Dual-Modified Lignin-Assembled Multilayer Microsphere with Excellent Pb(2+) Capture

With the continuous research on lignin-based sorbents, there are still limitations in the research of spherical sorbents with a high adsorption capacity for Pb(2+). In order to solve the problem of low adsorption effect, alkali lignin (AL) was modified and assembled to increase the adsorption active sites. In this work, we used dual-modified lignin (DML) as a raw material to assemble a singular lignin-based multilayer microsphere (LMM) with sodium alginate (SA) and dopamine. The prepared adsorbent had various active functional groups and spherical structures; the specific surface area was 2.14 m(2)/g and the average pore size was 8.32 nm. The adsorption process followed the Freundlich isotherm and the second-order kinetic model. Therefore, the LMM adsorbed Pb(2+) ascribed by the electrostatic attraction and surface complexation; the adsorption capacity was 250 mg/g. The LMM showed a selective adsorption performance for Pb(2+) and the adsorption capacity followed the order Pb(2+) (187.4 mg/g) > Cu(2+)(168.0 mg/g) > Mn(2+)(166.5 mg/g). After three cycles, the removal efficiency of Pb(2+) by the LMM was 69.34%, indicating the reproducibility of LMM.