Attachment of two distinct humic acids onto a silica gel surface

A method for the attachment of two different humic acids onto silica gel has been developed. In the first step, the precursor was prepared by reacting the silylant agent 3-aminopropyltrimethoxysilane (APTS) with silica gel. Elemental analysis of the product showed the presence of 1.23 mmol of silylant agent per gram of support. Humic acid extracted from peat soil, HAPS, and commercial humic acid, HAFL, were connected by hydrogen bonds to the amine groups previously anchored onto silica gel, producing new materials named SiHAPS and SiHAFL, with 84.7 ± 0.04 and 101.7 ± 0.04 mg of humic acid per gram of modified silica for SiHAPS and SiHAFL, respectively. Thermogravimetry, infrared, 13C and 29Si CP/MAS–NMR spectra have confirmed the success of the attachment and the scanning electron microscopy–energy dispersive spectrometer (SEM–EDS) technique showed a good dispersion of the humic acids onto modified silica surface for both materials.