Çeşitli adsorbanlarla fosfat giderilmesi
Başlık çevirisi mevcut değil.
- Tez No: 55724
- Danışmanlar: PROF. DR. A. NURSAN İPEKOĞLU
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kimya Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 73
Özet
ÖZET Günümüzde, yeryüzü sularının çoğu, evsel ve endüstriyel faaliyetler ile doğal olaylardan dolayı kirlenmekte ve sularda bulunan organik ve inorganik kirleticiler doğal hayatı tehdit etmektedir. Doğal hayatı tehdit eden maddeler arasında bulunan ve sulardaki biyolojik hayat için anahtar element olan fosfor, ötrofikasyona sebep olmaktadır. Çeşitli kaynaklardan yeryüzü sularına karışan fosfor çeşitli yöntemlerle giderilebilir. Bu çalışmada sentetik olarak hazırlanmış fosfat çözeltileriyle pirinç kabuğu, mısır koçanı, yer fıstığı kabuğu gibi tarım atıkları ve yurdumuzda önemli miktarda bulunan bentonit ile çalışılmıştır. Tarım atıklarından iyi sonuç alınamamış, bentonit ile yapılan çalışmalarda fosfat adsorpsiyonu üzerine adsorbanın partikül çapının ( Dp ), adsorbanın miktarının ( Ws ), başlangıç fosfat konsantrasyonunun ( C0 ) ve temas süresinin ( t ) etkisi incelenmiştir. MU
Özet (Çeviri)
SUMMARY PHOSPHATE REMOVAL WITH VARIOUS ADSORBENTS Phosphorus, P, atomic weight 30.98, is in Group VA of the periodic table just below nitrogen. Solid elemental phosphorus exists in several allotropic forms. The best-known and most important commercially is ot-White phosphorus or yellow phosphorus. Depending on the crystallite size, the pure material is a colorless or white waxy solid with a density of 1.82 g / cm3. It melts at 44,1 C° to a clear, colorless liquid. Commercial white phosphorus, which is 99.9 % pure, has a slight yellowish color and melts to a straw-colored liquid. It soluble in carbon disulfide, ether, benzene, and other organic solvents and it boils at 280,5 C°. Phosphorus occurs in natural waters and in wastewaters almost solely as phosphates. Phosphates may be defined very broadly as compounds containing four phosphorus-oxygen ( P-0 ) linkages. The term phosphate is used in the traditional sense, referring to compounds in which phosphorus atoms are surrounded by a tetrehedron of four oxygen atoms. By sharing oxygen atoms between tetrahedra, chains, rings, and branched polymers of interconnected P04, tetrahedra can be formed. Compounds containing discrete, ie, monomeric P04'3 ions are known as orthophosphates or simply phosphates, linear P-O-P chains as polyphosphates, cyclic rings as metaphosphates, and branched polymeric materials and cage anions as ultraphosphates. These compounds of phosphate arise from a variety of sources. Small amounts of certain condensed phosphates are added to some water supplies during treatment. Larger quantities of the same compounds may be added when the water is used for laundering or other cleaning, because these materials are major constituents of many commercial cleaning preparations. Phosphates are used extensively in the treatment of boiler waters. Ortophosphates applied to agricultural or residential cultivated land as fertilizers are carried into surface waters with storm runoff and to a lesser extent with melting snow. Organic phosphates are formed primarily by biological processes. They are contributed to sewage by body wastes and food residues, and also may be formed from orthophosphates in biological treatment processes or by receiving water biota. IXThe presence of phosphate in wastewaters provides an additional growth-limiting nutrient in the near static water bodies. As a result, an excessive growth of photosynthetic aquatic micro- and macro- organisms is encouraged in such water bodies which ultimately becomes a major cause for the europhication of such receiving waters. Removal of phosphate from the wastewaters can, therefore, be an effective method for the control of eorophication in lakes and similar water bodies.. Inorganic phosphates present no hazard to humans and are essential to life processes. Problems apparently caused by sewage-borne phosphates are mostly localized to areas that have traditionally employed lakes as receiving water for sewage effluents. Average phosphorus concentrations vary in municipal sewage for several reasons, including industrial waste input, storm waters, seasonal fluctuations, and daily living-habit cycles. Extreme values range between 3 and 1 5 mg / 1. The chemical form of phosphorus in waste varies, including soluble orthophosphates, condensed phosphates, insoluble salts, and numerous forms of organic phosphorus. Mankind cannot prohibit phosphorus, as it is an essential part of the natural order the world. However, it has to be controlled when necessary. Specialized tertiary treatment methods, such as adsoprtion and / or precipitation, are practiced for the removal of phosphate from the wastewaters. Phosphate removal through adsorbents, such as activated alumina, powdered aluminum oxide, activated red mud, flyash, blast furnace slag and other materials, is commonly and successfully practiced. These adsorbents are, however, not easily and / or economically available everywhere. Adsorption, the commonly used method of phosphate ( P04“3 ) removal, employ numerous adsorbents such as above. By using high calcium flyash for phosphate removal, a very high adsorbent dose requirement of 25 g / I for about 98 % phosphate removal from initial phosphate concentration of 5.6 mg / 1 is reported. With activated red mud it is reported as much as 72 % phosphate removal at equilibrium. The resulting activated carbon exhibited efficient sorption capabilities for wastewaters. Sorbate molecular mass was found to have a significant effect on the sorption, while its solubility and polarity had insignificant effects. By using slag as a by-product in the iron ore it is observed that the amount of phosphate adsorbed increased but the percent phosphate removal decreased with increasing initial phosphate concentrations. It is concluded that phosphate removal efficiencies were higher for lower initial phosphate concentrations, lower pH and higher adsorbent doses.Cationic and anionic ion exchange beds are used for phosphate removal. In fixed beds are using activated alumina as high as 99.9 % phosphate removal is reported. Phosphate removal through electrolysis using iron and aluminum electrodes is tried and reported a highest phosphate removal of greater than 95 % in 256 s. These adsorbents are, however, not easily and / or economically available everywhere. In this study, it was investigated that the adsorption of phosphate from water by different adsorbents. There is a need to procedure low cost adsorbents that can be applied to pollution control. Therefore, as adsorbents corncobs, rice hulls, peanut sells and bentonites were used in this search. As organic agricultural waste is usually available in large quantities, there is, therefore, no shortage of starting materials. Corncobs, rice hulls and peanut shells are cheap raw material and in abundant supply. Bentonites are also natural minerals which it can be found easily in Turkey. Corncobs, rice hulls and peanut shells ere initially treated with 1 % H2S04 for activation and then extracted with ethanol to remove the other organics and washed with distilled water. The washed products were dried at 60 ° C. It is called as Activation Method 1. Then same adsorbents were treated except step of treatment with 1 % H2SO4 of Activation Method 1. This method is called as Activation Method 2. By using these adsorbents which organic base for phosphate removal, a very high adsorbent dose requirement. These adsorbents failed on phosphate removal, therefore bentonites managed phosphate removal. Phosphorus analyses embody two general procedural steps: (a ) conversion of the phosphorus form of interest to dissolved orthophosphate, and (b ) calorimetric determination of dissolved orthophosphate. The separation of phosphorus into its various form defined analytically but the analytical differentiations have been selected so that they may be used for interpretive purposes. Filtration through a 0.45-nm-pore-diam membrane filter separates dissolved from suspended forms of phosphorus. No claim is made that filtration through 0.45 nm filters is a true separation of suspended and dissolved forms of phosphorus: it is merely a convenient and replicable analytical technique designed to make a gross separation. XIMembrane filtration is selected over depth filtration because of the greater likelihood of consistent separation of particle sizes. Prefiltration through a glass fiber filter may be used to increase the filtration rate. Phosphates that respond the calorimetric tests without preliminary hydrolysis or oxidative digestion of the sample are termed ”reactive phosphorus u. While reactive phosphorus is largely a measure of orthophosphate, a small fraction of any condensed phosphate present usually is hydrolyzed unavoidably in the procedure. Reactive phosphorus occurs in both dissolved and suspended forms. Acid hydrolysis at boiling-water temperature converts dissolved and particulate condensed phosphates to dissolves orthophosphate. The hydrolysis unavoidably releases some phosphate from organic compounds, but this may be reduced to animism by judicious selection of acid strength and hydrolysis time and temperature. The term“ acid-hydrolyzable phosphorus ”is preferred over“ condensed phosphate ”for this fraction. The phosphate fractions that are converted to orthophosphate only by oxidation destruction of the organic matter present are considered“ organic ”or“ organically bound ”phosphorus. The severity of the oxidation required for this conversion depends on the form - and to some extent on the amount- of the organic phosphorus present. Like reactive phosphorus and acid-hydrolyzable phosphorus, organic phosphorus occurs, both in the dissolved and suspended fractions. The total phosphorus as well as the dissolved and suspended phosphorus fractions each may be divided analytically into the three chemical types that have been described: reactive, acid-hydrolizable, organic phosphorus. In this study vanadomolybdophosphoric acid calorimetric method is used. As principle, in a dilute orthoposphate solution, ammonium molybdate reacts under acid conditions to form a heteropoly acid, molybdophosphoric acid formed. The intensity of the yellow color is proportional to phosphate concentration. This method is used except sample pH adjustment, color removal from sample. In this study synthetic phosphate solutions are used. Chosen desired concentration of the KH2P04 solutions shaken on a radial bench shaker for the desired durations of the contact times of the tests. The bottles were also shaken for sufficiently long times to attain an equilibrium which was ascertained and ensured through the last two consecutive readings of the residual phosphate concentrations being identical. After attainment of equilibrium, the bottles contents were filtered through 0.45 jim Millipore filter paper and analyzed for residual phosphate concentrations.Operating variables on the performance evaluation of the adsorbents for adsorption of phosphates are size of adsorbents particles ( Dp ), adsorbent dose ( Ws ), initial adsorbate concentration ( C0 ) and contact time duration ( t ). At all adsorbent particle sizes, the percent phosphates removal at equilibrium increased with increasing adsorbent doses. For any adsorbent dose, the percent phosphates adsorbed was higher for smaller adsorbent size. This is because adsorption being a surface phenomenon, the smaller adsorbent sizes offered comparatively larger surface areas and hence higher phosphate removal at equilibrium. The total phosphates adsorbed increase rapidly in the beginning and very slowly toward the and of the run. The percent phosphates removal at any contact time increases with increase in the adsorbent dose. Bentonites is seen to yield an isotherm model in form to the Freundlich isotherm. XIU
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