Catalytic Polymerization of Hydroquinone by Nontronite

The catalytic power of Ca-nontronite (0.2-2 μm) in the polymerization of hydroquinone was studied. The polymerization reaction proceeded abiotically, since there was no evidence of microbial growth in the system studied. The polymerization of hydroquinone in the presence of Ca-nontronite was substantially higher in air than in an N2 atmosphere, indicating the synergistic effect of Ca-nontronite and O2 in enhancing the reaction. After a sodium metaphosphate treatment to block the edges of Ca-nontronite, both absorbances at 472 and 664 nm of the supernatant and yield of humic macro-molecules in the Ca-nontronite-hydroquinone system were significantly decreased. However, the treatment did not eliminate the catalytic effect of Ca-nontronite. The results indicate that both Fe(III) on the edges and other Lewis acid sites of Ca-nontronite contributed to promoting the polymerization of hydroquinone. IR and ESR spectra of FA (MW > 1000) and HA (MW > 1000) formed in the supernatants of the Ca-nontronite-hydroquinone system were similar to those of natural humic substances.