Effect of the reaction medium on the immobilization of nutrients in hydrochars obtained using sugarcane industry residues.

In this study, nutrients were immobilized on the hydrochars obtained by hydrothermal carbonization (HTC) of a vinasse and sugarcane bagasse mixture, in the presence of acid, base and salt additives at temperatures of 150, 190 and 230°C. The increase in temperature caused higher immobilization of Ca, Mg, K, N, Cu, Mn, Zn, B, P and Fe in all hydrochars produced. HPO and NaOH immobilized higher amounts of P, Mg and Mn, while Ca was immobilized in higher quantities in the presence of HPO and (NH)SO. The addition of HSO, HPO and (NH)SO was responsible for an increased immobilization of P, N, Ca, Mg and K. The immobilization of B, not present in the starting raw material, was possible with the addition of HBO. The results showed that it is possible to alter the reaction medium to immobilize nutrients on hydrochars produced from vinasse and sugarcane bagasse, for agricultural applications.