Purification treatment agent and purification treatment method

A purification treatment agent and a purification treatment method which are excellent in the removal performance of heavy metals mainly containing cadmium are provided. The purification treatment agent of the present invention is a purification treatment agent for removing cadmium from contaminated water or contaminated soil and is characterized by containing a metal powder containing iron or an alloy and a non-metallic reducing agent. The raw material of the non-metallic reducing agent may be sodium thiosulfate, ascorbic acid, urea, anisole or a combination thereof. The metal powder may be atomized powder. The metal powder may contain sulfur. The sulfur content of the metal powder is preferably 0.05% by mass or more and 5% by mass or less. The mass ratio of the content of the non-metallic reducing agent to the metal powder is preferably 0.01 or more and 4 or less. The purification treatment method of the present invention is a purification treatment method for removing cadmium from the contaminated water or