Browsing by Author "Nguyen, Duy V."

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Addition of copper-sequestering agents to alginate gel to enhance copper recovery from aqueous media
(1995-11) Jang, Larry K.; Nguyen, Duy V.; Kolostyak, K.; Geesey, Gill G.
A mixture of sodium alginate and sodium polystyrenesulfonate (NaPSS) was used as the absorbent for copper in this work. A viscous solution of the mixture was dispensed into a copper-containing solution circulating in a loop fluidized bed reactor to form alginate gel in situ. Batch absorption data was treated by Langmuir model to yield copper binding capacity and binding stability constant. Results were compared with those of our previous work in which no NaPSS was added to Na-alginate. Based on the Langmuir parameters, the critical copper concentration above which the addition of NaPSS can enhance the copper loading of the alginate gel was calculated. The ratio of copper loading of the alginate gel with the addition of NaPSS to that without the addition of NaPSS at any copper concentration was predicted as well. Similar calculations were made for the case of using the mixture of Na-alginate and Microcystis as the copper absorbent.
Effect of pH on the absorption of cu(ii) by alginate gel
(1995-01) Jang, Larry K.; Nguyen, Duy V.; Geesey, Gill G.
The absorption of copper from synthetic solutions of cupric sulfate (initial Cu concentration: 200 ppm, initial pH: 2.4 or 3.4) in a batch loop fluidized bed reactor by alginate gels was investigated. Compared to the results obtained without addition of sulfuric acid [Jang L. K., Geesey G. G., Lopez S. L., Eastman S. L. and Wichlacz P. L., Wat. Res. 24, 889–897 (1990)], the copper-binding efficiency of the alginate gels at pH 3.4 was affected mildly by the acidity of the solution; at pH 2.4, the percent copper recovered was reduced by roughly one-half. In this work, an extended Langmuir model that took into account the competition between monovalent hydrogen ions and divalent cupric ions for the carboxyl groups on the alginate molecules was derived. This model yielded the binding group density of the alginate gel and binding stability constants for cupric alginate and alginic acid simultaneously. The new model was shown to be superior to the simple Langmuir model that expressed the results as conditional copper binding stability constant and capacity at a given pH. Application of the extended Langmuir model to the prediction of copper binding at pH 2 is also illustrated.
An equilibrium model for absorption of multiple divalent metals by alginate gel under acidic conditions
(1999-08) Jang, Larry K.; Nguyen, Duy V.; Geesey, Gill G.
An extended Langmuir model was proposed in this work to describe the simultaneous absorption of multiple divalent metal ions and hydrogen ions from acidic metal-containing aqueous media by an absorbent having one kind of active functional group. A viscous Na–alginate solution was directly dispensed dropwise into the acidic aqueous media containing dissolved copper and zinc to form spherical Cu–Zn–H–alginate gels which subsequently absorb these ions until final equilibrium was reached in batch experiments. Initial pH of the aqueous media was in the range of 2.6–5.4. Binding group density and binding stability constants of alginic acid, cupric alginate and zinc alginate were obtained simultaneously by fitting data to the proposed model developed in this work. Application of the constants obtained to the prediction of the extent of absorption of copper and zinc from an aqueous medium having an initial pH in the range of 2.6–5.4 is illustrated and compared with experimental results.
Selectivity of alginate gel for cu vs co
(1995-01) Jang, Larry K.; Nguyen, Duy V.; Geesey, Gill G.
The selectivity of the kelp alginate gel for copper compared to cobalt was investigated. When copper and cobalt existed at relatively high concentrations (100 ppm each), Na-alginate solution was directly dispensed into the mixed solution circulating in a loop fluidized bed reactor to produce CuCo-alginate gels in situ. Two extended Langmuir models were derived and tested against experimental data in this work: Model 1 was a general Langmuir model for two absorbates competing for the same type of binding site. Model 2 was based on the “egg-box” model for gelation of sodium alginate in the presence of divalent metal ions with the assumption that each metal ion would bind two carboxyl groups on neighboring uronate residues that formed the “site”. It was found that Model 1 data better and parameters obtained from Model 1 were used to predict the amount of Na-alginate needed to “polish” a cobalt solution containing a trace amount of copper.