Extraordinary Superhydrophobic Polycaprolactone-Based Composite Membrane with an Alternated Micro-Nano Hierarchical Structure as an Eco-friendly Oil/Water Separator

Phographene as a new carbon allotrope for adsorption and detection of SO2, AsH3, NO2, CF3H, and CO2 air pollutant gaseous species

CONTEXT

Phographene and its family member structures are of the newly proposed semiconductors for detection of chemicals. That is, in this project, the potential of using α-phographene (α-POG) both for adsorption and detection of five types of the most important air pollutant gases containing SO2, AsH3, CF3H, NO2, and CO2 species were investigated.  The results of the time dependent density functional theory (TD-DFT) calculations indicate that during the adsorption of NO2, and SO2 by the sorbent, big redshifts occur (up to 866.2 nm, and 936.5, respectively) resulting in considerable changes in the orbitals and the electronic structures of the systems. Moreover, the results of the thermodynamic calculations reveal that α-POG could selectively adsorb SO2, NO2, and AsH3 gases (with different orders), but it could not adsorb the two other gases.Finally, the outcome of the band gap calculations shows that between all mentioned gases, α-POG could selectively detect the presence of SO2, and then NO2; while, this nanosheet could not sense the existence of AsH3, CF3H, or CO2 gases.

METHODS

All of the calculations were carried out by using the Gaussian 03 quantum chemical package. In addition, the physiochemical parameters were extracted from the output files for further calculations. Studies on all saddle points and the following calculations were performed applying the B3LYP/6-311g(d,p) level of theory.

Engineered eco-friendly composite membranes with superhydrophobic/hydrophilic dual-layer for DCMD system

Considerable advancements have been made in the development of hydrophobic membranes for membrane distillation (MD). Nonetheless, the environmentally responsible disposal of these membranes poses a critical concern due to their synthetic composition. Herein, an eco-friendly dual-layered biopolymer-based membrane was fabricated for water desalination. The membrane was electrospun from two bio-polymeric layers. The top hydrophobic layer comprises polycaprolactone (PCL) and the bottom hydrophilic layer from cellulose acetate (CA). Additionally, silica nanoparticles (SiO2 NPs) were electrosprayed onto the top layer of the dual-layered PCL/CA membrane to enhance the hydrophobicity. The desalination performance of the modified PCL-SiO2/CA membrane was compared with the unmodified PCL/CA membrane using a direct contact membrane distillation (DCMD) unit. Results revealed that silica remarkably improves membrane hydrophobicity. The modified PCL-SiO2/CA membrane demonstrated a significant increase in water contact angle of 152.4° compared to 119° for the unmodified membrane. In addition, PCL-SiO2/CA membrane has a smaller average pore size of 0.23 ± 0.16 μm and an exceptional liquid entry pressure of water (LEPw), which is 3.8 times higher than that of PCL/CA membrane. Moreover, PCL-SiO2/CA membrane achieved a durable permeate flux of 15.6 kg/m2.h, while PCL/CA membrane showed unstable permeate flux decreasing approximately from 25 to 12 kg/m2.h over the DCMD test time. Furthermore, the modified PCL-SiO2/CA membrane achieved a high salt rejection value of 99.97% compared to a low value of 86.2% for the PCL/CA membrane after 24 h continuous DCMD operation. In conclusion, the proposed modified PCL-SiO2/CA dual-layer biopolymeric-based membrane has considerable potential to be used as an environmentally friendly membrane for the MD process.

The Design of PAN-Based Janus Membrane with Adjustable Asymmetric Wettability in Wastewater Purification

In this paper, an environmentally friendly polyacrylonitrile-based (PAN-based) composite membrane with a Janus structure for wastewater treatment was successfully fabricated. To achieve the optimum adsorption of PAN-based Janus composite membrane, the asymmetric wettability was regulated through electrospinning, resulting in TiO2 modifying PAN as the hydrophilic substrate layer, and PCL gaining a different thickness as the hydrophobic layer. The prepared Janus composite membrane (PAN/TiO2-PCL20) showed excellent oil/water separation performance for diverse surfactant-stabilized oil-in-water emulsions. For n-hexane-in-water emulsion, the permeate flux and separation efficiency reached 1344 L m-2 h-1 and 99.52%, respectively. Even after 20 cycles of separation, it still had outstanding reusability and the separation efficiency remained above 99.15%. Meanwhile, the PAN/TiO2-PCL20 also exhibited an excellent photocatalytic activity, and the removal rate for RhB reached 93.2%. In addition, the research revealed that PAN/TiO2-PCL20 possessed good mechanical property and unidirectional water transfer capability. All results indicated that PAN/TiO2-PCL20 with photocatalysis and oil/water separation performance could be used for practical complex wastewater purification.

"Rigid-Flexible" Anisotropic Biomass-Derived Aerogels with Superior Mechanical Properties for Oil Recovery and Thermal Insulation

Aerogels with low density, high mechanical strength, and excellent elasticity have a wide potential for applications in wastewater treatment, thermal management, and sensors. However, the fabrication of such aerogels from biomass materials required complex preparation processes. Herein, a sustainable and facile strategy was reported to construct lignin/cellulose aerogels (LCMA) with three-dimensional interconnected structures by introducing homologous lignin with a polyphenyl propane structure as a structural enhancer through a top-down directional freezing approach, prompting a 2036% enhancement in compressive modulus and an 8-12-fold increase in oil absorption capacity. In addition, the hydrophobic aerogels with superelasticity were achieved by combining the aligned polygon-like structure and flexible silane chains, which exhibited remarkable compressional fatigue resistance and superhydrophobicity (WCA = 168°). Attributed to its unique pore design and surface morphology control, the prepared aerogel exhibited excellent performance in immiscible oil-water separation and water-in-oil emulsion separation. Due to the ultra-low density (8.3 mg·cm-3) as well as high porosity (98.87%), the obtained aerogel showed a low thermal conductivity (0.02565 ± 0.0024 W·m-1·K-1), demonstrating a potential in insulation applications. The synthetic strategy and sustainability concept presented in this work could provide guidance for the preparation of advanced biomass-based aerogels with unique properties for a wide range of applications.

Polycaprolactone-blended cellulose acetate thin-film composite membrane for dairy waste treatment using forward osmosis

In recent years new sustainable technology for wastewater treatment has emerged, and among them, forward osmosis (FO) has gained importance. FO utilizes osmotic pressure difference across the semipermeable membrane as the driving force to concentrate the wastewater. Further, the surface and physical properties of the semipermeable FO membrane play a crucial role during the FO process in reducing the internal concentration polarization. In general, FO membranes are prepared using cellulose acetate (CA) polymer due to their high hydrophilic nature. However, CA membranes are mechanically unstable for the FO process. Hence, to increase the mechanical strength and flexibility of CA, other polymers are blended along with it. In this present study, we have prepared a phase-inversion membrane using CA blended with polycaprolactone (PCL) polymers. Further, to increase the hydrophilicity of the membrane, a thin-film composite (TFC) layer of polyamide is coated using interfacial polymerization. To increase the antifouling properties of the membrane, graphene oxide (GO) and copper oxide (CuO) nanoparticles (NPs) are incorporated inside the TFC matrix. The prepared NPs and membrane were characterized using Fourier-transform infrared spectroscopy (FTIR), wide-angle X-ray scattering (WAXD), and contact angle. Further, the GO-CuO incorporated TFC coating has improved the hydrophilicity and antifouling properties of the membrane. It was observed that the water flux has increased up to 5 LMH, and reverse solute flux has reduced to 4 GMH. Further, the membrane was utilized to concentrate in situ prepared dairy waste. It was observed that after 60 min of the FO process, the concentration of dairy waste had increased to 23%, with a concentration factor of 0.903. Thus, a prepared TFC phase inversion membrane is potential for dairy wastewater treatment.

Phytic acid and graphene oxide functionalized sponge with special-wettability and electronegativity for oil-in-water emulsion separation in single-step

Developing an emulsion separation material with one-step in-situ purifying capability and improved security in applications, especially for subsequent scale-up, is valuable but remains a challenge. Herein, the amphiphilic sponge (PA@RGO@MS) was prepared via impregnation and in-situ growth of the negatively charged hydrophilic phytic acid (PA) and the hydrophobic reduced graphene oxide (RGO) on the surface of the melamine sponge (MS) and applied in emulsion purification. The mechanics, wettability, absorption performance of the PA@RGO@MS were analyzed to identify its potential for stable demulsification. Results show that the PA@RGO@MS could purify emulsions (turbidity removal rate = 99.7%; TOC removal rate = 94.14%) in-situ in one step by simple shock absorption, profited from the hydrophilic and demulsification capability of PA, oil absorption of RGO, and wide reaction and storage space of MS. Targeting the emulsion with distinct properties (density, viscosity, and concentration) of the oil phase, the PA@RGO@MS could efficiently enable the purification. Meanwhile, the powerful flame-retardant granted from PA ensures the safe shipment and storage of sponges. The favorable cyclability (turbidity removal rate > 98.5% and TOC removal rate > 89.5% after 10 cycles) and diversified operating modes enhance the practical value of the PA@RGO@MS.

General Suspended Printing Strategy toward Programmatically Spatial Kevlar Aerogels

Aerogels represent a kind of nanoporous solid with immense importance for a plethora of diverse applications. However, on-demand conformal shaping capacity remains extremely challenging due to the strength unfavorable during aerogel processing. Herein, a universal microgel-directed suspended printing (MSP) strategy is developed for fabricating various mesoporous aerogels with spatially stereoscopic structures on-demand. As a proof-of-concept demonstration, through the rational design of the used microgel matrix and favorable printing of the Kevlar nanofiber inks, the Kevlar aerogels with arbitrary spatial structure have been fabricated, demonstrating excellent printability and programmability under a high-speed printing mode (up to 167 mm s^-1). Furthermore, the custom-tailored Kevlar aerogel insulator possessing superior thermal insulation attribute has ensured normal discharge capacity of the drone even under a harsh environment (-30 °C). Finally, various types of spatial 3D aerogel architectures, including organic (cellulose, alginate, chitosan), inorganic (graphene, MXene, silica), and inorganic-organic (graphene/cellulose, MXene/alginate, silica/chitosan) hybrid aerogels, have been successfully fabricated, suggesting the universality of the MSP strategy. The strategy reported here proposes an alternative for the development of various customized aerogels and stimulates the inspiration to truly arbitrary architectures for wider applications.

Room-temperature fabrication of superhydrophobic covalent organic framework (COF) decorated cotton fabric for high-flux water-in-oil emulsion separation

We report the preparation of a two-dimensional superhydrophobic covalent organic framework (COF)-coated cotton fabric via a rapid one-step method at room temperature. The COF-coated fabric was found to have stable superhydrophobicity and remarkable water-in-oil emulsion separation capacity with ultra-high flux under only gravity.