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Special Issue "Porous Materials for Water Technology"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 August 2016)

Special Issue Editors

Guest Editor
Prof. X.S. George Zhao

School of Chemical Engineering, The University of Queensland, St. Lucia, Brisbane QLD 4072, Australia
Institute of Materials for Energy & Environment, School of Materials Science and Engineering, Qingdao University, Qingdao 266071, China
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Guest Editor
Prof. Hongliang Li

Institute of Materials for Energy & Environment, School of Materials Science and Engineering, Qingdao University, Qingdao 266071, China
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Guest Editor
Prof. Peizhi Guo

Institute of Materials for Energy & Environment, School of Materials Science and Engineering, Qingdao University, Qingdao 266071, China
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Special Issue Information

Dear Colleagues,

As the name suggests, porous materials are solids (or liquids) containing pores as cavities, channels, and interstices. According to the International Union of Pure and Applied Chemistry (IUPAC), porous materials are classified into three categories: microporous, mesoporous, and macroporous materials with pore sizes less than 2 nm, between 2 and 50 nm, and larger than 50 nm, respectively. In terms of composition, porous materials can be inorganic, or organic, or inorganic–organic composite materials. They are of scientific and technological importance because of the ability of their pore walls to interact with atoms, ions, molecules, and supermolecules, together with the capacity of controllable pore space to load or capture liquid and gas molecules, and solid particles. The tailorable pore size and pore wall surface chemistry enable porous materials to have been used in various applications from daily necessities, such as purifying drinking water by activated carbon or porous ceramics and use in modern industries, for example in petroleum refining. In the water industry, it is not exaggerated to say that every success in the development of water technology, such as water treatment using membrane filtration, wastewater treatment using adsorption and photocatalysis, desalination using reverse osmosis, and electrocapacitive desalination all rely on porous materials.

Collected in this Special Issue are recent research works on using porous materials to solve problems in water technology.

Prof. X.S. George Zhao
Prof. Hongliang Li
Prof. Peizhi Guo
Guest Editors

Manuscript Submission Information

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Keywords

  • Porous Materials
  • Water purification
  • Wastewater treatment
  • Desalination
  • Photocatalysis
  • Membranes and thin films

Published Papers (7 papers)

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Research

Open AccessFeature PaperArticle Molecular Weight Cut-Off and Structural Analysis of Vacuum-Assisted Titania Membranes for Water Processing
Materials 2016, 9(11), 938; doi:10.3390/ma9110938
Received: 29 September 2016 / Revised: 8 November 2016 / Accepted: 11 November 2016 / Published: 18 November 2016
PDF Full-text (4961 KB) | HTML Full-text | XML Full-text
Abstract
This work investigates the structural formation and analyses of titania membranes (TM) prepared using different vacuum exposure times for molecular weight (MW) cut-off performance and oil/water separation. Titania membranes were synthesized via a sol-gel method and coated on macroporous alumina tubes followed by
[...] Read more.
This work investigates the structural formation and analyses of titania membranes (TM) prepared using different vacuum exposure times for molecular weight (MW) cut-off performance and oil/water separation. Titania membranes were synthesized via a sol-gel method and coated on macroporous alumina tubes followed by exposure to a vacuum between 30 and 1200 s and then calcined at 400 °C. X-ray diffraction and nitrogen adsorption analyses showed that the crystallite size and particle size of titania increased as a function of vacuum time. All the TM membranes were mesoporous with an average pore diameter of ~3.6 nm with an anatase crystal morphology. Water, glucose, sucrose, and polyvinylpyrrolidone with 40 and 360 kDa (PVP-40 kDa and PVP-360 kDa) were used as feed solutions for MW cut-off and hexadecane solution for oil filtration investigation. The TM membranes were not able to separate glucose and sucrose, thus indicating the membrane pore sizes are larger than the kinetic diameter of sucrose of 0.9 nm, irrespective of vacuum exposure time. They also showed only moderate rejection (20%) of the smaller PVP-40 kDa, however, all the membranes were able to obtain an excellent rejection of near 100% for the larger PVP-360 kDa molecule. Furthermore, the TM membranes were tested for the separation of oil emulsions with a high concentration of oil (3000 ppm), reaching high oil rejections of more than 90% of oil. In general, the water fluxes increased with the vacuum exposure time indicating a pore structural tailoring effect. It is therefore proposed that a mechanism of pore size tailoring was formed by an interconnected network of Ti–O–Ti nanoparticles with inter-particle voids, which increased as TiO2 nanoparticle size increased as a function of vacuum exposure time, and thus reduced the water transport resistance through the TM membranes. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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Open AccessArticle ZnO-Layered Double Hydroxide@Graphitic Carbon Nitride Composite for Consecutive Adsorption and Photodegradation of Dyes under UV and Visible Lights
Materials 2016, 9(11), 927; doi:10.3390/ma9110927
Received: 13 August 2016 / Revised: 1 October 2016 / Accepted: 10 November 2016 / Published: 15 November 2016
Cited by 1 | PDF Full-text (3191 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, a ZnO-layered double hydroxide@graphitic carbon nitride composite (ZnO-LDH@C3N4) was synthesized via co-precipitation method with solvothermal treatment. The structure and morphology of ZnO-LDH@C3N4 composite were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy
[...] Read more.
In this work, a ZnO-layered double hydroxide@graphitic carbon nitride composite (ZnO-LDH@C3N4) was synthesized via co-precipitation method with solvothermal treatment. The structure and morphology of ZnO-LDH@C3N4 composite were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopes/transmission electron microscopes (SEM/TEM), N2 adsorption/desorption, ultraviolet visible diffuse reflectance spectroscopy (UV-Vis-DRS), photoluminescence spectrometer (PL) and electrochemical impedance spectroscopy (EIS). The adsorption and photocatalytic properties of ZnO-LDH@C3N4 composite towards the organic dyes: Orange II sodium salt (OrgII, an anionic azo dye) and methylene blue (MB, a cationic azo dye) were investigated. Compared to ZnO-LDH and g-C3N4, the ZnO-LDH@C3N4 composite displayed an excellent performance in both adsorption and photocatalytic degradation of the organic dyes. Moreover, a combination of ZnO-LDH and g-C3N4 significantly improved the photocatalytic performance of ZnO-LDH and g-C3N4 under visible-light irradiation. The adsorption and photocatalytic mechanism were also investigated. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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Open AccessArticle Highly and Stably Water Permeable Thin Film Nanocomposite Membranes Doped with MIL-101 (Cr) Nanoparticles for Reverse Osmosis Application
Materials 2016, 9(11), 870; doi:10.3390/ma9110870
Received: 29 August 2016 / Revised: 26 September 2016 / Accepted: 11 October 2016 / Published: 26 October 2016
Cited by 6 | PDF Full-text (6808 KB) | HTML Full-text | XML Full-text
Abstract
A hydrophilic, hydrostable porous metal organic framework (MOF) material-MIL-101 (Cr) was successfully doped into the dense selective polyamide (PA) layer on the polysulfone (PS) ultrafiltration (UF) support to prepare a new thin film nanocomposite (TFN) membrane for water desalination. The TFN-MIL-101 (Cr) membranes
[...] Read more.
A hydrophilic, hydrostable porous metal organic framework (MOF) material-MIL-101 (Cr) was successfully doped into the dense selective polyamide (PA) layer on the polysulfone (PS) ultrafiltration (UF) support to prepare a new thin film nanocomposite (TFN) membrane for water desalination. The TFN-MIL-101 (Cr) membranes were characterized by SEM, AFM, XPS, wettability measurement and reverse osmosis (RO) test. The porous structures of MIL-101 (Cr) can establish direct water channels in the dense selective PA layer for water molecules to transport through quickly, leading to the increasing water permeance of membranes. With good compatibility between MIL-101 (Cr) nanoparticles and the PA layer, the lab made TFN-MIL-101 (Cr) membranes integrated tightly and showed a high NaCl salt rejection. MIL-101 (Cr) nanoparticles increased water permeance to 2.2 L/m2·h·bar at 0.05 w/v % concentration, 44% higher than the undoped PA membranes; meanwhile, the NaCl rejection remained higher than 99%. This study experimentally verified the potential use of MIL-101 (Cr) in advanced TFN RO membranes, which can be used in the diversified water purification field. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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Open AccessArticle Synthesis and Characterization of N-Doped Porous TiO2 Hollow Spheres and Their Photocatalytic and Optical Properties
Materials 2016, 9(10), 849; doi:10.3390/ma9100849
Received: 28 August 2016 / Revised: 4 October 2016 / Accepted: 11 October 2016 / Published: 19 October 2016
Cited by 3 | PDF Full-text (7297 KB) | HTML Full-text | XML Full-text
Abstract
Three kinds of N-doped mesoporous TiO2 hollow spheres with different N-doping contents, surface area, and pore size distributions were prepared based on a sol–gel synthesis and combined with a calcination process. Melamine formaldehyde (MF) microspheres have been used as sacrificial template and
[...] Read more.
Three kinds of N-doped mesoporous TiO2 hollow spheres with different N-doping contents, surface area, and pore size distributions were prepared based on a sol–gel synthesis and combined with a calcination process. Melamine formaldehyde (MF) microspheres have been used as sacrificial template and cetyltrimethyl ammonium bromide (CTAB) or polyvinylpyrrolidone (PVP) was selected as pore-directing agent. Core–shell intermediate spheres of titania-coated MF with diameters of 1.2–1.6 μm were fabricated by varying the volume concentration of TiO2 precursor from 1 to 3 vol %. By calcining the core–shell composite spheres at 500 °C for 3 h in air, an in situ N-doping process occurred upon the decomposition of the MF template and CTAB or PVP pore-directing surfactant. N-doped mesoporous TiO2 hollow spheres with sizes in the range of 0.4–1.2 μm and shell thickness from 40 to 110 nm were obtained. The composition and N-doping content, thermal stability, morphology, surface area and pore size distribution, wall thickness, photocatalytic activities, and optical properties of the mesoporous TiO2 hollow spheres derived from different conditions were investigated and compared based on Fourier-transformation infrared (FTIR), SEM, TEM, thermogravimetric analysis (TGA), nitrogen adsorption–desorption, and UV–vis spectrophotoscopy techniques. The influences of particle size, N-doping, porous, and hollow characteristics of the TiO2 hollow spheres on their photocatalytic activities and optical properties have been studied and discussed based on the composition analysis, structure characterization, and optical property investigation of these hollow spherical TiO2 matrices. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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Open AccessArticle Solvothermal Synthesis of Hierarchical Colloidal Nanocrystal Assemblies of ZnFe2O4 and Their Application in Water Treatment
Materials 2016, 9(10), 806; doi:10.3390/ma9100806
Received: 15 July 2016 / Revised: 5 September 2016 / Accepted: 20 September 2016 / Published: 29 September 2016
Cited by 2 | PDF Full-text (2218 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hierarchical colloidal nanocrystal assemblies (CNAs) of ZnFe2O4 have been synthesized controllably by a solvothermal method. Hollow ZnFe2O4 spheres can be formed with the volume ratios of ethylene glycol to ethanol of 1:4 in the starting systems, while
[...] Read more.
Hierarchical colloidal nanocrystal assemblies (CNAs) of ZnFe2O4 have been synthesized controllably by a solvothermal method. Hollow ZnFe2O4 spheres can be formed with the volume ratios of ethylene glycol to ethanol of 1:4 in the starting systems, while solid ZnFe2O4 CNAs are obtained by adjusting the volume proportion of ethylene glycol to ethanol from 1:2 to 2:1. Magnetometric measurement data showed that the ZnFe2O4 CNAs obtained with the volume ratios of 1:2 and 1:1 exhibited weak ferromagnetic behavior with high saturation magnetization values of 60.4 and 60.3 emu·g−1, respectively. However, hollow spheres showed a saturation magnetization value of 52.0 emu·g−1, but the highest coercivity among all the samples. It was found that hollow spheres displayed the best ability to adsorb Congo red dye among all the CNAs. The formation mechanisms of ZnFe2O4 CNAs, as well as the relationship between their structure, crystallite size, and properties were discussed based on the experimental results. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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Open AccessArticle Immobilization of Magnetic Nanoparticles onto Amine-Modified Nano-Silica Gel for Copper Ions Remediation
Materials 2016, 9(6), 460; doi:10.3390/ma9060460
Received: 26 April 2016 / Revised: 21 May 2016 / Accepted: 2 June 2016 / Published: 9 June 2016
Cited by 2 | PDF Full-text (5674 KB) | HTML Full-text | XML Full-text
Abstract
A novel nano-hybrid was synthesized through immobilization of amine-functionalized silica gel nanoparticles with nanomagnetite via a co-precipitation technique. The parameters, such as reagent concentrations, reaction temperature and time, were optimized to accomplish the nano-silica gel chelating matrix. The most proper amine-modified silica gel
[...] Read more.
A novel nano-hybrid was synthesized through immobilization of amine-functionalized silica gel nanoparticles with nanomagnetite via a co-precipitation technique. The parameters, such as reagent concentrations, reaction temperature and time, were optimized to accomplish the nano-silica gel chelating matrix. The most proper amine-modified silica gel nanoparticles were immobilized with magnetic nanoparticles. The synthesized magnetic amine nano-silica gel (MANSG) was established and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and vibrating sample magnetometry (VSM). The feasibility of MANSG for copper ions’ remediation from wastewater was examined. MANSG achieves a 98% copper decontamination from polluted water within 90 min. Equilibrium sorption of copper ions onto MANSG nanoparticles obeyed the Langmuir equation compared to the Freundlich, Temkin, Elovich and Dubinin-Radushkevich (D-R) equilibrium isotherm models. The pseudo-second-order rate kinetics is appropriate to describe the copper sorption process onto the fabricated MANSG. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
Open AccessArticle Effective Degradation of Aqueous Tetracycline Using a Nano-TiO2/Carbon Electrocatalytic Membrane
Materials 2016, 9(5), 364; doi:10.3390/ma9050364
Received: 10 March 2016 / Revised: 27 April 2016 / Accepted: 10 May 2016 / Published: 12 May 2016
PDF Full-text (3536 KB) | HTML Full-text | XML Full-text
Abstract
In this work, an electrocatalytic membrane was prepared to degrade aqueous tetracycline (TC) using a carbon membrane coated with nano-TiO2 via a sol-gel process. SEM, XRD, EDS, and XPS were used to characterize the composition and structure of the electrocatalytic membrane. The
[...] Read more.
In this work, an electrocatalytic membrane was prepared to degrade aqueous tetracycline (TC) using a carbon membrane coated with nano-TiO2 via a sol-gel process. SEM, XRD, EDS, and XPS were used to characterize the composition and structure of the electrocatalytic membrane. The effect of operating conditions on the removal rate of tetracycline was investigated systematically. The results show that the chemical oxygen demand (COD) removal rate increased with increasing residence time while it decreased with increasing the initial concentration of tetracycline. Moreover, pH had little effect on the removal of tetracycline, and the electrocatalytic membrane could effectively remove tetracycline with initial concentration of 50 mg·L−1 (pH, 3.8–9.6). The 100% tetracycline and 87.8% COD removal rate could be achieved under the following operating conditions: tetracycline concentration of 50 mg·L−1, current density of 1 mA·cm−2, temperature of 25 °C, and residence time of 4.4 min. This study provides a new and feasible method for removing antibiotics in water with the synergistic effect of electrocatalytic oxidation and membrane separation. It is evident that there will be a broad market for the application of electrocatalytic membrane in the field of antibiotic wastewater treatment. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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