METHOD FOR REMEDIATION OF ACID MINE DRAINAGE USING CORN COB BIOCHAR WITH DOUBLE THERMAL ACTIVATION

Abstract

A method for remediating acid mine drainage using corn cob biochar with double thermal activation, characterized in that it comprises the following steps: step 1. crushing corn cobs to obtain a particle size between 1.5 and 2.5 mm; washing with distilled water; drying in an oven between 100 °C and 110 °C for 20 to 24 hours; and sieving to obtain the corn cob precursor with a particle size between 1 and 5 mm; step 2. the sieved precursor is subjected to pyrolysis between 370 °C and 420 °C, obtaining a biochar; step 3. the obtained biochar is subjected to chemical activation with ferric chloride (FeCl₂) in a mass ratio of 1:1 (biochar:FeCl₂) for a time of up to 12 hours; Step 4. Wash the activated biochar with distilled water and dry in an oven between 100 °C and 110 °C until all residual moisture is removed; Step 5. Subject the material from step 4 to secondary thermal activation between 470 °C and 520 °C under an inert atmosphere and cool; Step 6.The process involves contacting 3-6 g / L of activated biochar from step 5 with the acid mine drainage for 7-12 minutes and separating the solid from the liquid. In step 7, the resulting effluent is pH-adjusted to between 6.0 and 7.0 and contacted with 1-3 g / L of synthetic zeolite for 20-40 minutes. The invention achieves simultaneous and efficient removal of sulfates and heavy metals with rapid kinetics (less than 60 minutes), low material dosage, and industrial scalability.