كليدواژه :
بنزآلدئيد , التراسونيك , هيدروژن پراكسيد , تخريب
چكيده فارسي :
هدف از انجام اين مطالعه، بررسي و ارزيابي فرايند اكسيداسيون پيشرفته US / H2O2 در تخريب تركيب سمي بنزآلدئيد مي باشد. در اين راستا اثر پارامترهاي pH، غلظت اوليه بنزآلدئيد، غلظت اوليه هيدروژن پراكسيد، دامنه ارتعاش و فركانس التراسونيك روي تخريب بنزآلدئيد مورد مطالعه قرارگرفت. نتايج نشان داد كه تخريب بنزآلدئيد در سيستم US / H2O2 تحت تاثير پارامترهاي pH، غلظت اوليه بنزآلدئيد، غلظت اوليه هيدروژن پراكسيد، دامنه ارتعاش و فركانس التراسونيك است. ميزان تخريب بنزآلدئيد با التراسونيك تنها در غلظت 10 ميلي گرم بر ليتر از بنزآلدئيد، pH=3 ، فركانس 1 سيكل بر ثانيه و دامنه ارتعاش 100 ميكرومتر در حدود 80% بدست آمد. نتايج درصد حذف بنزآلدئيد با پراكسيد هيدروژن تنها در غلظت 10 ميلي گرم بر ليتر از بنزآلدئيد، غلظت 100 ميلي گرم بر ليتر از هيدروژن پراكسيد و pH=3 ذرحدود 16% بود. نتايج نشان داد كه هيدروژن پراكسيد تنها براي تخريب بنزآلدئيد موثر نيست در حاليكه تركيب H2O2 با التراسونيك درصد تخريب بنزآلدئيد را افزايش داده است. به طوريكه در مدت زمان 60 دقيقه، دامنه ارتعاش 100، فركانس 1 سيكل بر ثانيه، غلظت بنزآلدئيد 10 ميلي گرم بر ليتر ، غلظت هيدروژن پراكسيد 100 ميلي گرم بر ليترو pH=3، بيشترين درصد حذف با راندمان 91% حاصل شد. مطابق نتايج تخريب بنزآلدئيد در فرآيند التراسونيك / هيدروژن پراكسيد با سينتيك شبه مرتبه اول تطابق خوبي داشت. بنابراين تخريب سونوشيميايي بنزآلدئيد با فرايند US / H2O2 مي تواند روش موثري براي حذف بنزآلدئيد از محلول هاي آبي باشد.
چكيده لاتين :
Aromatic aldehydes are toxic compounds present in different waste-waters coming from the chemical and petrochemical industries. Their environmental fate may end up by their occurrence in the ground water through the infiltration/deep percolation processes of rain and snow water. Therefore, this kind of substances is contained not only in various industrial wastewaters, but occasionally also in drinking water. Hence, the degradation of such compounds in water and wastewater is still of special interest for many researchers. Benzaldehyde is an aromatic aldehydes used chiefly as a precursor to other organic compounds, ranging from pharmaceuticals to plastic additives and it has been classified as a hazardous substance by the United States Environmental Protection Agency. As a result, the use of alternative treatment technologies, aiming to mineralize or transform refractory molecules into others which could be further biodegraded, is a matter of great concern. Among them, advanced oxidation processes (AOPs) have already been used for the treatment of water and wastewater containing recalcitrant organic compounds such as pesticides, surfactants, colouring matters, pharmaceuticals and endocrine disrupting chemicals. Moreover, they have been successfully used as pretreatment methods in order to reduce the concentrations of toxic organic compounds that inhibit biological wastewater treatment processes. The main mechanism of AOPs function is the generation of highly reactive free radicals. Hydroxyl radicals (HO•) are effective in destroying organic chemicals because they are reactive electrophiles (electron preferring) that react rapidly and nonselective with nearly all electron-rich organic compounds. They have an oxidation potential of 2.33 ev and exhibit faster rates of oxidation reactions comparing to conventional oxidants such as O3. The diverse methods used for generating these radicals are photo catalysis and sonochemistry methods. A new alternative sonochemistry approach offers a solution for combating the persistent water and wastewater organic pollutants. Sonochemical degradation could be used for organic pollutant removal in aqueous solutions. The advantages of using ultrasound irradiation are the simplicity of its use , the ultrasound does not require additional chemicals, and it can be used for treatment of turbid solutions. In this research, ultrasonic/H2O2 advanced oxidation process has been studied for degradation of aqueous solution of benzaldehyde. The effect of key parameters such as ultrasonic frequency, ultrasonic amplitude, time, pH of solution and initial concentration of the benzaldehyde on the removing rate of benzaldehyde are investigated. Different concentrations of benzaldehyde and H2O2 were prepared and the solutions were exposed to ultrasonic treatment (UP 400S model). The experiments was carried out in a batch reactor for 60 min and each 5 min an aliquot was taken from the solutions. Absorbance of sampling solutions was recorded by UV-Vis spectrophotometer of Hack (DR 5000-15 V model). The results show that, the removal rate increases with the increase of time, ultrasonic frequency and amplitude and decreases with the increase of solution pH, H2O2 and benzaldehyde concentrations. As data shown, the degradation of benzaldehyde in ultrasonic/ H2O2 process best fitted by pseudo first order kinetic. It can be conclude the combined of ultrasonic/ H2O2 led to 91% degradation of benzaldehyde after 60 min.
