Spectroscopic and conductometric study of complexes formed by humic and fulvic acid with metal ions

Abstract

The present study was carried out at the laboratory, Department of Soil Science and Agricultural Chemistry, College of Agriculture, Rajendranagar. The interactions of metal ions with humic substances in 1:1.5 molar ratio metal to ligand are investigated by spectroscopic technique with absorbance at 400 nm for Fe (II), Cu (II) and Zn (II) and 420 nm for Mn (II). The complexes formed by humic and fulvic acid with metal ions was studied by molar ratio method and job’s plot method. The results revealed that from Job’s plot for metal humates maximum absorbance occurred at X = 0.4, 0.4, 0.4 and 0.2 for Fe (II), Cu (II), Mn (II) and Zn (II) with humic acid and from the Job’s plot for metal fulvates maximum absorbance occurred at X = 0.8 for Mn (II) with fulvic acid respectively. In case of conductometric titrations humic acid conductance increased very slowly in the beginning and then followed by a steep rise and for fulvic acid the conductance decrease initially due to neutralisation of strong functional group with further addition of NaOH, a constant or slight increase is observed.