The adsorption of aquatic humic substances by iron oxides |
| |
| Authors: | E Tipping |
| |
| Institution: | Freshwater Biological Association, The Ferry House, Ambleside, Cumbria, U.K. |
| |
| Abstract: | The interactions of humic substances from Esthwaite Water with hydrous iron oxides (α-FeOOH, α-Fe2O3, amorphous Fe-gel) have been examined by measuring adsorption isotherms and by microelectrophoresis. In Na+-Cl?-HCO3?at I = 0.002 M (medium I) the extent of adsorption decreases with increasing pH. The results are consistent with a mechanism involving ligand exchange of humic anionic groups with H2O and OH?of surface Fe-OH2+and Fe-OH groups respectively, with an increasing degree of protonation of the adsorbed humics as the adsorption density increases at constant pH.At pH 7 in a medium containing Mg2+, Ca2+ and SO42?, at their Esthwaite Water concentrations and at I= 0.002 M (medium II) the adsorption capacity of goethite (α-FeOOH) is approximately twice that in medium I. Electrophoresis experiments show that the extra capacity is associated with coadsorption of Mg2+ and/or Ca2+ ions.When the iron oxides are added to samples of Esthwaite Water itself they become negatively charged and plots of electrophoretic mobility against pH for the natural water are identical to those in medium II plus humics. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
