Bu tezde, farklı zincir uzunluğuna sahip lineer alkil aminlerin Pt(IV) iyonlarının sulu çözeltilerden katı faz ekstraksiyonu için etkinliği araştırılmıştır. Bu amaçla bis(3-aminopropil)amin (BAPA-SG) ve dietilentriamin (DETA-SG) olmak üzere iki farklı alkil zincir uzunluğa sahip amin bileşiği silika jelin yüzeyine kovalent bağla bağlanarak iki farklı modifiye silika jel hazırlanmıştır. Sentezlenen modifiye silika jeller, C,H,N elementel analizleri ve FTIR spektroskopisi ile karakterize edilmiştir. Modifiye silika jeller ile Pt(IV) iyonlarının katı faz ekstraksiyonu kesikli yöntem adsorpsiyon tekniği ile incelenmiştir. Pt(IV) iyonlarının BAPA-SG ve DETA-SG ile adsorpsiyonuna etki eden faktörler olan çözeltideki hidronyum ve klorür derişimi, karıştırma süresi ve Pt(IV) başlangıç derişimi araştırılmıştır. Pt(IV) iyonlarının adsorpsiyonunun 0,1 M hidronyum ve 0,1 M klorür içeren çözeltilerde en verimli olduğu gözlenmiştir. Pt(IV) iyonlarının başlangıç derişiminin artmasıyla adsorplanan Pt(IV) miktarının arttığı bulunmuştur. Pt(IV) iyonlarının adsorpsiyonunun bis(3-aminopropil)amin immobilize edilmiş silika jel ile 2 saatte ve dietilentriamin bağlı silika jel ile 4 saatte dengeye geldiği ve her iki modifiye silika jel üzerinde Pt(IV) adsorpsiyon kinetiğinin sahte ikinci derece kinetik model üzerinden yürüdüğü bulunmuştur. Bis(3-aminopropil)amin bağlı silika jel ve dietilentriamin bağlı silika jel ile Pt(IV) iyonlarının adsorpsiyonunun dengesinin Langmuir izotermiyle uyumlu olduğu ve maksimum adsorpsiyon kapasitelerinin sırasıyla 158,7 ve 227,3 mg/g olduğu hesaplanmıştır. Kolon katı faz ekstraksiyon deneylerinde numune hacmi ve akış hızı, elüentin türü, hacmi ve derişimi ile matriks iyonlarının etkisi incelendi. Her iki modifiye silika jel ile kolon katı faz ekstraksiyon tekniği ile Pt(IV) iyonlarının 500 mL hacmindeki numuneden kantitatif olarak adsorplanıp ardından asidik tiyoüre çözeltisi ile sıyırılarak kantitatif olarak geri kazanılabildiği bulunmuştur. Matriks iyonlarının etkilerinin incelendiği çalışmalar sonunda Pt(IV) iyonlarının iki modifiye silika jel ile geri kazanımının yüksek derişimdeki klorür iyonlarından etkilendiği görülmüştür. Ayrıca BAPA–SG ile Pt(IV) iyonlarının geri kazanımı 100 mg/L derişimdeki bakır(II) ve nikel (II) iyonlarından %90'nın altına düşerken DETA-SG ile geri kazanımların kantitatif olduğu gözlenmiştir. 1000 mg/L Ca(II) ve Mg(II) ile 2000 mg/L Na(I) ve K(I) içeren çözeltilerden Pt(IV) iyonlarının geri kazanımının iki modifiye silika jel ile de kantitatif olarak yapılabildiği bulunmuştur. Sonuç olarak, Pt(IV) adsorpsiyonunda ve geri kazanımında bis(3-aminopropil)amin bağlı silika jel ile dietilentriamin bağlı silika jelin kullanılabileceği ve dietilentriamin bağlı silika jelin Pt(IV) adsorpsiyonunda ve geri kazanımında daha verimli olduğu sonucuna varılmıştır.
EFFECT OF SPACER LENGTH BETWEEN N ATOMS OF LINEAR ALKYL TRIAMINES ON ADSORPTION OF ANIONIC PLATINUM(IV) IONS Platinum is a member of the platinum group metals (PGM) and is also classified among the noble metals having resistance to corrosion and oxidation. In addition, platinum group metals together with gold and silver are called precious metals because they are economically valuable. Platinum is scarce in the world, with important ores in Transvaal, South Africa, Sudbury, Canada and Siberia, Russia. Generally, PGMs are found with metal sulfides in low concentrations in ores and their concentrations are in the range of 2-10 g/tonne (Jha et al., 2013). Due to the extraordinary catalytic properties of platinum, it is widely used as a catalyst, especially in the chemical industry. In addition, it is widely used in the production of catalytic converter for automobile exhausts and in the jewelry industry. Despite its limited availability in the world, the demand for platinum is constantly increasing with the development of technology (Hughes et al. 2021). Therefore, recycling of platinum from secondary sources such as industrial wastes has become mandatory nowadays (Boudesocque et al., 2019). The selective recovery of Pt(IV) ions is an important step in the production of platinum by the hydrometallurgical method. Since oxidative reagents are used in this method, platinum ions are present as +4 valence in the obtained leaching solutions (Öztürk et al., 2020). On the other hand, Pt(IV) ions can be found in wastes produced from mining facilities and mine leachate. The release of these polluted waters to the environment without treatment and reaching of Pt(IV) ions to humans and other living things through the food chain can cause serious health problems such as DNA damage. Therefore, it is necessary to remove and recover Pt(IV) ions from these wastewaters (Mosai et al., 2020, Park et al., 2018). Electro-thermal atomic absorption spectrometry (ET-AAS), neutron activation analysis (NAA), inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) are used for the determination of Pt level in several samples including wastewater and ores etc.. However, Pt determination with these techniques is difficult due to the interference of matrix ions and the fact that the Pt concentration can be found below the detection limit of the instrument. In order to elimenate these problems, separation and pre-concentration procedures should generally be performed before determination step by the instrument (Abdulbur-Alfakhoury et al. 2021). Solid phase extraction (SPE), based on the use of solid adsorbents, is one of the most efficient methods used for the recovery of Pt(IV) ions from leaching solutions, removal of Pt(IV) ions from wastewater and preconcentration of Pt(IV) ions prior to the measurement. Activated carbon, silica gel, ion exchangers, impregnated resins, chelating polymers, biomass or natural polymers have been used as adsorbent for SPE of the analytes (Öztürk et al., 2020). Anion exchange and chelating resins are very efficient in the separation and recovery of Pt(IV) ions. Trace levels of Pt(IV) ions can be recovered and separated from other base metal ions by the selective binding properties of these resins (Cyganowski et al. 2020). No requirement to phase separation, no usage of organic solvents and providing a high enrichment factor are the advantages of SPE procedures over liquid-liquid extraction (Öztürk et al., 2020). However, due to the complex chemistry of the platinum element, it makes the separation of Pt(IV) ions difficult by the SPE method, and therefore, scientists have been working extensively in the synthesis and applications of different materials with ion exchange and/or chelating properties in the last two decades (Cyganowski et al. 2020). For this purpose, various adsorbents such as zeolite functionalized with 3-aminopropyl(diethoxy)methylsilane (Mosai et al., 2018), cellulose modified with polyethyleneimine (Hong et al., 2019), poly(m-aminobenzoic acid) chelating polymer (Öztürk et al., 2020), 3-aminopropyl- (diethoxy)methylsilane modified bentonite (Mosai et al., 2020), 1,10-phenanthroline-2,9-dicarbaldehyde cross-linked chitosan, [2,2'-bipyridine]-5,5'- dicarbaldehyde cross-linked chitosan and 8-hydroxyquinoline-2-carbaldehyde-grafted cross-linked chitosan (Mincke et al., 2019) for SPE of Pt(IV) ions have been reported in the literature. Diethylenetriamine bonded silica gel was previously used for preconcentration of Pd(II), Au(III) and Cu(II) ions from aqueous solutions (İmamoğlu et al., 2005). Bis(3-aminopropyl)amine bonded silica gel was synthesized and used for adsorption of Pd(II) (Sivrikaya et al., 2011), selective determination of Cr(VI) (Akyüz et al., 2013) and solid-phase extraction of Cu(II) in water and food samples (Çağırdı et al., 2014). According to our literature survey, adsorption and recovery of Pt(IV) ions have not been studied using diethylenetriamine bonded silica gel and bis(3-aminopropyl)amine bonded silica gel. In this study, diethylenetriamine bonded silica gel (DETA-SG) and bis(3-aminopropyl)amine bonded silica gel (BAPA-SG) were synthesized and used for the recovery of Pt(IV) ions from aqueous solutions. The fabricated adsorbents were characterized by C,H,N elemental analysis and FTIR spectroscopy. SPE of Pt(IV) ions using the modified silica gels was investigated by batch adsorption technique. The hidronium and chloride concentration in the solution, contact time and initial Pt(IV) concentration, which are the factors affecting the adsorption of Pt(IV) ions with BAPA-SG and DETA-SG, were investigated. In column SPE studies, the sample volume and flow rate, the type, volume and concentration of the eluent solution and the effect of matrix ions were investigated. In the batch adsorption studies of Pt(IV) ions, it was found that the adsorption of Pt(IV) ions was most efficient in solutions containing 0,1 M hydronium and 0,1 M chloride, and the amount of adsorbed Pt(IV) increased with increasing initial concentration of Pt(IV) ions. It was also found that the adsorption of Pt(IV) ions reached equilibrium in 2 hours with bis(3-aminopropyl)amine bonded silica gel and 4 hours with diethylenetriamine bonded silica gel, and the Pt(IV) adsorption kinetics were consistent with the pseudo-second-order kinetic model. The adsorption of Pt(IV) ions with bis(3-aminopropyl)amine bonded silica gel and diethylenetriamine bonded silica gel was compatible with the Langmuir isotherm and their maximum adsorption capacities for Pt(IV) ions were 158,7 and 227,3 mg/g, respectively. By the comparison of the Pt(IV) adsorption capacities of the modified silica gels with the adsorbents reported in the literature, it was seen that some adsorbents in the literature have higher Pt(IV) adsorption capacities than the bis(3-aminopropyl)amine bonded silica gel and diethylenetriamine bonded silica gel. But some of them have lower capacities than the modified silica gels. So, it can be concluded that the Pt(IV) adsorption capacity of bis(3-aminopropyl)amine bonded silica gel and diethylenetriamine bonded silica gel have moderate Pt(IV) adsorption capacities. In column solid phase extraction studies, the sample volume and flow rate, the type, volume and concentration of the eluent solution and the effect of matrix ions were investigated. It was found that Pt(IV) ions could be quantitatively recovered from a sample volume of 500 mL by column solid phase extraction technique using both modified silica gels. It was also found that the recovery of Pt(IV) ions using both modified silica gels was decreased by high concentrations of chloride ions. As a result, it was concluded that diethylenetriamine bonded silica gel was more effective for Pt(VI) adsorption, and bis(3-aminopropyl)amine bonded silica gel and diethylenetriamine bonded silica gel could be used for the adsorption and recovery of Pt(IV) ions.
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