New zeolite made from Tunisian raw clay: study and modeling for C3H6 breakthrough dynamic adsorption onto zeolite material.

In this study, Tunisian raw clay (RC) was utilized as a cheap source of silicium and aluminum for the preparation of faujasite zeolite (FAUsyn) using the alkaline fusion technique. The zeolite's structural analysis was carried out using the XRD, nitrogen adsorption-desorption, and SEM-EDX techniques. The data collected demonstrate that the produced zeolite only included one homogeneous faujasite phase. Textural analysis shows that the FAUsyn prepared from RC has a hierarchical porosity (micro-, meso-, and macropores). The total porosity was found to be 0.33 cm3/g as well as the BET area was equal to 360 m2/g. Adsorption experiments for propene capture were performed using the FAUsyn as adsorbent material. The performance of the column was examined in relation to various parameter impacts, including flow rate (50, 100, and 150 mL/min), input concentration (4, 8, and 12 mg/L), and bed depth (10, 14, and 18 cm). Finally, experimental and theoretical studies were investigated to predict adsorption capacities and kinetics parameters. To clarify and estimate column inputs, a model that incorporates axial dispersion, Langmuir equation, and migration within the adsorbent's pore was improved. COMSOL Multiphysics software was used to execute the model and resolve it computationally. The results of the experiments and the expected breakthrough curves were very well agreed. Modeling obtained results can be extrapolated to industrial level.

Use of Insect-Derived Chitosan for the Removal of Methylene Blue Dye from Wastewater: Process Optimization Using a Central Composite Design.

Insects are a readily available source of chitosan due to their high reproductive rates, ease of breeding, and resistance to changes in their ecosystem. This study aimed to extract chitosan from several widespread insects: Blaps lethifera (CS-BL), Pimelia fernandezlopezi (CS-PF), and Musca domestica (CS-MD). The study was also extended to using the obtained chitosans in removing methylene blue dye (MB) from wastewater. The source of the chitosan, the initial concentration of MB dye, and the reaction time were chosen as the working parameters. The experiments were designed using a central composite design (CCD) based on the dye removal efficiency as the response variable. The experimental work and statistical calculation of the CCD showed that the dye removal efficiency ranged from 35.9% to 88.7% for CS-BL, from 18.8% to 47.1% for CS-PF, and from 10.3% to 29.0% for CS-MD at an initial MB concentration of 12.79 mg/L. The highest methylene blue dye removal efficiency was 88.7% for CS-BL at a reaction time of 120 min. This indicates that the extraction of chitosan from insects (Blaps lethifera) and its application in dye removal is a promising, environmentally friendly, economical, biodegradable, and cost-effective process. Furthermore, the CCD is a statistical experimental design technique that can be used to optimize process variables for removing other organic pollutants using chitosan.

Sono-assisted adsorption of organic compounds contained in industrial solution on iron nanoparticles supported on clay: Optimization using central composite design.

Organic substance (O.S) in industrial phosphoric acid (IPA) solution is often tacked placed creates a major problem for IPA quality. This study was performed to assess the efficiency of Iron Intercalated Bentonite Nanoparticles (IIBN) coupled with the ultrasonic irradiation named sono-adsorption process for treating IPA 54% P2O5 contained O.S. XRD, SEM and BET were performed for the characterization of as-prepared adsorbent. Several conditions such as adsorbent dosage, molar ratio (OH/Fe) and time were investigated in retention experiments at acidic pH and T° of 40 ± 1 °C. The sono-assisted retention parameters were optimized by using NEMROOD software. The interaction impact of study condition on the final retention capability of the organism has been revealed by ANOVA software. Accordingly, the organic substance removal can be retained more than 83% by a sonication time of 0.5 h, absorbent dosage of 1.2 g/L and a molar ratio (OH/Fe) of 1.37. The absorbability of O.S was also evaluated by using the three parameters retention isotherms and kinetic analysis.

Sono-assisted adsorption of Cristal Violet dye onto Tunisian Smectite Clay: Characterization, kinetics and adsorption isotherms.

The present work describes the removal of Crystal violet from aqueous solution by Sono-assisted adsorption on Raw Tunisian Smectite Clay (RSC). This material was purified by dispersion in water and extraction of the fraction with a particle size smaller than 2 µm. the resulting material was characterized by XRD, TEM, BET, surface area and pore volume measurements. Batch studies were carried out to investigate the effect of experimental factors such as contact time (0-60 min), pH (2.5-11), adsorbent dose (0.05-0.3 g/L), and initial dye concentration (12.5-100 mg/L) on the Sono-assisted adsorption of Crystal violet dye. Adsorption kinetics was well fitted by pseudo-second order kinetic model. Langmuir (R2 = 0.988), Freundlich (R2 = 0.968), Langmuir-Freundlich (R2 = 0.997) and Toth (R2 = 0.999) isotherms were fitted to describe the equilibrium of Crystal violet Sono-assisted adsorption process. The results suggested that Natural Tunisian Smectite Clay is suitable as a sorbent material for Sono-assisted adsorption of Crystal violet dye from aqueous solutions.

Adsorption of terpenic compounds onto organo-palygorskite.

Essential oils from aromatic plants are currently mentioned as suitable tools for excellent protection of stored grains from insect pest attacks. The present work aimed to study the processes of the synthesis insecticidal formulation with clay. The active terpenic compounds of essential oil of Eucalyptus globulus (Eg) were fixed in the palygorskite by adsorption process. Two sample types of palygorskites were used: raw and organo-palygorskite. The palygorskite clays were characterized by different physicochemical techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR) analyses, thermogravimetric analysis (TG), differential thermal analysis (DTA), Brunauer-Emmet-Teller (BET), and scanning electron microscope (SEM). Results reveal that the raw clay has a fibrous structure with impurities essential calcite. These structures and physicochemical properties of raw palygorskite and organo-palygorskite give it the potential of material adsorbent. Results show that the adsorption capacity strongly depends on affinity between terpenic compounds and organic cations rather than on interlayer distance of organo-palygorskite. The highest adsorption capacity of terpenic compounds is acquired with palygorskite interlaced by didodecyldimethylammonium bromide (DDDMA). These results validated the potential utility of the Paly-DDDMA as adsorbent fibrous clay for the retention of terpenic compounds in application of environmental preservation.

Breakthrough modeling and experimental design for o-xylene dynamic adsorption onto clay material.

The adsorption of o-xylene onto raw clay material in a fixed bed using a thermal conductivity detector gas chromatography was investigated. Experimental and theoretical studies were established to evaluate the removal efficiency of o-xylene by adsorption on clay materials and to predict kinetic parameters. Column data were describing at different conditions using Bohart-Adams, Wolborska, Thomas, Yoon and Nelson, dose-response, and bed depth service time models. All used models were satisfactory to predict the breakthrough curves. A suitable advection-dispersion-sorption (ADS) model has been also developed to simulate the measured data, based on the nature of the various equilibrium relationships of solid-gas and diverse descriptions of the mass transfer processes within of the adsorbent particle. The experiments can be fitted with high correlated coefficient R 2 = 0.996.

Detection of terrain indices related to soil salinity and mapping salt-affected soils using remote sensing and geostatistical techniques.

Traditional surveying methods of soil properties over landscapes are dramatically cost and time-consuming. Thus, remote sensing is a proper choice for monitoring environmental problem. This research aims to study the effect of environmental factors on soil salinity and to map the spatial distribution of this salinity over the southern east part of Tunisia by means of remote sensing and geostatistical techniques. For this purpose, we used Advanced Spaceborne Thermal Emission and Reflection Radiometer data to depict geomorphological parameters: elevation, slope, plan curvature (PLC), profile curvature (PRC), and aspect. Pearson correlation between these parameters and soil electrical conductivity (ECsoil) showed that mainly slope and elevation affect the concentration of salt in soil. Moreover, spectral analysis illustrated the high potential of short-wave infrared (SWIR) bands to identify saline soils. To map soil salinity in southern Tunisia, ordinary kriging (OK), minimum distance (MD) classification, and simple regression (SR) were used. The findings showed that ordinary kriging technique provides the most reliable performances to identify and classify saline soils over the study area with a root mean square error of 1.83 and mean error of 0.018.

Purification of industrial phosphoric acid (54 %) using Fe-pillared bentonite.

The current problem of excess impurities in industrial phosphoric acid (IPA) 54 % P2O5 makes phosphates industries look toward low-cost but efficient adsorbents. In the present study, iron-oxide-modified bentonite (Fe-PILB) was prepared and investigated as a possible adsorbent for the removal of organic matter (OM) like humic acid (HA), chromium (Cr(III)), and zinc (Zn(II)) from IPA aqueous solutions. These adsorbents were characterized using XRD, TEM, and BET. The adsorption of impurities is well described by the pseudo-second-order model. The results indicate that Fe-PILB has a good ability to resist co-existing anions and the low-pH condition of IPA and owns a relatively high-removal capacity of 80.42 and 25 % for OM, Cr(III), and Zn(II). The mechanism of adsorption may be described by the ligand and ion exchange that happened on the active sites. The selected order of adsorption OM > Cr(3+) > Zn(2+) showed the importance of the competitive phenomenon onto bentonite materials' pore adsorption. For the adsorption of OM at the low pH of IPA, H-bond complexation was the dominant mechanism. From the adsorption of heavy metals and OM complex compounds contained in IPA 54 % on Fe-PILB, the bridging of humic acid between bentonite and heavy metals (Zn(II) or Cr(III)) is proposed as the dominant adsorption mechanism (bentonite-HA-Me). Overall, the results obtained in this study indicate Fe-pillared bentonite possesses a potential for the practical application of impurity (OM, Zn(II), and Cr(III)) removal from IPA aqueous solutions.

Almond shell activated carbon: adsorbent and catalytic support in the phenol degradation.

In this work, two technologies are studied for the removal of phenol from aqueous solution: dynamic adsorption onto activated carbon and photocatalysis. Almond shell activated carbon (ASAC) was used as adsorbent and catalytic support in the phenol degradation process. The prepared catalyst by deposition of anatase TiO2 on the surface of activated carbon was characterized by scanning electron microscopy, sorption of nitrogen, X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, and pHZPC point of zero charge. In the continuous adsorption experiments, the effects of flow rate, bed height, and solution temperature on the breakthrough curves have been studied. The breakthrough curves were favorably described by the Yoon-Nelson model. The photocatalytic degradation of phenol has been investigated at room temperature using TiO2-coated activated carbon as photocatalyst (TiO2/ASAC). The degradation reaction was optimized with respect to the phenol concentration and catalyst amount. The kinetics of disappearance of the organic pollutant followed an apparent first-order rate. The findings demonstrated the applicability of ASAC for the adsorptive and catalytic treatment of phenol.

Efficient degradation of phenol using natural clay as heterogeneous Fenton-like catalyst.

A natural containing Fe-clay (NRC) was used for the Fenton-like oxidation of phenol. This new catalyst was very efficient in phenol elimination in aqueous medium under mild experimental conditions (20 °C, atmospheric pressure and low concentration of hydrogen peroxide). The influence of different parameters like calcination's temperature, particle size, initial phenol and H2O2 concentrations were examined considering both phenol conversion and total organic carbon (TOC) removal. NRC was characterized by several complementary methods including chemical analysis, X-ray diffraction (XRD), Mössbauer spectroscopy, thermogravimetry-differential thermal analysis (TG-DTA), temperature programmed reduction (TPR) and BET. The experimental results showed that 100 % phenol conversion and 70 % TOC removal can be achieved using sieved and calcined NRC (d < 50 µm/450 °C). Catalytic activity of NRC was mainly attributed to the amount of iron oxide species (12.15 wt.%) present naturally in the clay.

Modelling the adsorption of mercury onto natural and aluminium pillared clays.

INTRODUCTION: The removal of heavy metals by natural adsorbent has become one of the most attractive solutions for environmental remediation. Natural clay collected from the Late Cretaceous Aleg formation, Tunisia was used as a natural adsorbent for the removal of Hg(II) in aqueous system. METHODS: Physicochemical characterization of the adsorbent was carried out with the aid of various techniques, including chemical analysis, X-ray diffraction, Fourier transform infrared and scanning electron micrograph. Batch sorption technique was selected as an appropriate technique in the current study. Method parameters, including pH, temperature, initial metal concentration and contact time, were varied in order to quantitatively evaluate their effects on Hg(II) adsorption onto the original and pillared clay samples. Adsorption kinetic was studied by fitting the experimental results to the pseudo-first-order and pseudo-second-order kinetic models. The adsorption data were also simulated with Langmuir, Freundlich and Temkin isotherms. RESULTS: Results showed that the natural clay samples are mainly composed of silica, alumina, iron, calcium and magnesium oxides. The sorbents are mainly mesoporous materials with specific surface area of <250 m(2) g(-1). From the adsorption of Hg(II) studies, experimental data demonstrated a high degree of fitness to the pseudo-second-order kinetics with an equilibration time of 240 min. The equilibrium data showed the best model fit to Langmuir model with the maximum adsorption capacities of 9.70 and 49.75 mg g(-1) for the original and aluminium pillared clays, respectively. The maximum adsorption of Hg(II) on the aluminium pillared clay was observed to occur at pH 3.2. The calculated thermodynamic parameters (∆G°, ∆H° and ∆S°) showed an exothermic adsorption process. The entropy values varied between 60.77 and 117.59 J mol(-1) K(-1), and those of enthalpy ranged from 16.31 to 30.77 kJ mol(-1). The equilibrium parameter (R (L)) indicated that the adsorption of Hg(II) on Tunisian smectitic clays was favourable under the experimental conditions of this study. CONCLUSION: The clay of the Aleg formation, Tunisia was found to be an efficient adsorbent for Hg(II) removal in aqueous systems.

Efficiency of natural and acid-activated clays in the removal of Pb(II) from aqueous solutions.

The adsorption of Pb(2+) ions onto Tunisian clay in aqueous solution was studied in a batch system. Four samples of clay (RGC, RRC, AGC, and ARC) were used. The raw RGC and RRC clays were sampled in jebel Tejera-Esghira in Medenine area (Southeast of Tunisia). AGC and ARC corresponds respectively to RGC and RRC activated by 6M sulphuric acid. The adsorbents employed were characterized by X-Ray Diffraction, chemical analysis, and the specific surface area was also estimated. The ability of clay samples to remove Pb(2+) ions from aqueous solutions has been studied at different operating conditions: temperature and pH. The optimum pH for lead ions retention was found 7.0 for the four clay samples. The effect of temperature on adsorption phenomenon was also investigated. The results indicated that adsorption is an exothermic process for lead ions removal. The equilibrium adsorption data were analysed using the Langmuir and Freundlich isotherms. The adsorption capacities (X(m)) for RRC, RGC, ARC and AGC were found 17.84, 25.44, 27.15 and 40.75 mg g(-1), respectively. The performance of the red clay after activation was compared to that of silica gel, which has maximum adsorption of 20 mg g(-1). On the other hand, although the performance of activated carbon (88.3 mg g(-1)) is by far higher than that of the green clay after activation, the latter seems to have better performance than that of the silica gel.

Valorization of olive mill wastewater by its incorporation in building bricks.

This investigation deals with the possibility of incorporating the effluent resulting from olive oil extraction activity, known as olive oil mill wastewater (OMW), in the brick-making process. It was undertaken at an important Tunisian brickworks company. In this study, the OMW was mixed with clays following the same brick-making procedure used at the collaborative brickworks in Tunisia. The samples containing OMW were found to be comparable in forming/extrusion performance to a control product that used fresh water. The experimental products produced were tested for their comparative physical properties (volume shrinkage, water absorption, tensile strength of bricks, after firing at 920 degrees C and paste plasticity) in the unfired and fired states against a control representing the commercial product in the same factory. The results showed a significant increase in the volume shrinkage (10%) and the water absorption (12%), while the tensile strength remained constant. The maximum plasticity index value was found when incorporating 23% of OMW. This rate either maintained the physical and mechanical properties of bricks or improved them. The incorporation of OMW in bricks can represent a promising way to valorize this effluent, to rid the environment of a highly polluting wastewater and to save huge and precious amounts of water in a country where water shortage is a serious problem. This newly-prepared material has a double positive impact: it protects the environment and allows water economy.