2.3. Preparation of the sorbate
The metal ion solutions, containing analytic reagents from
Sigma of copper(II) ions from 99% pure Cu(NO3)23H2O, lead(II)
ions from 94 to 100% pure Pb(NO3)2, nickel(II) ions from 99% pure
Ni(NO3)26H2O, and cadmium(II) ions from 98% pure
Cd(NO3)24H2O, were prepared from 1000 mg L1 stock solutions.
To prevent competitive adsorption, each adsorption experiment
was run using only a single test metal. To prevent concentration
interference, the initial concentrations of metal ions were
controlled to 300 mg L1 for all experiments.
2.4. Kinetic adsorption experiment
Each biosorbent (1 g) was added to a beaker containing a 1 L
solution of the test metal ion. The pH value of the solution was
controlled at 5.00 0.1. The test mixture was stirred using a
magnetic stirrer at 25 8C for 120 min. Samples (1 mL each) were
collected at specified times to determine metal ion concentrations by
using atomic absorption (AA) spectrometry (Avanta, GBC scientific
equipment).