Acid-vacuo heat treated low cost banana stems fiber for efficient biosorption of Hg(ii)

Abstract

The potential of banana stem fiber (BSF) as a low cost biosorbent for Hg(II) removal was studied. HCl treatment increased the cellulose accessibility which led to an enhanced interaction of Hg(II) and BSF. Activation of BSF-HCl in vacuo at 373 K increased the maximum biosorption capacity from 28 to 372 mg g⁻¹ and altered the activation energy from 3.5 to 76.9 kJ mol⁻¹ showing an increase in Hg(II) chemisorption. FTIR and ESR results confirmed the large amount of structural defects on the activated BSF-HCl which led to the increase in Hg(II) uptake. Batch biosorption models showed that the kinetics follow pseudo-second-order and the equilibrium uptake fitted to all three-parameter models showing the Hg(II) biosorption behaves as a Langmuir isotherm. The non-linear regression method exhibited higher coefficient of determination values for isotherm and kinetic analyses compared to the linear method. The thermodynamic functions indicated that the nature of Hg(II) biosorption is an exothermic and non-spontaneous process.