Asian Journal of Chemical Sciences

Pb(II) and Fe(III) ion adsorption from aqueous (water) solution onto an unaltered oil palm peduncle was investigated for thermodynamic effects. With a given mass (0.2 g) of adsorbent and a fixed adsorbate concentration of 10 ppm, adsorption studies were conducted in a batch method. Using an atomic absorption spectrophotometer, changes in the adsorbates' concentration during the course of the adsorption process were examined. Using van't Hoff's plots, thermodynamic parameters like ΔH° and ΔS° were computed.

At the range of temperatures (30,40,50 and 60°C) studied, ΔG° changed in the order -5.49, -4.39, -4.42 and -4.79 kJmol^-1 for Pb(II) and -2.83, -2.50, -2.58, and -1.99 kJmol^-1 for Fe(III). The values of ΔH° of Pb(II and) were -11.97 and -10.19 kJmol^-1 respectively. The ΔS° values of lead(II) and iron(III) were 22 and 24.30 kJmol-1K^-1 respectively. The disorder (randomness) of the adsorbate particles over the adsorbent surface is indicated by positive values of standard change (ΔS°). The attachment processes of both ions were exothermic and responsive, as signified by the negative figures of the standard change of Gibbs free energy (ΔG°) and standard enthalpy change (ΔH°). For both ions, spontaneity declined with increasing temperature. The attachment of Pb(II) and Fe(III) onto oil palm peduncle grind had activation energies, or Ea, of 11.97 and -10.19 kJmol^-1, respectively. As a result, the adsorption processes were physical (Ea < 40 kJmol^-1). The palm fruit peduncle's ability to absorb the metal ions was diminished by the increase in adsorbent dosage. At low temperatures, lead (II) and iron (III) ion adsorption onto an unaltered oil palm peduncle is thermodynamically possible.