Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 17, 1996
Publication Date: N/A
Interpretive Summary: The presence of dyes in textile wastewaters is an environmental problem. A chemically-modified starch was synthesized using inexpensive reagents and examined for its ability to bind textile dyes. The modified starch bound various dyes, although to an extent that was less than expected based on its composition. Dye binding was highly dependent on the pH of the dye solution. These findings indicate that this material might be useful to treat certain types of wastewaters at low pH to remove contaminating dyes.
Technical Abstract: Crosslinking of starch with epichlorohydrin in the presence of NH4OH, NaOH, and water was studied. The reaction was optimized and the products analyzed by solid-state **13C-NMR in the presence of water, acid-base titration, and dye-binding measurements. The presence of different types of hydroxypropyl groups was confirmed by NMR, but their linkage to polysaccharide could not be confirmed because of their minor abundance relative to all other CH2 groups, and because the motion of the sidechains is much greater than the starch component which remains fairly constant despite the presence of water. Adding NH4OH and lowering the quantity of water in the reaction increases the yield of crosslinked material. Potentiometric titration methods on resin in H**+ form or in non-ionized form gave smaller exchange capacity values than those determined by elemental analysis. The dye-binding is pH-dependent and increased quantity yof dye is bound at lower pH. The trivalent dye (hydrolyzed Brilliant Red F3B) was bound less effectively on a molar basis by the resin at the acidic pH range than the monovalent dye (Alizarin Red S). The values of dye-binding capacities are lower than the ion-exchange capacities determined by potentiometric titration.