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WP2 Wastewater Treatment: Analysis, Fate and Removal of Emerging Contaminants
(REH-1115-826333) Fate of primary alkane sulphates (PAS) under anaerobic conditions- effect of branching on biodegradability.
REHMAN, N1, MELLING, J2, VAN DUYNHOVEN, J3, ROBERTS, D4, 1 UNILEVER COLWORTH, SHARNBROOK, BEDFORDSHIRE, UNITED KINGDOM2 UNILEVER COLWORTH, SHARNBROOK, BEDFORDSHIRE, UNITED KINGDOM3 UNILEVER R&D, VLAARDINGEN, NETHERLANDS4 LIVERPOOL JOHN MOORES UNIVERSITY, LIVERPOOL, UNITED KINGDOM
ABSTRACT- Household products e.g. detergents are typically comprised of anionic surfactants that can occur as linear or branched structures. It is well established that linear structures i.e. linear alkyl benzene sulphonate (LAS) tend to undergo rapid aerobic biodegradation, and some surfactants are also able to undergo anaerobic biodegradation e.g. fatty alcohol sulphates and alcohol ether sulphates. The effect of branching during aerobic biodegradation is also reasonably well understood e.g. the distance principle demonstrated with LAS i.e. the further the sulphonate group from the terminal end of the alkyl chain the more rapid the biodegradation. Despite the subtle differences in structure, LAS and PAS are both known to degrade rapidly under aerobic conditions. However unlike LAS, PAS is also able to degrade anaerobically, often at quite significant rates. There is some understanding about the mechanism of anaerobic biodegradation that occurs with sulphates/sulphonates, however any limits to anaerobic biodegradation due to branching (e.g. methyl, ethyl) has not been studied. We present the results of an anaerobic biodegradation study carried out with a series of PAS samples each with different extents of B and methyl branching. Branching characteristics i.e. extent and position of B branching and methyl distribution were determined by NMR. A mechanistic theory to describe B-oxidation occuring in these structures is presented to explain the poor extent of anaerobic biodegradation seen with branched PAS (36%) versus a more linear PAS (68%).
Key words: Fate, Branching, Anaerobic, NMR
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