Coffee Silver Skin: A Useful Adsorbent Substrate for Norfloxacin Removal and Photodegradation

ThisworkproposestheuseofCoffeeSilverSkin,aby-productof coffeeproduction, as anadsorbent substrate for the removal of the antibiotic Norfloxacin fromwater andassesses thepossibilityof regenerating it through advancedoxidationprocesses. Indetail, thestudywasdevelopedbyshowingthe best conditions for the pollutant removal, inwhich the adsorption process occurredwiththemaininvolvementof electrostatic interactions.Apreliminary desorptionapproachinthepresenceofsalt-basedsolutions, i.e.,NaCland0.1M MgCl2, was followed with the aim of desorbing the non-photodegraded Norfloxacin from the regenerated adsorbent. Therefore, indirectly, the quantitative evaluationof photodestroyedNorfloxacinwas assessed according toselectedworkingconditions:UVlight,UVlight/H2O2,UVlight/TiO2, and UVlight/TiO2/H2O2.Moreover, a comparisonwith the literaturedevoted to Norfloxacinphotodegradationdirectlyinwaterwasaccomplished.TheuseofUV light/TiO2occurredasthebestapproachforthepurposeofobtainingthecompletedegradationofNorfloxacinin6h.Ontheother hand, theuseofH2O2didnot improvetheprocess.Thus, toreducethe irradiationtime,Norfloxacindegradationwasevaluated simultaneouslyduring its release fromtheadsorbent, ina0.1MMgCl2 solution, retrievinga similar andwell-knownbehavior observedwhenthepollutantwasdegradedinwater.In3h,thedesorbedNorfloxacinwasdestroyed,enablingtherecyclingofCoffee SilverSkinforupto3cycles.