Palygorskite-based self-separable nano-adsorbent for wastewater treatment

Palygorskite (Pal) had been widely investigated as adsorbent, owing to its plentiful tunnels in crystals and channels on surface. But the two main challenges restricted its practical application: inconvenient separation and reuse. Here, Pal-based self-separable nano-adsorbent was developed via the surface olefin cross-metathesis (OCM) of nitrile butadiene rubber (NBR) from the methacryloxypropyl-modified Pal nanorods (M-Pal). The P -Pal microgels as small covalent aggregates with higher Pal content, could be easily dispersed into water, and interestingly, settled down completely within 6 min after adsorption of methylene blue (MB) with capacity of 33.0 mg g-1, slightly higher than the pristine Pal nanorods. The adsorbed MB could be completely desorbed by twenty times of desorption with 1.0 M HCl/ethanol. However, the desorption in repeated use was controlled by the adsorption/desorption equilibrium of MB in the tunnels of Pal nanorods, maintaining adsorption capacity of about 3.0 mg g-1 and 4.6 mg g-1 for reuse with ethanol or 1.0 M HCl/ethanol as eluent.