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

Abstract

Silica nanoparticles (SiO2NPs) 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 SiO2NPs from SWA. The SiO2NPs 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 SiO2 content was 88.68 and 99.08 wt % for SWA and SiO2NPs, respectively. TEM images of SWA and SiO2NPs exhibit drastic alterations of the material size ranging from several micrometers to less than 20 nm. The SiO2NPs showed a specific surface area of 131 m2 g–1 and adsorption capacity of around 230 mg g–1 for acid orange 8 dye. Furthermore, the recycling of the SiO2NPs 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.

An Alternative and Simple Method for the Preparation of Bare Silica Nanoparticles Using Sugarcane Waste Ash, an Abundant and Despised Residue in the Brazilian Industry

“…12 Figure 1 shows the XRD diffractograms of the SiO 2 NPs obtained with different ratios of ash:NaOH. Different from sugarcane waste ash which only presents crystalline silica that is mainly assigned to peaks present in the quartz form, 12,15 ( Figure S3, SI section), the diffractograms of silica nanoparticles for the synthesized samples indicate the presence of amorphous silica only which is characterized by the presence of a broad single peak, reaching its maximum at 22° (2θ), corroborating with examples in the literature. 13,14,16,28 The absence of crystalline peaks in the structure does not allow the Scherrer equation to be utilized for the calculation of the crystallite size.…”

“…Several studies demonstrate how these properties can be controlled, aiming to remediate different types of contaminants with relative success. [9][10][11] Sugarcane waste ash can be utilized to generate silica nanoparticles (SiO 2 NPs) in the presence of cetyltrimethylammonium bromide (CTAB), 12 as previously demonstrated by our group; however, in this article the synthesis of bare silica nanoparticles without the presence of stabilizers is described. Nanoparticles without stabilizers have more applications due to the fact that they can be modified as needed, avoiding the problems generated by previously modified molecules, since removing molecules from the surface of nanoparticles in general, can cause destabilization or incompletion.…”

“…The synthetic procedure described in this manuscript is, in part, based on previous publications where all characterizations of sugarcane waste ash were reported. 12,15 In this article the procedure utilized to obtain bare silica nanoparticles and the properties of these nanoparticles are presented.…”

“…The Brunauer-Emmett-Teller (BET) analysis and the textural properties are reported in Figure 6 and Table 3, respectively. The textural properties of the sugarcane waste ash has already been reported in a previous article, 12 thus only the results of the SiO 2 NPs are presented. The SiO 2 NPs (1:1.5) sample isotherm can be classified as Type IIb, 33 which is associated with aggregates of plate-like particles with non-rigid, slit-shaped pores, resulting in large pore size distribution.…”

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“…Nowadays the most promising technique for treating wastewater is adsorption process (i.e adsorbents agro-industrial) (Rovani et al 2018). Porous SiO 2 produced from commercial silicon has also been applied as green adsorbents (Nabil and Motaweh 2019).…”