Simultaneous removal of lead(II) ions and poly(acrylic acid) macromolecules from liquid phase using of biocarbons obtained from corncob and peanut shell precursors

Abstract

The activated biocarbons obtained from corncobs and peanut shells were applied for simultaneous removal of poly(acrylic acid) – PAA macromolecules and lead(II) ions from their mixed solution. The biocarbons were prepared via the two-step chemical activation, including pyrolysis of the precursors at 500 °C in nitrogen atmosphere, followed by impregnation with K2CO3 and heat treatment at 800 °C. The obtained materials were characterized using the low-temperature nitrogen adsorption-desorption method, elemental analysis and back-titration method. The activation products were micro/mesoporous biocarbons of medium developed surface area (862 and 654 m2/g, respectively), showing slightly acidic character of the surface. The average molecular weight of PAA ensured penetration of polymer coils into the adsorbent pores under specific pH conditions. The nanostructure of PAA adsorption layer without and with Pb(II) cations on the activated carbons surface was characterized based on the adsorption, electrokinetic, stability and microscopic data obtained from the spectrophotometric experiments, both potentiometric titration and zeta potential measurements, turbidimetric experiments and SEM imaging, respectively. It was shown that the micro/mesoporous biocarbons are effective and cheap adsorbents for simultaneous removal of polymeric macromolecules and heavy metal ions from the liquid medium (the presence of both adsorbates has an extremely favorable effect on their adsorbed amounts).