The innovative process of removal of toxic heavy metals from water by biosorption, using the dead biomass of Sargassum marine alga packed in flow-through columns, was examined. The mechanism of uptake of Cu 2+, Zn2+, Cd2+, Fe2+, and Cr(III) by the biomass was identified as ion exchange taking place at the weakly acidic functional groups embedded in the cellular matrix of the seaweed. After pretreatment with mineral acids, the cation exchange capacity of the biomass was approximately 2.3 meq/g of biomass dry weight which is comparable to the metal binding capacities of commercial ion exchange resins. / The issues related to the biosorption process design, optimization, and limits of applicability were addressed by (1) evaluating different ionic cycles for biomass in columns at different normalities of the feed, (2) assessing the interference of iron in biosorption of a toxic metal, and (3) analyzing the effects of competitive binding of several toxic metals in the flow-through column including the metal elution order and the overshoots of the concentrations of toxic species in the column effluent over their feed levels. The column models, previously developed for ion exchange, such as the Equilibrium Column Model (ECM) and the Mass Transfer Column Model (MTCM) were used to fit the experimental data and to predict the service time of biosorption columns treating binary and multi-metal mixtures. The application of the theory of ion exchange to describing and assessing the process of metal sequestering by biomass in flow-through columns represents an original work. / The investigation into the removal of hexavalent chromium by Sargassum biomass revealed that the latter could take up approximately 60 mg/g (2.3 meq/g) at pH 2 while reducing some of the Cr(VI) to Cr(III). A combined ion exchange-redox mechanism of Cr(VI) removal was proposed whereby, at pH > 2, the Cr(VI) is assumed to be taken up from water primarily by an anion exchange mechanism, while at pH < 2 the reduction of Cr(VI) to Cr(III) controls the binding of chromium to the seaweed. The effect of pH on the Cr(VI) removal was explained through the dependence of the reduction potential of HCrO4- ions on the pH of the liquid.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.34988 |
| Date | January 1997 |
| Creators | Kratochvíl, David. |
| Contributors | Volesky, B. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001618203, proquestno: NQ44480, Theses scanned by UMI/ProQuest. |
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