Examination of the Effectiveness of Physical and Chemical Activation of Natural Bentonite for the Removal of Heavy Metal Ions from Aqueous Solutions

摘要

The ability of physically and chemically activated bentonite to adsorb copper and nickel ions from aqueous solutions was examined under various experimental conditions. Physically activated bentonite was obtained by thermal treatment of the initial material in an oven at 700 ℃ (T-bentonite), while chemically activated bentonite was obtained in two ways, either by treatment of the initial material with sodium dodecyl sulphate (SDS) as an anionic surfactant to give SDS-bentonite or with aluminium hydroxypolycation as a pillaring agent to give Al-bentonite. Batch adsorption tests were undertaken to study the removal of Cu~(2+) and Ni~(2+) ions from aqueous solutions using the above-mentioned types of activated bentonite. The adsorption capacity of the bentonites towards both Cu~(2+) and Ni~(2+) ions followed initial metal concentration, solution pH, temperature and salinity of the solution affected the adsorption capacity towards both metal ions. The uptake of Cu~(2+) ions increased with an increase in temperature (25-45 ℃) as well as with an increase in the initial pH of the solution (3-5). The uptake of Cu~(2+) and Ni~(2+) ions decreased significantly with an increase in the NaCl and KCl concentrations present in the aqueous solutions. Sulphuric acid of 0.1 M concentration was found to be an effective desorbent for bentonite laden with heavy metals.