Multilayer nanoplastics capture using functionalized porous biochar nanoparticles obtained with low temperature: Interfacial binding forces enhancement mechanisms by humic acids decoration

Nanoplastics, which ubiquitously present in wide variety of water bodies, pose a serious threat to human health due to nanoscale size, toxicity, and persistence. Therefore, it is urgently necessary to develop appropriate adsorbents with features of strong capability of nanoplastics capturing and easy separation. In this regard, through decorating biodegradable and functional groups rich humic acids on porous magnetic biochar nanoparticles that prepared at lower pyrolysis temperature (400℃), the environmental friendly adsorbent (HAs/γ-Fe 2 O 3 /PNBC) was prepared. It was revealed that 100 mg/L of high concentration leveled nanoplastics with amino modification were near completely removed in 2 h, and the maximum capture capacities reached 1633.99 – 2105.26 mg/g at 10, 25 and 40 ℃, which was significant improvement compared to current researches. Also superior adsorption efficiencies were maintained at varying pH and ionic strength conditions. By mechanism study the attachment between HAs/γ-Fe 2 O 3 /PNBC and nanoplastics was revealed to be driven by electrostatic interaction, hydrogen bond, π–π interaction and complexation. Furthermore, the adequate binding sites and highly negative charging provided by rich humic acids which attaching on porous interface of nano biochar synergistically realized multilayer sorption. Overall, an extraordinary effective, environmental friendly and cost effective adsorbent was facially created using easy accessible natural materials, which has pronounced potential to decontaminate large scaled nanoplastics polluted water bodies.