Iron(III) reduction by natural humic acids: a potentiometric and spectroscopic study

Abstract

Summary The reduction of iron(III) by natural humic acid (NHA) was studied in aqueous solution as a function of pH, time and iron(III) concentration. The information gained from FTIR and ESR spectroscopies as well as potentiometric data suggests that redox reactions occur at a low pH due to the involvement of phenolic groups and radicals. At pH values higher than 3.5 the reaction is strongly inhibited by the formation of iron(III)–humate complexes.