Hydrotalcite as adsorbent for the removal of chromium (VI) from aqueous media:Equilibrium studies

摘要

The sorbent power of hydrotalcite ocmpound [Mg_3Al(OH)_8]_2CO_3xH_2O for Cr(VI) from water solution has been evaluated.The adsorption behaviour of Cr(VI) was investigated at different initial concentration of adsorbate,contact time,pH,temperature and adsorbent dose by batch equilibrium technique.The extent of adsoration decreased from 23.2 mg to 4.9 mg with increase in pH from 2.0 to 10.0 The adsorption of Cr(VI) on the outer surface as well as diffusion within the pores of the adsorbent.The mass-transfer coefficients as a function of temperature were calculated to explain the results.The adsorption follows first-order kinetics.A Langmuir isotherm model fits the equilibrium data well.Thermodynamic parameters such as (triangle open)Gdeg,(triangle open)Hdeg and (triangle open)Sdeg were calculated to predict the nature of adsorption.Delorption studies showed that about 95.7% of Cr(VI) can be desorbed from the adsorbent at 0.1 M NaOH.The efficiency of the adsorbent to remove Cr(VI) from synthetic wastewater has also been tested.