Method of decomposing organic halide

A method for decomposing an organic halide, comprising:

• providing a microwave plasma generator comprising:
• a rectangular waveguide having a hole to transmit a microwave,
• a coaxial microwave cavity connected to said rectangular waveguide by communicating with the hole, and including a cylindrical outer conductor and a cylindrical inner conductor disposed in said cylindrical outer conductor coaxially therewith,
• a discharge tube which is made of a dielectric material, extends through the hole of said rectangular waveguide, and extends through said cavity so as to be coaxial with a central axis of said cavity, and
• an ignition member connected with ignition power supply,
• wherein said discharge tube has a double-tube structure including outer and inner tubes, a sectional area of an annular gap formed between said outer and inner tubes is constant over an entire length of said inner tube, and an end portion of said inner tube has a gas injection opening having the same diameter as an internal cavity of said inner tube;
• supplying a gas containing an organic halide, water vapor, and air into the annular gap formed between said outer and inner tubes;
• and
• allowing said ignition member to discharge by operating said ignition power supply, generating a plasma in said outer tube, which plasma extends from the vicinity of the end portion of said inner tube toward an end portion of said outer tube, thereby decomposing the organic halide.