Comparison between conventional pump and adsorption sampling method with passive solid phase microextraction ( SPME ) sampling to investigate changes in the concentration of benzene, toluene , and xylene ( BTX ) in urban ambient air

Background and Aims: Besides toxic effects on human, animals and plants, aromatic hydrocarbons may also be effective in the formation of photochemical smog. The measurement of these hydrocarbons, therefore, play aprominent part in evaluating their health and environmental impacts. The purpose of this study was to compare pump and adsorption sampling method with solid phase microextraction (SPME) to investigate changes in theconcentration of benzene, toluene, and xylene (BTX).Materials and Methods: SPME samplers in sampling protective holders were placed in ambient air at a relatively high traffic routes for 5 days. Sampling was carried out in two seasons. Samples were analyzed at the end of sampling period. In addition, pump and adsorption sampling method was also used to measure the concentrations of benzene, toluene, and xylene. Ethical issues were all considered in conducting the study and citation.Results: The obtained results in solid phase microextraction sampling method were compared with those obtained using the conventional pump and adsorbent method. Correlation coefficients (R2) between these methods were 0.98, 0.9 and 0.95 for benzene, toluene, and xylene, respectively. The results obtained with pump and adsorption method showed a higher values in general.Conclusion: The comparison between obtained results with these methods indicates a relatively similar values. It may be concluded that SPME sampling method can also present reliable results for the measurement of benzene,toluene and xylene concentrations in the ambient air.Keywords: Passive sampling, SPME, Benzene, Toluene, XyleneFor downloading the full text please click here

Biodegradability improvement of composting leachate by sulfate radical-advanced oxidation process followed by aerobic and anaerobic treatmentcomparison of biodegradability improvement of composting leachate by sulfate radical-advanced oxidation process for aerobic and anaerobic treatment

Aims: Comparing to strong traditional oxidation, the persulfate and sulfate radicals was characterized by relatively low cost and easy application. The present study aimed to investigate the performance of sulfate radical-based advanced oxidation process (SR-AOP) for pretreatment of compost leachate in order to improvement of its biodegradability. Materials and Methods: The sulfate radicals was used for pretreatment of compost leachate in the batch reactor followed by aerobic and anaerobic biological reactors. Results: the results of combination of SR-AOP with biological treatment showed that BOD5/COD ratio was increase. However, the different trend was observed in COD removal by sequencing batch reactor (SBR) and anaerobic sequencing batch reactor (ASBR). Comparing to SR-AOP with ASBR, the SR-AOP with SBR substantially improved final COD removal efficiency up to 70%. Although pretreatment of compost leachate with the SR-AOP clearly improved the BOD5/COD ratio of entering raw leachate into ASBR (from 0.4 to 0.65), but, the COD removal efficiency was ranging between 25% and 27%. Conclusion: Based on the results, it can be concluded that the BOD5/COD ratio cannot be suggested as biodegradability improvement indicator without considerations of changing of substrate nature during pretreatment

فراینداکسیدانیو کاتالیتیکی آهن دو ظرفیتی/ پرسولفات/ کلینوپتی لولایت به عنوان یک روش مقرون به صرفه جهت تصفیه پساب واحد ایزوسیانات و متاتولوئن دی آمین پتروشیمی

Background: Petrochemical wastewater from isocyanate units contains aromatic and hazardous compounds such as Diaminotoluenes, Mononitrotoluene, Dinitro-toluene, Nitro-phenol, Nitro-cresol. Persulfate and ferrous sulfate can produce sulfate radicals with strong standard oxidation potential. Clinoptilolite, a natural adsorbent; plus sulfate radicals can result in catalytic oxidation of these chemicals. The objective of this study is to evaluate the catalytic oxidation efficiency Fe2+/Persulfate/ Clinoptilolite and cost effectiveness of this process for treatment of petrochemical wastewater containing aromatics.Materials and methods: The effect of study variables including persulfate and ferrous sulfate concentrations, zeolite dosages, pH and oxidation time were investigated. The type and amount of aromatic compounds as well as COD and TSS removal efficiencies were determined. All procedures in study were conducted ethicallyResults: The COD and TSS removal efficiencies using catalytic oxidative treatment processes by Fe,Persulfate, Clinoptilolite were 96% and 95%, respectively. The corresponding COD and TSS removal efficiencies using Fe and Persulfate, without zeolite were 85% and 80%, respectively.Conclusion: The catalytic processes utilizing Fe2+/Persulfate/ Clinoptilolite demonstrates an excellent COD and TSS removal efficiency. Due to its natural nature, low cost compared to chemical oxidants, as well as improvements in the efficiency of advanced oxidation processes, Zeolite can be considered as an efficient and cost-effective alternative to upgrade the catalytic oxidative treatment. زمینه و اهداف: پساب واحد ایزوسیانات پتروشیمی، حاوی ترکیبات آروماتیک خطرناک و متنوع میباشد. پرسولفات و آهن دو ظرفیتی، میتوانند رادیکالهای سولفات با پتانسیل اکسیداسیون بالا تولید نمایند. کلینوپتیلولایت یک جاذب طبیعی میباشد که همراه با رادیکالهای سولفات میتوانند باعث فرایند تصفیه اکسیداتیو کاتالیکی شوند. هدف از این مطالعه ارزیابی کارایی و هزینه فرایند اکسیداتیو کاتالیتیکی آهن دو ظرفیتی، پرسولفات، کلینوپتیلولایت برای تصفیه پساب پتروشیمی حاوی ترکیبات آروماتیک میباشد. مواد و روشها: تاثیر متغیرهای مختلف شامل غلظت پرسولفات، سولفات آهن و زئولیت،pH و زمان اکسیداسیون مورد بررسی قرار گرفت و در نهایت مقدار حذف COD و TSS در نمونه های تصفیه شده مشخص گردید. در کلیه مراحل انجام پژوهش، موازین اخلاقی، مراعات گردید. یافته ها: مقدار حذف COD و TSS توسط فرایند تصفیه کاتالیتیکی اکسیداتیو با استفاده از سولفات آهن، پرسولفات و کلینوپتیلولایت به ترتیب 96 و 95 درصد بود. در حالیکه مقدار حذف COD و TSS توسط فرایند سولفات آهن، پرسولفات و بدون استفاده از کلینوپتیلولایت حدود 85 و 80 درصد بود. نتیجه گیری: در فرایند تصفیه اکسیداسیون کاتالیتیکی که در آن به طور همزمان از آهن دو ظرفیتی/ پرسولفات و کلینوپتیلولایت استفاده میگردید، بیشترین مقدار حذف COD و TSS نشان داده شد. با توجه به طبیعی بودن زئولیت و هزینه کم آن نسبت به مصرف مواد شیمیایی و همچنین بهبود قابل توجه راندمان فرایند اکسیداسیون پیشرفته، استفاده از آن از نظر فنی و اقتصادی توجیه پذیر میباشد