Recovery of Silver from X-Ray Film Processing Effluents Using Trimercapto-s-triazine (TMT)

Abstract

In this study, the recovery of silver from waste X-ray photographic solutions by precipitation using trimercapto-s-triazine (TMT) was studied. Taguchi L₂₅ (5³) orthogonal design was adopted for the study. The effects of concentration of thiosulphate (5.2–200 g/L), TMT (Ag:TMT = 6.6–2.2), temperature (20–60°C) and pH (4.37–8.00) on the extent of the precipitation of silver were investigated. The findings have shown that the concentration of TMT and pH are the most significant factors affecting the recovery of silver while the effect of temperature (20–60°C) is insignificant under the conditions tested. The increase in the concentration of TMT and pH was found to improve the extent of precipitation of silver. TMT was also found to be an effective agent to reduce silver concentrations below the regulatory limit value of 5 ppm. Characterization of the precipitates was performed to identify silver-TMT compounds formed.

Keywords:

• precipitation
• recovery
• silver
• Taguchi
• Trimercapto-s-triazine (TMT)
• waste treatment

ACKNOWLEDGEMENTS

The authors would like to express their sincere thanks and appreciations to the Research Foundation of Karadeniz Technical University (KTU) for the financial support (Project no: 2006.112.008.1), to Mr. Fatih Erdemir (Dept. of Metallurgical&Materials Eng., KTU) for SEM-EDS analysis, to Mr. Ismail Polat (Dept. of Physics, KTU) for XRD analysis, to Dr. Ali Gündoğdu (Dept. of Food Eng., Gümüşhane University) for IR analysis, and to Degussa (now Evonik) Industries for kindly providing the TMT 15 reagent.

Notes

*Original pH of the solution. No addition of NaOH.

*Original pH of the solution. No addition of NaOH.