A new strategy was proposed that simultaneously improves the pervaporation (PV) performance and solvent resistance via the construction of a movable crosslinked structure in ethyl ...cellulose/polyvinylidene fluoride (EC/PVDF) composite membrane for the purpose of benzene/cyclohexane separation. Based on the molecular design of the macrocyclic compound cyclodextrin, polyrotaxane crosslinking agent (PR=) with a special sliding/rotating property and cavity structure was successfully synthesized. Furthermore, for convenient comparative study, cyclodextrin crosslinking agent (CD=) with cavity structure bereft of a sliding/rotating property and pentaerythritol triacrylate (PETA) without sliding/rotating property and cavity structure were prepared. The composite membranes were fabricated with crosslinking modified EC as active layer, together with PVDF support layer. The molecular structure and microstructure were confirmed. The pervaporation and swelling performance of the fabricated membranes for benzene/cyclohexane were investigated. PR= modified membranes showed good solvent resistance and exhibited a flux of 4332 g·m
−2
·h
−1
and separation factor of 6.26, which was higher than CD= and PETA modified membranes. The results were attributed to the facilitated transport behavior, which was markedly related with the sliding/rotating property and cavity structure of polyrotaxane (PR). The related research provides interesting suggestions for PV membrane design for the separation of organic mixtures.
Desalination of brackish water and purification of drinking water still pose several challenges. Combination of in-situ hydrolysis and condensation of tetraethyl orthosilicate (TEOS) in polyamic acid ...(PAA) solution along with imidization reaction provide a novel polyimide/SiO2 (PI/SiO2) membrane. This is the first synthesis of a PI nanofiltration (NF) membrane with three-dimensional (3D) water channels, ultra-thin skin layer (30 ± 2 nm), and high flux at low operating pressure, by one-step phase inversion method. There was no additional requirement of an acid, since PAA served as a catalyst. The SiO2 cross-linked network provided the skeletal support, due to hydrogen bonding between PAA-PI and silicon hydroxyl groups. The fabricated PI/SiO2 membrane demonstrated a water contact angle of 45°, pore size of 1.05 ± 0.15 nm, Zeta potential of −30 mV, and tensile strength of 2.24 MPa when under optimized conditions. The loose PI/SiO2 NF membrane exhibited salt rejection in the sequence of Na2SO4 (87%)>MgSO4 (67%)>NaCl (41%)>MgCl2 (37%), which was consistent with size exclusion and Donnan exclusion effects. In particular, the water flux of 20.4 L/(m2 h bar) was about 4–15 times higher than that of universal PI-NF membranes. The membrane also exhibited excellent stability for over six days when used for separation. Furthermore, the membrane showed excellent dye (Rose Bengal (RB), Brilliant Blue G (BBG), Amido Black (AB)) rejection of over 90%. To conclude, this work paves a new pathway for the fabrication of PI-NF membranes for efficient NF separation.
Preparation and separation schematic diagram of PI/SiO2 NF membranes. Display omitted
•The loose PI/SiO2 NF membrane can be obtained by one-step phase inversion.•The SiO2 nanoparticles could serve as a skeletal support of membrane.•An ultra-thin skin layer thickness of 30 ± 2 nm could be generated.•The flux of 20.4 L/(m2 h bar) is 4~15 times higher than universal PI-NF membranes.•The membrane exhibited an excellent stability over six days long-term separation.
Highway tunnel entrance is not only the exposed part of mountain in the tunnel engineering, but also an integral part of the highway breaking through the mountain. On the premise of ensuring the ...safety of tunnel entrance, it is important to realize the unity of safety and practical “stability” and landscape greening “beauty” of the expressway tunnel through reasonable aesthetic landscape greening design. In combination with the topographic and geomorphological conditions as well as the regional and humanistic conditions of the highway tunnel portal area, this paper introduces the cultural landscape and plant greening engineering of highway tunnel entrance by reference to the successful experience of tunnel entrance landscape greening, and puts forward the requirements for landscape and greening technology of highway tunnel entrance in accordance with the provisions of relevant regulations.
Under the background of the integration of transport industry and tourism industry, the highway can expand many functions such as ecology, tourism, scenic view, nostalgia and so on. By this, it ...replaces the traditional single road traffic function, organically combine the appreciation of natural landscape, ecological environment protection and the pursuit of human history, and closely connects the highway with the tourist area. Relying on the typical projects and the regional characteristics of rich tourism resources, this paper deeply digs the regional natural ecological elements of the “Home of Mountains and Rivers” and the regional cultural characteristics of “Millennium Poetry Road”, and connects the pearls on the golden tourism line. This paper aims to study construction of the fine road of tourism traffic in mountains, rivers and poetry road under the background of the integration of traffic and tourism, and provides practical exploration and reference for the integrated development of highway and tourism.
Service area is an important part of expressway. The construction of characteristic thematic service area is of great significance for improving highway service facilities and ensuring highway ...traffic safety. Through the study of location, facility layout, landscape design and architectural design of the characteristic service area, this paper analyzes the key points of the construction of the characteristic service area, which is helpful for the design and construction of the open and multi-functional service area. On the basis of meeting the functional requirements of the service area, it is necessary to adapt measures to local conditions, create the service area landscape with distinct personality and outstanding characteristics, and show the regional culture.
Combined with the characteristics and actual needs of expressway project, the demonstration application of green highway construction is mainly carried out from four aspects: “building traffic ...infrastructure system integrated into natural landscape”, “promoting green construction technology of environmental protection, energy saving and high efficiency”, “creating tourism type Expressway demonstration project” and “promoting safety intelligent construction and control technology”, forming “respecting nature and smooth” The supporting technology system should be established for the green road of “nature, nature protection and integration”, and Zihui expressway should be built into a demonstration project of green road in mountain area which is coordinated and integrated with the natural environment.
Selective filtration of dyes and inorganic salts is a challenge for the treatment of textile wastewater containing high salt contents. In this study, selective separation performance of PI/SiO2 ...nanofiltration (NF) membrane for dye/inorganic salt mixtures was substantially improved through directional modulation of its thermal treatment parameters after phase inversion. After thermal modification, the pore size, porosity and roughness were reduced, and the mechanical strength was improved. The PI/SiO2 membrane under optimized thermally-modified conditions (M6, heat treatment conditions: 50 °C for 8 min) possessed high porosity of 79.95%. Besides, the thermally-modified PI/SiO2 membrane revealed high water permeance of 152.87 L m−2 h−1·bar−1 with efficient rejection performance for a variety of typical dyes. In single dye filtration tests, the thermally-modified PI/SiO2 membrane displayed high rejection (>90%) for Coomassie Brilliant Blue (CBB), Congo Red (CR), Trypan Blue (TB) and Direct Black 38 (DB 38), and exhibited excellent permeance (84.21–133.76 L m−2 h−1·bar−1). In addition, the thermally-modified PI/SiO2 membrane could selectively separate dyes and inorganic salts. The membrane exhibited high dye rejection (>90%) and low inorganic salt rejection (<10%) for the filtration tests of CR + NaCl/Na2SO4 and CBB + NaCl/Na2SO4 mixed solutions (2 g L−1). In particular, the permeances of the thermally-modified PI/SiO2 membrane (89.45–130.21 L m−2 h−1·bar−1) were higher than those of many contemporary NF membranes used for the same type of dye/inorganic salt separation. In conclusion, the present study presents a simple, inexpensive and effective thermal modification means, which shows great promise in the selective filtration of industrial dye wastewater.
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•Heat treatment parameters of PI/SiO2 membranes after phase inversion were optimized.•Thermal modification reduced the roughness, pore size and porosity of the membranes.•The thermally modified membrane exhibited high permeance and rejection of four dyes.•The thermally modified membrane can selectively separate dye and inorganic salt.•The thermally modified membrane showed high permeance for dye/salt separation.
Efficient separation of dyes and salts from textile wastewater is still a great difficulty. Herein, a tris(hydroxymethyl) aminomethane (Tris)-modified polyimide (PI) membrane was developed, which was ...effective, easy-to-fabricate, and versatile with high-separation-selective performance. With the introduction of Tris, the roughness, hydrophilicity and negative zeta potential of the membranes were increased, and the pore size was reduced. At 3 bar, the representative membrane exhibited high permeate flux (176–206 L·m−2·h−1) and high rejection (>97 %) to four common dyes and excellent solvent resistance to seven organic solvents, indicating that PI/Tris membrane had potential for application in dye wastewater containing complex organic solvents. Furthermore, the PI/Tris-modified membrane could selectively separate dyes and salts, and presented high dye rejection (>99 %) and low salt rejection (≈7 %) as well as high selectivity (separation factor = 103) for Direct Black 38/NaCl mixture. In particular, the PI/Tris-modified membranes outperformed many contemporary separation membranes in terms of separation efficiency of dye/salt mixtures. In summary, this PI/Tris membrane developed in this study has a promising future in the field of industrial dye wastewater treatment.
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•Tris incorporating improved roughness, negative zeta potential and hydrophilicity.•PI/Tris membrane showed high permeance and rejection to four typical dye solutions.•PI/Tris membrane showed solvent-resistant performance to seven organic solvents.•PI/Tris membrane can effectively and selectively separate dye and inorganic salt.
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•Solvent-resistant PI/SiO2 NF membrane was fabricated by phase inversion.•PAA provided acidic environment to achieve in situ cross-linking.•Organic/inorganic skeleton structure ...fabricated by a biomineralized strategy.•The membrane showed high separation efficiency for water and solvent systems.•The membrane showed excellent structural stability.
Nowadays, the separation efficiency and stability of nanofiltration (NF) membrane are of widespread concern. Inspired by the biomineralization phenomenon and its unique structure with siliceous framework, a polyimide (PI) NF membrane decorated with “silica hard phase-polymer soft phase” 3D interwoven sponge bionic structure was fabricated via a simple and effective one-step phase inversion strategy. The obtained membranes demonstrated high pure water permeability of 65 L/(m2·h) and rejections of Na2SO4 (91.55%) and NaCl (30.21%) at 0.4 MPa, respectively. Moreover, siliceous sponge-like structures were determined by SEM analysis, with the degree of cross-linking after membrane pore regulated as high as 88.89%. The integrity and long-term stability of the membrane in different organic solvents, including methanol, cyclohexane, acetone, ethyl acetate, n-heptane, absolute ethanol and toluene were maintained for 72 h at 0.8 MPa. Furthermore, the PI/SiO2 membrane with siliceous sponge biologically unique structure gives rise to a scope of bioinspired membranes and shows promising prospect for the treatment of solutions in extreme environments.
The service facilities along the expressway are designed to meet the needs of drivers and passengers, which is directly related to the convenient travel of the general public. In order to break ...through the rigid construction mode of expressway service facilities, this paper analyses the micro terrain design and construction of different types of expressway service facilities, and discusses the micro terrain construction of expressway service facilities, so as to improve the view of the landscape and the sense of physical and mental pleasure of the drivers, passengers and service personnel, eliminate security risks and improve service efficiency.
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