To develop a new technology to remediate pollution sites stably and effectively, hydrothermal conversion of polluted soil (model soil) into zeolite P for in situ immobilization of Heavy Metals (HM) was carried out. Zeolite P could be synthesized from soil hydrothermally with a large range of Al/Si ratio (0.33–1.0) in 48 h at 200 °C. With immobilizing heavy metals (Cr, Zn and Cd), the crystallization of Zeolite P (Cr-ZP, Zn-ZP and Cd-ZP) was delayed with the order of Cr >Zn >Cd because the stronger the ligand effect of heavy metals have, the more heavily the nucleation and growth were influenced. During immobilization via zeolitization, a self-adaptive structuring behavior was confirmed by EDAX, BET and Rietveld refinement analyses: zeolite P structured more [AlO 4 ] − to immobilize HM because the flexible 8-member-Ring channels (8 mRs) with higher Al/Si ratio could complex with more HM readily. The encapsulated HM occupied the original Na positions (Na1 and Na2) of zeolite P competitively because of their different cation size, e.g., the smallest Cr 3+ could substitute all Na1 because Na1 is closer to the Framework Oxygen (FO); the largest Cd 2+ , however, substituted Na1 (9%) and Na2 (14%) evenly. The shrunken 8 mRs due to heavy metal immobilization also caused different chemical environments for different heavy metals immobilized because the smaller heavy metal cation could get closer to the framework, and also coordinated with more FO.
Volatile organic compounds (VOCs) emitted from many industrial processes, are harmful to human health and the atmsphere. Several technologies are currently used to eliminate VOCs from the environment. Among them, catalytic oxidation has been recognized as one of the most efficient and promising ways to treatment VOCs. So high performance oxidants play an dominant role in the catalytic oxidation process. In this work, we discussed many researchers’ works about preparation and effect of their catalysts, kinds of mesoporous catalysts for eliminating VOCs were reviewed, the active components of the catalysts are noble and non-noble metal oxides, which loaded in the mesochannels of mesoporous materials including silica, titania and aluminia.
In this study, (3-mercaptopropyl) triethoxysilane (MPTMS)-modified ordered mesoporous silica (OMS) materials were prepared using a post-grifting method, with MPTMS as the organic functionalized reagent. The OMS materials were analyzed by FT-IR spectra, N2 sorption, and small angle X-ray scattering to evaluate their potential for scavenging Cd2+ from water. Moreover, a (3-mercaptopropyl) triethoxysilane-functionalized ordered mesoporous silica modified polyvinylidene fluoride (MPTMS-OMS/PVDF) membrane was synthesized using the solvent phase inversion method to remediate wastewater containing heavy metal ions. The MPTMS-OMS was characterized by a maximum specific surface area of 422 m2/g, high surface hydrophilicity, and high pure water flux. The MPTMS-OMS/PVDF exhibited a dynamic adsorption capacity for Cd2+ in water. At an MPTMS-OMS content of 5 wt%, the Cd2+ removal efficiency was 90%, whereas the pure PVDF showed no Cd2+ adsorption capacity. These results highlight the potential of the MPTMS-OMS/PVDF membrane to eliminate Cd2+ during the decontamination of aqueous streams containing low-concentrations of contaminants.
The electrocatalytic reduction of nitrate, a common contaminant in surface and ground water, to the harmless nitrogen gas is a promising technology that can be potentially energy efficient and environmentally friendly. The bottleneck hindering its large-scale implementation is mainly attributed to the unsatisfactory selectivity toward the final product N2. To solve this challenge, a two-step strategy was applied here, in which the NO3- was first reduced to NH4+ at the cathode, followed with a rapid non-electrochemical oxidation to N2 by the ClO- generated from anodic breakpoint chlorination. Note that the formation of ClO- may be easily controlled and enhanced by the dosage of Cl- ions, the overall nitrate removal efficiency for the above process was determined by its NO3- to NH4+ activity. The high-performance copper-nickel alloys embedded mesoporous carbon electrocatalysts were therefore rationally designed, which exhibited a complete conversion of NO3- in the absence of Cl-, and furthermore, a 100% N2 selectivity with the addition of Cl- . Using density functional theory calculations, it was verified that the incorporation of Ni atoms into Cu interface significantly enhanced the adsorption of *NHOH and *NH2OH intermediates, lowering the barrier of *NOH hydrogenation to *NH3 (NH4+). Besides, the nitrogencontaining ordered mesoporous carbon support not only facilitated the synthesis of uniformly distributed CuNi nanoparticles (ca. 20 nm), but also ensured the sufficient mass and charge transfer, as well as the high durability.
Low-temperature selective catalytic reduction of nitrogen oxides (NOx) with NH3 (NH3-SCR) has been identified as a promising strategy to mitigate the pollution of NOx. The fine control of synergistic effect and the suppression of aggregation of the active component, however, are still the challenge because of the weak interaction between the active component and matrix. In this work, a series of Ce-promoted Mn-based heterogeneous catalysts supported on mesoporous silica (SBA-15) with different Mn contents were prepared by two separated impregnation processes. Low-temperature NH3-SCR activity demonstrates that the Mn content in the catalyst has a great influence on the activity of the NH3-SCR reaction. The 20% MnOx-CeOx/SBA-15 catalyst exhibited the best catalytic performance in a broad temperature window. Moreover, it exhibits enhanced resistance to SO2 and H2O and long-term durability during 72 h reaction. The highly dispersive active phase, the formation of solid solution, the high ratio of Ce3+, and the spatial confinement effect largely contribute to the outstanding activity and durability of the 20% MnOx CeOx/SBA-15 catalyst. Finally, a monolithic catalyst fabricated by the 20% MnOx-CeOx/SBA-15 catalyst powder and cordierite substrate show promising industrial application.
Issues of uniform incorporation of catalytic functional species with controllable sizes, shapes, compositions, and functions into porous carbon scaffolds remain significant challenges toward enriching and boosting performance. Here, we develop a straightforward approach that introduces dicyandiamide as a nitrogen source to chelate with metal species and combines with the surfactant-templating self-assembly method for the fabrication of highly dispersed catalysts anchored in nitrogen-containing ordered mesoporous carbon (NOMC). As a result, these functional catalyst (such as PdCu nanocrystals)-embedded NOMC composites manifest a synergistic catalytic capability for the electroreduction of nitrate in neutral electrolyte, with more than 90% nitrate removed under an ultra-low concentration of 100 ppm and a high nitrogen selectivity of 60% after 10 repeated tests.
A subtle catalyst design is provided with stably incorporated binary catalytically active centers of CuO and MnO2 on the surface wall of mesoporous TiO2. Such unique features render these mesoporous composites highly promising in the low-temperature selective catalytic reduction of NO with NH3, including high NO conversion efficiency, and superior H2O and SO2 resistance.
Phthalate esters (PAEs) are a group of endocrine disrupting compounds, which have been widely used as plasticizers. To alleviate the environmental and health threats from water resources polluted by PAEs, we prepared phenyl functionalized mesoporous silica materials (ph-SBA-15) were synthesized by a simple post-modification approach for rapid and efficient removal of low concentration of di-n-butyl phthalate (DBP) from aqueous solution. Mesostructure, texture, surface chemistry and surface charges were systemically characterized. The obtained ph-SBA-15 possesses a highly ordered mesostructure, a high surface area (418m2/g), uniform mesopores (6.5nm) and high-density organic groups around 11wt.%. Batch adsorption experiments revealed that phenyl modified SBA-15 had an excellent ability to remove DBP with the maximum adsorption capacity up to ∼40mg/g at 25°C. The thermodynamics and kinetics for the adsorption were also investigated, demonstrating an exothermic, multi-layer and fast adsorption process. In addition, DBP adsorption was found to be sensitive to the pH and the uptake was observed to be greatest at around pH 7.0. Furthermore, this material can be effectively regenerated by ethanol.
Volatile organic compounds (VOCs) are the primary poisonous emissions into the atmosphere in natural gas exploitation and disposing process. The adsorption method has been widely applied in actual production because of its good features such as low cost, low energy consumption, flexible devices needed, etc. The commonly used adsorbents like activated carbon, silicon molecular sieves and so on are not only susceptible to plugging or spontaneous combustion but difficult to be recycled. In view of this, a new adsorbent (CrSBA15) was made by the co-assembly method to synthesize the ordered mesoporous silica materials with different amounts of chromium to eliminate VOCs. This new adsorbent was characterized by small-angle-X-ray scattering (SAXS), nitrogen adsorption/desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Its adsorption performance to eliminate VOCs (toluene, benzene, cyclohexane and ethyl acetate used as typical pollutants) was also tested systematically. Research results indicate that this new adsorbent of CrSBA-15(30), with the silicon/chromium ration being 30, owns the maximum micropore volume, and shows a higher adsorption performance in eliminating toluene, benzene, cyclohexane and ethyl acetate. Besides, it is cost-effective and much easier to be recycled than the activated carbon. In conclusion, CrSBA-15(30) is a good adsorbent to eliminate VOCs with broad application prospects.
A mesoporous carbon confined PdCu bimetallic electrocatalyst is fabricated, which delivers a superior nitrate conversion yield and nitrogen selectivity.
随着我国经济的持续快速增长, 人类对能源的需求和消耗也随之大幅度增加,同时,化石燃料燃烧带来的环境污染问题日益恶化.煤炭是我国主要能源,约占一次能源总消耗量的70%左右,其中80%以上用于直接燃烧[1],在经济增长模式还未得到彻底改变的大环境下,我国仍然保持以矿产资源(煤、天然气)为主的能源结构[2]. 随着环境污染与经济增长矛盾的日益加剧以及人们环保意识的提高, 同时为了适应可持续发展战略的要求,由燃煤所带来的诸多环境问题亟待解决.
A gradient pyrolysis approach has been adopted for synthesis of ordered mesoporous carbonaceous materials with different surface and textural properties for removal of hexachlorobenzene. The resultant ordered mesoporous carbonaceous materials possess high surface areas (364-888 m2/g), large pore volumes (0.23-0.47 cm3/g), uniform pore sizes (2.6-3.8 nm), and tunable hydrophobic properties. They show high-efficiency removal performances for hexachlorobenzene with high adsorption capacity of 594.2-992.1 μg/g. An enhanced removal rate (>99%) can be obtained with the increasing pyrolysis temperature (900 °C) as a result of the strong hydrophobic-hydrophobic interaction between the carbon framework and hexachlorobenzene molecules. Furthermore, the adsorption behaviors follow the Sips isotherm model and obey the pseudo-first-order kinetic model.
煤层气发电是煤层气利用的重要途径之一,但煤层气发电排放的高温尾气中含有大量的氮氧化物(NOx),会对环境造成污染,需要对其进行脱硝处理,而高温烟气(约500℃)又不宜用V2O5/TiO2蜂窝式催化剂进行直接脱硝处理.为此,在分析比较煤层气发电高温烟气与燃煤发电烟气差别的基础上,应用纳米组装和灌注法研制了GJ-HC-5型催化剂,并通过室内实验确定了脱除NOx的最佳温度窗口(400~600℃).之后,在某煤层气电厂进行中间试验,将发电机组高温烟气直接通入到SCR一体化装置进行脱硝处理,在SCR反应器进出口处连续监测,进口NOx浓度约为620 mg/m3,出口监测浓度约为20mg/m3,对烟气中的NOx的脱除率始终保持在90%以上.试验结果表明,所研制的高温SCR催化剂符合实际烟气温度条件,且制备方法简单,是一种可行的煤层气发电高温烟气的脱硝方法.
A simple two-step method was adopted to prepare the mesoporous Cu–Mn/TiO2 composite, which shows high catalytic activity for the degradation of Acid Red 1.
Highly branched SnO2-decorated TiO2 interpenetrating network architectures were fabricated with superior denitration catalytic activity over a broad temperature range.
ABSTRACT: The deposit of noble metal on titanium dioxide (TiO 2 ) has been considered as an effective strategy to improve the activity of TiO 2 . In this study, TiO 2 nanoparticles were prepared using a sol‐gel route followed by heat treatment at elevated temperatures (573 K, 773 K, and 973 K). TiO 2 ‐Pt catalyst (1 wt%) was prepared by depositing Pt on the surface of the prepared TiO 2 nanoparticles. TiO 2 and TiO 2 ‐Pt were used as heterogeneous catalysts to remove humic acid with UV‐light (120 W) illumination. TiO 2 prepared at low temperature with smaller particle size and larger specific surface area had stronger activity on humic acid degradation. Deposit of Pt would favor separation of photogenerated charges and enhance the photocatalyst activity, but its coating of the active site also inhibited degradation of humic acid. The addition of H 2 O 2 enhanced degradation of humic acid for more active oxygen produced. Low pH (pH = 4) was helpful to adsorb humic acid on the surface of TiO 2 and, correspondingly, enhance degradation of humic acid (44.4%).
Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. Accepted Manuscript Journal of Materials Chemistry A