Cationic MB Research Articles

Microemulsion Templating Synthesis of Hierarchical Porous Ag‐Doped SiO2‐TiO2 Composites for Efficient Degradation of Noxious Methylene Blue Dye: Effect of Calcination Environment

AbstractWe report herein a dual function mesoporous structure of titanium oxide based porous carbon with large surface‐to‐volume ratios for efficient degradation of noxious methylene blue dye (MB) from an aqueous environment. The mesoporous photocatalysts is fabricated via direct template synthesis of highly ordered silica‐titania monolith doped with Ag0/Ag2O starting from a quaternary microemulsion liquid crystalline phase. The produced monoliths are subjected in‐situ to doping by growing silver, in the cubic cavities, and on the silica/titania structure's domain. This study investigated the efficiency of novel composite materials, consisting of silver‐doped silica‐titania (SiO2/TiO2), which is synthesized using the microemulsion templating approach. The photocatalytic performance of the synthesized composite in the photodegradation of MB has been studied. The procedure of photodegradation was employed to achieve decolorization of the cationic MB dye using visible light. The catalyst effectively achieved the decolorization of the dyed solution through the processes of adsorption and photodegradation. The composite consisting of SiO2, TiO2, and Ag2O at a ratio of 1 : 1:0.5, which underwent calcination in an air environment (AgOST), exhibited a removal efficiency of 99 % compared to its calcined state under argon (AgSTC).

Adsorption technique using new semi-IPN hydrogels for high removal of methylene blue dye from aqueous solutions

ABSTRACT Six new semi-IPN hydrogels using 2-acrylamido-methylpropane-1-sulfonic acid (AMPS) and Gelatin at different ratios through redox polymerization were prepared. Methylene-bisacrylamide and glutaraldehyde were used as the crosslinking agents for AMPS and Gelatin, respectively. The hydrogels’ swelling ratios and surface morphologies were analyzed using SEM for characterization. Porosity and specific surface area using the Brunauer–Emmett–Teller technique. DSC and Tg were also used for the thermal analysis of the prepared hydrogels, which show trans-glass temperature (Tg) higher than their raw materials AMPS and Gelatin. The prepared hydrogels were used to eliminate the cationic dye MB from the water-based solutions with an initial concentration of 600 ppm. The study discovered that the N9 and N10 hydrogels were extremely effective at removing a certain dye from aqueous solutions with an optimum pH level of 11 and an optimum temperature of 65°C. Both N9 and N10 achieved high removal efficiencies, reaching equilibrium at 90 min, whereas the other hydrogels required 120 min. N9 performed slightly better at 1078.919 mg/g and N10 at 1057.404 mg/g. The adsorption behavior of the two hydrogels followed the Langmuir model. The hydrogels exhibited pseudo-second-order kinetics. The thermodynamic study cleared that the adsorption of MB dye was endothermic and spontaneous. Results also showed that the adsorption of dyes with hydrogels N9 and N10 is chemisorption in nature. Desorption studies were conducted using 0.1 M HCl and NaOH. HCl was found to be the best eluent for dye recovery.

Rich active sites ZIF-8 base on imidazole-based deep eutectic solvents for rapid adsorption of acid fuchsin and competitive adsorption

MimDES-ZIF-8 with rich active sites as positive charges and metal coordination sites were prepared based on imidazole based deep eutectic solvent (MimDES) using interface permeation method. 2-Methylimidazole (2-Mim) simultaneously acted as a hydrogen bond acceptor (HBA) in MimDES (hydrogen donner was 1,6-hexanediol) and an organic ligand in MimDES-ZIF-8, affecting the coordination of ZIF-8 during permeation. Four different zinc salt solutions (ZnCl2, Zn(NO3)2·6H2O, Zn(OAc)2·2H2O, ZnSO4·7H2O) were permeated into MimDES to obtain MimDES-ZIF-8 with different morphologies. All MimDES-ZIF-8 had higher Zn/N ration (>0.25), specific surface area and surface positive charges. The dye adsorption results indicated that MimDES-ZIF-8 showed high adsorption efficiencies for acid fuchsin (all exceeded 97.75 % under pH 7.5) and a fast adsorption rate (exceeding 93 % in 5 min and reaching equilibrium in 60 min). Among MimDES-ZIF-8, the adsorption capacity of ZIF-8-C was 4845.3 mg/g. After five cycles of adsorption, the AF removal efficiency of ZIF-8-C remained over 93.23 %. Moreover, ZIF-8-C also had good adsorption capacity for anionic dyes CR, cationic dyes MB and BB. The adsorption process aligned well with both the Langmuir model and the pseudo-second-order kinetic model. Based on FTIR, XPS, and electrostatic potential calculation, the adsorption mechanism was elucidated.

Synergistic enhancement of plasmon induced photocatalytic and photoelectrochemical performance on ZnWO4/Ag2O@Ag hybrid-heterostructures

A novel hybrid photocatalyst, ZnWO4/Ag2O@Ag heterostructure was synthesized using a simple one-pot microwave treatment with varying concentrations of silver. Physico-chemical characterization was performed to elucidate the synthesized nanohybrids' properties. The photocatalytic activity of both pristine and heterostructure samples was evaluated through the degradation of cationic MB dye. Among the varied Ag concentrations, the 9 % Ag-doped ZnWO4/Ag2O heterostructure exhibited superior degradation performance, with a degradation rate of 93 % achieved within 45 min, surpassing both other Ag concentrations (89 % (90 min) for 1 % Ag, 87 % (80 min) for 3 % Ag, 90 % (80 min) for 5 % Ag and 91 % (45 min) for 7 % Ag) and pristine ZnWO4 (91 % (90 min)) samples. This catalytic enhancement can be attributed to the formation of heterostructures, plasmon-induced absorption enhancement within specific wavelength ranges, and reduced charge recombination rates. UV–visible studies revealed Ag nanoparticles of various sizes in the heterostructures, supported by surface plasmon resonance (SPR) peaks at 480 and 550 nm, respectively. Trapping experiments indicated that •OH and •O2− were the active species in MB reduction for pure and heterostructure samples. Furthermore, the hybrid heterostructure samples exhibited high stability and reusability in photocatalytic degradation. These findings suggest that the ZnWO4/Ag2O heterostructure photocatalysts are promising candidates for environmental remediation applications.

Highly porous carbon with rich inherent groups for ultrahigh adsorption of organic dyes from wastewater

Activated carbon from renewable biomass or its waste to purify various dyeing wastewater from textile industry is highly desired. In this work, porous activated carbon was prepared by using silk waste as precursor via a simple one-step carbonization process. The obtained SWC-1-800 had ultrahigh adsorption for anionic dye AR73 and cationic dye MB owing to its ultrahigh specific surface area (2774 m2 g−1) and rich functional groups. SWC-1-800 had an increased adsorption capacity reaching 1310 and 928 mg g−1 for AR73 and MB respectively as the initial concentration up to 1000 mg L−1. Moreover, the adsorption capacity was stable under a wide range of Na+ and SDS concentration. By adjusting the temperature and pH value, the maximum adsorption capacity reached 1337 and 1000 mg g−1 for AR73 and MB respectively, keeping the removal rate of AR73 and MB more than 80 % after 5 adsorption cycles. Besides, SWC-1-800 demonstrated quite good adsorption ability for many other kinds of dyes, which adsorption capacity as high as 1998 mg g−1 (Rh B). The adsorption mechanism was further proposed according to the structural characteristics, inherent functional groups and adsorption properties. Using silk waste-derived carbon to effectively absorb the harmful dyes in the wastewater shows dual value for cleaner production via a “waste-waste to clean products” model, which has great application potential in dyeing wastewater purification.

Surface‐Modified Mesoporous V2‐xSb2xO5‐δ Ceramics for Improving the Electrostatic Chemisorption of Methylene Blue

AbstractHerein, mesoporous V2‐xSb2xO5‐δ (Sb−V−O) compounds, encompassing a compositional range of x varying between, 0.05≤x≤0.08, with orthorhombic Pmmn space group symmetry, are synthesized by high‐temperature solid‐state reaction method. Scanning electron microscopy indicated the formation of microscale rods and flakes and EDS spectra affirmed the stoichiometric precision of their composition adhering to the formulated chemical formula. Nitrogen adsorption isotherms exhibited the distinctive type IV pattern, accompanied by an H3 hysteresis loop, signifying the formation of mesoporous micro rods and flakes. Brunauer‐Emmett‐Teller measurements demonstrated an augmented surface area, ranging from 16.67–28.74 m2/g, mirroring the effect of the increase in the concentration of Sb cations. The study demonstrated complete Methylene Blue dye removal within a brief 90 minute period, highlighting its efficacy in water remediation. The adsorption kinetics was aptly described by the pseudo‐second‐order model which exhibited a high degree of fit (R2=0.99). Freundlich adsorption isotherm was used to describe the multilayer adsorption of MB dye on the Sb−V−O surface indicating an exponential increase in adsorption active sites. Enhanced cationic MB dye adsorption on negative Sb−V−O surface is attributed to the electrostatic chemisorption by the interaction of NMe2+ on the negative surface modified Sb−V−O compounds.

Green synthesis of carbon quantum dots from teak leaves biomass for in situ precipitation and regenerative-removal of methylene blue-dye.

The objective of this study was to completely eliminate environmentally harmful cationic organic dye from aqueous solutions using the one-step ultrasonication method, renowned for its energy efficiency, user-friendliness, and minimal requirement for chemical resources, making it particularly suitable for large-scale applications. To achieve effective environmental remediation, we employed carbon dots derived from teak leaf biomass (TBCDs) layered with graphene oxide. We conducted a thorough characterization of the TBCDs using UV-vis spectroscopy (with absorption peaks at λmax = 208 and 276nm), FTIR spectroscopy (confirming the presence of various functional groups including -OH, -CH, C = O, COO-, C-O-C, and = C-H), Raman spectroscopy (with bands at 1369cm-1 (D-Band) and 1550cm-1 (G-Band), and an intensity ratio (ID/IG) = 0.88, indicating structural defects correlated with the sp3 hybridization sites on the TBCDs), XRD analysis (indicating an amorphous nature of particles), HRTEM imaging (showing homogeneous dispersal of TBCDs with typical sizes ranging from 2 to 10nm), FESEM analysis (showing a flat surface and minuscule particles), and Zeta potential analysis (revealing a surface charge peak at -51.0mV). Our adsorption experiments yielded significant results, with a substantial 50.1 % removal rate and an impressive adsorption capacity of 735.2mg g-1. Theoretical adsorption parameters were rigorously analyzed to understand the adsorption behavior, surface interactions, and mechanisms. Among these models, the Langmuir isotherm in conjunction with pseudo-second-order kinetics provided an exceptional fit (with R2 values closer to 1) for our system. The Gibbs free energy (ΔG) was found to be negative at all temperatures, indicating the spontaneity of the reaction. Regarding mechanism, electrostatic attraction ((+ve) MB dye + (- ve) TBCDs), π-π stacking adsorption facilitated by the graphitic structure, formation of multiple hydrogen bonds due to polar functional groups, and a pore-filling mechanism wherein the cationic MB dye fills the pores of TBCDs with graphene oxide layers, forming an adduct were identified. Furthermore, we demonstrated the regenerative capacity of our system by effectively extracting and recovering the MB dye (with a regeneration rate of 77.1%), utilizing ethyl alcohol as the solvent. These findings not only provide valuable insights into the adsorption capabilities of TBCDs but also highlight the potential of our approach in the recovery of expensive cationic organic dye compounds from polluted environments.

Surface parametric influences on the photocatalytic behaviour of zinc oxide nanoparticles

Zinc oxide nanoparticles were chemically synthesised and characterised by UV-DRS spectroscopy, FTIR, scanning electron microscopy with energy-dispersive X-ray diffraction, and X-ray powder diffraction. In order to evaluate the impact of the synthesis process on the structural parameters, Rietveld refinement was done using the GSAS-II programme on experimentally acquired XRD data. ZnO was found to have a hexagonal structure with lattice parameters of a = b =3.247 Å; c = 5.205Å and an average size of about 20-40 nm, as determined by Rietveld refinement of XRD and SEM data. FTIR and EDX analysis was used to confirm the functional group and elemental composition of ZnO NPs. The UV-DRS spectra revealed that the synthesised ZnO had an optical band gap of 3.05 eV. Parametric investigations of the surface morphology of ZnO nanostructures were conducted using the Gwyddion programme. Pseudo-first-order rate kinetics were observed for the photodegradation of two cationic dyes, MB (87.87%) and RhB (74.79%), in the presence of UV light.

Multifunctional In-MOF and Its S-Scheme Heterojunction toward Pollutant Decontamination via Fluorescence Detection, Physical Adsorption, and Photocatalytic REDOX.

A novel doubly interpenetrated indium-organic framework of 1 has been assembled by In3+ ions and highly conjugated biquinoline carboxylate-based bitopic connectors (H2L). The isolated 1 exhibits an anionic framework possessing channel-type apertures repleted with exposed quinoline N atoms and carboxyl O atoms. Owing to the unique architecture, 1 displays a durable photoluminescence effect and fluorescence quenching sensing toward CrO42-, Cr2O72-, and Cu2+ ions with reliable selectivity and anti-interference properties, fairly high detection sensitivity, and rather low detection limits. Ligand-to-ligand charge transition (LLCT) was identified as the essential cause of luminescence by modeling the ground state and excited states of 1 using DFT and TD-DFT. In addition, the negatively charged framework has the ability to rapidly capture single cationic MB, BR14, or BY24 and their mixture, including the talent to trap MB from the (MB + MO) system with high selectivity. Moreover, intrinsic light absorption capacity and band structure feature endow 1 with effective photocatalytic decomposition ability toward reactive dyes RR2 and RB13 under ultraviolet light. Notably, after further polishing the band structure state of 1 by constructing the S-scheme heterojunction of In2S3/1, highly efficient photocatalytic detoxification of Cr(VI) and degradation of reactive dyes have been fully achieved under visible light. This finding may open a new avenue for designing novel multifunctional MOF-based platforms to address some intractable environmental issues, i.e., detection of heavy metal ions, physical capture of pony-sized dyes, and photochemical decontamination of ultrastubborn reactive dyes and highly toxic Cr(VI) ions from water.

Simultaneous removal of anionic and cationic dyes on quaternary mixtures by adsorption onto banana, orange and pomegranate peels

Disposal of untreated wastewater released by industries using dyes, causes serious damage to aquatic life and to the ecosystem in general. Both physical and chemical methods have been used for the removal of these dyes from wastewater; among them, adsorption has been found to be a very efficient technique. In this study, the ability to simultaneously remove cationic (MB) and anionic dyes (RR120, RB5 and RBBR) from a quaternary mixture solution by using zero-cost materials as banana, orange and pomegranate peels, was investigated. The optimal removal rates were achieved at pH 2.0 and a dose of 6.0 g/L. The comparative results of natural adsorbents on dye removal, separately and simultaneously in solution showed that MB adsorption on banana and orange peels was augmented from 89 to 96 and 43 to 87%, respectively, in the presence of anionic dyes (synergistic effect). On the other hand, a competitive effect was determined, mainly between anionic dyes, resulting in a decrease in their respective percentage. Banana peels were selected as the adsorbent material for further study in a quaternary dye mixture containing all dyes. Parameters affecting dye adsorption such as pH solution, initial concentration of dyes, contact time and temperature were examined. Based on the experimental results, two mechanisms for interactions were proposed: (a) the cationic MB molecules are connected to the negatively charged anionic dyes or (b) electrostatic attractions occurred among cationic MB molecules and negatively charged anionic dyes in the solution enhancing the adsorption efficiency. Kinetic experiments showed that equilibrium for anionic dyes reached at around 180 min (3 h), and for MB was reached much faster, at 30 min; 87% of 20 mg/L was found to be removed in just 5 min. Langmuir isotherm model and pseudo-second-order kinetic model were best fitted to the experimental results. According to thermodynamics the spontaneous nature of their adsorption was confirmed.

Potential antibacterial, antibiofilm, and photocatalytic performance of gamma-irradiated novel nanocomposite for enhanced disinfection applications with an investigated reaction mechanism

BackgroundWater scarcity is now a global challenge due to the population growth and the limited amount of available potable water. In addition, modern industrialization, and microbial pathogenesis is resulting in water pollution on a large scale.MethodsIn the present study, reusable Co0.5Ni0.5Fe2O4/SiO2/TiO2 composite matrix was incorporated with CdS NPs to develop an efficient photocatalyst, and antimicrobial agents for wastewater treatment, and disinfection purpose. The antibacterial performance of the gamma-irradiated samples was evaluated against various types of Gram-positive bacteria using ZOI, MIC, antibiofilm, and effect of UV-exposure. Antibacterial reaction mechanism was assessed by bacterial membrane leakage assay, and SEM imaging. In addition, their photocatalytic efficiency was tested against MB cationic dye as a typical water organic pollutant.ResultsOur results showed that, the formed CdS NPs were uniformly distributed onto the surface of the nanocomposite matrix. While, the resulted CdS-based nanocomposite possessed an average particle size of nearly 90.6 nm. The antibacterial performance of the prepared nanocomposite was significantly increased after activation with gamma and UV irradiations. The improved antibacterial performance was mainly due to the synergistic effect of both TiO2 and CdS NPs; whereas, the highest photocatalytic efficiency of MB removal was exhibited in alkaline media due to the electrostatic attraction between the cationic MB and the negatively-charged samples. In addition, the constructed heterojunction enabled better charge separation and increased the lifetime of the photogenerated charge carriers.ConclusionOur results can pave the way towards the development of efficient photocatalysts for wastewater treatment and promising antibacterial agents for disinfection applications.

Highly sensitive detection of cationic pollutants on molybdenum carbide (MXene)/Fe2O3/Ag as a SERS substrate

Recent studies reported that the two-dimensional transition-metal carbides (MXenes) present promising results for surface-enhanced Raman spectroscopy (SERS) application, permitting sensitive detection of analyte molecules thanks to rich surface chemistries, surface plasmon resonances, and electrical features. However, Mxene materials, especially Mo-based ones, still suffer from low concentrated sensing activity and lack specific sensing suited to surface chemistries. To overcome those issues, for the first time, we propose a simple and scalable approach to fabricate Mo2CTx/Fe2O3/Ag (MFA) hybrid nanostructure via the hydrothermal treatment of MXene and Fe2O3, and subsequent in-situ decorated of Ag NPs via seed-mediated growth processes. As-prepared MFA presents a 1 × 10−9 M detection limit with a 1.46 × 106 enhancement factor for cationic MB molecules. Here, in addition to the contribution of the electromagnetic enhancement mechanism due to the presence of Ag, the chemical enhancement mechanism also comes into play as a result of the specific binding of the cationic molecule, MB, to the negatively charged MXene surface. This result is also observed for harmful cationic molecules found in wastewater such as CTAC and arsenic. MFA exhibits a low detection limit for CTAB, where a very low concentration of 0.075 M was achieved probably owing to its cationic character. Last but not least, the MFA hybrid nanostructure shows promising results for arsenic detection in tap water with 10 μg/L. Overall, an as-prepared MFA is a promising option for creating a SERS-active surface that can be customized for particular uses, due to its adjustable surface chemistries and elevated charge carrier densities, while also being low-cost and simple to manufacture.

Zinc nanoparticles encapsulated in porous biopolymer beads for reduction of water pollutants and antimicrobial activity

This work focuses on the preparation of composite beads from alginate crosslinked with copper at several loading percent and also loaded with ZnNPs. Th obtained samples were applied as catalysts for the reduction of the organic polluants 4-NP, MB, OG, MO, and CR in simple and binary systems. XRD results and TEM images confirmed the presence of ZnNPs in the polymer matrix. XRF and TGA analysis showed that the percentage of the cross-linking agent significantly influences the content of ZnNPs as well as the thermal stability of the resulting material. The catalytic activity of the composite beads showed that the Cu(4 %)-ALG(ZnNPs) sample was the best catalyst for all pollutants. In the simple system, the recorded rate constants for MB, MO, 4-NP, OG, and CR were 0.0133 s−1, 0.0076 s−1, 0.005 s−1, 0.0042 s−1, 0.0036 s−1, respectively. The catalyst was more selective towards the cationic MB dye for binary systems. For antibacterial and antifungal applications, the different materials containing ZnNPs and their counterparts containing Zn2+ were found to be active across all bacterial strains (Gram positive and Gram negative) as well as fungi, and the Zn2+-containing composites in particular performed better across all bacteria and fungi.

Synergetic benefits of microfluidics using artificial cilia and ZnO/SnFe2O4 for the degradation of pollutants

Water pollution due to the discharge of organic dye pollutants is a significant environmental concern. To mitigate this environmental threat, microfluidic devices are employed as a promising platform that provides innovative methods and perspectives in achieving effective environmental remediation. Meanwhile, the hydrodynamics of the fluid flow inside such miniaturized systems can also play a crucial role in the pollutant eradication process that can further establish a reliable framework for accomplishing the most promising treatment strategies. Herein, the microfluidic device comprised of ZnO/SnFe2O4 nanoparticles and artificial cilia was proposed to incorporate two essential functions in adequately adsorbing the cationic dye (methylene blue, MB) suspended in the aqueous medium. Amongst these, the employed ZnO/SnFe2O4 nanoparticles acted as an active adsorbent site. Eventually, the cationic MB dye was found to be adsorbed by these nanoparticles due to the presence of a negative surface charge potential. Further, to enhance this adsorption process, the employed artificial cilia were magnetically controlled to exhibit a tilted conical asymmetric motion. Consequently, such dynamic motion of the cilia was observed to enhance the hydrodynamics aspect of the dye-aqueous solution. Essentially, the rate of mass transfer of the dye-aqueous solution toward the absorbent site was improved. Thus, the dye-adsorption efficiency achieved through the proposed synergetic platform was estimated to be 90.2% at the end of 30 min. In comparison with the conventional motions of the artificial cilia, this obtained result with the actuated dynamic motion was found to be enhanced by 12.1%. Further, to aid an efficient adsorption process through the hydrodynamic principles, a flow visualization measurement was performed to identify the optimal design parameters of artificial cilia. Eventually, the spatial representative parameters of artificial cilia were observed to significantly influence the dye-adsorption behavior. The attained expertise from this study will be potentially advantageous for future dye treatment applications in designing several other distinct synergetic components for effective pollutant removal.

PH-sensitive cellulose/chitin nanofibrillar hydrogel for dye pollutant removal

In this study, a pH-sensitive smart hydrogel was successfully prepared by combining a polyelectrolyte complex using biopolymeric nanofibrils. By adding a green citric acid cross-linking agent to the formed chitin and cellulose-derived nanofibrillar polyelectrolytic complex, a hydrogel with excellent structural stability could be prepared even in a water environment, and all processes were conducted in an aqueous system. The prepared biopolymeric nanofibrillar hydrogel not only enables rapid conversion of swelling degree and surface charge according to pH but can also effectively remove ionic contaminants. The ionic dye removal capacity was 372.0 mg/g for anionic AO and 140.5 mg/g for cationic MB. The surface charge conversion ability according to pH could be easily applied to the desorption of the removed contaminants, and as a result, it showed an excellent contaminant removal efficiency of 95.1 % or more even in the repeated reuse process 5 times. Overall, the eco-friendly biopolymeric nanofibrillar pH-sensitive hydrogel shows potential for complex wastewater treatment and long-term use.

Low-pressure carbon nanotube membrane with different surface properties for the removal of organic dyes and PPCPs

Low-pressure carbon nanotube membranes (CNT membranes) was prepared with multi-walled carbon nanotubes (MWCNTs), carboxyl functionalized MWCNTs (COOH-MWCNTs) and single-walled carbon nanotubes (SWCNTs). Surface properties of MWCNTs and SWCNTs were further altered by their non-covalent functionalization with Humic acid (HA), Sodium dodecyl sulfate (SDS), Sodium alginate (SA) and Polyethylene glycol (PEG). The CNT membranes with different surface properties were then used for the removal of organic dyes and pharmaceuticals and personal care products (PPCPs). The results revealed that HA/SDS/SA non-covalent functionalized MWCNTs membrane significantly promoted the removal of cationic dye MB, while it slightly interfered the removal of anionic dye RB19. During the dynamic filtration process, a 20∼30% increase of MB removal was promoted by HA/SDS/SA-MWCNTs membrane compared with the MWCNTs membrane, while the HA/SDS/SA-MWCNTs membrane significantly deteriorated the removal of PPCPs. The specific surface area of CNTs played a very important role in the dynamic filtration process of CNT membranes. The removal rate of PPCPs by SWCNTs membranes was almost all above 70% after 120 min’s filtration, and a further 10% increase was promoted by SA-SWCNTs membrane. HA and SDS non-covalent functionalization only slightly deteriorate the removal of PPCPs, and the removal rate of majority of PPCPs by HA-SWCNTs membrane and SDS-SWCNTs membrane remained over 60% and 30%. This work present new insight for the effectiveness of low-pressure CNT membranes in actual application, where the impact of competitive background organic materials on the removal of Low-MW organic pollutants were sometimes overestimated.

Rapid, Highly-Efficient and Selective Removal of Anionic and Cationic Dyes from Wastewater Using Hollow Polyelectrolyte Microcapsules

Herein, poly (allylamine hydrochloride) (PAH)/ poly (styrene sulfonic acid) sodium salt (PSS) microcapsules of (PAH/PSS)2PAH (P2P MCs) and (PAH/PSS)2 (P2 MCs) were obtained by a layer-by-layer method. The P2 MCs show high adsorption capacity for Rhodamine B (642.26 mg/g) and methylene blue (909.25 mg/g), with an extremely low equilibrium adsorption time (~20 min). The P2P MCs exhibited high adsorption capacities of reactive orange K-G (ROKG) and direct yellow 5G (DY5G) which were 404.79 and 451.56 mg/g. Adsorption processes of all dyes onto microcapsules were best described by the Langmuir isotherm model and a pseudo-second-order kinetic model. In addition, the P2P MCs loaded with reactive dyes (P2P-ROKG), could further adsorb rhodamine B (RhB) dye, and P2 MCs that had adsorbed cationic MB dyes could also be used for secondary adsorption treatment of direct dye waste-water, respectively. The present work confirmed that P2P and P2 MCs were expected to become an excellent adsorbent in the water treatment industry.

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.

Preparation of Ag@AgCl/GO Material with Efficient Visible-Light Photocatalytic Performance

Ag@AgCl/GO was prepared by chemical coupling, in-situ deposition of supported AgCl, and photoreduction. The morphology, structure, and surface area of the prepared Ag@AgCl/GO were characterized by SEM, TEM, FT-IR, Raman spectra, and BET. The optical properties of the photocatalyst were analyzed by PL and UV-Vis DRS, respectively. The surface electrical properties and degradation stability were evaluated by zeta potential measurement and cyclic catalytic degradation experiments, and the photocatalytic mechanism was proposed in detail based on the ESR test and trapping experiment. The results showed that Ag@AgCl nanoparticles were spherical and cluster distributed on the folded structure of GO. The prepared Ag@AgCl/GO had good adsorption performance and photocatalytic degradation stability. The material showed good visible light catalytic performance; especially, the degradation rates of cationic dyes RhB and MB were significantly higher than those of anionic dyes MO and CR, and their degradation processes were in line with the quasi-first-order reaction kinetics. Holes (h+) and superoxide radicals (·O2－) were the main active species for the degradation of RhB.

Interfacial coupling effects in α-Fe2O3/g-C3N4 composite magnetically separable heterojunction with upgraded Z-scheme photocatalytic performance of mixed organic pollutant degradation

Photocatalysis has fascinated wide consideration due to its promising advantage in wastewater treatment. And the metal-oxides and g-C3N4 that possess Z-scheme heterojunctions have become the energetic photocatalysts (PCs) in degrading the organic impurities. In this work, a novel magnetic separable g-C3N4/α-Fe2O3 (GFE) nanocomposites (NCs) were fabricated by a facile hydrothermal strategy. Structural, morphological, optical, surface area and magnetic belongings of GFE composites were effectively explored using XRD, FT-IR, XPS, FESEM, HRTEM with EDX mapping, BET, UV-DRS and PL spectra. The (g-C3N4/20 wt % α-Fe2O3) GFE2 composite PCs were verified robust with significantly upgraded the photocatalytic efficiency for (anionic) RhB (97.2%) and (cationic) MB (90.6%) mixed aqueous organic pollutants degradation in 150 min under visible-light exposure, which was favourably higher than to GCN (65.2%) and α-Fe2O3 (16.6%) PCs. Moreover, the as-obtained GFE composite PCs also exposed great stability after five successive recyclabilities. The enhanced photo-degradation activity was largely ascribed to the extended visible-light fascination ability, high surface area, augmented active sites and strong redox ability relatively. Also, the energetic formation of α-Fe2O3 coupled g-C3N4 heterojunction that skilled the probable recombination rate and beneficial for the separation of photo-excited electron and hole (e−/h+) pairs based on active “Z-scheme” mechanism was liable for eliminating organic mixed pollutants.