Sinteza in karakterizacija cink-železovih plastovitih dvojnih hidroksidov

Golob, David (author), Cerc Korošec, Romana (mentor)

Plastoviti dvojni hidroksidi (angl. Layered Double Hydroxides – LDH) so anionske gline z značilno plastovito strukturo. Naboj LDH plasti je pozitiven, zato se med plasti interkalirajo različne anionske zvrsti, da pride do izenačitve naboja. Med plastmi se nahajajo tudi vodne molekule. Dvo- in trivalentni kovinski kationi, ki gradijo plasti LDH, so lahko različnih vrst, kar nam omogoča širok nabor različnih LDH. Zaradi svojih številnih uporabnih lastnosti, kot so npr. velika specifična površina, visoka poroznost in enostavna priprava, so uporabljeni na številnih področjih. Z zamenjavo anionov, ki se vgradijo med plasti, lahko LDH spreminjamo lastnosti in jih tako uporabimo za različne aplikacije. Namen mojega diplomskega dela je bila sinteza in karakterizacija cink-železovih plastovitih dvojnih hidroksidov. Produkte smo analizirali z rentgensko praškovno difrakcijo (XRD), infrardečo spektroskopijo (IR), termogravimetrijo (TG), dušikovo fizisorpcijo in vrstičnim elektronskim mikroskopom (SEM). Sinteze so potekale po metodi soobarjanja pri konstantnem pH. Raztopino prekurzorskih kationov (Zn$^{2+}$, Fe$^{3+}$) sem pripravil z upoštevanjem pogoja, da mora biti delež trivalentnega kationa med 0,2 in 0,33. Produktom smo merili absorpcijske in fotokatalitske sposobnosti na osnovi merjenja spreminjanja koncentracije barvila Plasmocorinth B, ki je bil v stiku z materialom. Raztopini barvila smo merili absorbanco z uporabo UV-Vis spektrometra, preko katere smo izračunali koncentracijo. Zanimalo nas je tudi, kako dobro materiali adsorbirajo svinec iz odpadnih voda, zato smo naredili meritve, pri katerih smo imeli raztopino z začetno koncentracijo Pb$^{2+}$ ionov, ki smo ji dodali vzorec in pomerili koncentracijo po adsorpciji Pb$^{2+}$ ionov. Meritve smo izvajali z metodo optične emisijske spektrometrije. Izkazalo se je, da smo sintetizirali FeO(OH), vendar iz analize SEM sklepamo, da je poleg FeO(OH) nastalo tudi nekaj slabo kristaliničnega želenega produkta. Poleg tega so tudi ostale opravljene analize pokazale, da je imel sintetiziran produkt določene lastnosti LDH.

• Language: Slovenian
• Keywords: plastoviti dvojni hidroksidi, metoda soobarjanja, SEM, adsorpcija, fotokataliza
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-159052
• COBISS.SI-ID: 202658819
• Publication date in RUL: 28.06.2024

Secondary language

• Language: English
• Title: Synthesis and characterisation of zinc-iron layered double hydroxides

Abstract

Layered double hydroxides (LDHs) are anionic clays with a characteristic layered structure. The charge of LDH layers is positive, so different anionic species are intercalated between the layers to equalize the charge. Water molecules are also located between the slabs. Divalent and trivalent metal cations that form LDHs can be of different types, giving us a wide range of LDHs that can be synthesized. LDHs are used in many applications due to their many useful properties, such as high specific surface area, high porosity and easy preparation. By exchanging the anions between the layers, LDHs can be modified in their properties and thus used for a variety of applications. The aim of my diploma work was the synthesis and characterisation of zinc-iron layered double hydroxides. The products were analysed using X-Ray powder diffraction (XRD), infrared spectroscopy (IR), thermogravimetry (TG), nitrogen physisorption and scanning electron microscopy (SEM). The syntheses were carried out by the co-precipitation method at constant pH. The solution of the precursor cations (Zn$^{2+}$, Fe$^{3+}$) was prepared under the condition, that the molar ratio of the trivalent metal cation was between 0.2 and 0.33. The absorption and photocatalytic properties of our products were determined by measuring the change in concentration of the dye Plasmocorinth B in contact with the material. The absorbance of the dye solution was measured by using UV-Vis spectrometer, from which the dye concentration was calculated. We also wanted to know how well the product adsorbs lead from the waste water. We have prepared a solution with an initial concentration of Pb$^{2+}$ ions, added our sample and measured the concentration of Pb$^{2+}$ ions after they adsorbed on the material. The measurements were carried out by optical emission spectrometry. It turned out that FeO(OH) was synthesised, but on the basis of SEM analysis we suppose that some poorly crystalline desired product was also formed. In addition, other analyses carried out showed that the synthesised product had certain LDH properties.

• Keywords: layered double hydroxides, co-precipitation method, SEM, adsorption, photocatalysis