efficiency of the photo fenton process for decolorization of direct red 81 dye from the aqueous solution

background textile dyes are the largest organic compounds associated with some problems for the environment. advanced oxidation process is the most effective method for dye removal from wastewater. objectives the aim of this study was to investigate the efficiency of the photo fenton process for decolorization of direct red 81 (dr 81) dye, and to determine the optimal process conditions. methods this is a cross-sectional study conducted on a laboratory scale. the effective parameters in the photo fenton process include ph, ferrous sulfate heptahydrate concentration, hydrogen peroxide concentration, initial dye concentration and reaction time. these parameters were studied, and finally analyzed using the excel software. results according to the obtained results, maximum removal efficiency was 98.1% at ph = 3, concentration of fe (ii) was 10 mg/l, hydrogen peroxide concentration was 50 mg/l, initial concentration of dye was 100 mg/l, and reaction time was 120 minutes. results showed that increasing the concentration of fe (ii), h2o2 and the initial concentration of dye to a certain extent resulted in increasing removal efficiency, then by increasing the concentrations of these parameters, removal efficiency decreased. results also indicated that increasing a reaction time resulted in increasing removal efficiency. conclusions the photo fenton method with optimized parameters can be used to conduct high efficiency dye removal in a short period of time and this process is based on hydroxyl radical formation.