Exploring the inhibitory performance of expired moxifloxacin and norfloxacin on copper corrosion in saline environment

The reuse of expired drugs has become a challenge to maintain environmental clean-liness and achieve economic benefit. In this report, two expired drugs, moxifloxacin and norfloxacin, were used as inhibitors for copper corrosion in 3.5 % NaCl solution at different temperatures using several experimental approaches including chemical, electrochemical and spectroscopic techniques. The interaction of these two molecules on the copper surface was also inspected using different adsorption models. Using a dose of 500 mg L-1 of these drugs at 298 K, maximum inhibition efficiencies (IE) of 88.7 and 85.2 % were estimated from the potentiodynamic polarization technique for Mox and Nor, respectively., confirming that they can be considered as promising and effective inhibitors. The IE values were enhanced with increasing drugs doses and reduced with rising temperature. The higher IE is due to the strong adsorption of these molecules on the copper surface and such adsorption is physical in nature and follows the Langmuir adsorption isotherm. This is due to their unique chemical structures as they contain a number of functional groups. Polarization experiments confirmed that the drugs were tuned to behave as mixed-type inhibitors with an anodic predominance. All thermos¬dynamic and kinetic parameters were calculated and discussed in details, and the inhibition mechanism is proposed. All experimental results obtained by different techniques were in agreement with each other.