Lignin-inspired porous polymer networks as high-performance adsorbents for the efficient removal of malachite green dye

Abstract

Herein, a series of porous polymer networks (LPPNs) were prepared from sustainable lignin-derivatized aldehyde monomers. It was interesting to discover that the 4-hydroxy benzaldehyde (H type) was favorable to promote the formation of the porous network LPPN-H with the largest BET surface area (739.4 m2/g) and pore volume (1.78 cm3/g) over that of LPPN-G (G type) and LPPN-S (S type), emphasizing the various geometrical shapes of building blocks significantly affected the porosity properties. The porous networks and abundant functional groups of LPPNs enabled efficient and rapid adsorption of malachite green (MG) dye. Strongly depending on the porosity parameters, LPPN-H gave a higher adsorption capacity for MG (Qmax = 1449.8 mg/g) than LPPN-G and LPPN-S, which exceeded many other reported adsorbents. The adsorption process could be well described by the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. Study in adsorption mechanism demonstrated that the electrostatic force, hydrogen bonding, and π-π stacking interactions existed in MG adsorption onto LPPNs. Besides, LPPN-H exhibited high stability and retained over 90% removal efficiency after 10 cycles. Together with the excellent adsorption behaviors and unique porosity properties, the low-cost and green LPPNs exhibited promising utilization in wastewater purification.