Nanochitin/manganese oxide-biodegradable hybrid sorbent for heavy metal ions

Synthesis of porous calcium-guar gum benzoate nano-biohybrids for sorptive removal of congo red and phosphates from water

This work aims to develop an eco-sound nano-bio-hybrid sorbent using sustainable materials for sorptive elimination of congo red and phosphates from aquatic environment. An amphipathic biopolymer derivative, high DS guar gum benzoate (GGBN) was used for entrapment of as synthesized calcium carbonate nanoparticles using solvent diffusion nano-precipitation technique. Designer nano-biohybrids were developed upon experimenting with various materials stoichiometry. SEM, XRD and EDX studies confirmed near-uniform impregnation of rhombohedral calcium carbonate crystals throughout the biopolymer matrix. Average pore size distribution and surface area of final product Ca-GGBNC, were estimated from NDLFT and BET methods respectively. Analysis of adsorption findings acquired at study temperature 27 ± 2 °C showed that the maximum adsorption capacity of Ca-GGBNC recorded qmax, 333.33 mg/g for congo red azo dye and that for phosphate was at 500 mg/g. Adsorptive removal was noted and both components followed pseudo second order kinetics. Intra-particle diffusion kinetics investigation disclosed that the boundary layer effect was prominent and the adsorption rates were not solely directed by the diffusion stage. Activation energy, Ea was to be estimated using Arrhenius equation at 56.136 and 47.015 KJ/mol for congo red and phosphates respectively. The calculated thermodynamic parameters(ΔG°, ΔH°, and ΔS°) revealed the spontaneous, feasible and endothermic sorption process. Owing to active surface area, spherical size, functional moiety and porous network, antibacterial properties of nanobiohybrid were persistent and MIC against E. coli and S. aureus were recorded at 200 μg/mL and 350 μg/mL respectively.

Biocompatible Nanoparticle Heteroaggregates as Stabilizers of Pickering Emulsions for Vitamin D3 Efficient Delivery

Vitamin D3 deficiency is a major public health problem worldwide, and standard cholecalciferol formulations provide poor absorbability of the vitamin. Several biphasic formulas have been proposed to overcome the disadvantages in which Pickering emulsions stand out in particular. This paper describes olive oil-in-water Pickering emulsions stabilized by pseudoboehmite (AlOOH), cellulose nanocrystals (CNC), and their heterocoagulates. Colloidal properties were assessed by laser Doppler microelectrophoresis, potentiometric titration, and rheology. It was shown that the heterocoagulation of CNC and AlOOH led to a drastic change in surface properties (ζ-potential, pKa, and number of active centers), which promoted the formation of more stable emulsions with the smallest size of droplets and the highest viscosity among the studied samples. Simulated digestion studies showed the targeted release in the small intestine medium where cholecalciferol should be delivered. High-performance liquid chromatography showed the efficient encapsulation of cholecalciferol in emulsions (86% of initial concentration). Oral administration to laboratory mice of initial nanoparticles and emulsions stabilized by them showed nontoxicity for all of the components, and they were estimated to be class V materials. The proposed emulsions have great potential as targeted delivery systems of lipophilic drugs.

Biofibrous nanomaterials for extracting strategic metal ions from water

Strategic metals play an indispensable role in the related industries. Their extraction and recovery from water are of great significance due to both their rapid consumption and environmental concern. Biofibrous nanomaterials have shown great advantages in capturing metal ions from water. Recent progress in extraction of typical strategic metal ions such as noble metal ions, nuclear metal ions, and Li-battery related metal ions is reviewed here using typical biological nanofibrils like cellulose nanofibrils, chitin nanofibrils, and protein nanofibrils, as well as their assembly forms like fibers, aerogels/hydrogels, and membranes. An overview of advances in material design and preparation, extraction mechanism, dynamics/thermodynamics, and performance improvement in the last decade is provided. And at last, we propose the current challenges and future perspectives for promoting biological nanofibrous materials toward extracting strategic metal ions in practical conditions of natural seawater, brine, and wastewater.

Preparation of Needleless Electrospinning Polyvinyl Alcohol/Water-Soluble Chitosan Nanofibrous Membranes: Antibacterial Property and Filter Efficiency

Electrospinning is an efficient method of producing nanofibers out of polymers that shows a great potential for the filtration territory. Featuring water-soluble chitosan (WS-CS), a low-pollution process and a self-made needleless machine, PVA/WS-CS nanofibrous membranes were prepared and evaluated for nanofiber diameter, bacteriostatic property, filtration efficiency, pressure drop, and quality factor. Test results indicate that the minimal fiber diameter was 216.58 ± 58.15 nm. Regardless of the WS-CS concentration, all of the PVA/WS-CS nanofibrous membranes attained a high porosity and a high water vapor transmission rate (WVTR), with a pore size of 12.06–22.48 nm. Moreover, the membranes also exhibit bacteriostatic efficacy against Staphylococcus aureus, an optimal quality factor of 0.0825 Pa⁻¹, and a filtration efficiency as high as 97.0%, that is 72.5% higher than that of common masks.

Effective removal of heavy metals from water using porous lignin-based adsorbents

Multifunctional composite materials are the key to improving removal capacity and environmental utility. Here, the adsorbent (SLCA) was obtained by free-radical polymerization of acrylic acid with sodium lignosulfonate and citric acid. FTIR, SEM, TGA and XPS characterization methods were used to prove the structure and properties of SLCA adsorbents. The maximum uptake capacities of the optimized SLCA adsorbent is 276 mg g^-1 of Cu²⁺ and 323 mg g^-1 of Pb²⁺, respectively. The Langmuir isotherm and the second-order kinetic model were established to illustrate that the capture of Cu²⁺ and Pb²⁺ by the adsorbent belongs to chemisorption on the monolayer. XPS analysis confirmed that complexation and electrostatic attraction are the mechanism of pollutant removal. Not only that, as-resulting adsorbent revealed no significant adsorption cycle efficiency reduction even after 5 runs of sorption-desorption cycle, manifesting that it is of great stability and could be regarded as a promising candidate adsorbent. The purpose of this research was to develop a green lignin-based adsorbent with strong environmental protection and regeneration ability based on cheap polyacrylic resin.

Sponge-like Chitosan Based Porous Monolith for Uraemic Toxins Sorption

More than three million patients are treated for kidney failure world-wide. Haemodialysis, the most commonly used treatment, requires large amounts of water and generates mountains of non-recyclable plastic waste. To improve the environmental footprint, dialysis treatments need to develop absorbents to regenerate the waste dialysate. Whereas conventional dialysis clears water-soluble toxins, it is not so effective in clearing protein-bound uraemic toxins (PBUTs), such as indoxyl sulfate (IS). Thus, developing absorption devices to remove both water-soluble toxins and PBUTs would be advantageous. Vapour induced phase separation (VIPS) has been used in this work to produce polycaprolactone/chitosan (PCL/CS) composite symmetric porous monoliths with extra porous carbon additives to increase creatinine and albumin-bound IS absorption. Moreover, these easy-to-fabricate porous monoliths can be formed into the required geometry. The PCL/CS porous monoliths absorbed 436 μg/g of albumin-bound IS and 2865 μg/g of creatinine in a single-pass perfusion model within 1 h. This porous PCL/CS monolith could potentially be used to absorb uraemic toxins, including PBUTs, and thus allow the regeneration of waste dialysate and the development of a new generation of environmentally sustainable dialysis treatments, including wearable devices.

Structure and properties of cellulose/HAP nanocomposite hydrogels

The exploiting of abundant natural polymers as potential absorbents for heavy metal ions is attracting. Cellulose is the most abundant natural polymer and exhibits amazing properties such as high chemical stability, hydrophilicity and biodegradability. However, some properties of pure cellulose-based materials including adsorbability are usually not enough, so it is important to improve their properties to broaden their applications. In the present work, hydroxyapitite (HAP) nanoparticles were prepared and introduced to improve the cellulose hydrogel (CG) properties. The structure and properties of the resultant cellulose/HAP nanocomposite hydrogels (CHG) were characterized and studied systematically. The results indicated that HAP nanoparticles was fixed and distributed evenly in CG. The maximum decomposition temperature increased gradually from 334.6 °C for CG to 346.7 °C for CHG, and the compressive strength increased gradually from 100 kPa for CG to 570 kPa for CHG with the increase of HAP content, respectively. Moreover, the adsorption capacity (q_e) value of CHG towards Cu²⁺ could reach more than 300% higher than that of CG. As a potential absorbent, CHG exhibited relatively good recyclability of more than 78% after 10 cycles. Therefore, the introduction of HAP improved the properties of CG greatly, showing wide potential applications.

Sequential Oxidation on Wood and Its Application in Pb2+ Removal from Contaminated Water

Raw wood was subjected to sequential oxidation to produce 2,3,6-tricarboxycellulose (TCC) nanofibers with a high surficial charge of 1.14 mmol/g in the form of carboxylate groups. Three oxidation steps, including nitro-oxidation, periodate, and sodium chlorite oxidation, were successfully applied to generate TCC nanofibers from raw wood. The morphology of extracted TCC nanofibers measured using TEM and AFM indicated the average length, width, and thickness were in the range of 750 ± 110, 4.5 ± 1.8, and 1.23 nm, respectively. Due to high negative surficial charges on TCC, it was studied for its absorption capabilities against Pb2+ ions. The remediation results indicated that a low concentration of TCC nanofibers (0.02 wt%) was able to remove a wide range of Pb2+ ion impurities from 5–250 ppm with an efficiency between 709–99%, whereby the maximum adsorption capacity (Qm) was 1569 mg/g with R2 0.69531 calculated from Langmuir fitting. It was observed that the high adsorption capacity of TCC nanofibers was due to the collective effect of adsorption and precipitation confirmed by the FTIR and SEM/EDS analysis. The high carboxylate content and fiber morphology of TCC has enabled it as an excellent substrate to remove Pb2+ ions impurities.

Efficient removal of various coexisting organic pollutants in water based on β-cyclodextrin polymer modified flower-like Fe3O4 particles

HYPOTHESIS

The construction of porous β-cyclodextrin polymer (β-CDP) modified flower-like Fe₃O₄ particles (CDP@Fe₃O₄) is expected to remove various organic pollutants from water, based on the larger specific surface area of flower-like Fe₃O₄ particles and the active sites provided by β-CDP. With the help of various noncovalent interactions, the removal ability of CDP@Fe₃O₄ for various water-soluble and water-insoluble organic pollutants were systematically studied.

EXPERIMENTS

CDP@Fe₃O₄ were successfully synthesized and applied for the simultaneous removal of various organic pollutants with different electrical properties, structure and hydrophobicity. Adsorption efficiency, adsorption process, adsorption mechanism and the reusability of CDP@Fe₃O₄ for single pollutant and mixed pollutants were comprehensively investigated.

FINDINGS

CDP@Fe₃O₄ exhibited excellent adsorption capabilities for various pollutants. Importantly, when these pollutants were coexisting, CDP@Fe₃O₄ still maintained a comparable removal ability for various pollutants. Efficient removal of organic pollutants was attributed to varieties of noncovalent interactions between organic pollutants and CDP@Fe₃O₄, including hydrophobic interactions, hydrogen bonds, π-π and electrostatic interactions. These results revealed that the excellent adsorption ability and convenient regeneration make CDP@Fe₃O₄ being a potential candidate in various complex organic wastewater purification.

Magnetic/Polyetherimide-Acrylonitrile Composite Nanofibers for Nickel Ion Removal from Aqueous Solution

In this study, a magnetic/polyetherimide-acrylonitrile composite nanofiber membrane with effective adsorption of nickel ions in an aqueous solution was created using a simple electrospinning method. Iron oxide nanoparticles (NPs) were stirred and ultrasonically dispersed into a polyetherimide-acrylonitrile solution to create a homogenous NPs suspension, which was placed in an electrospinning machine to produce a uniform and smooth nanofiber composite membrane. Nanoparticle incorporation into this membrane was confirmed using scanning electron microscope, energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and NPs aqueous stability from a leaching test. The high adsorption capability of the membrane on nickel ions was attributed to the combination of magnetic NPs, polyetherimide-acrylonitrile matrix, and the nanostructure of the membrane. A membrane containing magnetic NPs demonstrated the maximum adsorption capabilities (102 mg/g) of nickel ions in an aqueous solution. Various kinetic and isotherm models were applied to understand the adsorption behavior, such as pseudo-second-order kinetic and Langmuir isotherm models. A polyetherimide-acrylonitrile composite nanofiber membrane containing magnetic NPs could be used as an environmentally friendly and nontoxic adsorbent for the removal of nickel ions in an aqueous medium due to its ease of preparation and use and stability in aqueous mediums.

Pulse electrodeposited, morphology controlled organic-inorganic nanohybrids as bifunctional electrocatalysts for urea oxidation

Organic-inorganic nanohybrids with nanoscale architectures and electrocatalytic properties are emerging as a new branch of advanced functional materials. Herein, nanohybrid organic-inorganic nanosheets are grown on carbon paper via a pulse-electrochemical deposition technique. A benzo[2,1,3]selenadiazole-5-carbonyl protected dipeptide BSeFL (BSe = benzoselenadiazole; F = phenylalanine; and L = leucine) cross-linked with Ni2+ ions (Ni-BSeFL) and nickel hydroxide (Ni(OH)2) in a BSeFL/Ni(OH)2 electrode exhibits stable electrocatalytic activity toward urea oxidation. The cross-linked nanosheet morphology of nanohybrids was optimized by controlling the reduction potential during pulse electrodeposition. The BSeFL/Ni(OH)2 (-1.0 V) nanohybrid deposited at -1.0 V provides abundant active sites of Ni3+ with low charge transfer resistance (RCT) and high exchange current density (J0) at the electrocatalytic interface. The nanohybrids with Ni-BSeFL and Ni(OH)2 show low overpotential and superior stability for electrocatalytic urea electro-oxidation. The BSeFL/Ni(OH)2 (-1.0 V) nanohybrid based electrode requires a low potential of 1.30 V (vs. RHE) to acquire a current density of 10 mA cm-2 for the urea oxidation reaction (UOR) in urea containing alkaline solution which is lower than that for water oxidation in alkaline solution (1.49 V vs. RHE). The organic-inorganic nanohybrid BSeFL/Ni(OH)2 (-1.0 V) shows durability over 10 h for oxygen evolution and urea electro-oxidation, thereby confirming the BSeFL/Ni(OH)2 (-1.0 V) nanohybrid-based electrode as an efficient electrocatalyst.

Adsorptive-Oxidative Removal of Sulfides from Water by MnO2-Loaded Carboxylic Cation Exchangers

Hybrid ion exchangers (HIX) containing manganese(IV) oxide (MnO₂) based on macroporous and gel-type carboxylic cation exchangers as supporting materials were obtained. The hybrid materials were characterized using scanning electron microscopy with energy dispersive spectrometry (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and nitrogen adsorption isotherms at 77 K and mercury porosimetry. HIX with introduced MnO₂ (20.0–32.8 wt% Mn) were tested for removal of dissolved sulfides from anoxic aqueous solutions with 100–500 mg S²⁻/dm³ concentrations. The process proceeded effortlessly at pH 10–13 despite unfavorable electrostatic interactions of the reactants. The highest exhibited sorption capacity was 144.3 ± 7.1 mg S²⁻/g. Approximately 65% of dissolved sulfides were oxidized to S₂O₃²⁻ ions and repelled from HIX structure. On average, 13% of sulfide removal products were adsorbed by the MnO₂ surface. The impact of MnO₂ load and the ionic form of HIX functional groups on removal of sulfides and resulting products was examined. The mechanism of the process is suggested.

Maria H, Gopi S, Volova T, C. M. Fernandes S, Thomas S. Extraction of Nanochitin from Marine Resources and Fabrication of Polymer Nanocomposites: Recent Advances

Industrial sea food residues, mainly crab and shrimp shells, are considered to be the most promising and abundant source of chitin. In-depth understanding of the biological properties of chitin and scientific advancements in the field of nanotechnology have enabled the development of high-performance chitin nanomaterials. Nanoscale chitin is of great economic value as an efficient functional and reinforcement material for a wide range of applications ranging from water purification to tissue engineering. The use of polymers and nanochitin to produce (bio) nanocomposites offers a good opportunity to prepare bioplastic materials with enhanced functional and structural properties. Most processes for nanochitin isolation rely on the use of chemical, physical or mechanical methods. Chitin-based nanocomposites are fabricated by various methods, involving electrospinning, freeze drying, etc. This review discusses the progress and new developments in the isolation and physico-chemical characterization of chitin; it also highlights the processing of nanochitin in various composite and functional materials.

Environmentally friendly Au@CNC hybrid systems as prospective humidity sensors

Cellulose nanocrystals are a “green” support for nanogold. Hybrid films quickly and autonomously respond to changes in humidity and can be used in sensing applications.