Chiang Mai Journal of Science

     In this study, Salacca zalacca seed (SS) agricultural waste was employed as a material for the preparation of activated carbon. Salacca zalacca seed activated carbon (SSAC) was chemically activated using H₃PO₄ and used as an adsorbent for chromium (VI) adsorption. The effect of various experimental parameters such as activation temperature, impregnation ratio, and H₃PO₄ concentration (%) on adsorption capacity was determined using response surface methodology (RSM). The optimum condition prediction of these values from RSM alines well with experimental data; activation temperature (800 °C), impregnation ratio (3.50) and H₃PO₄ concentration (75 %). SSAC activated at the optimum condition were intensively characterized to understand the morphology, surface charge density, chemical compositon and textural property by using SEM, pH_pzc, FTIR, CHON analysis, and N₂ adsorption-desorption. Maximum chromium (VI) adsorption was 7.94 mg/g. Langmuir adsorption model was effectively fi tted to the equilibrium adsorption information. Furthermore, the pseudo- second-order kinetic model also explains the experimental data well. Overall, the results suggested that RSM could optimize the preparation conditions of Salacca zalacca seed biochar leading to enhance the adsorption capacity of Cr(VI) using Salacca zalacca seed activated carbon. Moreover, SSAC provides a great reuseablity upto 6^th cycles. This result ensures that SSAC has a great potentiality as a low-cost, high-value agricultural waste adsorbent for Cr(VI) removal.