SUMMARY Fly ash is waste that produced from the burning process of palm oil shells and fiber in the engine of boiler. Fly ash contains of metal oxides such as SiO2, CaO, MgO and Al2O3 which have potential as the adsorbent. The aim of this study was to determine the optimal absorption time of methylene blue by fly ash from microwave irradiation and to characterize the fly ash before and after a…