Recovery of precious metals from spent catalysts due to the limited resources of these metals and the reduction of environmental hazards due to the presence of catalysts used in the environment, has been considered by many researchers. In this study, chloride leaching method was used as an environmentally friendly method to recover platinum from the catalyst used in Kermanshah refinery. First, the potential of some leaching agents including hydrochloric acid, sodium hypochlorite, hydrogen peroxide, iron chloride, copper chloride, aluminum chloride, aluminum nitrate, sodium chloride, ammonium chloride to dissolve platinum was eva‎luated. Leaching in chloride medium facilitated the dissolution of platinum and reduced acid consumption due to the tendency of platinum to form complexes with chlorine ions. The highest percentage of Pt recovery in this study was about 97.5% by 5 M hydrochloric acid and 1% hydrogen peroxide at 70 °C. But to reduce acid consumption, chloride leaching method was selected using hydrochloric acid, sodium chloride salt and iron chloride. The experiments were designed using the response surface methodology and the Box-Benken design. Three factors of hydrochloric acid concentration, iron chloride and temperature were considered as variables in the design. The results showed that with increasing temperature from 70 to 90 ° C, the recovery of Pt increased and the recovery of Pt from about 52% at 70 ° C and the concentration of one molar of hydrochloric acid to a maximum recovery of 88.5% at 90 ° C and The concentration reached three molar acid. Therefore, increasing the concentration of hydrochloric acid to a concentration of 3 M increased the recovery of Pt. Increasing the concentration of iron chloride in low concentrations of acid increased the recovery of Pt and in concentrations of acid higher than two molar, decreased the recovery rate. Thus, at a constant concentration of two molar hydrochloric acid and a temperature of 80 ° C, the recovery of 0.7 to one molar of iron chloride of platinum recovery decreased from 78% to 73% and from a concentration of 1 to 1.3 M, the recovery of platinum to about 76% Increased. The highest recovery of platinum was 88.5% at a concentration of one molar of iron chloride, a concentration of three molar hydrochloric acid and a temperature of 90 ° C. Finally, the platinum in the leaching solution was precipitated as ammonium hexachloroplatinate by ammonium chloride saturated solution. In order to extract platinum with higher purity, the method was extracted with organic solvent trioctylamine (TOA) and precipitated preparation using ammonium chloride and ammonia solution was used. According to X-ray diffraction (XRD) analysis, the platinum in both sediments from both precipitation methods was detected as the ammonium hexa chloroplatinate salt. In the best case, the salt produced was obtained by direct precipitation with ammonium chloride with an enrichment ratio of about 72 compared to the catalyst used and with a purity of 18% Pt.

محمدرئوف حسيني، اكبر زمانيان

علي احمدي عامله

مهدي نصيري سروي، حميد زيلويي