Search

The removal of unsymmetrical dimethylhydrazine (UDMH) has long been a concern because of its harmful effect on the environment and humans. This study aimed to prepare a novel graphene oxide/O-carboxymethyl chitosan (GO/CMC) composite adsorbent using the solution-blending method for the removal of UDMH from wastewater. The prepared GO/CMC was systematically characterized by Fourier-transform infrared, Raman, scanning electronic microscopy, transmission electron microscopy, thermogravimetric, and zeta potential analyses. The effects of initial pH, temperature, adsorbent dosage, initial concentration, contact time, and recyclability on the UDMH adsorption behaviour of GO/CMC were studied. The adsorption kinetics was consistent with the pseudo-second-order kinetics model, and the adsorption process was mainly controlled by chemisorption. Adsorption isotherms indicated that the adsorption of UDMH by GO/CMC followed the Langmuir adsorption isotherm. The adsorption mechanisms were mainly electrostatic attraction, hydrogen bonding, and surface complexation. Furthermore, GO/CMC composites can be used as a renewable and eco-friendly adsorbent for the removal of UDMH wastewater. The designed GO/CMC composites exhibited a relatively satisfactory recyclability and removal efficiency after five adsorption-desorption cycles.

In this study, mesoporous TiO2 with various hydrolysis rates were prepared and combined with H2O2 for the photodegradation of unsymmetrical dimethylhydrazine (UDMH) under VUV irradiation. Results showed that the mesoporous TiO2 synthesized by the hydrolysis in water (MT100) exhibited a good mesoporous structure and the largest specific surface area (178.85 m2 g−1). Consequently, MT100 showed the best degradation efficiency, with the rate constant (k) for VUV/MT100 and VUV/MT100/H2O2 of 0.0185 and 0.2595 min−1, respectively, which was 1.4 and 4.0 times of that of P25. The addition of H2O2 significantly enhanced the degradation efficiency by photoactivation of H2O2 and the synergistic effect. The rate constant and the mineralization rate (after a 3-h treatment) increased by 13 and 3.8 times when 40 mM H2O2 was added into VUV/MT100. The weak alkaline condition (pH = 9) would facilitate the degradation of UDMH. The ⋅OH was the key oxidizing species in VUV/MT100/H2O2. Eight intermediates were detected during the degradation and the possible pathways of UDMH degradation in VUV/MT100/H2O2 process were proposed. VUV/MT100/H2O2 provides an efficient method to degrade UDMH.

Intrinsic hydrophobicity of polymeric biomedical devices generally causes adverse complications (i.e. thrombosis formation). In this study, biomimetic surface modification is conducted on different hydrophobic substrates (PP, PET and PTFE) by physisorption and subsequent UV induced chemical crosslinking of a ternary methacrylate copolymer bearing phosphorylcholine (PC), cholesteryl (Chol) and azidophenyl (Az) side groups, poly(MPC-co-CMA-co-AzMA) (PMCA). X-ray photoelectron spectrophotometer (XPS), atomic force microscopy (AFM) and water contact angle (WCA) measurements are used to monitor the changes in chemical composition, morphology and wetting behavior of the polymeric substrate surfaces before and after surface modification. The protein adsorption and platelet adhesion experiments are also performed to assess its antifouling properties. The results show that the synergistic contribution of physical anchor of Chol groups and chemical crosslinking of Az moieties leads to the formation of a highly crosslinked cell outer membrane mimetic coating with relatively uniform and dense nano-granular surface textures. The resultant PMCA modified surface exhibits greatly enhanced hydrophilicity due to the enrichment of hydrophilic phosphorylcholine moieties on the outer layer of PMCA coating. Particularly, compared with poly(MPC-co-CMA) (PMC) and poly(MPC-co-AzMA) (PMA) coatings, PMCA coating possesses good surface stability and interfacial adhesion performance. It provides the polymeric substrates with significantly improved antifouling property. The amounts of proteins and platelets adsorbed or adhered on PMCA modified surfaces could be reduced by at least 85% and 97% after incubation for 48 h, respectively. It offers a facile way to fabricate robust antifouling surface for the improvement of the biocompatibility of polymeric biomedical devices.

A non-fluorinated polymeric alkylsilane, poly(isobutyl methacrylate- co -3-methacryloxypropyltrimethoxysilane) (PIT), is designed and synthesized to replace the commercial long-chain perfluoroalkylsilane (FAS) water-repellent agent. The superhydrophobic polyester fabrics are prepared by anchoring sol-gel derived silica nanoparticles onto alkali-treated polyester fabric surfaces and subsequently hydrophobilizing with PIT, using FAS as control. The surface chemical composition, surface morphology, wetting behavior and durability of the modified polyester fabrics are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrophotometer (XPS) and video-based contact angle goniometer, respectively. The results show that a porous silica layer could be successfully fabricated onto the surface of polyester fabric through base-catalyzed sol-gel process with tetraethoxysilane (TEOS) as precursor, incorporating additional nanostructured roughness essential for superhydrophobicity. At the same time, such a silica primer layer could provide both secondary reactive moieties (−Si − OH) for the subsequent surface hydrophobization and acceptable adhesion at the silica-polyester fabric interface. When silica modified polyester fabric (SiO 2 @ fabric) is hydrophobized by PIT solution (10 mg/mL), excellent water-repellency could be obtained. The water contact angle is up to 154° and the sliding angle is about 5°. Compared with small molecule water-repellent agent FAS, PIT modified SiO 2 @ fabric exhibits greatly improved solvent resistance under ultra-sonication, abrasion and simulated laundering durability. The anti-stain property of PIT-modified SiO 2 @ fabric is also evaluated by using different aqueous colored solutions.