Construction of Lanthanide Magnetic Bio-Based Porous Carbon Materials with Beam and Column Structure and Its Synergistic Adsorption Performance.

Abstract

Biochar porous carbon material (BPCM) has extraordinary adsorption properties and is being widely used in different fields around the world. The pore structure of BPCM is liable to collapse, and mechanical properties are inferior; hence, the focus is on developing a new ″powerful″ structure of functional BPCM. Rare earth elements with characteristic f orbitals are used as pore and wall strengthening units in this work. The new ″beam and column structure″ BPCM was synthesized by the aerothermal method, and then, the magnetic BPCM was prepared. The results showed that the designed synthesis route was reasonable, BPCM with a steady-state beam and column structure was attained, and the La element played a stabilizing role in maintaining the overall BPCM. The La hybridization exhibits the characteristic of ″the stronger column and weaker beam″, and the La group is the ″column″ to strengthen the BPCM as the ″beam″. The functionalized BPCM (lanthanum-loaded magnetic chitosan-based porous carbon materials, MCPCM@La2O2CO3) obtained exhibited a transcendent efficient adsorption capacity with an average adsorption rate of 6.640 mg·g-1·min-1 and over 85% removal of different types of dye pollutants, which exceeded the adsorption performance of the materials of most other BPCMs. Ultrastructural analysis revealed that MCPCM@La2O2CO3 has a huge specific surface area of 1458.513 m2·g-1 and a magnetization value of 16.560 emu·g-1 for MCPCM@La2O2CO3. A new theoretical model for the adsorption of MCPCM@La2O2CO3 (multiple adsorption coexistence equation) was established. The theoretical equations clarify that the mechanism of pollutant removal by MCPCM@La2O2CO3 is different from the traditional adsorption model, presenting a mechanism of coexistence of multiple adsorption types, displaying a monolayer-multilayer adsorption mechanism, influenced by the synergistic effects of H bonding, electrostatic attraction, π-π conjugation, and ligand interaction. The rapid coordination of the d orbitals of La is an obvious factor in enhancing the adsorption efficiency.