Preparation of Two Kinds of Biochar and the Factors Influencing Tetracycline Removal from Aqueous Solution

Abstract

In this research, Chinese medicine residue of Evodia lepta and corn stalks were chosen as raw materials to prepare biochar (EIBC and CSBC) at 400, 600, and 800℃, for the removal of tetracycline from solution. The biochar was characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effects of pyrolytic temperature, biochar dosages, initial concentration, adsorption time, solution pH, ionic strength, and ambient temperature on the removal of tetracycline from solutions by biochar were investigated. The adsorption behavior of tetracycline by biochar was investigated using adsorption kinetics and adsorption isotherms. The results showed that the adsorption capacity of biochar for tetracycline was elevated with increase in the pyrolysis temperature. The biochar prepared from Chinese medicine residue Evodia lepta at under 800℃ (EIBC800) had the best adsorption properties. Biochar dosages, solution pH, ionic strength, and adsorption time had significant effects on the adsorption of tetracycline by EIBC800 and CSBC800. In contrast, the effect of ambient temperature on tetracycline adsorption was a concentration-dependent process. The adsorption kinetics and isotherms of tetracycline onto EIBC800 and CSBC800 were all fitted to pseudo-second order models (R2 0.9540 and 0.8355) and to a Freundlich equation (R2 between 0.8991-0.9579 and 0.9736-0.9946), respectively. The adsorption process was mainly controlled by chemical reaction, and the tetracycline adsorption process was spontaneous and endothermic. Compared with the corn-stalk derived biochar, EIBC800 had better adsorption capacity for antibiotics than CSBC800 did, which indicated that Chinese medicine residue derived biochar had wider prospects for application in the treatment of wastewater containing antibiotic residues.