ATOMIC-FORCE MICROSCOPY OF HUMIC-ACID

Structural analysis of humic acid extracted from a Cecil soil was cond ucted by atomic force microscopy (AFM) of monolayer thin films of humi c acid deposited on mica strips using the Langmuir-Blodgett deposition technique. The humic acid specimens display a fibre-like morphology s howing prominent hexagonal structures of benzene rings at a molecular level of resolution. The side chains attached to these ring structures were identified by infrared spectroscopy to be carboxyl and carbonyl groups as indicated by absorption bands at 1625 and 1720 cm(-1), respe ctively. The presence of C-H alkyl chains were detected by bands at 29 17 and 2850 cm(-1). This AFM observation provides the first direct evi dence supporting the theoretical description of humic acid molecules c onsisting of benzene rings with various sizes of alkyl chains.