Glass fiber reinforced plastics (GFRP) are composite materials with high strength and flame retardancy, and the disposal process is expensive to cause illegal dumping. Therefore, new recycling technology of waste GFRP are desired. In this study, recycling of waste GFRP using pyrolysis with sodium hydroxide (NaOH) under an inert atmosphere was attempted by gasification and carbonization of resin and conversion of glass fiber into soluble sodium silicate. The pyrolysis behavior of GFRP, the characteristics of the obtained residue, the composition and the yield of generated gas, and the silica extraction into the solution were investigated. The gasification and carbonization of the resin and the conversion of the glass fiber into soluble sodium silicate were promoted by pyrolysis with NaOH. Further, it was found that the sample after the pyrolysis treatment can be pulverized into a powdery residue by washing the solution without mechanical crushing. It was confirmed that the gas yield, especially flammable gases (H₂ and CH₄), and the silica extraction increased and the residual ratio decreased, with increasing heating temperature, NaOH addition and heating time. When 1 M HCl was used for extraction, a decrease in residual rate, an increase in silica and calcium extraction, and an increase in specific surface area of the residue for using adsorbent were achieved, compared to using distilled water, HNO₃ and H₂SO₄.

The demand for PGMs is increasing year by year due to their excellent physical and chemical properties. Moreover, in order to meet the demand, it is important to develop a highly efficient recovery process of PGMs from secondary resources. Solvent extraction applied to refining process for PGMs offers several advantages over the traditional precipitation methods and distillation. Solvent extraction efficiency of Rh and Ru from chloride solutions is very low. However, the extraction efficiency of Rh and Ru can be improved by adding Sn(II) to chloride solutions.

In the present study, the extraction of Rh and Ru from hydrochloric acid solutions with tri-n-octylamine (TOA) and tri-octyl methyl ammonium chloride (TOMAC) diluted with benzene were tested to clarify the effect of addition of Sn(II) on the extraction of Rh and Ru and stripping of Rh and Ru. The addition of Sn(II) was effective for the extraction of Rh and Ru and the stripping of Rh and Ru with solutions of sodium nitrite prepared with sodium hydoxide was effective.

Steel converter slag, a by-product of iron- and steel-making plants, was converted into a hydrogarnet-containing product using the alkali fusion method. The converter slag was transformed into an alkali-fused slag with reactive phases via alkali fusion using sodium hydroxide at 600°C for 6 h, after which the fused slag was stirred in distilled water at ambient temperature to prepare a precursor to synthesize a product, comprising hydrogarnet, by heating the precursor at 80°C. This product could remove HCl gas at a high temperature (800°C) and showed higher Cl fixation than slag and lime. These results suggest that a novel product capable of removing HCl gas at high temperatures can be synthesized from converter slag via alkali fusion.

There is an increasing trend in the copper smelters to recycle electronic materials, which contain relatively high concentration of silver. Silver lost in the slag is increasing with increasing of treated scrap amount. To determine the portion of the silver chemically dissolved in the slag will be a key factor to improve the recovery of silver.

An experimental study was carried out to determine the solubility of silver in the FeO_x-SiO₂ slag equilibrated with a pure liquid silver and the molten Ag-Cu alloys at 1573K in the range of oxygen partial pressure from 10^–9 to 10^–6 as an oxygen activity. The solubility of silver in the slag tends to increase with increasing oxygen partial pressure and the activity of Ag in the alloys. Therefore, lower oxygen partial pressure and lower concentration of silver in the metal phase tend to lower silver dissolution in the slag. Based on the measured silver solubility and the oxygen partial pressure, activity coefficients of silver oxide in the FeO_x-SiO₂ slag were derived. The activity coefficients of AgO_0.5 in iron silicate slag show a constant value regardless of the oxygen partial pressure and the copper concentration in the slag. We found that AgO_0.5 and CuO_0.5 in the FeO_x-SiO₂ slag behaved as ideal relation from the derived activity coefficient of AgO_0.5.