Fadhila Ayari

The remarkable effect of Al–Fe pillaring on the adsorption and catalytic activity of natural Tunisian bentonite in the degradation of azo dye

Four Al–Fe–PILC catalysts were prepared by pillaring process and tested for the degradation of diazo dye in heterogeneous Fenton-like process. The synthesized catalysts were characterized using XRD, N2 sorption, XRF and TEM techniques in order to study the influence of iron and Al loading on structure and texture. In this work, at Fe loading of 10%, pillared clay was studied and investigated in catalytic test. The effects of major parameters, such as initial pH, H2O2 concentration and catalyst dose were tested on the activity as well as iron leaching from catalyst. Results of this study show that dye degradation rate increased with an increase in dosages of catalyst and concentration of H2O2 up to a certain limit. However, the degradation rate decreased with an increase in the pH. Mineralization and comparison with different catalysts prepared were evaluated by analyzing color removal and inorganic ions (SO42−, NO3−) concentrations. The kinetic studies revealed that the degradation profile is well fitted by the first-order kinetic model.

Hybrid material based on clay and calixarenic derivatives

Hybrid nanocomposites were obtained in this study by solid–solid reaction based on calixarenic derivatives and natural Tunisian clay: clay-calixarene. For this purpose, two calixarenic derivatives were synthesized and their properties were studied. Results show their affinity towards bivalent mercury and lithium by complexation in a homogeneous medium and vis-a-vis the rubidium by extraction of water to dichloromethane. The clay was purified and characterized by means of X-ray diffraction, X-ray fluorescence, cation exchange capacity and BET techniques. Intercalation of the calixarenes in the interfoliar space of the clay has been demonstrated by the spacing of the basal space after reaction and the comparison of infrared spectra confirms that the reaction has taken place. In addition, these hybrids have developed important specific surfaces area. Both nanocomposites prepared are among the first synthesis of clay-calixarenic hybrids in solid state. According to the calixarenic structures, it is assumed that these materials were of class II hybrids.

Synthesized and characterization of organobentonites for anionic dye removal: application to real textile effluent

ABSTRACT Clays have been considered as potential alternative adsorbents due to their high adsorptive property, abundance and non-toxic compounds. Adsorption of cationic dyes by natural clays has been studied and appreciable results have been reported, but few researchers have been interested in anionic dyes. Anionic dyes are widely used by the textile industries, yet they are toxic, non-biodegradable and hardly adsorbable on natural clay; modified clay (e.g. organoclay) has emerged as an alternative adsorbent. In this study, organobentonites were prepared with hexadecyltrimethylammonium bromide at three cation exchange capacity levels and used as adsorbents for the removal of, reactive blue II – an anionic dye used in Tunisian textile industry to dye jeans. Obtained organobentonite-labelled Hi-bent (Iu2009=u20091, 2 and 3) was characterized by several techniques in order to study the effect of a surfactant on texture and structure of the initial clay. H3-bent and purified bentonite (Na-bent) were then tested as adsorbents. The amount of dye removal by H3-bent (98%) was found to be around five times higher than that of Na-bent (19%). Adsorption process was well described by Freundlich, Dubinin–Radushkevic and Elovich isotherms model. Kinetic data were fitted by both pseudo-second-order and pseudo-first-order models. The use of Na-bent, as adsorbent, for real textile effluent treatment was tested, and significant results related to two other clay minerals were obtained. GRAPHICAL ABSTRACT

Physicochemical characteristics of organophilic clays prepared using two organo-modifiers: alkylammonium cation arrangement models

The clay was modified by an ion exchange reaction with cetylpyridinium chloride CPC and hexadecyltrimethylammonium bromide HDTMA. The modified samples were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The basal spacing of unmodified clay determined by XRD was 12.72xa0Å and, after modification, increased with increasing concentration; expressed as a function of the cation exchange capacity (CEC) of the clay; to reach 21.08 and 26xa0Å for clays modified with CPC and HDTMA successively for an equal concentration of 3CEC. FTIR studies revealed structural differences between modified and unmodified clay samples. Modified clay spectra showed C–N functional bands (1480xa0cm−1) and C–H vibrations (near 2936 and 2871xa0cm−1). The results of the SEM study reveal a difference between natural and modified clays. The purified clay has massive and curved plates. However, the modified clays show numerous small aggregate particles and plaques that become relatively flat. The arrangement of surfactants in clay is rather complicated. It depends on the nature of the surfactant molecules, the CEC of the clay and the method of preparation. According to these parameters, the inserted surfactants may be arranged in monolayer, paraffinic or admicelles structures.

X-ray fluorescence analysis of Portland cement and clinker for major and trace elements: accuracy and precision

Accurate, rapid methods for controlling and determining composition are necessary to aid in classification of cements and for correlation of performance characteristics with composition. X-ray fluorescence (XRF) is used to adjust the raw material proportions and to control the process conditions. The aim of the present study was to establish a reliable analytical program by X-ray fluorescence spectrometry, based on the choice of a well-defined range of standards, which are used to control the quality of the clinker. The results showed a second order polynomial regression model that could properly interpret the experimental data with an R2 value >0.97 even after correction for some elements. The results obtained indicate the reliability, reproducibility, and the ease of use of the established program.