TREATMENT OF PHOTOGRAPHIC EFFLUENTS BY ELECTROCHEMICAL METHOD

Fixing and bleach/fixing solutions from photographic process were trea ted in this investigation by an electrochemical reduction process for silver recovery and oxidation process to reduce chemical oxygen demand (COD) levels. The COD oxidation process was undertaken after the silv er recovery process. According to these results, silver recovery rate from bleach/fixing solution depends heavily on pHs, whereas the nature of silver deposit from fixing solution is sensitive to cathode potent ial. The GOD, NH4+-N, and total organic carbon (TOC) removal rates fro m both fixing and bleach/fixing solutions were also examined by electr ochemical oxidation at a IrO2 + RuO2/Ti anode with and without the add ition of NaCl. In the fixing solution, the oxidation rate of inorganic compounds is faster than that of organic compounds. Under the operati ng conditions, a current density of 10 A/dm(2), and by adding 5% NaCl, about 90% of the COD and NH4+-N in the fixing solution was removed af ter electrolysis for 10 h. For a bleach/fixing solution, the COD remov al rate was independent of the addition of NaCl; meanwhile, the NH4+-N removal rate increased with addition of NaCl. Under the operating con ditions of 10 A/dm(2) current density and the addition of 5% NaCl, ove r 95% of COD was removed after electrolysis for 10 h. At the same time , 42,000 mg/L NH4+-N was also completely removed.