Pentachlorophenol (PCP), found in wood preservatives and pesticides, is an acutely toxic recalcitrant organochlorine carcinogenic compound. A point-to-plane glow discharge plasma (GDP) process was used to study the destruction of 30-50 ppm (120-188 µM) sodium salt of pentachlorophenol (PCP) in an aqueous solution. PCP was converted to less than 10% of its initial concentration in 1-3 h, at room temperature and low pressure (50 Torr). Effects of varying the headspace gas chemistry, stirring rate, pH, and current upon rate of PCP conversion were investigated. Organic acids, including formate, acetate, butyrate, and oxalate, were formed as byproducts after 1-3 h of GDP treatment of PCP. The chloride recovery suggests 50-70% dechlorination. The PCP removal rate exhibited mixed order kinetics. A reaction model developed to verify mixed order kinetics compares well with the experimental data. The increase in order may be due to the production and subsequent destruction of several reaction products throughout the process. An increase in current and stirring rate increased the rate of PCP removal in the GDP reactor. However, the rate of PCP removal decreased when the initial pH of the solution is raised to 11.4. Rapid removal of PCP was observed when the headspace gas was argon, air, or oxygen. Bench scale data was used to compare the power efficiency of the GDP process with atmospheric pressure corona discharge. Results suggest that the cost of power for PCP conversion by glow discharge was less than that of atmospheric pressure corona discharge. Additionally, the operating cost for PCP destruction in aqueous solution using UV based advanced oxidation technologies was found to be comparable with power costs for PCP conversion using GDP.

No abstract

No abstract

No abstract

To support the selection of a waste form for the liquid secondary wastes from the Hanford Waste Immobilization and Treatment Plant, Washington River Protection Solutions (WRPS) has initiated secondary waste form testing on four candidate waste forms. Two of the candidate waste forms have not been developed to scale as the more mature waste forms. This work describes engineering-scale demonstrations conducted on Ceramicrete and DuraLith candidate waste forms.Both candidate waste forms were successfully demonstrated at an engineering scale. A preliminary conceptual design could be prepared for full-scale production of the candidate waste forms. However, both waste forms are still too immature to support a detailed design. Formulations for each candidate waste form need to be developed so that the material has a longer working time after mixing the liquid and solid constituents together. Formulations optimized based on previous lab studies did not have sufficient working time to support large-scale testing. The engineering-scale testing was successfully completed using modified formulations. Further lab development and parametric studies are needed to optimize formulations with adequate working time and assess the effects of changes in raw materials and process parameters on the final product performance. Studies on effects of mixing intensity on the initial set time of the waste forms are also needed. v SummaryThe Hanford Site in southeast Washington State has 56 million gallons of radioactive and chemically hazardous wastes stored in 177 underground tanks (DOE 2010). The U.S. Department of Energy (DOE), Office of River Protection, through its contractors, is constructing the Hanford Tank Waste Treatment and Immobilization Plant (WTP) to convert the radioactive and hazardous wastes into stable glass waste forms for disposal. Within the WTP, the pretreatment facility will receive the retrieved waste from the tank farms and separate it into two treated process streams. These waste streams will be vitrified, and the resulting waste canisters will be sent to offsite (high-level waste [HLW]) and onsite (immobilized lowactivity waste [ILAW]) repositories. As part of the pretreatment and ILAW processing, liquid secondary wastes will be generated that will be transferred to the Effluent Treatment Facility (ETF) on the Hanford Site for further treatment. These liquid secondary wastes will be converted to stable solid waste forms that will be disposed in the Integrated Disposal Facility (IDF).To support the selection of a waste form for the liquid secondary wastes from WTP, Washington River Protection Solutions (WRPS) has initiated secondary-waste-form testing work at Pacific Northwest National Laboratory (PNNL). In anticipation of a down-selection process for a waste form for the Solidification Treatment Unit to be added to the ETF, PNNL is conducting tests on four candidate waste forms for stabilizing and solidifying WTP liquid secondary wastes:• Cast Stone Portland-cement-based waste form• Ceramicrete phosphate-b...