EDDA
<p><b >Ethylenediamine-<i>N</i>,<i>N'</i>-disuccinic acid</b> (<b >EDDS</b>) is a <a href="http://en.wikipedia.org/wiki/Chelating_agent" title="Chelating agent" class="mw-redirect" >chelating agent</a> that may offer a biodegradable alternative to <a href="http://en.wikipedia.org/wiki/EDTA" title="EDTA" class="mw-redirect" >EDTA</a>, which is currently used on a large scale in numerous applications. Research into the synthesis and application of EDDS is mainly focused on the (S,S) <a href="http://en.wikipedia.org/wiki/Stereoisomer" title="Stereoisomer" class="mw-redirect" >stereoisomer</a>.<sup class="Template-Fact" >[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a></i>]</sup></p>
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(S,S)-EDDS is a biodegradable chelating agent that offers an alternative to EDTA, of which 80 million kilograms are produced annually. Under natural conditions, EDTA has been found to convert to ethylenediaminetriacetic acid and then cyclize to the diketopiperizide, which accumulates in the environment as a <a href="http://en.wikipedia.org/wiki/Persistent_organic_pollutant" title="Persistent organic pollutant" >persistent organic pollutant</a>.<sup id="cite_ref-7" class="reference" ><a href="http://en.wikipedia.org/wiki/Ethylenediamine-N,N%27-disuccinic_acid#cite_note-7" >[8]</a></sup> As an environmentally friendly alternative, (S,S)-EDDS can thus be used as a substitute for EDTA in its myriad applications. These uses usually revolve around removing or deactivating metal cations.<sup id="cite_ref-8" class="reference" ><a href="http://en.wikipedia.org/wiki/Ethylenediamine-N,N%27-disuccinic_acid#cite_note-8" >[9]</a></sup> When EDDS is applied in chemical-enhanced soil remediation in excessive case (e.g. when applied for ex-situ soil washing), higher extraction efficiency for heavy metals can be achieved and the amount of extraction is less independent with the EDDS dosage;<sup id="cite_ref-9" class="reference" ><a href="http://en.wikipedia.org/wiki/Ethylenediamine-N,N%27-disuccinic_acid#cite_note-9" >[10]</a></sup> On the other hand, during soil remediation which involves continuous flushing, metal extraction is often limited by the amount of EDDS. Under EDDS deficiency, initial unselective extraction of heavy metals was observed, followed by heavy metal exchange and re-adsorption of heavy metals that have lower stability constant with EDDS.<sup id="cite_ref-10" class="reference" ><a href="http://en.wikipedia.org/wiki/Ethylenediamine-N,N%27-disuccinic_acid#cite_note-10" >[11]</a></sup>
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