Magnetically modified nanogold-biosilica composite as an effective catalyst for CO oxidation

Abstract

The temperature-dependent biosynthesis of gold nanoparticles (AuNP) using diatom cells of Diadesmis gallica was successfully performed. The resulting biosynthesis product was a bio-nanocomposite containing AuNP (app. 20 nm) subsequently anchored on the silica surface of diatomaceous frustules. As-prepared nanogold-biosilica composite was tested as catalyst in the oxidation of carbon monoxide using gas chromatograph with thermal conductivity detector. For catalytic activity enhancement, bionanocomposite was magnetically modified by ferrofluid using two different methods, i.e., with and without the use of methanol. The oxidation of CO at 300 degrees C was 58-60% in the presence of nanogold-biosilica composites. CO conversion at 300 degrees C was only 15% over magnetically responsive sample modified in the presence of methanol. On the other hand, complete CO conversion was reached over direct (without methanol) magnetically modified nanogold-biosilica composite at 330 degrees C (GHSV = 60 l g(-1) h(-1)). Our results show, that the type of magnetic modification can influence the catalytic activity of bionanocomposite. The best catalytic effect in CO conversion established direct magnetically modified nanogold-biosilica composite.