Hexavalent chromium sorption from aqueous solutions by heat-treated rice hull biomass
2007
Oncog, R.T.A.
Heat-treated rice hull was used for Cr (VI) sorption from aqueous solutions. Scanning electron microscopy revealed changes in the microstructure after Cr (VI) uptake. Potantiometric titrations and Fourier Transform infrared spectroscopy suggested the involvement of weakly basic groups in Cr (VI) sorption by the biomass. The kinetic experiments were evaluated for the first-order and second-order rate laws. Calculations showed that the second-order kinetic model best correlated with the experimental data. The calculated rate constant was 0.1360 g/mg/min. The mechanisms of Cr (VI) sorption was proposed to involve an anion exchange process accompanied by the reduction of Cr (VI) to Cr (III). Maximum Cr (VI) uptake occurred at pH3 using the 45 micro m rice hull biomass. The equilibrium sorption data for both heat-treated and control rice hull were adequately described by the Freudlich model of heterogeneous sorption. The calculated K or sorption capacity was higher for the heat-treated biomass indicating that it was the more efficient sorber of Cr (VI).
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