Natural Tunisian Clay Research Articles

Photocatalytic degradation of Acridine orange dye and real textile wastewater via ZnO nanoparticle supported natural Tunisian clay

Photocatalytic degradation of Acridine orange dye and real textile wastewater via ZnO nanoparticle supported natural Tunisian clay

Elaboration and properties of low-cost ceramic microfiltration membrane from local Tunisian clay for wastewater treatment

Abstract This study focused on the development and preparation of a microfiltration membrane, based on a low-cost natural Tunisian clay powder, deposited on macro-porous ceramic support. The deposit was made through a dip-coating technique, followed by a drying process and sintering at 700 °C. Results revealed that the obtained membrane was characterized by a good adhesion between the membrane layer and the ceramic support, an average pore diameter of 0.34 mm, and a porosity of 39%. This membrane was applied in the treatment of wastewater generated by the wastewater treatment plant of Sfax, Tunisia. The performances in terms of permeate flux and efficiency were determined in order to reduce the pollutant content expressed in terms of turbidity, biochemical oxygen demand (BOD5), and suspended matter (MES). Results showed an MES retention value of about 15%, and turbidity and BOD5 retention rate of 99% and ~100%, respectively.

Adsorption of Bisphenol A from Aqueous Solution by HDTMA-Tunisian Clay Synthesized Under Microwave Irradiation: A Parametric and Thermodynamic Study

AbstractBisphenol A (BPA), an endocrine disrupting compound, is of concern because of its wide presence throughout the environment and its harmful effects. The present study aimed to prepare an eco-friendly, low-cost, and efficient adsorbent for removal of BPA from wastewater. A natural Tunisian clay was used as a raw material. First, the clay was purified and then modified with hexadecyltrimethylammonium bromide (HDTMA) using microwave heating. The optimal conditions for clay modification were as follows: activation ratio = 0.3:(g/g), solid/liquid ratio = 5%, and microwave heating condition (2:min, 100:W). The purified and modified clays, abbreviated as HP and HMH, respectively, were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption/desorption analysis (BET). Adsorption tests were conducted in a batch reactor process under various conditions. The tests showed that the BET specific surface area of HMH is considerably smaller than that of HP, whereas the basal spacing increased from 14.99 to 22.07 Å after modification, indicating the success of HP organophilization. The adsorption of BPA onto HMH was not affected by the pH of solution between 2 and 10 and only slightly by temperature variation from 23 to 50°C, but was affected significantly by the initial concentration of BPA, contact time, and organo-clay dose. At equilibrium, the data obtained were fitted to Langmuir and Freundlich models. The best fit was obtained by the Langmuir model with a maximum monolayer adsorption capacity of 217.39 mg/g at 23°C. The thermodynamic study suggested that the removal of BPA by HMH was spontaneous (ΔG < 0), exothermic (ΔH < 0), and favorable. The present study demonstrated that HMH synthesized from an abundant and cheap natural clay could be used successfully as a low-cost adsorbent for the removal of BPA from wastewater.

Cancrinite synthesis from natural kaolinite by high pressure hydrothermal method: Application to the removal of Cd2+ and Pb2+ from water

Abstract Zeolites were synthesized from natural Tunisian clay by hydrothermal treatment under high pressure (100 MPa H2O pressure) at different gradients of temperature in high pressure autoclaves. The natural clay was first heated at 650 °C (HC-heated clay) and then transformed to an amorphous phase at 650 °C by adding different amount of NaOH. By increasing temperature and NaOH content, low-density frameworks zeolites like faujasite are transformed into more stable zeolites having higher density frameworks like cancrinite due to dissolution and recrystallisation steps. Cancrinite (Na8(H20)2CO3[Al6Si6O24]) (IZA-code: CAN) was successfully synthesized with a good purity. The synthesized CAN was characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The removal performance of heavy metal ions (Cd2+, Pb2+) from solution by pure CAN and clays has been studied. The kinetics of adsorption of Cd2+ and Pb2+ are very fast: equilibrium is reached within 2 min at 298 K. The capacity of adsorption of CAN is higher for Pb2+ (192 mg g−1) than for Cd2+ (68 mg g−1). Adsorption equilibrium of Cd2+ and Pb2+ on CAN were well represented by Langmuir equation although the thermodynamic study reveals a more complex mechanism: thermodynamic parameters, such as equilibrium constant, free energy, entropy and enthalpy for adsorption were obtained from the experimental data, including adsorption microcalorimetry.

A comparative study of natural Tunisian clay types in the formulation of compacted earth blocks

This study investigates the physico-chemical, mineralogical and thermal characteristics of three natural Tunisian clays collected from Gafsa (A1), Zeramdine (A2) and Nabeul (A3). The aim was to promote an appropriate formulation of materials and to obtain optimal compacted earth blocks (CEB). Results of mineralogical analysis of clays revealed the dominance of kaolinite (>13.58%), illite (>25.7%), quartz (>18%) and a minor fraction of smectite phases. Chemical analysis of the clays major elements showed a SiO2 content exceeding 50% and a percentage of Al2O3 higher than 18%. Particle size distribution showed that clay fractions varied from 10 to 20%. Plasticity index defined a plastic character while the values of specific surface area were around 60 m2/g. This discrepancy has an effect on the behavior of these clays in CEB, notably their mechanical properties. From this characterization, it appears that all the sampled clays are suitable as raw material for CEB application. The prepared CEB formulations varied according to compaction energy and binder dosages. In this work, lime served as a binder at different rates (4, 6, 8 and 10%) to ameliorate the quality of CEB. Unconfined Compressive Strength values were determined by Static method test. Then bulk density, shrinkage and porosity values of samples were determined. Compressive strength could reach 7 MPa with lime supplementation in sample A1. The static compaction onto the sand-clay mixture achieved a value of density superior to 2 g cm−3 with lime supplementation in sample A1. Overall, the Gafsa clay was the most suitable for CEB preparation. Also, lime improved the compressive strength of the matrix, in addition to its ecological merits.

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.

Photocatalytic decolorization of cationic and anionic dyes over ZnO nanoparticle immobilized on natural Tunisian clay

In the present work we describe a simple and low-cost method for the decolorization of textile dyeing and printing wastewaters, using ZnO as photocatalyst supported on natural Tunisian clay (ZnO/Clay). This composite ZnO/Clay material was synthesized through a sol–gel method. X-ray diffraction (XRD), Nitrogen Physisorption (BET), Infrared Spectroscopy (FTIR), Scanning Electronic Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HRTEM) linked with Energy Dispersive X-ray (EDX), were performed in order to explain the characteristics of the ZnO/Clay photocatalyst. The XRD patterns, pointing to the presence of ZnO of very small crystal sizes, i.e. highly dispersed on the clay surface. The photocatalytic activity of ZnO/Clay was assayed in the decolorization of a cationic dye (Malachite Green, MG) and anionic dyes (Red Congo, RC) in aqueous solution as models pollutants under UV irradiation. In addition, the effects of different parameters such as pH of the solution, catalyst dosage, concentration of the dyes, irradiation source, as well as the influence of the presence of inorganic ions were investigated. The ZnO/Clay photocatalyst exhibited high photocatalytic activity of MG and CR decolorization under simulated solar compared to UV irradiation. The recyclability of the ZnO/Clay photocatalyst was as well validated.

Photocatalytic degradation of methyl green dye in aqueous solution over natural clay-supported ZnO–TiO 2 catalysts

A ZnO–TiO2/clay photcatalyst was prepared using a natural Tunisian clay as support. Its activity was assayed in the photocatalytic degradation of methyl green in aqueous solutions, in the presence of UVA irradiation. The photocatalyst was synthesized using a metal organic chemical vapor deposition (MOCVD) with Ti (OPri)4 deposed on the natural Na+–clay, followed by a modified sol–gel synthesis method for introduction. The sample was then characterized by scanning electronic microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N2 adsorption, X-ray diffraction (XRD) and titration for the determination of the zero point charge (pHZPC). The activity tests showed that the photodegradation efficiency for ZnO–TiO2/clay is higher than for the TiO2/clay catalyst, clearly pointing to a promoting effect of ZnO. The influence of operational parameters such as pH, catalyst dosage, initial dye concentration, UV irradiation intensity, as well as the influence of the presence of different oxidants was evaluated. Almost complete mineralization was obtained upon 30 min of light irradiation in the presence of the ZnO–TiO2/clay catalyst.

Structure and properties of new eco-material obtained by phosphoric acid attack of natural Tunisian clay

In this work, new three dimensional geopolymer materials based on dehydroxylated natural kaolin and phosphoric acid were synthesized.The effects of Si/P molar ratio and curing time were studied. The structures of raw, calcined kaolin and geopolymers synthesized were investigated using X-ray diffraction analysis, IR spectroscopy, scanning electronic microscope, 31P, 29Si and 27Al MAS-NMR and by mechanical measurements.The mechanical strength of geopolymers is maximum when Si/P molar ratio, equal to 2.25, which corresponds to Al/P ratio=1. The mechanical properties are correlated with the amount of amorphous phase in geopolymer which is determined by the Rietveld method. In addition to metakaolin, illite mineral contributes to geopolymerization.

Fe-clay-plate as a heterogeneous catalyst in photo-Fenton oxidation of phenol as probe molecule for water treatment

A novel heterogeneous photo-Fenton plate catalyst was prepared by immobilizing iron species on the surface of natural Tunisian clay. The activity of this structured catalyst was assayed in the degradation of phenol under UV irradiation at two different wavelengths (245nm, UVC, and 365nm, UVA, radiation). Phenol removal rate from the aqueous solution always increased in the presence of the Fe-plate catalyst, even under dark-Fenton conditions and for both 254 and 365nm UV radiation, confirming the efficiency of the prepared catalytic system in the Fenton process. HPLC analysis confirmed a phenol degradation mechanism towards an almost complete mineralization of the organic compound. An apparent activation energy of 48.7kJ/mol was calculated from the removal experiments performed at different reaction temperatures in the presence of the Fe-plate catalyst. Catalytic activity remains almost unaltered after five consecutive reaction cycles re-using the same Fe-plate. Catalyst stability was confirmed by means of TEM–EDX analysis, pointing to this novel plate catalyst as a promising option as a Fenton heterogeneous catalyst for the mineralization of organic compounds in wastewaters.