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Positively charged and non-toxic intermediate layers are highly desirable for the construction of nanofiltration membranes in the field of Mg2+/Li+ separation. Herein, we have prepared dual-electric layer nanofiltration membranes via introducing positively charged quaternized cellulose nanocrystals (Q-CNC) beyond the negatively charged polyamide skin layers. On the one hand, the strong interactions between Q-CNC and piperazine (PIP) could regulate the thickness, roughness, and residual groups of the polyamide (PA) layers, resulting in improved water flux. On the other hand, the Q-CNC has lots of positive charges which are beneficial for enhancing the rejections of negatively charged polyamide skin layers towards divalent cations since the Donnan and electrostatic effects are long-range forces. Moreover, this effect could be amplified by reducing the thickness of skin layers or decreasing the contents of residual carboxyl groups via adjusting the monomer concentrations. The obtained nanofiltration membranes possess high water flux of 51 L/m2/h/bar, and rejection for MgCl 2 of 86 %. The separation factor of Mg2+/Li+ is 29 when the Mg2+/Li+ mass ratio in the feed solution is 20:1. Moreover, the nanofiltration membrane with Q-CNC intermediate layers (QNFM) has good antibacterial properties, showing great potential in the fields of lithium extraction from salt lakes. [Display omitted] [ABSTRACT FROM AUTHOR]

The conventional skin sensor detection of human physiological signals can be an effective method for disease diagnosis and health monitoring, but the poor biocompatibility, low sensitivity and complex design largely limit their applications. Developing natural nanofiller-reinforced composites as strain biosensors is an appealing solution to reduce environmental impacts and overcome technical bottleneck. Herein, a versatile nature skin-inspired composite film as flexible strain biosensor was developed based on cellulose nanocrystals-polyaniline (CNC-PANI) composites by utilizing their percolated conductive network in polyvinyl alcohol (PVA) matrix. The composite electronic skin showed robust mechanical strength (50.62 MPa) and high sensitivity (Gauge Factor = 11.467) with easy water-induced self-healing abilities. Moreover, we investigated the functioning mechanism of percolated network and the sensory behavior determined by CNC nanocomposite alignment. The percolation threshold of CNC-polyaniline (PANI) was determined at 4.278% and 5% CNC-PANI composite film shows the best overall sensing property. It was also discovered that the sensitivity of this type of conductive-filler electronic skin can be divided into two separate regions at different strain range due to its percolated network. With films prepared by dry casting and dip coating, the alignment of CNC-PANI also contributes to this unique change in electrical property. Generally, our results demonstrated the mechanism and tunability of conductive nanofiller-based composite strain biosensors as a potential alternative to commercial synthetic sensors. • Conductive cellulose nanocrystals incorporated PVA composite strain biosensor were prepared. • The self-healed composite showed robust mechanical strength and excellent sensitivity. • Working mechanism of percolated network-based conductivity and sensitivity was reported. • Self-healing mechanism of PVA nanocomposite film was proposed. [ABSTRACT FROM AUTHOR]