Fumihiro Nishimura

Removal of lead from cathode ray tube funnel glass by combined thermal treatment and leaching processes.

The reduction melting process is useful to recover toxic lead from cathode ray tube funnel glass; however, this process generates SiO2-containing residues that are disposed in landfill sites. To reduce the volume of landfill waste, it is desirable to recycle the SiO2-containing residues. In this study, SiO2 powder was recovered from the residue generated by reduction melting. The funnel glass was treated by a process combining reduction melting at 1000°C and annealing at 700°C to recover a large quantity of lead from the glass. The oxide phase generated by the thermal treatment was subjected to water leaching and acid leaching with 1M hydrochloric acid to wash out unwanted non-SiO2 elements for SiO2 purification. In the water washing, the oxide phase was microparticulated, and porous structures formed on the oxide surfaces. This increased the surface area of the oxide phase, and the unwanted elements were effectively washed out during the subsequent acid leaching. By controlling the acid leaching time and the amount of added acid, porous and amorphous SiO2 (purity >95 wt%) was recovered. In the obtained SiO2-concentrated product, unrecovered lead remained at concentrations of 0.25-0.79 wt%. When the Na2CO3 dosage in the thermal treatment was increased, the lead removal by acid leaching was enhanced, and the lead concentration in the obtained product decreased to 0.016 wt%.

Phase separation of cesium from lead borosilicate glass by heat treatment under a reducing atmosphere

A phase-separation technique for removing sodium from glass using a heat-treatment method under a reducing atmosphere was previously developed for sodium recovery from waste glass. In this study, this technique was applied to cesium-containing lead borosilicate glass to concentrate the cesium in phase-separated sodium-rich materials for efficient cesium extraction. The theoretical phase-separation temperature of the sodium-rich phase was simulated by thermodynamic equilibrium calculations and was predicted to occur below 700°C for lead borosilicate glass. Experimentally, a simulated lead borosilicate glass was melted at 1000°C and subsequently annealed below 700°C under a CO-containing reducing atmosphere. The phase separation of cesium was found to occur with sodium enrichment on the glass surface that was in contact with the gas phase, promoting cesium extraction from the treated glass using water. The cesium extraction efficiency was affected by the surface area of the treated glass that was in contact with water, and under the examined conditions, the cesium extraction efficiency was up to 66%. Phase separation using reductive heat treatment, combined with a water leaching technique, is suggested to be effective for extracting cesium incorporated in borosilicate glass waste.

Recovery of palladium, cesium, and selenium from heavy metal alkali borosilicate glass by combination of heat treatment and leaching processes

Reductive heat-treatment and leaching process were applied to a simulated lead or bismuth soda-potash-borosilicate glass with palladium, cesium, and selenium to separate these elements. In the reductive heat treatment, palladium is extracted in liquid heavy metal phase generated by the reduction of the heavy metal oxides, whereas cesium and selenium are concentrated in phase separated Na-K-rich materials on the glass surface. From the materials, cesium and selenium can be extracted in water, and the selenium extraction was higher in the treatment of the bismuth containing glass. The chemical forms of palladium in the glass affected the extraction efficiencies of cesium and selenium. Among the examined conditions, in the bismuth glass treatment, the cesium and selenium extraction efficiencies in water were over 80%, and that of palladium in liquid bismuth was over 80%.

Structural analysis of cellulose acetate and zirconium alkoxide hybrid fibres

We investigated the detailed structures of organic–inorganic hybrid fibres composed of cellulose acetate (CA) and zirconium alkoxides (Zr(OR)4) using attenuated total refraction-Fourier transform infrared spectroscopy (ATR-FTIR), energy-dispersive X-ray spectroscopy (EDS), and X-ray absorption fine structure (XAFS) measurements. The fibres were prepared by an air-gap spinning technique, where the acetone solution of CA was injected into a Zr(OR)4–acetone bath. The Zr contents in the prepared fibres increased with increasing Zr(OR)4 bath concentration, but reached steady-state values at Zr(OR)4 bath concentrations above 10 wt%. In addition, EDS analysis for the cross-section of the fibre showed that Zr distribution in the fibre varied depending on Zr(OR)4 bath concentration and alkoxide type. ATR-FTIR and XAFS analysis showed that Zr contained in a CA fibre was hexacoordinated, with a local structure similar to that of hydrolysed Zr(OR)4. This result indicated that the confinement to the CA fibre had little influence on the local structure of Zr.