Trivalent chromium sorption on alginate beads

The applicability of trivalent chromium removal from aqueous solutions using calcium alginate beads was studied. The equilibrium isotherms were plotted at two temperatures. The relationship between the chromium sorbed and the calcium released was determined as well as the effect of alginate amount and initial pH on the equilibrium results. Chromium sorption kinetics were evaluated as a function of chromium initial concentration and temperature. Transport properties of trivalent chromium on alginate beads were characterised by calculating chromium diffusion coefficients-the Linear Absorption Model and the Shrinking Core Model were assayed. Trivalent chromium removal from aqueous solutions, that made chromium alginate beads by directly dispensing the sodium alginate solution on chromium solutions, was also tested. Finally, a methodology for trivalent chromium removal with alginate is proposed. This method includes two steps: in the first, chromium is removed by using it as an agent for alginate bead formation (for chromium concentrations above 400 mg l(-1)); afterwards, the obtained solution is placed in contact with previously formed alginate beads for removal of the remaining chromium. (C) 1997 Elsevier Science Ltd. All rights reserved.