Methylene Blue Adsorption Capacity Research Articles

Regulating the surface chemistry of covalent organic frameworks for enhancement cationic dye removal and identification.

Simultaneous removal and identification of trace-level cationic dye pollutants from water is both important and challenging owing to their highly polar and complex sample matrices. In this study, three covalent organic frameworks (COFs) were synthesized using 2, 4, 6-triformylphloroglucinol with ethidium bromide (EB) containing positively charged groups, 3, 5-diaminobenzoic acid (DABA) containing negatively charged groups, and p-phenylenediamine (Pa) lacking charged groups. These were named EB-COFs, TpPa-1, and DP-COFs, respectively, and were employed as adsorbents for the extraction and identification of cationic dyes. The adsorption performance of the three COFs toward methylene blue (MB) and crystal violet (CV) was investigated. By incorporating carboxyl groups into DP-COFs, the surface chemistry of the adsorbent was effectively tailored, enabling complete exploitation of selective cationic sites. This facilitated dynamic interactions with cationic dyes through multiple adsorption mechanisms, including electrostatic, π-π, and H-bonding interactions. DP-COFs exhibited high adsorption capacities for MB and CV, achieving 383 and 326mgg-1, respectively. The adsorption behavior was further analyzed using adsorption isothermals, kinetics, and thermodynamics. Moreover, DP-COFs were employed as a matrix in laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) to adsorb and directly identify both cationic dyes without the need for an elution process. This approach demonstrated high sensitivity, high reproducibility, low background interference, and excellent salt tolerance. The limits of detection for MB and CV were 0.12 and 0.04ngmL-1, respectively, representing improvements of 166-fold and 225-fold compared with using DP-COFs solely as a matrix. Recovery rates of both dyes in spiked industrial wastewater and lake water samples ranged from 81.4 to111.1% with RSDs of 1.9-6.3%. These results highlight the high reliability of the proposed method.

Mechanistic Understanding of Superior Methylene Blue Adsorption Capacity in a Novel g-C3N4 Modified Amorphous Na-Ca-Mg Silicate Adsorbent: Insights from Multinuclear Solid-State NMR Spectroscopy.

Silicate-based adsorbents offer significant advantages over traditional materials, particularly due to their superior thermal and chemical stability, enhanced regenerability, and the ability to endure more rigorous operating conditions. In this study, an amorphous Na-Ca-magnesium silicate adsorbent (SAAM) and its g-C3N4-modified counterpart (gCN-SAAM) were synthesized via alkali activation and a subsequent thermal process, respectively. The g-C3N4 modification resulted in a novel hybrid adsorbent with a remarkable methylene blue (MB) adsorption capacity of 420 mg g-1, four times higher than the unmodified sample, setting a new benchmark. Solid-state 29Si (MAS and CP/MAS), 1H MAS, and 13C CP/MAS NMR spectroscopy were used to investigate the complex structures of these adsorbents and their interactions with MB. The local structure of SAAM primarily consists of Q3 Si units, with minor Q0 and Q1 Si species, structural water, and Mg-OH sites. Exposure to MB caused an upfield shift in the 29Si CP/MAS spectrum and enhanced resonances in the high-field region, indicating MB interaction with Si sites. 1H MAS NMR spectra revealed significant interactions between water molecules in the geopolymer-like framework of SAAM and MB. The thermal treatment of SAAM with urea to produce gCN-SAAM enhanced the polymerization of Q3 Si species and increased the relative fraction of Q4 Si sites. This treatment also reduced the intensity of some Mg-OH units, showing interaction with g-C3N4. After MB adsorption on gCN-SAAM, NH2 groups of g-C3N4 disappeared, and shifts in the C2N-NHx and C3N sites indicated their involvement in adsorption, while Si sites remained intact. This thermal method creates a sustainable, cost-effective and efficient adsorbent for MB removal from wastewater. Multinuclear NMR spectroscopy provides detailed insights into the adsorbent's complex structure and MB interactions, potentially guiding the design of improved future adsorbents.

Preparation of nitrogen-doped lignin porous carbon using low dosage KHCO3 for efficient methylene blue adsorption: Activation mechanism and adsorption performance

The previous requirement for activation of porous carbon adsorbents commonly exceeded several times the mass of the carbon precursor. Therefore, it was crucial to develop cost-effective and efficient carbon adsorbent materials for long-term environmental remediation. In this study, biorefinery lignin was utilized to fabricate porous carbon with an ultrahigh specific surface area (3423 m2 g−1) and pore volume (1.52 cm3 g−1) by employing melamine as the nitrogen source and a low dosage of KHCO3 as the activator. Multiple activations during the carbonization process contributed to the exceptional characteristics of the porous carbon, including well-developed pore structure, high specific surface area, and reasonable nitrogen doping. The porous carbon demonstrated remarkable adsorption capabilities with a maximum methylene blue (MB) adsorption capacity of 1457 mg g−1. Structural characterization conducted before and after adsorption revealed that electrostatic interactions, pore filling, hydrogen bonding, and π-π stacking were among the main mechanisms employed by lignin porous carbon for effective MB adsorption. The proposed method is a simple, green, highly efficient, and environmentally friendly approach that can be applied to treat lignin from various industrial sources. It provides valuable insights into the development of advanced carbon materials suitable for adsorption and capacitor applications.

Evaluation of ZnO/NiO/kaolin nanocomposite as a sorbent/photocatalyst in hybrid water remediation process

The colored effluents causing environmental pollution pose a threat to the world. This study aims to assess the effectiveness of nickel oxide/zinc oxide/kaolin nanocomposite (NiO/ZnO/Ka) in removing methylene blue (MB) from water. Furthermore, it aims to examine the impact of synergetic adsorption/photocatalytic degradation (APCD) on the MB adsorption capacity as well as the suitability of the nonlinear adsorption isotherm and kinetic modeling in analyzing the process. The composites ZnO/Ka and NiO/ZnO/Ka were synthesized by the sol–gel method and were characterized by X-ray diffraction, Fourier transform infra-red, field emission scanning electron microscopy, and Brunauer–Emmett–Teller. The impacts of various parameters, such as pH, initial concentration of MB, dose, ionic strength, and temperature, on MB removal were studied using adsorption and APCD. The results showed that ZnO/Ka had the maximum adsorption capacity of MB (39.31 mg/g) and the maximum removal (78.61%) under optimal conditions of pH 10, clay dosage of 0.1 g/25 mL, initial concentration of MB 200 mg/L, contact time of 15 min, and 298 K, while NiO/ZnO/Ka showed the maximum adsorption capacity of MB (40.88 mg/g) and maximum removal (83.74%) at pH 7. It was also noticed that Temkin and Fritz–Schlunder models are the best isotherm models, with the highest R2 (1 and 0.842) for ZnO/Ka and NiO/ZnO/Ka, respectively. Moreover, the data of adsorption and photodegradation of MB onto ZnO/Ka and NiO/ZnO/Ka were revealed to follow pseudo-first-order and Avrami kinetic models with R2 (0.897) for ZnO/Ka and (0.986) for NiO/ZnO/Ka. Overall, NiO/ZnO/Ka showed better removal of MB than ZnO/Ka, and the hybrid process (photodegradation process after adsorption) enhanced the overall efficiency of MB removal than adsorption alone.

Synthesis of zirconium-based metal-organic framework under mild conditions and its application to the removal of cationic and anionic dyes from wastewater

Water resources contaminated by industrial dyes can pose a significant threat to the environment and human health. Herein, we conducted a study on the removal of cationic and anionic dyes, such as methylene blue (MB) and methyl orange (MO), using MIL-140A, a zirconium-based metal-organic framework. MIL-140A is synthesized in a Schlenk flask at 120 °C, whereas its conventional synthesis route involves a teflon-sealed autoclave at 220 °C, highlighting the cost reduction and lower equipment requirements of the low-temperature synthesis. The structure of MIL-140A is characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and nitrogen adsorption techniques. The optimal pH for the adsorption of two dyes by MIL-140A is pH 5–8 for MB and pH 3 for MO. The adsorption equilibrium can be reached within 60 min at room temperature, and the adsorption of both dyes on MIL-140A follows pseudo-second-order kinetics and Langmuir isotherm, and the maximum adsorption capacity of MO and MB by MIL-140A were 163.6 and 89.2 mg/g, respectively. Thermodynamic studies indicate an entropy-driven spontaneous process. The adsorption mechanism of MO and MB on MIL-140A is investigated using FT-IR and X-ray photoelectron spectroscopy. The adsorption of MO involves coordination between Zr and sulfonate, while MB adsorption occurs via π-π interactions. Additionally, MIL-140A exhibits better removal efficiency for MO from lithium battery wastewater compared to MB, primarily due to stronger coordination interactions than π-π interactions. These findings demonstrate that MIL-140A is a promising adsorbent for effectively removing both anionic and cationic dyes from water resources.

Copolymeric hydrogels with high capacities of hydration and methylene blue adsorption in water

Copolymers based on monomethyl hydrogen itaconate (βHI) with 2-hydroxyethyl methacrylate (HEMA) and βHI with 2-hydroxypropyl methacrylate (HPMA) were prepared in different monomer molar ratios. The reactivity parameters of copolymerization (r1 and r2) were determined. The values obtained for r1 and r2 indicate that P(βHI-co-HEMA) exhibits a high tendency towards alternate copolymerization. Structural characterization of the copolymeric hydrogels was carried out using Fourier transform infrared (FTIR) and 1H NMR spectroscopies, where the characteristic signals of the constituent functional groups were observed. The typical thermal stability of the polymeric systems was observed by thermogravimetric analysis (TGA). In addition, the swelling capacity in water was evaluated, and a swelling percentage over 655 % and 1249 % presented P(βHI-co-HEMA) and P(βHI-co-HPMA) respectively, in a period of 15 days at pH 10, and presence of 0.05 M NaNO3.Additionally, methylene blue (MB) adsorption capacity was studied in batch mode by varying different experimental parameters. MB adsorption capacity of 122.79 mg g−1 and 112.24 mg g−1 were achieved for P(βHI-co-HEMA) and P(βHI-co-HPMA), respectively. The data obtained were fitted to the Elovich kinetic model and to a Redlich-Peterson isotherm. The thermodynamic parameters indicated that the adsorption phenomenon is spontaneous, endothermic and with a high probability of occurrence. The adsorption efficiency decreases by approximately 60 % in the presence of interfering ions (Na+, K+, Ca2+ and Cl−). The adsorbents are reusable and achieve high MB adsorption efficiency (90 % and 80 % for P(βHI-co-HEMA) and P(βHI-co-HPMA) respectively) in a textile-simulated wastewater. Based on the results obtained, it is concluded that P(βHI-co-HEMA) and P(βHI-co-HPMA) show great potential for use in adsorption of water molecules, for MB retention and purification of simulated effluents from the textile industry.

Microwave assisted activation of silkworm excrement for fast adsorption of methylene blue and high performance supercapacitor

The activated carbon (AC) with an exceptionally high surface area was made of silkworm excrement (SE) by microwave-assisted KOH activation (MAKA). It was investigated for the potential applications in methylene blue (MB) adsorption and a supercapacitor electrode. The effect of activation time on the AC properties and performance was studied. The physical and chemical properties of the as-prepared samples were analyzed by FE-SEM, TEM, N2 adsorption, and Raman spectroscopy. Remarkably, the AC with the largest specific surface area (SAs) of 2530.3 m2g−1 was produced by partial carbonization of SE at 400 °C (SE400-5) and then activated for only 5 min. The large SAs is attributed to the abundance of micro-pores, leading to the enhanced MB absorption performance, as equilibrium was reached within 10 min at 25 ppm of MB concentration. The maximum MB adsorption capacity for SE400-5 was 902.56 mg g−1. The adsorption isotherms revealed that the Langmuir model best fits the empirical data (R2 ≥ 0.9813), indicating monolayer adsorption. The kinetic model fitted well to the Pseudo-second-order (PSO) (R2 ≥ 0.9691). CV, GCD, and EIS measurements also evaluated the electrochemical properties of all samples. The electrodes were made without the addition of conductive material. The SE400-5 also had the lowest total resistance and highest total effective capacitance, which resulted in its highest specific capacitance (Cs) of 322 F g−1 at 0.5 A g−1. The capacitive retention of SE400-5 remained as high as 98% even after 10,000 cycles at 10 A g−1. These results demonstrate that SE is a viable source of AC for MB adsorption and a supercapacitor electrode.Graphical abstract

Experimental and theoretical insights into the adsorption mechanism of methylene blue on the (002) WO3 surface

This work investigates the efficiency of green-synthesized WO3 nanoflakes for the removal of methylene blue dye. The synthesis of WO3 nanoflakes using Hyphaene thebaica fruit extract results in a material with a specific surface area of 13 m2/g and an average pore size of 19.3 nm. A combined theoretical and experimental study exhibits a complete understanding of the MB adsorption mechanism onto WO3 nanoflakes. Adsorption studies revealed a maximum methylene blue adsorption capacity of 78.14 mg/g. The pseudo-second-order model was the best to describe the adsorption kinetics with a correlation coefficient (R2) of 0.99, suggesting chemisorption. The intra-particle diffusion study supported a two-stage process involving surface adsorption and intra-particle diffusion. Molecular dynamic simulations confirmes the electrostatic attraction mechanism between MB and the (002) WO3 surface, with the most favorable adsorption energy calculated as -0.68 eV. The electrokinetic study confirmed that the WO3 nanoflakes have a strongly negative zeta potential of -31.5 mV and a uniform particle size of around 510 nm. The analysis of adsorption isotherms exhibits a complex adsorption mechanism between WO3 and MB, involving both electrostatic attraction and physical adsorption. The WO3 nanoflakes maintained 90% of their adsorption efficiency after five cycles, according to the reusability tests.

Preparation of nanocomposite hydrogel based on Fe3O4-TMSPM/poly(HEMA-PEG6MA-IA) for the removal of methylene blue dye from aqueous solution

In this work, a new hydrogel poly(2-hydroxyethyl methacrylate-co-polyethylene glycol methacrylate-co-itaconic acid) poly(HEMA-PEG6MA-IA) covalently crosslinked with Fe3O4 nanoparticles functionalized with 3-(trimethoxysilyl)propyl methacrylate organosilane (TMSPM) was prepared by free radicals, named Fe3O4-TMSPM/HG. FTIR-ATR, TGA, XRD, and TEM experiments were utilized to explore the Fe3O4-TMSPM/HG nanocomposite hydrogel. Swelling studies were also carried out in water, in different pH media, and then used in the adsorption of the cationic dye methylene blue (MB) from aqueous media. The factors controlling the adsorption process such as pH, dose, contact time, initial MB concentration, and temperature were investigated. The maximum MB adsorption capacity (270.27 mg/g) using Fe3O4-TMSPM/HG was obtained under the best conditions pH 8, dose 0.5 mg/mL, contact time 24 h, and ambient laboratory temperature (≈15 °C). The kinetic and isothermal experiments showed that the adsorption of MB followed the pseudo-second-order and Langmuir models. The effect of temperature on the adsorption capacity is related to the swelling, since the Fe3O4-TMSPM/HG nanocomposite hydrogel exhibit temperature-responsive. After 5 adsorption–desorption cycles, the adsorption decreased by 19 mg/g compared to the initial adsorption capacity. All the experimental results show that the prepared Fe3O4-TMSPM/HG nanocomposite hydrogel has the potential to be applied as an adsorbent for MB dye.

Adsorption properties of alkali-activated stone wool

Alkali-activated materials are actively studied as adsorbents for toxic metals, nutrients, and dyes from wastewater. They are produced using an environmentally friendly process from low-cost aluminosilicate precursors, and thus have significant potential for fostering the development of clean technology. One of the potential precursors is stone and glass wool, for which alkali activation has been successfully demonstrated in construction products. In this study, alkali-activated stone wool was assessed for adsorption for the first time. Stone wool manufactured without organic resin (SW) and another stone wool with organic resin being removed by heat treatment (SW-O) were alkali activated using NaOH, Na2CO3, NaAlO2, or Na silicate solution, and characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetry–mass spectrometry, and potentiometric titrations to understand the surface properties affecting adsorption. Comparative adsorption experiments were conducted using methylene blue (MB), cobalt (Co(II)), arsenite (As(III)), and NH4+ at 100 mg × L−1 concentration, 1 g × L−1 adsorbent dose, 24 h contact time, and pH of 7. The raw stone wools demonstrated almost no adsorption, whereas the alkali-activated stone wools adsorbed up to 78, 42, 3, and 18 mg × g−1 of MB, Co(II), As(III), and NH4+, respectively. The samples prepared with the SW Na silicate demonstrated higher adsorption capacities for MB and Co(II). For As(III), an adsorption capacity was similar regardless of the mixture. The highest adsorption capacity for NH4+ was achieved with SW-O NaOH. The increased adsorption capacities were related to the increase in the specific surface area, more negative zeta potential, formation of tobermorite-like structures, and an increase in the quantity of surface OH groups. The varying adsorption levels of specified contaminants are possibly governed by their speciation at pH 7, aqueous radii, and the adsorption mechanism. This study demonstrated that stone wool-based adsorbents could have practically relevant potential for wastewater treatment.

Effective adsorptive removal of heavy metal anion Cr(Ⅵ) and dye cation methylene blue by the novel 2D material TiVCTx MXene

With the increasingly serious industrial pollution, the effective removal of heavy metal ions and organic pollutants from wastewater has become a key issue of environmental protection. In this paper, a new MXene material, TiVCTx, was prepared by in situ etching, and its adsorption capacity of heavy metal anion Cr(Ⅵ) and methylene blue (MB) dye cation was studied. The effect of adsorption time, pH values, temperatures, initial concentrations of adsorbent and adsorbate, interfering ions on the Cr(Ⅵ) and MB adsorption of TiVCTx was systematically investigated. It is found that TiVCTx has excellent Cr(Ⅵ) and MB adsorption property, the adsorption capacity can be as high as 600mg/g and 1430mg/g, respectively. The adsorption experiments revealed that the adsorption process of Cr(Ⅵ) conformed to the Langmuir isotherm model and the Pseudo-second-order kinetic model, which indicated that the Cr(Ⅵ) adsorption was a heat-absorbing monolayer chemisorption. In contrast, the adsorption process of MB is in accordance with the Freundlich isotherm model and the Pseudo-second-order kinetic model, suggesting that the MB adsorption was an exothermic multilayer chemisorption. The results of X-ray electron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis further confirmed that the reductive adsorption and electrostatic adsorption can account for the outstanding Cr(VI) and MB adsorption capacity of TiVCTx, respectively.

Good adsorption performance for both cationic and anionic dyes by a novel crosslinked tetrafluoroterephthalonitrile-tannic acid-chitosan polymer synthesized via one-pot reaction

In this work, tetrafluorophenonitrile was utilized to crosslink tannic acid and chitosan together to form a new crosslinked polymer (CSTTA), and then the Fe3O4 nanoparticles were prepared and immortalized on the CSTTA at the same time to obtain the Fe3O4/CSTTA composite. The structures of CSTTA polymer and Fe3O4/CSTTA composite were characterized by SEM, FTIR, TGA, 13CNMR, XPS, WAXD, N2 adsorption-desorption isotherm, VSM, and zeta potential measurement. The CSTTA could simultaneously adsorb the cationic methylene blue (MB) and anionic orange G (OG), and its adsorption behaviors for MB and OG conformed to the pseudo-second-order kinetic model and the Langmuir isotherm model, which were spontaneous according to thermodynamic calculation. The CSTTA possessed not only high adsorption capacities for both MB and OG up to 1092.69 mg/g and 519.89 mg/g at 303 K under the optimal pH conditions of pH=10 and pH=1, respectively, but also the good reused ability. In addition, the Fe3O4/CSTTA composite could also absorb both MB and OG with good magnetically recollected ability to avoid secondary pollution.

Cnicus Benedictus roots as a low-cost adsorbent for methylene blue dye removal from aqueous solution: kinetic and equilibrium studies

In this research, Cnicus Benedictus roots powder (CBRP) was utilized as a low-cost adsorbent for removing methylene blue (MB) as a cationic dye from aqueous solution. Characterization of CBRP by Boehm titration method, Fourier transform infrared (FT-IR) and environmental scanning electron microscope (ESEM) indicates the presence of different types of functional groups and a very rough surface filled with cavities, suitable for MB adsorption. The effect of various parameters such as CBRP dose (0.2–2 g/1L), contact time (0–180 min), initial pH (1–10), coexisting anions/cations and the initial MB concentration (100–500 mg L−1) on MB adsorption were examined, the results showed that MB uptake depends on the pH of solution, the electrostatic attraction forces, the formation of H-bonds and π–π interactions are the possible CBRP–MB interaction mechanisms. Adsorption kinetic of MB on CBRP was best represented by linear and non-linear form of the pseudo-second order model. The experimental equilibrium data were best described by linear and non-linear forms of Langmuir and Redlich–Peterson isotherm models (R 2> 0.98) with a maximum MB adsorption capacity of 85.47 mg g−1 at 25 °C, the adsorption efficiency R (%) was greater than 90 (%). MB adsorption-desorption experiments showed the reusability of CBRP for five consecutive cycles. According to the obtained results, CBRP can be used as a natural adsorbent material for cationic dyes removal from aqueous solution.

Methylene blue adsorption by chemical-activated Trichanthera gigantea leaf

ABSTRACT This study investigated the potential of NaOH-treated Trichanthera gigantea leaf (TGL) powder as a sustainable, low-cost biosorbent for methylene blue (MB) removal from wastewater. Characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller, and energy-dispersive X-ray spectroscopy (EDX) techniques confirmed favorable morphology, identifying micropores, suitable functional groups, notable surface area, pore volume, and elemental diversity. Batch experiments systematically investigated the influence of operational parameters, including contact time, initial MB concentration (5–35 mg/L), pH (2–10), and biosorbent dosage (2–10 g/L) on adsorption performance. The Langmuir isotherm model best represented the experimental data (R² values of 0.993 and 0.9725), indicating favorable adsorption (RL < 1) and maximum MB adsorption capacities of 0.822 and 0.330 mg/g for treated and untreated TGL, respectively. Statistical analysis (ANOVA) results further identified the most significant factors influencing MB biosorption. These findings highlight the potential of NaOH-treated TGL powder as an effective and eco-friendly solution for removing MB dye from industrial effluents, contributing to sustainable wastewater treatment and environmental protection.

A green strategy to realize the high value utilization of lignin for hydrogel formation

Grafting lignin extracted from pulping black liquor onto hydrogel not only endows hydrogel with strong adsorption capacity, but also realizes the high value utilization of lignin, thereby alleviating the environmental pressure caused by the exhaust gas generated by direct combustion of black liquor. However, those lignin fragments have lost generous active functional groups as the high temperature polycondensation during industrial production, restricting the improvement of lignin-based hydrogel adsorption capacity. Herein, we propose a strategy combining amination and oxidation to prepare lignin derivatives with low molecular weight and high activity groups. The introduced amino groups promote the Cα-Cβ cleavage of β-O-4 unit and the oxidation treatment converts S-unit hydroxyl to carboxyl. The hydrogel obtained by grafting aminated-oxidized-lignin shows satisfactory adsorption performance with a methylene blue adsorption capacity of 697.47 mg/g (vs. 195.12 mg/g for pristine hydrogel). The retention ability has also been greatly improved that only 0.43 % of the adsorbed methylene blue is released even after 96 h (vs. 5 % within just 12 h for pristine hydrogel). This work not only provides a new strategy for the high-value utilization of biomass resources, but also offers a new idea for the preparation of hydrogels with high adsorption performance.

NaOH activated Galla chinensis residue hydrochar for the adsorption of methylene blue

To achieve the resource utilization of waste materials, this study utilized Galla chinensis residue (GCR) as a raw material to synthesize green hydrochar (HC) in one step, activated with NaOH to obtain alkali-activated hydrochar (AHC), which was then used for the adsorption of organic dye methylene blue (MB). The results showed that when the temperature was 25 °C, the pH was 7 and the MB concentration was 300 mg/L, the adsorption capacity (AC) of MB by AHC was 278.97 mg/g and the removal rate was 78.67 %. Langmuir (R2 = 0.9949) and the pseudo-second-order dynamics model (R2 = 0.9983) described the adsorption behavior of MB on AHC, which was an exothermic process according to thermodynamics. The adsorption mechanism included electrostatic attraction, hydrogen bond, π-π interaction, and the pore filling effect. Even after 5 cycles of adsorption–desorption, the AHC adsorbent maintained a high AC for MB, indicating that the HC prepared from GCR was a sustainable and promising adsorbent for MB, providing a new application direction for the reuse of GCR.

Anthill clay activated Ocimum gratissimum extract for effective adsorption of methylene blue and chromium (VI) ion from wastewater: Insights into the adsorption isotherms, kinetics, thermodynamics, and mechanisms

The removal of methylene blue (MB) dye and hexavalent chromium (Cr(Vl)) ions from water bodies have necessitated the search for a promising adsorbent material with high adsorptive performance, facile operation, and economical. Here, a novel adsorbent was prepared by activating anthill clay (AC) with Ocimum gratissimum leaf extract (OG@AC) by ultrasonic strategy method to eliminate MB and Cr(Vl) from the aqueous environment; however, the activation strategy serves as an important factor that influenced the adsorptive performance towards MB and Cr(Vl). Furthermore, a high BET surface area of 120.48 m2/g was measured for OG@AC which is attributed majorly to the green activation strategy. The SEM micrograph of OG@AC was seen to have displayed a leaf-like plate formed by quartz and kaolin. In the batch experimental study, the MB and Cr(Vl) adsorption capacities towards OG@AC were determined to be 227.52 and 143.45 mg/g, respectively. Also, the adsorption kinetics and isotherms models results revealed that the adsorption process of OG@AC towards MB and Cr(Vl) was best described by pseudo-first-order and Freundlich models, suggesting that the adsorption process involves a multilayer physisorption. Moreso, thermodynamic results revealed the adsorption process is feasible, spontaneous, and endothermic in nature. The OG@AC exhibited an outstanding regeneration ability and stability towards MB and Cr(Vl) by maintaining a removal efficiency of 79.11 % and 81.20 % even at the tenth successive adsorption-desorption cycles. Overall, this research sheds more insight on how anthill clay is activated using a feasible design and green chemical (Ocimum gratissimum leaf extract) to enhance its adsorptive performance towards MB and Cr(Vl), which can broaden its wide application in the real world.

Kinetic Adsorption Studies of Cationic Dyes onto Molecular Sieve and Activated Carbons

Background: Dye-containing wastewater causes irreparable damage to the ecological water system. Although adsorbents are widely used for treating wastewater containing dyes, the comparative investigation on these materials is still insufficient for their wide applications in the industries. Objective: With the aim of comparing efficient and fast adsorbent materials for cationic dyes, we analyzed and evaluated the adsorbents of the MCM-41 molecular sieve and activated carbons. Methods: The adsorption performance was studied on the common colored organics, such as cationic dyes of rhodamine B (RhB) and methylene blue (MB) dyes. The present work examined the impact of experimental variables, including initial dye concentration, adsorption time, and pH, on the adsorption process and performance, as well as the adsorption kinetics of the diverse adsorbents towards two cationic dyes. Results: MCM-41 molecular sieves showed relatively high adsorption capacity for RhB and AC-2, which made their adsorption capacity for MB much higher than that of MCM- 41 molecular sieves. A comprehensive analysis was conducted using pseudo-first-order and pseudo-second-order to decipher the mechanism of dye adsorption. The heterogeneous adsorption mechanism could explain the dye adsorption behavior of MCM-41 molecular sieve and activated carbons. Conclusion: The results demonstrated the influence of the pore structure and surface properties of the adsorbents on the adsorption capacity of dye molecules in an aqueous solution. For the initial concentration of cationic dye solutions of 20 mg/L, the MCM-41 molecular sieve had a MB adsorption capacity of 130.8 mg/g under alkaline conditions at pH=10, while the activated carbon adsorbents showed a stable MB adsorption capacity of 266.6 mg/g under different pH conditions, proving their applicability in treating wastewater containing dyes under different acid/base environments.

Chitosan‐Carbon Aerogel for Efficient Removal of Methylene Blue Dye: Synthesis, Characterization, Adsorption Mechanism and Antimicrobial Therapies

AbstractChitosan‐carbon aerogel was synthesized via a facile and eco‐friendly method and characterized for its structural and morphological properties. The composite exhibits remarkable adsorption kinetics and a high potential for removing Methylene Blue (MB) dye, attributed to its enhanced surface area, porous structure, and active functional groups. The adsorption capacity of chitosan‐carbon aerogel increased from 38 to 86.8 mg/g as the pH was raised from 2 to 7. The maximum MB adsorption capacity increased from 22 to 632 mg/g as the initial MB concentration increased from 25 to 2000 mg/L. The saturation adsorption capacity of the chitosan‐carbon aerogel was 668 mg/g. After five reuse cycles, the removal efficiency dropped from 89 % to 73.1 %. Antibacterial tests showed that the width of the inhibition zone for S. enterica was 16.2 ± 0.38 mm, indicating similar antibacterial activity for both chitosan and chitosan‐carbon aerogels. These findings underscore the potential of chitosan‐carbon aerogel as a sustainable and cost‐effective solution for dye removal in wastewater treatment.

Synergy of Magnetic Nanoparticles and Sodium Alginate-Coated Lignin for Effective Pollutant Remediation, Simple Recovery, and Cost-Effective Regeneration.

In the pursuit of sustainable materials for environmental remediation, this study presents the development and comprehensive characterization of cobalt ferrite nanoparticles (CFNPs) incorporated in lignocellulosic-derived sodium alginate (CFNPs@LCG-SA) biocomposite beads. These biobased beads exhibit exceptional adsorption capabilities, particularly for methylene blue (MB) dyes, rendering them promising candidates for wastewater treatment. Using a comprehensive range of analytical techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis-derivative thermogravimetry (TGA/DTG), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), etc., we elucidated their structural, physicochemical, and thermal properties. Their multifunctional nature, derived from lignin and sodium alginate components, provides ample active sites for both physical interactions and chemical bonding with contaminants apart from the magnetic character attributed by the CFNPs. With a freeze-drying approach, the optimal adsorption capacity and removal rate of MB reached 97 mg/g and 99%, respectively, and no meaningful decline in their activity was noted even after six cycles. The CFNPs@LCG-SA biocomposite beads emerge as a cost-efficient and sustainable remedy for environmental cleanup, offering valuable perspectives in environmental preservation and advancing green energy technologies.