Humic acid can be used as an adsorbent with white jabon fruit powder (Anthocephalus cadamba Miq.) as the supporting solid. The adsorption ability of the biosorbent can be improved by NaOH activation process, which increases the active sites and enlarges the surface area of the biosorbent. This study aims to determine the optimal biosorbent dosage, pH, pHpzc and contact time for adsorbing Crysta…