Rice straw is one of the most common agricultural wastes due to its large production amounts. Energy valorization of rice straw is a technology used for nitrate removal as the produced ashes used to generate the adsorbent by means of an alkali dissolution followed by acid precipitation. The novelty of the proposed process is that the production of the nano zero-valent iron supported acid-activated rice straw (AARS-nZVI) adsorbent is carried out without the energy valorization process but, through an acid activation for rice straw followed by precipitation of nZVI particles on its surface. The new adsorbent synthesis, characterization and application were studied. Initial solution pH, initial nitrate concentration, adsorbent dose and contact time factors were considered during the investigation of nitrate removal efficiency using Central Composite Design (CCD) method. The optimum nitrate removal 91.62 % is obtained at initial pH of 7, initial nitrate concentration of 6 mg/L, adsorbent dose of 3 g/L and contact time of 180 min by using numerical optimization.