Zeolitic Imidazole Framework (ZIF)-Sponge Composite for Highly Efficient U(VI) Elimination.

Herein, a zeolitic imidazole framework (ZIF-67) composite was prepared by a rapid, simple and inexpensive situ hybridization technique applying polyurethane sponge (PU) as support, which was designated as ZIF-67-PU. The ZIF-67 nanoparticle was successfully supported on the surface of sponge skeletons mainly through electrostatic attraction as well as probable π-π stacking interactions with PAM modification of the sponge. The resultant ZIF-67-PU exhibited a remarkably enhanced U(VI) elimination capacity of 150.86 mg∙g-1 on the basis of the Langmuir isotherm model, in comparison to pristine sponge. Additionally, the mechanism for U(VI) elimination was mainly achieved through the complex reaction between C-N(H)/-OH groups in ZIF-67 and U(VI), based on XPS investigations. ZIF-67-PU represents a simple, feasible and low-cost disposal option for preparing ZIF-coated sponges of any shape that can enhance the U(VI) elimination capacity. Furthermore, this approach can be widely applied to the preparation of various kinds of MOF-sponges through this situ hybridization technique.

Piezoresistive Pressure Sensor Based on a Conductive 3D Sponge Network for Motion Sensing and Human-Machine Interface.

Flexible sensors have attracted increasing attention owing to their important applications in human activity monitoring, medical diagnosis, and human-machine interaction. However, the rational design of low-cost sensors with desirable properties (e.g., high sensitivity and excellent stability) and extended applications is still a great challenge. Herein, a simple and cost-effective strategy is reported by immersing polyurethane (PU) sponge in graphene oxide solution followed by in situ chemical reduction to construct a reduced graphene oxide (RGO)-wrapped PU sponge sensor. Ascribed to the excellent compressive resilience of PU sponge and an electrically conductive RGO layer, the constructed flexible sensor exhibits satisfactory sensing performance with high sensitivity (17.65 kPa-1) in a low-load range (0-3.2 kPa), a wide compression strain range (0-80%), and reliable stability (8000 cycles). In addition, these sensors can be successfully applied to monitor human movements and identify the weight of objects. Through the use of a sensor array integrated with a signal acquisition circuit, the reasonably designed sensors can realize tactile feedback via mapping real-time spatial distribution of pressure in complicated tasks and show potential applications in flexible electronic pianos, electronic skin, and remote real-time control of home electronics.

The adsorbent preparation of FeOOH@PU for effective chromium (VI) removal.

A novel adsorbent (FeOOH@PU) for hexavalent chromium [Cr(VI)] removal was synthesized using a polyurethane foam (PU) and FeOOH via a facile one-step method. Scanning electron microscopy (SEM), FTIR, X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS) characterized the adsorbent. The influence of environmental factors was investigated to evaluate the adsorption behavior for Cr(VI). Furthermore, adsorption dynamic and adsorption isotherm models described the adsorption performance. This adsorbent also treated electroplating wastewater and remediated simulated Cr(VI) contaminated soil. The adsorbent effectively removed Cr(VI) with a high adsorption rate; its equilibrium rate constant was 13 times that of FeOOH. Cr(VI) removal was a monolayer adsorption process and the maximum adsorption capacity of FeOOH@PU reached 34.9 mg Cr/g. Electrostatic attraction was the mechanism of Cr(VI) removal. Electroplating wastewater became clear and the Cr(VI) concentration decreased from 9.76 to 0.042 mg/L after treatment with FeOOH@PU. Cr enrichment in rice seedlings grown in remediated soil decreased from 7.687 to 6.295 mg Cr/kg. These results suggested that FeOOH@PU was a promising adsorbent for Cr(VI) removal and Cr(VI) stabilization.

Stable photodegradation of antibiotics by the functionalized 3D-Bi2MoO6@MoO3/PU composite sponge: High efficiency pathways, optical properties and Z-scheme heterojunction mechanism.

The designation and fabrication of heterogeneous photocatalyst with superior redox capability is an important technique for emerging pollutants treatment. In this study, we designed the Z-scheme heterojunction of stable 3D-Bi2MoO6@MoO3/PU, which could not only accelerate the migration and separation in photogenerated carriers, but also stabilize the separation rate of photo-generation carriers. In the Bi2MoO6@MoO3/PU photocatalytic system, 88.89% of oxytetracycline (OTC, 10 mg L-1) and 78.25%-84.59% of multiple antibiotics (SDZ, NOR, AMX and CFX, 10 mg L-1) could be decomposed within 20 min under the optimized reaction condition, revealing the superior performance and potential application value. Specifically, the morphology, chemical structure and optical properties detection of Bi2MoO6@MoO3/PU greatly affected the direct Z-scheme electron transferring mode in the p-n type heterojunction. Besides, the ·OH, h+, ·O2- dominated the photoactivation process through ring-opening, dihydroxylation, deamination, decarbonization and demethylation in OTC decomposition. Expectantly, the stability and universality of Bi2MoO6@MoO3/PU composite photocatalyst would further broaden the practical application and demonstrated that the potential of photocatalytic technique in antibiotics pollutants for wastewater remediation.

Mussel-Inspired and In Situ Polymerization-Modified Commercial Sponge for Efficient Crude Oil and Organic Solvent Adsorption.

Oil spills and pollution of oily wastewater from the industrial field have not only caused serious economic losses but also imposed a huge threat to human beings. To solve these issues, the development of advanced materials and technologies for the purification of oily wastewater has garnered great concern and become a central topic. Hence, a superhydrophobic polyurethane (PU) sponge adsorbent is designed via mussel-inspired coatings by double bonds to PU sponge, followed by in situ polymerization with 1-hexadecene. The prepared PU sponge adsorbent (PU@DB@16ene sponge) showed outstanding mechanical properties including low density, high porosity, and compression recovery ability. Moreover, the prepared PU@DB@16ene sponge showed excellent adsorption of oils and organic solvents (up to 187 g g-1) and exhibited superior recyclability. Particularly, when the PU@DB@16ene sponge was applied in the continuous and rapid separation of oils and organic solvents, it still showed desired properties at a rapid velocity of 8.3 L m-3 s-1. Additionally, the PU@DB@16ene sponge could not only adsorb organic solvents in laboratories but also adsorb crude oil and industrial waxy oil in practice. Therefore, we proposed a simple and convenient method to construct PU sponge absorbents with great application prospects, which would be highly valuable for crude oil and organic solvents cleanup.

A Robust Superhydrophobic Polyurethane Sponge Loaded with Multi-Walled Carbon Nanotubes for Efficient and Selective Oil-Water Separation.

The influence of different coupling agents and coupling times on the wettability of a polyurethane (PU) sponge surface were optimized. Octadecyltrichlorosilane (OTS) was selected as the optimal coupling agent to prepare the superhydrophobic sponge. The superhydrophobic sponge was prepared in one step, which has the advantages of simple operation and enhanced durability. The superhydrophobic sponge was characterized by scanning electron microscopy, Teclis Tracker tensiometry, and Fourier transform infrared (FT-IR) spectrophotometry. The water contact angle increased from 64.1° to 151.3°, exhibiting ideal superhydrophobicity. Oils and organic solvents with different viscosities and densities can be rapidly and selectively absorbed by superhydrophobic sponges, with an absorption capacity of 14.99 to 86.53 times the weight of the sponge itself, without absorbing any water. Since temperature affects the viscosity and ionic strength of oil, and influences the surface wettability of the sponges, the effect of temperature and ionic strength on the oil absorption capacity of the superhydrophobic sponges was measured, and its mechanism was elucidated. The results showed that the absorptive capacity retained more than 90% of the initial absorptive capacity after repeated use for 10 times. Low-cost, durable superhydrophobic sponges show great potential for large-scale oil-water separation.

Modification of Polyurethane Sponge Based on the Thiol-Ene Click Reaction and Its Application for Oil/Water Separation.

A polyurethane (PU) sponge with hydrophobic/oleophilic property was prepared based on the thiol-ene click reaction, which was a simple method with only one step. Photopolymerization was induced through UV light on the sponge surface in a homogeneous solution containing polyethylene glycol diacrylate, pentaerythritol (mercaptoacetic acid) ester, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and octadecyl methacrylate. The as-prepared sponge possessed excellent selective for oil from various types of oil/water mixtures. It also had a high absorption capacity for toluene, >21 times its self-weight, and it had about 20 times its self-weight for vegetable oil, even after five extrusion-adsorption cycles, presenting a good recyclability. It created a new method to prepare oil/water separation sponge.

Ultrasensitive and Highly Compressible Piezoresistive Sensor Based on Polyurethane Sponge Coated with a Cracked Cellulose Nanofibril/Silver Nanowire Layer.

With the rapid development of flexible wearable electronics, a piezoresistive sensor with low detection limit and wide strain sensing range turns out to be a great challenge for its application in this field. Here, a cracked cellulose nanofibril/silver nanowire (CA) layer-coated polyurethane (PU) sponge was acquired through a simple dip-coating process followed by precompression treatment. The electrical conductivity and mechanical property of the conductive CA@PU sponge could be effectively tuned through changing the dip-coating number. As a piezoresistive sensor, the sponge exhibited the capability of detecting both small and large motions over a wide compression strain range of 0-80%. Based on the "crack effect", the sensor possessed a detection limit as low as 0.2% and the gauge factor [GF, GF = (Δ R/ R0)/ε, where Δ R, R0, and ε represent the instantaneous resistance change, original resistance, and strain applied, respectively] was as high as 26.07 in the strain range of 0-0.6%. Moreover, the "contact effect" enabled the sensor to be applicable for larger strain, and the GF decreased first and then became stable with increasing compression strain. In addition, frequency- and strain-dependent sensing performances were observed, demonstrating that the sensor can respond reliably to different applied frequencies and strains. Furthermore, the sensor displayed exceptional stability, repeatability, and durability over 500 cycles. Finally, the sensor could be applicable for the detection of various human bodily motions, such as phonation, stamping, knee bending, and wrist bending. Most importantly, the sponge also exhibited great potential for the fabrication of artificial electronic skin. Herein, the conductive CA@PU sponge will undoubtedly promote the development of high-performance flexible wearable electronics.

In situ reduced graphene oxide-based polyurethane sponge hollow tube for continuous oil removal from water surface.

Graphene oxide (GO) was prepared by using the natural graphite as raw materials via the modified Hummers' method and ultrasonic stripping method. GO was reduced online after its anchoring on the surface of polyurethane sponges by a dip-coating method, then in situ reduced graphene oxide-based polyurethane (IRGOPU) sponges were fabricated. The characterizations of IRGOPU sponges were investigated using Field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and contact angle measurement. The IRGOPU sponges had an adsorption capacity for a broad range of oils up to 21.7 ~ 55 g/g. A simulation experiment of large-scale oil spill using a simple IRGOPU sponge hollow tube component was designed. The process of continuous oil removal from water surface was quick and effective, and the oil/water separation efficiency could be up to 99.6%. The results indicated that the IRGOPU sponge hollow tube may be an optimum candidate for the oil/water separation of large-scale oil spill.