1Raman Centre for Applied and Interdisciplinary Sciences, 16A Jheel Road, Kolkata, 700 075
2Department of Agricultural Chemistry & Soil Science, University of Calcutta, 35 B.C. Road, Kolkata, 700 019
#Present address: NBSS & LUP (ICAR), Regional Centre, Jorhat, Assam
A siliceous allophane was interacted with soil humic acid (HA) and fulvic acid (FA) at various pH to study the complexes of allophane-HA and allophane-FA. Fixation of HA as well as FA reduced with pH due to increasing charges on allophane as well as on the humic molecules. At similar pH, FA showed dramatically lower fixation compared to HA. This was due to more negative charges on FA and its greater hydrophilic nature. The allophane-HA complex was probed by x-ray diffraction (XRD), infrared spectroscopy (IR) and differential thermal analysis (DTA). XRD of allophane-HA complex exhibited little change; it was inferred that the amount of HA was too little in the complex to affect any notable alteration. Except for a broad strong absorption in 3500–3450 cm−1 region, other IR bands remained unaffected; this suggested weak interaction between allophane and HA. The DTA exotherm, however, spread out indicating involvement of various types of bonding in the complexation process.
