Title Priprema TiO2/ZIF-8 hibridnog fotokatalizatora i testiranje njegove aktivnosti za fotorazgradnju neonikotinoidnih insekticida Title (english) Preparation of hybrid TiO2/ZIF-8 photocatalyst and testing of its activity for photodegradation of neonicotinoid insecticides Author Lucija Bogdan Mentor Vesna Tomašić (mentor)Committee member Vesna Tomašić (predsjednik povjerenstva)Committee member Marina Duplančić (član povjerenstva)Committee member Ana Palčić (član povjerenstva)Granter University of Zagreb Defense date and country 2022-09-29, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Zbog kontinuiranog porasta koncentracije organskih onečišćenja u vodenim ekosustavima, postoji potreba za pronalaskom tehnologije za učinkovitu obradu industrijskih i komunalnih otpadnih voda. Fotokataliza upotrebom titanijevog dioksida već je dobro uspostavljena metoda razgradnje organskih onečišćivala, no primjena titanijevog dioksida koja je ograničena samo aktivacijom UV zračenjem predstavlja velik izazov. Tijekom opsežnih istraživanja na ovom području razvijene su različite metode dopiranja titanijevog dioksida nemetalima ili drugim fotoaktivnim metalima, kao i ostali postupci modifikacije TiO2 usmjereni na smanjenje zabranjene zone i smanjenje brzine rekombinacije nositelja naboja. Međutim, u novije vrijeme postignuti su značajni iskoraci u području zeolita i metalo-organskih mreža kao naprednih materijala s velikom specifičnom površinom i ujednačenom strukturom što otvara nove mogućnosti pripreme kompozitnih fotokatalizatora i daljnjeg poboljšanja fotokatalitičke aktivnosti postojećih fotokatalizatora čiji je sastavni dio titanijev dioksid. U ovome radu opisan je postupak sinteze hibridnog TiO2/ZIF-8 fotokatalizatora i provedeno je testiranje njegove aktivnosti u sustavu za fotokatalitičku razgradnju neonikotinoidnog insekticida imidakloprida u uvjetima UV zračenja postignutog uporabom Pen Ray lampe. Hibridni fotokatalizatori dobiveni su hidrotermalnom sintezom pri 150 ºC uporabom mehanokemijski sintetiziranog ZIF-8 i titanijevog tetraizopropoksida kao prekursora titanijevog dioksida. Sintetizirana su tri fotokatalizatora s različitim udjelima titanijevog dioksida (5, 50 i 95 %) te su provedena istraživanja njihovih adsorpcijskih i fotokatalitičkih svojstava. Istraživanja su provedena u suspenzijskom reaktoru volumena 80 mL, s 80 mg uzorka katalizatora pri brzini okretaja od 250 o/min. Početna koncentracija imidakloprida iznosila je 10 ppm, a pH je podešen na 6,5. Stupanj razgradnje imidakloprida određen je mjerenjem koncentracije imidakloprida u vremenskim intervalima od 15, 30 i 60 minuta primjenom tekućinske kromatografije visoke djelotvornosti. Rezultati karakterizacije pokazali su uspješnu sintezu hibridnog fotokatalizatora uz smanjenje energijskog procjepa s 5,0 eV na 3,1 – 3,6 eV u odnosu na polazni uzorak (ZIF-8). Fotokatalizatori su se pokazali termički stabilnima do 400 ºC s veličinom čestica ispod 1 μm. Ustanovljeno je da ne dolazi do promjene strukture katalizatora nakon njegovog testiranja u sustavu. Usprkos izvrsnoj adsorpcijskoj sposobnosti ZIF-8 kao temeljne komponente hibridnih fotokatalizatora, hibridni fotokatalizatori pokazali su loša adsorpcijska svojstva. Uspješnost fotorazgradnje imidakloprida ovisi o masenom udjelu fotokatalitički aktivne komponente, TiO2, nanesene na površinu ZIF-8. Najveću učinkovitost pokazivao je hibridni fotokatalizator koji je sadržavao 5 % TiO2.
Abstract (english) Due to the continuos increase in the concentration of organic pollutants in water ecosystems, there is need to find technology for efficient tretment of industrial and municipal wastewater. Photocatalysis using titanium dioxide is already a well-established method of decomposition of organic pollutants, but the limited use of titanium dioxide only with activation by UV radiation presents a big challenge. During extensive research in this area, various methods of doping titanium dioxide with nonmetals or other photoactive metals were developed, as well as other TiO2 modification procedures aimed at reducing the band gap and reducing the rate of charged carrier recombination. However, in recent times, significant advances have been made in the field of zeolites and metal-organic frameworks as advanced materials with a large specific surface area and uniform structure, which opens up new possibilities for the preparation of composite photocatalysts and further improvement of the photocatalytic activity of existing photocatalysts whose constituent part is titanium dioxide. This paper describes the synthesis procedure of the hybrid TiO2/ZIF-8 photocatalyst and testing of its activity in a system for the photocatalytic degradation of the neonicotinoid insecticide imidacloprid under the conditions of UV irradiation achieved using a Pen Ray lamp. Hybrid photocatalysts were obained by hydrothermal synthesis at 150 ℃, using mechanochemically synthesized ZIF-8 and titanium tetraisopropoxide as precursor to titanium dioxide. Three photocatalysts with different amount of titanium dioxide (5, 50 and 95%) were synthesized and their adsorption and photocatalytic properties were investigated. The research was carried out in a suspension reactor with a volume of 80 mL, containing 80 mg of the catalyst sample at a rotation speed of 250 rpm. The initial concentration of imidacloprid was 10 ppm, and the pH was adjusted to 6,5. The degree of degradation of imidacloprid was determined by measuring the concentration of imidacloprid in time intervals of 15, 30 and 60 minutes using high performance chromatography. The characterization results showed successful synthesis of the hybrid photocatalyst with a reduction of the band gap from 5,0 eV to 3,1 – 3,6 eV compared to the starting sample (ZIF-8). The photocatalysts proved to be thermally stable up to 400 ℃ with a particle size below 1 μm. It was found that there is no change in the structure of the catalyst after its testing in the system. Despite the excellent adsorption capacity of ZIF-8 as the basic component of the hybrid photocatalysts, the hybrid photocatalysts showed poor adsorption properties. The efficiencyof the photodegradation of imidacloprid depends on the mass fraction of the photocatalytically active component, TiO2, deposited on the surface of ZIF-8. The hybrid photocatalyst containing 5% of TiO2 showed the highest efficiency.
Keywords
TiO2
ZIF-8
heterogena fotokataliza
imidakloprid
Keywords (english)
TiO2
ZIF-8
heterogenous photocatalysis
imidacloprid
Language croatian URN:NBN urn:nbn:hr:149:108788 Project Number: IP-2018-01-8669 Study programme Title: Chemical Engineering - Graduate study Type of resource Text File origin Born digital Access conditions Access restricted to students and staff of home institution Terms of use Created on 2023-03-29 09:14:48
