Ash admixtures formed during the loss on ignition (LOI) procedure and their impact on laser textural analysis results

Abstract

We present an experimental study that explores the feasibility of using the ash from biogenic deposits for laser textural analysis. The results have demonstrated that conducting ash textural analysis without prior chemical treatment can lead to unreliable results. Among other things, this is due to the “contamination” of the ash with aggregates formed by metal oxides and carbonates during ignition ($LOI_{550}$ procedure) in a muffle furnace. Metal oxides and carbonates can create aggregates with silt and clay grains. As a result, the material coarsens, mainly to very coarse and coarse silt fractions. It is illustrated that the ash after $LOI_{550}$ has been contaminated with oxides and carbonates of iron (Fe), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), sodium (Na), zinc (Zn), lead (Pb) and copper (Cu). Thus, we suggest a method of using 10% HCl to purify the ash from metal oxides and carbonates (so-called ash purification procedure or APP). The analysis in this paper focuses on the grain size composition of ash, both untreated and HCl-treated. The obtained results have been compared and discussed in detail.