Chapter 3 Aquatic Chem Part 2

Chapter 3 Aquatic Chem Part 2 - Aquatic Chemistry Part Two...

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Unformatted text preview: Aquatic Chemistry Part Two Speciation The properties of metals dissolved in water depend largely upon the nature of metal species dissolved in the water. Therefore, speciation of metals plays a crucial role in their environmental chemistry in natural waters and wastewaters For example, cyanide with dissolved iron (II) Complexes and EDTA Ethylenediaminedisuccinic acid EDTA Ethylenediaminedisuccinic acid Production of [S, S]- EthyleneDiamineDiSuccinic Acid by Actinomycete Species Christina Kay Villavaso Environmental Studies Louisiana State University March 27, 2000 Chelating Agents Organic chemicals that bond with and remove free metal ions from solution Often polydentate ligands Have diverse industrial applications Conventional chelators are EDTA, NTA EDTA - most widely used chelator worldwide Industrial and Household Uses of Chelators (as a percentage of world markets) detergents 32% water treatment 18% pulp and paper 13% textile 4% cosmetics, foods, pharmaceuticals 3% concrete admixtures 5% gas scrubbing 2% agrochemicals 4% rubber production 2% photography 5% metal plating/cleaning 5% surface polishing, oil production, etc 7% detergents water treatment pulp and paper textile cosmetics, foods, pharmaceuticals concrete admixtures gas scrubbing agrochemicals rubber production photography metal plating/cleaning surface polishing, oil production, etc Source:www. Chemsoc.com/gateway/chembyte/cib/store. html Ethylenediaminetetraacetic Acid (EDTA) Cheap to produce, extensively used Not readily biodegradable Several countries have enacted regulations restricting its use and discharge. Others have even banned EDTA usage for some applications. Regulations plus increased environmental levels have sparked concern about toxicity and research into alternative chelators. EDTA EDTA is a polyamino carboxylic acid with the formula [CH2N(CH2CO2H)2]2 . Alternative Chelating Agents Generally, the more biodegradable a chelator is, the less effective it is. Recently, research has defined alternative chelators that are as effective as conventional chelators, but more biodegradable. For EDTA, that alternative was [S, S]- Ethylenediaminedisuccinic acid (EDDS.) Chelant Biodegradability Comparison Chelant Biodegradation using Acclimated Activated Sludge-0.4-0.2 0.2 0.4 0.6 0.8 1 1.2 Time (Days) Concentration (mM) EDTA PDDS NTA EDDS EDTA 0.8 0.775 0.8 0.75 0.8 0.75 PDDS 0.8 NTA 0.8 0.6 0.5 EDDS 0.8 0.575 0.25 0.2 0.2 0.12 10 20 30 40 50 60 Data summarized from Takahashi et al, Bioscience, Biotecnology, Biochemistry v. 61 no.11:1957-9 [S, S]-Ethylenediaminedisuccinic Acid First synthesized in 1964 by Kezerian et al. 4 stereoisomers possible: [S, S], [R, R], and [R, S/S, R] Hexadentate ligand, structural isomer of EDTA Chemically quite similar [S, S]-EDDS and its complexonates are easily degraded by photolysis and are ecologically safe. [S, S]-EDDS COOH COOH CH 2 H-C-NH-CH 2-CH 2-NH-C-H CH 2 COOH COOH EDDS Stereoisomer...
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This note was uploaded on 10/11/2011 for the course ENVS 4101 taught by Professor Portier during the Spring '10 term at LSU.

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Chapter 3 Aquatic Chem Part 2 - Aquatic Chemistry Part Two...

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