Sand/polyethyleneimine composite microparticles: Eco-friendly, high selective and efficient heavy metal ion catchers

Abstract

The modification of natural sand surface with a high number of amino groups represents an interesting route to obtain organic nanostructured films onto solid surfaces aiming heavy metal ion decontamination of surface waters. Herein, one weak polycation (branched poly(ethyleneimine) (PEI)) and one weak polyanion (poly(acrylic acid) (PAA)) were one-step deposited through non-stoichiometric interpolyelectrolyte coacervate precipitation method onto different sizes sand fractions (F70, F100, F200, F355) followed by glutaraldehyde (GA) cross-linking. The sand composites, with ten times higher and fast sorption properties toward heavy metal ions compared with bare sand, were obtained only after PAA extraction in strong basic media from previously cross-linked sand//(PEI-GA/PAA) composite surfaces. The sorbed amount of heavy metal ions in column experiments depended on the amount of organic material deposited on the sand particles, amount which depended on the sand fraction size. The maximum recorded value, after 5 cycles of loading/release of copper ions onto F70//(PEI-GA), was ~7 mg Cu2+/mL column composite (or ~80 mg Cu2+/g composite shell). Natural sand composites based on cross-linked PEI chains on the solid surface could be very promising by scaling up the production, inexpensive, and environmentally friendly solid sorbents used in multiple water cleaning processes (non-competitive conditions) and copper separation from an aqueous mixture (competitive conditions).