Nanostructured surfaces

Lead(II) ions removal by the use of nanostructured biocarbons modified with poly(acrylic acid)
Wiśniewska M.1, Nowicki P.2
1 Department of Radiochemistry and Colloid Chemistry, Faculty of Chemistry, Maria Curie-Sklodowska University, M. Curie-Sklodowska sq. 3, 20-031 Lublin, Poland. e-mail: wisniewska@hektor.umcs.lublin.pl
2 Laboratory of Applied Chemistry, Faculty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego Street 8, 61-614 Poznań, Poland.

The activated biocarbons obtained from corn cobs 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 two-step chemical activation, including pyrolysis of the precursors at 500C in nitrogen atmosphere, followed by impregnation with K2CO3 (wt. ratio 2:1) and heat treatment at 800C. The obtained materials were characterized using the low-temperature nitrogen adsorption-desorption method, thermogravimetry, elemental analysis and back-titration method. The products of activation were micro/mesoporous biocarbons of medium developed surface area (862 and 654 m2/g, respectively), showing slightly acidic character of the surface.
The weight average molecular weight of the polymer equal to 2 kDa ensured penetration of polymer coils into the adsorbent pores under specific pH conditions. The adsorption tests were performed in the aqueous solution of pH 3 and at pH 5, at which hydrodynamic radius of PAA chains assumes values: 0.77 nm and 1.62 nm, respectively (viscosity measurements and calculations based on the Flory-Fox theory [1]). Moreover, under these conditions, there is no precipitation of lead hydroxide from the solution. The nanostructure of PAA adsorption layer without and in the presence of Pb(II) cations on the activated carbons surface was characterized based on the adsorption and electrokinetic data obtained from the spectrophotometric experiments, potentiometric titration and zeta potential measurements, 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.

1.	Flory P.J., Principles of Polymer Chemistry// Cornell University Press -1953- New York.