Carbon-based adsorber resin Lewatit AF 5 applicability in metal ion recovery

Abstract

The microporous carbonaceous adsorbent Lewatit AF 5 was applied in metal ions recovery from aqueous acidic solutions. The batch method was used throughout the studies. The affinity and sorption capacity of selected metal ions (Pd(II), Co(II), Cu(II), Ni(II), Zn(II)) were evaluated. A series of batch tests was carried out as a function of contact time (1 min–4 h), and acid concentrations (0.1–6.0 M HCl – 100 mg M(II)/L; 0.1–0.9 M HCl – 0.9–0.1 M HNO3 – 100 mg M(II)/L). Additionally, the effect of the initial Pd(II) concentrations (100, 500, 1000 mg/L), beads size (0.4–0.8 mm), agitation speed (120, 140, 180 гpm) and adsorption temperature (298, 313, 333 K) was analysed. The results of kinetic and equilibrium studies for palladium(II) ions removal were presented. The thermodynamic parameters were obtained and pHPZC, SEM, XRD results before and after palladium sorption on Lewatit AF 5 were also shown. The working ion exchange capacities of palladium were determined based on the breakthrough curves (column method). Desorption and reuse possibilities of carbonaceous resin were checked. The adsorption capacity of carbon-based adsorbent determined from the Langmuir isotherm model at ambient temperature was found to be 193.31 mg/g. Kinetic studies of Pd(II) followed the pseudo-second order model. Effects of experimental conditions such as agitation speed, temperature and bead size distribution are slightly marked. The most effective desorption of palladium was obtained using 0.5 M ammonium hydroxide (%D = 71.5%). The reduction of sorption capacity after 3 cycles of sorption-desorption is less than 10% (exception of the solutions containing thiourea). The process is spontaneous and exothermic in nature and the entropy possesses negative values.