Removal of Cr (VI) from aqueous solution by Eichhornia crassipes root biomass-derived activated carbon

In this work, the removal of Cr (VI) from aqueous solutions by activated carbon prepared from the Eichhornia crassipes root biomass has been studied. Activated carbon is prepared and characterized, using SEM–EDX, FTIR and XRD. Dependence of adsorption on adsorbent dose, pH of the solution, contact time, and temperature had been studied to achieve the optimum condition. The maximum removal capacity of activated carbon was found to be 36.34 mg/g, at optimum conditions of pH 4.5, contact time of 30 min, biomass dosage of 7 g/L, and temperature of 25 ± 2 °C. The mean sorption energy (E) is calculated from D–R model which indicate the chemisorptions nature of adsorption. The pseudo-second-order equation described the kinetics of Cr (VI) adsorption (R2 > 0.99). Thermodynamic parameters reveal that the adsorption process is endothermic, spontaneous, and feasible in nature. Column studies are also performed to know the breakthrough point with an initial concentration of 10 mg/L. The effluent volume at breakthrough is found to be 100 bed volumes, and the column capacity is found to be 0.8 mg/g.

► The maximum removal efficiency of Cr (VI) is found to be 92.24% at pH 4.5.
► The pseudo-second-order equation described the kinetics with R2 > 0.99.
► Langmuir isotherm is better fitted than others with R2 > 0.99.
► At breakthrough point the effluent is 100 bed volumes, and the column capacity is 0.8 mg/g.