Adsorption thermodynamic and kinetic studies of Pb(II) removal from water onto a versatile Al₂O₃-supported iron oxide

The use of versatile sorbents has been investigated for wastewater treatment. An investigation into the use of activated alumina-supported iron oxide (denoted as FeAA), which is a by-product of the wastewater treatment plant. In our previous study, the FeAA has successfully been as heterogeneous photoassisted Fenton catalyst for degradation azo dye at neutral pH 7.0. In this work, the test and use of FeAA as adsorbent for the removal of lead (Pb²⁺) from water are carried out. The highest Pb²⁺ adsorption capacity was determined as 0.14 mmol g^-1 for 0.8 mmol dm^-3 initial Pb²⁺ concentration at pH 5.0 and 318 K. Adsorption data were well described by the Langmuir model and the thermodynamic constants of the adsorption process: ΔG°, ΔH° and ΔS° were evaluated as -19.4 kJ mol^-1 (at 318 K), 25.73 kJ mol^-1 and 0.113 J mmol^-1 K^-1, respectively. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The pseudo-second-order kinetic model provided the best correlation of the experimental data compared to the pseudo-first-order model.