Naslov (srp)

Sinteza, karakterizacija i primena hidrogelova za izdvajanje bakra, kadmijuma i cinka iz vodenih rastvora : Doktorska disertacija

Autor

Milosavljević, Nedeljko B.

Doprinosi

Kalagasidis Krušić, Melina
Perić-Grujić, Aleksandra
Filipović, Jovanka

Opis (srp)

U radu su polikondenzacijom sintetisane semi-interpenetrirajuće mreže (semi-IPM) na bazi hitozana i itakonske kiseline, a kao interpenetranti su korišćeni poli(etilen glikol) i poli(N-vinil-2-pirolidon). Polikondenzacijom su sintetisane i hibridne polimerne mreže hitozana (HPM), itakonske kiseline i poli(vinil alkohola), dok su hidrogelovi hitozana, itakonske i metakrilne kiseline (Ch/IA/MAA) sintetisani radikalnom polimerizacijom. Sinteza svih sistema je izvedena uz variranje odnosa monomera i koncentracije umreživača. Ispitan je uticaj reakcionih parametara na parametre mreže i stepen bubrenja dobijenih hidrogelova. Karakterizacija dobijenih uzoraka izvedena je ispitivanjem kinetike bubrenja u puferima različitih pH vrednosti, infracrvenom spektroskopijom sa Furieovim transformacijama (FT-IR), rendgenskom analizom (XRD), dinamičko-mehaničkom analizom (DMA), skenirajućom elektronskom mikroskopijom (SEM), energetskom disperzionom spektroskopijom (EDX), mikroskopijom atomskih sila (AFM), termogravimetrijskom analizom (TGA) i diferencijalnom skenirajućom kalorimetrijom (DSC). Sistem koji je u prethodnim ispitivanjima imao najbolje karakteristike, hidrogelova Ch/IA/MAA, primenjen je za uklanjanje teških metala (Cu+2, Cd+2 i Zn+2) iz vodenih rastvora. Praćena je kinetika sorpcije metala i ispitan uticaj pH sredine, mase sorbenta, temperature i početne koncentracije metala na stepen uklanjanja. Koncentracija metala, pre i nakon sorpcije, je merena indukovanom spregnutom plazmom sa masenom detekcijom (ICP-MS). Ispitana su tri najčešće upotrebljavana modela adsorpcionih izotermi: Lengmuir-ova, Freundlich-ova i Redlich-Peterson-ova. Na kraju je ispitana desorpcija metala sa sorbenta odgovarajućim reagensima, uz optimizaciju njihove koncentracije. Rezultati ispitivanja su pokazali da bubrenje sintetisanih hidrogelova zavisi od sastava, pH vrednosti rastvora, temperature i koncentracije umreživača. Sastav hidrogelova i koncentracija umreživača utiču na mehanička svojstva, a u slučaju semi-IPM i HPM vrsta i sadržaj dodatog polimera. SEM analiza je pokazala da svi hidrogelovi imaju poroznu strukturu, kao i da nakon vezivanja metala dolazi do smanjenja pora u hidrogelu. FT-IR analizom je utvrđeno jonsko umrežavanje između COO– grupa iz kiseline i grupa iz hitozana, kao i hemijsko umreženje između hitozana i poli(vinil alkohola).Takođe, FT-IR analiza je pokazala da se metal veže najverovatnije preko –NH2 i –OH grupa hitozana i karboksilnih grupa koje potiču iz ugrađenih kiselina. Kapacitet sorpcije zavisi od pH sredine, mase sorbenta, početne koncentracije metala u rastvoru i temperature. Mehanizam sorpcije Cd2+, Cu2+ i Zn2+ se pretežno odvija preko pseudo-drugog reda, a najbolji rezultati su dobijeni za Redlich–Peterson-ov model. Vrednosti energije aktivacije ukazuju da je u pitanju fizisorpcija. Sva tri metala se desorbuju 100 % sa 0,01 mol/L HNO3 i 0,1 mol/L HNO3. Tokom tri uzastopna procesa adsorpcije/desorpcije za sva tri metala je zadržana efikasnost desorpcije od 100,0 %. Prikazani rezultati pokazuju da su Ch/IA/MAA hidrogelovi vrlo pogodni kao sorbenti za uklanjanje Cu2+, Cd2+ i Zn2+ iz vodenih rastvora, jer imaju zadovoljavajući kapacitet sorpcije, a mogu se više puta upotrebljavati uz potpunu regeneraciju što je veoma važno za praktičnu primenu.

Opis (srp)

Hemija i hemijska tehnologija - polimerno inženjerstvo / Chemistry and chemical technology - polymeric engineering Datum odbrane: 17.12.2010.

Opis (eng)

The present work reports on the properties of semi-interpenetrating networks (semi-IPN) based on chitosan and itaconic acid with poly(ethylene glycol) and poly(N-vinyl-2-pyrolidone) and hybrid polymer network (HPN) based on chitosan, itaconic acid and poly(vinyl alcohol) synthesized by polycondesation reaction, as well as the hydrogels of chitosan, itaconic and methacrylic acid (Ch/IA/MAA) synthesized by radical polymerization. All hydrogels were synthesized with varying monomer content and crosslinking agent concentration. The swelling kinetics was carried out in buffers of different pHs. Further, the samples were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic-mechanical analysis (DMA), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The best system, determined by previous studies, Ch/IA/MAA hydrogels, was applied as a sorbent for removal of heavy metals (Cu+2, Cd+2 and Zn+2) from aqueous solutions. The kinetics of metals adsorption was investigated, as well as the influence of pH, adsorbent dosage, temperature and concentration of metals on the degree of heavy metal removal. Also, the three most commonly used models of adsorption isotherms: Langmuir, Freundlich and Redlih-Peterson were applied. Afterwards, desorption of metals from sorbent were tested with appropriate reagents, with optimization of their concentration. The results showed that the swelling of the synthesized hydrogels depend on the hydrogel composition, pH, temperature and degree of the crosslinking. The hydrogel composition and the degree of crosslinking affect the mechanical properties, as well as the type and content of the added polymer in the case of semi-IPN and HPN. SEM analysis showed that all hydrogels had a porous structure. Sorption of the metal ions led to reduction of the hydrogel pore size. FT-IR analysis showed the ionic crosslinking between the COO-group of the acid and NH3+ groups of chitosan and chemical crosslinking between chitosan and poly(vinyl alcohol). Further, FT-IR analysis also showed that the metal is very likely bounded over –NH2 and –OH groups of chitosan and carboxyl groups originating from the incorporated acids. It was found that the adsorption capacity depend on the pH of solution, the adsorbent mass, initial solution metal concentration and temperature. The mechanism of Cd2+, Cu2+ and Zn2+ adsorption predominantly followed the pseudo-second order kinetics, while the best results were obtained for the Redlich-Peterson's model. Based on the adsorption activation energy the adsorption process is considered as a physisorption. Both HNO3 solutions, 0.1 mol/L and 0.01 mol/L, appeared to be effective for metal ions desorption (100.0 %). No significant loss of the capacity was observed during three cycles of adsorption-desorption. According to the presented results, Ch/IA/MAA hydrogels could be used as sorbents for the removal of heavy metals (Cu+2, Cd+2 and Zn+2) from aqueous solutions due to their high adsorption capacity and the possibility of reuse, on account of complete recovery, which is very important for the practical application.

Jezik

srpski

Datum

2010

Licenca

Ovo delo je licencirano pod uslovima licence
Creative Commons CC BY-NC-ND 2.0 AT - Creative Commons Autorstvo - Nekomercijalno - Bez prerada 2.0 Austria License.

http://creativecommons.org/licenses/by-nc-nd/2.0/at/legalcode