Diklofop metil'in ileri oksidasyon teknikleriyle parçalanma süreçlerinin incelenmesi = Investigation of diclofop methyl's degradation process by advanced oxidation techniques

Abstract

Klorlu pestisitler yüzeysel sulara ve yer altı sularına karışan ve tüm canlı ekosistemi için toksik, kanserojenik ve mutajenik etkilere sahip olan kimyasal maddelerdir. Tarımsal faaliyetler sırasında açığa çıkan bu toksik klorlu pestisitler kimyasal olarak kararlı yapıya sahip olmaları ve bundan dolayı abiyotik ve/veya biyotik süreçler yoluyla kolayca parçalanabilen moleküller olmamalarından ötürü zor parçalanmaktadırlar. Bu maddelerin arıtımı kimyasal çöktürme, koagülasyon ve flokülasyon, biyolojik oksidasyon ve diğer temel konvansiyonel su ve atık su arıtma teknikleri gibi konvansiyonel arıtma prosesleriyle tam olarak gerçekleşememektedir. Konvansiyonel arıtma prosesleri bu kimyasalların istenilen seviyelere düşürülmesinde etkili olmamakta, sadece belirli pestisitlerin belirli bir oranda ortamdan uzaklaştırılması için kullanılmaktadırlar. Bu kimyasal maddelerin çevresel alıcı ortama verilmeden önce, flordan sonra en güçlü oksidan madde olan, organiklerin mineralizasyonunda hızlı ve seçici olmayan reaksiyonları mümkün kılan hidroksil radikallerin üretimine dayanan ileri oksidasyon prosesleriyle zararsız ürünlere dönüştürülmeleri veya mineralizasyonların sağlanması gerekmektedir. Bu tez çalışmasında hakkında literatürde yapılmış çalışmaların kısıtlı olduğu klorlu bir pestisit olan diklofop metil herbisitinin su ortamından giderim verimleri ileri oksidasyon proseslerinden olan Elektro Fenton, Foto Fenton ve Peroksi Elektrokoagülasyon ile laboratuvar ortamında GC-MS cihazı kullanılarak araştırılmıştır. Proseslerin diklofop metil giderimi üzerine etkileri araştırılırken; Elektro Fenton prosesi için iletkenlik, pH, akım yoğunluğu, sisteme verilen O2 miktarı, süre, Foto Fenton prosesi için pH, Fe+2 miktarı, H2O2 miktarı, ışık şiddeti, süre, Peroksi Elektrokoagülasyon prosesi için iletkenlik pH, H2O2 miktarı, akım ve süre parametreleri incelenmiştir. Her proses için ayrı ayrı kinetik, enerji tüketimi ve maliyet hesapları yapılmıştır. Oluşan ara ürünler hakkında fikir sahibi olunmuştur. Belirlenen optimum şartlar altında Elektro Fenton prosesi ile 30 dakikalık reaksiyon sonucunda %89,55, Foto Fenton prosesi ile 20 dakikalık reaksiyon sonucunda %41,85, Peroksi Elektrokoagülasyon prosesi ile 25 dakikalık reaksiyon sonucunda %79,2 diklofop metil giderme verimine ulaşılmıştır. Her üç proses de Pseudo ikinci derece kinetik modeline uyum sağlamıştır. Giderilen diklofop metil miktarı ve maliyet değerlerine bakıldığında en ekonomik prosesin Peroksi Elektrokoagülasyon olduğu sonucuna varılmıştır.

In the century we live in, the population is increasing day by day, so people need more food and beverage. In order to meet this need, it is necessary to expand the agricultural areas. Harmful organisms (insects, plant pathogens, weeds, mollusks, birds, mammals, fish, worms, etc.) must be prevented and kept under control in order to achieve maximum production in agricultural areas. For this, pesticide mixtures, which are chemicals consisting of different substance contents, are used for agricultural control. Chlorinated pesticides mix with surface and ground waters and have toxic, carcinogenic, and mutagenic effects on all living ecosystems. These toxic chlorinated pesticides, which are released during agricultural activities, are difficult to decompose since they have a chemically stable structure and can not easily degradable molecules through abiotic and biotic processes. These substances cannot be completely treated with conventional wastewater treatment processes such as chemical precipitation, coagulation and flocculation, biological oxidation, and other basic conventional wastewater treatment techniques. Conventional treatment processes are insufficient to reduce concentrations of these chemicals to the standards limit values. Still, they are used to remove some specific pesticides at a certain rate. These chemicals must be converted into harmless products or mineralized by advanced oxidation processes based on the production of hydroxyl radicals, the strongest oxidant after fluorine, and enable rapid and non-selective reactions in the mineralization of organics, before discharge to the receiving environment. Advanced oxidation processes have different mechanisms, such as photochemical and electrochemical reactions. Advanced oxidation processes are divided into three main classes. These are (i) processes based on the methodology applied for the production of oxidizing radicals (OH·, HO2·, O·), (ii) processes according to whether oxidation processes occur by UV and/or Vis light radiation, and (iii) processes that depend on whether oxidation processes use a single phase or heterogeneous catalysts. Diclofop-methyl herbicide (2-[4-(2,4-dichlorophenoxy) phenoxy]-propionate) with the chemical formula C10H14Cl2O4 is an aryloxyphenoxy propionic acid in the phenoxy acid herbicide group. It is a post-emergence herbicide and a graminicide commonly used to suppress weed growth in crop fields. Diclofop methyl is a broad-spectrum pesticide used in wheat, barley, soybean, peanut, lentil, onion, rapeseed, beet, wild oat, and other crop fields to control weed growth to improve and improve agricultural production. Aryloxy phenoxy propionate is a specific herbicide that inhibits the synthesis of fatty acids by reducing the activity of acetyl CoA carboxylase (ACCase) in herbaceous plants. Diclofop methyl is named with different trade names in agricultural applications, is a colorless and odorless crystalline substance. Diclofop methyl has a molecular weight of 341.20 g/mol, a melting point of 39–41 oC, a boiling point of 173–175 oC at 0.1 mbar, and a vapor pressure of 3.4×10-7 mbar at 20 oC and 1.5×10-5 mbar at 30 oC mbar. Diclofop methyl solubility in common organic solvents is 40 g for acetone, 50 g for xylene, and 40 g for methanol per 100 ml. Its solubility in water is approximately 50 mg/L at 22 oC. In this thesis, the removal of diclofop methyl herbicide from the aquatic environment with the Electro Fenton, Photo Fenton and Peroxy Electrocoagulation processes, which are advanced oxidation processes, was investigated using GC-MS. For each process, kinetic models, energy consumption, and cost analysis were calculated separately. When the literature is examined, it is seen that the studies on this subject are quite limited. Diclofop methyl solutions used in this thesis were prepared between 1 mg/L and 100 mg/L concentrations. The calibration curve was drawn with the determined GC-MS temperature program and the equation of the curve was determined. The R2 value was found to be 0.9992. As a result of the extraction studies, it was decided to use ethyl acetate as the solvent in a 1:1 volume ratio. A vortex device was used for 1 min for the complete mixing of the sample and the solvent. After waiting for 15 minutes, the upper phase was taken into a vial and measurements were made with the temperature program determined in the GC-MS. While investigating the effects of processes on diclofop methyl removal, the effects of certain parameters for the processes were investigated. For the Electro Fenton process, effects of conductivity, pH, current density, amount of O2 supplied to the system, and time parameters were examined. Similarly, for the Photo Fenton process; The effects of pH, Fe+2 amount, H2O2 amount, light intensity, and time parameters were investigated. For the Peroxy Electrocoagulation process; conductivity, pH, H2O2 amount, current, and time parameters were investigated. As a result of the experimental studies on the removal of diclofop methyl with the Electro Fenton process, optimum values were found as pH=11, O2 dose= 8 L/min, current density= 2.66 mA/cm2, NaCl= 0.75g/L. With the determined optimum values, 89.55% diclofop methyl removal rate was achieved due to the reaction time of 30 minutes. As a result of the experimental studies on the removal of diclofop methyl with the Photo Fenton process, the optimum values were found to be pH=11, H2O2=100g/L, Fe+2 dose=100 mg/L, light intensity=18 watts. With the optimum determined values, 41.85% diclofop methyl removal rate was achieved as a result of the reaction time of 20 minutes. As a result of the experimental studies on the removal of diclofop methyl with the Peroxy Electrocoagulation process, pH= 5, H2O2= 500 mg/L, current density= 2.66 mA/cm2, NaCl= 0.75 g/L were found as optimum values. With the optimum determined values, 79.2% diclofop methyl removal rate was achieved as a result of the reaction time of 25 minutes. Kinetic model calculations were made for oxidation studies using Electro Fenton, Photo Fenton, and Peroxy Electrocoagulation processes. All three processes were suitable for the pseudo-second-order kinetic model, and R2 values were calculated as 0.9861, 0.9988, 0.9882 for ElectroFenton, PhotoFenton, and Peroxy Electrocoagulation processes, respectively. Electricity consumption and cost values for 1 m3 diclofop methyl removal were calculated for all three processes. As a result of the electricity consumption study, 8.1 kWh/m3 for the Electro Fenton process, 60 kWh/m3 for the Photo Fenton process, and 10.125 kWh/m3 for the Peroxy Electrocoagulation process were obtained. As a result of the cost analysis study, 1570.289 $/m3 for the Electro Fenton process, 46.769 $/m3 for the Photo Fenton process, and 51.641 $/m3 for the Peroxy Electrocoagulation process were determined. In order to have information about the intermediate products, the peaks in the chromatogram obtained in the study were investigated. It was concluded that the initial peaks were not similar to diclofop methyl fragments because their isotope distributions were completely different, so they could be products caused by pollution or by gas phase decomposition products. Molecules that lost their chlorine such as phenoxycyclohexatriene (C12H9O), methyl (CH3), 2-(2-Phenoxyethoxy) benzoate (C15H13O4), 1,3-Dioxolane (C10H11O4) were observed in the following periods. 1-Chlorodibenzo-p-dioxin (C12H7ClO2), dichlorophenoxyl-diol (C12H7Cl2O2), 2-Chloro-2,2-diphenylacetic acid (C14H11Cl2O2), 5-Chloro-2-(4-chlorophenoxy) phenol (C12H8Cl2O2), 2-Chloro-3-(4-hydroxylbutoxy) naphthoquinone (C14H13ClO4), diethylhexylphthalate (C24H38O4) intermediate products were formed. Considering the removal amount of diclofop methyl, energy consumption, and the cost analysis of all processes, the most economical process was the Peroxy Electrocoagulation.