Adsorption of deoxyribonucleic acid (DNA) by willow wood biochars produced at different pyrolysis temperatures

Adsorption of DNA by biochars was investigated in the present study. Biochars were produced from air-dried willow wood chips at 300, 400, 500, and 600 °C under limited oxygen supply. The resulting products, referred to as BC300, BC400, BC500, and BC600, respectively, were characterized for their elemental composition, cation exchange capacity (CEC), specific surface areas (SSA), and microporosity. According to a Langmuir isotherm, maximum DNA adsorption capacity of biochars was ranked as BC500 > BC600 > BC400 > BC300. Increasing solution pH (from 4.0 to 9.0) faintly decreased DNA adsorption onto biochars. The addition of Na⁺, Mg²⁺, and Ca²⁺ slightly increased the adsorption of DNA, and the effect decreased by increasing the pyrolysis temperature of biochars, indicating that electrostatic interaction was not the main driving force for DNA adsorption onto those biochars. Correlation analysis showed that SSA and micropore surface area were the main factors influencing DNA adsorption on biochars.