Karakterizacija i primena kompleksa na bazi hitozana i amidovanog pektina za uklanjanje azo boja iz vodenih rastvora

Abstract

Poslednjih godina se sve veća pažnja posvećuje očuvanju životne sredine. Ispuštanje azo boja u vodenu sredinu dovodi do kontaminacije vode i predstavlja ozbiljan ekološki problem. Azo boje podložne su bioakumulaciji, a zbog kancerogenih, mutagenih i teratogenih svojstava neretko su pretnja zdravlju ljudi i očuvanju okoline. Proces adsorpcije je sve zastupljeniji u obradi svih vrsta otpadnih voda, pa tako i onih koje sadrže azo boje, zbog ekonomičnosti, jednostavnosti procesa i stepena efikasnosti prečišćavanja otpadnih voda. S obzirom da se sve veća pažnja poklanja ispitivanju adsorbenata koji potiču iz obnovljivih izvora i koji su biodegradabilni, zbog ekoloških i ekonomskih uslova, predmet ovog rada je priprema i karakterizacija kompleksa koji se zasnivaju na prirodnim polisaharidima, pektinu i hitozanu. U ovom radu ispitivani su kompleksi hitozan/poli(itakonska kiselina) i amidovani pektin/poli(itakonska kiselina) pri udelima poli(itakonske kiseline) od 10-90% u kompleksu. Takodje, ispitivani su i kompleksi hitozan/montmorilonit i amidovani pektin/montmorilonit, pri udelu montmorilonita od 10-50%. Ovi kompleksi su karakterisani Elementarnom analizom, Fourier transformisanom infracrvenom spektroskopijom (FTIR), Skenirajućom elektronskom spektroskopijom (SEM) i Termogravimetrijom (TG). Analizom FTIR spektara je potvrdjen sastav svih kompleksa. SEM analizom je utvrdjena morfologija ovih kompleksa, kao i promene nastale na površini uzoraka nakon adsorpcije boje. Analizom termograma ustanovljeno je da montmorilonit ima veliki uticaj na termijsku stabilnost kompleksa hitozan/montmorilonit i amidovani pektin/montmorilonit. Montmorilonit pri malom udelu u kompleksu, dovodi do povećane termijske stabilnosti, naspram čistog hitozana, odnosno amidovanog pektina, dok sa porastom montmorilonita do 50% u kompleksu, dolazi do opadanja termijske stabilnosti. Poli(itakonska kiselina) takodje pospešuje termijsku stabilnost kompleksa naspram čistih komponenti. U ovom radu je ispitana kinetika adsorpcije anjonske Reactive Orange 16 boje iz vodenih rastvora na komplekse hitozan/poli(itakonska kiselina) i hitozan/montmorilonit, pri različitim odnosima komponenti u kompleksu. Takodje, ispitivana je i kinetika adsorpcije katjonske Basic Yellow 28 boje iz vodenih rastvora na komplekse amidovani pektin/poli(itakonska kiselina) i amidovani pektin/montmorilonit pri različitim odnosima komponenti. Ispitivan je uticaj početne koncentracije boje (30, 50 i 80 ppm), zatim uticaj temperature (8, 25, 37 i 55 °C), uticaj pH vrednosti rastvora (2, 4, 5, 6 i 7,4) , kao i uticaj različitog odnosa komponenti u kompleksu na kinetiku adsorpcije i adsorpcioni kapacitet. Radi utvrdjivanja kinetike i 2 mehanizma adsorpcije, ispitivana su četiri različita kinetiča modela: Lagergren-ov model pseudo-prvog reda, Ho-ov model pseudo-drugog reda, Jelovičev model i model unutarčestične difuzije. Ispitivana su tri modela adsorpcionih izotermi: Langmuir-ova, Freundlich-ova i Temkin-ova adsorpciona izoterma...

Environmental protection has been a topic of great attention in recent years. Discharging azo dyes in aquatic systems leads to contamination of water and exhibits serious ecological problems. Azo dyes are subject to bioaccumulation, and due to their allergenic, cancerogenic, mutagenic and teratogenic properties they are a grave threat to people and the environment. Adsorption process is becoming incerasingly popular as a way of treatment of various kinds of wastewaters, among them the azo-dyes containing ones, because it is economically feasible, processes are simple and there is a high level of efficiency present in such processes. The increasingly interesting adsorbents are those that stem from sustainable sources and are biodegradable – both from ecological and economical point of view. The aim of this study is preparation and characterization of polymer complexes based on naturally occuring polysaccharides – pectin and chitosan. This study presents the preparation and characterization of chitosan/poly(itaconic acid) and amidated pectin/poly(itaconic acid) complexes containing between 10 and 90% of poly(itaconic acid). The complexes chitosan/montmorillonite and amidated pectin/montmorillonite having between 10 and 50% of montmorillonite were prepared as well. The complexes were characterized by elemental analisys, Fourier Transformed Infrared spectroscopy, Scanning electron microscopy and thermogravimetry. FTIR analysis confirmed the composition of all complexes. SEM analysis confirmed the morphology of these complexes, and changes in morfology after dye adsorption. It was shown that after adsorption on the surface of complexes has changed, and a large number of agglomerate and roughness appeared. Thermogravimetry has shown that the amount of montmorilonite in chitosan/montmorillonite and amidated pectin/montmorillonite complexes had big influence on thermal stability. Montmorillonite increased thermal stability of complexes, but this effect was most pronounced at low amounts of MMT in the system, while at higher content of MMT the decomposition temperature decreased. Poly(itaconic acid) improved the thermal stability of complexes. This study investigated the adsorption kinetics of Reactive Orange 16 dye from aqueous solutions on chitosan/poly(itaconic acid) and chitosan/montmorillonite complexes using various component amounts. The adsorption kinetics of Basic Yellow 28 azo-dye from aqueous solutions on amidated pectin/poly(itaconic acid) and amidated 4 pectin/montmorillonite complexes in various component amounts have also been studied. The influence of initial dye concentration (30, 50 and 80 ppm), temperature (8, 25, 37 and 55˚C), pH value of the solution (2, 4, 5, 6 and 7,4) and the composition of complexes on the kinetics and adsorption mechanisms were the main focus of this work. The kinetics and adsorption mechanisms were investigated using four kinetic models: The Lagergren pseudofirst order model, the Ho pseudo-second order model, the Elovich model and the intraparticular diffusion model. Three adsorption isotherms models were applied – Langmuir, Freundlich and Temkin. Before the experimental part the theoretical introduction has been presented containing the relevant information needed to asses the width of the problem and understanding the prniciples on which this study was based...