Heavy metal ions are toxic to humans, plants, and marine life, making it crucial to eliminate them from water. This study reports the development of a new nanocomposite material (Alg@Ag/PU) that ...involves modifying silver nanoparticles (Ag NPs) with alginate (Alg) and coating them onto a polyurethane sponge (PU) for removing heavy metal ions. The successful coating of Alg@Ag NPs onto PU due to their strong chemical binding was confirmed by morphology and size characterization. Batch experiments were conducted to evaluate the removal efficiency of heavy metal ions at high concentrations (∼100 mg/L). The maximum adsorption amount was achieved within 6 h, and the highest removal efficiency was obtained at pH values between 6 and 7. Furthermore, the Alg@Ag/PU nanocomposite demonstrated excellent recyclability for metal ion removal even after 5 cycles. In summary, this work developed a simple and cost-effective method for producing an environmentally-friendly nanocomposite material for the efficient removal of heavy metal ions.
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•A new nanocomposite (Alg@Ag/PU) is developed for heavy metal ions removal.•Alg@Ag/PU is environmentally-friendly, cost-effective, reusable, and sustainable.•The removal efficiency of heavy metal ions remains great at high concentrations.•The composite has great recyclability, with high efficiency even after 5 cycles.
A ring-shaped stain is frequently left on a substrate by a drying drop containing colloids as a result of contact line pinning and outward flow. In this work, however, different patterns are observed ...for drying drops containing small solutes or polymers on various hydrophilic substrates. Depending on the surface activity of solutes and the contact angle hysteresis (CAH) of substrates, the pattern of the evaporation stain varies, including a concentrated stain, a ringlike deposit, and a combined structure. For small surface-inactive solutes, the concentrated stain is formed on substrates with weak CAH, for example, copper sulfate solution on silica glass. On the contrary, a ringlike deposit is developed on substrates with strong CAH, for example, a copper sulfate solution on graphite. For surface-active solutes, however, the wetting property can be significantly altered and the ringlike stain is always visible, for example, Brij-35 solution on polycarbonate. For a mixture of surface-active and surface-inactive solutes, a combined pattern of a ringlike and concentrated stain can appear. For various polymer solutions on polycarbonate, similar results are observed. Concentrated stains are formed for weak CAH such as sodium polysulfonate, and ring-shaped patterns are developed for strong CAH such as poly(vinyl pyrrolidone). The stain pattern is actually determined by the competition between the time scales associated with contact line retreat and solute precipitation. The suppression of the coffee-ring effect can thus be acquired by the control of CAH.
Additive manufacturing is a promising technique for offering novel functionality to various materials by creating three-dimensional (3D) structures. However, the development of sustainable synthesis ...processes for 3D printing inks or 3D-printed materials remains a major challenge. In this work, a simple two-step mixing approach is developed to prepare a 3D printing ink from green, low-cost, and low-toxicity materials commercial Carbopol and deep eutectic solvents (DESs). A small weight fraction of Carbopol can impart desired rheological properties to the DES used in the 3D printing ink and also can significantly enhance the stretchability of eutectogels up to 2500% strain. The 3D-printed auxetic structure shows a negative Poisson’s ratio (within 100% strain), high stretchability (300%), high sensitivity (gauge factor of 3.1), good moisture resistance, and sufficient transparency. It can detect human motion with high skin comfort and breathability. The results of this work highlight a green, low-cost, and energy-saving strategy to fabricate conductive microgel-based inks for 3D printing of wearable devices.
The wetting behavior of simple binary mixtures containing both partial and total wetting liquids is investigated on the commonly used substrates. The variation of the contact angle (CA) of the binary ...liquid with the composition (xP) on different solid surfaces is obtained. It is interesting to find that for the droplet which can exhibit self-propulsion, four different regimes can be identified in the CA-xP plot. Among them, the plateau regime where the CA remains a constant value in a certain concentration range is most intriguing. In contrast, for the droplet which cannot self-propel, the CA grows monotonously with the concentration of the partial wetting liquid. The leak-out phenomenon in which the droplet is surrounded by the precursor film is believed to occur in the plateau regime, and it is examined by observing the encounter of two miscible droplets by optical microscopy. The apparently noncontact repulsion between the moving and static droplets reveals the presence of the precursor film leaked out from the self-propelled droplet.
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Nonsolvent-induced phase separation is widely used to create polymer membranes, but its demixing process is generally understood by liquid-liquid separation. In this work, the solidification dynamics ...of polymer solutions for membrane formation are explored through dissipative particle dynamics simulations. The shrinkage of the symmetric film of polymer solution is monitored, and the evolutions of the concentration profiles of polymer, solvent, and nonsolvent are analyzed. Additionally, the evolution of the degree of crystallinity (local alignment) and the morphology of the developing membrane are also studied. Three regions can be identified: (i) interfacial region, (ii) dense layer, and (iii) middle region. The demixing process associated with liquid-solid separation is found to be caused by the extraction of solvent and concentration of polymers rather than nonsolvent-induced separation. Our results provide valuable insights into directional solidification and spontaneous stratification of the membrane, driven by solvent loss and oversaturation (beyond the maximum solubility of polymer).
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•Solidification dynamics of polymer solutions for membrane formation is presented.•The shrinkage process involves negligible solvent-nonsolvent exchange.•Polymer precipitation is mainly driven by solvent loss and polymer oversaturation.•Spontaneous stratification emerges within the symmetric yet nonuniform membrane.
Droplets of a polymer solution can solidify in a nonsolvent bath, forming solid capsules and particles. However, the dynamics of this process, based on nonsolvent-induced phase separation, remains ...elusive. In this work, the solidification dynamics of polymer solution droplets is explored using dissipative particle dynamics simulations for different initial polymer concentrations. The dynamics of the shrinking droplets is monitored. Additionally, the evolutions of solvent and nonsolvent concentrations are examined, and the local polymer concentration profiles are analyzed. Furthermore, the microstructural characteristics of polymers, including the degree of crystallinity (local alignment) and the radius of gyration of polymers, are investigated. It is interesting to observe that the macroscopic morphology and microscopic configuration are significantly dependent on initial polymer concentrations. At higher concentrations, hollow particles are formed, containing polymer shells with longer persistence lengths. Conversely, lower concentrations lead to the creation of solid particles with increased chain-folding. Our results provide valuable insights into the influence of initial polymer concentrations on polymeric capsules and particle formation.
Graft
copolymers with diblock side-chains A
m
(-
graft
-B
3
A
y
)
n
in a selective solvent have been reported to self-assemble into vesicles, but the structure is expected to differ distinctly from ...those of lipid bilayers. Surprisingly, the number of alternating hydrophobic A-block and hydrophilic B-block layers in the vesicle can vary from a monolayer to multilayers such as the hepta-layer, subject to the same copolymer concentration. The area density of the copolymer layer is not uniform across the membrane. This structural difference among different layers is attributed to the neighboring environment and the curvature of the layer. Because of the unusual polymer conformations, nonlamellar structures of polymersomes are formed, and they are much more intricate than those of liposomes. In fact, a copolymer can contribute to a single or two hydrophilic layers, and it can provide up to three hydrophobic layers. The influence of the backbone length (
m
) and side-chain length (
y
) and the permeation dynamics are also studied. The thickness of hydrophobic layers is found to increase with increasing side-chain length but is not sensitive to the backbone length. Although the permeation time increases with the layer number for planar membranes, the opposite behavior is observed for spherical vesicles owing to the curvature-enhanced permeability associated with Laplace pressure.
Smart surfaces with switchable wettability for both aqueous and non-aqueous drops based on zwitterionic sulfobetaine silane (SBSi) have been fabricated. The wettability transition occurs from a total ...wetting (contact angle, CA ≈ 0°) to a partial wetting (CA as high as ∼75°) state. A surfactant solution (aqueous or non-aqueous) rinse (for 5 s) acts as a stimulus and the reversal of surface wettability is achieved simply by a pure water rinse. The reversible behavior of the switchable wettability of a SBSi surface can be observed for at least 100 cycles. Various cationic surfactants are used as stimuli for aqueous drops and anionic surfactants are employed for non-aqueous drops. This unique wettability-switching property is attributed to basal surfactant adsorption driven by electrostatic attractions between the charged surfactant head groups and zwitterionic groups of SBSi. Such rapid surfactant adsorption is also responsible for intriguing drop fission and dewetting phenomena, shown by stimulus drops cast on clean SBSi surfaces. Thus, this smart switchable wettability surface can be employed to fabricate intelligent devices for controlling mobility and sensing.