Adsorption of anionic and cationic dyes on biochars, produced by hydrothermal carbonization of waste biomass: Effect of surface functionalization and ionic strength

In this work, surface-functionalization agents and various salts as auxiliaries were used to improve the adsorption capacity of biochars produced via hydrothermal carbonization of glucose, cellulose, and hazelnut shell. The effect of surface functionalization with different acids and bases as well as neutral salts on the adsorption of methylene blue and methyl orange was investigated using Boehm titration, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy techniques. Surface functionalization of biochars leads to an increase in the number of oxygen-containing functional groups on the surface, thus increasing the adsorption capacity.