The properties of thermally modified porous glasses (CPG). III. The influence of long additional thermal treatment and the leaching process of CPG on the adsorption properties

Materials Chemistry and Physics, I1 (1984)

503-5

THE

MODIFIED

PROPERTIES

III.

THE

OF

THERMALLY

INFLUENCE

LEACHING

PROCESS

OF

14

503

POROUS

LONG ADDITIONAL

OF CPG

ON THE

GLASSES

THERMAL

ADSORPTION

(CPG).

TREATMENT

AND

THE

PROPERTIES

DAWIDOVJICZ

A.L.

Department of Chemical Maria Curie Sklodovska 20-031 Lublin Poland

Physics, University,

Institute M.C.

Received

accepted

2 May

2 April

1984;

of Chemistry, Sklodovska Squats

3,

1984

ABSTRACT The presented paper deals with the adsorption properties of controlled porous glasses (CPG) in which the thermally formed borate clusters have been removed from the surface of long-heated materials by means of the leaching process. The relationships used in comparing the surface nature of prepared packings are adsorption isotherms and isosteric heats of adsorption.

INTRODUCTION Among and

the

supports

chemically phy

of

are

glasses

pore

their

other

size

porous

things,

a

mainder phic

which

of makes

The changing

the work

the

B203

is

these

of

glasses materials

the

surface

thermal

heating diffuse

0254-0584/84/$3.00

of

boron treatment

a CPG

from

the

on

the bulk

a CPG

concentration. of boron to

the

the

of

the

inner c6,j,

gels.

the

possibility

can

glass

The

re-

chromatogra-

in surfaces

is

silica

The

the

silica

of

packings

c-0.57;).

from

remaining

surface.

from

Analysis

mainly

exist

their

.

these

Nap0

It

porous

atoms

obtained

of

from

of

with properies

4.5

consists

atoms

different feature

are

important

also

importance

structure

type

and

or

chromatogra-

Their

glasses

Boron and

liquid

porous

Vycor

(-3%)

fillings

adsorbed)

in

structure

especially

characteristic

proper

B203

column

physico-chemical

network

porous

viewpoint.

porous

the

the

their

the

amount

as k-33.

porous of

that

adsorption

structure

by

small

of

and

shows Besides,

well

their

and

as

(physically

as

from

glasses

.

used

porosity

Controlled

glasses

contains

gas

distribution

surface.

E.51

in

controlled

sodium-borosilicate

(-97%)

materials deposited

phases of

among

narrow

important

adhesively

bonded

results,

of

most

be

accomplished

p,g. in

of

the

During silica

concentration

netof

0 Elsevier Sequoia/Printed in The Netherlands

504 surface of

boron

a

change

in

the

In

proportional

formation .

many

cases

of

the

surface

boron

molecules

is

of

Such

a

porous

E ,131

or

classical difficulties.

the

use

of

not

completely

reaction ient on

the

ned

glass

of

can

This

into

removed

concentration

chemically

chemical

atoms

or

decrease

possible

be

surfaces

account.

The

borate

surface, in

phases,

film, be

is

a

capping

more

conven-

their when

.

cause

surface

given

amount

the

mentio-

long

thermal

hetcrogenations

thus

and

14

11

and

bonded

to

the

agents

glass

would

on

the

this,

by

. It

surface

with

avoid

deposited

the

even

electron

(

adhesively

pS,lg

may

glass

blocking

When

seems

the

porous

to

discussed

a CPG

insufficient

clusters

from

on

of

boron

borate

taken

be

the

surface

surface.

is

formed atom

with

the

of

necessary.

performed

been

course

interacting

often

case

of

of

12 . To Cl modified

frequently

the

is

be

the

formation

treatment

17

to

remove

very

temperature

electron-deficient

depositing

In

covered

ought to

is

are

pre-columns

has

specifically

adsorptive

procedures

certain

of

on

disadvantageous

glass

and leads

exposure

clusters

atoms

time

a CPG

which

thermal

presence

separated surface

long

borate

accepting)

bonding

the of

properties,

. A very

p-19

to

modification

adsorption

E,lg

surface

is

thermal

its

previously cause

atoms Such

heating.

lowering

the

v/hole

the

boron

;llaterial

11, C

.

3

EXPEiZIMENTAL IvIa terials The -type

glass

In

order

an

88

for

glasses

20

102 hrs

procedure to

as

atoms the

initial

and

then

hydroxylated fewer

the

of

a

glass with

porous

at

not

(having the

glass the

of

surface To

I

Si02

a

only

compare mainly

hydroxylated

was

is

glass

700°C

2

causes of

the

the glass

adsorption Si-OH

groups

material

referred

surface

for

600°C

described

on

lo

Vycar

sorbent at

henceforth

crystals

a

F-S].

heated

previously

the

borate

the

dehydroxylation.

B-OH)

70:s

into

sorbent

CPG

to

from

and

folowing

heated

obtained

material Vycor

of

were

23Y5 S203

enrichment

was

bulk

the

obtained

formation I

treatment the

of

The

the

crude

leached

For

I. for

porosity

7id Na20,

this

fraction

glass

from

surface

and

pm

glass

Thermal

of

transform

p,5,1S].

and

atoms

controlled

composed

to

-

of

in

the 75

hrs

(glass

diffusion but

of

also

on

boron

of

the a

II)

leads

properties

with

boron

surface,

to the

surface

high

concen

505 tration

of

boron

concentration in

O.lN

atoms

of

NaOH

for

In

order

portion

of

(glass

B-OH

30

at

to

of

is

a

slow

of

the

very

IV

0.5N

NaOH

of

was

the

Chromatoqraphic

were

that

min

)* method

rehydroxylated described

be

left

at

NaOH do

not

atoms

same

long

for

conditions

as

sorbents

not

the

for

2

enough

the

glass hrs

before

25’C

porous

boron

for

a

at

the

of

150

are

surface

hrs.

change

diffusion

in

700°C

isotherm out

of

the

by

atoms

the

removal

,

network) and

leached

(glass

V).

given

in

on

the

1

measurements

means

88

on

a

the

were

the

gas

Table

by The

I.

-

102pm.

The

carrier

The

adsorption

isotherms

presented

adsorption

isotherms

at

135.6 in

materiChrom

4

thermo-condu

1000

x

gas

was

(flow

using

correction. 151.2,

a

was

4 8

performed

175.1,

-

with used

sieve

were

obtained

chromatograph

columns

molecular

diffusion

198.4,

a

Czehoslovakia)

of

measurements with

of

Praha, size

particles dried

Isotherm

The at

was

measurements

carried

22 [ measurements

higher

previously

from

0.5N

may

obtained

adsorption

initially

gen,

in

the

it

‘2

Laboratorni Pristroje, ( ctivity detector. The and

II

the

crystallites

. Because

again

the

of

significantly

glass

using

conditions

21

boron

heated

under

properties

The

leached

was

process

majority

glass

borate

II

CPG

groups)

a

III).

leaching

the

by

15’C

remove

These

IV).

min.

(glass

glass

structure

als

surface

29,201

procedure

characterized

(

rate the

3

mm hydro-

25

peak

ml/

profile

temperatures

and this

of

119.6’C. paper

were

made

198.4’C. ‘The

calculating the

the

method

Porosimetric The

ted Carlo

materials

were

Erba

of

adsorption,

based

on

by

Q

for

used

, according

to

the

areas

were

patented

in

diameters

means

of

a

mercury

the

investiga-

porosimeter,

1500.

surface areas

and

pore

out

type

specific

surface

were

average

Italy)

of

Spectrographic

Zeiss

were ST

kO.233.

carried

(Milan,

constructed

8 O3

of

temperatures

investigations

Specific

ments

heats

known

measurements

Measurements

ment

isosteric

already

all

by

nitrogen

(BET)

investigated UMCS 8ET

Lublin

by

means

[24].

The

of

equip-

measure-

method.

measurements contents

PJena,

GDR).

were

estimated

The

investigations

emploing were

a spectrograph made

by

means

of of

Carl the

506 relative

method

amount

of

RESULTS In

DISCUSSION

the

previous treated

of

atoms an

these to

in in

The

the

the

were

of

glass

after

the

hydroxylated

with

the

additionally

known

final

the

to

product

and obtained

of

The

enriched

surfa-

in

have

boron

shown

that

causes

with

investigate borate

of the

the

an

properties

clusters

possessed its

a

were of

showing

a

clusters).

from

the

surfa

compared initial

high

glass

concentration

These

dehydroxylated

its

hydroxylated

properties surface

surface form

compared

discussed.

concentration

of

hydroxylated

the

properties

materials surface

were containing

crystallites.

average surface areas, atoms for investigated

Table I. Specific amounts of boron Specific areas

Materials

Glass Glass Glass Glass Glass

I II III IV V

in

evident

in

especially

data

the

that

boron IV

is

Cl. 11

process not

V

mean

and

Boron

content

p/w%]

of

preparatory

in

of

between

compared

the

obtained

glass

in

the

which

effective. glasses

to data

of

and

II

I.

used

samples. I

confirm

boron

boron

Table

glasses

thermal

The I

and in

procedure

comparison obtained

8203

2.76 2.68 2.61 1.26 0.98

diameters

the

repetition

with

pore are

The

The

particularly

contents

diameter

glesses

content

and

illustrative. in

leaching

boron

the

glasses

discussed

removed

pore

Pm1

areas,

investigated

from

of

Mean

pore diameters materials

29.2 27.8 28.5 29.9 29.4

surface

the

decrease

cases

s rface bs/g]

63.4 36.1 65.3 57.3 55.8

Specific tents

the

is

removal

procedure,

(in

atoms

work

the

with

the

a

properties.

this

all

boron

been

atom

applied

of

have

results

the

a

with

adsorption

dehydroxylated The

Because

borate

standards

the

boron

surface. after

1

surface

ce

of

glass

degrees.

adsorption

purpose

porous

and

of

9,lO c glasses

porous

different

increase

first

series

papers

materials

increase

of

a

AND

thermally ces

using

8203.

-

the

small shown

It

ere

results

were

and partly

in

difference in

is

causes The

III

treatment atoms

con-

Table

I

Is

507

probably the for of

connected

initial glass the

re

in

not as

glasses process

porosity

and

real

and is

surface I and

tion

II).

process

during

heating

process

of

the

glass

relation

removal

of

that

glass

fic

surface

area

specific

glasses

3 the

1,2

and

and

chloroform

shown.

To avoid

bents,

the

substance

the

surface.

experiments

; diethyl

increase

of

from

hydroxy

the

small

pore

differences of

the

adsorp

ether

initial of

the

a

has the

and

in

adsorbates

of

repeated

increase

surface

area

boron

of

enriched

adsorption of

the

initial

B-OH groups be

(in

supported

glasses

by

IV and

V.

the

speci-

decreases

isotherms investigated specific

were

as 1as:ahexane molecule

place

.

V

adsorption on the

of

the

cf. ( dehydroxyla-

takes

higher

can

surface

I the

hydroxylation

surface

amount

Table

material

causes

areas

IV

adsorption

which

explanation the

material

the from

further

III

with

diminishes

The

than

relationships The

seen

atoms

the

small

differences

9,lO c

is

of

a result

glass

from

see

ether

of

As

7OO’C.

surface

atoms

Figs.

earlier

of

results

.The specific Cl of glass I. Probably

This

diethyl

meter

of

treated

1

11

of

III).

the

diameter

be

connected

surface

area

a very

presented

procedu

conditions

Such

boron

is

at

that

boron

result

minimal

~,11,19,20]

contains the

values

of

strength

to

I surface

molecules

of

the The

In

in

nitrogen glass

and area.

surface

to

pore

investigation

partly

surface

diminution

comparison

the

surface

This

exceeds

which

I,

is

in

surface

for

as

preparatory can

procedure.

amount

boron-enriched

even

of

9.11.20.25 a long thermal C pore diameters in heated

of

for

area

rshydroxylated

explained

average

a result

before

which

glass

of

the

properties

as

decrease

the

glass

specific

III

glass

and

of

heating

concentration

surface.

value

the

be

applied

the

leaching

the

B203

differences

or

reported

specific

of

specific

can

the

small

errors

reflects

the

enrichment glass

The

the

of

A more

II

I that

insignificant

properties

centers

glass

I3203 during

the

process.

a small

are

porosity

to

in

cf glass I and II). The (2 materials III - V probably

for

lation

of

decrease

significantly

As was

diameters

evaporation

Table

packings.

ceuses

porous

of

from

influence

preparation.

tion

relation

measurement

treatment

the

A small

hydroxylation

obtained

either

in

I.

appears

does

the

III

applied

It

with

glass

of

surface

chosen

per on

a non-specific, which

are

areas

calculated

were

hexane,

glasses

contains

of

one

the

sor-

square

basis

non-polar an

oxygen

of

508 atom interacting types

of

molecule but,

very

hydroxyl that

also

contrary

a larger

198.4OC:

glass curve

atoms

interacts

specifically

with

one molecule

ether,

Cl.

and different

chloroform

as a

the CPG surface

of CHC13 occupies

10

40

60

80

7cO 120 p L’kN/rrFl

The adsorption isotherms of hexane on glasses I - V at glass I - curve I,0 ; glass II - curve II. l i IV - curve IV, l ; glass V III - curve III, a ; glass V, 8 .

Comparing

is

the

seen

tion

of

hexane

enrichment

the

properties however,

surface

they

are

still

The

initial large

specific

hexane

>

glass but

of

I

(

a

two

small

increase

the

boron

I,IV,V,

hydroxylated

in

a

a

9 see

and

( non-specific

surface

of

Fig.

the

9’ large the

1,

the

The

Fig.

of

same

V with

1)

the run

;

initial of

iso-

isotherm

of

variations

increase

are

in

non-

dehydroxylation curves

I and

interaction

containing

adsorp-

in agree-

adsorption

III,

curve

to

and

the

is

1,

The rehydroxylation

than that

Fig.

hexane

atoms

see

IV and

atoms

This

1). [9].

leads

things:

bstween in

and

atoms

curves

indicate

enriched

( higher

glasses

boron increase

a decrease

hexane

a little boron

data

in Fig.

presented

in

Fig.

causes

for

for

interactions

surface 2

removal

hexane

surface

discussed

the

characteristic

the

I and II,

surface

of

therms

of

the surface of

( previously

glass. the

of

curves

cf.

boron-enriched

not

isotherms

dehydroxylation

ment with the

adsorptton

that

simultaneous

and

boron

1.

Fig.

of

with

on the CPG surface;

to diethyl

area

20

it

sensitively

groups

numerous

II)~],

between boron

A

Y

,o

-=-80

2%

?_

70

0

60

20 Fig.

w

40

60 80 p Ik N/m2.1

2. The adsorption V at 198.4OC. For

I -

60

isotherms explanation,

of

3. The adsorption isotherms Fig. at 198.4oC. For explanation, see

atoms.

Thus,

non-polar

E-OH groups

molecules

on

ether

and

chloroform

than

curve

I (Figs.

ts

in

the

these

This

had

been

Table

I).

which

properties 3).

In

therms

of Fig. of

is

are

is

to

process glass

with that

the

V.

Curve

III

is

of

remove

boron

causes

a diminution

seen

In

the

surface a little.

III

atoms and

(here: heating

of

resul-

adsorbate glass

leaching of

IV in

between case

higher

the

from

the

be

diethyl

difference

process

curves

can of

distinctly of

V

with

conclusion

character

is

I -

strongly

isotherms

conspicuous

by the

additional

adsorption

same

where

on glasse

on glasses

more

The

3,

This

(cf.

IV and

ones.

specific

confirmed

This the

3).

the

performed

a little

2 and

shown.

2 and from

glasses

evident

IV decrease

Si-OH

Figs.

1 no difference

interacting it

of

cases

molecules. (see

basis

ether 1.

of chloroform Fig. 1.

interact

than

drawn

diethyl see Fig.

the the

surface adsorption

Figs.

1,2

adsorption

molecules

II

and iso-

specifically

chloroform

amd diethyl

and

leaching

of

surfaces

IV and V dif-

Probably

ether)

material

510 fer

insignificantly

been

observed

weakly

with

the

responding already

in in

to

the

the

case

obtained glass

discussed

of

Cl

in

groups,

hexane

The

relation

to

that

adsorption glass

which

has

isotherms

I

are

not

interacts

the

same

coras

.

20. I

-

20

70

B-OH

non-polar

glasses.

II

9

amount of

a [3j+jxlti Fig. 4. The for the

hexane number

isosteric heats of adsorption on alasses I - V. The numbers of the glass.

70

5. Fig. glasses glass.

The I -

20

isosteric V. The

30

heats numbers

40

50

of adsorption on the curves

vs.

adsorbed curves

on the

60

amount correspond

-

for give

diethyl ether the number of

on the

511 The ter

of

property

the

amount

adsorbed

t ively.

From

(

for

curves

I,

highly

III,

is to

This

It

the

lated

of

materials the

surface

to of

glass

4, -cf. presented

belong

glass

is

one

to

another C

III,

IV

and

10,

V

surface.

surface

should

tendency of

with

to

a

be

the

4,

QST

of

adsorp-

molecules

case

of

hydroxy

is weaker.

enough

to investi-

results

presented

point

4 shows a drop the

boron

highest

boron-enriched

I).

of

V seems

the

According

isosteric

heats

and hydroxylated

glass

to

in surface

content

V and Table

presents

of

mechanism

the

best

slope

the adsorbed

IV,

of

the

in the

to

sensitive

in

surface

tend

the dehydroxy

form conglomerates

Fig.

III,

the

than

not

decrease

in Fig.

for

though

of

CPG and the

curves

and the

in

to

is

probably

observed II,

greater

However,

Fig.

III,

of

molecule

surface hexane

data

glass

I,

molecules

the affinity

II

and the

for

adsorption

respecseems

hydroxylated

is

from a change

interaction.

(

the

Non-polar

that

hexane

polar

activity

the

the amount adsorbed

one with

on a hydroxylated

surface

results

surface

The non-polar gate

vs.

surface

QST vs.

possess

charac-

adsorption,

and chloroform,

glasses

The same effect

may be said

a similar

for

which

molecules.

boron-enriched

lower,

of

of

adsorption

adsorbing

interact

the

heat

[27]. The significant increase of QST for hydroxyIII, IV and V may be due to a mutual interaction I,

adsorbed

tion.

of

ether the

slope

adsorbed

form conglomerates. lated

diethyl

about

isosteric

heats

evident

IV and V)

information

the

hexane,

molecules

molecules

glasses

between

for

especially

mobile

lated

is

isosteric

hexane,

4.

hexene

is

Non-polar

some

The positive

that

261 . This

the

Fig.

homogeneous.

suggest

gives

surface

4 - 6 present

Figs.

be

which

adsorption

of

surface

to be the

most

homogeneous. The molecule ce and is ether.

that

most useful

When an oxygen

present

in the

ly

with

electron-deficient

of

hydroxyl

tion

for

trast

groups

(C2H5)2*0

to hexane,

and

III

are

heterogeneous.

material high

ether

( curves (glass

concentration

for

the

the

atom containing molecule,

on the

the

boron

In the

cases

electron

The isosteric

the adsorption of I - III respectively) of

the

ether

indicates the surfaces

different heats on

types of

5. glass

that of

is

specifical

shown in Fig.

diethyl

surfa-

diethyl

pair

interactions

and with

I - V are

of

of CPG is

a donor latter

atoms

surface.

on glasses

properties

characterisation

adsorpIn conI,

II

the surfaces

the

initial

I - curve I and a hadroxylated surface with a ) of boron atoms glass III, curve III) the (

512

heterogeneities hydroxyl

result

from

the presence

of

. This is consisted L 1 The heterogeneity of [6-ll] .

groups

CPG surface

was discussed

Comparing

in Fig.

curves

I,

II

similarly

to hexane,

B-OH groups clusters

is

from

from the

and III

the heterogeneity

(see

glass

III

surface

5,

curves

to

of

of

of

the

surface borate

previously

crys-

EO,ll] .

OH groups

can be said

II and III)

and that,

highly

than glass

leads

II

existence

containing

more energetic the

types

our picture

the glass

see curve II, Fig. 5) results ( tallites on its surface, which to obscure

various

with

6-S

I.

concentrated

The removal

the homogenization

of of

borate

glass

surface glasses IV and V, curves IV and V in Fig. 5). giving ( ST a simultaneous decrease of Q . Curve V in Fig. 5 (glass V) suggests

a positive

and leaching

process

on

glass

influence

between

IV and glass

of

IV upon

glass

The difference

surface.

for

but small

the

V is

in this

6 the

isosteric

the additional

the

heterogeneity

isosteric case

heating of

heats

of

more explicit

the

adsorption than in

hexane. ,Finally, adsorbed

in Fig.

amount

for

chloroform

is

heat

of

adsorption

vs.

the

presented.

30

20

Fig. ses the

6.

The isosteric

I - v, glass.

The

The investigated homogeneous.

heat

numbers

on

surfaces

Especially

have energetically

uniform

of

adsorption

the

of

curves

for

hydroxylated

glasses

chloroform

correspond

to

glasses

IV and V (borate

surfaces

and

the

the

seem

on glasnumber

to

be

of

chloro-

clusters

QST values

of

remove 4

513 form

molecules

lated

lated

This

is

is

taken

surface

with of

borate

hydroxyl

chloroform of

interacts

probably

CPG

and

assumes

a

the

surface

boron

According

to

acts

a

with

sequence a

the

is

diethyl

above

larger not

a

model, of

atoms

the

sensitive

to

the

hydroxy-

obscuring The

the

utili-

surface

ether.

its

three This

groups

Chlorochlorine

should have

be

so

electron-

electron-donors.

molecule

adsorbent

of

(a

III).

diethyl

are

single

III

and

via

hydroxyl

chlorine

area so

ether

and

presence

of

and

surface

hydroxy-

heterogene-

the

II

configuration.

atoms

and

the Curve

confirms

hexane the

all

most

investigation

between

of

the if

curves

the

tripod-like

properties

lowest is

account.

(cf.

with

since accepting

into

in

is

atoms

II

crystalites)

molecule

form

the

glass

understandable

groups

heterogeneity

are

of

chloroform.

properties of

adsorbents

surface

conglomerates

for

borate

these The

materials.

ous

ty

on

of

changes

CHClS 10

surface

inter-

1

and

in

[ heterogeneity

of

conas

molecule.

CONCLUSIONS The

employed

has

been

the

surface.

vation

shown

CPG The

of

cause

were

necessary

pore

and does

the

leads

not

that

boron to

atoms

the

require

initial

any

of

from

CPG

homogeneity

as

strong

of

a

deacti-

glass.

the

second

substantia.1

thermal

treatment

changes.in

the

and properties

surface.

data

different

removal

effective

suggest not

of

surface

surface

does

the

be

the

be a

results

leaching of

to

Such

as The

procedure

to

obtained

repeat

porosity

for

the

one

same

(glasses

type

of

glass.

investigation

possessing

It

with

narrow,

seems

to

glasses

medium

of

and

large

diameters

)a existance

The

of

OH groups

on

the

CPG

surface

decreases

its

heterogeneity. The CPG

best

surface

molecule is

formation

of on

A CHC13

molecule

larger

atoms are

the

area and

more

diethyl

is

(even not

the

as

clusters

sensitive

to

In not

of

heterogeneity the

as

hexane

and types

ether the

of

because

These of

the

surface.

the

of

the

presence

significant.

hydroxylation

of

probability

molecules

different

sensitive

is the

ether with

surface.

borate

the

because

between

surface

on

investigate

ether,

complexes

centers

a

to

the

adsorption OH groups). it of

occupies boron

molecules

514

REFERENCES i 2 3 4 5 6 7 8 9

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1980

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