Abstract
Soil is composed of various minerals with variable amounts of organic matter that absorb many pollutants, which can be difficult and expensive to remove. High energy ball milling is an effective and cheap way of remediating contaminated soil. Research has shown that the initial step in the process is predominantly the ionization of the polluting organic molecules to form a radical. This radical initiates a chain reaction, thus destroying the organic pollutant.
The site(s) of ionization on the organic molecule has yet to be identified. Initial studies using diesel and some small molecules suggested that the ionization potential of the molecule is important, but the volatility of these small molecules had made these results uncertain. In this study, a range of large organic molecules with low volatilities has been investigated. These molecules contained a range of functional groups and were milled in quartz to determine their destruction rates. This enabled the investigation of whether destruction rates are dependent on the functional group or the main carbon chain in the organic compounds. Whether ionization is the major initiator was investigated as well.
It was found that the functional group does in fact play a major role in the destruction rates of the compounds. In order of destruction difficulty: The most difficult to destroy was found to be the alkene hexadecane then in order of increasing ease of destruction: hexadecanone, hexadecanol, methyl hexadecanoate, hexadecanoyl chloride, propyl hexadecanoate, ethyl hexadecanoate, hexadecanoic acid, hexadecylamine, decyl hexadecanoate, hexadecane and the fastest was n-ethylhexadecanamide.
Comparison of the destruction rates with the ionization energies of the functional groups showed, a modest relationship. While the ionization of the functional group does play a part, destruction is clearly a more complicated process.
