Novel biocide multifunctional materials basedon mesoporous silicas modified by treatmentwith guanidine polymersand mercaptopropyltrimethoxysilane: synthesis,characterization, and applications

Alexander Timin • Evgeniy Rumyantsev

Received: 19 March 2013 / Accepted: 6 August 2013

� Springer Science+Business Media Dordrecht 2013

Abstract Mesoporous thiol- and guanidine-modified silicas with narrow pore size

distribution were prepared by the sol–gel technique. The surface area of the silicas

was modified by 3-mercaptopropyltrimethoxysilane (MPTMS) and guanidine

polymers: polyacrylate guanidine (PAG) and polymethacrylate guanidine (PMAG).

The mesoporous silicas were characterized by nitrogen adsorption–desorption

analysis, Fourier transform infrared spectroscopy (FTIR), and the laser diffraction

method. The materials obtained were used as adsorbents for removing heavy metal

ions (Cu2?) from water. It was determined that modification of the silica surface by

MPTMS and guanidine polymers provides the new sorbents with high adsorption

capacity compared to non-modified silica. The equilibrium adsorption ability of

Cu2? ions on the surface of silicas modified by PAG and PMAG was 65 and

99.8 mg/g, respectively. Moreover, the modified silicas obtained were tested on the

antimicrobial activity in vitro: Gram-positive prokaryotes in the Staphylococcus

genus and Gram-negative prokaryotes in the Escherichia genus. The results showed

that only silica-modified guanidine polymers had high antimicrobial activity. All in

all, the silicas modified by guanidine polymers are more effective than thiol-mod-

ified silica for removing heavy metal ions from aqueous solution, and can also be

used as biocide materials for surface sterilization.

Keywords Sol–gel � Mesoporous silicas � Adsorbent � Heavy metals �Surface area � Biocide � Antimicrobial activity

A. Timin (&) � E. Rumyantsev

Department of Inorganic Chemistry, Ivanovo State University of Chemistry and Technology

(ISUCT), 7, Sheremetevsky prosp., Ivanovo, Russian Federation

e-mail: a_timin@mail.ru

123

Res Chem Intermed

DOI 10.1007/s11164-013-1361-3

Introduction

Nowadays, mesoporous materials based on silicas have been used as adsorbents,

catalysts, and catalyst support [1]. A great number of different adsorbents are used

for solving different environmental and pollution problems. However, many of them

are not very effective because they suffer from a low removal capacity, specific

surface area, low porosity, long equilibrium time, low selectivity, etc. [2].

At the present time, nanotechnology approaches have been successfully applied,

especially the sol–gel method due to its simplicity and efficiency. A great many

different adsorbents It have been synthesized through the sol–gel process based on

silica [3–6]. It is well known that active silica with a large specific surface area is of

great importance in adsorption and ion exchange. These properties are well studied,

even though the shape of silica surface is basically unknown [7]. Template methods

are currently used to synthesize silicas with a large pore size and pore volume [4].

Usually, surfactants are applied to form the required pore size [4], but there are

many problems following synthetic procedures because the template molecules

need to be removed. For this reason, silica surface modification is one of the most

promising ways to improve the adsorption (removal capacity, equilibrium time,

selectivity), and structural and morphological properties (specific surface area, pore

size, pore volume). There are two well-known techniques to modified silica

surfaces: one is to use organosilanes with different functions, such as –NH2, –SH,

–COOH, etc. [8, 9]; the second is to immobilize the bioorganic molecules in a silica

matrix during the sol–gel process. Such types of modification can change the

morphology and physical properties of the obtained materials (specific surface area,

pore and volume size) [10, 11]. The most convenient way to develop a chemically

modified surface is achieved by simple immobilization (or fixing) of the group on

the surface by adsorption, electrostatic interaction, or hydrogen bond formation or

other types of interaction [12].

Biocide polymers are now one of the most interesting classes because they are

harmless and have a high selective capacity relative to large amounts of different

compounds. Moreover, they can be used as templates and for surface modification

and in medicine for the creation of antimicrobial surfaces [13]. In fact, modification

of the silica surface by these polymers provides new and highly effective materials

with new physicochemical and biological properties [6]. Among such biocide

polymers are guanidine polymers: polyacrylate guanidine (PAG) and polymethac-

rylate guanidine (Fig. 1). These guanidine polymers can react with different

compounds via chemical and electrostatic interactions.

Sol–gel technology is used to synthesize hybrid materials to modify different

organo-chelating molecules. These materials have successfully been used for

purification of water contaminated with heavy metals [14]. However, there are no

studies related to the application of silicas modified by guanidine polymers for the

selective removal of copper ions from water or on the influence of these polymers

on physical, chemical, and antimicrobial properties of modified silicas.

The aim of the present work is to investigate the influence of the modification of

silica on the structural and morphological properties with the following applications

of the obtained materials for the selective removal of Cu2? ions from water, and for

A. Timin, E. Rumyantsev

123

antimicrobial investigations against Staphylococcus and Escherichia coli. We focus

on the ways to modify the silica surface. We also compare the adsorption capacity

of guanidine-modified silicas with non-modified silica and thiol-modified silica. We

present chemical, physical, and biological studies of the obtained materials prepared

by the sol–gel technique.

Experimental

Materials and methods

3-Mercaptopropyl trimethoxysilane (MPTMS 95 %) and tetraethyl orthosilicate

(TEOS 99 %) were purchased from the closed-company ‘‘Ecos-1’’. Cetyltrimeth-

ylammonium bromide (CTAB 99 %) was purchased from Sigma-Aldrich. All the

above materials were used without further purification. Nitrate of copper

(ChemMed, Russia) was used to prepare the metal ion solutions. Deionized water

was used throughout this work. The guanidine polymers: PGA (M = 400,000) and

polymethacrylate guanidine (PMAG) (M = 500,000) were synthesized at the

department of macromolecular compounds of the Kabardino-Balkar State Univer-

sity by N. M. Berbekova. They were recrystallized from a water–acetone mixture

followed by drying under vacuum at 60 �C.

Escherichia coli (ATTC 25922), Staphylococcus aureus and nutrient agar were

provided by Laboratory for Microbiology—Ivanovo State Medical Academy,

Russia.

Synthesis of non-modified silica

A typical synthetic procedure of non-modified silica used TEOS and water in

relative molar ratios of 1:4 [15]. In a typical synthesis, 4 g TEOS was mixed with

1.668 g water and vigorously stirred for 2 h. And then 0.05 ml of ammonium

hydroxide solution (NH4OH 5 %) was added every 25 min as a base catalyst. The

final product was transferred into a Petri dish for solvent evaporation at room

H2C C

R

CO O

H HN

CH2N NH2 n

+

-

a

H2C C

R

CO O

H2N NH2C

NH2

n

+

-

b

H2C C

R

CO O

NH2

CH2N NH2

_

+

nc

R = H - polyacrylate guanidine (PAG)R = CH3 - polymethacrylate guanidine (PMAG)

Fig. 1 Structural formulas of guanidine polymers (a, b, c)

Treatment of biocide multifunctional materials

123

temperature. The obtained powder sample was dried under vacuum at 100 �C during

2 days.

Synthesis of silicas modified by guanidine polymers

The synthesis of silicas modified by PAG and PMAG was similar to the one

described above. It was used the same molar ratio of TEOS/H2O as in previous

syntheses. In a typical synthesis, 0.2 g PAG was dissolved in 1.667 g water during

the sol–gel process to prepare solutions with the necessary concentration of PAG.

Then, the prepared solutions were mixed with TEOS and vigorously stirred for 2 h.

The same synthesis route was applied for silica modified by PMAG (0.2 g). The

ammonium hydroxide solution (0.05 ml) was added every 25 min as a base catalyst.

The final product was transferred into a Petri dish for solvent evaporation at room

temperature. The obtained powder samples were dried under vacuum at 100 �C

during 2 days. The synthesis route is shown in Fig. 2.

Synthesis of thiol-modified silica

TEOS and MPTMS were used in relative molar rations of 4:1. For this procedure,

1.667 g water, 0.95 g MPTMS, and 10 g ethanol were mixed and stirred for 20 min.

Si

OC2H5

OC2H5

OC2H5C2H5O + 4xH2O Si O Si O Si

O

Si

O

Si

OH

OH

HO

OH

OHHO

OH

OH

OH

OH

OHHOH2C C

R

CO O

H HN

CH2N NH2 z

+

-

HydrolysisPolycondensation

x

y

+

Immobilization

NCO

O

H

HC

NH2

NH2

C

R

CH2 - +

NC

O

O

H

H CNH2

NH2

C

RCH2

N

CO O

H H

CH2N NH2

CR

H2C

Si O Si OSi O

Si O

Si

O

Si

OSiO

SiO

SiO Si O

Si O Si O

OH

SiOH

OH

Si OH

OHOH

OH Si

HOHO

O

SiO

HO+

-

n

- +

Fig. 2 The synthesis route to silicas modified by PAG and PMAG (n = y ? z)

A. Timin, E. Rumyantsev

123

Then, 4 g TEOS and 1 g CTAB were slowly dripped into the mixture. After the

addition of TEOS was complete, the mixture was stirred for 2 h. Then, 0.05 ml of

ammonium hydroxide solution (NH4OH 5 %) was added every 25 min as a base

catalyst. CTAB was used as a surfactant to form the required pore size inside the

silica matrix. The final product was transferred into a Petri dish for solvent

evaporation at room temperature. Then, the obtained powder samples were

extensively washed in hot water–ethanol solution at 70 �C in order to remove

CTAB from the silica matrix and dried under vacuum at 100 �C during 2 days.

Characterization of mesoporous adsorbents

The obtained materials were characterized by common analytical techniques.

Nitrogen adsorption measurements were carried out at 78 K using Micromeritics

ASAP 2020 analyzer (Norcross, GA, USA). The specific surface area was calculated

by employing the Brunauer–Emmett–Teller (BET) method [16] in the range of

relative pressure from 0.05 to 0.25. Before the experiment, all samples were

degassed at 100 �C under vacuum. The pore volume and pore size distributions

were calculated using the Barrett–Joyner–Halenda (BJH) model [17] on the

desorption branch. FTIR spectra were obtained on Avatar 360 FTIR spectrometer

(Thermo Nicolet, USA) by the KBr pellet method. The particle sizes of the obtained

materials were measured by laser diffraction method on an Analysette 22 Compaq

(Fritch, Germany).

Antimicrobial tests

Antimicrobial activity of the prepared silicas containing PMAG and PAG was

evaluated using cultures of Staphylococcus genus (S. aureus associated with skin

and mucous membranes was used as test microbe) and gram-prokaryotes

Escherichia genus (E. coli associated with the gastrointestinal mucosa was used

as test microbe). The experiments were carried out in solid media. In order to

prepare the solid medium agar, a microwave safe container was used for mixing and

heating the agar with water. These mixing proportions make enough medium agar in

order to prepare two halves of the Petri dish with boiling for 1 min to completely

dissolve the agar. Then, the obtained textile materials were put inside a Petri dish

and incubated for 24 h at 37 �C.

The adsorption isotherms of the non-modified and modified silicas

To measure the adsorption isotherms, approximately 50 mg of adsorbents and 10 ml

of Cu2? solution with different concentrations (0.01, 0.02, 0.04, 0.06, 0.08, 0.1 mol/

l) were added to a 20-ml flask and shaken for 60 min at 293 K. The initial pH value

was adjusted to 5 with dilute nitric acid and sodium hydroxide solution. The pH

values were measured by a pH-meter U-500 (Aquilon, Russia). The effect of the

solution pH on the adsorption of Cu2? has been studied by Wu et al. [2], who

showed that, when pH equals 5, the adsorption of Cu2? from water is at a maximum.

So, this pH value was chosen as the optimum pH value for the maximum removal of

Treatment of biocide multifunctional materials

123

Cu2? ions from the water solution. The concentration of copper ions (Cu2?) in the

water solution was determined by UV–Visible spectroscopy using the values of

optical density. The UV–Visible spectra of solutions and suspensions were recorded

on a SF-104 spectrophotometer (Aquilon).

The magnitude of Cu2? adsorption on the surface of non-modified and modified

silicas was determined as the difference between the initial and equilibrium

concentrations in a water solution (pH 5) after contact with a sorbent, using the formula

Q ¼ ðCo � CadsÞ � Vm

ð1Þ

where Q is the magnitude of Cu2? adsorptions, mmol/g; Co and Cads are the initial

and equilibrium concentration of Cu2? in a water solution, mmol/l; V is the volume

of the solution, L; and m is the mass of the sorbent sample e.g.

Results and discussion

Characterization of the obtained materials

The adsorbents were examined by FTIR to characterize the influence of adding the

guanidine polymers and MPTMS during the sol–gel process on the structure and

morphology of the obtained adsorbents. The FTIR spectra of non-modified silica

and the silicas modified by guanidine polymers are presented in Fig. 3. The FTIR

spectrum of non-modified silica has the following important bands: 3,47073,420,

1,630, 1,390, 1,06071,220, 960, and 798 cm-1. The features around 960 and

1,060 cm-1 are assigned to the Si–O–Si stretching vibrations [18, 19]. The

vibrations of Si–OH appeared around 1,630 and 3,470 cm-1 [20].

500 1000 1500 2000 2500 3000 3500 4000

Si-O

H

C=

NN

3

2

T, %

v, cm-1

1

Si-O

-Si

Fig. 3 A FTIR spectra pattern of the obtained adsorbents: non-modified silica (1), PAG-modified silicawith a content of the PMAG of 0.2 g (2), PAG-modified silica with a content of the PMAG of 0.2 g (3)

A. Timin, E. Rumyantsev

123

The FTIR spectra of silicas containing PAG and PMAG show the same peaks,

which correspond to Si–O–Si and Si–OH vibrations. However, the peak at

860 cm-1 corresponds to the CH2=C non-planar bending vibrations. The bands

around 1,680 and 1,656 cm-1 correspond to the N=C stretching vibrations and the

NH2 bending vibrations [13]. Furthermore, the bands in the range from 3,650 to

3,200 cm-1 characterize –OH groups of intermolecular hydrogen bonds. The

obtained results proved that the guanidine polymers have been successfully

immobilized on the silica surface and inside the silica skeleton via the sol–gel

process.

The FTIR spectrum of thiol-modified silica is represented in Fig. 4. The FTIR

spectrum of thiol-modified silica also characterized the peaks which are typical for

non-modified silica. However, the spectrum of thiol-modified silica shows

characteristic bands for mercapto groups around 2,551 cm-1 [3, 21], so we

conclude that mercapto groups have been successfully grafted onto the silica surface

by hydrolysis and polycondensation.

We performed the laser diffraction method to determine the particles size

distribution. The obtained results are presented in Fig. 5. The non-modified silica is

characterized by the most narrow particle size distribution (range from 0.22 to

6 lm). Such a synthesis procedure of non-modified silica allows the obtaining of the

silica with average particle size equal to 6 lm. However, nanoparticles (\0.68 lm)

are also obtained, and it is clear that the addition of guanidine polymers and

MPTMS leads to an increase in particle size. The most intensive peak for silica

modified by PAG ranges from 2 to 6 lm. As for silica modified by PMAG, it ranged

from 5 to 12 lm. The silica modified by MPTMS is characterized by the widest size

particle distribution and the biggest particle size (from 0.09 to 8 lm). According to

the polycondensation process, MPTMS is more reactive than TEOS and can easily

form large particle agglomerates.

500 1000 1500 2000 2500 3000 3500 4000

Si-O

H

1

v, cm-1

T,%

2

SHSi-O

-Si

Fig. 4 A FTIR spectra pattern of the obtained adsorbents: non-modified silica (1), thiol-modified silica(2)

Treatment of biocide multifunctional materials

123

The mesoporous structure of the modified silicas is confirmed by nitrogen

adsorption using BET analysis. The isotherms of silicas containing PAG and PMAG

are identical, so only the isotherm of silica-modified PAG (c) was presented in

Fig. 6. The isotherms b and c (thiol-modified silica and silica modified by PAG)

correspond to the IV type of isotherm which is typical for mesoporous materials

(Fig. 6). The isotherm b is characterized by more intensive hysteresis loop. But the

isotherm a (non-modified silica) shows that this adsorbent is not porous.

The specific surface area of the adsorbents was determined using the multipoint

BET measurement. According to the BJH method, the pore diameter and the

average pore diameter of the adsorbents were determined [16]. The structural

properties of the adsorbent samples are shown in Table 1.

It is clear that the pore size of the silica increased after modification. The surface

area, pore volume, and pore size of the modified adsorbents were all higher than the

non-modified silica. The non-modified silica is not porous, whereas the thiol-

modified silica is characterized by the greatest surface area. The pore diameter of

silica modified by PAG varies over a range of 8–13 nm and the average pore

diameter is 11 nm. This can be explained by the fact that molecules of guanidine

polymers can serve as a template to form the necessary pore sizes for obtaining

mesoporous materials. The pore diameter of thiol-modified silica varies over a range

of 5–7 nm and the average pore diameter is 6.31 nm (Fig. 7).

According to sol–gel synthesis, CTAB is used as a surfactant-template to form

the required pore size. The thiol-modified silica is characterized by the narrowest

pore size distribution compared with silica modified by PAG (Fig. 7).

(a) (b)

(c) (d)

Fig. 5 The particle size distribution of the obtained materials: non-modified silica (a), silica modified byPAG (b), silica modified by PMAG (c), silica modified by MPTMS (d)

A. Timin, E. Rumyantsev

123

Antimicrobial property of the obtained materials

Antimicrobial activity of the prepared materials was investigated against E. coli and

Staphylococcus in solid nutrient media. Before the experiment, all tested samples

were grafted onto paper discs. Pure silica, a paper disc and a piece of textile fabric

were used as control samples. After 300 min, the experimental activity results are

more evident. It is clear that only silicon oxides containing PAG and PMAG were

shown to have high antimicrobial activity suppressing the test cultures’ growth. The

zone of growth retardation of Staphylococcus on solid nutrient medium was more

than 35 mm (Fig. 8). Next, the experiment was repeated and the same results were

obtained . Figure 8 demonstrates a high antimicrobial activity of silica-containing

guanidine polymers against E. coli and Staphylococcus bacteria. This demonstrates

a potential application of the silica-containing guanidine polymers in the textile

industry and in medicine for the formation of antimicrobial surfaces.

(a) (b)

(c)

Fig. 6 Nitrogen adsorption–desorption isotherms of the synthesized materials: non-modified silica (a),thiol-modified silica (b), silica modified by PAG (c)

Table 1 Physical properties of

the obtained adsorbentsNo Sample Specific

area (m2 g-1)

Pore volume

(cm3 g-1)

Pore size

(nm)

1 SiO2 40 0.015 3.21

2 SiO2/PAG (0.2 g) 160 0.217 8–13

3 MPTMS/SiO2 345 0.312 5–7

Treatment of biocide multifunctional materials

123

The adsorption isotherms of the modified and non-modified silicas

Langmuir (Eq. 2), Freundlich (Eq. 3), and Redlich–Peterson (Eq. 4) equations were

used to analyze the experimental adsorption isotherms in Fig. 9.

Qe ¼QbCe

1þ bCe

ð2Þ

Qe ¼ KFC1=ne ð3Þ

Qe ¼KRCe

1þ ARCbe

ð4Þ

where b is the Langmuir isotherm constant. The ratio of Qe (mmol/g) gives the

theoretical monolayer saturation capacity of the adsorbent, Ce is the equilibrium

concentration (mmol/l) of Cu2? ions.

In the Freundlich model (Eq. 3), KF and n are constants specific to the adsorbent.

In the Redlich–Peterson model (Eq. 4), KR and AR are the specific isotherm

constants, and b is the exponent, which ranges from 0 to 1 (when b equals to 1, the

Redlich–Peterson equation becomes a Langmuir isotherm). The adsorption

isotherms of Cu2? are presented in Fig. 9. The adsorption values of Cu2? ions

increased rapidly in the initial phase and then the increasing trend decreased as the

initial concentration increased. The equilibrium adsorption capacity of Cu2? on

non-modified silica, thiol-modified silica, silica modified by PMAG, and silica

modified by PAG was 21.3, 38, 65, and 99.8 mg/g at 298 K, respectively. The

modification by MPTMS and guanidine polymers leads to the increase of the

adsorption value of Cu2? due to chemical and electrostatic interactions between

amino and mercapto groups of the modified silica and Cu2? ions. In spite of the fact

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

d,nm

cm3/nm/g,d

V∂∂

1

2

3

Fig. 7 Pore size distribution of the obtained adsorbents: non-modified silica (1), thiol-modified silica (2),silica modified by PAG (3)

A. Timin, E. Rumyantsev

123

that thiol-modified silica has a larger surface area, the adsorption capacity of silica

modified by guanidine polymers is higher. This might be explained because

guanidine polymers are more reactive than the mercapto groups of thiol-modified

silica. The adsorption capacity of silica modified by PAG is higher than the

adsorption capacity of silica modified by PMAG. This might be associated with the

role of structural factors: –CH3 groups in PMAG which may prevent the interactions

between Cu2? ions and functional groups of polymers.

The adsorption equilibrium data of Cu2? were analyzed with the above

Langmuir, Freundlich, and Redlich–Peterson adsorption equations. The corre-

sponding parameters are listed in Tables 2, 3, and 4. According to the correlation

coefficients, the adsorption isotherm for the non-modified silica adheres to the

Langmuir equation, which characterizes formation of a surface monolayer.

According to the correlation coefficients of the adsorption isotherms of Cu2? onto

modified silicas, the Redlich–Peterson model is the most suitable. The adsorption

process of Cu2? onto the surface of modified silica is more complicated because of

the chemosorption. It can be supposed that the chemosorption process can be caused

Solid medium agarStaphylococcus

results of test-tubes growth-free seedingStaphylococcus

Solid medium agarE. Coli

results of test-tubes growth-free seedingE. Coli

Fig. 8 Results of antimicrobial tests: 1 silica modified by PMAG (0.2 g), 2 thiol-modified silica, 3 silicamodified by PAG (0.2 g), 4 pure silica, 5 paper disc, 6 piece of textile fabric

Treatment of biocide multifunctional materials

123

by the electrostatic interactions between positively charged metal ions and

negatively charged silica matrices of thiol-modified silica [2] and silica modified

by guanidine polymers [13]. Also, the increase of the adsorption capacity of Cu2?

may be associated with chelation (the formation of co-ordinate bonds between

functional groups of guanidine polymers and metal ions).

Moreover, a large specific surface area of the modified silicas can also lead to

increased adsorption capacity of Cu2?. All in all, it was shown that the

modification of the silca surface by MPTMS and guanidine polymers increased

the specific surface area and adsorption capacity of Cu2? compared to non-

modified silica.

0.2

0.4

0.6

0.8

1.2

1.4

1.6

0

1

0.1 20.1 40.1 60.1 80.1 100.1

C, mmol/L

RedlimodeLangm

MPTM

SiO2/

SiO2/

SiO2

ch-Petersonelmuir model

MS/SiO2

/PMAG(0.2

/PAG(0.2 g

n

l

2 g)

g)

Q,mmol/g

Fig. 9 Isotherms of Cu2? adsorption on the surface: non-modified silica (SiO2), thiol-modified silica(MPTMS/SiO2), PMAG-modified silica with a content of the PMAG of 0.2 g (SiO2/PMAG(0.2 g)), PAG-modified silica with a content of the PAG of 0.2 g (SiO2/PAG(0.2 g))

Table 2 Nonlinear fitting parameters and equations of the Langmuir model

Sample Average value of fitting parameters Equations

b Qe r2

SiO2 9.38 0.3333 0.993 Qe = 3.09Ce/(1 ? 9.38Ce)

MPTMS/SiO2 18.58 0.5920 0.986 Qe = 10.99Ce/(1 ? 18.58Ce)

SiO2/PMAG (0.2 g) 14.84 0.9267 0.988 Qe = 13.75Ce/(1 ? 14.84Ce)

SiO2/PAG (0.2 g) 12.89 1.5649 0.994 Qe = 20.17Ce/(1 ? 12.89Ce)

pH 5, the weight of the adsorbent equals to 50 mg, sample volume = 10 ml, equilibrium time = 60 min

A. Timin, E. Rumyantsev

123

Conclusions

The multifunctional mesoporous-modified silicas with high adsorption capacity for

Cu2? ions were synthesized through the sol–gel process. It was determined that

modification of the silica surface by guanidine polymers and MPTMS leads to an

increase of the physical properties (specific surface area, pore volume, and pore

size) of the obtained adsorbents and the adsorption capacity for Cu2? ions. The

particle size of the obtained materials was determined. According to the correlation

coefficient (r2), the adsorption isotherms for modified silicas fit the Redlich–

Peterson nonlinear model. The silicas modified by guanidine polymers are more

effective than silica modified by MPTMS for the removal of heavy ions. Addition of

polymers and MPTMS in the sol–gel matrix leads to increased particle size

distribution. Moreover, the obtained materials were tested for antimicrobial activity

against E. coli and Staphylococcus bacteria and only silicas containing guanidine

polymers showed excellent antimicrobial properties in solid medium agar. The

obtained results show a potential application of the obtained materials in different

branches of science and technology, both as effective adsorbents for the removal of

heavy metals from water and as biocide materials.

Acknowledgments We thank Dr. Khashirova S. Yu., department of macromolecular compounds, the

Kabardino-Balkar State University by N.M. Berbekova, for synthesis of guanidine polymers. The work is

supported by the Grant of the RFBR (Project No. 12-03-31309).

Table 3 Nonlinear fitting

parameters and equations of the

Frendlich model

pH 5, the weight of the

adsorbent equals to 50 mg,

sample volume = 10 ml,

equilibrium time = 60 min

Sample Average value of fitting

parameters

Equations

KF n r2

SiO2 14.48 1.439 0.870 Qe = 14.48Ce0.695

MPTMS/SiO2 11.79 1.491 0.981 Qe = 11.79Ce0.670

SiO2/PMAG (0.2 g) 5.99 1.424 0.988 Qe = 5.99Ce0.702

SiO2/PAG (0.2 g) 3.06 1.386 0.992 Qe = 3.06Ce0.721

Table 4 Nonlinear fitting parameters and equations of the Redlich–Peterson model

Sample Average value of fitting parameters Equations

KR AR b r2

SiO2 3.43 49.69 0.635 0.953 Qe = 3.43Ce/(1 ? 49.69Ce0.635)

MPTMS/SiO2 4.53 50.40 0.602 0.995 Qe = 4.53Ce/(1 ? 50.40Ce0.602)

SiO2/PMAG(0.2 g) 18.34 53.09 0.645 0.996 Qe = 18.34Ce/(1 ? 53.09Ce0.645)

SiO2/PAG(0.2 g) 18.30 55.58 0.674 0.998 Qe = 18.30Ce/(1 ? 55.58Ce0.674)

pH 5, the weight of the adsorbent equals to 50 mg, sample volume = 10 ml, equilibrium time = 60 min

Treatment of biocide multifunctional materials

123

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