Recovery of nano-magnetite from silica/magnetite aggregates in magnetic seeding aggregation of CMP wastewaters

• Main Authors: Li-Jen Wang, 王立仁
• Other Authors: Ching-Ju Chin
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/25493854426623949028

碩士 === 國立中央大學 === 環境工程研究所 === 93 === Magnetic seeding aggregation has been developed to remove silica nanoparticles from CMP wastewaters successfully with removal efficiency of turbidity higher than 95 %. With proper treatments, seeded magnetite (Fe3O4) nanoparticles can be reused repeatedly in the magnetic seeding aggregation of CMP wastewaters. In this study, the recovery of magnetite nanoparticles by different types and concentrations of surfactants and removal efficiency of total silicon (e.g. summation of silica nanoparticles and silicate) from CMP wastewaters treated by reused seeding particles were investigated. Experimental results showed that recovery of magnetite nanoparticles was always higher than 99% when silica/magnetite aggregates were treated by any SDS or CTAB concentrations used in this work (0.1 ~ 2 CMC). Though the addition of CTAB limited the separation between silica and magnetite nanoparticles, this improved the reusability of magnetite nanoparticles, which was due to lateral interactions of hydrophobic groups of CTAB molecules adsorbed on the surface of silica nanoparticles. When silica/magnetite aggregates were treated by 0.1 CMC CTAB, the silicon removal ability of magnetite nanoparticles is 1917 mg total Si / 1g magnetite, which is 1497.5% more than those used only once in the magnetic seeding aggregation of CMP wastewaters. However, total silicon removal efficiency of CMP wastewaters was very poor when they were treated by high concentration (2 CMC) of CTAB or SDS. This might be due to the steric repulsions between particles resulted from adsorbed surfactant molecules.