(188a) Removal of Cr(VI) In Aqueous Solution by Fe3O4 Nanoparticles In the Presence and Absence of Mn(II)

Abstract: Chromium is widely used in various industrial process such as metal electroplating, leather tanning and manufacturing of products for corrosion protection. At the same time, it is one of the major pollutants around the world, which is found in soil, waste sites, and water. Chromium exists in the environment primarily in two valence states: Cr(VI) and Cr(III). Chromium (VI) is highly toxic compared with Cr(III) to biological activities. In the past decades, Cr(VI)-containing waste water was treated by various adsorbent via adsorption process, including activated carbon, chitosan, functionalized polymers and ferric oxides. Among these adsorbents, magnetite (Fe₃O₄) nanoparticles have been studied extensively. However, little is known regarding the effect of Mn(II) on the adsorption process. In this study, removal of cr(VI) in the presence and absence of Mn(II) by Fe₃O₄ nanoparticles was investigated. Fe₃O₄ nanoparticles were firstly synthesized by modified hydrolysis method, morphology and physical properties was measured by TEM, SEM, FTIR, XRD and VSM. Then effect of Mn(II) on Cr(VI) removal by obtained Fe₃O₄ nanoparticles was investigated under different pH value and ratio of Cr(VI)and Mn(II). The experiment was conducted in two ways: pre-treated method and simultaneous method. In the pre-treated method, at pH=4, the final removal percentage of Cr(VI) was 114.3%, 116.1% and 102.5% compared with the control when Mn(II):Cr(VI) was 1:2, 1:1 and 2:1, respectively, meanwhile at pH=8, the final removal percentage of Cr(VI) was 56.8%, 87.6% and 88.5%. In the simultaneous method, at pH=4, the final removal percentage of Cr(VI) was 93.3%, 94.5% and 92.8% with the control when Mn(II):Cr(VI) was 1:2, 1:1 and 2:1, respectively. However, an interesting phenomenon was that at pH=8, the final removal percentage of Cr(VI) was 128.8%, 204.9% and 349.4% with the control. The results indicated that Mn(II) was not an inhibitor but an accelerant in the process of Cr(VI) removal by Fe₃O₄ nanoparticles.