Chelate coupling with pineapple leaves as a modified bio-sorbent for lead ions (II) removal

Abstract

Modification of cellulose-rich agricultural waste, pineapple leaves, was conducted for the purpose of lead (Pb) adsorption from aqueous solution. The process was executed in two scales: one with simply mercerizing the leaves using sodium hydroxide, and the other furthered by coupling iminodiacetic acid with the cellulose content of the waste material. Batch model was adapted for this study, and different kinetic and isotherm models were compared for the acquired data. The effect of initial concentration of lead ions, time, and the recyclability was the aspects in focus, while temperature and pH were controlled at 30 °C and 5.5, respectively. Scanning electron microscopy shows an evident change to the raw material after the mercerization process in terms of cellulose fibers exposure. In addition, CHN elemental analysis suggests a nearly doubling of nitrogen content in the adsorbent after coupling treatment, which indicates the success of binding the amino group to the cellulose polymer. Both adsorbents made a better fit to the pseudo-second-order kinetic model. Similarly, they were better represented by Freundlich isotherm model. The potential of the modification conducted can be concluded from the achieved maximum lead ions uptake of 45, 18.7 mg/g at lead concentration of 400 mg/L for iminodiacetic acid coupled leaves compared to mercerized leaves, respectively. Moreover, iminodiacetic acid coupled leaves managed to sustain more than 87% of its initial capacity after four cycles of adsorption and desorption, which indicates a great reusability potential.