Cationic Methylene Blue Research Articles

Optimizing catalytic performance: Reduction of organic dyes using synthesized Fe3O4@AC magnetic nano-catalyst

This article presents a sustainable method for the catalytic reduction of both simple and binary dye systems using magnetic activated carbon (Fe3O4@AC) synthesized from almond shells, an agricultural waste biomass. The reduction of methylene blue (MB) and Congo red (CR) was investigated in the presence of NaBH4, and a series of physical-chemical experiments were conducted to elucidate the mechanism of dye conversion and its performance. The results confirmed the successful synthesis of Fe3O4 nanoparticles on the activated carbon surface. The calculated rate constants in a simple system were 0.34 min⁻1 for MB and 0.25 min⁻1 for CR, in the binary system, the Fe3O4@AC catalyst demonstrated enhanced selectivity for the cationic MB dye, attributable to the robust, attractive surface charge. The study aimed to enhance catalytic performance by employing optimization curves generated from a three-level Box-Behnken Design (BBD) simulation. Experimental results indicated that the optimal catalyst dose, dye concentration, and reaction duration were 4–7 mg, 80–120 mg/L, and 5–20 min, respectively. Response surface methodology (RSM) was developed by processing the findings from 17 replicated experiments using a two-quadratic polynomial model, establishing a functional link between the experimental parameters and MB conversion. Optimal conditions for MB conversion were determined to be 7 mg of catalyst, 80 mg/L of MB concentration, and a reaction time of 12.5 minutes, resulting in an estimated conversion rate of 99.99 %. This prediction was validated by experimental findings, with regression analysis confirming a high correlation (R2 > 0.99) between the predicted and observed values. Additionally, the Fe3O4@AC catalyst demonstrated good recyclability and stable performance over three consecutive cycles, maintaining high conversion efficiency without loss of performance. These findings demonstrate that Fe3O4@AC is a viable approach for the rapid and efficient remediation of dyes in water.

Magnetic and visible light-induced novel green synthesized magnetic Co3O4 photocatalysts via sunflower seed meal extract for anionic and cationic dye removal by adsorption assisted photocatalytic degradation

This study was aimed at the preparation of m-Co3O4 NPs (magnetic Co3O4 nanoparticles) from sunflower seed meal (SFSM) which is the waste of sunflower seed oil factories, and their application as a photocatalyst for the adsorption assistant photocatalysis degradation of methylene blue (MB), and direct yellow-50 (DY-50) under the visible irradiations. Also, the photocatalytic performance of m-Co3O4 NPs was evaluated in synthetic wastewater. The produced m-Co3O4 NPs were ferromagnetic with a saturation magnetization value of 4.3 emu g−1 and the degradation of cationic MB and anionic DY-50 dyes by 100% and 93% in 20 min and 35 min, respectively, by adsorption-assisted photocatalytic process under visible light was achieved. The reactions were found to be pseudo-second-order equation for the adsorption-assisted photocatalytic process for both dyes. The photocatalytic activity of m-Co3O4 NPs decreased slightly even after five repeated cycles. These results show that the m-Co3O4 NPs can be used successfully in dye treatment in wastewater with their adsorption-assisted photocatalytic properties, activation by visible light, magnetic separability, and low-cost production.

Selective adsorption of cationic dye by κ-carrageenan-potato starch bio-hydrogel: Kinetics, isotherm, and thermodynamic studies

An eco-friendly κ-carrageenan/potato starch bio-hydrogel is designed for the efficient removal of methylene blue (MB) dye from water. The incorporation of potato starch was successfully confirmed through XRD, FT-IR, and SEM analysis, while TGA highlighted the hydrogel's thermal stability. Batch adsorption experiments demonstrated excellent MB removal efficiency, with a maximum adsorption capacity of 116.1 mg/g under optimal conditions (initial dye concentration: 100 mg/L, contact time: 180 min, temperature: 20 °C, adsorbent dosage: 1.6 g/L, and pH: 11). FT-IR analysis indicated that electrostatic interactions and hydrogen bonding primarily govern the adsorption process. The adsorption followed pseudo-second-order kinetics and fitted well with the Langmuir isotherm model. Thermodynamic studies revealed that the adsorption was exothermic and spontaneous. A key feature of this bio hydrogel is its selective affinity for the cationic dye MB, in a mixture with Acid Orange (AO) and other cationic dyes (Rhodamine B (Rh B) and crystal violet (CV)). The adsorbent also demonstrated impressive reusability, maintaining 93 % of its efficiency after five cycles, highlighting its potential for sustainable and cost-effective water treatment.

Pore design of POM@MOF hybrids for enhanced methylene blue capture

Abstract Adsorption of methylene blue from aqueous effluents is a key technique to treat wastewater discharge from chemical industries. Toward methylene blue adsorption, porous metal–organic frameworks have been promising owing to their high surface areas and tunable porosity. The incorporation of polyoxometalates (POMs) into metal–organic frameworks has been found to facilitate methylene blue adsorption due to electrostatic interactions between the anionic polyoxometalate and the cationic methylene blue. However, it remains unclear how the customizable pore of POM@MOF hybrids affects the capture of methylene blue. In this work, we study the effect of the size and environment of metal–organic frameworks on the property of methylene blue capture for [Zr6O4(OH)4(1,4-benzenedicarboxylate)6] (UiO-66) embedding an α-Keggin-type polyoxometalate [α-SiW12O40]4− (SiW12). Tuning pore size and environment based on ligand engineering of the metal–organic frameworks suggests that (i) lengthening the organic linkers and (ii) functionalization of the linker with −NO2 groups could enhance the methylene blue uptakes. Notably, an increase in the loading amounts of SiW12 on UiO-66 functionalized with −NO2 groups led to outstanding methylene blue capture, comparable to that of representative zeolites such as ZSM-5 and zeolite Y.

Alginate-Based Hydrogel Bead Reinforced with Montmorillonite Clay and Bacterial Cellulose-Activated Carbon as an Effective Adsorbent for Removing Dye from Aqueous Solution.

According to environmental concerns related to water pollution, this study aims to develop a novel hydrogel bead as a biocompatible and efficient adsorbent by integrating bacterial cellulose-activated carbon (BCAC) and montmorillonite (MT) in alginate hydrogel (ALG). The ionotropic gelation method was applied to the fabrication of BCAC/MT/ALG hydrogel beads. The BCAC/MT/ALG hydrogel bead exhibited significantly higher tensile strength, Young's modulus, and thermal stability, with ~1.4 times higher adsorption uptake of methylene blue (MB) from aqueous solution as compared to the pristine ALG bead. The textural properties, including specific surface area and porosity, were beneficial to accommodate the size of cationic MB as the target molecule. This resulted in a remarkable MB adsorption uptake of 678.2 mg/g at pH 7 and 30 °C. The adsorption isotherm showed the best fit for the nonlinear Redlich-Peterson isotherm model. Experimental adsorption data were well-described by the pseudo-second order kinetic model, with R2 values reaching 0.997. In addition, the adsorbent bead demonstrated easy regeneration with high reusability with approximately 75% of MB removal after being used for six cycles. Therefore, BCAC/MT/ALG bead represents an eco-friendly, cost-effective, and highly efficient adsorbent for MB removal from water and could potentially be used for removal of a wide range of cationic dye pollutants from wastewater.

Efficient adsorption of cationic and anionic dyes using hydrochar nanoparticles prepared from orange peel

Hydrochar nanoparticles biosorbent (HCNPs), derived from orange peel was prepared via an in-situ hydrothermal carbonization method. The HCNPs were tested as an effective biosorbent for removing cationic MB (methylene blue) and anionic MO (methyl orange) dyes. The prepared HCNPs was characterized using FTIR, CHN/O, SEM-EDX, UV–visible, XRD, PZC-titration, BET, and XPS. The biosorbent exhibits a good specific surface-to-volume ratio (28.23 m2/g and 0.069 cc/g, respectively) and mesopores size (2.41 nm). UV–Vis data confirm the graphitic nature of the carbon structures. XPS analysis reveals a high enrichment of multiple oxygen functionalities (including C-OH, C = O, and –COO- groups) on the surface. The optimal initial pHs are 3.0 and 5.0–8.0 for removing MO and MB, respectively. Electrostatic attraction plays a substantial role, with other hydrophobic forces in dye removal and binding. Equilibrium is attained during 60/90 min, with half-biosorption-time (tHST) for MB and MO are 4.72 and 6.71 min, respectively. The highest biosorption capacities are 203.4 mg/g for MB and 113.3 mg/g for MO, closely correlated with physiochemical characteristics. Experimental data follows Langmuir isotherm and PSO kinetic models, indicating monolayer chemisorption on a homogeneous surface. The biosorption process for both dyes is exothermic and spontaneous. HCNPs show high durability over multiple biosorption/desorption cycles using HCl and NaOH (0.1 M) for MB and MO, respectively. These findings highlight the promising potential of HCNPs as efficient biosorbents for removing both anionic and cationic dyes.

Degradation of Dyes Catalyzed by Aminophenyl-Substituted Mn-Porphyrin Immobilized on Chloropropyl Silica Gel and Evaluation of Phytotoxicity.

A heterogenized Mn(III) porphyrin-based catalyst was prepared for dye degradation. The new Mn(III) complex of 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin was immobilized, via covalent bond, in chloropropyl silica gel, generating the material (Sil-Cl@MnP) with a loading of 23 μmol manganese porphyrin (MnP) per gram of Sil-Cl. This material was used as a catalyst in degradation reactions of model dyes, a cationic dye [methylene blue (MB)] and an anionic dye (reactive red 120, RR120), using PhI(OAc)2 and H2O2 as oxidants. The oxidation reactions were carried out after the dye reached adsorption/desorption equilibrium with the catalytic material, with a much higher percentage of adsorption being observed for the cationic MB dye (20%) than for the anionic RR120 dye (3%), which may be associated with electrostatic attraction or repulsion effects, respectively, with the negatively charged surface of the silica (zeta potential measurement for Sil-Cl@MnP, ζ = -19.2 mV). In general, there was a higher degradation percentage for MB than for RR120, probably because the size and charge of RR120 would hinder its approach to the MnP active species on the silica surface. With respect to the oxidant, the PhI(OAc)2-based systems showed a higher degradation percentage than those of H2O2. It was observed that the increase in the oxidant concentration promoted a significant increase in the degradation of MB, with a degradation of approximately 65%. The efficiency of the catalyst was also evaluated after successive additions of the oxidant every 2 h, and it can be seen that the catalyst had no loss of efficiency, with a degradation percentage greater than 80% being observed after 8 h of reaction. The phytotoxicity of the products formed in the system was evaluated in a 1:23.5:188 molar ratio Sil-Cl@MnP: MB:PhI(OAc)2 was used. In these studies, phytotoxicity was found for the germination of lettuce seeds when the original solution was used without dilution; however, when diluted (10% V/V), the results were close to the positive and negative controls. Thus, the material obtained proved to be a potential candidate for application in the degradation reactions of environmental pollutants.

Surface enriched ternary hybrid via interfacial polymerization as an effective adsorbent for dye removal

Methylene blue (MB) is a carcinogenic pollutant that can negatively affect both human health and marine life. Developing effective adsorbents for MB removal is therefore crucial for ensuring safe human life and mitigating environmental issues. Herein, we present an interfacial polymerization to synthesize polydopamine assisted multi-walled carbon nanotubes stitched graphene oxide (PDA@MWNTs/GO) as an effective adsorbent for MB removal. Stitching the PDA layer interfacially onto MWNTs/GO effectively prevents disintegration, diminishes agglomeration/restacking issues, and maximizes adsorption sites. The inherent catecholamine functionality within the PDA layer significantly enhances hydrophilicity. These distinctive characteristics endowed the PDA@MWNTs/GO composite with exceptional adsorption capacity for the cationic MB. The effects of MB concentration, pH, and temperature on the dye solution were thoroughly investigated. The results of the adsorption isotherm and kinetics analysis revealed conformity with the Langmuir isotherm model and adherence to the pseudo-second-order kinetic model. Moreover, PDA@MWNTs/GO demonstrated removal efficiency, exceeding 90% after three consecutive cycles of reuse. The adsorption mechanism was driven by electrostatic attraction and π–π stacking. The superior adsorption performance, attributable to the diverse functionalities and high removal efficiency, demonstrates the potential of PDA@MWNTs/GO as an efficient adsorbent for MB and can also function for other cationic dye impurities.

Removal of Methylene blue dye from contaminated wastewater using lignocellulosic biomasses: A comparative study

In this study, lupine seed (Lu-SP) and pumpkin seed shells (PSSP) biomasses were used to create alternative and effective adsorbents. Methylene blue (MB) dye was removed from wastewater using the as-prepared adsorbents at variables solution pH 2.0 –11.0, contact period (0–180 min), and adsorbent mass (0.2–2.0 g/L). The solution pH had a synergistic effect on the improved removal of MB and the optimal adsorption removal for both adsorbents occurred at pH 8.0 and 120 min. The adsorption isotherm modelling results showed a good fit with the Langmuir model, with a maximum monolayer adsorption capacity of 48.98 and 77.48 mg/g for PSSP and Lu-SP, respectively. Similarly, the pseudo-first-order (PFO) model is regarded as the best-fit kinetic model for both adsorbents and suggests the predominance of physisorption via interfacial diffusion. Mechanistic investigation of the present system suggests that both intraparticle diffusion and surface sorption mechanisms control the adsorption rate. Notably, the Lu-SP with a lower surface area (54.013 m2/g) outperformed the PSSP (235.992 m2/g) in terms of adsorption capacity under varying pH. Therefore, in addition to electrostatic interaction, adsorption into the micropores via volume filling is considered one of the adsorption mechanisms. This study, therefore, revealed that the PSSP and Lu-SP may be very helpful for removing cationic MB dye from contaminated wastewater.

A floating biosorbent of polylactide and carboxylated cellulose from biomass for effective removal of methylene blue from water

A floating adsorbent bead was prepared from polylactide (PLA) and maleic anhydride (MAH)-modified cellulose in a one-pot process (OP bead). Cellulose was extracted from waste lemongrass leaf (LGL) and modified with MAH in the presence of dimethylacetamide (DMAc). PLA was then added directly into the system to form sorbent beads by a phase separation process that reused unreacted MAH and DMAc as a pore former and a solvent, respectively. The chemical modification converted cellulose macrofibres (55.1 ± 31.5 μm) to microfibers (8.8 ± 1.5 μm) without the need for grinding. The OP beads exhibited more and larger surface pores and greater thermal stability than beads prepared conventionally. The OP beads also removed methylene blue (MB) more effectively, with a maximum adsorption capacity of 86.19 mg⋅g−1. The adsorption of MB on the OP bead fitted the pseudo-second order and the Langmuir isotherm models. The OP bead was reusable over five adsorption cycles, retaining 88 % of MB adsorption. In a mixed solution of MB and methyl orange (MO), the OP bead adsorbed 96 % of the cationic dye MB while repelling the anionic dye MO. The proposed method not only reduced time, energy and chemical consumption, but also enabled the fabrication of a green, effective and easy-to-use biosorbent.

Electrochemical genosensor based on RNA-responsive human telomeric G-quadruplex DNA: A proof-of-concept with SARS-CoV-2 RNA

In this report, a facile and label-free electrochemical RNA biosensor is developed by exploiting methylene blue (MB) as an electroactive positive ligand of G-quadruplex. The electrochemical response mechanism of the nucleic acid assay was based on the change in differential pulse voltammetry (DPV) signal of adsorbed MB on the immobilized human telomeric G-quadruplex DNA with a loop that is complementary to the target RNA. Hybridization between synthetic positive control RNA and G-quadruplex DNA probe on the transducer platform rendered a conformational change of G-quadruplex to double-stranded DNA (dsDNA), and increased the redox current of cationic MB π planar ligand at the sensing interface, thereby the electrochemical signal of the MB-adsorbed duplex is proportional to the concentration of target RNA, with SARS-CoV-2 (COVID-19) RNA as the model. Under optimal conditions, the target RNA can be detected in a linear range from 1 zM to 1 μM with a limit of detection (LOD) obtained at 0.59 zM for synthetic target RNA and as low as 1.4 copy number for positive control plasmid. This genosensor exhibited high selectivity towards SARS-CoV-2 RNA over other RNA nucleotides, such as SARS-CoV and MERS-CoV. The electrochemical RNA biosensor showed DPV signal, which was proportional to the 2019-nCoV_N_positive control plasmid from 2 to 200000 copies (R2 = 0.978). A good correlation between the genosensor and qRT-PCR gold standard was attained for the detection of SARS-CoV-2 RNA in terms of viral copy number in clinical samples from upper respiratory specimens.

Enhanced Adsorption of Methylene Blue Dye on Functionalized Multi-Walled Carbon Nanotubes.

Carbon nanomaterials are promising adsorbents for dye removal from wastewater also due to their possible surface functionalization that, in principle, can increase the adsorption rate and provide regeneration. To investigate the real advantages of functionalization, we synthesized and characterized through IR, TGA, TEM, XPS and DLS measurements a multi-walled carbon nanotube (MWCNT) derivative bearing benzenesulfonate groups (MWCNT-S). The obtained material demonstrated to have good dispersibility in water and better capability to adsorb methylene blue (MB) compared to the pristine MWCNT adsorbent. Adsorption kinetic studies showed a very fast process, with a constant significantly higher with respect not only to that of the unfunctionalized MWCNT adsorbent but also to those of widely used activated carbons. Moreover, the adsorption capacity of MWCNT-S is more than doubled with respect to that of the insoluble pristine MWCNT adsorbent, thanks to the dispersibility of the derivatives, providing a larger available surface, and to the possible electrostatic interactions between the cationic MB and the anionic sulfonate groups. Additionally, the reversibility of ionic interactions disclosed the possibility to release the adsorbed cationic pollutant through competition with salts, not only regenerating the adsorbent, but also recovering the dye. Indeed, by treating the adsorbed material for 1 h with 1 M NaCl, a regeneration capacity of 75% was obtained, demonstrating the validity of this strategy.

Green chemistry route to chitosan hydrogels and investigation of the materials as efficient dye adsorbents

Abstract Biopolymer-based materials for the adsorption of toxic dyes represent an interesting class of materials for environmental applications. Here we report on chitosan as the starting material for synthesizing dye adsorbents. In particular, the synthesis, characterization, and cationic dye adsorption properties of chitosan hydrogel adsorbents are reported. Polyanionic itaconated chitosan derivatives were synthesized in solvent-less conditions for the first time. Itaconated chitosan was cross-linked using thiol-ene chemistry to obtain hydrogels. The influence of the incorporated carboxylate groups and the cross-linker fraction on the adsorption of Methylene Blue (MB) was investigated. In addition, the impact of pH, adsorbent dose, initial concentration, and ionic strength were investigated to determine the optimum conditions for MB uptake, and the dye uptake kinetics, adsorption isotherms, selectivity, and reusability of the adsorbents were unveiled. A maximum adsorption capacity of 556 mg/g could be achieved, outperforming commercial activated charcoal and ion exchange resins. Furthermore the chitosan hydrogel adsorbents were shown to capture >90 % of cationic MB from a binary equimolar mixture with the anionic dye Methyl Orange. Since the adsorbents can be regenerated and re-used afterwards at least 20 times, retaining a high dye adsorption fraction of >95 %, these materials are promising candidates for environmental applications.

Sustainable use of low-cost adsorbents prepared from waste fruit peels for the removal of selected reactive and basic dyes found in wastewaters

Agricultural wastes are potential sustainable adsorbents since they are available in large quantities, are low-cost, and may require little or no treatment, in some cases. In this study, several fruit peels, such as banana, orange, and pomegranate, were collected from local markets and prepared by a simple and eco-friendly method and used as natural adsorbents for the removal of both anionic (Reactive Red 120 (RR120), Reactive Black 5 (RB5), Remazol Brilliant Blue R (RBBR)) and cationic Methylene Blue (MB) dyes found in wastewaters. Many industries, such as leather and textiles, can release huge amounts of synthetic dyes into the wastewater during dyeing processes. These are one of the most important pollutants of water pollution as they cause enormous damage to the water body and also affect the health of organisms due to their toxicity and carcinogenicity. The search for a sustainable and at the same time efficient material for the removal of a wide variety of dyes is the innovation of this work. These peels were prepared by washing, drying, grinding, and finally sieving, under natural sustainable conditions. Porosometry (BET analysis), FTIR, SEM/EDS, and XRD techniques were used to characterize the fruit peels before and after the adsorption process. Factors affecting the adsorption of dyes (adsorbent dosage, pH solution, initial concentration of dyes, contact time, and temperature) were investigated. According to the results, in terms of the effectiveness of fruit peels as (natural) adsorbent materials, for anionic dyes, 5.0–6.0 g/L of banana or orange dry peels was sufficient to remove near or even more than 90% anionic dyes at pH 2.0, and 4.0 g/L was sufficient to remove 98% of cationic MB dye at pH 9.0. Similar amount of pomegranate peels had lower efficiency for anionic dyes (50–70%), while cationic MB was still efficiently removed (98%) at pH 9.0. Moreover, the adsorption process in all cases was found to better fit to pseudo-second-order model, in comparison to pseudo-first-order model. According to isotherms, Freundlich model fitted better in some cases to the equilibrium data, while the Langmuir model in others. Finally, this study demonstrates the viability of reusing the banana, orange, and pomegranate peel adsorbents for eight, four, and five cycles, showing a gradual reduction of around 50% of their effectiveness.Graphical

Insights into simultaneous efficient removal of cationic and anionic dyes by nitrogen-rich seaweed carbon adsorbent

Textile dyes, including methylene blue (MB) and methyl orange (MO), pose a significant threat to water quality. This study delves into the competitive adsorption mechanisms pivotal for the concurrent removel of cationic MB and anionic MO dyes using nitrogen-rich seaweed-based carbon adsorbents. Synthesized through the pyrolysis and NaOH activation of Enteromorpha seaweed biomass, the preparation method is both uncomplicated and cost-effective, holding promising applications in industry. Characterization unveiled a commendable specific surface area of 911 m2/g, accompanied by abundant nitrogen- and oxygen-containing functional groups. Batch adsorption experiments showcased exceptional removal efficiencies surpassing 99.8% for both dyes. Molecular dynamics simulations offered valuable insights into the dynamic multi-stage adsorption behavior, while density functional theory calculations clarified the chemisorption-based interaction mechanism. Notably, MB displayed superior adsorption affinity compared to MO. An integrated adsorption mechanism was proposed, encompassing electrostatic attraction, migration, and enhanced chemisorptive binding of dye aggregates at active sites on the adsorbent surface. The innovative adsorption mechanism adopted by this carbon-based adsorbent prepared from nitrogen-rich seaweed can effectively remove cationic and anionic dyes, laying a solid foundation for future research on real water bodies with complex compositions.

Investigation of Visible and UV Light‐Induced Photocatalysis Properties of Oleic Acid‐Ligated Cobalt‐Mixed Magnesium Ferrite Nanoparticles for Photodegradation of Cationic and Anionic Dyes

Owing to numerous potential applications in multiple fields, the study of nanosized magnetic spinel ferrites has been gaining significance. Synthesis and characterization of high‐quality magnetic nanocrystals with narrow size distribution, enhanced magnetic saturation, and outstanding properties for bioenvironmental applications are presented in the current study. Nanoparticles of oleic acid‐ligated Co0.5‐mixed Mg0.5Fe2O4 were prepared by a simple thermal decomposition method. The effect of cobalt (Co2+) content on the structural, optical, magnetic, and thermal properties of magnesium ferrite was assessed by powder X‐ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT‐IR), and vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). High‐resolution transmission electron microscopy (HR‐TEM) and energy dispersive X‐ray (EDX) spectroscopy were used to determine morphology and composition, respectively. Nanoparticles produced are highly crystalline and homogeneous, having an average size of 10 nm, with large saturation magnetization (61 emu/g) and high magnetic moment. Photocatalytic properties of prepared nanocrystals were studied by degradation of anionic Orange II and cationic methylene blue (MB) dyes under UV and visible light radiations for different time intervals. The anionic Orange II dye exhibited higher degradation, up to 97.2% and 92.2%, within a 90‐minute time period of ultraviolet and visible light irradiation, respectively. The cationic MB dye also displayed significant degradation, up to 91.9% and 93.8%, within 300 min under UV and visible light sources, respectively. The synthesized OA‐ligated nanoparticles degrade cationic and anionic dyes more effectively than previously reported in the literature and, thus, can be prime candidates for effective photo catalytic dye degradation and waste water cleaning applications, through the harvesting of ambient solar energy.

Electrostatic Nanocage-Confined Probe for Electrochemical Detection of CA19-9 in Human Serum.

Prompt and accurate detection of CA19-9 in human serum has great clinical significance for the early diagnosis and disease monitoring of cancer. Herein, we develop a convenient and antifouling electrochemical sensor for CA19-9 determination by immobilization of both an electrochemical redox probe [methylene blue (MB)] and immunorecognition element (CA19-9 antibody) on an electrostatic nanocage consisting of bipolar silica nanochannel array (bp-SNA). bp-SNA is composed of a negatively charged inner layer (n-SNA) and positively charged outer layer (p-SNA), which could be stably prepared on indium tin oxide (ITO) in several seconds using a two-step electrochemically assisted self-assembly approach and display asymmetric surface charges for confinement and enrichment of cationic MB into the inner n-SNA layer through electrostatic interaction. Modification of the CA19-9 antibody on the top surface of bp-SNA confers the sensing interface with specific recognition capacity. An antibody-antigen complex formed at the as-prepared immunosensor causes the decreased electrochemical signals of MB, achieving sensitive determination of CA19-9 with a wider linear dynamic range from 10 μU/mL to 50 U/mL and a low detection limit (3 μU/mL). Furthermore, accurate and feasible analysis of the CA19-9 amount in human serum samples by our proposed probe-integrated electrochemical immunosensor is realized.

Synthesis of graphene/silica composites and its removal efficiency of methylene blue dye from water

Water supply remains constant; however, industrial wastewater has been raised. Due to the high demand for clean water, there is a continued need for water treatment. Here, graphene nanoplatelets modified with silicon dioxide nanoparticles were synthesized and characterized. Structural, surface morphology and physichemical characteristics of GNP-SiO2 were characterized by FTIR, XRD, and SEM. The nanocomposite was assessed for methylene blue (MB) adsorption from wastewater. To study the impact of the adsorption parameters, the factorial design with multivariate method central design, analysis of variance, response surface 3D graph, Pareto Chart, and Normal probability plot was used. The experimental equilibrium data fit with the Langmuir isotherm model. Removal capacity (qm) was 495 mg g−1 for GNP-SiO2 nanocomposite with the formation of monolayer coverage and specific homogenous sites on GNP-SiO2 nanocomposite. The kinetic mechanism suggested that the PSO model fits kinetic MB removal mechanisms over the GNP-SiO2 nanocomposite and progressed profoundly via chemisorption. The MB cationic dye removal by GNP-SiO2 nanocomposite was by electrostatic attraction, hydrogen bond, and π–π interactions as well as the surface adsorption. The results revealed that prepared GNP-SiO2 nanocomposite was effective for MB adsorption from aquatic solution.

Adsorption of methylene blue dye onto modified activated carbon produced from groundnut shells

In this research work, groundnut shells agricultural byproducts were utilized for the production of modified groundnut shell based activated carbon (MGSAC) through the use of phosphoric acid and ethylene-diamine tetraacetic acid disodium salt (Na2EDTA) as an activating agent and a modifier, respectively. A three factor, two-level full factorial design (FFD) was employed for the exploratory design of experiments (DoE). The independent process variables are temperature, activation time, and activating agent concentration for the production of MGSAC in a muffle furnace. The product yield and methylene blue (MB) dye adsorption were considered as the performance indicators for the process. Regression analysis was conducted to examine the influence of process variables on the responses of the process parameters. From the analysis, it was found that the activation temperature has the most significant effects on the MGSAC product yield and the activation time for the adsorption of MB dye. The results obtained showed that the best operating conditions for production of MGSAC were carbonization temperature of 450°C, activation time of 30 min and activating agent concentration of (35 mmol Na2EDTA; 50% H3PO4) which resulted in the product yield of 55.5% MGSAC, and 99.6% MB dye adsorption. It was also observed that experimental values obtained were in good agreement with the values predicted by the model. Hence, the two-level FFD DoE technique demonstrated worthwhile features in disclosing the dominant factors that affect the production of modified groundnut shell based activated carbon. The products appear to be promising adsorbents for the adsorption of cationic MB dye from wastewaters.

Photocatalytic Degradation of Methylene Blue Dye Using Cuprous Oxide/ Graphene Nanocomposite

Aims: The aim of this study is to evaluate the photocatalytic degradation of methylene blue dye on cuprous oxide/graphene nanocomposite. Background: Cuprous oxide (Cu2O) nanoparticles are among the metal oxides that demonstrated photocatalytic activity. However, the stability of Cu2O nanoparticles due to the fast recombination rate of electron/hole pairs remains a significant challenge in their photocatalytic applications. This in turn, leads to mismatching of the effective bandgap separation, tending to reduce the photocatalytic activity of the desired organic waste (MB). To overcome these limitations, graphene has been added to make nanocomposites with cuprous oxides. Objective: In this study, Cu2O/graphene nanocomposite was synthesized and evaluated for its photocatalytic performance of Methylene Blue (MB) dye degradation. Method: Cu2O/graphene nanocomposites were synthesized from graphite powder and copper nitrate using facile sol-gel method. Batch experiments have been conducted to assess the applications of the nanocomposites for MB degradation. Parameters such as contact time, catalyst dosage, and pH of the solution were optimized for maximum MB degradation. The prepared nanocomposites were characterized by using UV-Vis, FTIR, XRD, and SEM. The photocatalytic performance of Cu2O/graphene nanocomposites was compared against Cu2O nanoparticles for cationic MB dye degradation. Results: Cu2O/graphene nanocomposite exhibits higher photocatalytic activity for MB degradation (with a degradation efficiency of 94%) than pure Cu2O nanoparticle (67%). This has been accomplished after 180 min of irradiation under visible light. The kinetics of MB degradation by Cu2O/graphene composites can be demonstrated by the second-order kinetic model. The synthesized nanocomposite can be used for more than three cycles of phtocatalytic MB degradation. Conclusion: This work indicated new insights into Cu2O/graphene nanocomposite as highperformance in photocatalysis to degrade MB, playing a great role in environmental protection in relation to MB dye.