KINETICS OF SINGLE AND MULTIPLE METAL-ION SORPTION PROCESSES ON HUMICSUBSTANCES

Single and multiple metal ion reaction processes were studied on humic acids (HA) from various sources, A sequential sampling method (sample s periodically removed from the bulk reaction volume) was used. Experi mental parameters studied included pH, temperature, HA and peat source s, metal type and concentration,The Langmuir-Hinshelwood (LH) kinetics approach was used to describe the sorption kinetics of metal ions ont o HA. Great differences were found among the metals in the extent of r eaction and sorption kinetics, The extent of reaction was Cr(III) > Pb (II) > Cu(II) > Ag(I) > Cd(II) = Co(II) = Li(I) for single metal adsor ption and Cr(III) >> Pb(II) > Cu(II) = Ag(I) = Cd(II) = Co(II) Li(I) f or multiple metal adsorption on Humic Acid No. 1. The multiple ion sor ption kinetics were similar between HA from different sources, For pea t reactions, the extent of multiple metal ion sorption was Cr(III) > P b(II) > Cu(II) > Ag(I) > Co(II) = Cd(II) = Li(I). The sorption rates o f all metal ions on HA were very rapid, Most adsorption occurred withi n 2 minutes, but sorption did not reach equilibrium in 1 day under com petitive conditions, The presence of Cr(III) greatly decreased the ads orption of all other metals to the extent that some were not adsorbed at all, For all metal ions studied, less total sorption of each metal ion occurred in the presence of multiple competing ions than with sing le metal ions. Pearson's Hard Soft Acid Base principles and Klopman's generalized perturbation theory of chemical reactivity generally predi cted the sorption preference between metal ions and humic substances,A nonlinearity concept was used to rationalize the use of the LH kineti c model.