title: Studies on adsorption, reaction mechanisms and kinetics for photocatalytic degradation of CHD, a pharmaceutical waste.
abstract: The photocatalytic degradation of chlorhexidine digluconate (CHD), a disinfectant and topical antiseptic and adsorption of CHD catalyst surface in dark condition has been studied. Moreover, the value of kinetic parameters has been measured and the effect of adsorption on photocatalysis has been investigated here. Substantial removal was observed during the photocatalysis process, whereas 40% removal was possible through the adsorption route on TiO2 surface. The parametric variation has shown that alkaline pH, ambient temperature, low initial substrate concentration, high TiO2 loading were favourable, though at a certain concentration of TiO2 loading, photocatalytic degradation efficiency was found to be maximum. The adsorption study has shown good confirmation with Langmuir isotherm and during the reaction at initial stage, it followed pseudo-first-order reaction, after that Langmuir Hinshelwood model was found to be appropriate in describing the system. The present study also confirmed that there is a significant effect of adsorption on photocatalytic degradation. The possible mechanism for adsorption and photocatalysis has been shown here and process controlling step has been identified. The influences of pH and temperature have been explained with the help of surface charge distribution of reacting particles and thermodynamic point of view respectively.
authors.affiliation: Environmental Research Group, R&D, Tata Steel Ltd., Jamshedpur, 831001, India.
authors.forename: Santanu
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Chemical Engineering Department, Jadavpur University, Kolkata 700032, India. Electronic address: cbhattacharyya@chemical.jdvu.ac.in.
authors.forename: Chiranjib
authors.initials: C
authors.lastname: Bhattacharjee
authors.affiliation: Department of Informatics, Modeling, Electronics and Systems Engineering (D.I.M.E.S.), University of Calabria, Via-P. Bucci, Cubo 42a, 87036 Rende (CS), Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Curcio
mesh_terms: D000327:Adsorption; D000891:Anti-Infective Agents, Local / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects; D002384:Catalysis; D002710:Chlorhexidine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D053758:Nanoparticles / Q000737:chemistry*; D055668:Photochemical Processes; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D000891:Anti-Infective Agents, Local; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; C010882:chlorhexidine gluconate; D002710:Chlorhexidine
keywords: Adsorption; Langmuir Hinshelwood kinetics; Langmuir isotherm; Photocatalysis; TiO(2) nanoparticle