Valorisation of sugar cane bagasse using hydrothermal carbonisation in the preparation of magnetic carbon nanocomposite in a single‐step synthesis applied to chromium adsorption

Abstract

BACKGROUND Sugar cane bagasse (SB) is a by‐product of the sugar cane industry, and is obtained on a large scale. In this paper, SB was used as a source of carbon for preparing a magnetic carbon nanocomposite (MCN‐SB) through one‐step hydrothermal carbonisation (HTC), in the presence of iron (III) nitrate. By way of comparison, SB was replaced by glucose in HTC (MCN‐GLU), and a thermal treatment of this material was then performed under an N2 atmosphere (MCN‐GLU‐HT). The physical and chemical properties of the nanocomposites were assessed, and the magnetic samples were applied as adsorbents. RESULTS MCN‐SB and MCN‐GLU are composed of iron oxide nanoparticles embedded in carbonaceous matrix which also contain oxygenated groups. The MCN‐SB sample was already magnetic after HTC, showing a magnetization saturation (Ms) of 5.0 emu g−1, due to the presence of magnetite, whereas MCN‐GLU consisted of hematite and required additional thermal treatment (HT) to acquire magnetic properties, with MCN‐GLU‐HT showing an Ms of 30.5 emu g−1. In turn, the mesoporous structure and higher specific surface area (SSA) of MCN‐GLU‐HT (SSA 90 m2 g−1) than MCN‐SB (SSA 53 m2 g−1) was a causative factor for its higher capacity of hexavalent chromium [Cr (VI)] removal (939 μg g−1), when compared to MCN‐SB (768 μg g−1), which has a nonporous structure. CONCLUSION The results suggest that SB can be reused, by means of HTC, for the preparation of a magnetically recoverable adsorbent, showing good adsorption properties. © 2022 Society of Chemical Industry (SCI).

Development of a novel direct magnetic sorbent sampling device by flame furnace atomic absorption spectrometry (DMSS-FF-AAS) using a carbonaceous nanocomposite for highly sensitive determination of cadmium

“…It was observed as a red solid residue, suggesting hematite formation. 24,27 The thermal profiles were similar for both samples and presented two main distinct stages of weight loss: (i) removal of adsorbed water (30–150 °C) and (ii) combustion of the carbonaceous matrix (200–450 °C). Above 500 °C in TGA curves, the weight loss could be negligible.…”

“…It is important to point out that nanoparticles are encapsulated in the carbonaceous matrix. 24,27 This arrangement is of paramount importance to avoid the oxidation of iron oxide nanoparticles (magnetic phase) in the structure of the nanocomposite, apart from providing adsorption sites for the material. 28,29…”

“…The synthesis of Fe 3 O 4 @C was carried out in two steps: the hydrothermal carbonization method (HTC) followed by thermal treatment in a nitrogen flow using a tubular furnace. 24 Initially, to produce a nanocomposite with a nominal Fe/C ratio (w/w) of 11%, 0.90 g of glucose and 0.30 g of Fe(NO 3 ) 3 ·9H 2 O were added to 40.0 mL of ultrapure water, and the solution was ultrasonicated for 15 min. This solution (pH approximately 2.0) was transferred to a Teflon®-lined stainless steel autoclave (capacity of 60.0 mL) and heated up to 190 ± 10 °C for 9 h in a muffle furnace.…”