Comparison of K (d), distribution coefficient, with other literature showed that the nanoparticles were better sorbents than other metal oxide nanoparticles and a commercial activated carbon.

No abstract

The use of commercially prepared hematite nanoparticles (37.0 nm) was studied as an adsorbent in the removal of Cd(II), Cu(II), Pb(II), and Zn(II) from aqueous solutions. Single-metal adsorption was studied as a function of metal and adsorbent concentrations, whereas binary metal competition was found to be dependent on the molar ratio between the competing metals. Competitive effects indicated that Pb had strong homogenous affinity to the nanohematite surface, and decreased adsorption of Cd, Cu, and Zn occurred when Pb was present in a binary system. Metal adsorption strength to nanohematite at pH 6.0 increased with metal electronegativity: Pb > Cu > Zn ∼ Cd. Equilibrium modeling revealed that the Langmuir-Freundlich composite isotherm adequately described the adsorption and competitive effects of metals to nanohematite, whereas desorption was best described by the Langmuir isotherm. The desorption of metals from nanohematite was found to be pH dependent, with pH 4.0 > pH 6.0 > pH 8.0, and results showed that greater than 65% desorption was achieved at pH 4.0 within three 24-h cycles for all metals.

Nanoparticles offer the potential to improve environmental 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 nanohematite, 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 exothermic reaction. The nanoparticles were able to simultaneously 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, exhaustion 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.

Safe drinking water is paramount to human survival. Current treatments do not adequately remove all heavy metals from solution, are expensive, and use many resources. Metal oxide nanoparticles may be ideal sorbents for heavy metals due to their smaller size and increased surface area in comparison to bulk media. Heavy metal adsorption (Pb, Zn, Cd) to hematite (Fe 2 O 3 ) and aluminum oxide (Al 2 O 3 ) nanoparticles was examined as a function of pH for use as a contaminant removal substrate in water treatment technology. Batch sorption experiments were conducted with 0.1 and 0.5 g/L nanoparticles. Adsorption results showed metal pHdependency with a Freundlich isotherm fit. Two-step desorption experiments using Pb and Cd indicated that Pb and Cd appeared to be irreversibly sorbed to the surface of hematite nanoparticles in the same solution conditions. Other experiments were conducted to determine the removal efficiency of multiple metals in solution by the nanoparticles. 0.5 g/L hematite nanoparticles simultaneously removed greater than 70% of Pb, Zn, Ni and Cd.