REUSE OF AGRICULTURAL WASTE TO ADSORB IRON CONTENT IN ACID MINE WATER

The adsorption process is the most desirable process in the treatment of waste containing heavy metals of acid mine drainage because it is economical, efficient, effective, and inexpensive. The adsorbent that is generally used is an activated carbon made from materials containing carbon, such as agricultural waste, namely lemongrass waste (Cymbopogon S.P), langsat fruit peel (Lansium domesticum cortex) and coconut shell (Cocos nucifera L.). The activated carbon using H3PO4 displayed more pore formation, larger, and cleaner than activated carbon with NH4OH. The best activated carbon in absorbing Fe³⁺ metal in acid mine water was at a mass of 4 grams with a percent removal. The equation used in the adsorption process was the Langmuir and Freundlich isotherm adsorption equation. The Langmuir isotherm equation obtained from maximum adsorption capacity of activated carbon langsat fruit peel was 38.89 mg/g with KL=76.69 mol/L and R²=0.9750 followed by 16.51 mg/g; KL=43.31 mol/L and R²=0.9069 for activated carbon lemongrass waste and 53.11 mg/g with KL=73.20 mol/L and R²=-0.9494 for activated carbon from coconut shell. Meanwhile, the Freundlich equation, KF value was 83.23 mol/L; R²=0.9512 on langsat peel activated carbon; KF=16.49 mol/L; R²=0.9042 on activated carbon of lemongrass waste, and KF=20.09 mol/L; R²=0.9162 on coconut shell activated carbon. Based on the data, the adsorption isotherm curve was more closely follows the Langmuir isotherm model with a linear regression coefficient that was relatively closer to 1 for the three types of adsorbents. This also indicates that the adsorption only takes place in one layer (monolayer).