Removal and recovery of phenol from FCC effluent

Effluent from the FCC process contains considerable concentrations of phenol, sulfide and ammonium ions. The pH of the effluent is around 9. In the present study, the possibility of the application of anion exchange membranes for its removal and recovery, was investigated. The equilibrium constant between phenol and hydroxide ions and the ion exchange capacity of a commercial anion exchange membrane were determined. The membrane was sandwiched between two glass cells filled with a phenol solution at pH 9, fed and withdrawn continuously to keep the phenol concentration constant, and a sodium hydroxide solution at various pH, respectively. The permeation rate increased with pH and reached a plateau at above pH 13. The permeation rate was measured for various concentrations of phenol in the feed side, keeping the pH of the strip side at 13. The rate linearly increased with the phenol concentration and reached a plateau at concentration greater than 1 mol/m³. The apparent diffusion coefficient of phenol in the membrane was determined from the plateau value. At a concentration of less than 1 mol/m³, the rate was found to be controlled by boundary film resistance. It was also found that the permeation rate of phenol was suppressed by the sulfide ion at a concentration comparable to or larger than that of phenol.