The biosorption potential of waste biomass young fruit walnuts for lead ions: Kinetic and equilibrium study

Abstract

The biosorption potential of waste biomass young fruit walnuts (YFW) as a low-cost biosorbent, processed from liqueur industry, for Pb(II) ions from aqueous solution was explored. The structural features of the biosorbent were characterized by FTIR spectroscopy, which indicates the possibility that the different functional groups may be responsible for the binding of Pb(II) ions from aqueous solution. The effects of relevant parameters such as pH (2 - 6), contact time (0 - 120 min), biosorbent dosage (2 - 20 g), initial metal ion concentration (10 - 120 mg dm-3), at a temperature of 25(C with stirring (120 rpm) and a constant ionic strength of 0,02 mol dm-3 were evaluated in batch experiments. The sorption equilibrium of Pb(II) ion (when 84 % of metal ions were sorbed at an initial concentration of 15 mg dm-3) was achieved within the pH range 4 - 5 after 50 min. Kinetic data were best described by the pseudo-second order model. Removal efficiency of Pb(II) ion rapidly increased with increasing biosorbent dose from 2.0 to 8.0 g per dm-3 of sorbate. Optimal biosorbent dose was set to 6.0 g per dm3 of sorbate. An increase in the initial metal concentration increases the biosorption capacity. The sorption data of investigated metal ion are fitted to Langmuir, Freundlich and Temkin isotherm models. The equilibrium data were well fitted by the Langmuir isotherm model (R2 ≥ 0.990). The maximum monolayer biosorption capacity of waste biomass YFW for Pb(II) ion, at 25.0 ± 0.5°C and pH 4.5, was found to be 19.23 mgg-1. This available waste biomass is efficient in the uptake of Pb(II) ions from aqueous solution and could be used as a low-cost and an alternative biosorbent for the treatment of wastewater streams bearing these metal ions.

Keywords

• biosorption
• waste biomass
• fruit walnut
• lead ions
• kinetic
• isotherms