Progress on the modification methods of bio-char for enhanced adsorption of pollutants from aqueous solution

The bio-char is one of the by-products from biomass pyrolysis, and it is a potential adsorbent for pollutants removal in aqueous solution.Through different modification methods, the physical/chemical properties of the bio-char could be changed.The adsorption capacity of pollutants would also be changed by the modification.Based on the analysis of the adsorption factors in aqueous solution, the enhanced absorption methods were proposed including heat treatment, reagent added for enlarge the pore volume, ultrasonic treatment, chemical modification and biological treatment.It was found that the surface oxygen functional groups of the bio-char played an important role in adsorption besides the pore structures.The surface acidity of the oxygen functional groups on bio-char would be increased after acid treatment.The adsorption capacity of metal ions would also be increased onto bio-char because of the cation exchange reaction.The delocalized π electron density would be increased by alkali treatment, which was helpful for phenolphthalein, dyes and other organic pollutants removal.The removal ability of organic and metal contaminants would be improved by the load atoms and compounds of bio-char.In addition, biological adsorption was found to be helpful for phenol removal.This paper provided effective ideas for the enhance adsorption of bio-char. © 2016, Chemical Industry Press Co., Ltd.. All rights reserved.