esm222_15_16_reaction

esm222_15_16_reaction - ESM 222 Transformation of...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 © Arturo A. Kel er ESM 222 Transformation of Pollutants 2 © Arturo A. Kel er Transformation of Pollutants ± Chemical processes ± Biological processes ± Radioactive decay 3 © Arturo A. Kel er Chemical processes ± Examples of chemical reactions: ± Oxidation ± Reduction ± Hydrolysis ± Elimination ± Substitution ± Photolysis 4 © Arturo A. Kel er Transformation ± Important factors for transformation ± Chemical structure ± configuration ± functional groups ± Presence of reactant(s) ± Availability of the pollutant ± sorption ± NAPL 5 © Arturo A. Kel er Transformation ± Chemical Structure ± Branching ± Carbon bond saturation ± Halogenation ± Oxygen in molecule ± Similarity to biochemicals ± (Hydrophobicity) 6 © Arturo A. Kel er Transformation ± For metals ± oxidation state ± pH ± redox conditions ± presence of certain anions (e.g. S 2- )
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
7 © Arturo A. Kel er Transformation ± Other environmental conditions ± presence of oxygen (atmosphere or DO) ± temperature ± pH (abiotic and biotic) ) T T ( r r ) T ( k ) T ( k 1 2 1 2 = θ ) RT / E exp( A k a r = k r = rate of reaction, A = rate coefficient E a = activation energy 8 © Arturo A. Kel er Rate of Reaction ± First-order reaction ± Zero-order reaction ] C [ k dt ] C [ d r = ) t k exp( C ) t ( C r o = r k dt ] C [ d = t k C ) t ( C r o = 9 © Arturo A. Kel er Rate of Reaction ± Second Order C B A + ] B ][ A [ k dt ] A [ d r = If the concentration of B (e.g. enzyme, O 2 , catalyst) doesn’t change with time, then consider the reaction as “pseudo” first-order in A. 10 © Arturo A. Kel er Chemical processes ± Oxidation ± Pollutant reacts with oxygen or another oxidizing chemical (e.g. ozone, hydrogen peroxide H 2 O 2 , singlet oxygen O . , OH . radicals, Cl 2 , Br 2 , F 2 , H 2 SO 4 , HCl), producing a more oxidized product ± In certain circumstances, reaction will result in complete oxidation of the pollutant 11 © Arturo A. Kel er Oxidation ± The end results of oxidation processes are typically CO 2 , H 2 O, NO/NO 2 , NO 3 - , SO 2 , HSO 4 - ± Complete oxidation of complex organic molecules may take a long time without the addition of energy or a catalyst 12 © Arturo A. Kel er Oxidation CH 4 + 2 O 2 CO 2 + 2 H 2 O Even this simple reaction has to go through several steps: • A methane molecule first strikes one oxygen molecule • partially reacts (usually forming a rather unstable intermediate) • strikes other oxygen molecules/atoms to form carbon dioxide and water
Background image of page 2
13 © Arturo A. Kel er Oxidation Complete oxidation usually involves several steps: R-C + O 2 R-C + O . H H H H OH H R-C + O . R-C + H 2 O H OH H O H reduced (hydrocarbon) alcohol aldehyde 14 © Arturo A. Kel er Oxidation R-C + O 2 R-C + O . O H O OH oxidized form (acid) R-C + O . R . + CO 2 + OH . O OH 15 © Arturo A. Kel er Oxidation ± All organic molecules can be oxidized in the environment, but some are more susceptible to oxidation than others ± Oxidation may be ± in a dark environment (e.g. subsurface, deeper water) ± promoted by the presence of light which forms free radicals ± accelerated by biological processes 16 © Arturo A. Kel er
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/06/2008 for the course ESM 222 taught by Professor Keller during the Spring '08 term at UCSB.

Page1 / 13

esm222_15_16_reaction - ESM 222 Transformation of...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online