Studies On The Removal Of Olaquindox And Its Interaction Mechanism With Protein

Feed additive olaquindox （OLA） has many toxicities and can pose a great threat tohuman health and the environment. Research on the removal of OLA can provideuseful information for solving the environmental problems caused by OLA, which isof great theoretical and practical significance. Studies on the interaction of OLA withserum albumin can provide a theoretical basis for appropriately understanding itseffect on protein function during the blood transportation process and its toxicologicalaction in vivo. The results of this paper are of great guiding significance to OLApollution prevention and controlling the safe application of OLA as feed additive.In this paper, multi-walled carbon nanotubes （MWCNT） were employed for thesorption of OLA from aqueous solution. A detailed study of the adsorption processwas performed by varying pH, ionic strength, sorbent amount, sorption time andsystem temperature. The surface/interface properties of MWCNT before and afteradsorption were characterized by physical and chemical methods, indicating that theadsorption mechanism is probably the non-electrostatic Ï€-Ï€ dispersion interaction andhydrophobic interaction between OLA and MWCNT. The adsorption efficiency couldreach99.7%, suggesting that MWCNT is an excellent adsorbent for effective OLAremoval from water. OLA adsorption kinetics were found to be very fast andequilibrium was reached within2.0min following the pseudo-second-order modelwith observed rate constants （k2） of0.169¹.048g·mg^-1·min^-1（293³33K）. Theoverall rate process appeared to be influenced by both external mass transfer andintraparticle diffusion, but mainly governed by intraparticle diffusion. A rapid initialadsorption behavior occurred within a short period of time in this adsorption system.The sorption data could be well interpreted by the Langmuir model with themaximum adsorption capacity of133.156mg·g1（293K） of OLA on MWCNT. Themean energy of adsorption was calculated to be0.124kJ·mol^-1（293K） from theDubinin–Radushkevich adsorption isotherm, suggesting that the adsorption is aphysical process. Moreover, the thermodynamic parameters showed the spontaneous and exothermic nature of the adsorption process. The results obtained in this worksuggest that MWCNT has a potential application as adsorbent media for removingOLA from water.The interaction between OLA and bovine serum albumin （BSA） was investigatedusing fluorescence, UV-vis absorption and circular dichroism （CD） spectroscopy. Theresults showed that the fluorescence quenching of BSA by OLA was a staticquenching process induced by the formation of OLA–BSA complex. The bindingconstant of OLA–BSA complex was calculated to be1.299×10⁴L·mol1（293K）.The negative values of H0and S0indicated that hydrogen bond and van der Waalsinteractions played major roles in stabilizing the complex. Site probe competitionexperiments and the number of binding sites （n） revealed that OLA could bind to siteI in subdomain IIA of BSA, and the binding distance （r） was evaluated to be3.643nm according to F rster’s non-radiative energy transfer theory. The results of CDand three-dimensional fluorescence spectra suggested some conformational changesof BSA after OLA binding.