Sequestration of hexavalent chromium and paracetamol from water using deoiled hemp stem-twigs and roots and activated carbon

Abstract

In the present study, deoiled hemp stem-twigs and roots and activated carbon were used to remove chromium and paracetamol. The hemp-based materials were characterized, and the surface area of the activated carbon samples increased more than 55-fold compared to the untreated materials. The pore volume of the carbon samples also increased, which can be attributed to the degradation of volatiles during carbonization and acid treatment. Contact time experiments showed that the uptake rate for hexavalent chromium was fast in the initial phase and equilibrium was reached in about 30 min for activated carbon from stem-twigs and activated carbon from hemp roots, while it took about 40 min for untreated hemp stem-twigs and untreated hemp roots. The trends for paracetamol show that the rate was slow compared to hexavalent chromium. Equilibrium was reached in about 120 min for all materials. pH solution 2 was optimal for the uptake of hexavalent chromium, while pH solution 6 was optimal for the adsorption of paracetamol. The data for enthalpy show that the sorption processes were endothermic and predominantly physisorptive. The values for Gibbs free energy were negative, indicating that the sorption was spontaneous and feasible.