Proučavanje uticaja različitih postupaka modifikacije na fizičko-hemijske karakteristike i sorpciona svojstva sepiolita
The influence of modification methods on physico-chemical and sorption properties of sepiolite Umnoženo za odbranu.
Докторанд
Lazarević, Slavica S.Ментор
Petrović, RadaЧланови комисије
Janaćković, ĐorđeOnjia, Antonije
Метаподаци
Приказ свих података о дисертацијиСажетак
Predmet ove doktorske disertacije je proučavanje uticaja modifikacije prirodnog
sepiolita primenom soli N-[(3-trimetoksi)propil]etilendiamintriacetatne kiseline
((CH3O)3Si(CH2)3N(CH2COONa)N(CH2)2N(CH2COONa)2), [3-(2-
aminoetilamino)propil]trimetoksisilana ((CH3O)3Si(CH2)3NH(CH2)2NH2)), 3-
merkaptopropiltrimetoksisilana (HS(CH2)3Si(OCH3)3) i gvožñe(III)-hlorida u baznoj
sredini na fizičko-hemijska svojstva sepiolita, kao i na sorpciju Cu2+, Co2+ i Ni2+ jona iz
vodenih rastvora i sorpciju organskih jedinjenja iz gasovite faze.
Karakteristično svojstvo površine, tačka nultog naelektrisanja, pHtnn, odreñena je
u rastvoru elektrolita različite koncentracije, kao i u prisustvu jona Cu2+, Co2+ i Ni2+.
Utvrñeno je da se tačka nultog naelektrisanja ne menja sa promenom koncentracije
rastvora KNO3, dok se u prisustvu Cu2+, Co2+ i Ni2+ jona pomera ka nižim pH
vrednostima, što ukazuje na specifčnu sorpciju jona.
Postupak modifikacije prirodnog sepiolita merkapto-silanom i amino-silanom
nije doveo ...do povećanja sorpcije jona. Uzorak modifikovan oksidom gvožña pokazao
se kao efikasan sorbent u sorpciji Cu2+, Co2+ i Ni2+ jona, dok je u slučaju modifikacije
vodenim rastvorom natrijumove soli N-[(3-trimetoksi)propil]etilendiamintriacetatne
kiseline uočen porast sorpcionog kapaciteta za Ni2+ jone.
Sorpcija jona Cu2+, Co2+ i Ni2+ iz vodenog rastvora rezultat je istovremenog
odigravanja procesa jonske izmene sa Mg2+ jonima iz sepiolitske strukture i specifične
sorpcije. Poreñenjem maksimalnih sorpcionih kapaciteta utvrñeno je kod svih ispitanih
sorbenata najveća sorpcija Cu2+ jona, zatim Co2+ jona a najmanja sorpcija Ni2+ jona.
Proces sorpcije ispitanih jona na prirodnom, kao i na modifikovanim sepiolitima
najbolje se opisuje Langmuir-ovom izotermom.
Promena pH vrednosti, u oblasti u kojoj ne dolazi do rastvaranja sorbenta i
hidrolize jona, nije bitno uticala na količinu sorbovanih jona na prirodnom sepiolitu,
kao ni na modifikovanim uzorcima. Sorpcija jona Cu2+, Co2+ i Ni2+ jona raste sa
porastom temperature. Pozitivne vrednosti promene entalpije sorpcije pokazuju da je
sorpcija endoterman proces.
Ispitivanje kinetike sorpcije, pri istoj polaznoj koncentraciji jona metala
pokazalo je da kinetički model pseudo-drugog reda najbolje opisuje eksperimentalne
rezultate, za sve ispitane sorbente.
Vrednosti konstanti jonizacije uzorka sepiolita modifikovanog gvožñe(III)-
hloridom u baznoj sredini (Fe-SEP) iznose: p
1
int
a K = 6,7 ± 0,1 i p
2
int
a K = 10,2 ± 0,1.
Uzorak ima veću relativnu kiselost površinskih funkcionalnih grupa u odnosu na
prirodni sepiolit, usled prisustva gvožñe(III)-oksihidroksida u strukturi modifikovanog
sepiolita.
Primenom inverzne gasne hromatografije u uslovima nulte prekrivenosti u
temperaturnom opsegu 483-513 K izračunate su vrednosti osnovnih termodinamičkih
parametara adsorpcije (slobodne površinske energije, standardne entalpije i standardne
entropije adsorpcije) na uzorku Fe-SEP, kao i specifična i disperzivna komponenta
slobodne energije adsorpcije. Rezultati ispitivanja interakcija uzorka Fe-SEP i kiselih,
baznih i amfoternih organskih molekula pokazali su da je površina ispitanog uzorka
baznog karaktera.
Na osnovu dobijenih adsorpcionih izotermi za n-heksan, benzen, hloroform i
tetrahidrofuran na sepiolitu Fe-SEP primenom inverzne gasne hromatografije u
uslovima konačne prekrivenosti u temperaturnom opsegu 483-513 K i B.E.T. jednačine
izračunate su vrednosti specifične površine, izosterične toplote adsorpcije, kao i
raspodela adsorpcione energije. Površina sepiolita pokazuje povećani afinitet prema
hloroformu usled uspostavljanja jakih kiselo-baznih interakcija.
The aim of this study was to investigate the influence of modification of natural
sepiolite using: 3-mercaptopropyltrimethoxysilane (HS(CH2)3Si(OCH3)3), [3-(2-
aminoethylamino)propyl]trimethoxysilane ((CH3O)3Si(CH2)3NH(CH2)2NH2)), N-[3-
(trimethoxysilyl)propyl], ethylenediamine triacetic acid trisodium salt
((CH3O)3Si(CH2)3N(CH2COONa)N(CH2)2N(CH2COONa)2) and iron(III)chloride in
basic conditions, on physico-chemical properties, sorption of Cu2+, Co2+ and Ni2+ ions
from water solutions and sorption of organic molecules from the gas phase.
The point of zero charge, pHtnn, as an important surface parameter, was
determined in electrolyte solutions with different initial concentration and in the
solution of M2+ ions. The value of pHtnn remains constant with changing concentration
of the KNO3 solution. The shift of the point of zero charge of sepiolite samples was
determined in the presence of Cu2+, Co2+ and Ni2+ ions indicating that specific sorption
of M2+ ions onto sepiolite samples had o...ccurred.
The improvement of the sorption efficiency of samples obtained by modification
of sepiolite with mercapto-silane and amino-silane was not observed. Modification of
natural sepiolite by iron oxyhydroxide resulted in formation of an effective sorbent for
sorption of Cu2+, Co2+ and Ni2+ ions, while in the case of modification by
ethylenediamine triacetic acid trisodium salt from water solution, the increase of
sorption capacity was deteced for sorption of Ni2+ ions.
The sorption of Cu2+, Co2+ and Ni2+ ions from water solutions is the result of the
process of ion exchange of Mg2+ ions from the sepiolite structure and specific sorption.
According to maximal sorption capacities, the sorption was the highest in the case of
Cu2+ ions, then Co2+, and the lowest in case of Ni2+ ions, for used all sorbent. The
equilibrium sorption process, for all investigated ions, on natural, as well as on modified
samples, was well described by the Langmuir isotherm model.
The change of the initial pH value, in the pH range where sorbent dissolution
and hydrolysis of ions can be excluded, did not affect the change of capacities of
sorption, on natural, as well on modified samples. The quantity of sorbed Cu2+, Co2+
and Ni2+ ions increased with increasing temperature. The positive enthalpy change
indicates that the process of removal of M2+ ions from water solution by sepiolites was
endothermic.
The sorption kinetic study showed that pseudo-second order was the model that
best described the experimental sorption data for all investigated ions and all the
sorbents used, indicating that the sorption may be controlled by chemical sorption.
The ionization constants of the surface functional groups of sepiolite modified
with iron(III)chloride in basic conditions (Fe-SEP) determined from the potentiometric
titration data, were p int
a1 K = 6.7 ± 0.1 and p int
a2 K = 10.2 ± 0.1. The relative acidity of the
surface functional groups was lower comparing to natural sepiolite sample, that can be
assigned to the presence of iron oxyhydroxide particles at the surface of modified
material.
The thermodynamic parameters (free energy, enthalpy, entropy) of adsorption as
well as dispersive and specific components of free energy of adsorption were calculated
from the inverse gas chromatography measurements for the probes on the sample Fe-
SEP in temperature range 483-513K. The results of interactions of Fe-SEP amd bacis,
acid and amphoteric organic probes indicate that Fe-SEP surface has basic character.
The sorption isotherms for n-hexane, benzene, chloroform and tetrahydrofurane,
on sample Fe-SEP, determined by inverse gas chromatography at finite concentration
condition in the temperature range 483-513 K, were used to estimate the surface area,
isosteric heat of adsorption and adsorption energy distribution function. The strong
interaction between Fe-SEP surface and chloroform, due to acid-base interactions, was
established.
Факултет:
Универзитет у Београду, Технолошко-металуршки факултетДатум одбране:
05-12-2012Пројекти:
- Синтеза, развој технологија добијања и примена наноструктурних мултифункционалних материјала дефинисаних својстава (RS-MESTD-Integrated and Interdisciplinary Research (IIR or III)-45019)