Final Report - Strategic Environmental Research and Development ...

6. MATERIALS AND METHODS6.1. Factors Controlling the Decomposition of Persulfate in the Subsurface6.1.1. Persulfate Activation by Major Subsurface MineralsChemicalsSodium persulfate, sodium citrate, and hexachloroethane (HCA) were purchased fromSigma Aldrich (St. Louis, MO). Sodium hydroxide, sodium bicarbonate, potato starch, andnitrobenzene were obtained from J.T. Baker (Phillipsburg, NJ). Sodium thiosulfate, potassiumiodide, and n-hexane were purchased from Fisher Scientific (Fair Lawn, NJ). Hydrogen peroxidewas provided by Great Western Chemical (Richmond, CA). Sodium dithionate was purchasedfrom EMD Chemicals (Darmstadt, Germany). Hydroxylamine hydrochloride was purchasedfrom VWR (West Chester, PA). Double-deionized water was purified to > 18 MΩ•cm using aBarnstead NANOpure II Ultrapure system.MineralsSix minerals were investigated for their potential to activate persulfate: goethite[FeOOH], hematite [Fe 2 O 3 ], ferrihydrite [Fe 5 HO 8 •4H 2 O], birnessite [δ-MnO 2 ], kaolinite[Al 2 Si 2 O 5 (OH) 4 ], and montmorillonite [(Na,Ca)(Al,Mg) 6 (Si 4 O 10 ) 3 (OH) 6 •nH 2 O]. Goethite andhematite were purchased from Strem Chemicals (Newburyport, MA) and J.T. Baker(Phillipsburg, NJ), respectively. Ferrihydrite was purchased from Mach I (King of Prussia, PA).Birnessite was prepared by the dropwise addition of concentrated hydrochloric acid (2 M) to aboiling solution of 1 M potassium permanganate with vigorous stirring (Mckenzie, 1971).Montmorillonite and kaolinite were provided by the Clay Minerals Society (West Lafayette, IN).Examination of the X-ray diffraction pattern confirmed the minerals were the desired iron andmanganese oxides. Mineral surface areas were determined by Brunauer, Emmett, and Teller(BET) analysis under liquid nitrogen on a Coulter SA 3100 (Carter et al. 1986). Particle sizedistribution of the minerals was determined by the pipette method (Gee and Bauder, 1986) and islisted in Table 6.1.1.1.Table 6.1.1.1. Particle size distribution (PSD) of mineralsPSD (mm) Goethite Hematite Ferrihydrite Birnessite Montmorillonite Kaolinite2.00 - 0.05 0.12% 2.40% 0% 2.40% 8.10% 8.10%0.05 - 0.002 8.24% 89.10% 0% 5.60% 40.10% 56.10%