Heavy metal removal from aquatic systems by northern Anatolian smectites

Competitive adsorption of the heavy metal ions Cu(II), Cd(II) and Pb(II) from aqueous media onto northern Anatolian smectites with a mean particle diameter of 200 μm, was investigated. The adsorption rate and capacity of the smectite for the selected heavy metal ions, containing different amounts of these ions (5-900 mg/L) at values ranging from pH 1.0 to 7.0 were studied. Very high adsorptions rates were observed at the beginning, and adsorption equilibria were then gradually achieved in about 30 minutes. The maximum adsorption of metal ions onto the smectite were found to be 41.46 mg Cd(II), 36.11 mg Pb(II) and 18.72 mg Cu(II) per gram of smectite. The order of affinity based on weight uptake by smectite was Cd(II)>Pb(II)>Cu(II). When the metal ions competed (in the case of adsorption from their mixture), the amounts of Cd(II), Pb(II) and Cu(II) ions adsorbed were 11.86 mg, 11.23 mg and 16.76 mg per gram of smectite, respectively. Desorption of the metal ions from smectite was studied in 0.5 M HNO₃ and very high desorption rates, greater than 95%, were achieved in all cases.