Removal of lead, copper, cadmium, zinc, and nickel from aqueous solutions by alkali-modified biochar: Batch and column tests

Engineered biochar was obtained through slow pyrolysis of hickory wood and then further modified with NaOH. After modification, biochar's surface area, cation-exchange capacity, and thermal stability were significantly improved. The modified biochar exhibited much larger (2.6–5.8 times) metal adsorption capacities than the pristine biochar. Competitive batch adsorption of mixed metal ions (Pb2+, Cd2+, Cu2+, Zn2+, and Ni2+) showed preferential adsorption of Pb2+ and Cu2+ onto the modified biochar. The alkali-modified biochar in a fixed-bed column also showed strong ability to filter heavy metals from aqueous solutions. The alkali-modified biochar thus can serve as alternative absorbent for heavy metals.

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