Biosorption of heavy metal ions from water by sugar beet shreds

Abstract

Cilj ove doktorske disertacije je bio da se ispita mogućnost primene izluţenih rezanaca šećerne repe i njihovih tretiranih oblika, nastalih u procesu proizvodnje bioetanola, kao biosorbenata za uklanjanje jona teških metala iz vode. U okviru eksperimenata, u laboratorijskim uslovima izvedeni su predtretman i hidroliza izluženih rezanaca kako bi se dobili tretirani oblici, a zatim je izvršena karakterizacija adsorbenata, ispitane njihove adsorpcione sposobnosti, utvrđeni najbolji uslovi za njihovu primenu i ispitana mogućnost njihove višestruke primene u obradi vode.<br />U okviru karakterizacije materijala određen je njihov sastav, specifiĉna površina i poroznost, ispitana površina primenom FTIR i EDS metode i kvantifikovana količina pojedinih funkcionalnih grupa prisutnih na površini primenom Boehm-ove titracije. Na osnovu FTIR metode pre i posle adsoprcije utvrđeno je koje grupe učestvuju u vezivanju jona metala.<br />Ispitan je i uticaj razliĉitih parametara na adsorpciju (vreme kontakta adsorbenta i adsorbata, veličina čestice, pH, temperatura, primenjena doza adsorbenta, jonska jačina, sušenje) radi utvrđivanja najboljih uslova za maksimalnu efikasnost.<br />Kako bi se stekao bolji uvid u sam proces adsorpcije jona na površinu adsorbenata, na eksperimentalne podatke primenjeni su različiti modeli adsorpcionih izotermi, a mehanizam vezivanja je detaljnije razmotren primenom kinetiĉkih modela. Primenom termodinamičkih modela utvrđena je priroda procesa.<br />Radi višestruke primene ovih ekoloških biosorbenata ispitana je i mogućnost regeneracije materijala razliĉitim kiselinama kao desorbensima i utvrđeno optimalno vreme desorpcije. Ispitana je primena kroz više uzastopnih ciklusa adsorpcija – desropcija. Rezultati su pokazali da ispitani materijali imaju zadovoljavajući adsorpcioni kapacitet, ali da se mogu primenjivati i vlažni, odmah nakon procesa ekstrakcije šećera, depektinacije i hidrolize, bez utroška energije za sušenje. Pored toga, utvrđeno je da se mogu regenerisati i koristiti uspešno više puta, što otvara mogućnost za njihovu primenu u praksi.

The aim of this PhD thesis was to investigate the possibility of usage of sugar beet shreds and their treated forms from the bioethanol production for removal of heavy metal ions from water. In the context of experiments, pretreatment and hydrolysis of sugar beet shreds were performed in order to obtain treated forms. The characterization of biosorbents was conducted and their adsorption capacity was investigated. Also, the optimal conditions for their implementation and the possibility of their multiple applications for water treatment were determined.<br />Within the characterization of materials their composition, specific surface area and porosity were determined. The surface of biosorbents was investigated by using FTIR and EDS methods. The amount of the functional groups present on the surface was quantified by Boehm's titration. On the basis of the FTIR method before and after adsorption it was determined which functional groups participate in the binding process.<br />The influence of various parameters on the adsorption (contact time of the adsorbent and adsorbate, particle size, pH, temperature, adsorbent dose, ionic strength, drying process) were examined in order to determine the best conditions for maximum efficiency.<br />For better insight into the process of adsorption of ions on the surface of the adsorbents, different models of adsorption isotherms were applied to experimental data. Mechanism of adsorption was determined by applying different kinetic models. The nature of the process was investigated by determining thermodynamic parameters.<br />The multiple applications of these eco-friendly biosorbents was examined by regeneration investigation. The optimal time of desorption was determined and different acids were used for regeneration study. The multiple cycles adsorption – desorption was also conducted.<br />The results showed that the investigated materials have a satisfactory adsorption capacity. They can also be applied wet, immediately after the process of sugar extraction, depectination and hydrolysis, without the energy consumption for drying. In addition, it was found that they can be regenerated and successfully used several times. This opens up the possibility for their practical application.