Biosorption of Pb(ii) and Fe(iii) from aqueous co-solutions using chemically pretreated oil palm fronds

Abstract

The removal of Pb(II) and Fe(III) from aqueous solutions using specially pretreated oil palm fronds (OPF) as biosorbents was investigated. OPF biosorbents were prepared through four different pretreatment processes; SCM0.5 (0.5 M NaCl/0.5 M Na₂SO₄ solution 1 : 1), SM1 (1 M Na₂SO₄ solution), CM1 (1 M NaCl solution) and SMCM1 (SM1 and CM1 1 : 1). The biosorbents were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Variables such as adsorbent dosage (0.25 g L⁻¹ to 1.75 g L⁻¹) and agitation time (10 min to 80 min) were investigated. The pH range for the solutions was adjusted between 5 and 6. The optimum biosorbent dosage and agitation time for removing Pb(II) and Fe(III) using the SCM0.5 biosorbent were 1.25 g L⁻¹ and 20 min, respectively. Compared with the other biosorbents, SCM0.5 exhibited the highest adsorption efficiency of 98% and 92% for Pb(II) and Fe(III), respectively. Adsorption equilibrium data were fitted into three adsorption isotherm models for the SCM0.5 and SMCM1 biosorbents. The Langmuir isotherm accurately fits the results for Fe(III) ions, whereas the Freundlich isotherm shows the best result for Pb(II). Kinetics of the biosorption process via the SCM0.5 and SMCM1 biosorbents were analyzed using pseudo-first-order and pseudo-second-order models. The latter demonstrates a better fit for both metals.