Methodological limitations to determining acidic groups at biochar surfaces via the Boehm titration

The Boehm titration is frequently employed to characterize acidic groups at biochar surfaces. However, biochars contain inorganic basic components (carbonates, oxides, hydroxides), inorganic acidic species (silica, alumina) and organic acids (carboxylic acids, phenols, humic-like substances) that ca...

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Bibliographic Details
Published inCarbon (New York) Vol. 66; pp. 730 - 733
Main Authors Tsechansky, L., Graber, E.R.
Format Journal Article
LanguageEnglish
Published Elsevier Ltd 01.01.2014
Subjects
Aluminum oxide
Carbon
Hydroxides
Oxides
Precipitates
Precipitation
Titration
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Summary:The Boehm titration is frequently employed to characterize acidic groups at biochar surfaces. However, biochars contain inorganic basic components (carbonates, oxides, hydroxides), inorganic acidic species (silica, alumina) and organic acids (carboxylic acids, phenols, humic-like substances) that can be differentially solubilized in the Boehm bases, rendering invalid results. This is demonstrated for two biochars. Prior to titrations (Boehm or continuous), biochar should be pretreated with NaOH to remove solubilizable acidic species, and then with HCl to remove solubilizable basic components and protonate carbon acid sites. Pretreatment is successful when direct and indirect titrations yield identical results and no precipitate is observed.
Bibliography:ObjectType-Article-2
SourceType-Scholarly Journals-1
ObjectType-Feature-1
content type line 23
ISSN:0008-6223
1873-3891
DOI:10.1016/j.carbon.2013.09.044