Blue is the colour for ozone-loaded solids
15 Jan 2000
The technique of using ozone to disinfect water has been around for many years, and produces high-purity water without the environmental problems associated with chlorine disinfection. But it still has problems bubbling ozone through water is an inherently inefficient way of using the gas, because it's hardly soluble in water. Researchers in the chemical engineering and chemical technology departments of the University of Bradford are trying to find ways of avoiding this problem.
The team's work involves adsorbing the gas onto the surface of various solids. The theory, they explain, is that a layer of ozone on a surface is a more 'concentrated' environment for the gas to exert its oxidising power than simply floating free in solution.
Chemists already use ozone adsorbed onto silica gel to perform specific oxidations in organic synthesis, the team explains, so the techniques already existed. The team sent dried oxygen from a pressurised cylinder through an electrical ozoniser and into a silica gel-containing adsorption column. The gel turns blue when it adsorbs ozone, they comment; the shade darkens as more gas is adsorbed.
The team then used the ozone-carrying gel to decolorise a reactive red dye. Using uv spectroscopy, they found that 10g of silica loaded with 0.031g of ozone bleached the dye completely in 20min, whereas gaseous ozone at a flow-rate of 0.35mg/s achieved the same result in 10min (consuming 0.21g of ozone, almost seven times as much as the adsorbed-gas experiment).
