Effect of low frequency ultrasound on the surface properties of natural aluminosilicates

Ultrasonics Sonochemistry 31 (2016) 598–609

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Effect of low frequency ultrasound on the surface properties of natural aluminosilicates Liudmila Novikova a,⇑, Philippe Ayrault b, Claude Fontaine b, Gregory Chatel b,⇑, François Jérôme b, Larisa Belchinskaya a a b

Voronezh State University of Forestry and Technologies, 8 Timiryazeva Str., 394087 Voronezh, Russian Federation Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP, UMR CNRS 7285), Université de Poitiers, 1, Rue Marcel Doré, TSA 41105, 86073 Poitiers Cedex 9, France

a r t i c l e

i n f o

a b s t r a c t

Article history: Received 12 November 2015 Received in revised form 31 January 2016 Accepted 9 February 2016 Available online 10 February 2016

Structural and surface properties of different natural aluminosilicates (layered, chain and framework structural types) exposed of 20 kHz ultrasound irradiation (0–120 min) in aqueous and 35 wt%. aqueous H2O2 dispersions were studied by X-ray diffraction (XRD), dynamic light scattering (DLS), nitrogen adsorption–desorption, thermal analysis, and Fourier transform infrared spectroscopy (FTIR) techniques. It was confirmed that sonication caused slight changes in the structure of investigated minerals whereas their textural properties were significantly affected. The aqueous dispersions of montmorillonite (Mt), clinoptilolite (Zlt), glauconite (Glt) and palygorskite (Pal) were represented by several particles size fractions according to DLS-study. Ultrasound irradiation produced a decrease of the average particle diameter by 4–6 times in water and by 1.3–5 times in H2O2 dispersions except for Pal, which underwent strong agglomeration. A significant increase of total pore volume and pore diameter was observed for Glt sonicated in H2O2 dispersions whereas for Pal mainly micropore volume sharply increased in both aqueous and H2O2 dispersions. Ó 2016 Elsevier B.V. All rights reserved.

Keywords: Natural aluminosilicates Ultrasound Dispersions Hydrogen peroxide Decrease of particles size Surface and structural characteristics

1. Introduction Currently it is required from a chemical production processes to be as much as possible safe to the natural environment. For that, the ‘‘green chemicals”, i.e. those having less toxic effect on the environment, and the ‘‘eco-technologies” are being actively developed. Natural aluminosilicates can contribute to the ‘‘eco-friendly chemical processes” as they are widespread materials of natural origin, possessing various surface active sites, e.g. hydroxyls, exchangeable and structural cations, as well as micro- and mesoporous structure that allows their application in ion-exchange, adsorption and catalytic processes [1]. Another environmental measure for intensification of technological/chemical processes getting an increasing interest during the past few decades is the use of ultrasound [2–4]. Indeed, ultrasound irradiation of materials can lead to disaggregation and deagglomeration of particles, improve dispersing and emulsification effects in various phases, as well as activates chemical reactions

⇑ Corresponding authors. E-mail addresses: [email protected] univ-poitiers.fr (G. Chatel).

(L.

http://dx.doi.org/10.1016/j.ultsonch.2016.02.014 1350-4177/Ó 2016 Elsevier B.V. All rights reserved.

Novikova),

gregory.chatel@

by improving the mass transfer, prevent sedimentation and coagulation, and cause running of cavitation driven reactions [5]. In case of aluminosilicates, low frequencies ultrasonic irradiation significantly shortens the time of nucleation and synthesis [6–8], enhances accessibility of internal pores of aluminosilicates, reduces time of adsorption equilibrium [9,10] as well as intensifies the intercalation processes [11,12], etc. Besides, short ultrasound irradiation is usually applied during purification of natural clay samples as promoting deagglomeration of clay minerals phases and non-clay admixtures [13,14]. Sometimes, a combined use of clays and ultrasonic irradiation may have a synergetic effect on reaction time and yield of products in several catalytic organic reactions [4,15,16]. However, depending on the choice of ultrasonic parameters (power, frequency, irradiation time, etc), the nature of a solvent or an electrolyte present in dispersion and the type of the structure of aluminosilicate itself, sonication may severely affect properties [17,18] and behavior of aluminosilicate dispersions [19–21]. Detailed investigations of aqueous dispersions of montmorillonite, palygorskite and kaolinite under ultrasound irradiation [22,23] observed that short sonication times (<7.5 min at 19.5 kHz) breaks natural aggregates of clay minerals enhancing their dispersing and increasing stability of suspensions due to

L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609

formation of a new coagulation structure with an increased surface energy [22]. As a result, viscosity and n-potential of dispersions increased [23,24]. The longer sonication of clay suspensions lead to enlargement of particles (autocoagulation) due to their strong interaction. In some cases, particles with high surface energy complete the structure so that further ultrasound irradiation cannot destroy them. The crystal structure of particles continues improving that may lead to formation of a new phase, such as montmorillonite arising by sonication (>7 min) of palygorskite suspensions [22]. Aqueous dispersions of kaolinite, hydromica and montmorillonite mainly disaggregate [25] and undergo more slight changes of crystal structure. Applying the ultrasound treatment for 40–100 h in aqueous or acid (1 M HCl) media, it is possible to reach severe delamination of minerals (talc), reduce plate diameters in lateral dimensions and sharply abate the degree of crystallinity, especially in acid media where magnesium is easily leached [26]. Nevertheless, despite the increased spreading of ultrasound treatment in processes with clay minerals and aluminosilicates, there is no uniform procedure for the treatment, including type of equipment applied, ultrasonic parameters, duration of irradiation and other experimental conditions [4]. As a consequence, the data on ultrasound effect on physico-chemical properties of aluminosilicates are rather scattered, not systematic, that makes them difficult to generalize trends and reproduce the results. The present research was aimed at studying the effect of ultrasound treatment of aqueous and hydrogen peroxide (H2O2) dispersions on structural and physical–chemical properties of natural aluminosilicates. The data obtained by applying XRD, DLS, nitrogen adsorption, TGA, FTIR techniques allow comparing the stability of the aluminosilicates towards ultrasonic treatment (20 kHz) in aqueous media and in the presence of aqueous H2O2 considered as a benign oxidant. Indeed, we reported in our recent review on the combination between clay science and sonochemistry that aqueous oxidants should be used in these conditions, to develop clay-based catalyst materials to be applied in oxidation reactions involving H2O2 [4]. Some studies are performed in our laboratories to investigate the catalytic activity, but the goal of the current paper is to characterize the effects of ultrasound on clay structures and composition, in these aqueous oxidative conditions, to further better understand the reactivity and chemical mechanisms.

2. Materials and methods As objects of investigation were chosen natural samples, containing aluminosilicates of varied structural types and belonging to different classes of minerals, i.e. clay minerals – (i) layered 2:1 mineral montmorillonite, 90% (Mt), deposit from Voronezh region, Russia; (ii) spherulite type mixed layered mineral glauconite (Glt) [27], collected on the area of Voronezh anticline, Russia [28]; (iii) chain-layered type mineral palygorskite (Pal) from S&B Industrial Minerals Gmbh; and natural zeolite clinoptilolite (Zlt), Slovak deposit, with a hard-sphere framework structure. Part of the natural Mt-containing sample was fractionated (<2 lm) by sedimentation in osmosed water, converted to Ca-form and further used as a reference material (MtCa). The rest aluminosilicates were used asreceived, being crushed and sieved into particle size fraction of less than 250 lm. 1 wt.% dispersions of the clay samples in deionized water (w) or in aqueous 35 wt.% H2O2 (hp) solution were exposed of ultrasound (US) for 60 and 120 min using a Digital SonifierÒ S-250D from Branson (power of standby P0 = 27.0 W, nominal electric power of the generator Pelec = 8.2 W). A 3.2 mm diameter tapered microtip probe operating at a frequency of 19.95 kHz was used and its

599

acoustic power in water (Pacous.vol = 0.25 W mL 1) was determined by calorimetry using a procedure described in the literature [29]. Energy consumption was measured with a wattmeter (PerelÒ). The solvent and clay samples were inserted in a glass rounded cylindrical reactor (17 mm in interior diameter, 102 mm in height), thermostated at 19 °C using a MinichillerÒ cooler (Huber). In these rigorous conditions (same equipment, same ultrasonic parameters, and same amounts for treated samples), all the experiments are reproducible with exactly the same effects and results on irradiated clays. Physical–chemical properties of natural and US-treated clay samples were studied by following methods: XRD, dynamic light scattering (DLS); nitrogen adsorption–desorption; DTA/TGA; FTIR. XRD analysis. Materials were characterized with PANalytical XpertPro equipment using Cu radiation source (40 kV, 40 mA) and Xccelerator detector allowing a cumulative count on 2°2h range. Analytical conditions were recording ranges (2–65°2h and 2–35°2h) and equivalent counting times (0.017°2h/0.75 s and 0.033°2h/1.5 s) for powder and oriented preparations respectively. Particle size measurements. Suspensions of clay minerals aggregates (1%) in pure water or in 35 wt.% H2O2 solutions were employed. DLS method was applied for measuring the size of clay mineral aggregates using a Zetasizer Nano Malvern Instrument. 1.5 mL of suspensions before and after a definite time of US irradiation (0–120 min) were placed into a polystyrene cell and PSZ was measured using a red laser (k = 632.8 nm). Nitrogen adsorption measurements. N2 adsorption–desorption isotherms at 196 °C were studied using a TRISTAR 300 gas adsorption system for samples of investigated aluminosilicates in natural form and after exposure of US in aqueous and hydrogen peroxide media. Outgassing conditions included 2 h at 90 °C followed by 8 h at 250 °C. BET-method was applied for calculation of specific surface area (SSA); BJH method for mesopores volume, and t-plot analysis were used for assessment of micropores volume. Thermal analysis. The sample were characterized by thermogravimetric analyses (DTA/TGA) using a Q600 TA Instrument, under a dry air flow (100 mL/min, 10 °C/min) FTIR-measurements of aluminosilicates samples in natural and US-treated form were carried out on Nicolet MAGNA-IR 760 spectrometer E.S.P. equipped with an IR source, DTGS detector and KBr Beam splitter. The KBr pressed-disc technique was used for preparing a solid sample. Samples of 0.5 mg were dispersed in 100 mg of KBr to record spectra within the 4000–400 cm 1 transmission range. Discs were kept overnight in an oven at 150 °C to prevent water adsorption.

3. Results and discussion 3.1. XRD characterization of aluminosilicates samples before and after ultrasound irradiation 3.1.1. Mineralogical characterization of natural aluminosilicates samples The XRD-patterns obtained for powder samples of investigated natural aluminosilicates are represented in Fig. 1. As follows from XRD-pattern of Mt sample, it was essentially composed of a dioctahedral smectite of montmorillonite–beidellite series with (0 0 1) and (0 6 0) reflections located at 15.1 Å and 1.49 Å (Fig. 1). This clay mineral is associated with quartz and very little amounts of illite, kaolinite, chlorite and plagioclase. For MtCa sample prepared by sedimentation of <2 lm fraction, a relatively slight decrease in quartz content and a disappearance of chlorite and plagioclase reflections were observed (Fig. S1, ESI).

L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609

5000 Glt 0 2

6

10

14

18

22

26

30

34

38

42

46

- 1.54 Å Q - 1.49 Å S

- 1.70 Å S- 1.67 Å Q - 1.66 Å Q

- 1.51 Å Ca - 1.50 Å Pa - 1.49 Å Sp

- 1.82 Å Q

50

54

- 1.50 Å I+S

- 15.5 Å S

10000 Atp

- 1.71 Å S - 1.66 Å Q+I

15000

- 10.0 Å I

- 15.8 Å S - 11.89 Å Sp - 10.54 Å Pa

20000 Zlt

- 1,82 Å Z

25000

- 1.87 Å Sp+Ca - 1.82 Å Q

Relave intensity (a.u.)

Mtm 30000

- 1.82 Å Q

35000

- 12.4 Å Z - 9.99 Å I - 9.99 Å I - 8,99 Å Z - 7,93 Å Z - 7.14 Å K - 6,65 Å Z - 6,78 Å Z - 6.47 Å Pa - 5,94 Å Z - 5.40 Å Pa - 5,25 Å -Z 5,12 Å Z - 5.07 Å I+S - 5.01 Å S - 5,00 Å S - 4,66 Å Z - 4.53 Å I+S - 4.48 Å S+K - 4.48 Å CM 4,35 Å Z - 4.38 Å S - 4.26 Å Q - 4.14 Å Pa- 4.26 Å Q - 4,04 Å C 3,97 Å Z - 3,90 Å Z 3.74 Å P 3,77 Å Z 3.70 Å Pa - 3.68 Å I - 3.57 Å K - 3,56 Å Z - 3.46 Å P - 3,47 Å Z - 3.34 Å Q - 3.34 Å Q - 3,32 Å Z - 3.25 Å F - 3.20 Å S+P - 3.20 Å P - 3,19 Å Z 3.19 Å Pa+Sp - 3.08 Å I+S - 3,07 Å Z - 3.03 Å Ca - 3.08 Å S - 2,98 Å Z - 2.89 Å Do - 2,80 Å Z - 2.69 Å Pa - 2,73 Å Z - 2,68 Å Z - 2,58 Å I+S - 2.57 Å CM - 2.55 Å S+K - 2,53 Å Z - 2.45 Å Q - 2.45 Å Q - 2,44 Å Z - 2.40 Å I - 2,35 Å Z 2.28 Å Q - 2.28 Å Q+Ca - 2.27 Å Q+I - 2.24 Å Q - 2.24 Å Q - 2.13 Å Q - 2.13 Å Q+Sp - 2,12 Å Z - 2,02 Å Z - 1.98 Å Q - 1.98 Å Q - 1,96 Å Z

40000

- 1,69 Å Z

45000

- 3.34 Å Q

- 15.1 Å S

50000

- 1.67 Å Q

600

58

62

Cu Kα (°2θ) Fig. 1. Powder diffractogram patterns of natural aluminosilicate samples (CM: Undifferentiated clay minerals; Ca: Calcite; Ch: Mineral of chlorite-group; Do: Dolomite; F: K-Feldspar; I: Illite; K: Kaolinite; P: Plagioclase; Pa: Palygorskite; Q: Quartz; Sm: Mineral of smectite-group; Sp: Sépiolite; Z: Zeolite of heulandite–clinoptilolite series).

Glt sample was a mixture of illitic mineral and smectite phase associated with traces of quartz. These two clay minerals gave broad (0 0 1) reflections indicative of their poor crystalline organization. After swelling treatment by ethylene glycol (Fig. S2 in ESI), the very low value of intensity peak ratio between I(002) and I(001) of illitic phase was indicative of glauconite member [30]. Pal raw material was a complex mixture of clay minerals (Fig. 1), in which two main fibrous species, sepiolite (11.9 Å) and palygorskite (10.5 Å), were the dominant phases. The third important phase was dioctahedral smectite species (15.8 Å). These clay minerals were associated with quartz (3.34 Å) and low amount of calcite (3.03 Å). An oriented preparation realized with suspension of Pal sample after 30 min of sedimentation (Fig. 2) showed that fine fraction was largely enriched in smectite, while the ratio of the two fibrous species remained substantially unchanged. On the other hand, this modification revealed the presence of illite traces. The Zlt sample was essentially composed of a zeolite mineral, which belongs to the heulandite–clinoptilolite series, having its chemical composition varied between (Na, K)Ca4(Al9Si27O72)
24H2O – heulandite and (Na, K)6(Al6Si30O72)
20H2O – clinoptilolite. The 4.04 Å reflection was attributed to cristobalite (silica phase), which is frequently associated with zeolite minerals formed by alteration of volcanic ashes. Unfortunately, the other peaks of this mineral were totally or partially hidden by the numerous peaks of zeolite term. Thermal treatments showed that the lattice of this zeolite was stable over 550 °C. This behavior has been used to discriminate

between clinoptilolite, whose lattice is stable until 750 °C, and heulandites, destroyed after heating over 450 °C [31,32]. Consequently, it appeared that Zlt raw sample was mainly composed of a zeolite close to the heulandite end-member of the heulan dite–clinoptilolite series. Diffractogram of oriented samples prepared by glycolation (Fig. S4, ESI), observed very little amount of associated clay minerals (illite and some traces of smectite).

3.1.2. Effect of ultrasound irradiation of aqueous aluminosilicates dispersions on their XRD patterns To observe the effect of ultrasound irradiation of aqueous dispersions on the structural changes of the natural aluminosilicate samples, a comparison of diffractograms before and after treatment was realized. The powder diffractograms of Mt-w120us, Glt-w120us and Zltw120us samples irradiated by ultrasound for 120 min in aqueous dispersions (Fig. S5, ESI) observed very slight changes, likewise shown for raw bentonite sonicated in ethanol [56], and strongly resembled those for untreated ones from Fig. 1. For Mt-w120us (Fig. S5, ESI), smectite was observed as the most abundant clay mineral associated with significant quantity of quartz and trace amounts of other minerals. Oriented preparation of Mt-w120us (Fig. S6, ESI) realized after 1.5 h of sedimentation, found out a strong decrease of quartz amount and to a lesser extent of feldspar content, unlike was concluded for MtCa (Fig. S1, ESI). On the other hand, trace and little amounts of illite, kaolinite and chlorite have been detected.

601

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-

-

- 3,67 Å Pa

Q - 4.26 Å

- 4.48 Å CM

8,7 Å Sm

-

-

- 5.00 Å Sm+I

AD

14000

5.42 Å Pa

6.40 Å Pa

16000 - + Sp

12000

I

~

EG 10000

- 10,4 Å Sp - 10,02 Å - 9,86 Å Sm - 9,2 Å Pa

6000 350°C

4000

2000 550°C

- 4.8 Å Sm

8000

- 6,50 Å F

Intensity

18000

- 3.03 Å Ca

- 3,34 Å Q

20000

3.24 Å F+Pa - 3.20 Å Pa+Sp

-

-

22000

10.59 Å Pa

24000

-

26000

10.2 Å I

28000

11.99 Å Sp

17.4 Å Sm - 15;3 Å Sm

30000

0 2

6

10

14

18

22

26

30

Angular position (°2θ) Fig. 2. Diffractogram patterns of raw Pal sample under different treatments: air dried (AD), glycolated (EG), heated at 350 °C and 550 °C (CM: Undifferentiated clay minerals; Ca: Calcite; F: K-Feldspar; I: Illite; Pa: Palygorskite; Q: Quartz; Sm: Mineral of smectite-group, Sp: Sepiolite).

Applying the Scherrer formula [33], one may calculate the size of coherent domain scattering by using the full width at half maximum (FWHM) of the (0 0 1) of smectite and Biscaye index (v/p) [34]. Table 1 illustrates a slight decrease of these both parameters for Mt and Mt-w120us samples, testifying to a possibility of a slight modification of the stacks of the mineral particles under ultrasound irradiation through a reduction of the number of sheets composing them [36]. The only change of the powder diffractogram of Glt-w120us (Fig. S5, ESI) was the decrease of (0 0 1) intensity of smectite and correlatively of 4.53 Å reflection of all clay mineral species. The same was marked for XRD-patterns of oriented samples (Fig. S7, ESI), however, after heating at 550 °C the intensity of 10 Å reflection and I3.32 Å/I10.1 Å ratio were almost the same with or without sonication treatment. This, probably, indicate that sonication of smectite only induce a stack disorder without modifying the crystal lattice. Similarly, for other mica minerals, e.g. biotite and muscovite, the X-ray diffraction patterns had no changes before and after 10–100 h of sonication, except for broadening of the lines and changes in the relative intensities of diffractions. This was attributed to the delamination, crystallite size reduction and textural effects [45]. Table 1 Parameters of smectite crystallinity from powder diffractograms. Sample

FWHM, o2h

D, Å

Sheets, N

v, cts

p, cts

v/p

Mt Mt-w120us

0.804 0.904

220 196

15 13

7910 5754

8620 6792

0.92 0.85

The comparison between the powder diffractograms of Zlt raw before (Fig. 1) and after (Fig. S5, ESI) ultrasonic treatment show no evidence of modification. Oriented preparations (Fig. S8, ESI) showed an apparent increase of smectite content with the apparition of a strong peak at 10 Å after thermal treatment at 350 °C. Apparently, the main part of smectite was disordered and/or had a low crystallinity, therefore it was only possible to bring out their presence when the interlayer domain collapsed and, consequently, the degree of order in the stack increased. As opposed to Mt-w120us, Glt-w120us and Zlt-w120us samples, for which ultrasound treatment had very reduced effect, for Pal-w120us material the powder diffractogram significantly changed (Fig. 3). Comparing with Pal raw material, the majors reflections of palygorskite (10.5 Å), sepiolite (12.2 Å) and smectite (15 Å) have almost or completely disappeared. Quartz became the most important phase after sonication. This testified to an amorphisation of these minerals because their fibrous habitus was very sensitive to ultrasound treatment. The intensity of 4.47 Å reflection showed that clay mineral species were still relatively abundant, therefore, the presence of calcite and dolomite appeared more clearly. Diffractograms of oriented samples of Pal-w120us (Fig. 4) under various treatments still observed presence of fibrous clay phases (palygorskite and sepiolite) in fine fractions, however, the ratios of their peak intensities were completely modified with a sharp decrease in the intensity of specific peaks of palygorskite and sepiolite. This confirmed a decrease of the crystallinity of these minerals, especially palygorskite and sepiolite, and to a lesser extent of smectite.

602

L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609

18000

50

- 1.51 Å Ca - 1.50 Å Pa - 1.49 Å Sp

- 1.87 Å Sp+Ca - 1.82 Å Q

46

- 1.67 Å Q

- 1.98 Å Q - 1.98 Å Q

- 1.87 Å Ca - 1.82 Å Q

- 2.28 Å Q+Ca - 2.24 Å Q - 2.13 Å Q+Sp

- 2.57 Å CM - 2.45 Å Q

B

- 3.25 Å F - 3.19 Å Pa+Sp - 3.03 Å Ca - 2.89 Å Do - 2.69 Å Pa

10000

- 3.70 Å Pa

- 6.47 Å Pa

12000

- 5.40 Å Pa - 5,00 Å S - 4.48 Å CM - 4.26 Å Q - 4.14 Å Pa

- 15.8 Å S - 11.89 Å Sp - 10.54 Å Pa

14000

Relave intensity (a.u.)

- 3.34 Å Q

16000

2

6

10

14

18

22

26

30

38

42

- 1.51 Å Ca - 1.50 Å Pa

- 1.67 Å Q - 1.66 Å Q

- 2.61 Å Do? - 2.57 Å CM - 2.45 Å Q

34

- 2.28 Å Q+Ca - 2.24 Å Q - 2.13 Å Q

A 0

- 3.19 Å Pa- 3.25 Å F - 3.03 Å Ca - 2.89 Å Do

2000

- 6.47 Å Pa

- 10.54 Å Pa

4000

- 5.40 Å Pa - 5,00 Å S - 4.48 Å CM - 4.26 Å Q - 4.14 Å Pa

6000

- 3.70 Å Pa - 3.49 Å F

- 3.34 Å Q

8000

54

58

62

Cu Kα (°2θ) Fig. 3. Powder diffractogram patterns of natural Pal (B) and Pal-w120us (A) samples (CM: Undifferentiated clay minerals; Ca: Calcite; F: K-Feldspar; I: Illite; Pa: Palygorskite; Q: Quartz; Sm: Mineral of smectite-group; Sp: Sépiolite).

Thus, the XRD-characterization of powder and oriented samples testified to a more pronounced effect of ultrasound irradiation on the components of Pal material as compared with Mt, Glt and Zlt samples. In the next sections it is illustrated that ultrasound irradiation of aqueous and H2O2 dispersions significantly varied physical chemical properties of surface and particle size of investigated aluminosilicates. 3.2. DLS-characterization of aqueous and H2O2 dispersions of natural aluminosilicates in silent and ultrasonic irradiation conditions It is essential to distinguish between clay aggregates (an assembly of particles) and clay particles (an assembly of layers) present in dispersions, because according to recommendations of the International association for study of clays (AIPEA) and the Joint Nomenclature Committee (JNC), clay particles are those less 4 microns [1,35]. Dispersions of natural aluminosilicates in water and H2O2 aqueous solution described below satisfy this criterion and the term ‘‘particle” is used hereinafter. As was observed, the average particle diameters varied depending on the time of dispersing in silent conditions and under exposure of US (Table 2). Fig. 5(a–d) represents dependences of DLS-signal (I, intensity, %) and number of particles (N, %) on average particle diameter (d, nm) for Mt and Glt dispersions. According to Fig. 5a, in silent conditions it was possible to distinguish three fractions of particles in Mt water dispersions with

an average diameter of 295, 2305 and 5560 nm respectively. The larger aggregates are formed from stacks of finer clay particles, each of which consist from a number of layers [1]. Application of US irradiation to Mt dispersion (60 min) led to redistribution of size fractions of particles and caused a shift of I–d maxima to 142; 825 and 3580 nm, correspondingly. Further US irradiation time (120 min) brought to an overlapping of the peaks resolved at around 255 and 1281 nm. Similar trends were observed for Na-montmorillonite suspensions exposed of 100 min sonication in an ultrasonic bath or freeze-drying [36]. Comparing to freezedrying, the efficiency of sonication was much higher, resulting in a partial disintegration of the larger particles. Fig. 5b illustrates that the longer US-irradiation reduced the number of larger particles and enhanced that for smaller ones as a result of deagglomeration of clay particles and a reduction of the size of aggregates. Noteworthy, that within the short sonication times (0.25–4 min), variations in the ultrasound power from 100 W to 400 W observed, mainly, a reduction of the coarse particles size of montmorillonite dispersions, whereas the size of the fine particle fraction remained almost constant (180 nm) [25]. The ratio between the coarse and the fine particles fractions of montmorillonite changed to the advantage of the latter under longer and more powerful irradiation. An approaching to the exfoliation limit of the montmorillonite, i.e. its single layers or nanosheets, the width of around 180 nm according to AFM [25], was a possible reason for the achieved fine particle size of around 180 nm.

603

L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609

34000

Ca - 3.03 Å

- 3,32 Å I - 3,34 Å Q - 3.24 Å F+Pa

I

- 4.48 Å CM - 4.26 Å Q

AD 20000

18000

- 10,48 Å Pa+Sm

16000 14000 EG 12000

- 10.4 Å Sp - 9.7 Å Sm - 9.3 Å Pa

10000 8000 350°C 6000 4000

- 6.50 Å F

Intensity

22000

- 6.48 Å

- 17.3 Å Sm

24000

- 4.99 Å

26000

Pa

28000

- 12.15 Å Sp - 10,51 Å Pa - 9.98 Å I

- 15.8 Å Sm

30000

- 5.36 Å Pa

32000

550°C 2000

0 2

6

10

14

18

22

26

30

Angular position (°2θ) Fig. 4. Diffractogram patterns of Pal-w120us sample under different treatments: air dried (AD), glycolated (EG), and heated at 350 °C and 550 °C (CM: Undifferentiated clay minerals; Ca: Calcite; F: K-Feldspar; I: Illite; Pa: Palygorskite; Q: Quartz; Sm: Mineral of smectite-group, Sp: Sepiolite).

Table 2 Comparison of particle size of aluminosilicates samples after ultrasound irradiation in aqueous and aqueous H2O2 dispersions. Mineral

Mt

Solvent

Water H2O2

Glt

Water H2O2

Pal

Water H2O2

⁄

Conditions

Average particle size (d, nm)

Effect of US on dispersion of clay particles

Time of dispersing (min)

d0/d120

dw/dH2 O2 (silent, 120 min)

dw/dH2 O2 (US, 120 min)

0

60

120

Silent US Silent US

1768 1768 1184 1184

1634 774 961 891

1434 455 860 875

1.2 3.8 1.4 1.3

1.7

0.5

Silent US Silent US

1634 1634 2013 2013

497 402 626 485

478 368 638 452

3.4 4.4 3.1 4.4

0.7

0.8

Silent US Silent US

5023 5023 3108 3108

2550 4979⁄ 3430 11,690

–(⁄) –(⁄) 5025⁄⁄ 5741⁄⁄

1.9 *(60) 1.0⁄ 0.7 0.5

1.6

0.4

651 390 892 539

749 419 755 433

2.6 4.7 3.0 5.3

1.0

0.9

Increase of viscosity, agglomeration. Zlt Water Silent US H2O2 Silent US

⁄⁄

Large flakes 1985 1985 2284 2284

Note. d0/d120 – ratio of average particle diameters at zero and 120 min time of sonication; dw/dH2 O2 (silent) – ratio of average particle diameters in aqueous and H2O2 dispersions under silent conditions; dw/dH2 O2 (US) – ratio of average particle diameters in aqueous and H2O2 dispersions after ultrasound irradiation.

The dispersion of Glt represented a coarse suspension of large (>4 microns) fast settling granules (Fig. 5c) along with a fraction of smaller suspended particles having diameter of about 458 nm. After sonication for 60 and 120 min the intensity of the signal

decreased significantly, giving broader peaks at 295 and 458 nm, correspondingly. Fig. 5d confirmed increasing number of finer Glt particles by longer sonication time of dispersions, which finally became highly intransparent.

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L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609

a

N, %

I, %

b

16

35

14

30

12

25

10

20

8 15

6 10

4 5

2

0

0 10

100

1000

10000

10

d, nm

-2 Mt-w

c

100

1000 d, nm

-5

Mt-w60us

Mt-w120us

Mt-w

I, %

d

50

Mt-w60us

Mt-w120us

N, % 40 35

40 30 30

25 20

20

15 10 10 0 10

100

1000

10000 d, nm

5 0

-10

10 Glt-w

Glt-w60us

Glt-w120us

100

1000 d, nm

-5 Glt-w

Glt-w60us

Glt-w120us

Fig. 5. DLS-particle size distributions for Mt and Glt aqueous (w) and H2O2 (HP) dispersions in silent conditions and after us-irradiation for 60 and 120 min: a, c – intensity (I, %) vs. particle size (d, nm); b, d – number of particles (N, %) vs. particle size (d, nm).

In case of Zlt dispersions in silent conditions two size fractions of particles with an average diameter of 250 and 1040 nm were observed. After 60 min of US-irradiation the ratio between the finer and larger particles changed providing maxima at 300 and 2500 nm. Finally, three size fractions of particles at 180, 450 and 4000 nm were determined for 120 min of sonication time (Figs. S9 and S10 in ESI). In dispersions of Pal mainly one size fraction of agglomerates (2200 nm) was observed, having tendency to further agglomeration. The average particle diameter in Pal aqueous dispersions raised from 4500 nm at 60 min to 5000 nm at 120 min of USirradiation (Figs. S11 and S12 in ESI). Thus the apparent viscosity was observed to rise rapidly from 19.5 mPa s to 54 mPa s [37] due to ultrasonic cavitation caused shock waves and microjets resulted in intense collisions of aluminosilicate aggregates. Table 2 summarizes the average particle diameters of different aluminosilicates in aqueous and H2O2 dispersions under silent and US-irradiation conditions. As follows from Table 2, under silent conditions in the first period of dispersing the larger particles were observed for Pal and the smaller ones for Glt and Mt both in water and H2O2. Further dispersing both in aqueous and H2O2 media lead to a decrease in particle size (PS) for Glt and Zlt in 3 times; for Mt in 1.2–1.4 times, whereas for Pal strong agglomeration took place.

Under irradiation of US a stronger decrease in particle size was observed, namely, 4–6 times decrease in water dispersions, and 1.3–5 times lower particles in H2O2. Taking into account the ratio of particle diameters before and after 120 min of sonication (d0/d120), it seen that the rate of US exposure on the aluminosilicates particles changed in the order: Zlt > Glt > Mt for both aqueous and HP dispersions. This fact, obviously, testifies to different stability of the aluminosilicates particles under US. Less stable in aqueous and H2O2-dispersions were Zlt aggregates and particles, probably, due to cavitation effects arisen also from the inside of a developed system of zeolite channels. Moreover, similarly to acids, H2O2 strongly attacks aluminosilicates structure causing dealumination of the tetrahedral structural elements [38]. From the other hand, use of sonication during zeolites synthesis produces more agglomerated product made up of much finer crystallites [5]. It is remarkable that dw/dH2 O2 values were practically the same for Glt and Zlt under both silent and US conditions, whereas for Mt they differed significantly. Sonication of aqueous Mt dispersion gave 2 times smaller particles as in case of H2O2-dispersion, whereas under silent conditions Mt-aggregates had nearly 2 times higher diameter in aqueous dispersion as in H2O2 dispersions. Additionally, for all the cases of investigated aluminosilicates exposed of US, particle diameters in aqueous dispersions were

L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609

smaller than in H2O2, i.e. particles were finer in water as in H2O2. Nevertheless, the Pal dispersions in water and HP observed a stronger agglomeration of particles enhanced under sonication. This is typical for Pal mineral to form gel structures in different solutions by establishing a lattice structure of particles connected through hydrogen bonds [37]. Noteworthy, that after 120 min of ultrasound irradiation the dispersions of clay minerals samples (Mt, Pal, Glt) acquired a dark gray color, obviously, due to erosion of the titanium microtip probe of the sonifier. The elemental analysis confirmed contamination of the samples by titanium coming from the tip of the sonication probe [45]. 3.3. Nitrogen adsorption characterization of natural aluminosilicates exposed of ultrasound in aqueous and aqueous H2O2 dispersions Isotherms of N2 adsorption by investigated aluminosilicates in natural form and after sonication in aqueous and aqueous H2O2 solution dispersions are given in Fig. 6. Different shapes of the isotherms for natural form of the aluminosilicates were determined by the structural and morphological features of the investigated samples. Considering the IUPAC classification of the N2 adsorption/desorption isotherms, it is not possible to attribute the experimental isotherms to a single type due to a presence of both micro-, meso- and macropores in the samples. In general, the formation of hysteresis loops by the adsorption and desorption branches of the isotherms testifies to mesoporosity of the material and is attributed to the Type IV adsorption isotherm [39]. However, the absence of the plateau at higher P/P0 values in such isotherms is associated with the macropores of the material and is considered by Rouquerol et al. [40] as Type IIB isotherms. In the as-received form of the natural aluminosilicates the highest N2 adsorption volume at higher P/P0 was obtained for Pal sample changing in the order Zlt > Glt > Mt. The irradiation of the aluminosilicates by the US in aqueous dispersions shifted the N2 adsorption isotherms to the higher adsorption volumes, while the form of both the isotherms and the hysteresis loops kept unchanged. Treatment of aluminosilicates in the H2O2 solutions markedly influenced the isotherms and adsorption volume of Glt (Fig. 6c, d) and Mt (Fig. 6e) samples, whereas for Pal (Fig. 6a, b) and Zlt (Fig. 6f) samples it had a weaker effect. For the montmorillonite containing sample Mt, the form of the isotherms before and after US treatment both in water and HP dispersions changed, mainly, due to a broadening of the hysteresis loop between the adsorption and desorption isotherms. This was, obviously, resulted from the change of the interparticle porosity of the sample after sonication and corresponded to the data obtained for Na-montmorillonited irradiated by ultrasound in [36]. The form of the isotherms and the hysteresis loop were significantly different for Glt-samples treated in aqueous and HPdispersions. The pore volumes of Glt-w and Glt-w120us samples were rather low; a slow and gradual filling of the pore space by the adsorbed N2 molecules took place (Fig 6c). In case of Glt-hp and Glt-hp120us samples, a sharp increase of the adsorbed volume at high P/P0 of the isotherm was observed, testifying to a higher contribution of a certain size (macro) pores to adsorption of N2. The form of the hysteresis confirmed, obviously, the changes in the porosity (form and number of pores) of Glt-hp-samples, especially under irradiation of US. Additionally, an intensive decomposition of H2O2, providing numerous bubbles of oxygen visible, was characteristic for Glt-hp-samples, obviously, due to the higher Fecontent (ICP OES-data) for Glt-n sample (13.0%, ESI) comparing to Pal-n (2.6%) or Zlt-n (1.0%, [41]). Similar effect was observed for

605

raw vermiculite [42], for which chemical treatment with 30% H2O2 (6 h, 100 °C) lead to a sharp increase in its internal layer space, i.e. from 3.38–3.91 to 50.15–65.77 lm. For comparison, 6 h of treatment by 0.5 M HCl at 100 °C increased internal layer space of vermiculite only to 11–14 lm. Application of US caused an increase in the N2 adsorbed volume of Glt-w120us and Glt-hp120us samples and did not further change the form of the isotherms. Unlike the Mt and Glt sample, the Pal- and Zlt-containing samples did not observe any change in the shape of adsorption isotherms both before and after US-treatment in aqueous and HP-dispersions. The adsorbed volume of N2 increased equally for Pal-w120us and Pal-hp120us samples indicating at a similar effect of the US irradiation and the dispersing solution on the mineral structure. At the same, for Zlt-w120us sample, the adsorbed volume almost did not change or slightly increased for Zlt-hp120us as compared to Zlt samples under silent conditions. Surface characteristics of natural aluminosilicates samples before and after US-treatments calculated from adsorptionisotherms are represented in Table 3. It follows from Table 3 that exposure of US for 120 min caused variations in the surface characteristic of aluminosilicates depending on the solution media and the structural features of the mineral [43]. After US-irradiation, the values of SSA of the investigated samples enhanced in 1.1–1.6 times in both aqueous and H2O2 media. The total pore volumes did not significantly change after sonication, except for Glt, for which it was markedly increased along with the pore diameters values in H2O2 solutions. Besides, the strongest rise of the micropores volumes after exposure of ultrasound was revealed for Pal samples, particularly, in aqueous dispersions. According to the ratio of Sus/Snat (Table 3), the impact of ultrasound on the surface characteristics of the aluminosilicates samples declined in the order Glt > Pal > Zlt > Mt for ultrasound exposure in aqueous dispersions, and as Glt > Mt = Zlt > Pal for the ultrasound exposure in H2O2 dispersions. These orders do not entirely coincide with ones obtained for particle diameters ratio d0/d120 from the DLS-study of aqueous and H2O2 dispersion as the investigated systems (dispersions), the property and the experimental conditions are different. 3.4. Thermal analysis of aluminosilicates treated with ultrasound in aqueous and H2O2 dispersions Experimental data derived from the TG, DTG analysis of investigated aluminosilicates in natural form and after sonication are summarized in Table 4. Depending on the structural type of the aluminosilicate, there were one or several temperature regions observed which stand for the processes of dehydration or dehydroxylation [44]. Noteworthy, the significant changes in thermal behavior of the solids [59] can be caused by their particle size distribution. Thus, particle size reduction produced by sonication facilitated the dehydroxylation of minerals [44,45] and, obviously caused slight changes of the DTG-profiles of investigated samples by shifting the temperature peaks to lower values after ultrasound treatment. For Mt-sample the DTG-curves comprised two regions where temperature peaks appeared. Low temperature peaks (L.T.P.) (85 °C, 145 °C) was caused by dehydration of loosely bound water of adsorption (85 °C) and from the interlayer space (145 °C) [47,48]. Additionally, the first endothermic peak was doubled in case of 2+-interlayer cation [49]. The T-peak at 664 °C was due to dehydroxylation process. US-treatment of Mt caused a shift of LTP on 15–30 °C to lower temperature region as well as a decrease of the first intensities. T2-peaks of Mt-w120us and MT-hp120us weakened and became the shoulders of the T1-peaks. The stronger

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L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609

a

VN2, cm3/g

b

350

VN2, cm3/g 400

300

350 300

250

250

200

200 150 150 100

100

50

50 0

0 0

0.2

0.4

0.6

Pal-ads Pal-w120us-ads

c

0.8

1

0

0.2

0.4

0.6

0.8

1

P/P0

Pal-des Pal-w120us-des

VN2, cm3/g

d

0

Pal-HP-ads

Pal-HP-des

Pal-hp120us-ads

Pal-hp120us-des

VN2, cm3/g

100

200

90

180

80

160

70

140

60

120

50

100

40

80

30

60

20

40

10

20

0

0

0

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1 P/P0

P/P0 Glt-ads Glt-w120us-ads

e

P/P

Glt-des Glt-w120us-des

VN2, cm3/g

f

80

Glt-HP-ads

Glt-HP-des

Glt-HP120us-ads

Glt-HP120us-des

VN2, cm3/g 80

70

70

60

60

50

50

40

40

30

30

20

20

10

10 0

0

0

0.2 MtCa-ads MtCa-w120us-ads MtCa-hp120-ads

0.4

0.6

0.8 MtCa-des MtCa-w120us-des MtCa-hp120us-des

0

1 P/P0

0.2 Zlt-hp-ads Zlt-hp120us-ads Zlt-ads

0.4

0.6

0.8

1

Zlt-hp-des Zlt-hp120us-des Zlt-des

P/P0

Fig. 6. BET isotherms of N2 adsorption/desorption on natural aluminosilicates samples before and after 120 min of ultrasound irradiation (120us) in water (w) and H2O2 (hp) dispersions: a, b – Pal; c, d – Glt; e – MtCa; f – Zlt.

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L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609 Table 3 Surface characteristics of aluminosilicates samples treated with ultrasound (120 min) in water and H2O2 dispersions. Mineral

Solvent

Specific surface area, m2/g Snat

Sus/Snat

Total pore volume, cm3/g

Sus

Vnat

Vus

Vus/Vnat

Micro pores volume, cm3/g Vmicro nat

Vmicro us

/Vmicro Vmicro us nat

Pore diameter, A (BJH-des)

Dus/Dnat

Dnat

Dus

Mt

Water H2O2

23

26 31

1.1 1.3

0.052

0.049 0.065

0.9 1.2

0.004

0.005 0.005

1.2 1.2

104

78 75

0.8 0.7

Glt

Water H2O2

39

61 54

1.6 1.4

0.055

0.097 0.287

1.8 2.3

0.010

0.014 0.016

1.4 1.6

83

84 263

1.0 3.2

Pal

Water H2O2

113

166 121

1.5 1.1

0.385

0.356 0.347

0.9 0.9

0.003

0.023 0.008

7.7 2.7

160

157 177

1.0 1.1

Zlt

Water H2O2

23

28 30

1.2 1.3

0.107

0.059 0.112

0.5 1.1

n.f.

n.f. 0.009

– –

162

164 193

1.0 1.2

Note. Subscripts ‘‘nat” and ‘‘us” stand respectively for natural aluminosilicate and after 120 min of ultrasound irradiation.

Table 4 DTG and TGA-data for natural (Nat) aluminosilicates before and after ultrasound treatment (120 min) in water (w) and H2O2 (HP) dispersions. Temperature peak

1st

Sample

T1,°C

a

Mt-Nat Mt-w120us Mt-hp Mt-hp120us Glt-Nat Glt-w120us Glt-hp Glt-hp120us Pal-Nat Pal-w120us Pal-hp Pal-hp120us Zlt-Nat Zlt-w120us Zlt-hp Zlt-hp120us

86 71 62 56 65 57 53 48 62 n.o. 60 51 56 58 57 65

– 15 24 30 – 8 12 17

Note. aDTi = Ti(nat)

2nd

DT1

2 12 2 1 9

T2,°C 145 150 s.c 140 s. 134 s. 129 n.o. n.o. n.o. 94 81 84 78

3rd

DT 2 5 5 11 – – – – 13 10 16

4th

b

T3,°C

DT3

ML3,%

4.3 1.7 3.9 3.0 6.9 4.0 3.6 3.3 8.9 6.9 8.3 8.8 11.1 10.8 10.8 11.1

668 654 654 665 494 481 490 459 211 198 201 197

14 14 3 – 13 4 35 – 13 10 14

3.5 3.7 3.9 3.4 5.1 3.8 4.7 4.8 2.2 2.5 2.2 2.2

ML1,2%

T4°C

431 427 435 429

5th

DT 4

– 4 4 2

ML4,%

4.1 4.9 4.6 4.2

T5,°C

665 641 654 618

6th

DT5

24 11 47

T6,°C

860 706

ML5,6,%

1.9 1.7 1.41 0.64

Total ML,% 7.8 5.4 7.8 6.4 12.0 7.8 8.3 8.1 17.0 16.0 16.5 15.5 11.1 10.8 10.8 11.1

Ti(us); bML – mass loss (%); cs – shoulder on the peak.

effect of ultrasound on dehydration temperature observed for Mt-samples contacted to HP-solutions both in silent conditions and after US-irradiation. Dehydroxylation process of Mt-w120-us and Mt-hp, attributed to high temperature peaks (H.T.P.), occurred at slightly lower temperatures as for Mt-Nat and Mt-hp-us. As follows from Table 4, the total mass loss of Mt on TG-curves was lower after us-exposure in both aqueous and HP-dispersions than in the unsonicated state. Similar to montmorillonite, at the DTA curves of Glt exist peaks caused by desorption of adsorbed and interlayer water in the region of 200 °C. A peaks shoulder at 135 °C, obviously, testifies to desorption of water differently bound to the surface. Dehydroxylation of natural glauconite has a temperature maximum at 495 °C and usually occurs within 300–800 °C range [50]. After sonication the shoulder of the peak disappeared and elimination of the adsorbed water was at lower temperatures than both in aqueous (57 °C) and in H2O2 dispersions (48 °C), the latter caused a stronger shift of the peak temperature. In case of Pal-samples, the DTA-curves exhibit four characteristic regions in which endothermic processes occur, providing corresponding peaks. The first peak for Pal-Nat is doubled (62 °C and 94 °C) due to desorption of adsorbed water and partially water from the zeolites channels [20,51]. The second peak and a mass loss correspond to the total elimination of zeolitic water up to 210 °C, which can be reversibly absorbed again. The third peak with a maximum at 432 °C lies in the region of removal of the water coordinated to cations situated along octahedral sheets (crystallized water).

Dehydroxylation of Mg–OH groups by further increase of the temperature produces the fourth peak at 663 °C, where also a partial destruction of the crystal structure and decomposition of carbonates takes place. Ultrasound irradiation of Pal-samples caused 10–15 °C lower temperatures of dehydration according to the shifts of the 1st, 2nd, 3rd peaks; the 4th peak underwent almost no changes, whereas the 5th peak for dehydroxylation was markedly shifted (24–47 °C) to lower temperatures. Similarly, the stronger temperature shift was observed for samples treated by ultrasound in the presence of hydrogen peroxide. The TG curves of all clinoptilolite samples revealed a continuous mass loss during heating up to 1000 °C, providing the same total mass loss of 11%. The peak maxima observed on the DTG curves in the region below 100 °C correspond to the loss of adsorbed and loosely bonded water at higher temperatures. As a result of ultrasound exposure dehydration of Zlt occurred at slightly higher temperatures, especially for the case of Zlt-hp-us, comparing to natural Zlt. A stronger modification of thermal behavior of clay minerals can be reached applying the longer (5–100 h) sonication times [43,45,46]. This will lead to a significant increase in the mass loss at low temperature due to the loss of some outer hydroxyl groups and protonated hydroxyls, which appeared on the new surface generated by reduction of particles. Additionally, the original endothermic dehydroxylation effects markedly shift to lower temperatures depending on the mineral structure, e.g. by 9 °C for disordered kaolinite and by 184 °C for muscovite [43].

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3.5. FTIR-spectra characterization The FTIR-spectra of natural aluminosilicates samples Mt, Glt and Pal before and after ultrasound treatment in both aqueous and H2O2 dispersions were very similar since it is very difficult to distinguish by this method the changes caused by sonication. The same observations were obtained for raw bentonites [24], palygorskite [58] sonicated in water (30–120 min [24]; 1–4 h [57]) or ethanol (1–4 h [57]), and other minerals, testifying, thereby, to minor structural changes induced. Therefore, the assignments of the main absorption bands were only provided hereinafter for natural samples, while the full FTIR-spectra for each aluminosilicate samples before and after US-irradiation can be found in ESI (Figs. S13–S15 and Tables S1–S3) [52–56]. 4. Conclusion Ultrasound irradiation of aqueous and hydrogen peroxide dispersions of natural aluminosilicates samples significantly varied both dispersion properties and textural characteristics of aluminosilicates (specific surface area, total pore volume, micropore volume and pore diameters, and variation in thermal behavior). Finer aluminosilicates particles were produced by ultrasonic irradiation of aqueous dispersions, while the stronger modification of textural characteristics of aluminosilicate samples was observed after irradiation of their H2O2 dispersions. According to the ratio of average particle diameters before and after sonication, the effect of ultrasound irradiation on the dispersing ability of the aluminosilicate decreased in the order Zlt > Glt > Mt for aqueous and H2O2-dispersions. Obviously, the change of surface characteristics for montmorillonite and zeolite containing samples was, mainly, due to reduction of particle size under ultrasound irradiation, accompanied by slight variations of the total pore and micropore volumes and a minor decrease of pore diameter. Ultrasound exposure of aqueous dispersions of glauconite and palygorskite came to a sharp increase in pore diameter (glauconite in H2O2) or a significant growth of the proportion of micropores (palygorskite in aqueous dispersion) that caused the most noticeable changes in the texture of mineral particles as well as thermal behavior. Except for palygorskite, the XRD-patterns of powder and oriented aluminosilicate samples confirmed a relative stability of the mineral structure towards ultrasound exposure. Acknowledgement Dr. Liudmila Novikova would like to acknowledge the Coordinator of the IMACS project Mrs Patricia Patrier for affording a possibility to contribute to Erasmus Mundus IMACS program with a research project and a lecture course in Clay Science, and the University of Poitiers, France, for granting a financial support for the research stay. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.ultsonch.2016.02. 014. References [1] F. Bergaya, G. Lagaly, Handbook of Clay Science, second ed., Developments in Clay Science. 5. Elsevier, Amsterdam, 2013. [2] D. Chen, S.K. Sharma, A. Mudhoo, Handbook on Applications of Ultrasound: Sonochemistry for Sustainability, CRC Press, 2011.

[3] M. Nasrollahzadeh, A. Ehsani, A. Rostami-Vartouni, Ultrasound-promoted green approach for the synthesis of sulfonamides using natural, stable and reusable natrolite nanozeolite catalyst at room temperature, Ultrason. Sonochem. 21 (1) (2014) 275–282. [4] G. Chatel, L. Novikova, S. Petit, How efficiently combine sonochemistry and clay science?, Appl Clay Sci. 119 (2016) 193–201. [5] K.S. Suslick, Sonocatalysis, in: G. Ertl, H. Knozinger, J. Weitkamp (Eds.), Handbook of Heterogeneous Catalysis, vol. 3, Wiley-VCH, Weinheim, 1997, pp. 1350–1357. [6] Ö. Andaç, M. Tatlıer, A. Sirkeciog˘lu, I. Ece, A. Erdem-S ßenatalar, Effects of ultrasound on zeolite A synthesis, Microporous Mesoporous Mater. 79 (1–3) (2005) 225–233. [7] N. Kumar, O.V. Masloboischikova, L.M. Kustov, T. Heikkilä, T. Salmi, D.Yu. Murzin, Synthesis of Pt modified ZSM-5 and beta zeolite catalysts: influence of ultrasonic irradiation and preparation methods on physico-chemical and catalytic properties in pentane isomerization, Ultrason. Sonochem. 14 (2) (2007) 122–130. [8] A. Pérez, M.A. Centeno, J.A. Odriozola, R. Molina, S. Moreno, The effect of ultrasound in the synthesis of clays used as catalysts in oxidation reactions, Catal. Today 133–135 (2008) 526–529. [9] Z. Dankova, A. Mockovciakova, S. Dolinska, Influence of ultrasound irradiation on cadmium cations adsorption by montmorillonite, Desalin. Water Treat. 52 (28–30) (2014) 5462–5469. [10] Z. Danková, A. Mockovcˇiaková, M. Orolínová, Cd(II) adsorption by magnetic clay composite under the ultrasound irradiation, Energy Environ. Eng. 1 (2) (2013) 74–80. [11] Vasundhara Singh, Varinder Sapehiyia, Goverdhan Lal Kad, Ultrasound and microwave activated preparation of ZrO2-pillared clay composite: catalytic activity for selective, solventless acylation of 1, n-diols, J. Mol. Catal. A Chem. 210 (2004) 119–124. [12] M.J. Pérez-Zurita, G.J. Pérez-Quintana, A.J. Hasblady, A. Maldonado, C.U. De Navarro, A. De Abrisqueta, C.E. Scott, Synthesis of Al-PILC by ultrasound: reducing the intercalation time and the amount of synthesis water, Clays Clay Miner. 53 (5) (2005) 528–535. [13] G.D. Hoke, M.D. Schmitz, S.A. Bowring, An ultrasonic method for isolating nonclay components from clay-rich material, Geochem. Geophys. Geosyst. Techn. Brief 15 (2) (2014) 492–498. [14] F. Nieto, K.J.T. Livi, Minerals at the Nanoscale, Mineralogical Society of Great Britain and Ireland, 2013. [15] R.M. Martin-Aranda, E. Ortega-Cantero, M.L. Rojas-Cervantes, M.A. VicenteRodrigues, M.A. Banares-Munoz, Sonocatalysis and basic clays. Michael addition between imidazole and ethyl acrylate, Catal. Lett. 84 (3–4) (2002) 201–204. [16] J. Safari, L. Javadian, Montmorillonite K-10 as a catalyst in the synthesis of 5,5disubstituted hydantoins under ultrasound irradiation, J. Chem. Sci. 125 (5) (2013) 981–987. [17] J.L. Pérez-Rodríguez, F. Franco, V. Ramírez-Valle, L.A. Pérez-Maqueda, Modification of the thermal dehydroxylation of antigorite by ultrasound treatment, J. Therm. Anal. Calorim. 82 (2005) 769–774. [18] J. Poyato, J.L. Perez-Rodriguez, V. Ramirez-Valle, A. Lerf, F.E. Wagner, Sonication induced red-ox reactions of the Ojen (Andalucia, Spain) vermiculite, Ultrason. Sonochem. 16 (2009) 570–576. [19] Zˇ. Dohnalova, L. Svoboda, P. Šulcova, Characterization of kaolin dispersions using acoustic and electroacoustic spectroscopy, J. Min. Metal. Sect. B. 44 (2008) 63–72. [20] J. Xu, W. Wang, A. Wang, Effects of solvent treatment and high-pressure homogenization process on dispersion properties of palygorskite, Powder Technol. 235 (2013) 652–660. [21] F. Ali, L. Reinert, J.-M. Lévêque, L. Duclaux, F. Muller, Sh. Saeed, S. Sakhawat Shah, Effect of sonication conditions: solvent, time, temperature and reactor type on the preparation of micron sized vermiculite particles, Ultrason. Sonochem. 21 (3) (2013) 1002–1009. [22] N.N. Kruglitskii, V.Yu. Tretinnik, V.V. Simurov, Ultrasound in Chemical Technology, UkrNIINTI, Kiev, 1970. [23] N.N. Kruglitskii, Physico-chemical Mechanics of Dispersed Minerals, Naukova dumka, Kiev, 1970. [24] W.K. Mekhamer, The colloidal stability of raw bentonite deformed mechanically by ultrasound, J. Saudi Chem. Soc. 14 (2010) 301–306. [25] H. Li, Y. Zhao, S. Song, Y. Nahmad, Comparison of ultrasound treatment with mechanical shearing for montmorillonite exfoliation in aqueous solutions, J. Miner. 2 (1) (2015) 1–12. [26] N.H. Jamil, S. Palaniandy, Comparative study of water-based and acid-based sonications on structural changes of talc, Appl. Clay Sci. 51 (2011) 399–406. [27] L. Novikova, L. Belchinskaya, V. Krupskaya, F. Roessner, A. Zhabin, Effect of acid and alkaline treatment on physical–chemical properties of surface of natural glauconite, Sport. Chrom. Proc. 5 (2015) 730–740. [28] A.V. Zhabin, A.D. Savko, Glauconites of Voronezh Anticline, Ocherki po regionalnoi geologii, Nauka, Saratov, 2008. [29] S. Koda, T. Kimura, T. Sakamoto, T. Kondon, H. Mitome, A standard method to calibrate sonochemical efficiency of an individual reaction system, Ultrason. Sonochem. 10 (2003) 149–156. [30] D.M. Moore, R.C. Reynolds, X-Ray Diffraction and the Identification and Analysis of Clay Minerals, second ed., Oxford University Press, Oxford, 1997. [31] F.A. Mumpton, Clinoptilolite redefined, Am. Mineral. 45 (1960) 351–369.

L. Novikova et al. / Ultrasonics Sonochemistry 31 (2016) 598–609 [32] G. Gottardi, E. Galli, Natural Zeolites, in: P.J. Wyllie, W. von Engelhardt, T. Hahn (Eds.), Mineral and Rocks Series, vol. 18, Springer Verlag, Berlin, 1985. [33] G.W. Brindley, G. Brown, Crystal structures of clay minerals and their X-ray identification. Mineralogical Society Monograph N 3, Mineralogical Society, London, 1980. [34] P.E. Biscaye, Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and adjacent seas and oceans, Geol. Soc. Am. Bull. 76 (1965) 803–832. [35] S. Guggenheim, Definition of clay and clay mineral: joint report of the AIPEA nomenclature and CMS nomenclature committees, Clays Clay Miner. 43 (2) (1995) 255–256. [36] A. Pacuła, E. Bielan´ska, A. Gaweł, K. Bahranowski, E.M. Serwicka, Textural effects in powdered montmorillonite induced by freeze-drying and ultrasound pretreatment, Appl. Clay Sci. 32 (2006) 64–72. [37] F. Zhou, T. Li, Y. Yan, C. Cao, L. Zhou, Y. Liu, Enhanced viscosity of aqueous palygorskite suspensions through physical and chemical processing, Adv. Mater. Sci. Eng. 2015 (2015) 1–2, http://dx.doi.org/10.1155/2015/941580 (ID 941580). [38] M. Çanli, Y. Abali, A novel Turkish natural zeolite (clinoptilolite) treated with hydrogen peroxide for Ni2+ ions removal from aqueous solutions, Desalin. Water Treat. (2015) 1–11. [39] U. Kuila, M. Prasad, Specific surface area and pore-size distribution in clays and shales, Geophys. Prospect. 61 (2013) 341–362. [40] J. Rouquerol, F. Rouquerol, K.S.W. Sing, Adsorption by Powders and Porous Solids, Academic Press, 1998, ISBN 0080526012. [41] L.I. Belchinskaya, N.A. Khodosova, L.A. Bityutskaya, Adsorption of formaldehyde at mineral nanoporous sorbents exposed to a pulse magnetic field, Prot. Metal. Phys. Chem. Surf. 45 (2) (2009) 203–206. [42] F.S. Hashem, M.S. Amin, S.M.A. El-Gamal, Chemical activation of vermiculite to produce highly efficient material for Pb2+ and Cd2+ removal, Appl. Clay Sci. 115 (2015) 189–200. [43] J.L. Pérez-Rodríguez, J. Pascual, F. Franco, M.C. Jiménez de Haro, A. Duran, V. Ramírez del Valle, L.A. Pérez-Maqueda, The influence of ultrasound on the thermal behaviour of clay minerals, J. Eur. Ceram. Soc. 26 (2006) 747–753. [44] M. Földvári, Handbook of thermogravimetric system of minerals and its use in geological practice, Geological institute of Hungary, 2011. [45] F. Franco, L.A. Pérez-Maqueda, J.L. Pérez-Rodriguez, The influence of ultrasound on the thermal behaviour of a well ordered kaolinite, Thermochim. Acta 404 (2003) 71–79.

609

[46] L.A. Pérez-Maqueda, J.M. Blanesa, J. Pascual, J.L. Pérez-Rodrı´guez, The influence of sonication on the thermal behavior of muscovite and biotite, J. Eur. Ceram. Soc. 24 (2004) 2793–2801. [47] M. Fernndeza, M.D. Albab, R.M. Torres Sáncheza, Effects of thermal and mechanical treatments on montmorillonite homoionized with mono- and polyvalent cations: insight into the surface and structural changes, Colloids Surf. A 423 (2013) 1–10. [48] A.V. Ursu, G. Jinescu, F. Gros, I.D. Nistor, N.D. Miron, G. Lisa, M. Silion, G. Djelveh, A. Azzouz, Thermal and chemical stability of Romanian bentonite, J. Therm. Anal. Calorim. 106 (2011) 965–971. [49] V.S. Fajnor, K. Jesenak, Differential thermal analysis of montmorillonite, J. Therm. Anal. 46 (1996) 489–493. [50] V.A. Logvinenko, F. Paulik, I. Paulik, Kvasi Equilibrium Thermogravimetry in Modern Inorganic Chemistry, Nauka. Sib.otd, Novosibirsk, 1989. [51] L. Boudriche, R. Calvet, B. Hamdi, H. Balard, Surface properties evolution of attapulgite by IGC analysis as a function of thermal treatment, Colloids Surf. A. 399 (2012) 1–10. [52] J. Madejova, P. Komadel, Baseline studies of the clay minerals society source clays: infrared methods, Clays Clay Miner. 49 (5) (2001) 410–432. [53] J.L. Bishop, M.D. Lane, M.D. Dyar, A.J. Brown, Reflectance and emission spectroscopy study of four groups of phyllosilicates: smectites, kaoliniteserpentines, chlorites and micas, Clay Miner. 43 (2008) 35–54. [54] M. Honty, M. De Craen, Mineralogy of the Boom Clay in the Essen-1 borehole. RP.WD.0044 – DS 251–A43/2.12 SCKCEN ref.: KNT 90 01 1467.01, NIRAS/ ONDRAF ref.: CCHO 2004–2470/00/00. [55] G.A. Soberanis-Monforte, P.I. González-Chi, J.L. Gordillo-Rubio, Influence of chemically treated palygorskite over the rheological behavior of polypropylene nanocomposites, Ingeniería, Investigación y Tecnología 16 (4) (2015) 491–501. [56] B. Rhouta, E. Zatile, L. Bouna, O. Lakbita, F. Maury, et al., Comprehensive physicochemical study of dioctahedral palygorskite-rich clay from Marrakech High Atlas (Morocco), Phys. Chem. Miner., Springer Verlag 40 (5) (2013) 411– 424. [57] Z. Darvishi, A. Morsali, Synthesis and characterization of nano-bentonite by sonochemical method, Ultrson. Sonochem. 18 (2011) 238–242. [58] Z. Darvishi, A. Morsali, Sonochemical preparation of palygorskite nanoparticles, Appl. Clay Sci. 51 (2011) 51–53. [59] N. Koga, J.M. Criado, Kinetic analyses of solid-state reactions with a particlesize distribution, J. Am. Ceram. Soc. 81 (1998) 2901–2909.