Study Of Biorefractory Of Ozonation In A Membrane Reactor

Ozone, due to its characteristics of powerful oxidation ability and rapid react with organic compounds, has been used as a chemical oxidation to treatment drinking. But its applications to wastewater has been limited, the main reason is the ozone's diffusion coefficient and solution rate in water is relatively low, which make the proportion of reacting with organics is low. Conventional ozone contacting methods, such as bubble columns, impellers, injectors, and others, bring the gas and water contact directly. These methods suffer from excessive formation of foam, the chemical foam inhibitions can suppress the formation of foam, but the application of chemical foam inhibition will lead to a additional pollution.The hollow fiber membrane, which can provided magnitude large contacting surface area per unit volume, can reduced mass-transfer resistance effectively and offer higher transfer rate than conventional contacting methods. Past studied have demonstrated the membrane-based contacting method can greatly increase a over conventional gas absorption tower (30 cm~-1 for membrane devices compared to 0.1-4cm~-1 for plate columns). The experiment studied the ozonation in the hollow fiber membrane reactor, and investigated some factors which the removal rate depends on.The experiment showed the contamination was decomposed effectively in the membrane reactor. When the conditions were favorable, the removal rate was 93%. The factors which was investigated affect the removal rate in different degrees. An increasing of pH will lead to a great increase of removal rate, but when the initial pH was above 9.5, the increase become unconspicuous. Increasing the ozone flow rate and the liquid flow rate will make the ozonation quick due to the transfer resistance be reduced. The higher initial concentration contamination will yield much secondary products which includes much organic acid, these compounds not only decrease pH of liquid phase but also exhaust ozone, the removal efficiency become lower. The higher concentration of ozone can increase the contamination removal efficiency though increasing the impetus of transfer.Mathematical model were developed to study the characteristic of gaseous ozone transfer coupled with reaction process. Five processes were simulated: the evolution of ozone concentration in lumen side, the evolution of ozone concentration in the shell side, the evolution of ozone concentration in the vessels, the evolution of the contamination concentration in shell side, the evolution of the contamination concentration in the vessel. The model was solved numerically by using the finite-difference method, and the parameters were determined by using experimental data. The values of transfer rate, constant rate and the attenuation coefficient were calculated. The results showed the increase of the gas flow rate and aqueous flow rate led to the increase of the transfer rate. The attenuation coefficient and the constant rate depend on the pH, the pH rise will lead to the increase of attenuation coefficient and constant rate.