Montmorillonite K10 (MMT K10) supported copper oxide nanoparticles (CuONPs) were synthesized by incorporating CuONPs onto the surface of MMT K10 by reducing the metal precursor with the help of hydrazine hydrate. Effects of various factors on the efficiency of composite to remove hexavalent chromium were studied to find out the optimum conditions for maximum removal. Under optimum conditions 15 mg of the synthesized nanocomposite was found capable to almost completely remove (99.9 %) hexavalent chromium in 30 min from a 10 ppm aqueous chromium solution and that too in a wide range of pH from 2.88 to 5.56. The synthesized MMT K10 supported CuONPs were characterized by UV, SEM-EDX, FTIR and XRD studies. The average particle size of supported CuONPs was found to be 22.9 nm. Antibacterial potential of the prepared composite was also studied for one Gram-positive bacterium Staphylococcus aureus (ATCC 25323) and one Gram-negative bacterium Pseudomonas aeruginosa (ATCC 27853). The prepared nanocomposite was found to have excellent bactericidal potential and its statistical analysis was performed using t-test which indicates both bacterial strains of Pseudomonas aeruginosa and Staphylococcus aureus show different zone of inhibition for different concentrations.