The influence of mechanochemical effects on chemical properties of antibiotic bioferment residue (ABR) during the comminution process was studied. The solid-state C-13 nuclear magnetic resonance (NMR) and electron spin resonance (ESR) techniques were used to study the carbon structures and free radical characteristics of ultrafine ABR Results showed that with the decrease of particle sizes, the net-like macromolecular aliphatic structures were cracked into numerous short-chain aliphatic carbons, leading to the increase of methylene and methine groups. The side chains of methoxy and oxygen-bonded methine groups initiated the bond cleavage and turned into oxygen-bonded methylene groups. In addition, the degree of aromatization of ABR increased during the grinding process due to the generation of more aromatic structures and the condensation among the aromatic rings. ESR spectra of ABR were the sum of several absorption lines caused different paramagnetic centers, which could be fitted by two Gaussian curves and one Lorenz curve. The effects of particle sizes on g-values, radical concentrations, and linewidths were analyzed. Results indicated that during the ultrafine pulverizing process, mechanical forces induced the cleavage of chemical bonds because of the severe collisions between the ABR particles, thereby producing more free radicals. The concentration of free radicals rose from 1.891 x 10(18) to 2.255 x 10(18) spin/g. In addition, more reactive sites generated with the increase of the free radicals in ABR, which was conducive to the chemical adsorption of NOx and its reduction into N-2 in combustion reactions. (C) 2017 Elsevier B.V. All rights reserved.