Arundo donax biochar (ABC) is produced through pyrolysis with limited oxygen levels as green biochar (GBC) serves as the raw material. KOH, HCl, and H₃PO₄ were used as alkalin and acidic agents for surface modification. Adsorption experiments were conducted to investigate the impact of these surface modification methods on humic acid (HA) removal from aqua solution compared with ABC without surface modifications and commercially activated carbon. The adsorption experiments were conducted in a pH range from 5 to 9. The findings indicated that the removal of humic acid has been enhanced at lower pH for all cases at the same operation conditions. The HA removal efficiency was higher by CAC than ABC without modification. However, both acidic and alkaline surface modification had higher HA removal compared with CAC. The adsorption efficiency by various treatment reagents on HA was in the order  KOH > HCL > H₃PO₄. At a pH value of 5, HA removal efficiency was 97.56 %,  51.3 %, and 48.64 % for KOH, HCL, and H₃PO₄ respectively. The research indicated that biochar derived from Arundo donax represents a promising, cost-effective, sustainable, and environmentally friendly solution for HA removal from surface water, offering a novel perspective for practical implementation.