Laponitni hidrogeli za adsorpcijo snovi

Kučič, Neli (author), Šebenik, Urška (mentor)

Diplomska naloga obravnava adsorpcijo barvil, govejega serumskega albumina (BSA) in težkih kovin na različno pripravljene laponitne hidrogele. Adsorpcija je proces, pri katerem se snovi, imenovane adsorbati, vežejo na površino snovi, imenovane adsorbenti. Adsorpcija barvil se je preučevala na laponitnih kapsulah, polivinil alkohol (PVA) laponitnem hidrogelu in polidopamin (PDA) laponitnem hidrogelu. Uporabljena barvila so bila kristalvijolično barvilo, metilensko modrilo in rodamin B, ki so kationska barvila, ter metil modro, kongo rdeče barvilo in metiloranž, ki so anionska barvila. Ugotovljeno je bilo, da se pri vseh treh hidrogelih na njihovo površino lažje adsorbirajo kationska kot anionska barvila. Takšna adsorpcija je predvsem posledica privlaka med pozitivno nabitimi molekulami barvil in trajnim negativnim nabojem na površini laponita. Adsorpcijo BSA proteina se je raziskovalo na hidrogelu iz hitozana, polivinil alkohola in laponita ter na hidrogelu iz polivinil alkohola, natrijevega alginata in laponita. Dokazano je bilo, da laponit zaradi svoje posebne strukture izboljša adsorpcijske lastnosti hidrogelom. Za adsorpcijo ionov težkih kovin je bil preučen polivinilpirolidon (PVP) laponitni hidrogel. Pri tem je dodatek laponita omogočil oblikovanje hidrogela. Ioni težkih kovin imajo pozitivni naboj in so se z lahkoto adsorbirali na negativna aktivna mesta na površini laponita. Pri vseh laponitnih hidrogelih poteka adsorpcija psevdo-drugega reda in s tem kemisorpcija. Mehanizem adsorpcije pri hidrogelih, kjer adsorpcija poteka le na površini laponita (laponitne kapsule, PVP laponitni hidrogel) sledi Freundlichovi izotermi, zato gre za heterogeno adsorpcijo. V primerih, kjer se adsorbati vežejo tudi s šibkimi Van der Waalsovimi vezmi na hitozan ali polivinil alkohol, mehanizem sledi Langmuirjevi izotermi in poteka monoslojna adsorpcija. Vse hidrogele je možno tudi regenerirati, kar jim daje dobro prednost za uporabo v različnih panogah.

• Language: Slovenian
• Keywords: hidrogeli, laponit, adsorpcija
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-128207
• COBISS.SI-ID: 71009027
• Publication date in RUL: 06.07.2021

Secondary language

• Language: English
• Title: Laponite hydrogels for adsorption of different substances

Abstract

Thesis describes in detail adsorption of dyes, bovine serum albumin (BSA) and heavy metals onto prepared surfaces of laponite hydrogels. Adsorption is a process in which adsorbates bind onto the surface of adsorbents. Laponite capsules alongside polyvinyl alcohol – laponite hydrogel and hydrogel made from polydopamine and laponite were used for studying adsorption of dyes. Colorants used in the study were crystal violet, methylene blue and rhodamine B which are all cationic colorants and anionic dyes such as methyl blue, congo red and methyl orange. Results of the researches conducted showed that cationic colorants are more easily adsorbed onto the three hydrogels than anionic colorants. The described adsorption is a direct consequence of attraction between positively charged dye molecules and perpetual negative charge on the surface of the laponite. BSA protein adsorption was studied on hydrogel made from chitosan, polyvinyl alcohol and laponite and also on the hydrogel made from polyvinyl alcohol, sodium alginate and laponite. Researches show that laponite improves adsorption properties of hydrogels because of its special structure. For the purposes of heavy metal ions adsorption hydrogel made from polyvinylpyrrolidone and laponite was studied. The addition of laponite during the synthesis enabled the forming of hydrogel. Heavy metal ions have a positive charge and were easily adsorbed onto the negative centers on the surface of the laponite. Kinetics of the adsorption on all studied hydrogels are of the pseudo-second order which means that the type of adsorption is chemisorption. If adsorption takes place only on the surface of the laponite (lap capsules and polyvinylpyrrolidone-laponite hydrogel) the adsorption mechanism follows Freundlich isotherm which means that we have a heterogeneous adsorption. In cases where adsorbates also bind onto the chitosan or polyvinyl alcohol with weak Van der Waals bonds the adsorption mechanism follows the Langmuir isotherm and we have a monolayer adsorption. All of the abovementioned hydrogels have the ability to be regenerated which gives them a good advantage for use in different industries.

• Keywords: hydrogels, laponite, adsorption