Host–Guest Extraction of Heavy Metal Ions with p-t-Butylcalix[8]arene from Ammonia or Amine Solutions

Figure 1

Extractability of all tested transition metal ions as a function of pH. Organic phase: H₈L = 5 × 10⁻⁴ M; aqueous phase: = (●) 5 × 10⁻⁵ M; succinic acid = 0.01 M; and buffer solution: 0.01 M; MES-NaOH (pH 5.0–7.0) and 0.1 M Tris-HClO₄ (pH 7.0–9.0). [Cd²⁺] = (■)1 × 10⁻⁴ M, 0.2 M NaClO₄. O/A = 1; T = 25°C. O:A represents the ratio between organic (O) and aqueous (A) volumes in the experiments.