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 100 nm
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.