Površinska modifikacija i funkcionalizacija prirodnoga zeolita – klinoptilolita

[B. Kalebić]

113 listova

Technological Engineering - Environmental Engineering / Tehnološko inženjerstvo - Inženjerstvo zaštite životne sredine

The goal of the dissertation was to develop new, environmentally friendly, and economically profitable adsorbents based on natural zeolite – clinoptilolite (CLI) for the removal of the antibiotic ciprofloxacin (CIP) from aqueous solutions. CLI was chosen as it is readily available, while CIP as it is a widely used fluoroquinolone-type antibiotic. In this study, the CLI is first modified with iron oxide nanoparticles (MAG) by two methods: 1) co-precipitation (MAGCP-CLI) from a Fe(II) salt solution and 2) microwave crystallization also from Fe(II) solution (MAGMW-CLI). Finally, the third modification procedure involved the deposition of graphene oxide on MAGMW-CLI using ultrasonic treatment (GO-MAGMW-CLI). The CIP adsorption on the obtained adsorbents was investigated for different initial CIP concentrations, temperatures, pH values and reaction times. The design of experiment (DoE) was used to analyse the influence of these parameters on the adsorption efficiency. Using the response surface methodology and the application of the central composite design (RSM-CCF), the following was determined: the highest possible adsorbed CIP concentration (12.40 mg g–1) is achieved onto GO-MAGMW-CLI for an initial concentration of 48.47 mg dm–3 at pH = 5 and 24.78 °C, after 19.20 min. Adsorption kinetics and mechanism were investigated by applying the most commonly used kinetic and adsorption isotherms models at 10, 15 and 20 °C and pH = 5. For all investigated temperatures, the adsorption kinetics follows the pseudo-second-order Lagergren equation, while the mechanism of the adsorption process is best described by the Langmuir isotherm. The adsorption mechanism of CIP for the investigated adsorbents includes ion exchange reaction and electrostatic attraction between the negatively charged aluminosilicate lattice of the adsorbent and CIP-cations. Modification of CLI with mixed iron oxides (12 wt.%) conferred magnetic properties to the adsorbents, enabling their separation from the liquid phase by an external magnetic field. Also, the presence of graphene oxide on the surface contributed to an increase in the specific surface area and adsorption capacity. For the adsorbents’ regeneration, a novel method of non-thermal plasma (NTP) was applied. In this work, NTP was tested for the first time to remove organic species from the surface of minerals. Various reactive gas species formed during NTP treatment contributed to the mineralization of adsorbed CIP. The results showed that in five consecutive adsorption/regeneration cycles, more than 90% of the adsorption capacity was preserved.

Cilj ove doktorske disertacije bio je razvoj novog, ekološki prihvatljivog i ekonomski isplativog adsorbensa na bazi prirodnog zeolita – klinoptilolita (CLI) za uklanjanje antibiotika ciprofloksacina (CIP) iz vodenih rastvora. Za modifikaciju je izabran CLI kao jedan od najdostupnijih prirodnih zeolita, dok je CIP izabran kao široko upotrebljivan antibiotik iz grupe fluorohinolona. U radu, CLI je modifikovan na tri načina. Prvo, nanočesticama gvožđe-oksida (MAG) primenom dve metode: 1) ko-precipitacijom (MAGCP-CLI) iz rastvora Fe(II)-soli i 2) mikrotalasnom kristalizacijom takođe iz Fe(II)-rastvora (MAGMW-CLI). Treći postupak modifikacije podrazumevao je nanošenje grafen-oksida na MAGMW-CLI pomoću ultrazvučnog tretmana (GO-MAGMW-CLI). Adsorpcija CIP-a na dobijene adsorbense ispitana je za različite početne koncentracije, temperature, vrednosti pH i reakciona vremena. Za anlizu uticaja ovih parametara na efikasnost adsorpcije korišćena je metoda za dizajn eksperimenta (DoE). Metodom odzivnih površina i primenom centralnog kompozitnog dizajna (RSM-CCF) određeno je sledeće: najveća moguća koncentracija CIP-a od 12.40 mg g–1 postignuta je na GO- MAGMW-CLI za početnu koncentraciju 48,47 mg dm–3 pri pH = 5 i 24,78 °C, nakon 19,20 minuta. Kinetika i mehanizam adsorpcije ispitivane su pomoću najčešće korišćenih kinetičkih modela i adsorpcionih izotermi na 10, 15 i 20 °C i pH = 5. Za sve ispitivane temperature, kinetika adsorpcije sledi Lagergrenovu jednačinu pseudo-drugog reda, dok se mehanizam procesa adsorpcije najbolje opisuje Langmuirovom izotermom. Zaključeno je da mehanizam adsorpcije CIP-a za ispitivane adsorbense uključuje dva procesa: reakciju jonske zamene i elektrostatičko privlačenje između negativno naelektrisane aluminosilikatne rešetke adsorbensa i CIP-katjona. Modifikacija CLI-a mešovitim oksidima gvožđa (12 mas.%) doprinela je da adsorbensi dobiju magnetna svojstva i da se pomoću spoljašnjeg magnetnog polja lako mogu odvojiti od tečne faze. Takođe, prisustvo grafen-oksida na površini doprinelo je povećanju specifične površine i adsorpcionog kapaciteta. Za regeneraciju adsorbenasa primenjena je nova metoda netermalne plazme (NTP) koja je prvi put ispitana u ovom radu za uklanjanje organskih vrsta sa površine minerala. U NTP tretmanu došlo je do stvaranja različitih reaktivnih gasnih vrsta koje su doprinele mineralizaciji adsorbovanog CIP-a. Rezultati su pokazali da u pet uzastopnih ciklusa adsorpcije/regeneracije, ostaje očuvano više od 90% adsorpcionog kapaciteta

natural zeolite, clinoptilolite, magnetic nanoparticles, graphene oxide, ciprofloxacin, adsorbent regeneration, non-thermal plasma

prirodni zeolit, klinoptilolit, magnetne nanočestice, grafen-oksid, ciprofloksacin, regeneracija adsorbensa, netermalna plazma

661.18:549.67(043.3)

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