This thesis develops and demonstrates an innovative method for adsorbing metals from metal mine drainage in mid-Wales and northern Italy using dealginated seaweed (DS) as a biosorbent. The chemical composition of 15 mine drainages and two receiving waters in Wales was determined over a two year period in relation to precipitation and season. The waters were circum-neutral, iron-poor (<1 mg/L) but metal-rich, dominated by Zn ( 42 mg/L), Cu ( 188 μg/L), Cd ( 99 μg/L) and Pb ( 2.7 mg/L). The chemical composition varied throughout the year, but did not necessarily show clear seasonal variation, with Zn, Cd and Pb tending to show a winter maximum. The physico-chemical adsorption characteristics of the DS were determined. Over 80 % of Zn, Cd and Pb were removed from solution within 15 minutes of contact; adsorption was not affected by pH (between 3.3 and 6.6) nor by additional elements in solution. The adsorption capacity of the DS was Pb > Cd > Zn. The main removal mechanisms were determined to be adsorption and ion exchange with Ca, Na, Mg released from the DS surface. Treatment plants containing DS were deployed at three sites in mid-Wales and one site in Italy. In mid-Wales, Zn, Pb and Cd adsorption peaked within an hour (at ~98 %) associated with a significant release of Ca, Mg and Na. The DS adsorbed Pb > Cd > Zn, with the DS adsorbing ~1 % of its dry weight of Pb, ~0.01 % Cd and ~2 % Zn. The saturation of the DS was dependent on the mine drainage composition, with adsorption continuing for several months when low metal concentration (<1 mg/L) mine drainages were remediated. In Italy, acidic (~pH 2.5), metal-rich ( 120 mg/L Al, 420 mg/L Fe and 99 mg/L Cu) mine drainage required neutralisation and Fe-removal before entering the DS treatment plant to remove the remaining metals. The treatment plants improved the quality of mine drainage and reduced their impact on receiving water courses; the plant was designed to be a practical, low-cost, solution which uses a waste product (from the alginate industry). This thesis demonstrated a novel method for remediation of neutral, low Fe waters, and is applicable as a final ‘polish’ when acidic, Fe-rich water has been neutralised and the Fe removed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:511225 |
| Date | January 2008 |
| Creators | Hartley, Suzanne |
| Contributors | Perkins, William ; Pearce, Nicholas |
| Publisher | Aberystwyth University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/2160/b9217acb-b8ad-4180-af12-a1627d7137c4 |
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