Removal of heavy metals by using adsorption on alumina or chitosan

The removal of heavy metals from wastewater by using activated alumina or chitosan as adsorbers was evaluated. Cd(II) and Cr(III) were employed as models of the behaviour of divalent and trivalent metal ions. The adsorption of Cd(Il) and Cr(III) onto the adsorbers evaluated was studied as a function of pH, time, amount of adsorber, concentration of metal ions and sample volume. A 0.4-g portion of activated alumina can retain 0.6 mg Cr(III) and 0.2 mg Cd(II) from 20 mL sample adjusted at pH 4 and stirred for 30 min. It is therefore possible to totally decontaminate 500 mL of a waste containing 5 mg L-1 Cd(II) and Cr(III) with 10 g alumina. On the other hand, 0.4 g chitosan can totally decontaminate 20 mL of a pH 5 solution containing up to 50 mg L-1 Cd(II) and Cr(III). A 99.2 +/- 0.1% retention of Cd(II) and 83 +/- 1% retention of Cr(III) was obtained from 500 mL of a laboratory waste. The aforementioned strategies were applied for the minimization of analytical chemistry teaching laboratories and atomic spectrometry laboratory wastes. On comparing both adsorbers it can be concluded that chitosan is more preferable than alumina due to the reduced price of chitosan and the absence of side-pollution effects.