The work gives the details about the influence of (Dy) substitution in the Lanthanum ferrite (x = 1mol%, 3mol%, 5mol%, 7mol%) nanoparticles prepared by biofuel mediated combustion method. The studies of PXRD, SEM, UV-DRS, FTIR, TEM were carried out to understand the structural characteristics. The PXRD shows the high crystalline peak of lanthanum ferrites. From Rietveld refinement analysis confirms orthorhombic structure. The estimated crystal size is 31-43nm. The band gap from UV -DRS studies was in the 2.4-2.8eV range. The morphological studies SEM and TEM shows the agglomerated structure. The variation of peak intensity (PXRD), the band gap and the force constant calculated from FTIR confirms the presence of dopant in the host disturbed the crystal lattice. The Photocatalytic degradation for the Eosin Y dye were done under visible light. The 3mol% Dy doped Lanthanum ferrite shows enhanced results of about 85.09% in 60minutes. The crystallinity nature from XRD and band gap of about 2.4eV could more most supportive parameters for the nanomaterial for photodegradation. The antibacterial activities for E.coli and P. aeruginosa shown effective activity, which could make the sample to be more applicable towards biomedical field.