Does Particle Size of Clinoptilolite Zeolite Have a

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Jul 18, 2015 - Insight through. Differential Pore-Volume Distribution ... lite fractions [(250 µ (Z10; coarse)] has.

Communications in Soil Science and Plant Analysis

ISSN: 0010-3624 (Print) 1532-2416 (Online) Journal homepage: http://www.tandfonline.com/loi/lcss20

Does Particle Size of Clinoptilolite Zeolite Have a Role in Textural Properties? Insight through Differential Pore-Volume Distribution of Barret, Joyner, and Halenda Model K. Ramesh, K. Sammi Reddy, I. Rashmi, A. K. Biswas & K. R. Islam To cite this article: K. Ramesh, K. Sammi Reddy, I. Rashmi, A. K. Biswas & K. R. Islam (2015) Does Particle Size of Clinoptilolite Zeolite Have a Role in Textural Properties? Insight through Differential Pore-Volume Distribution of Barret, Joyner, and Halenda Model, Communications in Soil Science and Plant Analysis, 46:16, 2070-2078, DOI: 10.1080/00103624.2015.1069312 To link to this article: http://dx.doi.org/10.1080/00103624.2015.1069312

Accepted online: 18 Jul 2015.Published online: 18 Jul 2015.

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Date: 26 September 2015, At: 05:09

Communications in Soil Science and Plant Analysis, 46:2070–2078, 2015 Copyright © Taylor & Francis Group, LLC ISSN: 0010-3624 print / 1532-2416 online DOI: 10.1080/00103624.2015.1069312

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Does Particle Size of Clinoptilolite Zeolite Have a Role in Textural Properties? Insight through Differential Pore-Volume Distribution of Barret, Joyner, and Halenda Model K. RAMESH,1 K. SAMMI REDDY,2 I. RASHMI,1 A. K. BISWAS,1 AND K. R. ISLAM3 1

Division of Soil Chemistry and Fertility, ICAR-Indian Institute of Soil Science, Bhopal, India 2 Division of Resource Management, ICAR-Central Research Institute for Dryland Agriculture, Hyderabad, India 3 Soil and Bioeneregy, College of Food, Agricultural and Environmental Sciences, Ohio State University, South Centers, Piketon, Ohio, USA Analysis of differential pore-volume distribution (PVD) patterns of commercial clinoptilolite fractions [(250 µ (Z10; coarse)] has been conducted experimentally using an analyzer to measure the nitrogen (N2) adsorption isotherms. The differential PVDs of the clinoptilolite fractions were calculated from the hysteresis loop according to the adsorption and desorption curves of the Barret, Joyner, and Halenda (BJH) model. The adsorption and desorption cycles of BJH produced heterogeneous as well as dissimilar differential PVD patterns with assorted peaks. While the adsorption curve has prolonged up to 300 nm, the desorption cycle was confined up to 190-nm pore diameter only. In the adsorption cycle, all the clinoptilolite fractions displayed U-shaped curves and had a differential pore volume in the range of 3 × 10–3 to 8 × 10–3 cm3/g A° in the micropore region with a sole peak at 1.75 nm for the fine fraction (Z8). In contrast, the curves were linear in the mesoporous region for all the fractions, with the fine fraction (Z8) having the greatest differential pore volume, whereas the other two fractions were almost parallel to each other. The desorption cycle has revealed an inverted V-shape curve with no definite patterns for the microporous region. Although the adsorption cycle could ascertain the micropore region, the desorption cycle was unable to do so. It was apparent from the differential PVD of the BJH model that fraction size has a major role in determining the textural properties of clinoptilolite fractions. Keywords Adsorption, desorption, mesopores, micropores, texture

Introduction Zeolites (clinoptilolites) are crystalline hydrated aluminosilicates known to have surface chemical properties analogous to clays but which display superior hydraulic properties (Sullivan, Hunter, and Bowman 1997) and are selective exchangers for the ammonium cations Received 23 January 2015; accepted 6 April 2015. Address correspondence to K. Ramesh, Indian Institute of Soil Science (ICAR), Nabibagh, Berasia Road, Bhopal 462038, Madhya Pradesh, India. E-mail: [email protected] Color versions of one or more of the figures in the article can be found online at www. tandfonline.com/lcss.

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Texture of a Natural Zeolite

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(Blanchard, Maunaye, and Martin 1984; Dyer and White 1999) with broad applications in agriculture (Ramesh, Biswas and Patra, 2015) and agricultural engineering (Panpranot, Toophorm, and Praserthdam 2005). Zeolite-based systems have been advocated as potential solutions to a wide range of issues. Because the cavity structure of the zeolite mainly consists of mesomacropores (lower specific surface area), it is expedient for ion exchange as the diffusion resistance within the pore is reduced (Wen et al. 2006). Clinoptilolite is one such zeolite that has a rigid three-dimensional lattice with 10−9 m tunnels and an affinity for ammonium (NH+4) on its internal exchange sites (Ferguson and Pepper 1987). The commercial clinoptilolite is largely produced in two particle sizes by St Cloud Mining Co. (USA). The 20-mesh (Zeobrite) and 30-mesh (Clino 1) zeolites are commercially used to diminish the toxicity of aflatoxin in broiler chicken (Harvey et al. 1993). Ion-exchange properties of zeolites have long been documented for plant nutrition due to their high cation-exchange capacity (Ramesh et al. 2010). Although smaller particles of zeolites were often found to be more active, they are expected to be less stable and there is difficulty in handling them in the field (Ramesh et al. 2011). A 200-mesh particle size of clinoptilolite was used for an uranium adsorption study (Kilincarslan and Akyil 2005). The underlying and undeniable merit of science is that we now possess the tools not only to know the reason why porous materials are so useful but also to control their porous texture to make materials with on-demand porosity and properties (Murcia 2013). Perceptibly, the large-scale use of zeolites is not suitable to use without the detailed study of their pore-volume distribution (PVD) patterns, especially in regards to the particle size used in agriculture. Clinoptilolite is an important zeolite whose kinetics of ion adsorption was greatly affected by particle size (Langwaldt 2008). Notwithstanding this fact, Kesraoui-Ouki, Cheeseman, and Perry (1993) and Park et al. (2002) could not find any significant effects of particle size on ionexchange properties. Likewise, Nguyen and Tanner (1998) also have reported comparable surface area for coarse clinoptilolite and fine clinoptilolite. However, Inglezakis et al. (1999) observed that the effective diffusion coefficients of ion-exchange process were depended strongly on particle size of clinoptilolite. The compressive strength and sorptivity coefficient of hydrated clinoptilolite with calcium hydroxide were reportedly dependent on particle size, and reducing the particle size significantly reduced the sorptivity but increased the wateraccessible porosity (Ortega et al. 2000). Though limited study on fraction size has been carried out elsewhere in the world, the effect of particle size on the PVD in connection with textural properties has not been studied in depth. The objective of the present work was to investigate the effects of different particle sizes of zeolite on differential PVD using the Barret, Joyner, and Halenda (BJH) model and to compare the adsorption and desorption cycles.

Materials and Methods Clinoptilolite was collected from St. Cloud Mining Co., New Mexico, USA. The commercial material was divided into three physical fractions using mechanical sieves [fraction 1, 250 µ (Z10)]. Each fraction was washed with distilled deionized water to remove extraneous materials and was air dried at room temperature for 48 h. Pore-Volume Distribution Measurements Gas absorption (N2) has been useful to measure pore volume and its distribution of powdery samples. Before the measurements, all samples were degassed overnight at 573 K. The relation between relative pressure p/p° (where p and p° denote the equilibrium and

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saturation pressures of N2, respectively) and sizes of the relative pores were derived, and the isotherms were transformed into a relation between the volume adsorbed of N2 and pore size.

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Barret, Joyner, and Halenda Model An array of computational procedures has been proposed by various authors to calculate the pore size distribution (PSD) from the N2 adsorption data (Ramesh et al. 2014a, 2014b). In the evaluation of the PSD, it is assumed that the pores are cylindrical (4 V/A) in shape and capillary condensation occurs in the pores according to the Kelvin equation (Evans, Marconi, and Tarazona 1986). A modified Kelvin equation was used in the Barrett-JoynerHalenda model for this calculation (Barrett, Joyner, and Halenda 1951), with pore radii ranging between 17 and 300 A°. The method suggests that the desorption process involves the removal of capillary condensate alone and that the following step involves both the removal of condensate (i.e., vaporization) and the thinning of the adsorbed multilayer in the larger pores. The differential pore volume of BJH adsorption and desorption models were calculated by the ASAP 2020 analyzer’s built-in software. Meso- and Micro- Pore-Volume Distribution (MMPVD) The characterization of pore size / volume distribution will provide quantitative and detailed information about the pore structure of the zeolite samples. An important aim of the porosity analysis is the determination of the pore size and/or volume distribution of the clinoptilolite sample (Ramesh et al. 2015), and the wide particle-size distribution of the commercially available natural zeolite products indicates the necessity for further classification (Langwaldt 2008). Prior to application in any process, the pore-volume distribution of clinoptilolite fractions assumed paramount significance. It is known that two equal pore-volume increments at two pore radii are not associated with same numbers of pores, even if the radius difference is only small. Hence, a detailed knowledge of the differential pore-volume distribution pattern for different fractions was attempted. The sizes of the pores can influence the order and the energy of activation of the catalytic reaction and so it is important to know how the total pore volumes are distributed in pores of different sizes, which is important for catalytic reactions. The PVD over pore diameter is expressed in terms of the distribution function f (v): f ðvÞ ¼  ðdV=d log DÞ (Jena and Gupta 2003) where V is pore volume. The function is such that area under the function in any pore diameter range yields volume of pores in that range. The PVD has been expressed in terms of cumulative, differential, and incremental pore volumes. According to the PSD curves of the BJH adsorption and the differential curves of the PSD, the pore diameter sizes are mainly in the 2- to 50-nm diameter range.

Results and Discussion Adsorption Cycle Curve The differential curves of the pore size distribution in the process of the BJH adsorption are presented in Figure 1. The distribution curve was extended up to 300-nm pore diameter. In the adsorption cycle, all the fractions obeyed U-shaped curves and had a

Texture of a Natural Zeolite Z9

Z10

0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0

0

50

100

150 200 Pore diamater (nm)

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300

Figure 1. Differential pore-volume distribution patterns of clinoptilolite fractions by BJH model (adsorption).

Z8

dV/dlog(D) Pore Volume (cm3/g·Å)

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dV/dlog(D) Pore Volume (cm3/g·Å)

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Z9

Z10

0.008 0.007 0.006 0.005 0.004 0.003 1.7

1.75

1.8 1.85 1.9 Pore diamater (nm)

1.95

2

Figure 2. Differential pore-volume distribution patterns (micropore region) of clinoptilolite fractions by BJH model (adsorption).

differential pore volume in the range of 3 × 10–3 to 8 × 10–3 cm3/g A° in the micropore region with a single peak at 1.75 nm for the fine fraction (Z8) (Figure 2). Figure 3 showed that the larger proportion of total volume was the specific volume of the pores in the range 2- to 7-nm diameter, and the curves were close to a linear line after 10-nm pore width. The test data has also shown that the pore volume in the 2- to 22-nm diameter range has maximum data points in the total pore volume in all the fractions. According to the International Union of Pure and Applied Chemistry (IUPAC), the pores are divided into macropores (>50 nm), mesopores (2–50 nm), and micropores (

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