In order to design a recovery process of phosphorous acid from the wastewater of electroless nickel-plating, the extraction of phosphorous acid in the aqueous solution with tri-n-octylamine in toluene was carried out using a vibration type continuous extractor, which has multiple vibration disks in a cylindrical tube. The effects of the initial concentrations of the extractant and phosphorous acid and the mean residence time of both solutions in the extractor on the extraction rate of phosphorous acid were measured under various conditions. The experimental results correlated to the complete mixing flow of both fluids in the extractor were analyzed based on the apparent rate equation of (2.0, 2.0)th orders for the acid and the amine. The calculated results for each frequency number of the vibration plates were in good agreement with the experimental results.

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In order to construct a practical extraction recovery process of organic, phosphorous and hypophosphorous acids from wastewater of electroless nickel-plating with tri-n-octylamine in toluene, a closed circulation type continuous extraction equipments with the extraction and the back-extraction steps were developed. Two equipments, which were a laboratory scale having 30 ml reactor and a pilot plant scale having 450 ml reactor, were constructed with reactors having multiple vibration disks in a cylindrical tube for extraction and back-extraction, the settler for oil/water separation and the metering pump for transportation of the organic and the aqueous phase. The effect of pH and its control in the aqueous phase on these acids extraction were investigated using the laboratory scale equipment. The experiments using the pilot scale equipment, whose experimental condition was selected based on the acids extraction behavior in the laboratory scale equipment, was done to determine the practical conditions. In the treatment of a spent electroless plating bath using the pilot scale equipment, the treatable volume of the wastewater was 210 L/24 hr, and the recovered mass for hypophosphorous acid and phosphorous acid were 3.4 kg and 1.1 kg for 24 hr.

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In Japan, low-level radioactive wastes discarded by research institutions and hospitals are packed into containers and stored. Volume reduction by incineration and compression processing are sometimes attempted; alternatively, the wastes are left in an unprocessed state because neither landfill sites nor disposal methods have been established. Especially, low-level radioactive waste incineration ash presents great problems of security, safety, and stability in inventory location. A safe and appropriate disposal processing method is desired because the bulk density of ash is low; the ash is also easily dispersed. Volume reduction and stabilization for low-level radioactive waste incineration ash were verified for low-temperature sintering method using glass bottle cullet. The proposed method was useful for easy treatment of low-level radioactive waste incineration ash. This report describes the difference between soda lime glass (cullet) and borosilicate glass for the RI ash sintering, and characteristics of RI volatilization and elution from the sintered radioactive waste pellets. The borosilicate glass is used for glass melt solidification of high-level radioactive waste.

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