Potential of a Tunisian Natural Clay to Remove Cationic and Anionic Dyes From Polluted Waters

The objective of this study is to show the adsorption power of Tunisian smectitic clay from Jebel Aidoudi from the region of El Hamma (southern Tunisia). A cationic dye (Methylene Blue: MB) and an anionic dye (Orange II: OII) are used to determine the maximum absorbability of clay. Physico-chemical characterization tests (XRD, XRF, SBET) on the clay sample were performed. The experimental results showed that the optimal contact time of adsorption is 40 min (91.35% and 51.87%, respectively, for MB and OII). An increase in the retention rate of the dyes was noted by varying the adsorbent rate from 0.06 g to 0.12 g. The experimental results showed that the retention was strongly influenced by the pH of the medium (a high adsorption rate of MB at basic pH and a high adsorption rate for OII at acidic pH). The adsorption capacities are well described by the Langmuir isotherm. The pseudo-second order model is the most reliable for determining the order of absorption kinetics of MM and OII by this smectitic clay

Preparation of Silica Gel Obtained From Early Cretaceous Sidi Aich Sands (Central Tunisia) and its potential to remove pollutant dye anionic from wastewaters

The present study concerns the elimination by retention of the anionic dye orange II (OII) from aqueous solutions was studied using a silica gel prepared from Tunisian silica sands (Barremian age). These Sidi Aich sands were collected in central Tunisia. The collected raw silica sand from the Jebel Meloussi (central Tunisia) was characterised by different techniques, such as X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). X-ray diffraction showed a predominance of quartz and potassic feldspars and lower amounts of kaolinite and calcite. The N-2 adsorption isotherms show that these are mesoporous materials with high chemi-physical adsorption capabilities, and indicated a multilayer process for N-2 absorption. They had pore diameters between 60 and 118 angstrom (mesoporous) and specific surface areas up to 183 m(2)/g, close to those reported for commercial silica gel materials. Maximum retention rates of the anionic dye orange II (OII, up to 89.73 % after 180 min contact time) were achieved with products prepared in acidic medium (pH 3). The adsorption is mechanism was well described with both Langmuir and Freundlich models, allowing for a multilayer coverage process of OII molecules on the gel surface, and the pseudo-second-order model is the most reliable for determining the order of absorption kinetics of OII by silica gel. The values of the adsorption capacities at equilibrium calculated (Qe = 242 mg / g) by the pseudo-second-order model are very close to the Qe determined experimentally (224 mg / g), and to those of an industrial silica gel (234 mg / g)

Green Synthesis of Iron Nanoparticle/Clay Composites and Their Effectiveness in Orange II Dye Removal Efficiency

This paper presents a study on orange II sodium salt (OII) degradation based on iron nanoparticles supported by kaolinite clays. The effects of nanoscale iron and initial dye concentration, as well as hydrogen peroxide dosage in a Fenton process, on the degradation of OII were studied. These nanoparticles were synthesized by green methods using coffee bean extract as a natural antioxidant for this process. Aqueous iron chloride was mixed with coffee extract, which is rich in antioxidants, and these antioxidants are responsible for the reduction of metal compounds into nanoparticles. The composite iron nanoparticle-kaolinite composite was synthesized from an aqueous FeCl3 and kaolinite solution with the added coffee bean extract. The results showed that OII removal efficiency increased with the amount of iron nanoparticles (n-Fe) alone and with the amount iron-supported-kaolinite composite. By increasing the amount of composite, the adsorptive surface area increases as well as the number of active sites, which determine the higher removal efficiency. Regarding H2O2 dosage, dye removal was more efficient at lower quantities: 62% removal efficiency with addition of 10 mL H2O2, while for the test conducted with 20 mL H2O2, removal efficiency was 47%. A possible reason for this behavior can be the n-Fe/ H2O2 ratio, which influences the production of degradation products and hinders the degradation

The controversial role of mast cells in fibrosis

Fibrosis is a medical condition characterized by an excessive deposition of extracellular matrix compounds such as collagen in tissues. Fibrotic lesions are present in many diseases and can affect all organs. The excessive extracellular matrix accumulation in these conditions can often have serious consequences and in many cases be life-threatening. A typical event seen in many fibrotic conditions is a profound accumulation of mast cells (MCs), suggesting that these cells can contribute to the pathology. Indeed, there is now substantial evidence pointing to an important role of MCs in fibrotic disease. However, investigations from various clinical settings and different animal models have arrived at partly contradictory conclusions as to how MCs affect fibrosis, with many studies suggesting a detrimental role of MCs whereas others suggest that MCs can be protective. Here, we review the current knowledge of how MCs can affect fibrosis