Influence of different dry milling processes on the properties of an attapulgite clay, contribution of inverse gas chromatography

Abstract

The effect of dry milling processes on the surface properties of an attapulgite clay, also called palygorskite, was investigated by carrying out experiments with different types of grinding devices. Ground products were then characterized by size measurement, scanning electron microscopy, X-ray diffraction, adsorption-desorption of N 2 and inverse gas chromatography at infinite dilution (IGC-ID) as well as finite concentration conditions (IGC-FC). These analyses were performed to evaluate the changes in particle size distribution, morphology, crystallinity and surface properties of attapulgite powder, respectively. Among the tested dry grinding devices, grinding in an air jet mill (Alpine 50 AS) and a vibratory ball mill (Pulverisette 0) led to the most significant particle size reduction. SEM photomicrographs showed that a breakage of the fibrous structure took place during dry grinding. Moreover, long grinding in Pulverisette 0 resulted in the complete destruction of fibre morphology followed by agglomeration. XRD analysis showed that whatever the grinding process, the microstructure of the attapulgite was not affected. IGC confirmed that only grinding in Pulverisette 0 affected the surface properties notably. In this case, the most significant decreases were observed in the dispersive component of the surface energy (164 to 116 mJ/m 2) and in the specific surface area obtained with the octane probe (114.5 m 2 /g to 62.6 m 2 /g) by IGC-ID and IGC-FC, respectively. At the same time, a modification of the distribution functions of the adsorption energies (DFAE), giving information about surface heterogeneity, was noticed.

Removal of lead(II) from aqueous solution using modified palygorskite, contribution of inverse gas chromatography

“…This parameter indicates the ability of the solid surface to have non-specific interactions with probe molecules [22]. More details regarding the calculations of various parameters obtained from IGC-ID experiments were given in a previous paper [16].…”

“…The increasing of specific surface area was attributed to the elimination of carbonates with the acid treatment effect, and consequently to the creation of new porosity accessible to probes. On the other side, the decrease in the specific surface area after milling can be explained by the alteration of the internal structure of particles (physical alteration, such as the disappearance of porosity) [16].…”

“…It may be thought that grinding in Pulverisette0 contributes to generate silanol sites [16]. These silanol sites can develop hydrogen interactions with the injected isopropanol, which contributes to increase irreversibility index.…”

“…Among them, three were obtained using different milling processes, and one by an acid treatment. These mechanical and chemical activations of palygorskite [15,16] induced changes in microstructure morphology and surface chemistry. All these modifications were expected to deeply change interaction capacities of the samples with the media, which was a lead(II) ion containing solution.…”

Application of wet milling techniques to produce micronized and nanonized drug pre-dispersions for the development of intranasal formulations

“…A number of dry milling possibilities are known; the survey of these in Table 1 is non-exhaustive. Techniques for dry milling are usually used for micronization (Boudriche et al, 2014). In this case, the Rittinger theory describes the PS reduction produced relative to the energy (E) input of milling: the new surface area generated is directly proportional to the E required for the PS reduction.…”