captured by resulting adsorbent from mixed dye solutions (MB-cationic dye and MB-anionic dye) and complex aqueous solution with high ionic strength up to 0.5 mol/L NaCl. It was eventually revealed that the enhanced and selective adsorption of MB by as-resultant adsorbent was due to the synergistic effects between multiple uptake mechanisms. What's more, its adsorption efficiency toward MB in simulated wastewater still maintained higher than 80 % of its original uptake performance after several runs of adsorption-desorption. Additionally, it exhibited more superior uptake performance toward MB than commercial powder activated carbon (PAC) in column adsorption system. Thus, the outstanding sorption ability, unique capture selectivity, as well as excellent stability and recyclability for model wastewater endow it a promising candidate adsorbent for selective adsorption and separation of MB from complex wastewater.

One-step generation of S and N co-doped reduced graphene oxide for high-efficiency adsorption towards methylene blue

S and N co-doped reduced graphene (S–N-rGO) nanohybrids were prepared by a one-step oil bath heating process using glutathione (GSH) as a green and mild co-reduction agent and a S and N source. It can be applied in the field of adsorption for the removal of methylene blue (MB) from aqueous solutions. The efficient adsorption rate of S–N-rGO hybrids for MB (50 mg L⁻¹) was observed with the best even within 2′07′′ from blue solutions into colorless (the mass ratio GO : GSH = 60 : 200). Under this mass ratio, the effects of initial solution pH, temperature, initial concentration and contact time on adsorption towards MB were explored systematically. The results indicated that the adsorption capacity at 275 K could reach up to 598.8 mg g⁻¹, the adsorption behavior followed the pseudo-second-order kinetic model and the equilibrium adsorption data fitted the Langmuir isotherm well. Thermodynamic and kinetic analyses revealed that adsorption is an exothermic, spontaneous and physisorption process.

A novel method was developed to directly generate S and N co-doped reduced graphene oxide for the adsorption of MB.

Facile synthesis of manganese oxide-embedded mesoporous carbons and their adsorbability towards methylene blue

Herein, a facile strategy to fabricate the novel manganese oxide-imprinted mesoporous carbons (MOPCx, x presents for pyrolysis temperature) was described via the direct pyrolysis of Mn₂(BDC)₂(DMF)₂ (BDC = 1,4-benzenedicarboxylate, DMF = N,N-dimethylformamide) as a self-sacrificed template at various temperatures (x = 550, 750, and 950 ^°C). The characterization results demonstrated the existence of MnO embedded in carbon structures with different morphologies, and enhancing surface areas (249.86-294.67 m²/g) compared with their precursor (3.59 m²/g). For methylene blue adsorption experiments, the MOPC pyrolyzed at 950 ^°C (MOPC950) revealed the best candidate with maximum uptake capacity (124.1 mg/g), so far higher than other MOPCx and Mn₂(BDC)₂(DMF)₂ materials. Finally, adsorption mechanisms involving H-bond, and π-π interaction were proposed via the chemisorption between surface functional groups (carboxyl, phenol, lactone, and base).

Molecule adsorption and corrosion mechanism of steel under protection of inhibitor in a simulated concrete solution with 3.5% NaCl

Herein, the protective performance of a new triazole inhibitor for carbon steel was studied by electrochemical methods. Potentiodynamic polarization curves showed that the anti-corrosion efficiency improved with increasing concentrations of the inhibitor and the results show that it is 22 times corrosion resistance efficiency for inhibitor compared to bare aggressive solution. X-ray photoelectron spectroscopy showed that the film adsorbed well on the carbon steel surface. The scanning vibrating electrode technique demonstrated the corrosion process of carbon steel with and without the protection of inhibitor. Thus, a mechanism for the corrosion process was proposed and the behavior of carbon steel under the protection of the inhibitor was discussed.

Herein, the protective performance of a new triazole inhibitor for carbon steel was studied by electrochemical methods.

Synthesis of nitrogen doped carbon quantum dots/magnetite nanocomposites for efficient removal of methyl blue dye pollutant from contaminated water

As a remedy for environmental pollution, a simple synthesis approach has been developed to prepare nitrogen doped carbon quantum dot/magnetite nanocomposites (Fe₃O₄@NCQDs NCs) using non-toxic and cost effective lemon juice as precursor for removal of organic dye pollutant. Fe₃O₄@NCQDs NCs were characterized by using UV-Vis spectroscopy, FTIR, XRD, FESEM, EDS, TEM, VSM and TGA/DTA. TEM results show spherical shaped Fe₃O₄@NCQDs NCs with an average particle size of 5 nm. Batch adsorption studies were done to investigate the tendency of the nanocomposites to remove representative methyl blue (MB) dye from aqueous solution. The effects of MB dye concentration, dosage of Fe₃O₄@NCQDs NC adsorbent, pH, contact time and temperature were optimized by varying one variable while all the other parameters were kept constant. The experiment showed rapid removal of MB dye within 20 minutes with an adsorption efficiency of over 90.84% under optimum conditions. The adsorption process fits the Freundlich isotherm model well with R² and n values of 0.993 and 1.842, respectively, at 298 K indicating the feasibility of the adsorption process. The adsorption process is spontaneous and involves exothermic behaviour as confirmed by thermodynamic studies. From a kinetic study, it was found that the pseudo-second order model is more suitable to describe the adsorption process than the pseudo-first order model for adsorption of MB dye onto Fe₃O₄@NCQDs NCs.

Herein, we report the green synthesis of magnetic, nitrogen doped carbon quantum dot/Fe₃O₄ NPs using aqueous lemon extract for the efficient removal of organic dye pollutants from contaminated water.

Magnetic ZnFe2O4@chitosan encapsulated in graphene oxide for adsorptive removal of organic dye

Magnetic ZnFe₂O₄@chitosan (ZnFe₂O₄@CS) encapsulated into graphene oxide (GO) layers was fabricated. The ZnFe₂O₄@CS/GO composites showed excellent adsorption capacity towards organic dye.

A recyclable and regenerable magnetic chitosan absorbent for dye uptake

A recyclable and regenerable magnetic polysaccharide absorbent for methylene blue (MB) removal was prepared by coating magnetic polyethyleneimine nanoparticles (PEI@MNPs) with sulfonated chitosan (SCS) and further cross-linked with glutaraldehyde. The driving force for coating is the electrostactic interaction between positively charged PEI and negatively charged SCS. Infrared spectra, zeta potential, thermal gravimetric analysis and X-ray diffraction demonstrated the successful synthesis of magnetic polysaccharide absorbent. The self-assembly of polysaccharide with magnetic nanopartices did not alter the saturation magnetization value of the absorbent confirmed by vibrating sample magnetometer. The nanoparticles showed fast removal (about 30min reached equilibrium) of MB. In particular, the removal ability of MB after desorption did not reduce, demonstrating an excellent regeneration ability. Our study provides new insights into utilizing polysaccharides for environmental remediation and creating advanced magnetic materials for various promising applications.