Fenton ve foto-fenton esaslı proseslerle organofosforlu pestisitlerin gideriminin araştırılması
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Date
2012
Authors
Azak, Safiye Hilal
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Publisher
Uludağ Üniversitesi
Abstract
Organofosforlu yapıda olan Dimetoat (C5H12NO3PS2, 229,26 g/mol, 0,0-dimetil S-[2- (metilamino)-2-oksoetil]dityofosfat) ve Monokrotofos (C7H14NO5P, 223,2 g/mol, Dimetil (E)-1-metil-2-(metilkarbamoil)vinil fosfat), sucul ortamlar için oldukça toksik, endokrin bozucu kimyasallardır ve insan sağlığı açısından kanserojen olma riski vardır. Dimetoat (DMT) ve Monokrotofos (MCP) pestisitlerinin sudaki çözünürlüklerinin yüksek olması nedeniyle yeraltı sularına sızma potansiyeli oldukça fazladır. Artan su ihtiyacına karşılık bütün dünya ülkelerinde olduğu gibi Türkiye’de de yeraltı suları içmesuyu maksatlı kullanılmakta ve konvansiyonel arıtma sistemleri ile oldukça kompleks organik yapıdaki pestisitlerin giderimi mümkün gözükmemektedir. Fenton prosesleri pestisit gideriminde kendini kanıtlamış olan yöntemlerdir. Bu tez çalışmasında, DMT ve MCP pestisitlerinin giderimi için Fenton, Fenton benzeri, FotoFenton ve Foto-Fenton benzeri proseslerin verimliliği araştırılmıştır. Fenton ve Fenton benzeri proseslerde, proses bağımsız değişkenlerin DMT ve MCP’nin ayrışma ve mineralizasyon davranışı üzerindeki etkileri ve optimum proses koşulları Merkezi Kompozit Dizayn (MKD) yöntemi kullanılarak belirlenmiştir. Proses bağımsız değişkenleri etkilerinin analitik olarak birbirleriyle karşılaştırılabilir olması için deneysel çalışma koşulları sabit alınmış ve başlangıç konsantrasyonları pestisit için 0,005-0,094 mM, Fe(II)/Fe(III) için 0,01-0,05 mM, H2O2 için 0,05-0,25 mM, TOK için 2-17 mg/L ve reaksiyon süresi için 5-65 dk aralığında değişen proses koşullarında çalışılmıştır. Foto-Fenton prosesi olarak konvansiyonel arıtma proseslerine kolaylıkla adapte olabilecek özellikte, henüz literatürde eşi bulunmayan, bu çalışma kapsamında özgün tasarlanan bir fotoreaktör kullanılmıştır. Foto-Fenton ve Foto-Fenton benzeri proseslerde, DMT ve MCP’nin ayrışma ve mineralizasyon davranışı üzerinde artan UVA ışık şiddeti etkisinin analitik olarak karşılaştırılabilir olması için MKD kullanılarak belirlenen optimum proses koşullarında çalışılmış, optimum UV ışık şiddeti konvansiyonel optimizasyon yöntemi ile belirlenmiştir. Bu çalışmada seçilen başlangıç DMT/MCP, Fe(II)/Fe(III) ve H2O2 konsantrasyonları için, DMT ve MCP’nin ayrışma verimi ve TOK giderimi üzerinde en önemli etkiye başlangıç pestisit konsantrasyonunun sahip olduğu, Fe(II) ve Fe(III) katalizörlerinin ise Fenton reaksiyonlarını yönlendirici bir etkisi olduğu belirlenmiştir. DMT ve MCP pestisitlerinin ayrışması sonucu açığa çıkan PO4 3- anyonu ile Fe2+/Fe3+ iyonlarının oluşturduğu FeH2PO4 + /FeH2PO4 2+ kompleksleri, reaksiyon kinetiğini değiştiren geciktirici etkilere neden olmuş, bu etkiler MCP ile çalışılan Fenton ve Fenton benzeri proseslerde daha fazla görülmüştür. Foto-Fenton ve Foto-Fenton benzeri prosesler de ise, FeH2PO4 2+ komplekslerinin UV-A ışıması ile fotolizi DMT ve MCP ayrışma ve mineralizasyon verimini arttırmıştır. Kullanılan UV-A ışık şiddeti miktarının pestisit ayrışma ve mineralizasyon verimi üzerinde önemli bir etkiye sahip olduğu belirlenmiştir. FeH2PO4 2+ komplekslerinin en etkin fotolizi, çalışılan bütün Foto-Fenton prosesleri için 16x10-6 einstein/s UV-A ışık şiddetinde gerçekleşmiştir. 45x10-6 einstein/s UV-A ışık şiddetinde ise artan FeH2PO4 2+ kompleksleri UV-A ışınlarını absorbe ederek uygulanan ışık şiddetinin azalmasına neden olmuştur. Fenton ve FotoFenton proseslerinin DMT ve MCP pestisitlerinin ayrışmasında ve TOK gideriminde daha etkin olduğu belirlenmiştir. DMT, 4x10-6 einstein/s’den 45x10-6 einstein/s artan UV-A ışık şiddetlerinde, MCP’ye nazaran daha kısa sürede, daha az enerji tüketerek giderilmiştir. MCP pestisitinin gideriminde Fenton ve Fenton benzeri proseslere nazaran Foto-Fenton ve Foto-Fenton benzeri proseslerin daha etkin olduğu, Foto-Fenton prosesi ile MCP’nin tamamen yok olmasının ve yüksek oranda mineralizasyonunun mümkün olduğu belirlenmiştir. 45x10-6 einstein/s UV-A ışık şiddetinde, Fe(II)/H2O2 = 1/5 molar oranında çalışılan Foto-Fenton prosesi ile 0,024 mM DMT içeren sentetik pestisit çözeltisinden, DMT 8 dakikada tamamen giderilmiş ve 3 saatlik reaksiyon sonunda TOK konsantrasyonu 2 mg/L’nin altına indirilmiştir. 16x10-6 einstein/s UV-A ışık şiddetinde, Fe(II)/H2O2 = 1/5 molar oranında çalışılan Foto-Fenton prosesi ile 0,022 mM MCP içeren sentetik pestisit çözeltisinden, MCP 20 dakikada tamamen giderilmiş ve 3 saatlik reaksiyon sonunda TOK konsantrasyonu 2 mg/L’nin altına indirilmiştir. Foto-Fenton prosesi ile DMT ve MCP’nin insan sağlığı ve sucul ortam açısından toksik etkilerinin tamamen giderildiği belirlenmiştir. Bu tez çalışması kapsamında tasarlanan fotoreaktörün yüksek bir performans ile çalıştığı bilimsel veriler ile kanıtlanmıştır.
Dimethoate (C5H12NO3PS2, molecular weight of 229,3 g/mol, 0-0-dimethyl S-[2- (methylamino)-2-oxoethyl]dithioatephosphate) and Monocrotophos (C7H14NO5P, molecular weight of 223,2 g/mol, Dimethyl (E)-1-methyl-2-(methylcarbamovy)vinyl phosphate) are organophosphate pesticides that are highly toxic for aquatic environments. They are also endocrine disrupting chemicals and a possible human carcinogen. Because Dimethoate (DMT) and Monocrotophos (MCP) are highly soluble in water, they have a great potential to leaching into groundwaters. Groundwaters are used as drinking water purposes due to increasing water demand in Turkey such as around the world and conventional treatment systems are not capable to treat the complex organic pesticides. Fenton processes have been proved its efficiency on pesticide removal. Hence in this thesis, the efficiencies of Fenton, Fenton like, PhotoFenton and Photo-Fenton like processes were investigated to remove pesticides from waters contaminated with DMT and MCP. The interactive effects of process independent variables on pesticide degradation and mineralization behavior and the optimum conditions in the Fenton and Fenton like processes were determined by Central Composite Design (CCD). All the designed experiments were carried out under the same initial concentration ranges for pesticides between 0,005-0,094 mM, Fe(II)/Fe(III) between 0,01-0,05 mM, H2O2 between 0,05-0,25 mM, TOC between 2-17 mg/L and the reaction time between 5-65 min in order to compare analytically the interactive effects of process independent variables on DMT and MCP degradation and mineralization behavior with each others. A new designed photoreactor that can be adaptable more easily to conventional treatment processes and something that has not been studied in the past was used as Photo-Fenton process in the experiments. In order to assess the effect of increasing UV-A light intensity on degradation/mineralization efficiency of DMT and MCP, it was studied at the optimum conditions which are determined by CCD. The optimum UV-A light intensity was determined by conventional optimization method. According to optimization data obtained for selected initial concentrations of DMT/MCP, Fe(II)/Fe(III) and H2O2 in this study, the initial pesticide concentration has the most important effect on DMT and MCP degradation efficiencies and TOC removals and Fe(II) and Fe(III) catalysts have a driven effects on Fenton reactions. The FeH2PO4 + /FeH2PO4 2+ complexes which are generated between Fe2+/Fe3+ ions and released PO4 3- are retarded the Fenton reactions and changed the reaction kinetic. The passivation effects of FeH2PO4 + /FeH2PO4 2+ complexes are seen more significantly in the Fenton and Fenton like processes studied with MCP. The photolysis of FeH2PO4 2+ complexes takes place under UV-A radiation enhanced the degradation and mineralization efficiencies of DMT and MCP in the Photo-Fenton and Photo-Fenton like processes. It was determined that the amount of applied UV-A light intensity has a significant effect on degradation and mineralization efficiencies of DMT and MCP. The most effective photolysis of FeH2PO4 2+ complexes are realized at 16x10- 6 einstein/s UV-A light intensity for each Photo-Fenton process. When the UV-A light intensity increased to 45x10-6 einstein/s, additional FeH2PO4 2+ complexes absorbed the UV-A radiation so that applied UV-A light intensity was decreased. It was determined that Fenton and Photo-Fenton processes are more effective for degradation of DMT and MCP pesticides and TOC removals than the others. At the UV-A light intensity increased from 4x10-6 einstein/s to 45x10-6 einstein/s, DMT was disappeared in a shorter reaction time consuming lower energy than MCP. It was determined that PhotoFenton and Photo-Fenton like processes are more satisfactorily on degradation and mineralization of MCP than Fenton and Fenton like processes, and higher mineralization of MCP and its disappearance were possible in Photo-Fenton process. DMT was disappeared in 8 minutes completely and TOC concentration was decreased under 2 mg/L after 3 h of reaction time in Photo-Fenton process studied with a synthetic solution containing 0,024 mM of DMT, applied 45x10-6 einstein/s of UV-A light intensity at 1/5 molar ratio of Fe(II)/H2O2. MCP was disappeared in 20 minutes completely and TOC concentration was decreased under 2 mg/L after 3 h of reaction time in Photo-Fenton process studied with a synthetic solution containing 0,022 mM of MCP, applied 16x10-6 einstein/s of UV-A light intensity at 1/5 molar ratio of Fe(II)/H2O2. Effluents from Photo-Fenton process at the conditions of DMT and MCP was treated 100% determined that toxic effects of DMT and MCP to aquatic environments and human health were eliminated completely. In this thesis, new designed photoreactor was employed in a great performance that was proven with scientific data from literature.
Dimethoate (C5H12NO3PS2, molecular weight of 229,3 g/mol, 0-0-dimethyl S-[2- (methylamino)-2-oxoethyl]dithioatephosphate) and Monocrotophos (C7H14NO5P, molecular weight of 223,2 g/mol, Dimethyl (E)-1-methyl-2-(methylcarbamovy)vinyl phosphate) are organophosphate pesticides that are highly toxic for aquatic environments. They are also endocrine disrupting chemicals and a possible human carcinogen. Because Dimethoate (DMT) and Monocrotophos (MCP) are highly soluble in water, they have a great potential to leaching into groundwaters. Groundwaters are used as drinking water purposes due to increasing water demand in Turkey such as around the world and conventional treatment systems are not capable to treat the complex organic pesticides. Fenton processes have been proved its efficiency on pesticide removal. Hence in this thesis, the efficiencies of Fenton, Fenton like, PhotoFenton and Photo-Fenton like processes were investigated to remove pesticides from waters contaminated with DMT and MCP. The interactive effects of process independent variables on pesticide degradation and mineralization behavior and the optimum conditions in the Fenton and Fenton like processes were determined by Central Composite Design (CCD). All the designed experiments were carried out under the same initial concentration ranges for pesticides between 0,005-0,094 mM, Fe(II)/Fe(III) between 0,01-0,05 mM, H2O2 between 0,05-0,25 mM, TOC between 2-17 mg/L and the reaction time between 5-65 min in order to compare analytically the interactive effects of process independent variables on DMT and MCP degradation and mineralization behavior with each others. A new designed photoreactor that can be adaptable more easily to conventional treatment processes and something that has not been studied in the past was used as Photo-Fenton process in the experiments. In order to assess the effect of increasing UV-A light intensity on degradation/mineralization efficiency of DMT and MCP, it was studied at the optimum conditions which are determined by CCD. The optimum UV-A light intensity was determined by conventional optimization method. According to optimization data obtained for selected initial concentrations of DMT/MCP, Fe(II)/Fe(III) and H2O2 in this study, the initial pesticide concentration has the most important effect on DMT and MCP degradation efficiencies and TOC removals and Fe(II) and Fe(III) catalysts have a driven effects on Fenton reactions. The FeH2PO4 + /FeH2PO4 2+ complexes which are generated between Fe2+/Fe3+ ions and released PO4 3- are retarded the Fenton reactions and changed the reaction kinetic. The passivation effects of FeH2PO4 + /FeH2PO4 2+ complexes are seen more significantly in the Fenton and Fenton like processes studied with MCP. The photolysis of FeH2PO4 2+ complexes takes place under UV-A radiation enhanced the degradation and mineralization efficiencies of DMT and MCP in the Photo-Fenton and Photo-Fenton like processes. It was determined that the amount of applied UV-A light intensity has a significant effect on degradation and mineralization efficiencies of DMT and MCP. The most effective photolysis of FeH2PO4 2+ complexes are realized at 16x10- 6 einstein/s UV-A light intensity for each Photo-Fenton process. When the UV-A light intensity increased to 45x10-6 einstein/s, additional FeH2PO4 2+ complexes absorbed the UV-A radiation so that applied UV-A light intensity was decreased. It was determined that Fenton and Photo-Fenton processes are more effective for degradation of DMT and MCP pesticides and TOC removals than the others. At the UV-A light intensity increased from 4x10-6 einstein/s to 45x10-6 einstein/s, DMT was disappeared in a shorter reaction time consuming lower energy than MCP. It was determined that PhotoFenton and Photo-Fenton like processes are more satisfactorily on degradation and mineralization of MCP than Fenton and Fenton like processes, and higher mineralization of MCP and its disappearance were possible in Photo-Fenton process. DMT was disappeared in 8 minutes completely and TOC concentration was decreased under 2 mg/L after 3 h of reaction time in Photo-Fenton process studied with a synthetic solution containing 0,024 mM of DMT, applied 45x10-6 einstein/s of UV-A light intensity at 1/5 molar ratio of Fe(II)/H2O2. MCP was disappeared in 20 minutes completely and TOC concentration was decreased under 2 mg/L after 3 h of reaction time in Photo-Fenton process studied with a synthetic solution containing 0,022 mM of MCP, applied 16x10-6 einstein/s of UV-A light intensity at 1/5 molar ratio of Fe(II)/H2O2. Effluents from Photo-Fenton process at the conditions of DMT and MCP was treated 100% determined that toxic effects of DMT and MCP to aquatic environments and human health were eliminated completely. In this thesis, new designed photoreactor was employed in a great performance that was proven with scientific data from literature.
Description
Keywords
Dimetoat, Monokrotofos, Fenton, Fenton benzeri, Foto-fenton, Foto-fenton benzeri, Dimethoate, Monocrotophos, Fenton like, Photo-fenton, Photo fenton like
Citation
Azak, S. H. (2012). Fenton ve foto-fenton esaslı proseslerle organofosforlu pestisitlerin gideriminin araştırılması. Yayınlanmamış doktora tezi. Uludağ Üniversitesi Fen Bilimleri Enstitüsü.