Degradation of Estradiol in Water and Soil Using a New Class of Stabilized Manganese Dioxide Nanoparticles and Hydrodechlorination of Triclosan Using Supported Palladium Catalysts

Abstract

Pharmaceuticals and personal care products (PPCPs), such as 17 beta-estradiol (E2) and triclosan (TCS), are endocrine disruptors that have been found in surface water and groundwater. The low concentration of these endocrine disrupting chemicals can cause adverse effects on humans and wildlife via interactions with their endocrine system. To facilitate in-situ remediation of E2 in groundwater, this research developed a new class of stabilized manganese oxide nanoparticles using “green” and low-cost carboxymethyl cellulose (CMC) as a stabilizer. The most mono-dispersed MnO2 nanoparticles were obtained at a CMC/MnO2 molar ratio of 1.39*10-3, which yielded a mean hydrodynamic size of 39.5*0.8 nm. The CMC-MnO2 nanoparticles could effectively degrade E2 in both aqueous and soil phases. Column transport tests confirmed that the nanoparticles can be delivered through three natural sandy loams, although retention of the particles varied with soils. The particle retention is strongly dependent on injection pore velocity, and in-situ treatment effectiveness is strongly affected by the mass transfer rates of both the nanoparticles and contaminants. When the E2-laden soils were treated with 0.17 g/L of the MnO2 nanoparticle suspension, 13-88% of water leachable E2 was degraded, depending on the soil type. The nanoparticles appear to be promising in terms of filling the technology gap for in-situ oxidation of endocrine disruptors in soil and groundwater. This study also developed and tested a new class of supported Pd catalyst by immobilizing the Pd particles on two strong basic anion exchange resins (IRA-900 and IRA-958). The resin-supported Pd catalysts could facilitate a rapid and complete hydrodechlorination (HDC) of TCS with very low concentration of chlorinated intermediates were present in the very early stage of HDC process. These resin supported catalysts showed long-term sustainability with only < 2% reactivity lost after eight exhausting runs, which contribute to the advantage of minimum Pd bleeding from the supports and high resistance to organic fouling. Catalytic HDC with resin-supported Pd catalysts have proved to be a promising solution for completely degrade the chlorinated pollutants and diminish highly toxic byproducts produced by other degradation methods.