synthesis of a high characteristics activated carbon from walnut shell for the removal of cr (vi) and fe (ii) from aqueous solution: single and binary solutes adsorption

A high performance activated carbon was synthesized using walnut shell as asolid waste through a two-step zinc chloride chemical activation-thermalpyrolysis process. characterization results demonstrated its porous structurewith very good textural properties such as high bet surface area (1223 m2/g)and high total pore volume (0.85 cm3/g). the final adsorbent was used foradsorption of fe (ii) and cr (vi) from aqueous solution. effect ofph, initialconcentration of metal ions, temperature, and contact time on adsorptioncapacity of the adsorbent was investigated. adsorption results revealed thatthe maximum removal of fe (ii) and cr (vi) ions, occurred at ph 4. 5 and 2respectively, were 96.2% and 99% at 313k. the equilibrium and kineticsdata for adsorption of single-component ions were well described by the sipsisotherm and the pseudo-nth-order models, respectively. the impact ofcompeting ions was studied by adsorption of a binary solution of fe (ii) andcr (vi) ions. the binary adsorption isotherm was described by the modifiedlangmuir model and model parameters were found following an optimizationprocedure by genetic algorithm. finally, the developed walnut-shell basedactivated carbon showed higher adsorption efficiency compared to otheractivated carbons at similar conditions.