Sinteza i karakterizacija nanokompozita srebra i huminskih kiselina

master's thesis

• Title (english): Synthesis and characterization of silver/humic acids nanocomposites
• Author: Mia Zaračko
• Mentor: Tomislav Bolanča (mentor)
• Committee member: Tomislav Bolanča (predsjednik povjerenstva)
• Committee member: Šime Ukić (član povjerenstva)
• Committee member: Petar Kassal (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2017-07-12, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry; Analytic Chemistry

Abstract

Cilj ovog rada je sinteza nanokompozita srebra i huminske kiseline primjenom metode
imobilizacije srebra na modificiranu huminsku kiselinu iz vodene otopine. Određeni su
optimalni uvjeti za sintezu: različito vrijeme kontakta otopine Ag+ iona i huminske kiseline
(kinetika), različite inicijalne pH vrijednosti te inicijalne koncentracije Ag+ iona. Za
istraživanje mehanizma adsorpcije/precipitacije srebra na huminsku kiselinu korišteni su
različiti kinetički modeli kojima su opisani eksperimentalni rezultati: model nultog, prvog,
pseudo prvog i pseudo drugog reda.
Srebrne nanočestice sintetizirane su iz soli srebrova nitrata, AgNO3 u prisutnosti
huminske kiseline koja ima ulogu stabilizatora i reducensa srebra iz ionskog oblika Ag+ u
metalni oblik Ag0 koji odgovara formi nanočestica. Prije sinteze, huminska kiselina prevodi
se u netopljiv oblik termičkom metodom prema Sekiju i Suzukiju[20] čime se olakšava
uklanjanje sintetiziranog nanokompozita od srebra preostalog u vodenoj otopini. Primjenom
plamene atomske apsorpcijske spektrofotometrije provodi se analiza uklanjanja srebra
mjerenjem koncentracije rezidualnog srebra nakon sinteze.
Nemodificirana i modificirana huminska kiselina te sintetizirani nanokompozit
karakterizirani su različitim instrumentalnim metodama: elementarna analiza,
termogravimetrijska analiza, infracrvena spektroskopija s Fourierovom transformacijom,
rendgenska difrakcija te skenirajuća elektronska mikroskopija s EDX detektorom. Konačno,
primjenom disk-difuzijske metode i metode minimalne inhibitorne koncentracije procijenjeno
je antimikrobiološko djelovanje nanokompozita na sedam testiranih bakterija: Staphylococcus
aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella
pneumoniae, Proteus mirabilis i Acinetobacter baumannii.

Abstract (english)

The main aim of this work was preparation (synthesis) of silver and humic acids
nanocomposites by silver immobilization on modified humic acids in aqueous solution. Effect
of various parameters on synthesis was evaluated: contact time between Ag+ and humic acid
(kinetic studies), initial pH value, and concentration of silver ion. Experimental data was
approximated by different kinetic models: zero-order, first-order, pseudo fist-order, and
pseudo second-order.
Silver nanoparticles were synthesized from silver nitrate salt, AgNO3, in presence of
humic acid. Humic acid has role of a stabilizing and reducing agent that converts silver from
ionic Ag+ form into Ag0 one which corresponds to nanoparticle form. Before synthesis, humic
acid was modified into insoluble form using thermal method developed by Seki and Suzuki[20]
in order to simplify the separation of synthesized nanocomposite and residual silver in
aqueous solution. Flame atomic absorption spectrophotometry was applied for analysis of
silver removal: silver concentration after the synthesis (residual silver concentration) was
measured.
Non-modified humic acid, modified humic acid and synthesized nanocomposite were
characterized using different instrumental methods: elemental analysis, thermogravimetric
analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron
microscopy with EDX detector. Finally, well diffusion method and minimal inhibitory
concentration method were used to evaluate antimicrobial activity of nanocomposite against
seven selected bacteria: Staphylococcus aureus, Staphylococcus epidermidis, Escherichia
coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Acinetobacter
baumannii.

• Keywords: nanočestice srebra; huminska kiselina; nanokompozit; kinetički modeli
• Keywords (english): silver nanoparticles; humic acid; nanocomposite; kinetic models
• Language: croatian
• URN:NBN: urn:nbn:hr:149:062126
• Study programme: Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry; Course: Advanced materials and technologies; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra primijenjene kemije (magistar/magistra primijenjene kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-11-11 12:26:07