Dual-Modified Lignin-Assembled Multilayer Microsphere with Excellent Pb2+ Capture

Abstract

With the continuous research on lignin-based sorbents, there are still limitations in the research of spherical sorbents with a high adsorption capacity for Pb2+. 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 m2/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 Pb2+ ascribed by the electrostatic attraction and surface complexation; the adsorption capacity was 250 mg/g. The LMM showed a selective adsorption performance for Pb2+ and the adsorption capacity followed the order Pb2+ (187.4 mg/g) > Cu2+(168.0 mg/g) > Mn2+(166.5 mg/g). After three cycles, the removal efficiency of Pb2+ by the LMM was 69.34%, indicating the reproducibility of LMM.

Synthesis and Characterization of Thermally Stable Lignosulfonamides

“…The presently explored directions of development of the applicability of technical lignins, whether in the form of hydrogels or other forms, mainly focus on four fields of potential utilization: biomedical, agriculture, environment, and electronics [ 50 ]. This year only, researchers have described the application of lignosulfonates and other technical lignins to obtain high-efficien absorbents for the removal of Au(III) [ 51 ], Cr(VI) [ 52 ], Cu(II) [ 53 ], Co(II) [ 54 ], or Pb(II) [ 55 ] ions, amine-functionalized lignins [ 56 ] and magnetic lignosulfonate-based adsorbents for the selective removal of dyes [ 57 ] and other wastewater contaminants [ 58 ], just to name a few. Recent studies are not limited only to sorbents—lignin is a versatile starting material, which can be used to create hydrogels for capacitor and sensor applications [ 59 , 60 ], efficient photoinitiators [ 61 ], or can become a cross-linker for bioprosthetic materials of heart valves [ 62 ].…”