Fazlul Bari

Kinetics of lanthanum(III) extraction from nitrate-acetato medium by Cyanex 272 in toluene using the single drop technique

Abstract The rate of forward extraction of La(III) from nitrate-acetato medium by bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272, H2A2) dissolved in toluene has been measured by the single drop technique. The rate of mass transfer per unit area is found to be proportional to [La(III)], [H2A2](o) and [H+]−1 at the interface. The forward extraction rate constant, kF, has been measured to be 10−7.0 m/s. From the temperature dependence of rate measurement, the values of Ea, ΔS±, ΔH± and ΔG300± are calculated to be 71 kJ/mol, −155 J/mol K, 69 kJ/mol and 115 kJ/mol, respectively. The rate expression can be written as; F La =10 −7.0 [ La 3+ ][ H 2 A 2 ] ( o ) [ H + ] ( i ) −1 kmol / m 2 s Analysis of the rate expression suggests that the formation of [La(HA2)]2+at interface from La3+and HA2− is the rate-determining step for the forward extraction of La(III). Negative entropy of activation suggests that the above rate-determining step occurs via the SN2 mechanism.

Kinetic and Thermodynamic Studies on Adsorption of Copper Ions onto Pomelo Peel (Citrus grandis)

The ability of pomelo peel (PP) as natural adsorbent to remove Cu (II) ions from aqueous solution was investigated. The influence of solution pH, contact time and temperature were evaluated. Cu (II) removal increased as the pH of the solution increased and the maximum value reached at pH 6. The adsorption was relatively fast (30 min). Adsorption kinetics followed the pseudosecondorder model. At low temperature the adsorption was not affected but at high temperature it was reduced. PP is considered as low cost material that shows potential to be applied in wastewater technology for remediation of heavy metal contamination.