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Ayçiçek sapından sülfürik asit kullanılarak biyokömür üretimi, karakterizasyonu ve sulu çözeltilerden bazı mikrokirleticilerin gidermindeki etkinliğinin incelenmesi

Production of biochar from sunflower stalk using sulphuric acid, its characterization and investigation of its effectiveness in removal of some micropollutants from aqueous solutions

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  1. Tez No: 947466
  2. Yazar: SÜLEYMAN UZUN
  3. Danışmanlar: PROF. DR. MUSTAFA İMAMOĞLU
  4. Tez Türü: Yüksek Lisans
  5. Konular: Kimya, Chemistry
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2025
  8. Dil: Türkçe
  9. Üniversite: Sakarya Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Kimya Ana Bilim Dalı
  12. Bilim Dalı: Analitik Bilim Dalı
  13. Sayfa Sayısı: 75

Özet

Bakır elementi sulu çözeltilerde genellikle +2 yükseltgenme değerliğinde bulunmaktadır. Bakır (II) iyonları düşük derişimlerde insan sağlığı için zararlı olmamasına karşın yüksek derişimleri başta insan olmak üzere diğer canlılar için toksik özellik göstermektedir. Bakır (II) iyonlarını sulu çözeltilerden gidermek amacıyla sementasyon, adsorpsiyon, membran filtrasyonu, ultrafiltrasyon, elektokimyasal yöntemler ve fotokataliz gibi yöntemler kullanılmaktadır. Bunların arasında adsorpsiyon basit olarak uygulanabilirliği, maliyeti ve verimliği gibi nedenlerle öne çıkmaktadır. Bakır(II) iyonlarının sulu çözeltilerden giderilmesinde biyokömür kullanımı gittikçe önem kazanmaktadır. Bu tez çalışmasında, ayçiçeği saplarından sülfürik asit kullanılarak oda sıcaklığında biyokömür (AYBK) hazırlandı. Üretilen biyokömür kısmi analizler ve FTIR ve SEM-EDS analizleri ile karakterize edildi. Ardından Cu(II) iyonlarının sulu çözeltilerden kesikli (batch) yöntem ile giderilmesi araştırıldı. Bu yöntemde etkili olan faktörler olan sulu fazın pH'sı, AYBK dozajı, Cu(II) başlangıç derişimi, ajitasyon süresi ayrı ayrı incelendi. Cu(II)'nin AYBK üzerinde adsorpsiyon denge verileri Langmuir ve Freundlich eşitliklerine uygulanarak incelendi. AYBK'nın kısmi analiz sonuçlarına göre rutubeti % 10,6, uçucu madde miktarı % 35,3 ve kül miktarının % 9,3 olarak bulunmuştur. Diğer taraftan BET yüzey alanı ise 7,9 m2/g olarak bulunmuştur ki yapısının gözenekliliğinin çok küçük olduğunu göstermektedir. Bu bulgu SEM görüntüleri ile de doğrulanmaktadır. EDS analiz sonuçlarına göre AYBK'nın % 60,17 karbon ve % 35,48 oksijen içerdiği bulunmuştur. Ayrıca yapısında eser düzeyde inorganik safsızlıklar bulunduğu tespit edilmiştir. FTIR analizi sonucunda AYBK'nın yapısında fenolik ve asidik hidroksil gruplarının mevcudiyeti ortaya çıkmıştır. AYBK ile Cu(II) adsorpsiyon deneylerinde en verimli pH değeri pH 5,0 ve adssorpsiyonun dengeye erişme süresi 300 dk. olarak bulunmuştur. AYBK ile Cu(II) adsorpsiyonunda Cu(II) başlangıç derişimin artması adsorplanan Cu(II) miktarının artmasına neden olmuştur. AYBK ile Cu(II) adsorpsiyon dengesinin Langmuir izotermi ile uyumlu olduğu ve maksimum adsorpsiyon kapasitesinin 128,2 mg/g olduğu bulunmuştur. AYBK ile Cu(II) adsorpsiyon kinetiği yalancı ikinci mertebeden kinetik model üzerinden yürüdüğü sonucuna varılmıştır. Ayçiçeği saplarından sülfürik asit kullanılarak üretilen AYBK'nın sulu çözeltilerden Cu(II) iyonlarını sulu çözeltilerden verimli bir şekilde giderebildiği sonucuna varılmıştır.

Özet (Çeviri)

Industrial production plays a vital role in the development of human society, but the release of industrial wastes, especially heavy metal-polluted waters, into the environment and nature without treatment causes serious environmental pollution (Zhang et al. 2024). Heavy metals mainly refer to elements with relative atomic masses between 63.5 and 200.6, specific gravity greater than 5.0 and atomic density greater than 4.5 g/cm-3 (Liu et al. 2023). Copper is among the heavy metals widely used in industry, and as a result, Cu(II) is among the pollutants frequently encountered in industrial wastewater. Copper element is generally found in +2 oxidation state in aqueous solutions. Although copper (II) ions are not harmful to human health in low concentrations, Cu(II) is toxic to humans and other living organisms, in high concentrations. In order to remove Cu(II) ions from aqueous solutions, various methods such as cementation, adsorption, membrane filtration, ultrafiltration, electrochemical methods and photocatalysis have been used (Ab Hamid et al., 2022). Among these, adsorption technique stands out due to its simple applicability, cost and efficiency (Ozer and İmamoglu, 2024). In the adsorption method, various materials such as activated carbon, biochars (Chung et al., 2025), chelating resins (García-Elías et al., 2025), polymeric adsorbents (Rostami et al., 2024), zeolites (Lunardi et al., 2024) and fly ash (Munyengabe et al., 2024) have been used. Various biochars such as orthophosphoric acid modified biochar from coconut shell (Yadav et.al. 2024), calcium chloride modified Medulla Tetrapanacis biochar (Liu et.al. 2025), biochar obtained from bamboo bark (Nguyen et.al. 2024), biochar obtained from camel manure (Wilson et.al. 2024) biochar obtained from Gum Seyal (Babeker et.al. 2025), ammonia modified sawdust biochar (Eleryan et.al. 2024) biochar-sodium alginate composite (Salem et.al. 2025), Tieguanyin tea biochar (Zhang et.al. 2024), biochar obtained from mushroom compost (Madzin et.al. 2025) have been reported in the literature. In this thesis study, biochar (AYBK) was prepared from sunflower stalks at room temperature using sulfuric acid. The produced biochar was characterized by partial analysis and FTIR and SEM-EDS analyses. Then, the removal of Cu(II) from aqueous solutions by batch method was investigated. The effective factors in this method such as pH of the aqueous phase, AYBK dosage, initial Cu(II) concentration, agitation time were investigated individually. The adsorption equilibrium data of Cu(II) on AYBK were investigated by applying Langmuir and Freundlich equations. In addition, the adsorption kinetics of Cu(II) on AYBK were investigated by using pseudo first and pseudo second order equations. According to the partial analysis results of the produced adsorbent AYBK, its moisture content was found to be 10.6%, its volatile matter content was found to be 35.3 and its ash content was found to be 9.3%. On the other hand, the BET surface area was found to be 9 m2/g, which shows that the porosity of its structure is very small. This finding is also confirmed by SEM images. According to the EDS analysis results, it was found to contain 60.17% carbon and 35.48% oxygen. In addition, there are trace levels of inorganic impurities in its structure. As a result of FTIR analysis, the presence of phenolic and acidic hydroxyl groups in its structure was revealed. In the adsorption studies of Cu(II) with AYBK, it was found that pH was very effective on Cu(II) adsorption. For example, at pH 2.0, Cu(II) adsorption did not occur at all, and began to occur after pH 3.0. It reached its maximum level at pH 4.0 and 5.0. Higher pH values were not examined due to possible precipitation copper hydroxide species. It was found that the mixing time was also effective on Cu(II) adsorption onto AYBK, and it was found that a period of five hours was required for Cu(II) ions to reach and bind to the adsorption sites on the surface of AYBK. The effect of AYBK dosage on the Cu(II) adsorption, various amounts of AYBK were added to Cu(II) solutions at a concentration of 300 mg/L and pH 5.0 in 50 mL volume. The percentage of Cu(II) removed from the aqueous phase increased with the amount of AYBK added, as expected. However, since the amount of Cu(II) adsorbed is inversely proportional to the mass of AYBK, the amount of Cu(II) retained per gram of AYBK in milligrams decreased. The effect of the initial concentration on Cu(II) adsorption with AYBK was also investigated, and the increase in the initial concentration of Cu(II) caused the amount of Cu(II) retained per gram of AYBK in milligrams to increase. This is an expected event, because the analyte concentration is the driving force in adsorption process. The amount of adsorbed Cu(II) reaches a maximum level of 115.0 mg/g. After this point, increasing the initial concentration of Cu(II) adsorption does not cause any increase in Cu(II) adsorption. The effect of Cu(II) ionic strength on Cu(II) adsorption with AYBK was also investigated by adding sodium chloride to the aqueous phase at different concentrations, and the amount of adsorbed Cu(II) decreased from 115.0 mg/g to 85.0 mg/g as the NaCl concentration increased from zero to 0.1 M. The same value of 85.0 mg/g Cu(II) was found when the NaCl concentration increased to 1.0 M. The Cu(II) adsorption equilibrium with AYBK was analyzed with Langmuir and Freundlich isotherms. The correlation coefficient of the Langmuir isotherm was found to be 0.9926, while that of the Freundlich isotherm was obtained as 0.9272. Accordingly, it was decided that Cu(II) adsorption with AYBK was compatible with the Langmuir isotherm. On the other hand, the maximum mono layer adsorption capacity of AYBK calculated with the Langmuir isotherm was found to be 128.2 mg/g. This value is also compatible with the experimentally obtained maximum adsorption capacity (127.5 mg/g). In the literature, the reported Cu(II) capacities were varied between 2.6 mg/g and 945.6 mg/g, many of them was in the range of 100 mg/g and 200 mg/g. When the Cu(II) adsorption capacity of AYBK adsorbent was compared with the others, it could be stated that it had a medium level Cu(II) capacity. The adsorption kinetics of Cu(II) with AYBK was investigated by applying the pseudo-first-order kinetic model and pseudo-second-order kinetic model equations. When the experimental and model predicted qe values were compared, it was seen that the qe value predicted by the pseudo-first-order kinetic model (40.3 mg/g) was very far from the experimental qe value (115.0 mg/g). The qe value predicted by the pseudo-first-order kinetic model (116.3 mg/g) was found to be very near to the experimental qe value. On the other hand, the correlation coefficient of the pseudo-second-order kinetic model (0.9924) was much closer to unity than that of the other model. Therefore, it was concluded that the adsorption kinetics of Cu(II) with AYBK proceeded through the pseudo-second-order kinetic model. As a result, it was concluded that the produced AYBK could efficiently remove Cu(II) ions from aqueous solutions.

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