A novel mussel-inspired layered montmorillonite-based composite aerogel for high-efficiency removal of heavy metal ions

Polydopamine-modified montmorillonite/chitosan (PDA-mMMT/CS) aerogels were synthesized through the combination of combining natural biopolymers CS and PDA-modified MMT, followed by freeze-drying. PDA-mMMT/CS aerogels overcame the poor mechanical properties of mMMT/CS aerogels, had abundant functional groups, large specific surface area, good thermal stability at low temperatures, and realized the efficient adsorption Cu(II) and Pb(II) in aqueous solution. The porous structure of aerogels offers more adsorption sites, and PDA grafting on the mMMT surface provided abundant amino and catechol groups, significantly improving the adsorption capacity. At pH = 6, the maximum amount of Cu(II) and Pb(II) adsorbed was 475.61 and 534.76 mg·g−1, respectively. These values are superior to those reported for most MMT or CS-based adsorbents. PDA-mMMT/CS aerogel mainly adsorbs heavy metal ions through chelation adsorption and ion exchange. The adsorption process is unimolecular layer adsorption and chemisorption. PDA-mMMT/CS exhibited high selective adsorption for Cu(II) and Pb(II), and the adsorption efficiency was still >86 % after 5 cycles. This work presented a green and convenient synthesis strategy based on renewable, low-cost, and environmentally friendly mMMT and CS. •PDA-MMT/CS aerogel was synthesized by a viable green route using polydopamine-modified montmorillonite.•The adsorption capacities of PDA-MMT/CS aerogel for Cu(II) and Pb(II) were 475.61 and 534.76 mg·g−1, respectively.•The aerogel's three-dimensional laminar pores enable rapid and efficient transport of heavy metal ions.•The adsorption capacity of Cu(II) and Pb(II) ions could be maintained above 86 % after 5 cycles.•PDA-MMT/CS aerogel adsorption capacity is superior to that of similar adsorbents.