Highly Pure Silica Nanoparticles with High Adsorption Capacity Obtained from Sugarcane Waste Ash

[Image: see text] Silica nanoparticles (SiO(2)NPs) from renewable sources can be used in very different materials, such as paints, membranes for fuel cells, Li-ion batteries, adsorbents, catalysts, and so on. Brazil is the world’s largest producer of sugarcane and generates huge amounts of sugarcane waste ash (SWA), which is a Si-rich source. This study investigates a method to produce highly pure SiO(2)NPs from SWA. The SiO(2)NPs were characterized by inductively coupled plasma optical emission spectroscopy, scanning and transmission electron microscopy (TEM), X-ray diffraction analyses, specific surface area and pore distribution, UV and Fourier transform infrared spectroscopy, and thermogravimetric analyses and applied as an adsorbent material in the removal of acid orange 8 (AO8) dye from aqueous solution. The SiO(2) content was 88.68 and 99.08 wt % for SWA and SiO(2)NPs, respectively. TEM images of SWA and SiO(2)NPs exhibit drastic alterations of the material size ranging from several micrometers to less than 20 nm. The SiO(2)NPs showed a specific surface area of 131 m(2) g(–1) and adsorption capacity of around 230 mg g(–1) for acid orange 8 dye. Furthermore, the recycling of the SiO(2)NPs adsorbent after AO8 adsorption was very satisfactory, with reuse for up to five cycles being possible. The results indicate that it was possible to obtain highly pure silica in a nanosize from the waste material and produce an adsorbent with high adsorption capacity and the possibility of reuse.