In this research, an Ag2CrO4/Ag/Fe3O4/RGO nanocomposite (AAFR-NCPs) with unique properties was synthesized. The structural and morphological properties of the AAFR-NCPs were characterized by the FT-IR, XRD, FESEM, EDS, DLS, BET, and VSM techniques. The XRD analysis showed an average crystallite size of 7 nm. The FESEM images showed that the synthesized AAFR-NCPs possessed a spherical shape and average particle size of 48.5 nm. The DLS results and pHzpc measurement analysis indicated that the surface charge and zero-point charge pH of AAFR-NCPs were at − 29.8 mV, and 7.35, respectively. According to the BET results, the average surface area and pore diameter size distribution of the synthesized composite were 73.64 m2/g and 5.86 nm respectively. The corresponding total pore volume of the nanocomposite was 0.2574 cm3/g, which is in good agreement with the estimated results from the BJH method (0.2682 cm3/g). In addition, the VSM results showed that AAFR-NCPs had significant magnetization properties, equal to 41.6 emu/g, which is comparable with the magnetization level of pure Fe3O4 (50.05 emu/g). Moreover, the band gap energy (Eg) of the prepared AAFRNCPs is estimated to be 1.62 eV. The photocatalytic activity and optimization of the methylene blue (MB) photodegradation process using the synthesized AAFR-NCPs were investigated by the Box Behnken design and by Design Expert software. In this regard, a limited number of influential variables were studied, including the concentration of MB, amount of AAFR-NCPs as the photocatalysts (Cat), pH, and irradiation time (t). A polynomial equation was obtained corresponding to the degradation efficiency (DE) for the experimental data. The calculated R2, Adj-R2, and Pred-R2 values in the model were 0.991, 0.981, and 0.952, respectively indicating a reasonable proportion between the model fitting and experimental data. DE of 97.6 was achieved under optimum conditions of [MB]o = 12 mg/L, [Cat] = 10 mg/L, pH = 2 and ~103 min time of
