The Influence Of Nanochitin Preparation Conditions On The Yield, Particle Size And Zeta Potential

Chitin is secondary most abundant natural polymer containing amino groups on it backbone.It is generally insoluble in water,aqueous solution of acid and alkali solution,concentrated alkali and organic solvents.It can be dissolved in concentrated hydrochloric acids,sulfuric acid,phosphoric acid and anhydrous formic acidunder high temperature condition.In concentrated hydrochloric acid,chitin can be partially deacetylatedin a mild condition and resulted in nanosized crystal particles.This research was to investigate the optimal conditions for chitin hydrolysis under different combination of reaction ratio,temperature,and reaction time.The particle size and size distribution,charge density and relative yield of resulted products were also studied.This study used shrimp chitin fibers as basic material,3N of hydrochloric acid as a reactant.Chitin fibers were hydrolyzed under different reaction conditions.The product was collected by centrifugation,dialysis against deionized water and ultrasonication to break down aggregates.Dynamic light scattering,conductometric titration were employed to characterize the size and size distribution,charge density,and the zeta potential of the nanoparticles.The morphology was visualized and measured by transmission electric microscopy and/or field emission scanning electric microscopy.The primary results showed that the yielding was variable under different react ratio,temperature.When ratio of chitin to hydrochloric acid was 1:200under 70,80,85,and 90 oC for 2 hours,the yields of nanochitinwere 10.563.65%,7.923.65%,2.773.65%,and 3.65%,respectively;the charge densities of the relative products were 110.97,352.04,905.17 and 831.15mmol/kg.As increase of ratio of reactant to chitin(more diluted),more free ions of H+ were involved in hydrolysis,the charge density and zeta potential increased dramatically,resulting in particle size in the range of 130-150 nm in length and 30-50 nm in width.By static analysis,we concluded that the under reaction ratio of chitin to reactant of 1:300at 85 oC for 2 hours it reached a highest yield and charge density of the nanoparticles,thus would be the optimal condition for industrial production.