In this work, the synthesis, characterization, and photocatalytic activity of iron-doped titanium dioxide nanoparticles (FDT) supported on environmentally benign activated carbon (PAC) has been discussed. The photocatalytic activity of the nanocomposite was investigated for the degradation of Congo red (CR) dye from aqueous solution under visible light (520 nm), and it was observed that 100% degradation for 20 ppm CR solution took place within 60 mins. The experimental data of photodegradation of CR using the FDT/PAC nanocomposite had the highest correlation with Langmuir Hinshelwood model and pseudo-first-order rate kinetics with an apparent rate constant of 0.05341min-1 and half-life period of 12.97mins, respectively. The thermodynamics study revealed that the degradation process is exothermic and spontaneous. The effect of interfering ions on the degradation of CR solution was also examined. The photocatalytic antibacterial activity of the nanocomposite was tested against two bacteria pathogens, Escherichia coli and Staphylococcus aureus, and it was found that for the concentration of 105 CFU ml-1, 100% photocatalytic inactivation was achieved for both Escherichia coli in 120mins and Staphylococcus aureus in 75 mins under visible light irradiation. The total electrical energy consumed and operating cost were measured and the total operating cost was 312.50, 236.74, and 166.67 INR (Indian rupee) for 20 ppm, 60 ppm, and 100 ppm CR dye removal using 0.06 g FDT/PAC nanocomposite, respectively.