Enhancement of Zero Valent Iron particles Dispersion

• Main Authors: Wen-chi Chang, 張文奇
• Other Authors: Li-chu Tsai
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/20107656965800882118

碩士 === 嘉南藥理科技大學 === 環境工程與科學系暨研究所 === 98 === The direct injection of zerovalent iron (ZVI) nanoparticles into the contaminated subsurface aquifer has attracted interests in recent years such as direct decontamination of polluted plume in groundwater zone, environment friendly, and reducing remediation cost. However, the synthesized ZVI nanoparticles with sodium borohydride could aggregate quickly with van der waals or magnetic forces from nano scale into micro scale or larger and attracted in the soil surface layer when it were transported through the soil holes. To improve the migration distance and prevent the aggregation of ZVI nanoparticles, surface modifiers are used to reduce the ZVI nanoparticles sizes, to stabilize the ZVI nanoparticles and to enhance the transportation efficiency through groundwater layer. Single type surface modifiers (SDBS, SDS, CMC, PAA, PEI, PVG, PVP, PSS, alginic acid, sodium alginate and gelatin) and mixed type surface modifiers (CMC mixed PAA), have been employed to maintain the dispersion of ZVI particles which were prepared with borohydride reduction method of ferric ion. Dynamic light scattering (DLS) analyses, UV-vis spectrophotometry, and zeta potentiometry are used to characterize the ZVI nanoparticles which were disperzed with various concentrations of surface modifiers at different pH. The effects of ionic strength (Na＋, Ca2＋) on NZVI dispersion in suspension and the migration efficiency of stabilized ZVI through sand column were also discussed. CMC, PAA, Sodium alginate, and PSS could modify, reduce and disperse the ZVI nanoparticles into 6.3, 5, 6, and 20.8 nm in diameters, respectively. Comparison with bare ZVI particles without modification of surface modifiers, the migration efficiency of stabilized ZVI through water saturated sand column, increased as high as 26.47, 24.47, 29.91, 9.73 times for CMC, PAA, Sodium alginate, and PSS, respectively. Mixed surface modifier (4 × 10-6 M CMC +1.26 × 10-3% PAA) can disperse the ZVI particles in average number-weighted particle size of 16.1 nm. Dispersion with single (0.0063% PAA, 2 × 10-6 M CMC) or mixed surface modifiers (0.0063% PAA +4 × 10-6 M CMC), the addition of ionic strength (Ca2 + and Na+) will aggregate the ZVI nanoparticles into larger size, no matter what the addition of sodium borohydride before or after the Ca2 + and Na+。