Physicochemical modification of corn straw biochar to improve performance and its application of constructed wetland substrate to treat city tail water.

Corn straw is rich in resources, and the preparation of biochar as the constructed wetland (CW) substrate is an effective measure to realize high-value resource utilization. The objective of this paper was to improve the treatment effect of CW on city tail water, the freeze-thaw cycles (FTCs) modification and chemical modification (KMnO, NaOH and HSO) of straw biochar and the utilization of modified straw biochar in CW were studied. The modification characteristics of straw biochar were discussed through scanning electron microscope, element determination, pore structure determination, X-ray diffraction analysis, Fourier transform infrared reflection analysis, CO adsorption and desorption experiment and application experiment of CW (no plants and plants). The results show that under the influence of strong oxidation of KMnO, the combination of KMnO and FTCs modification is easy to cause the destruction of biochar structure, and the content of carbon element is reduced. Except for the combined modification of NaOH and FTCs, other composite modifications have little effect on the crystal structure and functional groups of straw biochar. The adsorption capacity of CO by FTCs modified biochar increased by 20.4%, and the adsorption capacity of CO by HSO and FTCs composite modified biochar increased by 23.0%. The effect of HSO modification of straw biochar based on FTCs modification is obviously better than that of NaOH and KMnO. The research results are of great significance to improve the material structure of biochar and the purification effect of CW on city tail water.