حذف رنگ از پساب با استفاده از فرآیند شبه‌الکتروفنتون ناهمگن کاتالیز شده با کاتالیست زئولیتی

کمبود منابع آبی و تخلیه فاضلاب به محیط زیست منجر به تحقیقات وسیعی در این حوزه به منظور توسعه فرآیندهای تصفیه فاضلاب پربازده، سریع و ارزان شده است. فرآیندهای اکسیداسیون پیشرفته بخاطر عملکرد بالا و آسان بودن فرآیند برای تصفیه فاضلاب بسیار مورد توجه قرار گرفته است. در این تحقیق کاتالیست ir-zsm-5 به روش هیدروترمال و تلقیح مرطوب سنتز و خصوصیات آن با استفاده از روش های مختلف آنالیز نظیر xrd، fe-sem، bet، ft-ir و nh3-tpd تعیین مشخصه گردید. کاتالیست دارای بلورینگی بالا، مساحت سطح بالا، مورفولوژی کروی و توزیع یکنواخت فاز فعال بوده است. عملکرد کاتالیست ir-zsm-5 در واکنش ناهمگن شبه الکتروفنتون برای حذف رنگ متیلن بلو به عنوان پساب مدل مورد ارزیابی قرار گرفت. تاثیرکمیت های مختلف عملیاتی نظیر غلظت کاتالیست در محیط واکنش، ph محلول و شدت جریان بین دو الکترود بررسی شد. نتایج نشان داد که بهترین شرایط عملیاتی شامل سطح ph برابر با 3، غلظت کاتالیست برابر با 0.2 گرم برلیتر و جریان 100 میلی آمپر بود که منجر به بالاترین بازده حذف (%100) گردید. عملکرد کاتالیست در سه آزمایش پی درپی افت چندانی نشان نداد که بیانگر قابلیت استفاده مجدد و پایداری آن می باشد. سینیتیک واکنش حذف بصورت شبه درجه اول ارائه شد که مطابقت قابل قبولی با نتایج تجربی نشان داد. نتایج این تحقیق منجر به درک بهتر از عملکرد کاتالیست ناهمگن زئولیتی در واکنش شبه الکتروفنتون می شود و همچنین حاکی از پتانسیل بالای روش نوین شبه الکتروفنتون ناهمگن در تصفیه پساب ها می باشد.

Dye removal from wastewater by heterogeneous electro-Fenton like reaction catalyzed by zeolite catalyst

Water shortage and wastewater discharge into environment have led to significant research in the field of environmental engineering for developing high efficient, fast, and cheap wastewater treatment. In recent years, advanced oxidation processes (AOP) have been subjected to significant attention for wastewater treatment due to feasibility of the process in mild reaction conditions, requiring low cost equipment, and short time of the process. ElectroFenton process addresses the potential drawbacks of Fenton reaction including transportation of H2O2 and regeneration of ferrous ions which act as catalyst. In the present study, ZSM5 catalyst was synthesized by hydrothermal technique and promoter was introduced through wet impregnation method. IrZSM5 catalyst w::as char::acterized by XRD, FESEM, BET, FTIR and NH3TPD techniques. The XRD patterns revealed the high crystallinity for the both parent and Ir impregnated ZSM5 catalysts. FESEM images showed microspherical morphology. N2adsorptiondesorption confirmed mesoporous structure for the synthesized catalyst including 321.1 and 327.3 m2/g specific surface area for the parent and IrZSM5 catalysts, respectively. FTIR spectrum confirmed formation of ZSM5 zeolite and also revealed presence of surface hydroxyl groups. NH3TPD revealed that acidity of the impregnated ZSM5 catalyst was increased due to interaction of Ir with zeolite structure. Acidimetricalkalimetric titration determined pHPZC for the parent and IrZSM5 catalysts equal to 3.6 and 3.9, respectively. Catalytic performance of IrZSM5 catalyst for removal of methylene blue (MB) from wastewater in heterogeneous electroFenton like reaction was evaluated. Different operation conditions were tested including concentration of catalyst, pH of wastewater solution and applied current between graphite electrodes. The results showed that IrZSM5 catalyst had acceptable performance in near neutral pH level due to the improved adsorption of MB molecules on IrZSM5 structure. The stable catalytic activity resulted from formation of no sludge related to active phase. Detected OH groups at the surface of the catalyst attained positive charge at pHpHpzc which influenced the adsorption capacity of the catalyst at different pH levels through electrostatic adsorption of ionized MB molecules on the catalyst. Blank test using no amount of IrZSM5 catalyst led to only 77% MB removal which was attributed to anodic oxidation on the surface of the graphite electrodes. Increasing applied current led to the improved MB removal owing to the faster degradation of the sacrificial graphite anode. The optimum operational conditions for the proposed system were pH=3, 0.2 gL1 of IrZSM5 catalyst and 100 mA applied current which resulted in the highest MB removal (100%). The reusability test of the catalyst was carried out by 3 consecutive runs at the optimum conditions. After each run, the used catalyst was regenerated at 550 °C to remove the adsorbed organic molecules due to adsorption of either MB or its oxidation intermediates. The regenerated catalyst showd the high catalytic performance with insignificant change of the removal efficiency as result of the high crystallinity and specific surface area of the synthesized catalyst. A pseudo first order kinetic was proposed for the reaction of removal which fitted the experimental data with the high correlation factor. The results confirmed the high potential of the heterogeneous electro fentonlike process for wastewater treatment.