Novel Granulation-Shaped Microwave Discharge Electrodeless Lamps Setup for the Photodegradation of an Aqueous 1, 4-Dioxane Solution

A novel setup of granulated microwave discharge electrodeless lamps (MDELs) fabricated using vacuum UV-transparent quartz envelopes was used for treating wastewater, which in the present case was an aqueous solution of 1, 4-dioxane. The granulated MDELs were assessed in the self-ignition of the lamps on irradiation of low microwave power and in the wastewater photodegradation. 1, 4-Dioxane was photodecomposed in a flow reactor containing 20 of such MDELs. The photodegradation was analyzed by decreasing of 1, 4-dioxane concentration and total organic carbon (TOC). A conventional rod-shaped MDEL and a commercial low-pressure mercury lamp electrode were used to compare the performance of the novel granulated MDELs. The dominant performance of the MDELs was established by measuring the photodegradation rate per surface area of the irradiated wastewater and the applied electric power of the lamps. The decomposition dynamics of 1, 4-dioxane was investigated further using the number of passes through the flow reactor with the 20 MDELs under 80 W of microwave power. The photodegradation of 93% was achieved by passing wastewater through the flow reactor three times. Photodegradation intermediates were analyzed by the LC-MS technique. Basically, the photodegradation of 1, 4-dioxane occurs by the ·OH radical attack of the ring, which then leads to ring opening.