Mn (II)'nin atmosferik oksijenle oksidasyonundan oluşan çamur yaşının oksidasyon hızına etkisi
Influence of ageing on the catalytic activity of manganese sludge for oxidation of Mn (II)
- Tez No: 105382
- Danışmanlar: YRD. DOÇ. DR. NEŞE TÜFEKÇİ
- Tez Türü: Yüksek Lisans
- Konular: Çevre Mühendisliği, Environmental Engineering
- Anahtar Kelimeler: Katalitik etki, Manganez, Oksitlenme, Çamur, Catalytic effect, Manganese, Oxidation, Sludge
- Yıl: 2001
- Dil: Türkçe
- Üniversite: İstanbul Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Çevre Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Mn(II)'NİN ATMOSFERİK OKSİJEN İLE OKSİDASYONUNDAN OLUŞAN ÇAMUR YAŞININ OKSİDASYON HIZINA ETKİSİ Bu çalışmada, Mn(n)'nin oksidasyonunda Mn(TV)'ün katalitik etkisi, Mn(TV) çamurunun (Mn02'nin) yaşlanmasıyla katalitik etki arasındaki ilişki ve doğal sularda bulunan organik maddelerin Mn(II)'nin oksidasyonuna olan etkileri ve özellikle ortamda organik madde bulunması halinde Mn(TV)'ün katalitik etkisindeki değişim incelenmiştir. Bu kapsamda aşağıda belirtilen üç aşamalı deneysel çalışmalar gerçekleştirilmiştir. Birinci aşamada, Mn(II)'nin oksidasyonu üzerine Mn(IV)'ün katalitik etkisi, kontrollü olarak 2 litrelik kesikli bir reaktörde, Mn(TV) konsantrasyonu 0-300 mg/1 arasında değiştirilerek incelenmiştir. 10 mg/1 ve 25 mg/1 başlangıç Mn(Ü) konsantrasyonlarında, oksijenin kısmi basmcı, alkalinite, pH ve sıcaklık sabit tutulmuştur. Sisteme Mn(IV) ilavesiyle gelişen heterojen oksidasyon ortamında, artan Mn(TV) konsantrasyonlan ile Mn(II)'nin oksidasyon hızının arttığı belirlenmiştir. İkinci aşamada, pH=8.5-9.5-10 değerlerinde 0-10 gün bekletilen çeşitli konsantrasyonlardaki Mn02 çamurlarının Mn(II)'nin oksidasyon hızına etkisi araştırılmıştır. pH'nm 9.5 olması halinde, Mn(TV)=50 mg/1 için, çamur yaşmm yedinci gününe kadar reaksiyon hızlanmaktadır. pH'nın 10 olması durumunda ise çamur yaşının dördüncü gününe kadar reaksiyon hızı artmıştır. Buradan, çamurun yaşlanmasıyla katalitik etkinin arttığı gözlenmiştir. Üçüncü aşamada ise aynı deney sistemi kullanılarak, tannik asitin oksidasyon hızını oldukça yavaşlattığı, asetik asitin ise herhangi bir etki yapmadığı tespit edilmiştir.
Özet (Çeviri)
ABSTRACT INFLUENCE OF AGEING ON THE CATALYTIC ACTIVITY OF MANGANESE SLUDGE FOR OXIDATION OF Mn(II) In the aquatic system manganese primarily involves the Mn(II) and Mn(IV) states, and is of engineering interest in water supply and wastewater treatment The oxidation of manganese is affected by several factors such as Mn(D) and oxygen concentration, pH, temperature, organic matter and other ions present in the solution. Manganese oxidation is also affected and is accelerated in the presence of the manganese dioxide. In the presence of Mn(TV), the oxidation of manganese by the atmospheric oxygen occurs by two simultaneous processes. One of these is the homogeneous reaction taking place in solution, and the other is the heterogeneous reaction occurring on the surface of the manganese dioxide precipitates. Thus: k Mn(D)+ O2 »> MnOx^ (homogeneous) (1) ki Mn(H) + MnOx(k) + 02 *“ 2MnOs<i) (heterogeneous) (2) The reaction rate under the constant pH and O2 concentration is given as: -d[Mn(H)] / dt - k[Mn(H)] + kt [Mn(H)] [Mn(IV)] (3) kcat = (k + ki[Mn(IV)]) (4) In the first chapter, the importance and the general objectives of the study are defined in detail. The chemistry of aqueous manganese and character of manganese precipitates are given, the kinetics of manganese oxidation and its oxygenation products in aqueous systems are explained. In the second chapter, the kinetics of manganese oxidation in contact aeration systems is investigated. The effects of the manganese concentrations and the effects of the sludge age on autocatalytic oxidation of manganese were examined. 1The study was carried out in three stages: In the first stage, the kinetics of manganese oxidation by atmospheric oxygen has been studied in batch systems. Mn(TV) concentrations were varied within the range of 0-300 mg/1, keeping partial pressure, pH, and temperature constant In the second stage effect of manganese dioxide sludge age on its catalytic effect has been investigated. Oxidation experiments have been simultaneously carried out for the sludge ages of 1 to 10 days for the same manganese concentration. In the third stage, the inhibition of Mn(II) oxidation by organic species involved the cyclic oxidation of Mn(II) followed by the reduction of Mn(TV) by the organic substances are explained. In the third chapter, the results of the experiment are discussed. The experimental results of the experiments with initial Mn(II) concentration of 10 mg/1 and with varying initial Mn(TV) concentrations are given. Catalytic rate constant, kcat is calculated from the slopes of the lines on linear of Mn(II) versus time. Time needed for the completion of the oxidation reaction is about 50 minutes when no Mn(TV) is present in the reactor. The reaction time is reduced to about 36 minutes when 300 mg/1 of Mn(IV) is added initially into the reactor. It has been found that kcat increases linearly with increasing Mn(TV) concentrations. In the first stage of this study, the oxidation of Mn(H) was studied in batch reactor in which the concentration of Mn(TV) was in the range of 0-300 mg/1. A quadratic equation has been found to represent the catalytic reaction rate constant as a function of Mn(TV). The kinetics of the catalytic reaction can be represented by linear expression in the concentration range of Mn(IV) 0-300 mg/1. Applying the curve fitting techniques to the data, the following equations are obtained between the kcat and Mn(TV) concentration. In the linear range, kcat is given as, kcat-k + kıIMnCIV)] (5)k^at = 0.0169 + 4x10 5[Mn(IV)I where [Mn(IV)]o indicates the initial Mn(IV) concentration. Oxygenation rate in terms of kcat and Mn(II) is, d(Mn(II)] / dt ^^.[MnCn)] (6) Assuming Mn(IV) is constant, integration of equation 6 yields [Mn(n)] = [Mn(n)]oe*catt (7) in which [Mn(D)]o is the initial Mn(D) concentration. Substituting the value of kcat obtained from equation 5 into equation 7 yields: fMnfll)] = [Mn(D)]0. ^”.t*w"W»'t (8) As a result of the experiments on the ageing of the sludge, it was found that the catalytic effect increased by ageing of the sludge. A decrease in the catalytic effect of Mn(TV) is expected because of the increase in the active surface area of Mn02 by ageing of the manganese sludge. However, the experimental data obtained are in contrast with these expectations. In the case of pH=9.5, the rate of the reaction is accelerated up to the 7th day, and almost no increase is observed beyond this day. At pH=10, the rate of the reaction is accelerated up to 4th day, and almost no increase is observed beyond this day. Thus it is found that the catalytic effect is increased by ageing the sludge. Also to find out the effect on the manganese oxidation tannic acid and acetic acid were added in batch systems. All of the other conditions were kept same as the other stage. Tannic acid completely inhibited the oxidation of manganese. During the experiments no observable effect had been determined on the oxidation reaction for acetic acid.
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