Hydrothermal Activation of Sugarcane Mill Mud and its Increased Imidacloprid Adsorption Capability

The Australian sugar industry produces 4 million tonnes of sugar products from 30 million tonnes of sugarcane annually producing a large amount of wastes. Sugarcane mill mud, one of the wastes from sugar mills, was hydrothermally activated at 250 C for 4 hours to produce an economically feasible adsorbent to demonstrate as a pesticide adsorbent. The hydrothermally activated mill mud displayed distinct chemical and physical changes as well as modified surface characteristics, as determined by electron microscopy characterisation and X-ray photoelectron spectroscopy. The hydrothermal activation process changed the physical composition from agglomerated multi-layered structures to distinctive structures possessing mono-layered features. The maximum adsorption capacities for organic molecules, as characterised by using the methylene blue dye assay, showed at least a 3-fold increase after activation. The adsorption process for the hydrothermally activated displays a mono-layer adsorption profile whilst the untreated mill mud sample affords multi-layer adsorption, observations that are consistent with their respective physical structures. Of interest, the absorptivity of the activated material was tested against Imidacloprid, a common pesticide used widely in sugarcane farms, to assess its viability as a pesticide adsorbent. The adsorption capacity was comparable to the reference activated carbon and much higher than commercially available coconut derived activated carbon, demonstrating its potential application as a runoff barrier for sugarcane farms.