Recovery of sulfuric acid aqueous solution from copper-refining sulfuric acid wastewater using nanofiltration membrane process.

We used a nanofiltration (NF) membrane process to produce purified aqueous sulfuric acid from copper-refining sulfuric acid wastewater. Wastewater generated from a copper-refining process was used to explore the membrane performances and acid stabilities of six commercial NF membranes. A combination of permeate flux, sulfate permeation, and metal ion rejection clearly showed that two polyamide membranes and a polyacrylonitrile-based membrane achieved recovery of a purified sulfuric acid solution. Acid-stability and long-term performance tests showed that the polyamide membranes were unsuitable for copper-refining wastewater treatment because of their low acid stabilities. In contrast, the polyacrylonitrile-based composite membrane showed excellent acid stability, and gave greater than 90% metal ion rejection, with the exception of calcium ions, for 430 d. We also evaluated the recovery performance in 1 ton/d pilot-scale process using wastewater from copper-refining process; 90% metal ion rejection was achieved, with the exception of calcium ions, even at 95% recovery rate.

Hydrophilic and positively charged polyethylenimine-functionalized mesoporous magnetic clusters for highly efficient removal of Pb(II) and Cr(VI) from wastewater.

We develop mesoporous magnetic clusters (MMCs) functionalized with hydrophilic branched polyethylenimine (b-PEI), later called b-MG, and MMCs functionalized with positively charged b-PEI (p-MG). These materials efficiently remove Pb(II) and Cr(VI) from wastewater. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and nitrogen adsorption-desorption analysis results clearly indicate that hydrophilic b-PEI and positively charged b-PEI are successfully attached to the MMC surfaces. Wide-angle X-ray diffraction, high-resolution transmission electron microscopy, and field-emission scanning electron microscopy analyses confirm that the crystal structures and morphologies of the MMCs are maintained well even when wet chemical modification processes are used to introduce hydrophilic b-PEI and positively charged b-PEI to the MMC surfaces. Langmuir and Sips isotherm models are applied to describe Pb(II) adsorption behavior of the b-MG and Cr(VI) adsorption behavior of the p-MG. The isotherm models indicate that the maximum adsorption capacities of b-MG and p-MG, respectively, are 216.3 and 334.1 mg g-1, respectively. These are higher than have previously been found for other adsorbents. In reusability tests, using magnetic separation and controlling the pH, the Pb(II) recovery efficiency of the b-MG is 95.6% and the Cr(VI) recovery efficiency of the p-MG is 68.0% even after the third cycle.

Structurally Enhanced Self-Plasticization of Poly(vinyl chloride) via Click Grafting of Hyperbranched Polyglycerol.

A highly self-plasticized poly(vinyl chloride) (PVC) is demonstrated for the first time via click grafting of hyperbranched polyglycerol (HPG). The plasticizing effect of the grafted HPG on PVC is systematically investigated by various analytical methods. The amorphous and bulky dendritic structure of HPG efficiently increases the free volume of the grafted PVC, which leads to a remarkably lower glass transition temperature comparable to that of the conventional plasticized PVC. Viscoelastic analysis reveals that HPG considerably improves the softness of the grafted PVC at room temperature and promotes the segmental motion in the system. The HPG-grafted PVC films exhibit an exceptional stretchability unlike the mixture of PVC and HPG because the covalent attachment of HPG to PVC allows it to maintain its homogeneous and well-organized architecture under tensile stretching. The work provides valuable insights into the design of highly flexible and stretchable polymeric materials by means of introducing hyperbranched side chains.

Photoresponsive coumarin-stabilized polymeric nanoparticles as a detectable drug carrier.

The ability to create aqueous suspended stable nanoparticles of the hydrophobic homopolymer poly(ϵ-caprolactone) end-functionalized with coumarin moieties (CPCL) is demonstrated. Nanoparticles of CPCL are prepared in a continuous manner using nanoprecipitation. The resulting nanoparticles are spherical in morphology, about 40 nm in diameter, and possess a narrow size distribution and excellent stability over 4 months by repulsive surface charge. Nanoparticle size can be easily controlled by manipulating the concentration of CPCL in the solution. The interparticle assembly between the nanoparticles can be reversibly adjusted with photoirradiation due to photoinduced [2 + 2] cyclodimerization and cleavage between the coumarin molecules. In addition, the CPCL nanoparticles show significant cellular uptake without cytotoxicity, and the intrinsic fluorescence of the coumarin functional group permits the direct detection of cellular internalization.

Dialysis nanoprecipitation of polystyrene nanoparticles.

Using a facile dialysis nanoprecipitation method, nanoparticles of several hundred nanometers have been successfully generated from a "traditional," non-biodegradable polymer, that is, polystyrene. The effect of initial polymer concentration inside the dialysis membrane, as well as the polymer/solvent system and the ionic strength (electrolyte concentration) of the dialysis solution, on nanoparticle size is examined. A nucleation-aggregation mechanism has been provided to explain the observed trends. Furthermore, we determine the zeta potential as a function of ionic strength for the generated nanoparticles and show that anionic charging may be present in the system.

Enhancement of tensile toughness of poly(lactic acid) (PLA) through blending of a polydecalactone-grafted cellulose copolymer: The effect of mesophase transition on mechanical properties.

Increasing the toughness of poly(lactic acid) (PLA), i.e., simultaneously increasing both the tensile strength and ductility, remains a major challenge. In this study, fully bio-based PLA blends with polydecalactone (PDL)-grafted cellulose copolymer (CgPD) were prepared and comprehensively analyzed to enhance the toughness of the PLA matrix. The blends were found by FT-IR and solid-state 1H NMR to be physically intact and miscible at the sub-twenty-nanometer scale. The WXRD and DSC analyses indicated that the addition of the alkyl-branched CgPD imparts a more structurally disordered PLA mesophase state to the prepared PLA_CgPD bio-blends. UTM analysis was used to characterize the macroscopic mechanical properties of the PLA_CgPD bio-blends. Both the tensile strength and elongation properties were simultaneously improved with the addition of 1 wt% CgPD loading amount to PLA (PLA_CgPD1). This study experimentally demonstrates that the enhanced mechanical properties of PLA_CgPD1 are closely related to the existence of more ordered PLA mesophases induced by the introduction of an optimal amount of CgPD into the PLA matrix.

An Ultrasensitive, Visco-Poroelastic Artificial Mechanotransducer Skin Inspired by Piezo2 Protein in Mammalian Merkel Cells.

An artificial ionic mechanotransducer skin with an unprecedented sensitivity over a wide spectrum of pressure by fabricating visco-poroelastic nanochannels and microstructured features, directly mimicking the physiological tactile sensing mechanism of Piezo2 protein is demonstrated. This capability enables voice identification, health monitoring, daily pressure measurements, and even measurements of a heavy weight beyond capabilities of human skin.

Unentangled star-shape poly(ε-caprolactone)s as phthalate-free PVC plasticizers designed for non-toxicity and improved migration resistance.

We develop a nontoxic unentangled star-shape poly(ε-caprolactone) (UESPCL) plasticizer with excellent migration resistance for the production of phthalate-free flexible poly(vinyl chloride) (PVC) by means of the ring-opening polymerization of ε-caprolactone, initiated from the multifunctional core, combined with end-capping, and vacuum purification processes. UESPCL is a transparent liquid at room temperature and exhibits unentangled Newtonian behavior because of its extremely short branched segments. UESPCL is biologically safe without producing an acute toxicity response. Torque analysis measurements reveals that UESPCL offers a faster fusion rate and a higher miscibility with PVC compared to a typical plasticizer, di(2-ethylhexyl) phthalate (DEHP). The solid-state (1)H nuclear magnetic resonance (NMR) spectrum reveals that PVC and UESPCL are miscible with an average domain size of less than 8 nm. The flexibility and transparency of the PVC/UESPCL mixture, that is, phthalate-free flexible PVC, are comparable to the corresponding properties of the PVC/DEHP mixture, and the stretchability and fracture toughness of PVC/UESPCL are superior to the corresponding properties of the PVC/DEHP system. Most of all, PVC/UESPCL shows excellent migration resistance with a weight loss of less than 0.6% in a liquid phase, whereas DEHP migrated out of PVC/DEHP into a liquid phase with a weight loss of about 10%.

Investigation of coumarin functionality on the formation of polymeric nanoparticles.

The effect of coumarin molecules on the formation of polymeric nanoparticles is examined using a model polymer, poly(methyl methacrylate) (PMMA), functionalized with varying amounts of coumarin pendant groups (PCM). PCM nanoparticles are prepared in a continuous manner by Flash NanoPrecipitation (FNP). PCM forms spherical nanoparticles in water, while the PMMA without coumarin functionality fails to form nanoparticles. As the amount of coumarin functionality increases, the nanoparticle size and size polydispersity are decreased and the nanoparticle stability in water is enhanced. In particular, well-isolated spherical nanoparticles are generated from PCM with 20 mol% coumarin side chain functionality. These results can be explained by an observed increase in the negative surface charge with increasing coumarin content in the polymer.

Amphiphilic thiol functional linker mediated sustainable anti-biofouling ultrafiltration nanocomposite comprising a silver nanoparticles and poly(vinylidene fluoride) membrane.

We develop sustainable anti-biofouling ultrafiltration membrane nanocomposites by covalently immobilizing silver nanoparticles (AgNPs) onto poly(vinylidene fluoride) (PVDF) membrane mediated by a thiol-end functional amphiphilic block copolymer linker. Field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDXS) measurements reveal that the AgNPs are highly bound and dispersed to the PVDF membrane due to the strong affinity of the AgNPs with the thiol-modified block copolymeric linkers, which have been anchored to the PVDF membrane. The membrane performs well under water permeability and particle rejection measurements, despite the high deposition of AgNPs on the surface of membrane. The Ag-PVDF membrane nanocomposite significantly inhibits the growth of bacteria on the membrane surface, resulting in enhanced anti-biofouling property. Importantly, the AgNPs are not released from the membrane surface due to the robust covalent bond between the AgNPs and the thiolated PVDF membrane. The stability of the membrane nanocomposite ensures a sustainable anti-biofouling activity of the membrane.

Reduced migration from flexible poly(vinyl chloride) of a plasticizer containing beta-cyclodextrin derivative.

The migration of endocrine-disrupting di-(2-ethylhexyl) phthalate (DEHP) poses a serious threat to public health and the environment. In this study, we successfully prepared a plasticizerwith reduced DEHP migration by directly incorporating 2,3,6-per-O-benzoyl-beta-cyclodextrin (Bz-beta-CD) into DEHP. Bz-beta-CD was prepared by esterification between the hydroxyl groups of beta-CD and benzoyl chloride. The presence of this cyclodextrin is expected to facilitate formation of stable complexes through pi-pi association with DEHP molecules. The flexible PVC was prepared with a gelation-fusion process that uses the prepared migration-resistant plasticizer, and its properties (flexibility, thermal stability, and clarity) were evaluated by carrying out DSC and tensile testing, TGA, and haze testing, respectively. No significant changes in the physical properties of the flexible PVC were observed when Bz-beta-CD was added. DEHP migration tests were carried out for the flexible PVC according to the ISO 3826:1993(E) test method, and the quantity of migrated DEHP was then determined with UV-vis spectroscopy. It was found that the addition of Bz-beta-CD decreases the levels of DEHP migration from the flexible PVC samples by almost 40%. We investigated the molecular interaction between Bz-beta-CD and DEHP using molecular mechanics simulations, and we conclude that this reduction in DEHP migration is due to the formation of stabilized pi-pi attractive association and inclusion complexes of Bz-beta-CD and DEHP in flexible PVC.