MB Removal Efficiency Research Articles

Low-cost chemically treated sugarcane bagasse for removal of cationic, anionic and neutral dyes from aqueous solution

ABSTRACT This study presents use of low-cost chemically treated sugarcane bagasse for the adsorption of three dyes: cationic (methylene blue-MB), anionic (Methyl orange-MO) and neutral (Neutral red – NR) dyes. The prepared sugarcane bagasse was characterised using a scanning electron microscope (morphology) and Fourier transform infrared techniques. The FTIR spectra revealed that all the bands were identified in the sugarcane bagasse due to cellulose, pectin and lignin presence. The effect of adsorbent dose, contact time, pH and concentration on the adsorption performance of sugarcane bagasse for the removal of MB, MO and NR dyes was studied. Kinetic and isotherm studies were also carried out to study the adsorption process further. The maximum adsorptive removal efficiency of MB, MO and NR dyes was found to be 98.2%, 50.3% and 81.2%, respectively, at the optimised condition of adsorbent dose: 8 g/L, time: 120 min, pH: 10 and concentration: 50 ppm. From adsorption kinetics, it was established that the adsorption process followed pseudo-second-order rather than pseudo-first-order. The correlation coefficient values for the PFO and PSO models were 0.9319 and 0.9994, respectively, for MB dye adsorption on SCB. The adsorption isotherm study established that the adsorption process followed the Langmuir model rather than the Freundlich model.

Application of Optimization Response Surface for the Adsorption of Methylene Blue Dye onto Zinc-coated Activated Carbon.

The activated carbon was produced in the first phase of this investigation by chemically activating hazelnut shell waste with H3PO4. Composite materials were obtained by coating the activated carbon with zinc oxide, whose BET surface area was calculated as 1278 m2 g-1. ZnO-doped ZnO/AC composite was synthesized as an adsorbent for its possible application in the elimination of organic dyestuff MB, and its removal efficiency was investigated. Morphological properties of ZnO/AC were characterized using analytical methods such as XRD, SEM, and BET. The adsorption system and its parameters were investigated and modeled using the response surface method of batch adsorption experiments. The experimental design consisted of three levels of pH (3, 6.5, and 10), initial MB concentration (50, 100, and 150 mg L-1), dosage (0.1, 0.3, and 0.5 g 100 mL-1), and contact time (5, 50, and 95 min). The results from the RSM suggested that the MB removal efficiency was 98.7% under the optimum conditions of the experimental factors. The R2 value, which expresses the significance of the model, was determined as 99.05%. Adsorption studies showed that the equilibrium data fit well with the Langmuir isotherm model compared to Freundlich. The maximum adsorption capacity was calculated as 270.70 mg g-1.

Fabrication of used-tea embedded alginate beads for cationic dye remediation: Synergistic effect of surface adsorption and intraparticle diffusion

Water pollution has become a major concern due to high industrialization and poor waste management policies. Recently, organic contaminants such as dyes are severely influencing environmental conditions and therefore, it must be employed to efficient treatment processes before discarding in waterbodies. In this work, used-tea embedded alginate beads were fabricated as a novel adsorbent for removing a cationic dye (methylene blue, MB). The physical properties of fabricated beads were investigated and also characterized using field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The highest MB removal efficiency of about 97.38 ± 1.84% was obtained at optimized pH 7 and 25 °C. The adsorption capacity (qe) increased with MB concentration and the pseudo-second-order model exhibited excellent fit. MB adsorption comprises rapid surface adsorption (initial 5 min) and slow inter-particle diffusion (after 5 min). Supporting the Langmuir isotherm indicated the formation of a monolayer of MB on the surface of the beads and the calculated maximum adsorption capacity (qm) was 421.94 mg/g. Negative ΔG (-7.25 kJ/mol) and ΔH (-52.67 kJ/mol) reveal MB removal as a spontaneous and exothermic process. Positive entropy change of ΔS (152.05 J/mol) states increased randomness, facilitating promoted affinity of beads for free MB molecules. A removal efficiency of about 90.40 ± 2.91% was obtained up to 3rd cycle of its reuse, which further decreased to 67.11 ± 1.72% during 5th cycle. The MB adsorption mechanism was investigated by comparing the physiochemical and morphological characteristics of beads before and after MB removal.

Removal of methyl blue from aqueous solutions with nano-magnetic Pinus brutia biochar

In the study, the removal of dye (methyl blue) from aqueous solutions by batch/agitation adsorption method was investigated using Pinus brutia (PB). For this purpose, first, PB wood was collected and made into wood chips (PB), and then Pinus brutia biochar (PBB) was made. The PBB was modified to gain nano-magnetic properties. The biochar structure was characterized by FT-IR. PBB and nM-PBB were used for the removal of MB dye. The adsorbent amount, temperature, pH, time and dye concentration were investigated in the adsorption process with adsorption isotherms, kinetics and thermodynamics to estimate their MB removal efficiency. Sorption equilibrium for MB dye was reached by nM-PBB within 60 min and adsorption efficiency up to 99.007% was reached. While the adsorption kinetics followed a pseudo-second-order kinetic model, the Langmuir isotherm model, with a maximum adsorption capacity of 107.527 mg/g (nM-PBB), showed homogeneous physiochemical adsorption. The efficiency was found to be a spontaneous endothermic reaction. It can be suggested that nM-PBB can be used to remove MB.

G-C3N4/CuO loaded polyester fabric as effective Fenton-like dip-catalyst for the oxidation of dyes

This work aims to assess the catalytic efficiency for the degradation of organic dyes through advanced oxidation using a novel catalyst PE/g-C3N4-CuO. Polyester (PE) serves as an inert support, while the active catalyst comprises nanoparticles of graphitic carbon nitride g-C3N4-and copper oxide (CuO). The PE/g-C3N4-CuO was successfully prepared by sonicating g-C3N4 onto the PE matrix followed by the deposition of CuO nanoparticles, an efficient and reusable “dip catalyst”. Various physicochemical techniques have been employed to characterize the synthesized g-C3N4, CuO, and PE/g-C3N4-CuO such as FTIR, XRD, SEM, TEM, XPS and TGA. The composite is used for the oxidation of MB, MO, CR and RhB dyes via advanced oxidation process in presence of H2O2 as oxidant. In addition, the impacts of several parameters, such as pH, catalyst surface, CuO loading (%), H2O2 and MB concentration, on the degradation kinetics were thoroughly examined. A removal efficiency (94 %) of MB and TOC (80 %) has been attained for 30 min of the reaction using a surface of 4 cm2 PE/5%g-C3N4-10%CuO. The synthetized composite presented high stability after five reaction cycles with no discernible decrease in catalytic activity. Furthermore, OH were determined as the main reactive oxidative species (ROSs) responsible for highly efficient MB degradation. Finally, catalyst stability and recyclability demonstrated that the PE/g-C3N4-CuO might serve as a substitute Fenton-like catalyst for the oxidation of dyes and environmental cleanup.

The influences of Keggin-type H3PW12O40 nanostructure on Polyurethane microfiltration membrane to reinforce screening organic pollutants from wastewater

Manifestly, unceasing growth industrialization has caused to produce the non-segregated phases, engendering complexity in wastewater remediation. Therefore, we endeavored to construct the electrospun Polyurethane (PU)-based Microfiltration (MF) membrane that the Keggin-type H3PW12O40 (KHPW) nanostructure embedded in it by simplified strategy; after that, the PU/KHPWx (x= 0.5, 1, 1.5, and 2 %wt) nanocomposite membranes executed to purify the emulsifier-stabilized Walnut oil (EWO). Fortunately, perfect wettability, controlled porosity, and high negative charge boosted the values of Permeated Water Flux (PWF) and Oil Rejection Efficiency (ORE), which equaled 2150 L.m−2.h−1 and 100 % for the 1400 mg.L-1 of EWO by the PU/KHPW2 membrane, respectively; after that, the fouling resistance parameter (i.e., the Flux Recovery Ratio (FRR)) improved to 62.18 % in pH = 9. Notably, the MB Removal Efficiency (MRE) surveyed to render the light-driven catalytic activities of KHPW, and the Taguchi method optimized the values of operational parameters. Hence, the MRE astonishingly elevated to 79.3 % by PU/KHPW2 at the ameliorated conditions under UV-light irradiation, conferring the self-cleaning merits to the PU/KHPWx samples. After reviewing previously published articles, these authentic observations about the multifunctional capabilities of PU/KHPW2 elucidated insights towards robust screening water pollutants, which discreetly could utilize it in the pre-treatment units of MF.

Activating Illite kaolinite clay with CTAB for adsorbing Methylene blue: Isotherms, Kinetics, and thermodynamics studies

In this study, a stable multilayered adduct of maghemite surfactant and clay was created by sandwich-like electrostatic self-assembly of cationic polyelectrolytes of cetyltrimethylammonium bromide (CTAB) with illite kaolinite (IKaol) clay. The adsorptive property of IKaol/CTAB towards MB from . Aquatic system uptake was investigated. Its characteristics were analysed using X-ray powder diffraction, Fourier transform-infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and the zero point of charge. To attain higher performance of the IKaol/CTAB for MB adsorption, the primary key factors that influence the MB dye, such as (A: loading CTAB into the composite matrix of IKaol), adsorbent dose (B: 0.02–0.06 g), pH (C: 4–10), temperature (D: 30–60 °C), and time (E: 5–60 min) , were optimised using the Box–Behnken design method. The obtained results show that the highest MB removal efficiency of 86.24 % was observed at the following significant interactions: AB, BC, and AC and at optimum adsorption operation parameters (A: 0%, B: 0.06 g, C: 7, D: 45◦C, and E: 17.5 min). At these optimum conditions, the best adsorption capacity of MB dye (114.94 mg/g) was recorded at 45°C. The most effective isotherms and kinetic models were the Freundlich and pseudo-second-order kinetic models. The MB dye adsorption mechanism by IKaol can be assigned to several interactions, such as electrostatic attractions, n-π interaction, and hydrogen bonding interactions. The results of this study demonstrate the viability of IKaol as a promising precursor for the creation of an efficient adsorbent that can be used to remove cationic dye from an aqueous environment.

Synthesis of novel antibacterial nanocomposite CuO/Ag-modified zeolite for removal of MB dye

Novel CuO/Ag nanocomposites added zeolite (CAZ) were successfully fabricated, and their effectiveness as an antibacterial on S. aureus and MB removal was evaluated. EDX, XRD, and FTIR confirm the presence of the elemental compositions of CAZ. Friable CuO nanorods (10–70 nm in diameter) existed on the surface of the zeolite. Pure zeolite had a higher band gap (5.433 eV) and lower MB removal efficiency than CAZ. The adsorption method by CAZ was more effective at removing MB than photodegradation. 0.10 CAZ had the highest removal effectiveness (~ 99%) and adsorption capacity (~ 70.4 mg g−1) of MB. The inhibitory zone diameter for 0.005 CAZ against S. aureus was 20 mm, while 0.01 CAZ had a diameter of 17 mm. Azithromycin, ceftriaxone, and erythromycin antibiotics demonstrated lower or no efficacy against S. aureus than CAZ. Significant antibacterial activities and wastewater treatment were achieved by CAZ. The combination of photodegradation and adsorption enhanced pollutant removal. It will be interesting to study further the optimal molar ratio for MB removal (0.10 CAZ) in future investigations.

Membrane-based electrospun poly-cyclodextrin nanofibers coated with ZnO nanograins by ALD: Ultrafiltration blended photocatalysis for degradation of organic micropollutants

Membranes with simultaneous selective adsorption functionality and excellent photocatalytic response have been proposed for water remediation, especially for treating textile and industrial wastewater. However, state-of-the-art membranes are easily fouled by pollutant adsorption that impacts their reusability. Here we report the development of a crosslinked electrospun poly-cyclodextrin (Poly-CD) nanofiber (NF) membrane coated by atomic layer deposition (ALD) with ZnO nanograins for the removal of pollutants from wastewater. The inherent high affinity of poly-CD NFs favored the selective adsorption of cationic impurities, and the reactive oxygen species produced by photoirradiation of the ZnO surface effectively degraded adsorbed contaminants. The NFMs has signifies that, even under the dark, they have a removal efficiency of around 80% which may be due to the high adsorption nature. Further, these NFM are highly reusable while decorating the ZnO nanograins on the NFM, which degraded the adsorbed pollutant and opened up the active site to further adsorb the dye molecule on the poly-CD surface. Under the static mode, the ZnO(100)@poly-CD NFM achieved the highest MB removal efficiency of 94.3%, followed by ZnO(25)@poly-CD, ZnO(200)@poly-CD, and poly-CD, which had removal rates of 91.3%, 87.7%, and 83.1%, respectively in 120 min of photoirradiation. Modulating the photocatalytic reaction in a flow channel, ZnO(100)@poly-CD nanofibrous membranes (NFMs) achieved 2.19-fold higher removal efficiencies (98.6% in 60 min) in a flow-through filtration system than under static conditions (a non-filtration method). Furthermore, the flow-through mode promoted the mass transfer of pollutants through NFMs, which increased reactive oxygen species production by inhibiting electron-hole recombination. Furthermore, the inherent self-cleaning function conferred by the photocatalytic activity of surface ZnO increased membrane structural stability and provided a faster removal rate.

A novel effective bio-originated methylene blue adsorbent: the porous biosilica from three marine diatom strains of Nanofrustulum spp. (Bacillariophyta)

In the present paper, for the first time the ability of the porous biosilica originated from three marine diatom strains of ‘Nanofrustulum spp.’ viz. N. wachnickianum (SZCZCH193), N. shiloi (SZCZM1342), N. cf. shiloi (SZCZP1809), to eliminate MB from aqueous solutions was investigated. The highest biomass was achieved under silicate enrichment for N. wachnickianum and N. shiloi (0.98 g L−1 DW and 0.93 g L−1 DW respectively), and under 15 °C for N. cf. shiloi (2.2 g L−1 DW). The siliceous skeletons of the strains were purified with hydrogen peroxide and characterized by SEM, EDS, the N2 adsorption/desorption, XRD, TGA, and ATR-FTIR. The porous biosilica (20 mg DW) obtained from the strains i.e. SZCZCH193, SZCZM1342, SZCZP1809, showed efficiency in 77.6%, 96.8%, and 98.1% of 14 mg L−1 MB removal under pH 7 for 180 min, and the maximum adsorption capacity was calculated as 8.39, 19.02, and 15.17 mg g−1, respectively. Additionally, it was possible to increase the MB removal efficiency in alkaline (pH = 11) conditions up to 99.08% for SZCZP1809 after 120 min. Modelling revealed that the adsorption of MB follows Pseudo-first order, Bangham’s pore diffusion and Sips isotherm models.

The methyl blue adsorption performance and mechanism of NaX zeolite synthesized from Huadian oil shale ash

BackgroundAs a by-product of oil shale retorting process, oil shale ash would cause serious environmental problems. The similar composition to that of zeolites makes oil shale ash suitable to synthesize zeolites, which can be used to remove dyes from wastewater with low cost. This could provide not only an effective way for the potential utilization of oil shale ash but also a cheap raw material for the preparation of zeolites. It is of great significance to realize the win-win situation of environment and economic benefit of oil shale and dyeing industries. MethodsIn this work, NaX zeolite was synthesized successfully from Huadian oil shale ash by the alkaline fusion hydrothermal method and used to remove methyl blue. Significant findingsThe specific surface area, pore volume and BJH adsorption average pore diameter of the synthetic zeolite are 366.8672 m2/g, 0.208501 cm3/g and 7.0101 nm, respectively. Under the optimum conditions, the removal percentage of methyl blue could reach to 96.0%, and the synthetic zeolite has an excellent reusability. The existence of salts and salinity would influence the MB removal efficiency. The adsorption mechanism study indicates that electrostatic attraction, hydrogen bonds and pore diffusion facilitate the methyl blue adsorption on the synthetic NaX zeolite.

Study on the synthesis of g-C<sub>3</sub>N<sub>4</sub>/TCPP porphyrin composite and its application as photocatalyst for treatmen of MB organic dye in water

The g-C3N4/TCPP porphyrin composite was successfully fabricated via self-assembly approach. The composite was characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and FT-IR techniques. The results showed good integration of the porphyrin nanofibers with diameter of less than 100 nm and the length of several micrometer on the g-C3N4’s surface. The prepared g-C3N4/TCPP porphyrin composite showed high photocatalytic efficiency for MB degradation under sunlight irradiation, with MB removal efficiency > 90% after 100 min of simulated sunlight irrdadiation. The g-C3N4/TCPP porphyrin composite could be used as a promising photocatalyst for the treatment of other organic dyes in water.

ZnO@g-C3N4 S-scheme photocatalytic membrane with visible-light response and enhanced water treatment performance

Zinc oxide–Graphitic carbon nitride (ZnO@g-C3N4) composite membranes were prepared via in-situ growing ZnO crystals in the g-C3N4 membrane. In this composite membrane, ZnO crystals were embedded in loose surface layers of g-C3N4 membrane, which can repair some non-selective defects and improve the dye retention performance. In addition, the hetero-structures formed between ZnO and g-C3N4 nanosheets promoted the separation of photogenerated electron-holes in g-C3N4 layer, and improving the photocatalytic and anti-fouling performance of ZnO@g-C3N4 composite membranes. Herein, the prepared composite membranes showed excellent dye removal performance and self-cleaning property in dynamic recirculation filtration systems under visible light irradiation. The optimized sample (CNZ-0.15 g) showed MB removal efficiency of 94.4% and water flux of 336.8 L.m−2.bar−1.h−1. The outcome of this research would suggest the application of graphitic nitride nanomaterials for developing highly efficient photocatalytic membranes.

Simultaneous adsorption and catalytic degradation of methylene blue dye over recyclable Mn4(P2O7)3 nanoflakes: Mechanism and efficiency

In this study, highly efficient Mn4(P2O7)3 nanoflakes were successfully synthesized and characterized by SEM, TEM, XRD and XPS. Mn4(P2O7)3 nanoflakes applied as an inexpensive adsorbent and nanozyme to remove organic pollutants (methylene blue, MB) from water. The equilibrium adsorption studies showed that the organic dye followed Langmuir model of adsorption. The adsorption mechanism is based on the electrostatic interaction between the deprotonated (negatively charged) group in Mn4(P2O7)3 and MB cationic molecules; then, in basic solution the adsorption capability of Mn4(P2O7)3 remarkably increased. In addition, the applicability of Mn4(P2O7)3 catalase mimic in organic wastewater reclamation was exhibited via catalytic degradation of MB organic pollutant. The heterogeneous catalytic process performed at basic pH in the presence of H2O2 via reactive oxygen species (ROS) production. Experimental results indicated that superoxide radical was the main active species in degradation process of MB. Under the basic condition, the leaching of ions, which mainly occurs in the Fenton reaction, is significantly reduced. Water purification is done more efficiently by incorporating of adsorption and degradation method. It was found that the removal efficiency of MB (initial concentration at 40 mg/L) achieved to 99.2% after 30 min. Furthermore, the Mn4(P2O7)3 sample could be reused in water treatment process many times without a considerable decrease in its adsorption and catalytic efficiency. This stable and recyclable system might present a new sight for developing sufficiently low-cost and highly efficient nanomaterials for waste water treatment.

A mechanism study of methylene blue adsorption on seaweed biomass derived carbon: From macroscopic to microscopic scale

Biomass based active adsorbent can be prepared by activation process to adsorb dyes. In this study, using macroalgae as raw material, the biomass based activated carbon material was prepared by NaOH activation method to adsorb methylene blue. The activated adsorbent with high specific surface area (1238.491 m2 g−1) was characterized by BET, XRD, FTIR and XPS. The effects of impregnation ratio, amount of adsorbent, pH and contact time on the adsorption activity of biochar on MB were evaluated. The adsorption kinetics, molecular dynamics and density functional theory were discussed. The maximum MB removal efficiency of SWAC reached 98.56 % at 30 °C and pH= 5 which is due to its large specific surface area and mesoporous slit structure. MD simulation shows that MB molecules were adsorbed on carbon layer through face-to-face stacking. DFT calculation and subsequent electron structure analysis suggested that a synergistic effect of π-π stacking, cation-π interaction, and electrostatic interaction could help stabilize adsorbed MB molecules. And an excellent adsorption capacity SWAC is due to its graphitic N sites for high electronegativity.

Preparation of heterogeneous Fenton catalyst with residual carbon separated from coal gasification slag as carrier

ABSTRACT This study prepares a magnetite (Fe3O4)-based Fenton-like catalyst based on the residual carbon separated from coal gasification slag as a support by the chemical precipitation method. The catalysts are characterized using XRD, SEM-EDX, and N2 adsorption-desorption methods. In the process, the adsorption capacity, catalytic activity under various conditions, and catalyst reusability were evaluated with methylene blue as the target pollutant. According to SEM results, Fe3O4 particles are attached to the pore and surface of the residual carbon support and have good dispersion. BET findings demonstrate that Fe3O4/residual carbon catalyst has a greater surface area and pore volume than residual carbon support. The removal efficiency of MB by adsorption of Fe3O4/residual carbon catalyst is less than 10% after 120 min. But 2.4Fe-UC catalyst shows 2-h removal rates of 98% when the optimum removal efficiency of MB is under the following conditions: 2.5 mmol/L H2O2, 0.2 g/L catalysts for 50 mg/L MB at an initial pH of 3. Notably, outstanding catalytic stability and reusability of the 2.4Fe-RC catalyst have been revealed as it can be reused 6 times with>80% of the MB removal efficiency.

Green synthesis of carbon-doped zinc oxide using Garcinia mangostana peel extract: Characterization, photocatalytic degradation, and hydrogen peroxide production

Recent decades have cordially observed unprecedented events in the fields of photochemistry for water remediation and fine chemical production. In this study, we reported sustainable methods to fabricate carbon-doped zinc oxides (ZnO–C) using aqueous Garcinia mangostana peel extracts as a carbon source. Via the reinforcement of ZnO–C crystal structures with the employment of calcination techniques, ZnO–C accentuated better crystallization with average nanoparticle size of 25–70 nm. In addition to the introduction of carbon, the samples revealed the doping of heteroatoms such as N, S, and P simultaneously in ZnO structures originating from the phytochemicals in the extracts. It is observed that ZnO–C sample calcinated at 700 °C for 1 h gives out the best results for photoactivity. Moreover, the fabricated ZnO–C-700-1.0 exhibited a near complete removal towards methylene blue and malachite green, while removal of rhodamine B was 62.13% after 120 min using commercial UV light irradiation under pH 11 with the usage of 50 mg of catalyst. Further investigations of H2O2 photoproduction also validated the versatile application of the materials with the highest H2O2 evolution rate reaching 38.75 mM/g.h. The techno-economical of H2O2 production using ZnO–C reveals the scale-up viability of the process. Moreover, MB removal efficiency of 92.13% and H2O2 production of 8.83 mM/g.h were observed for the optimal ZnO–C sample under visible light irradiation. Subsequently, these results reinforce the applicability of phytoextract as a green approach to reach sustainability for synthesis and modifying the optical structure of semiconducting materials for water remediation and H2O2 production.

Removal of methylene blue dye from aqueous solution using an efficient chitosan-pectin bio-adsorbent: kinetics and isotherm studies.

Wastewater contains organic compounds, including dyes, which have potential risks to the environment. Hence, these compound needs to be eliminated from the aqueous solution. In the present study, chitosan-pectin composite (Cs-Pc) was used as an adsorbent to remove methylene blue dye (MB) from synthetic wastewater. To evaluate the parameters affecting adsorption, including the initial MB concentration, solution pH, contact time, and Cs-Pc dose, batch experiments were carried out. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), and pH point of zero charges (pH pzc) were applied for characterizations of Cs-Pc. The optimum conditions were obtained with an initial MB concentration of 50mg L-1: solution pH ~ 11, Cs-Pc dose: 1.5g L-1 and 180min contact time, which caused 97.77% of MB removal. In addition, the removal efficiency of MB was more influenced by pH than by sorbate dose. Also, Cs-Pc had a higher ability to remove MB than chitosan and pectin, probably due to its highly porous structure and rough surfaces that provides active sites and facilitate MB adsorption. The maximum removal efficiency and the adsorption capacity of MB onto Cs-Pc at 500mg L-1 concentration under optimum conditions were 98.67% and 328.02mgg-1, respectively. The adsorption kinetics and isotherms were best described by pseudo-second-order and Freundlich equation, respectively. After four times of recycling, the removal efficiency of MB was above 96%. Electrostatic and pi-pi interactions are the main mechanisms for the removal of MB onto the adsorbent. So the application of Cs-Pc is promising for MB removal from polluted solutions not only due to its strong adsorbing capability but also due to its excellent ability to reuse.

Sulfonated magnetic multi-walled carbon nanotubes with enhanced bonding stability, high adsorption performance, and reusability for water remediation.

In view of the simple and rapid conveniency of magnetic separation, magnetic nanocomposites had notably gained attention from researchers for environmental field applications. In this work, carboxylated magnetic multi-walled carbon nanotubes (c-MMWCNTs) and novel sulfonated MMWCNTs (s-MMWCNTs) were synthesized by a facile solvent-free direct doping method. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, energy dispersive X-ray, vibrating sample magnetometer, and point of zero charge analyses confirmed the successful doping of the Fe3O4 nanoparticles into the functionalized MWCNTs to form MMWCNTs. Besides, the bonding stabilities of both c-MMWCNTs and s-MMWCNTs were compared, and results showed that s-MMWCNTs possessed more substantial bonding stability than that of c-MMWCNTs with significantly less leaching amount of Fe3O4. The adsorption capacity of s-MMWCNTs was higher than that of c-MMWCNTs owing to the stronger electronegativity sulfonic group in s-MMWCNTs. Moreover, the reusability experiments proved that the adsorbent remained consistently excellent MB removal efficiency (R > 94%) even reused for twelve cycles of batch adsorption. The finding of the present work highlights the simple fabrication of novel s-MMWCNTs and its potential to be served as a promising and sustainable adsorbent for water remediation owing to its enhanced bonding stability, high adsorption performance, magnetic separability, and supreme recyclability.

Mechanochemical route for carboxy substituted Schiff-Base polymer coated MWCNT composite as an efficient adsorbent for the removal of Methylene Blue dye: Kinetics, Isotherms and Thermodynamic studies

In the present investigation, we report a rapid and green mechanochemical approach for the synthesis of carboxy substituted Schiff-Base polymer (cPSB) and MWCNT coated with cPSB composite (cPSB@MWCNTs) as an efficient adsorbent for cationic methylene blue MB dye. The as-synthesized cPSB and cPSB@MWCNTs were characterized by Fourier-transformed infrared spectrometer (FTIR), X-ray diffraction (XRD) and Scanning electron microscopy (SEM) to analyze the structure, size and morphology. Effects of different variables such as catalyst loading, contact time, effect of initial dye concentration and pH of the medium during the process of dye adsorption were studied. Adsorption was in agreement with the pseudo-second-order and is a chemisorption process according to the kinetic analysis. The adsorption equilibrium data for the dye adsorption process fitted well with the Langmuir model. In cPSB@MWCNTs, the removal efficiency of MB was found to be 99 % in 90 min at pH 7. The adsorption of dyes on cPSB@MWCNTs from thermodynamic data was found to be spontaneous and endothermic with a continuous decrease in entropy. Further cPSB@MWCNTs composite demonstrated admirable maximum adsorption capacity towards both MB (96.9 mg g−1) indicating cPSB@MWCNTs as an efficient cationic dye adsorbent.