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Towards Abatement of Selected Emissions from Metals Manufacturing
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science. (S. Seetharaman and M. Göthelid)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although the metallurgical industry has made great strides in the reduction of unwanted emissions to the atmosphere as a result of production processes, significant challenges still exist. From a global perspective, even large reductions in emissions per produced ton become immaterial when considering that the total world production of metals continues to increase. Two such particularly hazardous emissions are sulfur dioxide, primarily from copper ore roasting, and mercury, which has had increasing emissions from the steel industry in recent years. Both pollutants have severe consequences for the environment and also for human health. The primary motivations of this work have hence been: (1). to study sulfate formation on soot from sulfur dioxide emissions reacting with ozone and H2O in the vapor phase and (2). to study factors involving the behavior of mercury adsorption on metal surfaces involved in steelmaking, in order to further the understanding of select emissions from scrap-based steelmaking.

Gas phase experiments were conducted to examine the heterogeneous oxidation of sulfur dioxide on soot in the presence of ozone and water vapor. The sulfur dioxide oxidation into sulfate was quantified using a particle-into-liquid sampler coupled with ion chromatography to measure the sulfate formation at atmospheric pressure. Water vapor, ozone and sulfur dioxide concentrations were controlled.

Due to the ozone oxidation, multilayer adsorption of sulfur dioxide on soot, as well as sulfate formation and physisorption on secondary surface layer sites were observed. The exposure also caused the soot to become hydrophilic, due to the sulfur dioxide adsorption and also likely the formation of carboxyl groups on the surface. No significant increase in sulfate formation was observed at ozone concentrations above 1000 ppm.

The effects of common surface contaminants such as oxygen and chlorine were examined on the metal surfaces, as well as the impact of changes in temperature, with controlled conditions using thermal desorption auger electron spectroscopy. It was established that low temperatures (82 K through 111 K) were conducive to mercury adsorption, wherein physisorption and subsequent lateral mercury interactions in mercury adlayers occurred. Chlorine appeared to favor mercury uptake, as determined by the increased mercury coverage at low temperatures on polycrystalline iron, copper and zinc. Oxygen, however, was found to be an inhibitor of mercury, most notably at room temperature.

It was surprising to establish that no mercury adsorbed on zinc surfaces at room temperature and only on polycrystalline samples at low temperature. The mercury signal intensity increased up to the limit of the melting temperature for iron systems, on the oxidized copper surface and the polycrystalline zinc surfaces, prior to desorption from the surfaces. It is suggested that this is due to a rearrangement of mercury atoms on the surface at increasing temperatures, whereas at 85 K, mercury adhered to its initial adsorption position. In other words, mercury wet these surfaces on annealing, transitioning from an islanded surface at low temperature to a smooth layer before desorption. Based on these results, it was concluded that the mercury bond to the oxidized surface was weakened compared to clean copper. Furthermore, it is proposed that a surface phase transition occurred on polycrystalline zinc prior to desorption. No such transition was observed on iron.

Activation energies of desorption were calculated for the relevant metal surfaces. It was established that clean iron had the highest activation energy of desorption. The large bond strength between mercury and iron may account for the highest desorption temperature of the iron systems. Zinc and copper had similar activation energies and desorption temperatures, which were respectively lower than that of iron.

X-Ray Photoelectron and Auger Electron Spectroscopy were used to ascertain common surface contamination, i.e. chlorine, oxygen and sulfur, which affected mercury adsorption. Laser Ablation Inductively Coupled Plasma Time of Flight Mass Spectrometry was used to determine the depth of mercury adsorption on the samples. The technique also showed that the samples contained mercury in the surface layers.

Accompanied by the rising demand for metals is the increase in emissions from metals manufacturing. Moreover, it is critical to minimize sulfur dioxide emissions as particulates from soot continue to be released in the atmosphere. For scrap-based steelmaking, monolayer mercury adsorption on clean iron and copper at room temperature are significant results. With the rising use of electronic devices in vehicles, the sorting of scrap becomes increasingly important. Mercury not adsorbing on zinc at room temperature is also of relevance as it disproves the theory of increased mercury adsorption with the increased use of galvanized scrap in summer conditions. However, the low temperature studies showed multilayer adsorption of mercury on iron, zinc and copper, which has relevance for the reported temporal variations of mercury deposition in arctic regions.

Keywords: mercury, iron, zinc, sulfur dioxide, adsorption, pollution, thermal desorption, polycrystalline, surfaces, spectroscopy

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , xiv, 74 p.
Keyword [en]
mercury, zinc, iron, copper, sulfur dioxide, adsorption, pollution, spectroscopy, thermal desorption, polycrystalline, surfaces
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-26107ISBN: 978-91-7415-773-4 (print)OAI: oai:DiVA.org:kth-26107DiVA: diva2:370143
Public defence
2010-11-26, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20120326Available from: 2010-11-16 Created: 2010-11-15 Last updated: 2012-03-27Bibliographically approved
List of papers
1. The surface behavior of mercury on iron systems
Open this publication in new window or tab >>The surface behavior of mercury on iron systems
2006 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 6, 1049-1056 p.Article in journal (Refereed) Published
Abstract [en]

Thermal desorption Auger electron spectroscopy (TDAES) was used to investigate the circumstances under which mercury is adsorbed on the surface of iron in the temperature interval of 85 to 298 K. The effects of chlorine and oxygen modifications on the iron surface have also been investigated within the same temperature interval. It was seen that chlorine reduced the adsorption of mercury on polycrystalline iron at 85 K, as did oxygen. On the clean iron system at 298 K, only one monolayer (ML) of mercury adsorbed. The physisorption of mercury on chlorine and oxygen layers at low temperatures (LTs) is discussed in combination with the calculated activation energies of desorption, as well as the factors affecting the mechanism of adsorption at room temperature.

Keyword
atmospheric mercury, chemisorption, speciation, films
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-16221 (URN)10.1007/BF02735027 (DOI)000242967000023 ()2-s2.0-33846199496 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Surface chemistry of mercury on zinc and copper
Open this publication in new window or tab >>Surface chemistry of mercury on zinc and copper
2006 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 6, 1057-1066 p.Article in journal (Refereed) Published
Abstract [en]

Thermal desorption Auger electron spectroscopy (TDAES) was used to investigate mercury adsorption on the surfaces of zinc (Zn) and copper (Cu) in the temperature interval of 85 to 298 K. The effects of chlorine and oxygen modifications on the surfaces have also been investigated within the same temperature interval. On single crystalline Zn(0001), no mercury was adsorbed under any temperature or deposition conditions. On polycrystalline Zn at 85 K, a monolayer (ML) of mercury adsorbed, whereas no measurable quantity was observed at room temperature (RT). Predeposited chlorine was removed by exposure to mercury, most probably through formation of volatile HgCl2. Chlorine enhanced the adsorption of mercury on polycrystalline Cu at 87 K, whereas preoxidation reduced the coverage. Low temperatures (LTs) were conducive to mercury adsorption as compared to 298 K for the Cu systems studied. The physisorption of mercury on chlorine and oxygen layers at LTs is discussed, as well as the factors affecting the mechanism of adsorption at RTs. The desorption energies and surface enthalpies have been calculated for each system with mercury adsorption.

Keyword
atmospheric mercury, chlorine, zno(0001)-zn, adsorption, speciation
Identifiers
urn:nbn:se:kth:diva-16222 (URN)10.1007/BF02735028 (DOI)000242967000024 ()2-s2.0-33846223829 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Enhanced Sulfate Formation on Ozone-Exposed Soot
Open this publication in new window or tab >>Enhanced Sulfate Formation on Ozone-Exposed Soot
2011 (English)In: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964, Vol. 42, no 9, 615-620 p.Article in journal (Refereed) Published
Abstract [en]

Gas phase experiments were conducted to examine the heterogeneous oxidation of sulfur dioxide on methane soot in the presence of ozone and water vapor. The enhanced formation of sulfate at atmospheric pressure was confirmed by the use of a particle-into-liquid sampler (PILS) coupled with ion chromatography (IC). Due to the ozone oxidation, multilayer adsorption of sulfur dioxide on soot, as well as sulfate formation and physisorption on secondary surface layer sites were observed. The exposure also caused the soot to become hydrophilic, due to the formation of sulfuric acid and also likely the formation of carboxyl groups on the surface. The sulfate yield increased with ozone levels, but no increase was observed at ozone concentrations above 1000 ppm.

Keyword
Sulfate, Aerosol, Ozone, Soot, Chemisorption, XPS
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:kth:diva-26124 (URN)10.1016/j.jaerosci.2011.04.004 (DOI)000295148000005 ()2-s2.0-79960317269 (Scopus ID)
Note
QC 20101116. Updated from submitted to published (20111017)Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2017-12-12Bibliographically approved
4. Surface chemistry of mercury on zinc and copper
Open this publication in new window or tab >>Surface chemistry of mercury on zinc and copper
2006 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 6, 1057-1066 p.Article in journal (Refereed) Published
Abstract [en]

Thermal desorption Auger electron spectroscopy (TDAES) was used to investigate mercury adsorption on the surfaces of zinc (Zn) and copper (Cu) in the temperature interval of 85 to 298 K. The effects of chlorine and oxygen modifications on the surfaces have also been investigated within the same temperature interval. On single crystalline Zn(0001), no mercury was adsorbed under any temperature or deposition conditions. On polycrystalline Zn at 85 K, a monolayer (ML) of mercury adsorbed, whereas no measurable quantity was observed at room temperature (RT). Predeposited chlorine was removed by exposure to mercury, most probably through formation of volatile HgCl2. Chlorine enhanced the adsorption of mercury on polycrystalline Cu at 87 K, whereas preoxidation reduced the coverage. Low temperatures (LTs) were conducive to mercury adsorption as compared to 298 K for the Cu systems studied. The physisorption of mercury on chlorine and oxygen layers at LTs is discussed, as well as the factors affecting the mechanism of adsorption at RTs. The desorption energies and surface enthalpies have been calculated for each system with mercury adsorption.

Keyword
atmospheric mercury, chlorine, zno(0001)-zn, adsorption, speciation
Identifiers
urn:nbn:se:kth:diva-16222 (URN)10.1007/BF02735028 (DOI)000242967000024 ()2-s2.0-33846223829 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
5. Surface composition of industrial metal samples with potential for atmospheric mercury deposition
Open this publication in new window or tab >>Surface composition of industrial metal samples with potential for atmospheric mercury deposition
2010 (English)Report (Other academic)
Abstract [en]

Laser Ablation Inductively Coupled Plasma Time of Flight Mass Spectrometry, Auger electron spectroscopy and X-ray photoelectron spectroscopy were used to study atmospherically exposed metal samples for surface mercury concentration at room temperature. The metals were collected from industrial and pre-conditioned sources. In most cases, mercury detection was impossible because the samples were found to be highly contaminated from sources such as oxygen, carbon, chlorine and sulfur. However, the methods were effective at determining surface atoms and bulk substrate atoms that may be surface diffusive. Depth profiling was conducted on the samples that were found to contain mercury.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 20 p.
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-26127 (URN)KTH/MSE--05/91--SE+THMETU/ART (ISRN)
Note
QC 20101116Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2010-12-20Bibliographically approved

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