Understanding and enhancing multi-pollutant control using carbon-based materials

Activated Carbon;Catalysis;Adsorption;NO Oxidation;Trace Contaminant Control;Ultrasonic Spray Pyrolysis

Atkinson, John

关键词: Activated Carbon;    Catalysis;    Adsorption;    NO Oxidation;    Trace Contaminant Control;    Ultrasonic Spray Pyrolysis;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/44469/John_Atkinson.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Decades of research and industrial use have solidified carbon as one of the most versatile materials available.In the environmental arena, carbon is used as an adsorbent for air and water applications.Recent studies, however, highlight its use as a catalyst support or direct catalyst. Exploiting this versatility may allow carbon to function simultaneously as a catalyst, adsorbent, and/or catalyst support, making carbon an ideal candidate for multi-pollutant control applications.A single, simple, and possibly regenerable control device that can be used to prevent the emissions of several harmful contaminants would revolutionize the fields of air or water pollution control, helping to directly improve public health and protect the environment.In the studies completed herein, the versatility of carbon, in terms of preparation and potential applications, was investigated.Catalytic carbons were prepared via ultrasonic spray pyrolysis and potential applications for these materials were proposed.Next, activated carbons were tested as catalysts for NO oxidation and adsorbents for toxic industrial chemicals, including HCN.The research culminates by investigating the potential for carbon to be used to simultaneously control NO and mercury (Hg) or polychlorinated dibenzo-p-dioxins and -furans (PCDD/F), taking advantage of carbon’s adsorptive and catalytic properties.A simple, one-step technique based on ultrasonic spray pyrolysis was developed to prepare potentially catalytic carbons in a simpler and potentially more sustainable process.This one-step technique minimizes the number of heating steps and manual effort compared to the traditional methods for preparing iron-impregnated porous carbon materials.Work was done not only to investigate the role of processing parameters on the physical and chemical properties of the resulting materials, but also to investigate potential environmental applications for these impregnated carbons.Proposed applications include liquid phase reduction of chromium VI or gas phase heterogeneous catalysis.To expand the application potential of the USP technique, one-step preparation and impregnation of porous carbons with copper, zinc, cobalt, and nickel – all of which have been described as meaningful environmental catalysts in the literature – were also described.Activated carbon fiber cloth was investigated as a catalyst for the oxidation of NO to NO2 in the presence of oxygen.This work specifically shows the continuous addition of oxygen to the surface of the activated carbon catalysts through the use of NO oxidation cycle experiments.These oxygen groups acidify the carbon catalyst, which decreases the time required to achieve steady-state conditions.Furthermore, it is shown that changes to the surface chemistry of the carbon during NO oxidation have little impact on the physical properties of the catalyst, allowing the carbon to maintain its steady-state conversion efficiency during subsequent reaction cycles.This work highlights the preferred properties of NO oxidation carbon catalysts, allowing them to be prepared directly in the laboratory and function at peak performance immediately.The physical, chemical, and adsorptive properties of a commercially available activated carbon nanofiber (ACnF) were quantified and described.Chemical characterizations indicate that this novel carbon material contains significant amounts of surface nitrogen groups, adding basicity to the material.Physical analyses, however, show a completely microporous structure that includes extremely narrow micropores.Adsorption testing indicates that this material can be an effective adsorbent for acidic or acid producing gases, including HCN and SO2.The small diameters of the individual nanofibers and the narrow micropores within the fibers allow the ACnF to have improved adsorption kinetics compared to commercially available activated carbon fibers and carbon granules.Having gained a thorough background for the catalytic and adsorptive properties of activated carbons, select materials were tested for their ability to simultaneously control high concentration NO (through catalytic oxidation to NO2) and low concentration trace contaminants, including Hg and PCDD/F.Preliminary data describes the ability of carbons to individually control Hg (through physical and/or chemical adsorption) and PCDD/F (through physical adsorption and destruction).Subsequent testing highlights carbon’s ability to simultaneously oxidize NO to NO2 while controlling the release of these trace contaminants.This research is intended to support and springboard additional multi-pollutant control studies for novel activated carbons.