Tuning Pore Structure Research Articles

In-line granular filtration for mitigating gypsum scaling in membrane distillation

Mineral scaling and scaling-induced wetting are major challenges for the widespread application of membrane distillation (MD) in saline wastewater treatment. For the first time, an in-line modified activated alumina (AA) granular filtration coupled with MD process was proposed to achieve effective control of gypsum scaling. Firstly, the AA modified by NaOH impregnation with tuned pore structure and surface characteristics were supplied as the filter media. The optimized MD performance was obtained using in-line filtration with modified AA (MAA) with 20 g/L NaOH and the ratio of AA and NaOH solution of 1:3 for the duration of 24 h. Compared with severe scaling without granular filter, the optimized performance with a final normalized flux higher than 0.7 and a permeate conductivity less than 5 μS/cm at 70 % water recovery was observed. The MAA with rich pore, scale-like structures and high Na loading showed a superior ability in capturing gypsum scaling due to the enhanced heterogeneous scaling and the retention of scaling. In-line granular filtration-MD was also effective in mitigating gypsum scaling and scaling-induced wetting in saline solutions (e.g., 7–12 g/L NaCl). Our findings provide guidance for surface design of granular filter media and scaling control in membrane desalination technology.

Hierarchically porous ZSM-5/SBA-15 composite: Tuning pore structure and acidity for hydrodesulfurization of dibenzothiophene

Series ZSM-5/SBA-15 (ZS15-x) composites with different pore structure and acidity were synthesized, and the corresponding NiMo/ZS15-x catalysts were prepared for dibenzothiophene (DBT) hydrodesulfurization (HDS). The controlled introduction of ZSM-5 nanocrystal imparts more acid sites to the NiMo/ZS15 catalyst without altering its fundamental morphology. Furthermore, the increased presence of acid sites enhances the HDS effect of NiMo/ZS15-x catalysts. Simultaneously, the introduction of ZSM-5 nanocrystal modulates the interactions between metal and support (MSI), thereby promoting the dispersion of the active sites. The optimized NiMo/ZS15-50 exhibited superior HDS activities of 98.9 % for DBT, with the optimal reaction rate constant of 3.0 × 10−7 mol/g s−1 and turnover frequency of 2.0 × 10−4 s−1. This can be attributed to its two-dimensional open channels, suitable acidic sites and highly dispersed MoS2. The increased proportion of the ZSM-5 framework and enhanced acidity are advantageous for DBT HDS.

ZSM-5/γ-Al2O3 Catalysts for Methanol Dehydration: Tuning Pore Structure by Carbon Nanotubes as a Pore-Forming Agent

ZSM-5/γ-Al2O3 composites are synthesized using multiwall carbon nanotubes as a pore-forming agent. The as-prepared composites are characterized by nitrogen adsorption, X-ray diffraction, X-ray fluorescence, TEM, SEM, FT-IR spectroscopy, and pyridine adsorption. The as-prepared composites exhibit significantly different physicochemical properties depending on the synthesis technique. The catalytic activity of the as-prepared composites toward methanol dehydration to dimethyl ether is investigated. The as-prepared composites demonstrate the methanol conversion close to the equilibrium one with 100% selectivity toward dimethyl ether. The kinetic parameters of the process are measured highlighting the effect of the textural and acidic properties of the composites on their catalytic performance.

Tuning pore structure of polymer-derived carbon materials for supercapacitor electrode materials using microscopic phase separation engineering

Specific surface area and pore structure have critical impact on the performance of carbon-based supercapacitors. However, for carbon materials, the association between pore architecture and electrochemical performance remains unclear. In this study, sub-nano porous carbon materials with precisely controllable pore size were fabricated by a simple direct carbonization method using interpenetrating polymer networks (IPN), Besides, the correlation between pore architecture and electrochemical performance was explored by controlling the relative content of the two polymer phases to enhance or weaken the degree of microscopic phase separation so as to modulate the pore structure. C-IPN1 exhibited the highest Specific Surface Area (SSA) at 827 m2 g−1, where micropores contributed 95.8 % for the total SSA. Within the three-electrode device, C-IPN1 provided an excellent Specific Capacitance of 238.5 F g−1 at the current density of 0.5 A g−1, which had high cycle stability (100 % capacity retention for 10,000 cycles) and achieved 79.5 % capacitance retention for 20-fold increase in current density (0.5 A g-1 to 10 A g−1). Furthermore, assembled symmetrical supercapacitors achieved an energy density of 7.31 Wh Kg−1 at the power density of 62.5 W Kg−1. This could provide a new avenue for the development of high-performance carbon electrode materials for double layer capacitors, given its simple synthesis process and excellent performance.

Tuning pore structure and specific surface area of graphene frameworks via one-step fast pyrolysis strategy: Impact on electrochemical sensing behavior of catechol

Rational design porous nanomaterials with high specific surface area (SSA) have become an effective approach to improve their electrocatalytic activity, and thus enhancing the electrochemical sensing performance. However, increasing of SSA generally accompanied by magnifying the background current signal, which results in the electrochemical sensors may not achieve the optimal sensing performance. For porous nanomaterials, not only the appropriate SSA but also the pore size probably impacts the electrochemical sensing performance, while this aspect has seldomly studied in electrochemical sensor. Herein, the different SSA and pore size of graphene frameworks (GFs) are successfully synthesized by adjusting the ratio of the mixture of glucose and Na2CO3 via one-step fast pyrolysis process. The tailored GFs has been used as electrode material for constructing non-enzymic electrochemical sensor with catechol (CC) used as model analyte. Electrochemical analysis result suggests that GFs with the highest SSA do not obtain the best behavior, while GFs with abundant hierarchical pore structure and relatively large SSA can achieve the best performance. The optimized GFs as electrode materials for electrochemical detection of CC exhibit a low detection limit of 0.19 μM, and a relatively wide linear range between 1 and 201 μM. This work provides a guide for developing new porous carbon materials for electrochemical sensor with better performance.

Tuning pore structure of aluminosilicate for optimizing thermal energy storage property

Tuning the pore structure of scaffold materials is an effective avenue to preclude the leakage issue of phase change materials (PCMs) and optimize the thermal energy storage capacity of composites for practical applications. Herein, we precisely tuned the pore configuration of nano-aluminosilicate aggerates (n-ASA) by desilication-rearrangement mechanism to systematically investigate the influence of pore size on the energy-storage performance of polyethylene glycol (PEG)-based composites. n-ASA scaffolds with the mean pore size from 11.2 to 27.0, 51.7 and 111.0 nm were synthesized respectively, and the corresponding PCM composites n-ASA*n@PEG were prepared successfully. Among them, n-ASA*1@PEG exhibited the highest heat storage performance on account of the moderate pore size of 27.0 nm and the highest pore volume in all the prepared scaffolds. The load of PEG in the composite reached 81.0 wt%, and the corresponding melting and solidifying enthalpies were 139.8 J/g and 123.8 J/g, respectively. Furthermore, the mechanism of desilication-rearrangement is ideally suited for tailoring the pore size of silica matrixes, and the modulation of pore characteristics would be a feasible protocol to construct efficient energy-storage systems.

Ultrahigh-surface-area activated biocarbon based on biomass residue as a supercapacitor electrode material: Tuning pore structure using alkalis with different atom sizes

This work aims to develop an electrode material based on activated biocarbon made from rubber wood sawdust waste using alkali activating agents – KOH, NaOH, and LiOH – via a solvent-free mechanical mixing. The role of different alkali metal atom sizes plays in resulting pore structure has been studied for the first time. The influence of standard reduction potentials on the pore structure and electrochemical performance of the activated biocarbon are also investigated. The biocarbons activated with KOH or NaOH exhibit a microporous characteristic and a wide range of specific surface area of 1323–3040 m2/g, while the one activated with LiOH exhibits a mesoporous nature. The comparatively small atom size of Li and its low standard reduction potential may have caused the slow reactivity of LiOH with carbon matrix. This leads to the low specific surface area of 1134 m2/g and the formation of tiny lithium particles that could intercalate into biocarbon structure more readily than potassium or sodium particles. Mesoporosity tends to be generated by using alkali activating agent with small metal atom size and low standard reduction potential, whereas microporosity has an opposite trend. Cyclic voltammetry curves and charge-discharge profiles confirm the dominant EDLC behavior along with partial pseudocapacitance for activated biocarbons. The maximum specific capacitance is 195.3 F/g at 0.25 A/g for biocarbon activated with KOH at 4:1. This value is reduced to 69.4% of its original values at 4 A/g. The biocarbons activated with LiOH or NaOH retain the rate capability by 82.9% and 80.4%, respectively.

Pre-pyrolysis metal and base addition catalyzes pore development and improves organic micropollutant adsorption to pine biochar

Biochars were produced from pine feedstock pretreated with aqueous base, NaOH, at pH 9 and 11, and alkali and alkaline earth metals (AAEMs) Na, K, Ca, and Mg at 10−3 and 1 M. The effects of base and AAEM feedstock pretreatment on biochar surface area, pore size distribution, and adsorption capacity of two organic micropollutants (OMPs), 2,4-dichlorophenoxyacetic acid and sulfamethoxazole, from surface water with background dissolved organic matter (DOM) were evaluated. Base pretreatment significantly increased surface area within micropores (<2 nm diameter). AAEM pretreatment caused pore widening, increasing surface area within pores >2 nm in diameter. The catalytic activity of AAEMs, assessed by generation of non-micropore surface area, decreased in the following order: Ca > K > Na > Mg. All pretreated biochars outperformed untreated biochar for OMP adsorption. Biochar pretreated by aqueous base at pH 11 showed over an order of magnitude increase in OMP adsorption, nearly matching the performance of commercial activated carbon. OMP adsorption from surface water was positively correlated with biochar micropore surface area and negatively correlated with non-micropore surface area, which was linked to higher levels of DOM competition. Base and AAEM pretreatment of biochar feedstocks can increase OMP adsorption for water treatment applications by tuning pore structure and surface area.

Controllable nanoporous copper synthesized by dealloying metallic glasses: New insights into the tuning pore structure and applications

It is a great challenge to explore a feasible inner factor that dominates the ligament/pore size of nanoporous metals (NPMs). Herein, the controllable nanoporous copper (NPC) ribbons synthesized by free-dealloying as-spun Cu50-xZr50Mx (x = 0 and 2.5 at.%; M = Al, Nb, Ag) metallic glasses (MGs). From insightfully understanding the correlation of the ligament sizes of NPC, the surface diffusivity of Cu atoms as well as the corrosion potential of additional elements (Al, Nb, Ag), it is firstly unveiled that the corrosion potential of additional elements in the examined etching media could be an inner factor for influencing the pore/ligament size of NPMs. The new findings rooting in the inherent nature of additional elements makes the design of NPMs with useful pore size much more feasible than ever. For further application of NPC with tunable ligament size, the suitable pore structure of NPC is effective in improving the dispersion of MnO2 nanoflakes or nanoflowers to form 3D porous MnO2@NPC composite electrodes. Density functional theory (DFT) further proves that the interaction of NPC and MnO2 results in the modification of the electronic structure and subsequently the improvement of the electrochemical performance. The NPC-supported MnO2 electrode presents much enhanced specific capacitance and cycling stability as compared to the MnO2 nanoparticles. At last, three symmetric supercapacitor (SC) devices connected in series could power up a green LED bulb for more than 55 min.

Fabrication porous adsorbents templated from modified sepiolite-stabilized aqueous foams for high-efficient removal of cationic dyes

High internal phase emulsions (HIPEs) as template for fabrication of porous materials has attracted much attention, due to the high porosity and tunable porous structure. But the enormous consumption of organic solvents is still a nightmare for the practical application. In comparison, the aqueous foam without need any organic solvent and hence has greater advantages in the porous materials preparation. In this study, a novel Pickering foam which was stabilized by modified sepiolite (Sep) was prepared and applied as the template for preparation of the porous material via thermal-initiated polymerization. The Pickering foam had excellent ability and stability in the pH of 4–11 and the obtained porous adsorbent possess sufficient and tuned pore structure. The porous materials as adsorbent has favorable performance for adsorption and selective removal of cationic dyes, and the understanding adsorption capacities for Methylene blue (MB) and Methyl green (MG) can be achieved with 1421.18 mg/g and 638.81 mg/g within 60 and 45 min at 25 °C, respectively. This porous material can be as the potential adsorbent for adsorption or separation of organic pollutants.

Effect of the Post‐Treatment of HZSM‐5 on Catalytic Performance for Methanol to Aromatics

AbstractThe preparation of aromatic by methanol was the most effective way for rational utilization of resources. However, the catalyst for MTA reaction has not yet been successfully studied. Therefore, highly active and shape‐selective HZSM‐5 zeolite‐based catalysts were designed and synthesized by post‐treatments of desilication, dealumination, surface‐passivation and hydrothermal treatment tuning pore structure and acid amount and acid concentration of catalysts. XRD, SEM, TEM, BET, NH3‐TPD and Py‐IR were used for research and analysis the structure‐activity relationship between the catalysts and MTA reaction. The results showed that the total acid amount of catalyst shown a significant role in increasing the BTX selectivity. The selectivity of aromatics increased from 33 % to 58.1 % after hydrothermal treatment compared to the parent HZSM‐5 zeolite due to the decreased of total acid amount. Nevertheless the weak acid sites were crucial in increasing the p‐xylene selectivity. The selectivity of p‐xylene reached 63.8 % and 70.1 % after hydrothermal treatment and surface‐passivation due to the increased of weak acid sites, respectively. Modified HZSM‐5 zeolite‐base catalysts showed good application prospects in producing aromatics from methanol.

Hierarchically Porous β/SBA-16 Composites: Tuning Pore Structure and Acidity for Enhanced Isomerization Performance in Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene

β/SBA-16 (BS) materials were fabricated using β-nanoclusters through self-assembly hydrothermal crystallization approach; subsequently, the corresponding NiMo/BS catalysts were synthesized. The inf...

Biomass derived N-doped biochar as efficient catalyst supports for CO2 methanation

N-doped biochar with a high nitrogen content and tuned pore structure was obtained from Pinus sylvestris by an in-situ pyrolysis process with simultaneous doping nitrogen and activation where urea was used as a nitrogen precursor and NaHCO3 was employed as the activator. To test the feasibility of N-doped biochars obtained under different pyrolysis temperatures as catalyst supports, a series of Ru catalysts were prepared for use in the methanation and the catalysts were labelled as Ru/N-ABC-x, where x represented the pretreatment temperatures(500, 600 and 700 °C). Besides, the catalytic test of Ru/ABC which was prepared under the same conditions without N modification was also conducted for comparison. The probe reaction test of CO2 methanation showed that the Ru/N-ABC-600 catalyst with the highest pyridinic-N (37.7%) content had superior or comparable catalytic performance to Ru/N-ABC-500 and Ru/N-ABC-700 prepared from N-doped biochar with different pyridinic-N content. A high CO2 conversion of 93.8% with a CH4 selectivity of 99.7% was achieved on Ru/N-ABC-600 under the optimum reaction conditions (380 °C, 1 MPa, n(H2)/n(CO2) of 4, with a gas hourly space velocity of 6000 mL·g-1·h-1). This work provides an effective strategy for the utilization of biochar to develop highly active catalysts for CO2 methanation.

Tuning the pore structure of porous tin foam electrodes for enhanced electrochemical reduction of carbon dioxide to formate

Tin-based catalysts have been regarded as a promising candidate for electrochemical reduction of CO2 to produce value-added chemicals and reduce CO2 emissions. However, the catalysts still suffer from unsatisfied performance like large overpotential, rapid deactivation, and lower stability. In this work, the tunable pore structure of porous Sn foam electrodes were prepared using a simple acetic acid (bubble stabilizer)-assisted hydrogen bubble dynamic template method and evaluated as electrocatalysts for CO2 reduction. The Sn-0.15 (bubble stabilizer concentration of 0.15 M in precursor electrolyte), characterized by pore diameter of 50–60 µm and 3.2 times higher of pore number on surface layer of electrode, exhibited an excellent activity towards CO2-to-formate conversion with high Faradaic efficiency in a wide potential from −1.2 to −1.8 V, and acquired the maximum of 95.6% at −1.6 V vs. Ag/AgCl. With this porous electrode, formate started to produce at overpotentials as low as 473 mV and showed negligible degradation over electrolysis for 55 h. Electrochemical tests indicated the notable activity was attributed to the coordinative effect of enlarged reaction sites, weakened interaction strength of CO2− on the low-coordination sites, and alleviated reactant transfer resistance at reaction interfaces. These results demonstrate that tuning pore structure of tin catalyst is a convenient and promising approach for efficient CO2 electroreduction.

Microspheres with Tunable Porosity Based on Reactive Block Copolymer: Preparation and Vapor‐Healing Behavior

AbstractHerein, a simple route to prepare porous microspheres with tuned pore structure and potential functionality based on epoxy functionalized block copolymers, poly hydroxypropyl methacrylate‐b‐ poly glycidyl methacrylate (PHPMA‐b‐PGMA), through a water‐in‐oil‐in‐water (W/O/W) double emulsion is reported. The effect of surfactant concentration and the composition of block copolymers are investigated. The solvent vapor swelling behavior of porous microspheres before and after cross‐linking is studied. It is interesting that after the swelling, the cross‐linked open pores are self‐healed to form closed pores, whereas the uncross‐linked ones are collapsed. It is believed that this observation will be useful in guest carrying and control release, and find its application in biomedical and pharmaceuticals.

Hierarchically Porous ZSM-5/SBA-15 Zeolite: Tuning Pore Structure and Acidity for Enhanced Hydro-Upgrading of FCC Gasoline

The pore structure and acid sites of the catalysts are demonstrated as the main factors for the hydro-upgrading of fluid catalytic cracking (FCC) gasoline. Herein, we report a general synthesis of ZSM-5/SBA-15 composite zeolites with tunable pore structure and acid sites. The effects of the pore structure and acid sites of these catalysts on their hydro-upgrading performance were systematically investigated. The platelet CoMo/AZS-PL (CoMo/ZS-PL-γ-Al2O3) catalyst with the short mesochannels, appropriate Co–Mo–S phase, and suitable acidity exhibited the excellent preservation ability of research octane number (RON) and hydrodesulfurization (HDS) performance, which was better than those of CoMo/AZS-SR (CoMo/ZS-SR-γ-Al2O3), CoMo/AZS-HP (CoMo/ZS-HP-γ-Al2O3), and CoMo/AZS-LR (CoMo/ZS-LR-γ-Al2O3) catalysts. The relationship between the physicochemical properties (acidity, morphology, pore structure, and sulfided active metal) of the catalysts and their isomerization (ISO), aromatization (ARO), as well as HDS abi...

Facile fabrication of MIL-96 as coating fiber for solid-phase microextraction of trihalomethanes and halonitromethanes in water samples

Trihalomethanes (THMs) and halonitromethanes are the two most dominant categories of volatile disinfection by-products that pose considerable public health concerns. The pretreatment and determination methods of THMs in low concentrations, particularly trichloronitromethane (TCNM), have always been the focus of researchers. Metal-organic frameworks, which are effective adsorbents, have considerable potential for solid-phase microextraction (SPME) because of their tuned pore structure, large surface area, and high thermal and chemical stabilities. In this study, MIL-96 was successfully fabricated and developed as a coating fiber for SPME of THMs and TCNM in water samples. Several extraction parameters (i.e., extraction temperature, extraction time, stirring rate, pH, and ionic strength) and desorption parameters (i.e., temperature and time) were investigated and optimized in detail. Ionic strength, extraction temperature, and pH/desorption temperature were identified as key factors that affected the SPME efficiencies of THMs and TCNM. The developed method under optimal conditions obtained wide linearity (0.02–50 µg/L), low limits of detection (0.0030–0.0110 µg/L), and high enrichment factors (81–1181) for detecting THMs and TCNM. The spiked recoveries (1 and 10 µg/L) and relative standard deviations ranged from 81.0% to 109.9% and from 3.92% to 10.10%. Notably, the developed SPME method could overcome thermal degradation and showed excellent performance for TCNM. These results indicated the applicability of MIL-96 as coating fiber.

Engineered Fabrication of Hierarchical Frameworks with Tuned Pore Structure and N,O-Co-Doping for High-Performance Supercapacitors.

A series of multiheteroatom porous carbon frameworks (MPCFs) is prepared successfully from the trimerization of cyano groups of our designed and synthesized 4,4'-(4-oxophthalazine-1,3(4H)-diyl)dibenzonitrile monomers and subsequent ionothermal synthesis. Benefiting from the molecular engineering strategy, the obtained MPCFs framework show a homogeneous distribution of nitrogen and oxygen heteroatoms at the atomic level, confirmed by the transmission electron microscopy mapping intuitively, thereby ensuring the stability of electrical properties. The supercapacitor with the obtained MPCFs@700 as the electrode exhibits a high energy density of 65 Wh kg-1 at 0.1 A g-1, with excellent long cycle life and cycle stability (98% capacitance retention for 10 000 cycles in 1-butyl-3-methylimidazolium tetrafluoroborate). Another two electrolyte systems employed also demonstrate the delightful results, showing a 112% capacitance retention for 30 000 cycles in 1 M H2SO4 and a 95% capacitance retention for 30 000 cycles in tetraethylammonium tetrafluoroborate in an acetonitrile solution. Moreover, the successful preparation of MPCFs provides new insights into the fabrication of electrode materials intrinsically containing nitrogen and oxygen in the frameworks for readily available components through a facile routine.

Engineering Porous Poly(lactic acid) Scaffolds with High Mechanical Performance via a Solid State Extrusion/Porogen Leaching Approach.

A knotty issue concerning the poor mechanical properties exists in the porogen leaching approach to porous scaffolds, despite its advantage in tuning pore structure. To address this hurdle, solid state extrusion (SSE) combined with porogen leaching was utilized to engineer porous scaffolds of poly(lactic acid) (PLA). Advances introduced by poly(ethylene glycol) (PEG) caused the PLA ductile to be processed and, on the other hand, enabled the formation of interconnected pores. Thus, a well-interconnected porous architecture with high connectivity exceeding 97% and elevated porosity over 60% was obtained in the as-prepared PLA scaffolds with the composition of NaCl higher than 75.00 wt % and PEG beyond 1.25 wt %. More strikingly, the pore walls of macropores encompassed countless micropores and rough surface topography, in favor of transporting nutrients and metabolites as well as cell attachment. The prominent compressive modulus of the PLA scaffolds was in the range of 85.7–207.4 MPa, matching the normal modulus of human trabecular bone (50–250 MPa). By means of alkaline modification to improve hydrophilicity, biocompatible porous PLA scaffolds exhibited good cell attachment. These results suggest that the SSE/porogen leaching approach provides an eligible clue for fabricating porous scaffolds with high mechanical performance for use as artificial extracellular matrices.

Tuning pore structure of corrosion resistant solid-state-sintered SiC porous ceramics by particle size distribution and phase transformation

Aggressive process environment like hot corrosive water treatment caused corrosion in ceramic membrane and strength degradation of the membrane support, resulting in the invalidation of membrane filtration. Therefore, new SiC membrane support based on its intrinsic corrosion resistance was prepared by the combination of bi-modal particle size distribution and solid-state-sintering with 1–3wt.% of B4C additive at 2150°C and 2200°C. By tuning the contents of coarse and fine powder and without introducing any pore-creating agent, the porosity of SiC supports varied in the range of 36–39%, which was suitable for the membrane filtration. The phase transformation of 6H–SiC to 4H–SiC induced by the addition of B4C at 2200°C, accompanied by the formation of large plate-like grains, caused the pore size increased from 11.8μm to 20.9μm. The corrosion resistance of solid-state-sintered SiC supports was evaluated by exposing in 90°C 20wt.% H2SO4 and NaOH solutions for 200h. The high residual flexural strength (≥92.5%) and unchanged microstructure of the solid-state-sintered SiC supports after corrosion demonstrated that the supports exhibited excellent corrosion resistance and would be promising candidates to substitute the traditional ceramic supports.