2.7. Batch Adsorption Experiments

A 1.589 g sample of Pb(NO₃)₂ was dissolved in 1.0 L of distilled water. Different concentrations of Pb(NO₃)₂ solution were obtained by diluting the stock solution (1.0 g/L) of Pb²⁺. In order to understand the effect of pH, contact time, and initial Pb²⁺ concentration on adsorption of Pb²⁺, pH was set in the range of 2.0–6.0, contact time of 10 min to 1440 min, and the initial Pb²⁺ concentration of 20 mg/L to 300 mg/L. After adsorption, the microspheres were separated from the solutions using a filter. The initial and final Pb²⁺ concentrations were determined by an atomic absorption spectrophotometer (AAS, A3AFG-12, Puxi, Beijing, China). The removal rate (R) and the adsorption capacity (q_e) for Pb²⁺ are calculated as follows:

where C₀ and C_e (mg/L) are the initial and equilibrium concentrations of Pb²⁺ solution, respectively. V (L) is the volume of the solution, and m (g) is the mass of the adsorbent.

The experimental results of contact time and initial Pb²⁺ concentration were used for adsorption kinetics and isotherm study, respectively (Table 1).

Kinetics and adsorption isotherm models used to study the adsorption process.