title: Hexavalent chromium removal in contaminated water using reticulated chitosan micro/nanoparticles from seafood processing wastes.
abstract: Chitosan particles (CH) were obtained from seafood processing wastes (shrimp shells) and physicochemically characterized; deacetylation degree of CH was measured by Infrared Spectroscopy (FTIR) and potentiometric titration; polymer molecular weight was determined by intrinsic viscosity measurements. Reticulated micro/nanoparticles of chitosan (MCH) with an average diameter close to 100nm were synthesized by ionic gelation of chitosan using tripolyphosphate (TPP), and characterized by SEM, size distribution and Zeta-potential. Detoxification capacities of CH and MCH were tested analyzing the removal of hexavalent chromium Cr(VI) from contaminated water, at different initial chromium concentrations. The effect of pH on adsorption capacity of CH and MCH was experimentally determined and analyzed considering the Cr(VI) stable complexes (anions) formed, the presence of protonated groups in chitosan particles and the addition of the reticulating agent (TPP). Chitosan crosslinking was necessary to adsorb Cr(VI) at pH<2 due to the instability of CH particles in acid media. Langmuir isotherm described better than Freundlich and Temkin equations the equilibrium adsorption data. Pseudo-second order rate provided the best fitting to the kinetic data in comparison to pseudo-first order and Elovich equations. Chemical analysis to determine the oxidation state of the adsorbed Cr, showed that Cr(VI) was adsorbed on CH particles without further reduction; in contrast Cr(VI) removed from the solution was reduced and bound to the MCH as Cr(III). The reduction of toxic Cr(VI) to the less or nontoxic Cr(III) by the reticulated chitosan micro/nanoparticles can be considered a very efficient detoxification technique for the treatment of Cr(VI) contaminated water.
authors.affiliation: Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA-CONICET-UNLP), Calle 47 y 116, La Plata 1900, Argentina; Centro Nacional Patagónico (CONICET-CENPAT), Blvd. Brown N° 2915, U9120ACD Puerto Madryn, Chubut, Argentina.
authors.forename: Jimena Bernadette
authors.initials: JB
authors.lastname: Dima
authors.affiliation: Centro Nacional Patagónico (CONICET-CENPAT), Blvd. Brown N° 2915, U9120ACD Puerto Madryn, Chubut, Argentina.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Sequeiros
authors.affiliation: Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA-CONICET-UNLP), Calle 47 y 116, La Plata 1900, Argentina; Depto de Ingeniería Química, Facultad de Ingeniería, Universidad Nacional de La Plata, Argentina. Electronic address: zaritzkynoemi@gmail.com.
authors.forename: Noemi E
authors.initials: NE
authors.lastname: Zaritzky
mesh_terms: D000327:Adsorption; D060105:Animal Shells / Q000737:chemistry; D000818:Animals; D048271:Chitosan / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D005525:Food-Processing Industry; D007220:Industrial Waste; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D017747:Seafood; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D007220:Industrial Waste; D012996:Solutions; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D048271:Chitosan
keywords: Adsorption kinetics; Chitosan micro and nanoparticles; Equilibrium adsorption isotherms; Hexavalent chromium removal; Seafood waste; Water treatment