ENHANCING MANGROVE BIOCHAR RESIDUE FOR PHOSPHATE ADSORPTION BY MODIFIED WITH Fe3+, K+, AND Na+

nutrients. Four types of biochar were used to adsorb phosphate (one unmodified biochar and
three modified biochars. This study’s objectives were (i) to compare phosphate adsorption
removal with different biochar modifications and (ii) to study the adsorption kinetic. 0.1 mol
L-1 of Fe3+, K+, and Na+ solutions with a volume of 500 mL were used to modified 20 g of
biochar. The batch experiment was conducted to investigate phosphate adsorption removal.
The result showed that unmodified biochar could not adsorb phosphate. However, biochar
modified with Fe3+ can remove phosphate than those of K+ and Na+. The equilibrium time of
300 min of BC-Fe3+, the phosphate removal efficiency was 48.50% ± 0.22. In addition, the
experiment was fitted with pseudo-first-order with an R2 value of 0.95 and giving adsorption
capacity (0.15 mg g-1) closed to the experiment value (0.12 mg g-1). The phosphate
adsorption followed reversible adsorption reactions. Furthermore, the Kd value increased
from 11.61-24.24 L kg-1, while increasing contact time from 5-360 min. This study suggested
that biochar modified with Fe3+ can use to remove phosphate from contaminated water or
reduce phosphate leaching from agriculture.