High-performance two-dimensional montmorillonite supported-poly(acrylamide-co-acrylic acid) hydrogel for dye removal

Construction of mechanically robust and recyclable catalytic hydrogel based on hydroxypropyl cellulose-supported by montmorillonite/ionic liquid with different anions for pollutants(4-NP, MB, CR, Rhb) degradation

Dye wastewater poses a serious threat to the environment and human health, necessitating sustainable degradation methods. In this study, Na-based Montmorillonite (MMT) was exfoliated using different ionic liquids ([C16MIM][Cl], [C16MIM][BF4], [C16MIM][PF6]), and silver nanoparticles (Ag NPs) were green-synthesized using hydroxypropyl cellulose (HPC). The HPC significantly enhanced the dispersion of MMT in the hydrogel. By introducing lauryl methacrylate (LMA), a hydrophobic associative network was constructed in PAM/LMA/HPC/MMT@ILs&Ag NPs hydrogel. This hydrogel demonstrated outstanding mechanical properties, with a stress of 833.21 kPa, strain of 3300 %, and toughness of 14.36 MJ/m3. It also exhibited excellent catalytic activity, with a rate constant of 0.83 min-1 for 4-nitrophenol degradation at 28 °C. The effects of temperature and catalyst concentration on the catalytic reaction were systematically investigated. This study presents a simple green synthesis approach for Ag NPs using HPC, achieving superior mechanical performance and stable MMT dispersion in aqueous solutions.

Immobilization of Horseradish Peroxidase onto Montmorillonite/Glucosamine-Chitosan Composite for Electrochemical Biosensing of Polyphenols

Glucosamine-chitosan synthesized by the Maillard reaction was combined with montmorillonite to obtain a nanohybrid composite to immobilize horseradish peroxidase. The material combines the advantageous properties of clay with those of the chitosan derivative; has improved water solubility and reduced molecular weight and viscosity; involves an eco-friendly synthesis; and exhibits ion exchange capacity, good adhesiveness, and a large specific surface area for enzyme adsorption. The physicochemical characteristics of the composite were analyzed by infrared spectroscopy and X-ray diffraction to determine clay-polycation interactions. The electrochemical response of the different polyphenols to glassy carbon electrodes modified with the composite was evaluated by cyclic voltammetry. The sensitivity and detection limit values obtained with the biosensor toward hydroquinone, chlorogenic acid, catechol, and resorcinol are (1.6 ± 0.2) × 102 µA mM-1 and (74 ± 8) nM; (1.2 ± 0.1) × 102 µA mM-1 and (26 ± 3) nM; (16 ± 2) µA mM-1 and (0.74 ± 0.09) μM; and (3.7± 0.3) µA mM-1 and (3.3 ± 0.2) μM, respectively. The biosensor was applied to quantify polyphenols in pennyroyal and lemon verbena extracts.

Comparison of Structural, Water-Retaining and Sorption Properties of Acrylamide-Based Hydrogels Cross-Linked by Physical and Chemical Methods

Two series of hydrogels based on acrylamide and its copolymers with acrylonitrile and acrylic acid were synthesized by two cross-linking methods - chemical (using N,N'-methylene bis-acrylamide) and physical (using montmorillonite (MMT)) ones. The structure of the gels was characterized by Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The swelling and sorption properties were analyzed as a function of both the monomer composition and the cross-linking method. The shift of the band corresponding to Si-O (995-1030 cm-1 ) confirmed the formation of intercalation structures for MMT-cross-linked gels. Moreover, physically cross-linked gels demonstrated a non-monotonic dependence of the swelling degree on the MMT concentration, and acrylamide-acrylic acid copolymer MMT-cross-linked gels showed pH sensitivity and the highest swelling degree of 150 g/g. The highest sorption capacity towards cadmium(II) ions was demonstrated by acrylamide-acrylic acid copolymer gels, both covalently cross-linked (30 mg/g) and MMT-cross-linked (8.9 mg/g).

Tetracycline decontamination from aqueous media using nanocomposite adsorbent based on starch-containing magnetic montmorillonite modified by ZIF-67

In the present study, starch/zeolitic imidazole framework-67 (ZIF-67) modified magnetic montmorillonite nanocomposite adsorbent to remove tetracycline (TC) as an emerging antibiotic-based contaminant from aqueous media. The surface properties of the adsorbents were investigated using FTIR, XRD, SEM, EDX-Map, XPS, TEM, BET, and VSM analysis. The specific surface area of MMT, St/MMT-MnFe2O4, and St/MMT-MnFe2O4-ZIF-67 magnetic nanocomposite samples were found to be 15.63, 20.54, and 588.41 m2/g, respectively. The influence of pH, adsorbent amount, initial TC concentration, temperature, contact time, and coexisting ions on TC elimination was explored in a batch adsorption system. The kinetic and equilibrium data were well matched with the pseudo-second-order and Langmuir isotherm models, respectively. The maximum monolayer adsorption capacities of TC were obtained to be 40.24, 66.1, and 135.2 mg/g by MMT, St/MMT-MnFe2O4, and St/MMT-MnFe2O4-ZIF-67 magnetic nanocomposite adsorbents, respectively. Also, thermodynamic studies illustrated that the TC adsorption process is exothermic and spontaneous. Furthermore, the magnetic nanocomposite adsorbent St/MMT-MnFe2O4-ZIF-67 showed good reusability and could be recycled for up to five cycles. This excellent adsorption performance, coupled with the facile separation of the magnetic nanocomposite, gave St/MMT-MnFe2O4-ZIF-67 a high potential for TC removal from aqueous media.

A novel double-network hydrogel made from electrolytic manganese slag and polyacrylic acid-polyacrylamide for removal of heavy metals in wastewater

Electrolytic manganese slag (EMS), a bulk waste generated in industrial electrolytic manganese production, can be a cost-effective adsorbent for heavy metals removal after appropriate modification. In this study, EMS was activated by NaOH and then used to make the EMS-based double-network hydrogel (an EMS/PAA hydrogel) via a one-pot method. The results showed that the EMS/PAA hydrogel exhibits a high selective adsorption capacity of 153.85, 113.63 and 54.35 mg·g-1 for Pb (II), Cd (II) and Cu (II), respectively. In addition, Density Functional Theory (DFT) suggests that the adsorption energies (Ead) of Pb, Cd and Cu on SiO2/PAA of the EMS/PAA gels are - 4.15, - 1.96, and - 2.83 eV, respectively, and SiO2/PAA, with a strong affinity to Pb2+, is one of the reasons for the selective adsorption capacity of EMS/PAA gel for Pb2+. The removal efficiency of the EMS/PAA gel for Pb2+, Cd2+, Cu2+ decreased after four adsorption-desorption cycles by 20.00 %, 24.56 % and 46.56 %, respectively. Mechanism studies suggested that the elimination of the heavy metals by EMS/PAA gels mainly involves electrostatic attraction, inner-sphere complexation, and coordination interactions. The EMS/PAA hydrogels not only have high adsorption capacity, but are also easy to prepare and circulate, making them ideal for practical applications.

Stretchable, Strong, Recyclable Helicide Elastomer Based on Dynamic Covalent Interactions

Current methods for making and disposing synthetic polymers have been widely pursued and are largely unsustainable. As a part of the solution, the reversible nature of dynamic covalent bonds emerges as an extraordinarily diverse and valuable feature in the development of exotic molecules and extended structures. With these bonds, it should be possible to construct recyclable and mechanically interlocked molecular structures using relatively simple precursors with preorganized geometries. A new helicide-based elastomer network is developed here with self-healing, recycling, and degradation features using a similar concept. The best self-healing performance (100%) was noted over 10-20 min, with various H2O, HCl, and NaOH solutions that delivered mechanical properties in the 1-1.4 MPa range. For hydrolytic degradation, the parameters are defined based on the type of binding, the pH of the solutions, and the copolymer network, which endowed a degradation time of approximately 4-11 h for each prepared sample. However, due to the reversible nature of the dynamic bonds, the material showed good recyclable mechanical properties compared to the pristine samples after five consecutive cycles, which meet the requirements of recyclable materials and recyclable packaging.

Polymeric hydrogels-based materials for wastewater treatment

Low-cost and reliable wastewater treatment is a relevant issue worldwide to reduce the concentration of environmental pollutants. Industrial effluents containing dyes, heavy metals, and other inorganic and organic compounds can pollute water resources; therefore, novel technologies are required to mitigate and control their release into the environment. Adsorption is one of the simplest methods for treating contaminated water in which a wide spectrum of adsorbents can be used to remove emerging compounds. Hydrogels are interesting materials with high adsorption capacities that can be synthesized via green routes. These adsorbents are promising for large-scale industrial wastewater treatment applications; however, gaps still exist in achieving sustainable commercial implementation. This review focuses on the discussion and analysis of preparation, characterization, and adsorption properties of hydrogels for water purification. The advantages of these polymeric materials for water treatment were analyzed, including their performance in the removal of different organic and inorganic contaminants. Recent advances in the functionalization of hydrogels and the synthesis of novel composites have also been described. The adsorption capacities of hydrogel-based adsorbents are higher than 500 mg/g for different organic and inorganic pollutants, and can reach values of up to >2000 mg/g for organic compounds, significantly outperforming other materials reported for water cleaning. The main interactions involved in the adsorption of water pollutants using hydrogel-based adsorbents were described and explained to allow the interpretation of their removal mechanisms. The current challenges in the implementation of hydrogels for water purification in real-life operations are also highlighted. This review provides an updated picture of hydrogels as interesting materials to address water depollution worldwide.

Efficient Photocatalytic Degradation of Methylene Blue Dye from Aqueous Solution with Cerium Oxide Nanoparticles and Graphene Oxide-Doped Polyacrylamide

A cerium oxide nanoparticles (CeO₂-NPs)/graphene oxide (GO)/polyacrylamide (PAM) ternary composite was synthesized through free-radical polymerization of acrylamide in the presence of CeO₂ nanoparticles and GO in an aqueous system. The synthesized composite material was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy techniques and applied for the photocatalytic degradation of methylene blue (MB) dye from an aqueous solution. Tauc's model for direct transition was used to model for the optical band gap. The key operating parameters such as the amounts of CeO₂-NPs and GO, pH, initial MB concentration, type of light irradiation, and contact time have been optimized to achieve the highest MB degradation percentage. The photocatalysis process was pH-dependent, and the optimum pH value was found to be 12.0. Under UV-A light, 90% dye degradation occurred in 90 min. The degradation of MB was also specified in terms of total organic carbon (TOC) and chemical oxygen demand (COD). Free-radical capture experiments were also performed to determine the role of radical species during the photocatalytic oxidation process. The photocatalytic process showed that the equilibrium data is in good agreement with the Langmuir-Hinshelwood kinetic model. A rate constant of 0.0259 min^-1 was obtained. The hydrogel was also tested to assess its reusability, which is an important key factor in practical wastewater treatment. The photocatalytic activity only decreased to 75% after nine uses.

Chitosan-induced self-assembly of montmorillonite nanosheets along the end-face for methylene blue removal from water

In this study, chitosan-induced self-assembly of montmorillonite nanosheets (MMTNS) along the end-face to form the layered and porous structured composite with high adsorption capacity towards MB dye wastewater was investigated. The self-assembly process was driven by the hydrogen-bond interaction among -OH groups distributed along the end-face of MMTNS and -NH₂ groups on chitosan (CS) chain, which finally formed the infinite two-dimensional lamellae. This technology remained the exposed adsorption sites on MMTNS surface, and solved the separation issue of spent MMTNS from water, making MMTNS/CS an excellent adsorption material for macromolecular MB dye. The maximum adsorption capacity of MMTNS/CS towards MB reached 243 mg/g, which was achieved via the Na⁺- exchange, hydrogen-bond and n-π stacking interactions with MB molecules. This work aimed at breaking through the bottleneck of small adsorption capacity of traditional MMT adsorbents, solving the problem of solid-liquid separation of nanosheets, and effectively reducing the adsorption cost, which might guide an important direction for adsorption material design and development in the future.

Bamboo Nanocellulose/Montmorillonite Nanosheets/Polyethyleneimine Gel Adsorbent for Methylene Blue and Cu(II) Removal from Aqueous Solutions

In recent years, the scarcity of pure water resources has received a lot of attention from society because of the increasing amount of pollution from industrial waste. It is very important to use low-cost adsorbents with high-adsorption performance to reduce water pollution. In this work, a gel adsorbent with a high-adsorption performance on methylene blue (MB) and Cu(II) was prepared from bamboo nanocellulose (BCNF) (derived from waste bamboo paper) and montmorillonite nanosheet (MMTNS) cross-linked by polyethyleneimine (PEI). The resulting gel adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), etc. The results indicated that the MB and Cu(II) adsorption capacities of the resulting gel adsorbent increased with the solution pH, contact time, initial concentration, and temperature before equilibrium. The adsorption processes of MB and Cu(II) fitted well with the fractal-like pseudo-second-order model. The maximal adsorption capacities on MB and Cu(II) calculated by the Sips model were 361.9 and 254.6 mg/g, respectively. The removal of MB and Cu(II) from aqueous solutions mainly included electrostatic attraction, ion exchange, hydrogen bonding interaction, etc. These results suggest that the resulting gel adsorbent is an ideal material for the removal of MB and Cu(II) from aqueous solutions.

Construction and Ion Transport-Related Applications of the Hydrogel-Based Membrane with 3D Nanochannels

Hydrogel is a type of crosslinked three-dimensional polymer network structure gel. It can swell and hold a large amount of water but does not dissolve. It is an excellent membrane material for ion transportation. As transport channels, the chemical structure of hydrogel can be regulated by molecular design, and its three-dimensional structure can be controlled according to the degree of crosslinking. In this review, our prime focus has been on ion transport-related applications based on hydrogel materials. We have briefly elaborated the origin and source of hydrogel materials and summarized the crosslinking mechanisms involved in matrix network construction and the different spatial network structures. Hydrogel structure and the remarkable performance features such as microporosity, ion carrying capability, water holding capacity, and responsiveness to stimuli such as pH, light, temperature, electricity, and magnetic field are discussed. Moreover, emphasis has been made on the application of hydrogels in water purification, energy storage, sensing, and salinity gradient energy conversion. Finally, the prospects and challenges related to hydrogel fabrication and applications are summarized.

Safranin-O cationic dye removal from wastewater using carboxymethyl cellulose-grafted-poly(acrylic acid-co-itaconic acid) nanocomposite hydrogel

Copolymer of acrylic acid (AA) and itaconic acid (IA) grafted onto sodium carboxymethyl cellulose hydrogel (CMC-g-poly (AA-co-IA)) was successfully synthesized as an adsorbent to remove safranin-O from wastewater. The swelling and removal efficiencies of CMC-g-poly (AA-co-IA) were enhanced by increasing IA/AA molar ratio as well as by incorporation of montmorillonite clay nano-sheets (MMT). The surface area of MMT, CMC-g-poly (AA-co-IA), and CMC-g-poly (AA-co-IA) samples was 15.632, 0.61452, and 0.66584 m²/g, respectively, indicating the effectiveness of MMT nano-sheets in improving hydrogel surface area. The maximum removal efficiency of CMC-g-poly (AA-co-IA)/MMT under optimum conditions i.e., pH of 8, initial concentration of 10 mg/L, adsorbent dose of 2 g/L, and contact time of 40 min was ascertained 99.78% using a response surface methodology-central composite design (RSM-CCD). Pseudo-second-order and Langmuir models giving the maximum monolayer adsorption capacity of 18.5185 mg/g and 19.1205 mg/g for CMC-g-poly (AA-co-IA) and CMC-g-poly (AA-co-IA)/MMT samples, respectively are the best-fitted models for kinetic and equilibrium data. Thermodynamically, safranin-O decontamination was spontaneous, exothermic, and entropy decreasing. Moreover, ad (de)sorption behavior study showed that CMC-g-poly (AA-co-IA)/MMT performance was not changed after multiple recovery steps. Therefore, CMC-g-poly (AA-co-IA)/MMT was considered as a highly potential adsorbent for safranin-O removal from wastewater.

α-Amino Phosphonic Acid as the Oxidized Ore Collector: Flexible Intra-Molecular Proton Transfer Providing an Improved Flotation Efficiency

The efficient separation of ilmenite is a difficult problem in minerals flotation. For this issue, α-aminooctyl phosphinic acid (APA) was developed as a selective collector to separate ilmenite. The flotation test result showed that APA was more efficient for improving ilmenite recovery compared with octylphosphonic acid (OPA). Adsorption, ZETA and FTIR measurements proved that the chemical interaction between collector APA and the surface of ilmenite was stronger than OPA, while the result is completely opposite in the case of titanaugite. Moreover, XPS test and DFT calculations indicated that the collector APA was coordinated with the surface of ilmenite through P-O-Fe and P-O-Ti bonding. The amine group in the α-site of the phosphonyl group facilitated APA to be a stable zwitterion in the solution, which greatly enhanced the nucleophilicity of the phosphonic acid group. On the other hand, more appropriate coordination energy was another reason for the superior collecting selectivity of APA than OPA.

Inclusion of organic species in exfoliated montmorillonite nanolayers towards hierarchical functional inorganic-organic nanostructures

Montmorillonite (Mt) can readily undergo spontaneous delamination or exfoliation into nanolayers by various physical and chemical processes, which allow various strategies to engineer hierarchical functional inorganic-organic nanostructures. This review aims to discuss the recent progress in the liquid-phase exfoliation of Mt into individual nanolayers and the inclusion chemistry of functional organic species, ions, or molecules into the exfoliated Mt nanolayers to produce hierarchical functional inorganic-organic nanostructures. The exfoliation methods include mechanical force, ultrasonication, and intercalation-assisted exfoliation. Techniques for quickly assessing the quality of the exfoliated Mt nanolayers are still needed. Layer-by-layer (LbL) deposition, template, and evaporation-induced inclusions are examined to fabricate hierarchical Mt-organic species nanocomposites with unique functionalities and properties. The nanocomposites can be produced as multilayered porous films, brick-and-mortar coatings, hydrogels with a house-of-cards structure, core-shell materials, and hollow and mesoporous spherical nanocomposites, which exhibit significant potential for adsorption, catalysis, targeted delivery and controlled drug release, highly sensitive sensors, flame retardant coatings, and thermal energy storage and release (i.e. phase change materials). Finally, the challenges and prospects for the future development of hierarchical nanocomposites of exfoliated Mt nanolayers and organic species, particularly in hierarchical supramolecular nanostructured composites, are highlighted.

A comprehensive review on magnetic carbon nanotubes and carbon nanotube-based buckypaper for removal of heavy metals and dyes

Industrial effluents contain several organic and inorganic contaminants. Among others, dyes and heavy metals introduce a serious threat to drinking waterbodies. These pollutants can be noxious or carcinogenic in nature, and harmful to humans and different aquatic species. Therefore, it is of high importance to remove heavy metals and dyes to reduce their environmental toxicity. This has led to an extensive research for the development of novel materials and techniques for the removal of heavy metals and dyes. One route to the removal of these pollutants is the utilization of magnetic carbon nanotubes (CNT) as adsorbents. Magnetic carbon nanotubes hold remarkable properties such as surface-volume ratio, higher surface area, convenient separation methods, etc. The suitable characteristics of magnetic carbon nanotubes have led them to an extensive search for their utilization in water purification. Along with magnetic carbon nanotubes, the buckypaper (BP) membranes are also favorable due to their unique strength, high porosity, and adsorption capability. However, BP membranes are mostly used for salt removal from the aqueous phase and limited literature shows their applications for removal of heavy metals and dyes. This study focuses on the existence of heavy metal ions and dyes in the aquatic environment, and methods for their removal. Various fabrication approaches for the development of magnetic-CNTs and CNT-based BP membranes are also discussed. With the remarkable separation performance and ultra-high-water flux, magnetic-CNTs, and CNT-based BP membranes have a great potential to be the leading technologies for water treatment in future.

The efficiency of natural-ecofriendly clay filters on water purification for improving performance and immunity in broiler chickens

Background

Innovative water treatments and purification processes have become a point of interest to provide solutions and meet the basic water requirements and demands. Clay plays a key role in environmental protection from pollutants through ion exchange and/or adsorption.

Aim

The study evaluated the adsorption and antimicrobial efficiency of clay in purifying polluted water, as well as the influence of clay-purified water on performance, immunity, and microbial counts.

Methods

The experimented 280 one-day-old Hubbard broilers were divided into seven groups on a deep litter system. Polluted water (lead nitrate; 500 mg/l, calcium sulfate; 80 mg/l, yeast extract 5%; 5 mg/l, diazinon; 2.5 ml/l, Salmonella Typhimurium; 1.5 × 106 CFU/ml, and Eimeria tenella; 1 × 105 OPG/ml) was filtered using plastic basins of 1 m3 supplied with 60 cm layer of clay. Broiler groups (G1 to G6) were supplied with clay-filtered and G7 with control tape water. A total of 2,182 samples, including 54 water samples, 266 sera, 266 duodenal swabs, 266 breast muscles, 266 fecal samples, and 1,064 organs including liver, spleen, heart, and bursa of Fabricius were collected.

Results

Weight gains, performance indices, water intakes, water/feed intake ratios, live body weights, carcasses weights, edible and immune organs' weights, immunoglobulin G and M, total antioxidant capacity, lactate dehydrogenase, malondialdehyde, and superoxide dismutase revealed highly significant (p < 0.01) increases in all broiler groups supplemented with clay-filtered water compared to the control group. Meanwhile, total protein, alanine aminotransferase, creatinine, glucose, triglycerides, total cholesterol, cortisol hormone, total bacterial and Enterobacteriaceae counts, total Salmonella counts, and E. tenella counts revealed highly significant (p < 0.01) declines in all broiler groups supplemented with clay-filtered water compared to the control group.

Conclusion

Clay filters provided high filtration, adsorption, and antimicrobial efficiency against polluted water, enhanced water quality, and improved performance and immunity in broiler chickens.

Constructing Co-N-C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells

Exploiting platinum-group-metal (PGM)-free electrocatalysts with remarkable activity and stability toward oxygen reduction reaction (ORR) is of significant importance to the large-scale commercialization of proton exchange membrane fuel cells (PEMFCs). Here, a high-performance and anti-Fenton reaction cobalt-nitrogen-carbon (Co-N-C) catalyst is reported via employing double crosslinking (DC) hydrogel strategy, which consists of the chemical crosslinking between acrylic acid (AA) and acrylamide (AM) copolymerization and metal coordinated crosslinking between Co²⁺ and P(AA-AM) copolymer. The resultant DC hydrogel can benefit the Co²⁺ dispersion via chelated Co-N/O bonds and relieve metal agglomeration during the subsequent pyrolysis, resulting in the atomically dispersed Co-Nx/C active sites. By optimizing the ratio of AA/AM, the optimal P(AA-AM)(5-1)-Co-N catalyst exhibits a high content of nitrogen doping (12.36 at%) and specific surface area (1397 m² g^-1 ), significantly larger than that of the PAA-Co-N catalyst (10.59 at%/746 m² g^-1 ) derived from single crosslinking (SC) hydrogel. The electrochemical measurements reveal that P(AA-AM)(5-1)-Co-N possesses enhanced ORR activity (half-wave potential (E_1/2 ) ≈0.820 V versus the reversible hydrogen electrode (RHE)) and stability (≈4 mV shift in E_1/2 after 5000 potential cycles in 0.5 m H₂ SO₄ at 60 ºC) relative to PAA-Co-N, which is higher than most Co-N-C catalysts reported so far.

Self-decoration of N-doped graphene oxide 3-D hydrogel onto magnetic shrimp shell biochar for enhanced removal of hexavalent chromium

In this work, a novel decorated and combined N-doped graphene oxide hydrogel with shrimp shell magnetic biochar (NGO3DH-MSSB) biosorbent was fabricated as an effective material for Cr(VI) removal. Three-dimensional self-assembled graphene oxide hydrogel was synthesized using nitrogen source, ethylenediamine (EDA). Characterizations of NGO3DH-MSSB biosorbent were established by FT-IR, TGA, SEM and BET, where high surface area (398.05 m²/g) compared with that of MSSB (138.64 m²/g) was characterized. The maximum achieved swelling ratio (800%) was only after 300 min. The binding mechanisms between Cr(VI) ions and NGO3DH-MSSB biosorbent were controlled by electrostatic adsorption (ion-pair), pore filling, and reduction-coordination reaction. Adsorption was described by the pseudo-second order kinetic (R² =0.9994, 0.9983 and 0.9992) at 10, 50 and 100 mg/L and Langmuir isotherm model (R² =0.9997, 0.9957 and 0.9912) at 25, 40 and 50 °C. The adsorption capacity (350.42 mg/g) was achieved at pH 1.0, using initial Cr(VI) concentration (100 mg/L) and contact time (180 min) at room temperature. NGO3DH-MSSB biosorbent could be successfully reused after eight cycles. The percentage removal of Cr(VI) were confirmed as 99.79%, 99.20% and 98.00% from tap water, sea water and wastewater, respectively.

Emerging Hexagonal Mo2C Nanosheet with (002) Facet Exposure and Cu Incorporation for Peroxymonosulfate Activation Toward Antibiotic Degradation

The catalyst with a special exposed active facet and multivalent element synergism is much desired for advanced oxidation progress (AOP) reaction. Herein, an emerging substrate, Cu-incorporated Mo₂C, with an active (002) facet exposed was developed by one-step calcination to activate peroxymonosulfate (PMS) toward antibiotic degradation. Combining the multivalent Cu-Mo synergistic effect and Cu complexing interaction, Cu was incorporated onto the Mo₂C surface to further enhance its antibiotic removal through PMS activation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements indicated the 5% Cu-Mo₂C exhibited in the hexagonal nanosheet with Cu uniformly dispersed on the surface. Moreover, 5% Cu-Mo₂C displayed excellent PMS activation which could fully degrade the tetracycline (TC) within 20 min, and the degradation rate was found to be at least 20 times higher than those of pure Mo₂C, classical Fe₂O₃ and Co₃O₄, and Fenton reaction of 5% Cu-Mo₂C. The results were found to be ascribed to enhanced electrical conductivity, multivalent Cu-Mo synergism, and increased generation of active radicals which contributed in the sequence SO₄•^- > •OH > O₂^•-. Surface chemical analysis combined with density functional theory (DFT) calculations confirmed that both Cu²⁺/Cu⁺ and Mo⁶⁺/Mo⁴⁺/Mo²⁺ redox cycles occurred on the (002) plane of Mo₂C, which dominated more free electrons and mainly accounted for facilitating PMS activation. Meanwhile, systematically conditional experiments uncovered that the 5% Cu-Mo₂C exhibited superb catalysis even under a wide pH and temperature, various natural polluted waters and coexisting ions, and long-time recycle. In addition, the as-prepared catalyst presented excellent adaptability for the degradation of different organic effluents originated from medical, dyeing, and beneficiation wastewaters. Considering its great performance, stability, and applicability, 5% Cu-Mo₂C would be a capable candidate for PMS activation toward large-scale practical application in environmental remediation.

Changes in Optical Properties upon Dye-Clay Interaction: Experimental Evaluation and Applications

The development of hybrid materials with unique optical properties has been a challenge for the creation of high-performance composites. The improved photophysical and photochemical properties observed when fluorophores interact with clay minerals, as well as the accessibility and easy handling of such natural materials, make these nanocomposites attractive for designing novel optical hybrid materials. Here, we present a method of promoting this interaction by conjugating dyes with chitosan. The fluorescent properties of conjugated dye–montmorillonite (MMT) hybrids were similar to those of free dye–MMT hybrids. Moreover, we analyzed the relationship between the changes in optical properties of the dye interacting with clay and its structure and defined the physical and chemical mechanisms that take place upon dye–MMT interactions leading to the optical changes. Conjugation to chitosan additionally ensures stable adsorption on clay nanoplatelets due to the strong electrostatic interaction between chitosan and clay. This work thus provides a method to facilitate the design of solid-state hybrid nanomaterials relevant for potential applications in bioimaging, sensing and optical purposes.

Covalent organic framework and montomorillonite nanocomposite as advanced adsorbent: synthesis, characterization, and application in simultaneous adsorption of cationic and anionic dyes

In this work, Schiff base network-1 (SNW-1), as a new generation of covalent organic frameworks (COFs), was synthesized and modified by fabrication of a composite with clay mineral montomorillonite (Mt). It was used for simultaneous removal of anionic and cationic dyes from aqueous solutions. The fabricated composite was characterized successfully with various techniques. Tartrazine (TT) and methylene blue (MB) were selected as model anionic and cationic dyes, respectively. The effects of the percentage of each component in the composite, initial pH, and initial dye concentration were evaluated on the adsorption capacity. Adsorption reaction models and adsorption diffusion models were used to study the kinetic process of adsorption. Adsorption of both dyes reached equilibrium after 40 min. The obtained results were fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) models to predict the isotherms of adsorption. Under optimum conditions for removal of each dye with the composite, the maximum adsorption capacity of 519.2 and 602.7 mg g^-1 were obtained for TT and MB, respectively. The used SNW-1/Mt composite could be regenerated by salty methanol. The high adsorption capacity and excellent reusability make SNW-1/Mt composite attractive for the simultaneous removal of anionic and cationic dyes from aqueous solutions.

Role of Montmorillonite, Kaolinite, or Illite in Pyrite Flotation: Differences in Clay Behavior Based on Their Structures

It is widely acknowledged that clay minerals have detrimental effects on the process of flotation, but the mechanisms involved are still not fully understood. In this work, the effects of montmorillonite, kaolinite, and illite on pyrite flotation were investigated from the perspective of various structures of clay minerals. Flotation tests suggested that the detrimental effect of clay minerals on the flotation of pyrite increased as follows: montmorillonite > kaolinite > illite. With the help of rheology measurements, it was found that montmorillonite significantly increased pulp viscosity, which in turn substantially reduced pyrite recovery and grade. Scanning electron microscopy (SEM) images suggested that montmorillonite formed the "house-of-cards" structure by edge-to-edge and edge-to-face contact, while kaolinite and illite platelets were associated mainly in the face-to-face mode. In addition, it was clearly observed by SEM-energy dispersive spectrometry that montmorillonite and kaolinite coat on the pyrite surfaces, which would lower the surface hydrophobicity of pyrite. Kaolinite covered much larger area of pyrite surface than montmorillonite owing to the positive charge occurring at the exposed aluminum-oxygen octahedral sheet of kaolinite. Although illite has a similar 2:1 structure to montmorillonite, it showed little or no effect on pyrite flotation, which was attributed to its poor swelling nature. These findings shed light on the root cause of the adverse effect of clay minerals on pyrite flotation and are expected to provide theoretical guidance for mitigating the negative effects on flotation caused by clays.

Extraction, optical properties, and aging studies of natural pigments of various flower plants

In this paper, we reported the extraction process of five different flowering plants utilizing different dye extraction methods and solvents (ethanol and water) to choose the best dye removal process. The FTIR spectra revealed the presence of several clear functional groups for all five natural dyes. The analytical studies such as UV spectroscopy, column chromatography, and vacuum evaporation were performed to isolate the dyes from their solutions. The UV-Vis studies on the pigments of flower extracts indicated broad absorption peaks in the visible region including clear bandgaps. Among the studied pigments, Alternanthera ficoidea showed the lowest direct bandgap of 1.69 eV and an Urbach energy value of 6.33 meV. The dye extraction yield rate improvement was extended from 11.7 to 24.7% (water solvent) and 11.3-32.4% (ethanol solvent). Throughout the studies, it was observed that ethanol produced a better extraction for organic dyes than water as a solvent. Aging studies revealed that all the dyes at the room temperature showed better stability with minor changes in the observed optical parameters in oxygen-rich conditions; however, these parameters have shown significant variations at a 60 °C temperature.

Nanoscale Pisum sativum pods biochar encapsulated starch hydrogel: A novel nanosorbent for efficient chromium (VI) ions and naproxen drug removal

Assembly of novel ecofriendly and sustainable (N-PSPB/SHGL) nanosorbent was fabricated based on encapsulation of derived nanoscale spherical biochar from Pisum sativum pods (N-PSPB) with starch hydrogel (SHGL). The mass ratio between starch and N-PSPB was examined and 2% (w/w) was selected as the optimum percentage for fabrication of the assembled hydrogel. High swelling capacity was characterized by N-PSPB/SHGL nanosorbent (500.0%) at room temperature (25 °C), excellent stability for ten cycles with respect to regeneration by 0.1 mol L-1 HCl. Additionally, characterizations of N-PSPB/Starch nanosorbent were established by SEM and BET measurement to characterize surface area (226.94 m2/g) and pore volume (9.88 cm3/g). The N-PSPB/SHGL nanosorbent was subjected to extensive investigations to evaluate its efficiency for removal of naproxen drug (NAP) and chromium (VI). The Cr(VI) and NAP drug adsorptions were fitted to pseudo-second kinetic and correlated with Langmuir isotherm. The adsorption processes were spontaneous and endothermic based on thermodynamic study.

Adsorption toward Cu(II) and inhibitory effect on bacterial growth occurring on molybdenum disulfide-montmorillonite hydrogel surface

Novel molybdenum disulfide-montmorillonite (MoS₂@2DMMT) hydrogels for Cu(II) removal and inhibition on bacterial growth were successfully prepared. MoS₂ was first in-situ growth onto 2DMMT platelet through hydrothermal method and then cross-linked with organic reagents to form hydrogels. The flower-like structure of synthesized MoS₂ could be clearly observed in MoS₂@2DMMT by SEM. The synthesized hydrogels possessed a three-dimensional macroporous structure, offering a free access for contaminants to get inside and combine with the active sites. Adsorption tests revealed that efficient Cu(II) removal (65.75 mg/g) could be achieved within a short time (30 min) at pH 5. The pseudo-second-order kinetics model and Langmuir isotherm model indicated the existence of chemisorption and monolayer absorption for Cu(II) onto MoS₂@2DMMT hydrogels. Characterizations of EDS and XPS indicated that Cu(II) reacted with groups of carboxyl, hydroxyl and amidogen. Bacteriostatic tests revealed that almost a complete bacteriostatic was achieved with just small dosage (0.8 mg/mL) of MoS₂@2DMMT hydrogels after the Cu(II) removal under the normal illumination. The mechanism was ascribed to the destructive effect of Cu(II) to the cytomembrane and the damage of reactive oxygen species (ROS) to the DNA. Such hydrogel not only provided insights for treating co-existing contaminates, but also guides for designing novel polymer materials from two-dimensional (2D) nano-materials.