Abstract:
Microporous activated carbon was prepared from almond shell powder and activated with H3PO4
and was used for the removal of Cr (VI). The characterization of activated carbon was done for
Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–
Emmett–Teller (BET) surface area measurement and elemental analysis. The batch experiments were
conducted to study the effects of contact time, solution pH, adsorbent dose, initial chromium
concentration and temperature on removal of Cr (VI). The Cr (VI) removal was found to be 100% at an
initial pH of 2. The equilibrium data for the adsorption of Cr (VI) on the adsorbent were fitted with
Langmuir, Freundlich, Temkin and Dubinin–Radushkevich adsorption isotherm models. The Langmuir
isotherm model fitted better and values of model parameters qm, b, R2 and RL were found to be 195,
0.024, 0.98 and 0.45, respectively. Adsorption kinetics was analyzed for the pseudo first order,
pseudo second order and intra-particle diffusion situations. Thermodynamic parameters revealed the
spontaneous, endothermic and increased randomness nature of the adsorption process. The values
of Δ H and Δ S were found to be 22.9 KJ/mol and 95.3 J/mol-K
