Characterization and evaluation of surface modified materials based on porous biochar and its adsorption properties for 2,4-dichlorophenoxyacetic acid.

In this study, the effect of surface modification on the properties of porous biochar was studied, and these modification techniques were synthetically evaluated by principal component analysis. The results showed that surface modification significantly affected the surface and adsorption properties of porous biochar. Potassium carbonate activated porous biochar (KBC) was modified by surface oxidation, surface amination, loading nano-zero valent iron (nZVI) and loading nano-iron oxyhydroxide (nHIO). The surface modification affected the pore structure, especially the micropores. Surface modification influenced the oxygen-containing functional groups, amino, and metal-O significantly. It also changed the diffusion of 2,4-dichlorophenoxyacetic acid (2,4-D) on the biochar surface. The specific surface area was not the only factor determining the adsorption capacity. Surfaces rich in oxygen-containing functional groups would favor the adsorption of 2,4-D by biochar. The adsorption of biochars on 2,4-D were determined by π-π interaction, chemisorption and hydrogen bonding. The synthetic properties of modified biochar were evaluated by principal component analysis, and the comprehensive performance was in order of NKBC > OKBC > KBC > BC > nHIO@KBC > nZVI@KBC. Structural activation, surface amination and surface oxidation can improve the comprehensive properties of biochar.