Preparation of biochar based on self-polymerization of tannic acid and ammonia adsorption performance study

Ammonia becomes one of the indispensable raw materials in production and life, with the continuous development of industry. Ammonia pollution of the environment is becoming more and more serious, so the adsorption of ammonia is essential. In this paper, a new biochar material based on tannic acid was developed. The tannic acid was self-polymerized using different activators (K2CO3, KHCO3, KOH). Tannic acid biochar (TAB-X) was obtained by pyrolytic carbonization reaction at 800 degree celsius. The biochar was treated with phosphoric acid 10% by mass (TAB-X-10%PO4), and unlike other biochar materials, the specific surface area and hydroxyl content were increased after acidification, but there were no acidic functional groups. It is noteworthy that the specific surface area of TAB-KOH increased from 22 m2/g to 667 m2/g after acidification. The adsorption capacity of ammonia vapor reached 342.6 mg/g. It is proposed that the adsorption mechanism is an adsorption process in which hydroxyl groups on the surface of TAB-X firstly adsorb water, and after that ammonia gas is then dissolved in the water molecules on the surface of the biochar. These results highlight the great potential of TAB as an adsorbent for the adsorption of ammonia, in addition to the low price of raw materials and the simple preparation conditions of this preparation process, which corresponds with the conditions for mass production as well as practical application.