Biyolojik yöntemle üretilmiş gümüş nanopartikül bağlı aktif karbonun karakterizasyonu ve adsorpsiyon özelliklerinin incelenmesi
Characterization and adsorption properties of biologically synthesized silver nanoparticle attached activated carbon
Yazar: ŞEYDA KORKMAZ
Danışman: DR. ÖĞR. ÜYESİ HİKMET OKKAY
Yalova Üniversitesi / Fen Bilimleri Enstitüsü / Kimya ve Süreç Mühendisliği Ana Bilim Dalı / Kimya ve Süreç Mühendisliği Bilim Dalı
Derece: Doktora, 2019
Konu: Kimya Mühendisliği = Chemical Engineering

Özet:
Bu çalışmada, atık sulardan levofloksasin giderimi için biyolojik yöntemle sentezlenmiş antibakteriyel etkili adsorban geliştirilmiştir. Aktif karbon üretim aşamasında başlangıç maddesi olarak atık mantar kompostu ilk defa kullanılmış ve atıkların geri dönüştürülmesi sağlanmıştır. Çalışmanın ilk aşamasında en geniş yüzey alanına sahip aktif karbonun üretimi için optimum deney koşulları belirlenmiştir. Atık mantar kompostu, karbonizasyon aşamasından önce H3PO4 ile muamele edilerek gözenek yapısının gelişmesi için elverişli hale getirilmiştir. Karbonizasyon aşamasında karbonizasyon sıcaklığı (°C), impregnant oranı (g H3PO4/g atık mantar kompostu) ve karbonizasyon süresi  (dk) gibi üç önemli parametrenin aktif karbon verimi ve aktif karbonların metilen mavisi adsorpsiyon kapasitesi üzerine etkileri incelenmiştir. Karbonizasyon prosesi için deney koşulları Merkezi Kompozit Tasarım yöntemiyle belirlenmiştir. Deneysel çalışmalar sonucunda atık mantar kompostundan sentezlenen aktif karbonların verimi ve metilen mavisi adsorpsiyon kapasitesi için karbonizasyon sıcaklığı, impregnant (emdirme) oranı ve aktivasyon süresinin etkisini belirten istatistiksel modeller geliştirilmiştir. Model denklemler elde edilirken Merkezi Kompozit Tasarım temelli Cevap Yüzey Metodu kullanılmıştır. Elde edilen aktif karbonlardan en düşük, orta ve en yüksek metilen mavisi adsorpsiyon kapasitesine sahip olanların SEM, FTIR ve BET analizleri yapılmıştır. En geniş BET yüzey alanına sahip olan aktif karbon belirlenmiştir.
Çalışmanın ikinci aşamasında ultrases destekli biyolojik yöntemle gümüş nanopartikül üretimi için sentez koşulları optimize edilmiştir. Gümüş nanopartikül sentezinde indirgen ajan olarak biyolojik ve çevre dostu olması nedeniyle mısır koçanı ekstraktı kullanılmıştır. İndirgen ajan oranı (AgNO3/mısır koçanı ekstraktı), reaksiyon süresi (dk) ve ultrases gücünün (W) gümüş nanopartikül sentez verimine, partikül çapına ve morfolojisine etkisi incelenmiştir. En yüksek verimle elde edilen, küresel ve küçük çaplı gümüş nanopartikül sentezi için optimum koşullar belirlenmiştir. Gümüş nanopartiküllerin karakterizasyonu UV-görünür alan spektrofotometre, TEM, EDS ve XRD analizleriyle gerçekleştirilmiştir. En yüksek verimle elde edilen gümüş nanopartiküller, bir önceki aşamada elde edilen en geniş yüzey alanına sahip aktif karbona bağlanarak gümüş nanopartikül bağlı (katkılı) aktif karbon elde edilmiştir. Gümüş nanopartikül bağlı aktif karbon için TEM, EDS, XRD ve BET analizleri gerçekleştirilmiştir.
Bir sonraki aşamada, üretilmiş olan aktif karbon ve gümüş nanopartikül bağlı (katkılı) aktif karbonun adsorpsiyon özellikleri incelenmiştir. Öncelikli olarak, aktif karbon ve gümüş nanopartikül bağlı aktif karbonun levofloksasin adsorplama kapasitelerinin başlangıç konsantrasyonu ve temas süresiyle değişimini araştırmak için deneysel çalışmalar yapılmıştır. Elde edilen deneysel verilere göre, her iki adsorban için de Langmuir ve Freundlich adsorpsiyon izoterm modelleri ile Lagergren, yalancı ikinci dereceden kinetik model ve partikül içi kinetik modeller irdelenmiştir. 
Çalışmanın son aşamasında, aktif karbon ve gümüş nanopartikül bağlı aktif karbonun antibakteriyel özelliklerini belirlemek amacıyla disk difüzyon metodu kullanılmıştır. Her iki malzemenin gram-negatif Escherichia coli (E. coli) ve gram-pozitif Staphylococcus aureus (S. aureus) olmak üzere iki çeşit bakteriye karşı antibakteriyel özellikleri karşılaştırılmıştır. Tüm deneysel veriler ışığında, levofloksasin adsorpsiyonu için biyolojik yöntemle üretilmiş antibakteriyel özellikli bir adsorbanın etkinliği değerlendirilmiştir.
Yürütülmüş olan tez çalışmasında üstün adsorpsiyon özelliklerine sahip aktif karbon ve gümüş nanopartikül bağlı aktif karbon üretilmiştir. Aktif karbona gümüş nanopartikül bağlanmasıyla malzemenin antibakteriyel etki kazandığı Escherichia coli ve Staphylococcus aureus bakterileriyle yapılmış olan disk difüzyon metoduyla ispatlanmıştır. Ayrıca aktif karbonun levofloksasin adsorpsiyon kapasitesinde gümüş nanopartikül bağlanmasıyla birlikte %10 artış görülmüştür. Çalışmanın sonucunda elde edilen gümüş nanopartikül bağlı aktif karbon sayesinde, atıksulardan levofloksasin adsorpsiyonunda kullanıbilecek, ultrases destekli biyolojik yöntemle üretilmiş, antibakteriyel özellikli, çevre dostu, ekonomik ve sürdüreülebilir bir adsorban elde edilmiştir.

Abstract:
Biomass and biomass energy are used as a source of energy and chemical raw materials because of being economical, environmentally friendly and sustainable. For this purpose, countries with high level of development grow biomass resources and also prevent environmental pollution by using existing biomass wastes.
Biomass it is not preferred as a direct energy source due to its high moisture content and low calorific value, which results in low energy efficiency. Liquid and gas products obtained as a result of thermochemical conversion processes from biomass are considered as fuel with high calorific value while solid product is used as activated carbon because of its large specific surface area.
Activated carbon is considered to be a very effective adsorbent for various water pollutants due to its large surface area and porous structure. However, adsorbents should also have bactericidal properties for use in antibacterial applications. Furthermore, since the biocompatibility of activated carbon with microorganisms may enhance the growth of bacteria, silver nanoparticle attaching to activated carbon would be advantageous in terms of improving antibacterial properties. The agglomeration can be prevented by attaching silver nanoparticles to a support material. Activated carbon can be used as an ideal support material for silver nanoparticles due to its high surface area and pore volume.
The studies on the antibacterial properties of activated carbon and silver nanoparticles produced by environmentally friendly production methods have attracted attention with increasing environmental pollution and energy need. In addition to synthesis of silver nanoparticles using various methods, it is important to use environmentally friendly methods in terms of living life. Biological methods are more environmentally friendly than other silver nanoparticle production methods. Plant extract is most suitable for silver nanoparticle synthesis due to its ease of use and being non-toxic. Moreover, the use of plant extract as a reducing agent provides a low-cost method by recycling of wastes. 
The use of plant wastes as a reducing agent in the synthesis of silver nanoparticles with the biosynthesis method provides reducing the production costs and harmful effects of wastes to the environment. However, the use of plant extracts as reducing agents may cause longer reaction time. Sonication is used to overcome this problem and shorten the reaction time. Ultrasonic waves also provide the formation of smaller nanoparticles and prevent agglomeration which must be controlled in the nanoparticlesynthesis.
The wastes of industries such as textiles, pharmaceuticals, petroleum, paints, paper and food are released with water to the environment. Pollution in water threatens the whole life from microorganisms to humans. Biological, physical and chemical methods are used to remove water pollution. Adsorption is known as a simple and low cost method among water treatment processes. The adsorption process is the process of fluid to physically or chemically adhere to the solid surface and generally involves thermodynamic, kinetic and equilibrium studies. The parameters examined in the adsorption studies are the initial concentration of solution, temperature, pH, quantity and type of adsorbent. Adsorbent type is the most important variable which effects the adsorption efficiency. This situation led to the increase in adsorption studies and the importance of adsorbent production methods.
In this study, an antibacterial adsorbent which is synthesized by biological method for levofloxacin removal from waste water has been developed. In the activated carbon production step, recycling of wastes was provided by using spent mushroom compost as precursor of activated carbon. In the first step of the study, optimum experimental conditions were determined for the production of activated carbon having the largest surface area. The spent mushroom compost was impregnated with H3PO4 before the carbonization for the development of the pore structure. The effects of the three parameters such as carbonization temperature (°C), impregnant ratio (g H3PO4/g biomass) and carbonization time (min) on the yield and methylene blue adsorption capacity of activated carbon were investigated in the carbonization step. Experimental conditions for carbonization process were determined by Central Composite Design method. As a result of experimental studies, statistical models have been developed to determine the effect of carbonization temperature, impregnant ratio and carbonization time on the yield of activated carbons synthesized from waste mushroom compost and methylene blue adsorption capacity. Central Composite Design Based Response Surface Method was used to obtain the statistical models. The characterizations of activated carbons which have the lowest, medium and highest methylene blue adsorption capacity were performed by SEM, FTIR and BET analysis methods. 
In the second step of the study, synthesis conditions were optimized for the production of silver nanoparticles by ultrasound-assisted biological method. Corncob extract was used as reducing agent in the synthesis of silver nanoparticles because of being biological and eco-friendly. The effect of reducing agent ratio (AgNO3/corncob extract), reaction time (min) and ultrasound power (W) on silver nanoparticle synthesis efficiency, particle diameter and morphology were investigated. The optimum conditions for the synthesis of silver nanoparticles having spherical morphology and small diameter obtained with the highest yield were determined. Characterization of silver nanoparticles was performed by UV-visible spectrophotometer, TEM, EDS and XRD analysis methods. The silver nanoparticles obtained with the highest yield were attached to the activated carbon having the largest surface area to obtain the silver nanoparticle attached activated carbon. TEM, EDS, XRD and BET analyses were performed for silver nanoparticle attached activated carbon.
In the next step, the adsorption properties of activated carbon and silver nanoparticle attached activated carbon were investigated. Primarily, experimental studies have been carried out to investigate the effects of initial concentration and contact time on levofloxacin adsorption capacity of activated carbon and silver nanoparticle attached activated carbon. According to the experimental data, Lagergren, pseudo second order kinetic model and intra particle kinetic models were examined beside Langmuir and Freundlich adsorption isotherm models for both adsorbents.
In the final step of the study, disc diffusion method was performed to determine the antibacterial properties of activated carbon and silver nanoparticle attached activated carbon. The antibacterial properties of both materials against gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) were compared. According to experimental data, the levofloxacin adsorption efficiency of a biologically produced antibacterial adsorbent was evaluated.
Within the scope of the study, silver nanoparticle attached activated carbon produced from biomass wastes can be used as a low cost adsorbent with large specific surface area and can be used in the removal of antibiotics from wastewater. Due to the antibacterial properties of the silver nanoparticle, the adsorbent can provide the removal of antibiotics and bacteria at the single step. Thus, saving of time and cost will be ensured.
The spent mushroom compost used as precursor of activated carbon is obtained from the mushroom growers in the province of Yalova and has created an application area for the recycle of local wastes. In addition, low nutrient intake and low growth rates was observed in studies on the use of waste mushroom compost as animal feed. The lack of good feed for spent mushroom compost has led to a new field of application for the evaluation of this waste. Therefore, the production of activated carbon from spent mushroom compost is also important in terms of reducing wastes and environmental pollution.
The production of silver nanoparticles attached to activated carbon from plant wastes prevents the need for a coating step to prevent agglomeration of the nanoparticles. Because, the starch in plant wastes acts as caping agent and prevents agglomeration. In this way, silver nanoparticles were obtained in one step by an environmentally friendly method. In addition, corncob used as a reducing agent in the synthesis is one of the biomass wastes which has the highest capacity in our country. The biosynthesis method is also an application area for the recycle of these wastes. The use of ultrasound in the silver nanoparticle synthesis step and the attaching of synthesized nanoparticles to activated carbons provided to shorten the synthesis time and increased the yield.
In the literature, there is no study about the use of silver nanoparticle attached activated carbon produced from spent mushroom compost by ultrasound supported biological method and the use of this material in the removal of antibiotics from waste water. Furthermore, the use of waste mushroom compost as a starting material for activated carbon, the use of corncob as reducing agent in silver nanoparticle synthesis and the effect of ultrasound power on silver nanoparticle synthesis have not been studied before. Therefore, the proposed work is novel in several aspects.
In this study, activated carbon and silver nanoparticle attached activated carbon with superior adsorption properties were produced. The antibacterial effects of both produced materials were proved by disc diffusion method with Escherichia coli and Staphylococcus aureus bacteria. The levofloxacin adsorption capacity of the silver nanoparticle attached activated carbon was increased by 10% compared to activated carbon. The silver nanoparticle attached activated carbon produced by ultrasound assisted biological method can be used for the removal of levofloxacin from wastewater.