Adsorption of enrofloxacin on acid/alkali-modified corn stalk biochar

The levels of enrofloxacin have exceeded acceptable standards in the water environment of many global regions, and the problem of pollution caused by enrofloxacin needs to be solved urgently. In this study, phosphoric acid and potassium hydroxide were used to modify corn stalk biochar. The properties and structure of the modified biochar were studied by scanning electron microscopy, infrared spectrometer, X-ray diffraction spectroscopy, and other analytical methods. Other factors influencing enrofloxacin adsorption were assessed using the equilibrium adsorption method. The surface area of the acid- and alkali-modified biochar was found to increase 10- and 14-fold, respectively. The equilibrium adsorption capacity of enrofloxacin on the acid- and alkali-modified biomass carbon increased by 27.80% and 54.08%, respectively. The quasi-second-order kinetic equation and Langmuir equation described the adsorption process of the biochars accurately. At pH = 5.0, the biochars had the highest levels of enrofloxacin adsorption. The adsorption of enrofloxacin onto the biochars negatively correlated with the concentration of Ca2+ in the background solution.