RESEARCH ARTICLE Removal of Pb(II), Cd(II), Cu(II), and Zn(II) by hematite nanoparticles: effect of sorbent concentration, pH, temperature, and exhaustion Heather J. Shipley & Karen E. Engates & Valerie A. Grover Received: 25 April 2012 / Accepted: 10 May 2012 / Published online: 30 May 2012 # Springer-Verlag 2012 Abstract Nanoparticles offer the potential to improve en- vironmental treatment technologies due to their unique properties. Adsorption of metal ions (Pb(II), Cd(II), Cu(II), Zn(II)) to nanohematite was examined as a function of sorbent concentration, pH, temperature, and exhaustion. Adsorption experiments were conducted with 0.05, 0.1, and 0.5 g/L nanoparticles in a pH 8 solution and in spiked San Antonio tap water. The adsorption data showed the ability of nanohematite to remove Pb, Cd, Cu, and Zn species from solution with adsorption increasing as the nanoparticle concentration increased. At 0.5 g/L nanohema- tite, 100 % Pb species adsorbed, 94 % Cd species adsorbed, 89 % Cu species adsorbed and 100 % Zn species adsorbed. Adsorption kinetics for all metals tested was described by a pseudo second-order rate equation with lead having the fastest rate of adsorption. The effect of temperature on adsorption showed that Pb(II), Cu(II), and Cd(II) underwent an endothermic reaction, while Zn(II) underwent an exo- thermic reaction. The nanoparticles were able to simulta- neously remove multiple metals species (Zn, Cd, Pb, and Cu) from both a pH 8 solution and spiked San Antonio tap water. Exhaustion experiments showed that at pH 8, exhaus- tion did not occur for the nanoparticles but adsorption does decrease for Cd, Cu, and Zn species but not Pb species. The strong adsorption coupled with the ability to simultaneously remove multiple metal ions offers a potential remediation method for the removal of metals from water. Keywords Metals . Nanoparticles . Sorption . Kinetics . Thermodynamics . Exhaustion Introduction Researchers in science and engineering continue to have increased interest in the use of nanoparticles due to their unique physical and chemical properties. One area of par- ticular interest focuses on environmental clean-up (Engates and Shipley 2011; Liu 2006; Tratnyek and Johnson 2006), especially in regard to public health and drinking water quality. Electronic waste (e-waste, i.e., waste generated from cell phones, computers, toys, and other electronics) has become the most rapidly growing waste stream in the in- dustrialized world, growing 4 % annually (UNEP, DEWA/ GRID-Europe 2005). Considerable attention has been raised over the amount of e-waste that is improperly disposed of each year since it contains several metals which eventually may find their way into potential sources of drinking water. While naturally distributed levels of metals found in rocks and soils are usually not cause for concern, anthropogenic activities (e.g., industrial, agricultural, and military sources and incorrect disposal of e-waste) often disperse metal pol- lution throughout the environment, which may pose human health risks at high levels (USEPA 2006). Currently, the US Environmental Protection Agency regulates at least 10 Responsible editor: Vinod Kumar Gupta Electronic supplementary material The online version of this article (doi:10.1007/s11356-012-0984-z) contains supplementary material, which is available to authorized users. H. J. Shipley (*) : K. E. Engates Department of Civil and Environmental Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA e-mail: heather.shipley@utsa.edu V. A. Grover Department of Civil and Environmental Engineering, CALIBRE, 1777 NE Loop 410, Suite 628, San Antonio, TX 78217, USA Environ Sci Pollut Res (2013) 20:1727–1736 DOI 10.1007/s11356-012-0984-z