Transport of Arsenate with Iron Hydroxide Nanoparticles in Saturated Sand: Effects of Solution Ionic Strength, pH, and Humic Acid

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Author(s) Mpinda T. Martin | Abass K. Olusegun
Pages 640-654
Volume 3
Issue 10
Date October, 2014
Keywords Arsenate, Iron hydroxide, Co-transport, Adsorption

This study aims to understand the co-transport of Fe(OH)3 nanoparticles and arsenate in saturated sand column and the associated influence of pH, humic acid and ionic strength on the transport. HYDRUS-1D computer program was used to simulate the sorption and transport of Fe(OH)3 nanoparticles with arsenate through calibration of the breakthrough curves (BTCS). Data from different dissimilar (pH, Humic acid, and Ionic strength) input concentrations were compared to identify their influences on the nanoparticles and arsenate transport and sorption. Results from this study indicated that transport of iron hydroxide nanoparticles was influenced not only by ionic strength, humic acid, ionic composition and pH, but also by the flow velocity, nature and size of suspended nanoparticles. Nanoparticles were very mobile at low ionic strength, while increasing salt concentration decreased mobility, and consequently the amount of particles retained in the column increased. The transport of iron hydroxide nanoparticles became normalized due to the availability of (OH-) at pH 7-9. Below this pH value, the iron hydroxide nanoparticles precipitates, increasing the amount of (OH+) than (OH-) on the surface of the adsorbent. Conversely, the transport of arsenate was reduced under strongly acidic and alkaline conditions. Humic acid had considerable influence on the mobility of arsenate, resulting in more adsorption and less transport. A major implication of this study was that changes in chemical composition of solutions in aquifers and vadose zones might result in a different transport mechanism for nanoparticles as well as the associated transport of adsorbed arsenic.

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