title: Preparation and Properties of Natural, Demineralized, Pure, and Doped Carbons from Biomass; Model of the Chemical Structure of Carbonized Charcoal.

authors: Bourke, Jared

subjects: Flash Carbonization

abstract: Pioneering work performed by Rosalind Franklin over half a century ago provided the first structural models of two distinct carbon types: those that become graphitic during carbonization at high temperatures, and those that do not. Moreover it is known that certain properties of carbonaceous materials including combustion, surface area, electrical resistivity, and catalytic properties are influenced by mineral impurities.  The nature of this division in biocarbon structure and the known effects of minerals on carbon properties have led to this work; three principal topics were addressed; (1) the investigation of the solid state structure of biocarbons derived from various biomass feedstocks, (2) the removal of inorganic minerals from biomass, and (3) the investigation of biocarbon electronic structure subsequent to doping with select inorganic minerals.

Charcoals and carbonized charcoals (i.e. biocarbons) were prepared from a wide variety of biomass substrates, including pure sugars containing 5- and 6-membered rings with furanose and pyranose configurations, lignin, agricultural residues (corncob and nut shells) and a hard wood.  These biocarbons were subject to proximate and elemental analysis, gas sorption analysis, and analysis by ICP-MS, SEM, XRD, ESR, 13C CPMAS NMR, and MALDI-TOF MS.  All the carbonized charcoals contained oxygen heteroatoms, had high surface areas, and were excellent conductors of electricity.  Doping the biocarbon with boron or phosphorus resulted in a slight improvement in its electrical conductivity.  The XRD analysis indicated that the carbonized charcoals possess an aromaticity of about 71% that results from graphite crystallites with an average size of about 20  .  The NMR analysis confirmed the highly aromatic content of the carbonized charcoals.  The ESR signals indicated two major types of carbon-centered organic radicals.  A number of techniques employed highlighted differences between carbonized charcoals and synthetic graphite but none more so than MALDI-TOF spectrometry.  The biocarbons contained readily desorbed discrete ions with m/z values of 701, 685, 465, 453, 429, and 317.  All of the above findings were used to develop a model for the structure of carbonized charcoal that is consistent with the biocarbon's oxygen content, microporosity and surface area, electrical conductivity, radical content, and its MALDI-TOF spectra.

The removal of inorganic mineral constituents from various biomass feedstocks was achieved via simple washing/soaking techniques using two different aqueous media; deionized water and citric acid.  The most effective and consistent demineralization treatment for removing minerals from biomass involved a hot 0.1 molL-1 citric acid percolation treatment, ca.  67% of inorganic mineral matter was removed.  Mineral matter at the levels present in typical biomass derived charcoals and carbons had no significant influence upon the surface area or the electrical resistivity in carbonaceous materials after high heat treatment (950  C).

text: Preparation and Properties of Natural, Demineralized, Pure, and Doped Carbons from Biomass; Model of the Chemical Structure of Carbonized Charcoal. Pioneering work performed by Rosalind Franklin over half a century ago provided the first structural models of two distinct carbon types: those that become graphitic during carbonization at high temperatures, and those that do not. Moreover it is known that certain properties of carbonaceous materials including combustion, surface area, electrical resistivity, and catalytic properties are influenced by mineral impurities.  The nature of this division in biocarbon structure and the known effects of minerals on carbon properties have led to this work; three principal topics were addressed; (1) the investigation of the solid state structure of biocarbons derived from various biomass feedstocks, (2) the removal of inorganic minerals from biomass, and (3) the investigation of biocarbon electronic structure subsequent to doping with select inorganic minerals.

Charcoals and carbonized charcoals (i.e. biocarbons) were prepared from a wide variety of biomass substrates, including pure sugars containing 5- and 6-membered rings with furanose and pyranose configurations, lignin, agricultural residues (corncob and nut shells) and a hard wood.  These biocarbons were subject to proximate and elemental analysis, gas sorption analysis, and analysis by ICP-MS, SEM, XRD, ESR, 13C CPMAS NMR, and MALDI-TOF MS.  All the carbonized charcoals contained oxygen heteroatoms, had high surface areas, and were excellent conductors of electricity.  Doping the biocarbon with boron or phosphorus resulted in a slight improvement in its electrical conductivity.  The XRD analysis indicated that the carbonized charcoals possess an aromaticity of about 71% that results from graphite crystallites with an average size of about 20  .  The NMR analysis confirmed the highly aromatic content of the carbonized charcoals.  The ESR signals indicated two major types of carbon-centered organic radicals.  A number of techniques employed highlighted differences between carbonized charcoals and synthetic graphite but none more so than MALDI-TOF spectrometry.  The biocarbons contained readily desorbed discrete ions with m/z values of 701, 685, 465, 453, 429, and 317.  All of the above findings were used to develop a model for the structure of carbonized charcoal that is consistent with the biocarbon's oxygen content, microporosity and surface area, electrical conductivity, radical content, and its MALDI-TOF spectra.

The removal of inorganic mineral constituents from various biomass feedstocks was achieved via simple washing/soaking techniques using two different aqueous media; deionized water and citric acid.  The most effective and consistent demineralization treatment for removing minerals from biomass involved a hot 0.1 molL-1 citric acid percolation treatment, ca.  67% of inorganic mineral matter was removed.  Mineral matter at the levels present in typical biomass derived charcoals and carbons had no significant influence upon the surface area or the electrical resistivity in carbonaceous materials after high heat treatment (950  C).

year: 2007

title: Using Stata for applied research: reviewing its capabilities

authors: Baum, Christopher F.

subjects: Stata

abstract: The paper reviews Stata's capabilities.

text: Using Stata for applied research: reviewing its capabilities The paper reviews Stata's capabilities.

year: 2011

title: Adult education within a circular migration scheme. A case study from New Zealand

authors: Morrison, Sandra L.

subjects: adult education

abstract: This article examines the adult education and learning that occurs between a Māori business and the workers they employ from the Pacific nation of Tonga through the Recognised Seasonal Employer (RSE) scheme, a seasonal labour strategy allowing for the temporary entry of migrant workers in the horticulture and viticultural industries, with a preference for workers from the Pacific nations.. Māori are indigenous to NZ but their historical ties extend back to Polynesia in the Pacific and therefore common historical narratives exist between Māori and those from Tonga. A case study approach is used to highlight how adult education is embedded. Central to the success of this case study is the validation and implementation of indigenous knowledges and rituals.

text: Adult education within a circular migration scheme. A case study from New Zealand This article examines the adult education and learning that occurs between a Māori business and the workers they employ from the Pacific nation of Tonga through the Recognised Seasonal Employer (RSE) scheme, a seasonal labour strategy allowing for the temporary entry of migrant workers in the horticulture and viticultural industries, with a preference for workers from the Pacific nations.. Māori are indigenous to NZ but their historical ties extend back to Polynesia in the Pacific and therefore common historical narratives exist between Māori and those from Tonga. A case study approach is used to highlight how adult education is embedded. Central to the success of this case study is the validation and implementation of indigenous knowledges and rituals.

year: 2015