Valorization of sugarcane bagasse with in situ grown MoS2 for continuous pollutant remediation and microbial decontamination

In this study, sugarcane bagasse (SB) was strategically subjected to a delignification process followed by the in situ growth of multi-layered molybdenum disulfide (MoS2) nanosheets with hexagonal phase (2H-phase) crystal structure via hydrothermal treatment. The MoS2 nanosheets underwent self-assembly to form nanoflower-like structures in the aligned cellulose inter-channels of delignified sugarcane bagasse (DSB), the mechanism of which was understood through FTIR and XPS spectroscopic studies. DSB, due to its porous morphology and abundant hydroxyl groups, shows remediation capabilities of methylene blue (MB) dye through physio-sorption but shows a low adsorption capacity of 80.21 mg/g. To improve the removal capacity, DSB after in situ growth of MoS2 (DSB-MoS2) shows enhanced dye degradation to 114.3 mg/g (in the dark) which further improved to 158.74 mg/g during photodegradation, due to catalytically active MoS2. Interestingly, DSB-MoS2 was capable of continuous dye degradation with recyclability for three cycles, reaching an efficiency of > 83%, along with a strong antibacterial response against Gram-positive Staphylococcus aureus (S.aureus) and Gram-negative Escherichia coli (E. coli). The present study introduces a unique strategy for the up-conversion of agricultural biomass into value-added bio-adsorbents, which can effectively and economically address the remediation of dyes with simultaneous microbial decontamination from polluted wastewater streams.

Sustainable removal of hexavalent chromium using graphene oxide - Iron oxide reinforced pectin/polyvinyl alcohol magnetic gel beads

The study investigated removal of hexavalent chromium Cr (VI) from aqueous solution using graphene oxide‑iron oxide reinforced pectin/polyvinyl alcohol magnetic gel beads prepared through co-precipitation and freeze-drying technique. Scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, N2 adsorption-desorption isotherm, and zeta potential are used for characterization. The surface area of magnetic gel beads calculated by BET method was determined to be 100.95 m2/g, significantly higher than that of GO and GO-Fe3O4. The optimum removal efficiency of GO-Fe3O4/Pec/PVA was assessed by batch method at variables such as pH(1-6), adsorption time(0-180 min), and temperature(25-35 °C). Accordingly, 0.2 g GO-Fe3O4/Pec/PVA dose, pH 2, contact time: 120 min at 25 °C were found to be the optimal conditions, and maximum adsorption capacity of GO, GO-Fe3O4 and GO-Fe3O4/Pec/PVA toward Cr(VI) removal was found to be 39.5, 62.5 and 78.55 mg g-1, respectively. Kinetic and isotherm studies indicate adsorption data follow pseudo-second-order kinetic and Langmuir isotherm models. Thermodynamic studies showed adsorption capacities of adsorbents decreased when temperature increased which indicated adsorption for Cr (VI) was an exothermic process. The activation energies were found to be 34.92, 26.57, and 35.23 KJ mol-1 for GO, GO-Fe3O4, and GO-Fe3O4/Pec/PVA, respectively, which illustrated adsorption of Cr(VI) onto the surface of adsorbents was a physical process. The beads exhibit excellent recoverability and reusability over five cycles. Overall, GO-Fe3O4/Pec/PVA demonstrates exceptional adsorption properties and can serve as an efficient, stable, less toxic, and magnetically separable adsorbent for removal of Cr(VI) from aqueous solution.

Use of transition metal dichalcogenides (TMDs) in analytical sample preparation applications

Since the discovery of graphene, nano-sized two-dimensional (2D) transition metal dichalcogenides (TMDs) such as MoS2, MoSe2, MoTe2, NbS2, NbSe2, WS2, WSe2, TaS2 and TaSe2, which have been classified as next-generation nanomaterials resembling graphene (G) have complementary basic properties with those of graphene in terms of their practical applications. TMDs are attracting great attention due to their attractive physical, chemical and electronic properties. Despite being overshadowed by graphene in terms of frequency of use, TMDs have been used frequently in many areas in recent years instead of carbon-based materials such as graphene (G), graphene oxide (GO), carbon nanotubes (CNTs) and nanodiamonds (NDs). It is seen that the first and frequent uses of TMDs, which are classified as new generation materials, are in the fields of catalysis, electronic applications, hydrogen production processes and energy storage, but it has been used as an adsorbent in sample preparation techniques in recent years. Similar to graphene, layers of TMDs are held together by weak van der Waals interactions. The sandwiched layers of TMDs provide sufficient and effective interlayer spaces so that foreign molecules, ions and atoms can easily enter these spaces between the layers. Intermolecular interactions increase with the entry of different materials into these spaces, and thus, high activity, adsorption capacity and efficiency are obtained in adsorption-based analytical sample preparation methods. Although there are about 35 research articles using TMDs, which are classified as promising materials in analytical sample preparation techniques, no review studies have been found. This review, which was designed with this awareness, contains important informations on the properties of metal dichalcogenides, their production methods and their use in analytical sample preparation techniques.

Enhanced mechanical properties and biocompatibility of bacterial cellulose composite films with inclusion of 2D MoS2 and helical carbon nanotubes for use as antimicrobial drug carriers

Bacterial cellulose (BC) is a biomaterial being investigated for a range of applications. Herein, BC films derived from nata de coco pieces are reinforced by two-dimensional molybdenum disulfide (MoS2) and helical carbon nanotubes (HCNTs) to enhance their tensile mechanical properties, and the biocompatibility of the BC composite films is demonstrated. A simple preparation is presented using a kitchen blender to disperse and blend the BC fibers and additives in a common fabrication medium, followed by vacuum filtration. The mechanical properties of the BC/MoS2/HCNTs composite films are enhanced due to the synergistic effect of MoS2 and HCNTs embedded in the BC films. The MoS2/HCNTs binary additive (1 phr) is capable of increasing the strength and Young's modulus by 148 % and 333 %, respectively, relative to the BC films. The cell cytotoxicity of the BC/MoS2/HCNTs films was assessed using an MTT assay. The composite films are biocompatible with a cell viability of L929 fibroblast cells >70 %, coupled with observations of direct cell attachment on the films. The composite films also exhibited good performance in absorbing and releasing gentamicin antibiotics to inhibit the growth of Escherichia coli and Staphylococcus aureus. The BC/MoS2/HCNTs films are thus potential BC-based candidates as biocompatible robust antibiotic carriers.

Facile Synthesis of ZnS/1T-2H MoS2nanocomposite for Boosted adsorption/photocatalytic degradation of methylene blue under visiblelight

Facile solvothermal techniques were used to manufacture ZnS/1T-2H MoS₂ nanocomposite (ZMS) with outstanding adsorption-photocatalytic activity. The formed catalyst was characterized by different tools; XRD, HR-TEM, EDX, FTIR, Raman, N₂adsorprion/desorption, Zeta potential, PL,and XPS. The analysis provided the formation on mixed phase of metallic 1Tand 2H phases. ZMS has a high porosity and large specific surface area, and it has a high synergistic adsorption-photocatalytic degradation effect for MB, with a removal efficiency of ≈100% in 45 minutes under visible light irradiation. The extraordinary MB removal efficiency of ZMS was attributed not only to the high specific surface area (49.15 m²/g) and precious reactive sites generated by ZMS, but also to the formation of 1T and 2H phases if compared to pristine MoS₂ (MS). The best adsorption affinity was induced by the existance of 1T phase. The remarkably enhanced photocatalytic activity of ZMS nanocomposite can be ascribed to the 2D heterostructure which enhances the adsorption for pollutants, provides abundant reaction active sites, extends the photoresponse to visible light region.

High-Efficient Anionic Dyes Removal from Water by Cationic Polymer Brush Functionalized Magnetic Mesoporous Silica Nanoparticles

High efficiency removal of methyl orange (MO) and bromothymol blue (BT) dyes from contaminated water has been reported using magnetic mesoporous nanoparticles modified with cationic polymer brush (poly(2-methacryloyloxy)ethyl] trimethylammonium chloride solution) (Fe3O4-MSNs-PMETAC). Atom transfer radical polymerization (ATRP) was utilized to grow the polymer chains on the magnetic mesoporous silica nanoparticles. The chemical surface modifications were confirmed using IR, TGA, SEM and TEM. The results show that the obtained Fe3O4-MSNs-PMETAC materials were nearly spherical in shape with approximately 30 nm magnetic core, and silica shell thicknesses ranged from 135 to 250 nm. The adsorption performance of the material was found to be unaffected by the pH (3-9) of the media, with a removal efficiency of 100% for both dyes. The adsorption of BT and MO on the surface of Fe3O4-MSNs-PMETAC was found to follow Freundlich and Langmuir models, respectively. Since the synthesized nanocomposite materials exhibit an enhanced properties such as large maximum adsorption capacity, rapid synthesis process, and easy separation from solution, it could be an effective sorbent for the removal of other pollutants such as potentially toxic anionic elements (e.g., arsenate and chromate ions) from water and wastewater.

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

Quaternization of Poly(2-diethyl aminoethyl methacrylate) Brush-Grafted Magnetic Mesoporous Nanoparticles Using 2-Iodoethanol for Removing Anionic Dyes

Magnetic mesoporous silica nanoparticles (Fe3O4-MSNs) were successfully synthesized with a relatively high surface area of 568 m2g−1. Fe3O4-MSNs were then modified with poly(2-diethyl aminoethyl methacrylate) (PDEAEMA) brushes using surface-initiated ARGET atom transfer radical polymerization (ATRP) (Fe3O4@MSN-PDMAEMA). Since the charge of PDEAEMA is externally regulated by solution pH, tertiary amines in the polymer chains were quaternized using 2-iodoethanol to obtain cationic polymer chains with a permanent positive charge (Fe3O4@MSN-QPDMAEMA). The intensity of the C−O peak in the C1s X-ray photoelectron spectrum increased after reaction with 2-iodoethanol, suggesting that the quaternization process was successful. The applicability of the synthesized materials on the removal of methyl orange (MO), and sunset yellow (E110) dyes from an aqueous solution was examined. The effects of pH, contact time, and initial dyes concentrations on the removal performance were investigated by batch experiments. The results showed that the Fe3O4@MSN-PDMAEMA sample exhibited a weak adsorption performance toward both MO and E110, compared with Fe3O4@MSN-QPDMAEMA at a pH level above 5. The maximum adsorption capacities of MO and E110 using Fe3O4@MSN-QPDMAEMA were 294 mg g−1 and 194.8 mg g−1, respectively.

Water-soluble graphitic carbon nitride for clean environmental applications

The removal of halogenated dye and sensing of pharmaceutical products in the water bodies with quick purification time is of high need due to the scarcity of drinking water. The present work reported on the preparation of graphitic carbon nitride (g-C₃N₄) for quick time water contaminant adsorption, followed by synthesizing silver nanoparticles decorated graphitic carbon nitride for pharmaceutical product sensing using in-situ SERS technique. The prepared graphitic carbon nitride is used to study the adsorption behavior of water contaminants at room temperature, in the presence of methylene blue (MB) as an adsorbate model. The water-soluble graphitic carbon nitride, even at low concentration, possesses an excellent ability to adsorb halogenated organic dye. As a result, the dyes are found to adsorb within ∼5s even without any additional physical or chemical activation. From the UV-Vis absorption investigations, it has been perceived that in the presence of graphitic carbon nitride (g-C₃N₄) the dye adsorption efficacy is observed nearly 80% with the well fitted linearly of R² = 0.9731. Effective in-situ surface-enhanced Raman scattering (SERS) studies for Ag nanoparticles decorated graphitic carbon nitride has been carried out and the obtained result shows good sensing performance of the material towards acetaminophen drug. This method opens the possibility of the Nobel metal decorated graphitic carbon nitride for real-time sensing of SERS-based drug products along with the development of high-performance sensing of the target analyte in the future.

Solvothermal synthesis of poly(acrylic acid) decorated magnetic molybdenum disulfide nanosheets for highly-efficient adsorption of cationic dyes from aqueous solutions

Poly(acrylic acid) decorated magnetic MoS₂ nanosheets with high adsorption capacities for three cationic dyes have been successfully synthesized by a simple one-step solvothermal method.

Starch, cellulose, pectin, gum, alginate, chitin and chitosan derived (nano)materials for sustainable water treatment: A review

Natural biopolymers, polymeric organic molecules produced by living organisms and/or renewable resources, are considered greener, sustainable, and eco-friendly materials. Natural polysaccharides comprising cellulose, chitin/chitosan, starch, gum, alginate, and pectin are sustainable materials owing to their outstanding structural features, abundant availability, and nontoxicity, ease of modification, biocompatibility, and promissing potentials. Plentiful polysaccharides have been utilized for making assorted (nano)catalysts in recent years; fabrication of polysaccharides-supported metal/metal oxide (nano)materials is one of the effective strategies in nanotechnology. Water is one of the world's foremost environmental stress concerns. Nanomaterial-adorned polysaccharides-based entities have functioned as novel and more efficient (nano)catalysts or sorbents in eliminating an array of aqueous pollutants and contaminants, including ionic metals and organic/inorganic pollutants from wastewater. This review encompasses recent advancements, trends and challenges for natural biopolymers assembled from renewable resources for exploitation in the production of starch, cellulose, pectin, gum, alginate, chitin and chitosan-derived (nano)materials.

Co-modification of lignocellulosic biomass by maleic anhydride and ferric hydroxide for the highly efficient biosorption of methylene blue

Ferric hydroxide and microwave-assisted solvent-free esterification was applied in the modification of SBP to synthesize an efficient cationic dye adsorbent.