Yüksek tuzluluk içeren turşu atıksularından fiziko-kimyasal yöntemlerle laktik asit geri kazanımı
Lactic acid recovery from pickle wastewater containing high salty by physicochemical methods
Yazar: EZGİ AYIŞIĞI
Danışman: PROF. DR. EMİNE ÇOKGÖR ; DOÇ. DR. DİĞDEM GÜVEN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri, Mühendisliği ve Yönetimi Bilim Dalı
Derece: Yüksek Lisans, 2020
Konu: Çevre Mühendisliği = Environmental Engineering
Dizin: Adsorpsiyon = Adsorption ; Atık su = Waste water ; Biyoplastik = Bioplastic ; Fizikokimyasal yöntemler = Physicochemical method ; Geri kazanma =   ; Gıda atıkları = Food wastes ; Laktik asit = Lactic acid ; Salamura = Brine ; Turşu = Pickle

Özet:
YÜKSEK TUZLULUK İÇEREN TURŞU ATIKSULARINDAN FİZİKO-KİMYASAL YÖNTEMLE İLE LAKTİK ASİT  GERİ KAZANIMI
ÖZET
Konvansiyonel olarak bilinen petrol kökenli plastiklerin yol açtığı çevresel etkiler sebebiyle yerlerini alabilecek alternetifler araştırılmakta ve çalışmalar yürütülmektedir. Dayanım, esneklik gibi özellikleriyle geleneksel plastiklere benzerlik gösteren biyoplastikler, biyolojik olarak bozunurluk ve yenilenebilir kaynaklı olmaları açısından petrol bazlı plastiklere alternatif olmaktadırlar. 
Bu çalışmada biyoplastikler için yenilenebilir kaynak olarak turşu endüstrisi üretim proses atıksuyu kullanılarak poli laktik asit (PLA) biyopolimeri üretimi için atıksudan laktik asit geri kazanımı çalışmaları yürütülmüştür. Yüksek derecede tuzluluk içeren bu endüstriyel atıksuyun karakterizasyonu belirlenmiş ve biyopolimer üretimi için uygunluğu değerlendirilmiştir. Laktik asit geri kazanımı için reçinenin tekrar kullanılabilmesi, işletme kolaylığı ve ucuzluğu gibi avantajlarıyla adsorpsiyon prosesinin yanı sıra, yüksek saflaştıma, ayırma olanağına sahip membran prosesler ile ayırma işlemleri de çalışılmıştır.
Adsorpsiyon prosesi için organik asitlerin kompleks karışımlardan ayrılması amacıyla kullanıldığı bilinen Lewatit Monoplus M500, MP-62, MP-68 ile Amberlite IRA 67 ve IRA 402 sentetik reçinleri tercih edilmiştir. En iyi laktik asit geri kazanım koşullarını belirlemek için farklı pH, reçine miktarları denenmiştir. İlk aşamada, hazırlanan sentetik laktik asit çözeltileriyle reçinelerin laktik asit tutma/ayırma kapasitesini belirlemek için izoterm çalışmaları gerçekleştirilmiştir. Lewatit MP62 reçinesinin pH 2,3 değerinde maksimum laktik asit tutma kapasitesinin 313-535 mg KOİLA/g reçine aralığında olduğu ve daha çok Freundlich izoterm modeline uyumlu olduğu tespit edilmiştir. MP68 ve M500 reçineleriyle yapılan çalışmalarda laktik asit tutma kapasiteleri sırasıyla 225 mg LA/g reçine ve 31mg LA/g reçine olduğu belirlenmiş olup MP68 reçinesinin Freundlich ve Langmuir izotermlerinin ikisiyle de uyumlu olduğu tespit edilmiştir. M500 reçinesi ile aynı koşullarda elde edilen laktik asit tutulumunun diğer reçineler göre çok daha düşük olduğu ve sonuçların izoterm modelleriyle uyumlu olmadığı görülmüştür. Diğer reçine grubu olan Amberlite IRA67 ve IRA402 il eyapılan çalışmalarda IRA67 reçinesinin laktik asit tutma kapasitesi 246 mg LA/g reçine olarak hesaplanırken IRA402 reçinesinin kapasitesinin 38 mg LA/g reçine olduğu tespit edilmiştir. Aynı reçineler ile salamura atıksuyu ile farklı pH'larda çok sayıda izoterm çalışması gerçekleştirilmiştir. Ancak, sentetik çözelti çalışmalarında laktik asit tutma kapasitesi yüksek olan bu reçinelerin salamura atıksuyunda laktik asit ayırımı yapamadığı görülmüştür.
Yüksek tuzluluk içeren turşu endüstrisi proses atıksuyu ultrafiltrasyon, laktik asit için uygun olan membran prosesi olan nanofiltrasyon ve yüksek tuz içereği sebebiyle ters osmoz çalışmalarına tabi tutulmuştur. Salamura atıksuyu öncelikle ultrafiltrasyonandan (30kDa) geçirilmiştir. Buradan elde edilen atıksu süzüntüsü nanofiltrasyon (NF90 ve NF270) ve ters osmoz (BW30) membranlarından geçirilmiştir. NF90 ve NF270 membranından geçen atıksudan %16 ve ters osmozda %6 oranında laktik asit tutulumu gözlenmiştir. Ters osmoz için pH ayarı ile organik asitlerin tutulumu salamura atıksuyu ile mümkün olmadığı gözlenmiştir.
Bu çalışmada yüksek tuzlulukta fermantasyon atıksuyu olan turşu endüstrisi üretim prosesi atıksuyunda (salamura) polilaktik asit üretimi amacıyla laktik asit geri kazanımının adsorpsiyon ve membran proseslerle mümkün olmadığı ortaya konulmuştur. Projenin (TÜBİTAK 117Z658 Nolu 1003-KMY-ANAK) diğer iş paketlerinde gerçekleştirilen mikrobiyal polihidroksialkonat (PHA) üretiminin başarılı olduğu görülmüştür. Bu sebeple, turşu endüstrisi atıksularından biyopolimer üretimi için fizikokimyasal yöntemlerle laktik asit ayırımı yerine doğrudan mikrobiyal PHA üretiminin uygulanabileceği sonucuna varılmıştır.

Abstract:
LACTIC ACID RECOVERY FROM PICKLE WASTEWATER CONTAINING HIGH SALTY BY PHYSICOCHEMICAL METHODS
SUMMARY
Plastics have found wide use for many years due to their strength, flexibility and long life. Most of the commonly used plastics are produced from petroleum. Since they can survive in nature for a long time, we have recently come across with environmental pollution. Increasing plastic pollution causes possible alternatives to be investigated. The most common alternative here are bioplastics. Biodegradable plastics can be degraded by sunlight, under the influence of microorganisms such as bacteria, fungi in soil, water and mud environments. In addition, bioplastics have lower greenhouse gas emissions during the production phase compared to fossil fuel-based plastics. Bioplastics, which are alternative for sustainable environment and economy, should be used widespread with the development of technology and cheap raw material resources should be investigated. In recent years, our country and the EU have restricted the use of petroleum-based plastics within the framework of the circular economy (e.g. use of plastic bags). However, bio-based plastics were also supported. Bioplastics, which are similar to traditional plastics with their properties such as strength and flexibility, are a strong alternative to petroleum-based plastics with their properties such as biodegradable and renewable. 
Some or all of the content of (bio-based) plastics produced from biological material consists of renewable resources (starch, vegetable oil, cellulose, microbiota). Since the raw material of biopolymers is generally food-based, problems can occur in food management. Food waste is an important source of raw materials for biopolymer production, especially because of its content. When waste is used as raw material, the lands reserved for production will be able to be separated into food, and also waste will be utilized. Sustainable food and waste management can be achieved through the use of wastes as raw materials. In addition, it is aimed to reduce production costs by using wastes as raw materials for bioplastics. 
Polylactic acids (PLA), which are similar to conventional plastics with their properties such as strength, flexibility and easy workability, but are biodegradable, are a strong alternative to petroleum-based plastics in bioplastics. Due to its easy processability and durability, it can be used as a sewing thread for surgeries due to food packaging, prosthesis making and biodegradability, and it appears as a printing material in 3D printers. Its area of use has an undeniable width and is increasing day by day. Poly lactic acid (PLA) is produced by chemical synthesis of lactic acid monomers. Lactic acid, the raw material of polylactic acids, is a substance with a commercial value alone and a wide range of uses (food industry, leather industry, construction industry, etc.). Food wastes have lactic acid content or take part as raw material in lactic acid production by fermentation. Regarding the use of wastes in bioplastic/lactic acid production, it is possible to recover or directly recover them by producing lactic acid from food wastes. There are studies on the production and recovery of lactic acid from waste, but there is no lactic acid recovery study specifically designed to produce poly lactic acid (PLA) from the pickle industry process wastewater. After obtaining from wastes / wastewater by lactic acid recovery and purification methods, poly lactic acid production phase is started. Methods such as ion exchange chromatography, extraction (solvent extraction and reactive extraction), distillation, membrane processes, electrodialysis, precipitation, ion exchange and adsorption are used in lactic acid recovery and purification.
In this study, lactic acid recovery studies were carried out from wastewater for the production of poly lactic acid (PLA) biopolymer using pickle industry production process wastewater as a renewable resource for bioplastics. The pickle industry process wastewater (brine) has a content rich in carbon source and organic acid. Pickle industry wastewater was characterized in detail and its suitability for biopolymer production has been evaluated. The adsorption process used in this study was preferred because it does not require additional chemicals, resins can be reused, high purity material recovery and is a cheap method. Membrane processes, on the other hand, were preferred due to their high purity of substance recovery and high salinity of brine wastewater.
In order to determine the lactic acid adsorption capacity of synthetic resins to be used in the recovery of lactic acid from wastewater for the adsorption process and the optimum amount of resin to be used, adsorption isotherm experiments were carried out under different conditions using synthetic lactic acid solution. Lewatit Monoplus M500, MP-62, MP-68 and Amberlite IRA 67 and IRA 402 synthetic resins, which are known to be used to separate organic acids from complex mixtures, were preferred. Different pH and resin amounts were tried to determine the best lactic acid recovery conditions. Due to the feature of the resins of brine wastewater, the effect of lactic acid recovery was studied with chloride (Cl-) and phosphate ion (PO4-3) in the synthetic solution. In the presence of phosphate ions, lactic acid retention performance did not change. It has been determined that the maximum lactic acid adsorption capacity of MP-62 resin at pH 2.3 is in the range of 313-535 mg CODLA/g resin and it is more compatible with Freundlich isotherm model. In studies conducted with MP68 and M500 resins, lactic acid retention capacities were determined to be 225 mg LA / g resin and 31 mg LA / g resin respectively, and MP68 resin was found to be compatible with both Freundlich and Langmuir isotherms. It has been determined that M500 resin is not compatible with any isotherm models. In the studies conducted with other resin group Amberlite IRA 67 and IRA402, the lactic acid holding capacity of IRA 67 resin was calculated as 246 mg LA / g resin, while the capacity of IRA 402 resin was 38 mg LA / g resin. In the experiments carried out in brine wastewater, no resin was successful in holding lactic acid. In synthetic solution studies, it has been observed that these resins with high lactic acid holding capacity cannot distinguish lactic acid in brine wastewater.
Membrane filtration processes (ultrafiltration nanofiltration, reverse osmosis) were performed in the pickling industry process wastewater with high salinity in order to recover lactic acid and was subjected to reverse osmosis studies due to nanofiltration and high salt content, which is the membrane process suitable for lactic acid. Brine wastewater was first passed through ultrafiltration (30 kDa). While pH adjustment is not done in the brine that goes into ultrafiltration, the pH is adjusted to 5 by keeping lactic acid in lactate form in other membrane processes. The wastewater filtrate obtained here was passed through nanofiltration (NF90 and NF270) and reverse osmosis (BW30) membranes. Lactic acid uptake was observed at a rate of 16% through wastewater passing through NF90 membrane. There is a 6% retention of lactic acid in reverse osmosis. It has been observed that the retention of organic acids with pH adjustment for reverse osmosis is not possible with brine wastewater.
In this study, it has been demonstrated that lactic acid recovery is not possible with adsorption and membrane processes in order to produce polylactic acid in the pickle industry production process wastewater (brine), which is a high salinity fermentation wastewater. This also applies to ultrafiltration / nanofiltration and reverse osmosis membrane processes. Ion exchange chromatography, diafiltration and liquid membrane applications can be tried. 
Biotechnological methods for biopolymer production carried out within the scope of TUBITAK 117Z658 No 1003-KMY-ANAK project where this thesis study was carried out were successful and is recommended for this type of wastewater. Microbial polyhydroxyalconate (PHA) production in other work packages of the project, which is part of the study, has been successful. Therefore, it was concluded that direct microbial PHA production can be applied instead of lactic acid separation by physicochemical methods for biopolymer production from pickle industry wastewater.