Modified biochar activated by traditional Chinese medicine extract and its removal of tetracycline

Traditional Chinese medicine (TCM) has been widely used during the outbreak of Covid-19 in the past few years, causing waste of resources and environmental pollution. This paper will convert TCM into porous carbon-based materials through pyrolysis technology, and then combine it with TCM extract activator to synthesize a new type of adsorbent. The two main ingredients of Chinese patent medicine "Lianhua Qingwen Capsules", Honeysuckle and Forsythia suspensa, will be used as raw materials. After the two herbs are crushed, the leachate is extracted, and the remaining residue is collected. The dried residue is activated and carbonized at high temperature to generate biochar. Further, the biochar will be soaked in TCM extraction liquid to load active ingredients. The adsorption mechanism of tetracycline (TC) by TCM biochar was explored based on the adsorption kinetics and adsorption isotherm fitting results. The microstructure, surface functional groups and crystal structure of TCM biochar will reveal the material properties of the adsorbent. The results show that compared with biochar without extract activation, the adsorption effect of combined biochar (BC-C) with the proportion of "Lianhua Qingwen Capsules" is greatly improved. BC-C has richer surface functional groups through TCM extract loading, which provides superior TC adsorption capacity (36.92 mg/g). The adsorption process of TC by TCM biochar follows the pseudo-second-order adsorption kinetic model and Freundlich adsorption isotherm model. The adsorption mechanism mainly involves pore filling, hydrogen bonding, electrostatic interaction and π-π interaction.