Attapulgite (ATP) is a hydrous layer-ribbon magnesium aluminum silicate mineral with a unique three-dimensional structure. Due to its natural abundance

extremely good mechanical/thermal stability

its one-dimensional nanoscale

and a large quantity of silanol groups on the surface

attapulgite is a very good candidate for low-cost materials as adsorbents. To increase adsorption capacity and selectivity

attapulgite must be treated with organo-functional groups to produce specific sites on the surface. Polyacrylic acid/attapulgite (PAA/ATP) was prepared by grafting PAA onto γ-methacryloxypropyl trimethoxy silane (MPS)-modified attapulgite surface via solution polymerization. PAA/ATP was characterized by thermogravimetry (TG) and X-ray photoelectron spectroscopy (XPS). The selective adsorption of ternary mixed heavy metal ions (Pb2+

Ni2+ and Cr3+) by polyacrylic acid/attapulgite composite adsorbents was evaluated in batch experiments by varying contact time and initial ion concentration. The kinetic data was fitted with the pseudo-second-order kinetic model

and the equilibrium data obtained was analyzed with the Langmuir and Freundlich isotherm equations. The kinetic data followed pseudo-second-order equation

indicating the chemical adsorption was the rate-limiting step process. The equilibrium adsorption data of Pb2+ could be described well with the Langmuir isotherm model. Obviously

PAA/ATP showed excellent adsorption selectivity for Pb2+ compared with Ni2+ and Cr3+ in terms of distribution coefficient and separation factor

which was also confirmed by XPS.