Conversion of coal residue into humic acids via catalytic oxidation

In order to utilize carbon resource efficiently and decrease waste discharge, a procedure of catalytic oxidation for turning coal residue into humic acids is developed in this work. Humic substances have effects of improving soil and promoting plant yield. The catalytic oxidation can convert 35% of coal residue into humic acids at room temperature by using dilute H ₂O ₂ solution as oxidizing reagent and CuO powder as catalyst. It is proved that the oxidatively formed humic acids are similar to the natural humic acids both in structural features and in elemental composition. After the oxidatively formed humic acids are separated, the CuO powder is mixed into the secondary residue. Thus the CuO powder could be repeatedly used as catalyst for oxidation of the secondary residue into humic acids.