Abstract: The effect of surface modification of mesoporous activated carbon by nitric acid and ammonia on its adsorption capacity to two kinds of agro-antibiotics—abamectin and validamycin was investigated.The results showed that mesoporous activated carbon modified by nitric acid increased the adsorption capacity to the hydrophilic,validamycin,while decreased the adsorption capacity to the hydrophobic,abamectin.This may be attributed to the increase of hydrophilic acidic groups of the surface after the modification.However,when the concentration of nitric acid increased to 55% and the temperature increased to 60 ℃,the strong oxidation of nitric acid might lead to the destruction of internal pore structure of activated carbon,and weakened the adsorption to valiadamycin.By contrast,the surface hydrophilic acidic groups were reduced after modification by ammonia,which leaded to the increased adsorption capacity to abamectin.SAS statistical analysis indicated that the amount of acidic groups,in particular,carboxyl had significant correlation with the adsorption of mesoporous activated carbon to abamectin and validamycin,and the correlation coefficient was 0.560 2 and -0.873 7 respectively.Therefore,it deduced that increasing surface acidic hydrophilic groups of mesoporous activated carbon would improve its adsorption to hydrophilic agro-antibiotics to some extent,while increasing surface hydrophobic groups of mesoporous activated carbon would improve its adsorption to hydrophobic agro-antibiotics.