PHYSICAL-CHEMICAL PARAMETERS INFLUENCING ELEMENTAL IRONMEDIATED REDUCTION OF THE AZO DYE ORANGE G

Batch and column reduction experiments were performed with the azo dye orange G to determine changes in the performance of iron pretreatment process as solution variables were altered. The effects of iron type and surface area, solution pH, dissolved inorganic salts, and phosphate ions on reduction (decolorization) of orange G solutions were examined. In batch experiments, increased iron surface area, decreased pH, and chloride and sulfate salts enhance dye decolorization. High pH (> pH 9) and potassium phosphate (> 3 mg/L PO43--P) inhibited dye reduction. Column experiments were performed to assess more accurately treatment efficiency in continuous-flow experiments. Chloride and phosphate ions had similar effects on reduction efficiency in batch and column experiments. Column studies were also performed to determine the effect of temperature – an increase from 22°C to 35°C resulted in a near doubling of the reduction rate constant. Abiotic reduction data are indicators of the feasibility of an integrated iron column-activated sludge treatment process for wastewaters containing azo dyes.