{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/24421"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/24421","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Elucidation of nitrate reduction mechanisms on a Pd/In bimetallic catalyst using isotope labeled nitrogen species","abstract":"Catalytic hydrogenation over Pd-based catalysts has emerged as an effective treatment approach for nitrate (NO3-) removal, but its full-scale application for direct treatment of drinking water or ion exchange regenerant brines requires improved selectivity for the end-product dinitrogen (N2) over toxic ammonia species (NH4+, NH3). A key to improving N2 versus NH4+ production is to elucidate nitrate reduction pathways and identify the key intermediate(s) that determine selectivity. To address this challenge, aqueous reduction experiments with an Al2O3-supported Pd/In bimetallic catalyst were conducted using isotope-labeled nitrite (15NO2-), the first reduction intermediate of NO3-, alone and in combination with unlabeled proposed reduction intermediates (N2O, NO), and using N2O and NO alone, each as a starting reactant. Use of 15N-labeled species eliminated interference from ambient 14N2 when assessing mass balances and product distributions. Simultaneous catalytic reduction of 15NO2- and 14N2O showed no isotope mixing in the final N2 product, demonstrating that N2O does not react with other NO2- reduction intermediates. N2O reduction alone also yielded only N2, verifying that N2O reduction occurs after the reaction step controlling final N2/NH4+ product distribution. In contrast, simultaneous catalytic reduction of 15NO2- and 14NO yielded mixed-labeled N2 (mass 29), and 15NO reduction alone yielded both N2 and NH4+, indicating that NO is a key intermediate involved in determining final product selectivity. N2/NH4+ product selectivity was also evaluated as a function of varying initial 15NO concentration, and results show that selectivity for N2 increases with initial NO concentration to a point, above which product selectivity remains unchanged. This trend is attributed to the increasing importance of N-N pairing reactions leading to N2O formation as the concentration of catalyst-adsorbed NO (NOads) increases to a point of saturating available adsorption sites, above which no further increases in N2 selectivity occur. These results are important because they yield mechanistic insights into the NO3- reduction pathway and information on how catalytic reduction processes can be optimized to maximize N2 production over NH4+.","abstract_html":"Catalytic hydrogenation over Pd-based catalysts has emerged as an effective treatment approach for nitrate (NO3-) removal, but its full-scale application for direct treatment of drinking water or ion exchange regenerant brines requires improved selectivity for the end-product dinitrogen (N2) over toxic ammonia species (NH4+, NH3). A key to improving N2 versus NH4+ production is to elucidate nitrate reduction pathways and identify the key intermediate(s) that determine selectivity. To address this challenge, aqueous reduction experiments with an Al2O3-supported Pd/In bimetallic catalyst were conducted using isotope-labeled nitrite (15NO2-), the first reduction intermediate of NO3-, alone and in combination with unlabeled proposed reduction intermediates (N2O, NO), and using N2O and NO alone, each as a starting reactant. Use of 15N-labeled species eliminated interference from ambient 14N2 when assessing mass balances and product distributions. Simultaneous catalytic reduction of 15NO2- and 14N2O showed no isotope mixing in the final N2 product, demonstrating that N2O does not react with other NO2- reduction intermediates. N2O reduction alone also yielded only N2, verifying that N2O reduction occurs after the reaction step controlling final N2/NH4+ product distribution. In contrast, simultaneous catalytic reduction of 15NO2- and 14NO yielded mixed-labeled N2 (mass 29), and 15NO reduction alone yielded both N2 and NH4+, indicating that NO is a key intermediate involved in determining final product selectivity. N2/NH4+ product selectivity was also evaluated as a function of varying initial 15NO concentration, and results show that selectivity for N2 increases with initial NO concentration to a point, above which product selectivity remains unchanged. This trend is attributed to the increasing importance of N-N pairing reactions leading to N2O formation as the concentration of catalyst-adsorbed NO (NOads) increases to a point of saturating available adsorption sites, above which no further increases in N2 selectivity occur. These results are important because they yield mechanistic insights into the NO3- reduction pathway and information on how catalytic reduction processes can be optimized to maximize N2 production over NH4+.","abstract_has_math":false,"creators":["Zhang, Rui"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Environ Engr in Civil Engr","degree_department":null,"school":null,"contributors":["Strathmann, Timothy J.","Werth, Charles J."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-25T14:40:23Z","date_published":"2011-05-25T14:40:23Z","updated_at":"2026-07-22T22:25:23Z","subjects":["catalytic hydrogenation","nitrate","reduction","selectivity","intermediates"],"languages":["en"],"rights":["Copyright 2011 Rui Zhang"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/24421","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Strathmann, Timothy J.","Werth, Charles J."]},{"key":"dc:creator","label":"Author","values":["Zhang, Rui"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-25T14:40:23Z","2013-05-26T10:00:25Z","2011-05"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Environ Engr in Civil Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["catalytic hydrogenation","nitrate","reduction","selectivity","intermediates"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2011 Rui Zhang"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/24421"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Catalytic hydrogenation over Pd-based catalysts has emerged as an effective treatment approach for nitrate (NO3-) removal, but its full-scale application for direct treatment of drinking water or ion exchange regenerant brines requires improved selectivity for the end-product dinitrogen (N2) over toxic ammonia species (NH4+, NH3). A key to improving N2 versus NH4+ production is to elucidate nitrate reduction pathways and identify the key intermediate(s) that determine selectivity. To address this challenge, aqueous reduction experiments with an Al2O3-supported Pd/In bimetallic catalyst were conducted using isotope-labeled nitrite (15NO2-), the first reduction intermediate of NO3-, alone and in combination with unlabeled proposed reduction intermediates (N2O, NO), and using N2O and NO alone, each as a starting reactant. Use of 15N-labeled species eliminated interference from ambient 14N2 when assessing mass balances and product distributions. Simultaneous catalytic reduction of 15NO2- and 14N2O showed no isotope mixing in the final N2 product, demonstrating that N2O does not react with other NO2- reduction intermediates. N2O reduction alone also yielded only N2, verifying that N2O reduction occurs after the reaction step controlling final N2/NH4+ product distribution. In contrast, simultaneous catalytic reduction of 15NO2- and 14NO yielded mixed-labeled N2 (mass 29), and 15NO reduction alone yielded both N2 and NH4+, indicating that NO is a key intermediate involved in determining final product selectivity. N2/NH4+ product selectivity was also evaluated as a function of varying initial 15NO concentration, and results show that selectivity for N2 increases with initial NO concentration to a point, above which product selectivity remains unchanged. This trend is attributed to the increasing importance of N-N pairing reactions leading to N2O formation as the concentration of catalyst-adsorbed NO (NOads) increases to a point of saturating available adsorption sites, above which no further increases in N2 selectivity occur. These results are important because they yield mechanistic insights into the NO3- reduction pathway and information on how catalytic reduction processes can be optimized to maximize N2 production over NH4+.","Item withdrawn by Alexis Thompson (athmpsn1@illinois.edu) on 2011-04-20T21:47:33Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5) Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5)","Made available in DSpace on 2011-05-25T14:40:23Z (GMT). No. of bitstreams: 2 Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5) license.txt: 4059 bytes, checksum: 1bdc58b091c7ae9211206c9d656e4396 (MD5)","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by William Ingram (wingram2@illinois.edu) on 2011-05-25T14:42:11Z Item is restricted until 2013-05-25T14:41:28Z","Item reinstated by Sarah Shreeves (sshreeve@illinois.edu) on 2013-05-26T10:00:25Z Item was in collections: Dissertations and Theses - Civil and Environmental Engineering (ID: 672) University of Illinois Dissertations and Theses (ID: 204) No. of bitstreams: 3 Zhang_Rui.pdf.txt: 61025 bytes, checksum: e9b3a2030f9236bb7bee4d8009102d7d (MD5) Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5) license.txt: 4059 bytes, checksum: 1bdc58b091c7ae9211206c9d656e4396 (MD5)","Item released from any restrictions by Sarah Shreeves (sshreeve@illinois.edu) on 2013-05-26T10:00:25Z"]},{"key":"dc:title","label":"Title","values":["Elucidation of nitrate reduction mechanisms on a Pd/In bimetallic catalyst using isotope labeled nitrogen species"]}]}],"canonical_facts":{"dc:contributor":["Strathmann, Timothy J.","Werth, Charles J."],"dc:creator":["Zhang, Rui"],"dc:date":["2011-05-25T14:40:23Z","2013-05-26T10:00:25Z","2011-05"],"dc:description":["Catalytic hydrogenation over Pd-based catalysts has emerged as an effective treatment approach for nitrate (NO3-) removal, but its full-scale application for direct treatment of drinking water or ion exchange regenerant brines requires improved selectivity for the end-product dinitrogen (N2) over toxic ammonia species (NH4+, NH3). A key to improving N2 versus NH4+ production is to elucidate nitrate reduction pathways and identify the key intermediate(s) that determine selectivity. To address this challenge, aqueous reduction experiments with an Al2O3-supported Pd/In bimetallic catalyst were conducted using isotope-labeled nitrite (15NO2-), the first reduction intermediate of NO3-, alone and in combination with unlabeled proposed reduction intermediates (N2O, NO), and using N2O and NO alone, each as a starting reactant. Use of 15N-labeled species eliminated interference from ambient 14N2 when assessing mass balances and product distributions. Simultaneous catalytic reduction of 15NO2- and 14N2O showed no isotope mixing in the final N2 product, demonstrating that N2O does not react with other NO2- reduction intermediates. N2O reduction alone also yielded only N2, verifying that N2O reduction occurs after the reaction step controlling final N2/NH4+ product distribution. In contrast, simultaneous catalytic reduction of 15NO2- and 14NO yielded mixed-labeled N2 (mass 29), and 15NO reduction alone yielded both N2 and NH4+, indicating that NO is a key intermediate involved in determining final product selectivity. N2/NH4+ product selectivity was also evaluated as a function of varying initial 15NO concentration, and results show that selectivity for N2 increases with initial NO concentration to a point, above which product selectivity remains unchanged. This trend is attributed to the increasing importance of N-N pairing reactions leading to N2O formation as the concentration of catalyst-adsorbed NO (NOads) increases to a point of saturating available adsorption sites, above which no further increases in N2 selectivity occur. These results are important because they yield mechanistic insights into the NO3- reduction pathway and information on how catalytic reduction processes can be optimized to maximize N2 production over NH4+.","Item withdrawn by Alexis Thompson (athmpsn1@illinois.edu) on 2011-04-20T21:47:33Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5) Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5)","Made available in DSpace on 2011-05-25T14:40:23Z (GMT). No. of bitstreams: 2 Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5) license.txt: 4059 bytes, checksum: 1bdc58b091c7ae9211206c9d656e4396 (MD5)","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by William Ingram (wingram2@illinois.edu) on 2011-05-25T14:42:11Z Item is restricted until 2013-05-25T14:41:28Z","Item reinstated by Sarah Shreeves (sshreeve@illinois.edu) on 2013-05-26T10:00:25Z Item was in collections: Dissertations and Theses - Civil and Environmental Engineering (ID: 672) University of Illinois Dissertations and Theses (ID: 204) No. of bitstreams: 3 Zhang_Rui.pdf.txt: 61025 bytes, checksum: e9b3a2030f9236bb7bee4d8009102d7d (MD5) Zhang_Rui.pdf: 280951 bytes, checksum: e3c177a007733fdd1c3167f6a37d74a4 (MD5) license.txt: 4059 bytes, checksum: 1bdc58b091c7ae9211206c9d656e4396 (MD5)","Item released from any restrictions by Sarah Shreeves (sshreeve@illinois.edu) on 2013-05-26T10:00:25Z"],"dc:identifier":["http://hdl.handle.net/2142/24421"],"dc:language":["en"],"dc:rights":["Copyright 2011 Rui Zhang"],"dc:subject":["catalytic hydrogenation","nitrate","reduction","selectivity","intermediates"],"dc:title":["Elucidation of nitrate reduction mechanisms on a Pd/In bimetallic catalyst using isotope labeled nitrogen species"],"thesis:degree_discipline":["Environ Engr in Civil Engr"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:23Z"}