Advanced Treatment Of Dyeing Wastewater With Fenton-like Reaction Catalysted By Pyrite Cinder

Mineral Fenton-like technique hasthe advantages of low reagent dosage, wide reaction range of pH value, less mud quantity and the best reutilization ability, comparedwith the traditional Fenton reaction. It has been paid highly attention to apply this technique to wastewater treatment and water reuse. Pyrite cinder is one of the potential Fenton-like catalysts and deserves to be studied about its performance in dyeing wastewater treatment.In this paper, pyrite and pyrite cinder are chosen to catalyse hydrogen peroxide to degrade acid scarlet GR. Pyrite is a very effective catalyst to introduce Fe3+, Fe2+and other ions to increase the decomposition of hydrogen peroxide. Influencing factors, such as pH, reagent dosage and reaction time were studied to show their effects on the decoloration rate. Preparation of Bi-PyC and its characterization were also investigated to prove its high catalytic potential.The comparative study of the economic costs between Fenton-like and traditional Fenton techniqueswascarried out, and the experiment results were used as one of the most important index in application. Detailed procedures and results are as follows:In Fe3+/H2O2system the pH value was proved to be the most important factor on degradation of acid scarlet GR, hydrogen peroxide dosage and Fe3+dosage followed. Acid scarlet GR of50mg/L could be effectively degraded by0.1mL/L hydrogen peroxide and25mg/L Fe3+with pH value of3. Among acid system, Fe2+is generated instantly by Fe3+, which shows better decoloration performance catalysted by Fe3+.Bi-PyC had an advantage over unloaded pyrite cinder in reagent dosage and reaction time. At pH value of3, Acid scarlet GR of50mg/L get90.1percent decomposed by0.1mL/L hydrogen peroxide and5g/L unloaded pyrite cinder within120minutes, while same decoloration rate gains with just0.05mL/L hydrogen peroxide and2g/L Bi-PyC within10minutes. Unloaded pyrite cinder could be reused at pH3with reaction time of90minutes, pyrite cinder (450’C calcination) could be reused after10-minute reaction with pH ranging from3to5and the decoloration over90percent. Pyrite cinder (450℃calcination) hadthe potential to decompose40pecent acid scarlet GR even when the pH value was6.SEM, XRD, EDS and other techniques were applied to characterize the pyrite cinder. The results showed its amorphous block among surface, transfering to spherical surface with accumulation after Bi-loaded. Unloaded samples’BET value was as low as0.8m2/g. XRD and IR data indicated that the crystal structure of cataltst changed from Fe3O4to Fe2O3·Bi-loaded process could improve the ion dissolution of catalyst and then cause pH decline. Dissolved Fe3+had coupling effects of pyrite cinder on decoloration.The average cost of COD treatment was introduced to compare the difference between mineral Fenton-like and traditional Fenton reaction. It was shown as the total reagent cost per unit weight of COD. By Fenton-like method, COD droped from129mg/L to53.8mg/L with the hydrogen peroxide dosage of0.15mL/L, costing0.0133yuan/g, while costing0.0199yuan/g by the traditional way. In actual wastewater treatment, Bi-PyC needed shorter time of4h than24h of the unloaded one.This study provided a new Fenton-like way to decompose dyeing wastewater, which showedthe feature of high catalytic activity, low reagent dosages and wide pH range. Pyrite cinderwould make a contribution to promotethe application of mineral Fenton-like technique to the large-scale engineering in the near future.