Engineering-scale Experiments Of Solar Photocatalytic Oxidation Of Trichloroethylene

Abstract

A photocatalytic process is being developed to destroy organic contaminants in water. Tests with a common water pollutant, trichloroethylene (TCE), were conducted at the Solar Thermal Test Facility at Sandia with trough systems. Tests at this scale provide verification of laboratory studies and allow examination of design and operation issues that only arise in experiments on a realistic scale. The catalyst, titanium dioxide (TiO/sub 2/), is a harmless material found in paint, cosmetics and even toothpaste. We examined the effect of initial contaminant concentration and the effect of hydrogen peroxide on the photocatalytic decomposition of trichloroethylene (TCE). An aqueous solution of 5000 parts per billion (ppb) TCE with 0.1 weight% suspended titanium dioxide catalyst required approximately 4.2 minutes of exposure to destroy the TCE to a detection limit of 5 ppb. For a 300 ppb TCE solution the time required was only 2.5 minutes to reach the same level of destruction. Adding 250 parts per million (ppm) of hydrogen peroxide reduced the time required by about I minute. A two parameter Langmuir Hinshelwood model was able to describe the data. A simple flow apparatus was built to test four fixed catalyst supports and to measure their pressure drop and assess their ability to withstand flow conditions typical of a full-sized system. In this paper, we summarize the engineering-scale testing and results.