Hexavalent chromium removal in contaminated water using reticulated chitosan micro/nanoparticles from seafood processing wastes

DIMA JIMENA B.; SEQUEIROS CYNTHIA ; ZARITZKY NOEMI.

CHEMOSPHERE

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2015 vol. 141 p. 100 - 111

0045-6535

Chitosanparticles (CH) were obtained from seafood processing wastes (shrimp shells) andphysicochemically characterized; deacetylation degree of CH was measured byInfrared Spectroscopy (FTIR) and potentiometric titration; polymer molecularweight was determined by intrinsic viscosity measurements.Reticulatedmicro/nanoparticles of chitosan (MCH) with an average diameter close to 100 nm weresynthesized by ionic gelation of chitosan using tripolyphosphate (TPP), andcharacterized by SEM, size distribution and Zeta-potential. Detoxificationcapacities of CH and MCH were tested analyzing the removal of hexavalentchromium Cr(VI) from contaminated water, at different initial chromiumconcentrations.Theeffect of pH on adsorption capacity of CH and MCH was experimentally determinedand analyzed considering the Cr(VI) stable complexes (anions) formed, thepresence of protonated groups in chitosan particles and the addition of thereticulating agent (TPP). Chitosan crosslinking was necessary to adsorb Cr(VI)at pH < 2 due to the instability of CH particles in acid media. Langmuirisotherm described better than Freundlich and Temkin equations the equilibriumadsorption data. Pseudo-second order rate provided the best fitting to thekinetic data in comparison to pseudo-first order and Elovich equations.Chemicalanalysis to determine the oxidation state of the adsorbed Cr, showed thatCr(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). Thereduction of toxic Cr(VI) to the less or nontoxic Cr(III) by the reticulated chitosanmicro/nanoparticles can be considered a very efficient detoxification techniquefor the treatment of Cr(VI) contaminated water.