Eco-friendly lily bulb-derived polysaccharide aerogel for efficient microplastics and nanoplastics removal

Microplastics that eventually convert into nanoplastics are emerging global pollutants and the development of efficient adsorbents for their removal is urgently needed. For sustainability and eco-friendliness, in the current study, a polysaccharide aerogel (LPA) was prepared with lily bulbs as the raw material by following water bath extraction, purification and freeze-drying processes. The prepared porous LPA was then applied as a packing material in a mini adsorption column for removing polystyrene (PS) microplastics and nanoplastics. Results revealed that LPA was over 90 kDa in size and consisted mainly of glucomannan and the removal efficiencies for microplastics and nanoplastics were 93.68 % and 96.98 %, respectively, mainly due to hydrogen bonding interactions and porous structure. The adsorption column was robust and maintained a remarkable removal efficiency (over 90 %) for 3 months. In addition, the effects of other extraction methods and pre-freezing conditions before the freeze-drying process were studied. Compared with water bath extraction, ultrasonic-assisted extraction and microwave-assisted extraction transformed the LPA structure, resulting in reduced adsorption ability, while the pre-freezing temperature could be used to adjust the specific surface area. Meanwhile, the effects of temperature and pH of adsorbates were also investigated. The LPA was heat sensitive and not stable under strongly acidic (pH 4) or strongly alkaline (pH 10) conditions, resulting in a sharp decline in removal efficiency. The adsorption behaviour of LPA was further described via adsorption kinetic models, showing that the microplastics and nanoplastics adsorptions could be fitted by pseudo-second-order and pseudo-first-order models, respectively. Moreover, the adsorption performance of LPA was compared with some other aerogels and had a better result. This research provides a promising, sustainable alternative for microplastic and nanoplastic removal that has potential for pollutant adsorption and sample purification as well as a low preparation cost.