Particle Size Dependance of Nano-Magnetite in Arsenic Removal

John Thomas Mayo
Department of Chemistry, Rice University

Sujin Yean
Department of Civil and Environmental Engineering, Rice University

Lili Cong
Department of Civil and Environmental Engineering, Rice University

Cafer Yavuz
Department of Chemistry, Rice University

William Yu
Department of Chemistry, Rice University

Josh Falkner
Department of Chemistry, Rice University

Amy Kan
Department of Civil and Environmental Engineering, Rice University

Mason Tomson
Department of Civil and Environmental Engineering, Rice University

Vicki Colvin
Department of Chemistry, Rice University

     Full text: Login to access
     Last modified: April 29, 2006

Abstract
The removal of arsenic from drinking water to meet higher environmental standards has been the topic of numerous studies. Current methods use adsorbents such as iron oxides, aluminum hydroxides, alumina, and carbon which are adequate but not efficient enough to keep up with global development. Iron oxide is particularly interesting because its magnetic properties allow relatively routine dispersal and recovery of the adsorbent from the environment or industrial processing facilities. The objective of this study was to reevaluate the potential arsenic adsorption by iron oxide, specifically magnetite (Fe3O4) nanoparticles. In this study we focused on the effect of magnetite particle size on the adsorption and desorption behavior of As(III) and As(V). The results show that the nanoparticle size has a dramatic effect on the magnetite’s ability to adsorb and desorb arsenic. Our studies demonstrate that as the particle size is decreased from 300 nm to 11.72 nm the adsorption capacities for both As(III) and As(V) increases approximately by 1000 times, which is more than expected even after accounting for the overall increase in surface area. The desorption process however, exhibits some hysteresis with the effect becoming more pronounced with small nanoparticles. This hysteresis most likely results from a higher arsenic affinity for magnetite nanoparticles. Further studies need to be performed; however the use of magnetite nanoparticles could prove to be a very attractive method of arsenic removal from water systems.