Green, zero-waste pathway to fabricate supported nanocatalysts and anti-kinetoplastid agents from sugarcane bagasse

The conversion processes of sugarcane into direct-consumption sugar and juice are generating a tremendous amount of waste, the so-called sugarcane bagasse. Biochar preparation is among the practical solutions aiming to valorize this agrowaste and make it of a high added value functional material (FM). Herein, we propose a novel zero-waste pathway where sugarcane bagasse was first dispersed in a hydroalcoholic solution and the dispersion was then ultrasonicated in order to extract natural reducing and capping agents. Subsequently, silver and copper ions were added to get adsorbed under a controlled atmosphere prior to heat treatment. The suspension was later filtered to provide (i) Ag/Cu-Ag+/Cu2+-loaded biomass sludge, and (ii) a clear filtrate containing residual metal ions which was microwaved in order to generate unsupported Ag/Cu nanoparticles (NPs). The free Ag/Cu nanoparticles (FM2) were tested as anti-kinetoplastid material against two flagellate models namely Leishmania spp and Trypanosoma cruzi. Free Ag/Cu nanoparticles showed the highest leishmanicidal and trypanocidal effects with an IC50 of 2.909 ± 0.051; 3.580 ± 0.016 and 3.020 ± 0.372 ppm for L.donovani, L. amazonensis and Trypanosoma cruzi, respectively. The impregnated biomass was pyrolyzed to provide Ag/Cu-loaded biochar (FM1). The latter exhibited high catalytic activity in the total mineralization of methylene blue. The experimental data followed the first and the pseudo-second order rate laws with apparent mineralization rate constants K1 45 10-3 min-1 and K2 0.115 g.mg-1.min-1, respectively. To sum up, sugarcane bagasse agrowaste was valorized as a source of natural reducing agents of metal ions into free and biochar-supported metallic nanoparticles. In this way, we combine two concepts: green chemistry and valorization of agrowaste in a full zero-waste process, for addressing pollution and neglected tropical disease issues.