Catalytic oxidation of chlorinated organics over lanthanide perovskites: effects of phosphoric acid etching and water vapor on chlorine desorption behavior

In this article, the underlying effect of phosphoric acid etching and additional water vapor on chlorine desorption behavior over a model catalyst La3Mn2O7 was explored. Acid treatment led to the formation of LaPO4 and enhanced the mobility of lattice oxygen of La3Mn2O7 evidenced by a range of characterization (i.e., X-ray diffraction, temperature-programmed analyses, NH3–IR, etc.). The former introduced thermally stable Brönsted acidic sites that enhanced dichloromethane (DCM) hydrolysis while the latter facilitated desorption of accumulated chlorine at elevated temperatures. The acid-modified catalyst displayed a superior catalytic activity in DCM oxidation compared to the untreated sample, which was ascribed to the abundance of proton donors and Mn­(IV) species. The addition of water vapor to the reaction favored the formation and desorption of HCl and avoided surface chlorination at low temperatures. This resulted in a further reduction in reaction temperature under humid conditions (T90 of 380 °C for the modified catalyst). These results provide an in-depth interpretation of chlorine desorption behavior for DCM oxidation, which should aid the future design of industrial catalysts for the durable catalytic combustion of chlorinated organics

Noticiário

In an attempt to achieve the selective oxidation of NOx, a hybrid catalyst of single-atom-anchored metal organic frameworks (MOF, NH2-UiO-66) and MnO2 was constructed and used in the plasma catalytic process. Isolated Ru sites were successfully implanted into the structure of the MOF by simply stirring the mixed liquor containing both MOF and RuCl3, facilitating plasma discharge, NO/NO2 adsorption, and formation of âOH radicals. A special oxo-bridged Zr4+-O-Ru3+ was constructed to accelerate electron transfer and continuous proceeding of the reaction. Directional migration of generated electrons from MOF to Ru sites was witnessed when MOF was activated by plasma-induced "pseudo-photocatalysis". The total (100%) selective plasma-catalytic oxidation of NOx to NO2- and NO3- was achieved at an SIE of 75.3 J/L. The byproduct O3 was effectively degraded and utilized by MnO2, facilitating the deep oxidation of NOx. The facile realization of single atoms would be an ideal way to produce MOF-based catalysts with desired performance. Efficiently combining plasma with single atom-decorated MOF catalysts can provide additional prospects for the plasma-catalytic system. </p

Enhanced CO2 photocatalytic reduction on alkali-decorated graphitic carbon nitride

In this work, visible-light photocatalytic reduction performance of carbon dioxide (CO) on graphitic carbon nitride (g-CN) was significantly promoted by the decoration of potassium hydroxide (KOH) on g-CN. More importantly, the role of KOH was thoroughly discussed via various characterizations, control experiments and density functional theory (DFT) calculations. It was found that KOH decoration did not result in any significant difference regards to the morphology, elemental states, BET surface area and light adsorption of g-CN except a drastically enhanced CO adsorption capacity. The promotion effect of KOH on g-CN was mainly contributed by the hydroxide ion (OH) functioning as both a hole accepter and a driving force to keep a dynamically stable amount of HCO (probably the major form of CO to be reduced) on the surface of the catalyst. Moreover, the different extents of influence of NaOH and KOH on g-CN were revealed and further explained using computational results. This study supplements current understanding on alkali-promoted photocatalytic processes and provides new insights into the mechanism of CO photocatalytic reduction

Efficient elimination of chlorinated organics on a phosphoric acid modified CeO2 catalyst: a hydrolytic destruction route

The development of efficient technologies to prevent the emission of hazardous chlorinated organics from industrial sources without forming harmful by-products, such as dioxins, is a major challenge in environmental chemistry. Herein, we developed a new hydrolytic destruction route for efficient chlorinated organics elimination and demonstrated that phosphoric acid modified CeO2 (HP-CeO2) can hydrolytically destruct chlorobenzene (CB) without forming polychlorinated congeners under the industry-relevant reaction conditions. The active site and origin of hydrolysis reactivity of HP-CeO2 were probed, which showed the surface phosphate groups can hydrolytically react with CB and water to form phenol and HCl, thus facilitating the chlorine desorption and ensuring a continual O2 activation. Subsequent density functional theory (DFT) calculations revealed a distinctly decreased formation energy of oxygen vacancy nearest (VO-1) and next-nearest (VO-2) to the bonded phosphate groups, which led to a significantly improved oxidizing ability of the catalyst. Significantly, no toxic dioxins were detected from the hydrolysis destruction of CB, which has been frequently cited as a significant challenge to avoid in the conventional oxidation route. This work not only reports an efficient route and corresponding phosphate active site for chlorinated organics elimination, but also illustrates that rational design of reaction route can solve some of the most important challenges in environmental catalysis

Application of Internet of Things Compressed Sensing and Information Interaction Technology in Intelligent Transportation Layout

With the continuous development of economy, the number of motor vehicles has increased sharply, and urban traffic congestion has become more and more frequent. Urban traffic congestion has become one of the important reasons that hinder the continuous development of major cities. In order to better solve the problem of urban traffic congestion, it is more urgent to build urban intelligent transportation system. The technology related to Internet of things is becoming more and more mature, which has become a new idea of collecting traffic information, providing convenience for traffic, and injecting vitality into the study of intelligent transportation layout. The traffic system in the city or the main traffic intersection, through the traffic guidance layout road, provides the traffic instruction for the passenger on the highway network, enables the driver to choose the suitable driving road, can provide the travel guidance service for the driver, adjusts the flow distribution, and improves the traffic condition. This paper describes the research status of intelligent transportation layout and uses the basic theory of compressed sensing and information interaction technology to carry out data fusion and reconstruction algorithm in intelligent transportation. Finally, the application of compressed sensing in intelligent transportation layout is summarized to realize data collection in intelligent transportation network. In this paper, compressed sensing theory is applied to the data acquisition of intelligent transportation network to reduce the amount of data and improve the effective data acquisition. The reconstruction algorithm is used to realize the data reconstruction to ensure the accuracy and stability of signal reconstruction and the accuracy of network transmission information

g-C3N4 based composite photocatalysts for photocatalytic CO2 reduction

Photocatalytically converting CO into valuable energy fuels such as CO, CH, HCOOH and CHOH with photocatlayts and sunlight is a dream technology to realize artificial photosynthesis. The utilization of g-CN for CO photocatalytic reduction deserves a highlight not only for the different reaction routes that may take place on this distinct material, but also because of the great potential of this relatively cheap catalyst. In this article, the recent advances on g-CN-based composites for CO photocatalytic reduction are critically reviewed The review starts with a brief introduction of the key steps for CO photocatalytic reduction as well as the basic properties of g-CN. Then g-CN-based materials for CO adsorption and activation are discussed to provide a better understanding of the important active sites on g-CN for CO adsorption/activation, which are very different from many metal oxide photocatalysts. In the main section, g-CN and three major types of g-CN-based composites that have been studied for CO photoreduction are reviewed. Finally, recommendations on future studies to achieve a higher efficiency in CO photocataltic reduction with g-CN-based materials are given

Recent progress on photo-electrocatalytic reduction of carbon dioxide

Ever-increasing carbon dioxide emission has led to serious greenhouse effect and global warming in recent years. Photo-electrocatalysis is the most significant approach to convert carbon dioxide into hydrocarbon fuels to alleviate the greenhouse effect as well as ensure the global carbon cycling with inexhaustible solar energy resource. There are four typical configurations in the photo-electrocatalytic (PEC) carbon dioxide reduction system, i.e., photocathode coupling with anode cell, photoanode combining with cathode cell, photocathode integrating photoanode cell, and a photovoltaic-photo-electrocatalytic tandem cell. This review briefly summarizes the state-of-the-art progress of above four configurations for photo-electrocatalytic carbon dioxide reduction with a focus on the rational design of the electrode materials to achieve higher efficiency. In addition, the innovative design of the PEC system for efficient carbon dioxide reduction has also been concisely introduced. Finally, the perspectives on the challenges and future development of photo-electrocatalytic carbon dioxide reduction based on the discussed configurations are presented

Laboratory Study on Mercury Release of the Gypsum from the Mercury Coremoval Wet Flue Gas Desulfurization System with Additives

In this study, the mercury release of the gypsum from the mercury coremoval wet flue gas desulfurization (FGD) process with post-thermal treatment or open-stack disposal was investigated experimentally. The results indicated that the aqueous-phase oxidized mercury could be efficiently captured and stored in the solid-phase gypsum by using the additives like NaHS, DTCR, and TMT. However, it could be found that the thermal stability of the mercury species on the resulting gypsum decreased significantly under typical wallboard-manufacturing conditions. Especially, 92.8% of mercury was released from the DTCR-treated sample. The following thermal decomposition tests further confirmed this result. The mercury ions in DTCR-Hg compounds were linked to more sulfur atoms, which were ready to transfer electrons to nearby mercury ions during heat-treatment, resulting in its lower stability. It could be also seen that the thermal stabilities of mercury species decreased with an increasing amount of additives. Moreover, the mercury leaching tests showed that additives addition could lead to an evident increase in the mercury leaching content, and the mercury leaching content increased on the order of Hg-TMT < β-HgS < Hg-DTCR. All these results suggested that more attention should be paid toward the mercury release during the post-treatment and disposal of wet FGD gypsum from the mercury coremoval wet FGD system by using additives

Single-Atom Catalysts in Environmental Engineering: Progress, Outlook and Challenges

Recently, single-atom catalysts (SACs) have attracted wide attention in the field of environmental engineering. Compared with their nanoparticle counterparts, SACs possess high atomic efficiency, unique catalytic activity, and selectivity. This review summarizes recent studies on the environmental remediation applications of SACs in (1) gaseous: volatile organic compounds (VOCs) treatment, NOx reduction, CO2 reduction, and CO oxidation; (2) aqueous: Fenton-like advanced oxidation processes (AOPs), hydrodehalogenation, and nitrate/nitrite reduction. We present the treatment activities and reaction mechanisms of various SACs and propose challenges and future opportunities. We believe that this review will provide constructive inspiration and direction for future SAC research in environmental engineering