Discoloration of a red cationic dye by supported TiO(2) photocatalysis

The degradation under UV, visible and sunlight irradiation of C.I. Basic Red 46 (BR 46) dye used for acrylic fibers dyeing has been studied in a lab-scale continuous system with two different immobilized TiO(2) systems. Catalyst I was based on TiO(2) particles deposited on cellulose fibers; Catalyst II combined TiO(2) particles deposited on a layer of cellulose fibers (as in Catalyst I) with a layer of carbon fibers and finally a layer of cellulose fibers. The treatment of aqueous dye solutions and industrial wastewater contaminated with the same dye has been evaluated in terms of color removal and chemical oxygen demand (COD) decrease. With UV light, aqueous solutions containing dye were decolorized slightly more rapidly with Catalyst II than with Catalyst I. Sunlight was also very effective and experiments involving sunlight irradiation showed Catalyst II to be the more efficient, giving more than 90% discoloration after 20 min of treatment. Comparing the discoloration yield by adsorption or under visible light for both catalysts, it was observed that the difference between them is below 5%. The adsorption kinetics was found to follow a second-order rate law for Catalyst I and a first-order rate law for Catalyst II. The kinetics of photocatalytic degradation under UV or sunlight were found to follow a first-order rate law for both catalytic systems. Under sunlight the COD removal yield for textile wastewater reaches 33% with Catalyst I against 93% with Catalyst II.     

Rapid decolourization and mineralization of the azo dye C.I. Acid Red 14 by heterogeneous Fenton reaction

The decolourization and mineralization of a solution of an azo dye using a catalyst based on Fe(II) supported on Y Zeolite (Fe(II)-Y Zeolite) and adding hydrogen peroxide (heterogeneous Fenton process) have been studied. The catalyst was prepared by ion exchange, starting from a commercial ultra-stable Y Zeolite. All experiments were performed on a laboratory scale set-up. The effects of different parameters such as initial concentration of the dye, initial pH of the solution of the dye, H(2)O(2) concentration, temperature and ratio of amount of catalyst by amount of solution on the decolourization efficiency of the process were investigated. A percentage of colour removal of 99.3±0.2% and a mineralization degree of 84±5% of the solution of the dye were achieved in only 6 min of contact time between the catalyst and the solution, under the following conditions: initial concentration of the dye of 50 ppm, pH 5.96, 8.7 mM of H(2)O(2), T of 80°C and catalyst concentration of 15 g/L. Moreover, the catalyst Fe(II)-Y Zeolite can be easily filtered from the solution, does not leach any iron into the solution (avoiding any secondary contamination due to the metal) and its effectivity can be reproduced after consecutive experiments.     

Fatty acids,sterols, and tocopherols composition in seed oil extracts from four moroccan ecotypes of Ceratonia siliqua L.

Morphological characterization was investigated by agro-morphological criteria related to carob seed size in four different moroccan regions collected in 2018 and 2019. There was no significant difference (p ≤ 0.05) on the seeds lengths and widths. However, a significant difference between seeds thickness and total seeds weight per pod (p ≤ 0.05) were observed between these four populations. The fatty acid, sterol, tocopherol, hydrocarbon, and the unoxygenated composition of carob seed extracts (Ceratonia siliqua L.) were studied. The mean fat yield of the seeds obtained is 1.53%–2.17%, 2.14%–2.15%, 1.61%–1.62%, 1.71%–1.75% for, respectively, the P1 (Meknes), P2 (Fez), P3 (Khemisset), and P4 (Marrakech) in 2018 and 2019. The seed oil was extracted with hexane and the analysis of the fatty fraction was performed by gas chromatography–mass spectrometry (GC–MS). Results show that the major fatty acids for 2018 and 2019 are linoleic acid (61.48%–61.52%, 52.12%–52.14%, 57.76%–58.15%, 61.33%–61.52%), palmitic acid (15.78%–15.81%, 16.44%–16.45%, 19.11%–18.37%, 20.24%–20.32%), oleic acid (11.03%–11.04%, 8.72%–8.82%, 8.51%–8.61%, 8.41%–8.53%), stearic acid (4.35%–3.14%, 5.40%–5.43%, 3.12%–3.13%, 0.96%–1.56%), and cerotic acid (0.62%–0.53%, 4.51%–4.52%, 4.03%–4.06%, 3.84%–3.87%). The unsaturated fatty acids (69.39% in 2018 and 69.68% in 2019) are the most dominant in the four seed extracts compared to the saturated fatty acids. In addition, the oil carob seeds analysis revealed the presence of γ-tocopherol, α-tocopherol and four sterols that included campesterol, stigmasterol, and β-sitosterol. Moreover, the determination of hydrocarbon and un-oxygenated compounds confirmed the existence of major compounds such as heptadecane, 2-methyltriacontane, 1-iodo hexadecane and 1-iodo octadecane. The hierarchical analysis based on the morphological and chromatographic characterization of the seeds allowed the identification of three groups. Consequently, the first group consisted of populations from Marrakesh (P4) and Khemisset (P3), the second group consisted of the P1 from Meknes, and the P2 from Fez constituted the third group.     

Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite

The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na(2)S(2)O(4). Then, the adsorption experiments were studied in batch reactors at 25+/-3 degrees C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg(-1)min(-1) and that of Cr(VI) is 7.21 mmol kg(-1)min(-1). The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg(-1) (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg(-1). The mechanism of Hg(II) and Cr(VI) adsorption was discussed.     

Improvement of paint effluents coagulation using natural and synthetic coagulant aids

The coagulant iron chloride and the flocculants Polysep 3000 (PO), Superfloc A-1820 (SU) and Praestol 2515 TR (PR) have been used in this study to show the efficiency of coagulation flocculation process in the chemical precipitation method for the removal of organic and colouring matters from the paint industry wastewater. This study also includes the amount of produced sludge. The results indicate that FeCl(3) is efficient at pH range 8-9 and at optimal dose of 650 mgl(-1). Iron chloride allows the removal of 82% of chemical oxygen demand (COD) and 94% of colour. However, sequential addition of coagulant and polymeric additives enhance clearly pollutant removal and produces less decanted sludge compared to the results obtained when the coagulant is used alone. The removal efficiency of COD reaches 91% and that of colour 99%. Coagulation-biflocculation process is more effective than the coagulation-monoflocculation one. The sequential addition of iron chloride, Polysep 3000 (cationic flocculant) and Praestol 2515 TR (anionic flocculant) seems to be the most suitable combination for the treatment of the paint industry wastewaters.     

Experimental design to optimize preparation of activated carbons for use in water treatment

A series of seven activated carbons was obtained for use in drinking water treatments by steam-activation of olive-waste cakes. This raw material is an abundant and cheap waste byproduct of oil production, making these activated carbons economically feasible. The activated carbons, prepared by the one step method, were characterized, and the evolution of their characteristics (yield, adsorption capacities, and porosity) was analyzed as a function of the experimental parameters (activation temperature and activation time), using the Doehlert matrix. The Doehlert matrix allows the response surface to be studied with a good quality parameter estimation of the quadratic model. Each response has been described by a second order model that was adequate to predict responses in all experimental regions. The coefficients of the postulated model were calculated from the experimental responses by means of least squares regression, using the NEMROD software. We determined the region in which the optimum values of both activation temperature and activation time were achieved for the preparation of activated carbons suitable for use in water treatments. The "optimal activated carbon" was experimentally obtained, and its characteristic parameters showed a good agreement with those calculated from the model. The results obtained for activated carbons prepared by the one-step method were compared with those for activated carbons prepared by the two-step method. The characteristics of activated carbons obtained by the one-step and two-step methods showed that "one-step" activated carbons have a highly developed porous texture formed mainly of large macropores and micropores, whereas "two-step" activated carbons have a predominance of mesopores and narrow micropores. These activated carbons from olive-waste cakes showed a high capacity to adsorb herbicides (2,4-dichlorophenoxyacetic acid, 2,4-D; and 2-methyl, 4-chlorophenoxyacetic acid, MCPA) from water, with adsorption capacity values higher than those corresponding to a commercial activated carbon used from drinking water treatments.     

Removal of Basic Red 46 dye from aqueous solution by adsorption onto Moroccan clay

In this study, Moroccan crude clay of Safi, which was characterized by X-ray diffraction, is used as adsorbent for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the Basic Red 46 (BR46) in aqueous solutions at various dye concentrations, adsorbent masses and pH values. The results showed that the adsorption capacity of the dye increased by initial dye concentration and pH values. Two kinetic models (the pseudo-first-order and the pseudo-second-order) were used to calculate the adsorption rate constants. The adsorption kinetics of the basic dye followed pseudo-second-order model. The experimental data isotherms were analyzed using the Langmuir, Freundlich and Dubinin–Radushkevish equations. The monolayer adsorption capacity for BR46 dye is 54 mg/g of crude clay. Nearly 20 min of contact time was found to be sufficient for the dye adsorption to reach equilibrium. Thermodynamical parameters were also evaluated for the dye–adsorbent system and revealed that the adsorption process is exothermic in nature.     

Treatment of textile dye effluents using coagulation–flocculation coupled with membrane processes or adsorption on powdered activated carbon

This study describes the treatment of textile wastewater by various combinations of physicochemical and membrane processes. The basic physicochemical treatment consists in coagulation/flocculation (CF) with different coagulant and flocculant concentrations. The parameters analyzed prior and after treatment are turbidity, chemical oxygen demand (COD) and absorbance (Abs). The optimal process parameters for CF are 5 for pH, 100 mg/l for coagulant (Al₂(SO₄) ₃) of 100 mg/l and 4 mg/l for flocculant. This simple treatment by CF was inefficient concerning COD reduction and dyes deterioration. It was therefore combined with microfiltration (MF) or ultrafiltration (UF) on one hand and adsorption on powdered activated carbon (PAC) on the other. The CF/MF, CF/UF and CF/PAC combinations ensure a COD removal of 37%, 42% and more than 80% respectively and a color reduction of 65%, 74% and 50% respectively.     

Mechanical behavior and ultrasonic non-destructive characterization of elastic properties of cordierite-based ceramics

The structural and morphological evolutions of cordierite-based ceramics produced from stevensite/andalusite mixture sintered from 1150 to 1350 °C were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical behavior was investigated by three-point bending and Brazilian tests. The elastic properties were evaluated using ultrasonic non-destructive testing (NDT). XRD results revealed that the main crystalline phase formed at 1300 and 1350 °C was cordierite with traces of mullite. A linear-elastic behavior followed by brittle fracture was observed in three-point bending test with the presence of multiple discontinuities. Flexural and diametral compression strength values of cordierite sintered at 1300 °C were 39.4±4 and 21.8±2 MPa, respectively. The elastic properties such as Young's modulus (38.7–45.1 GPa), shear modulus (17.90–19.42 GPa) and Poisson ratio (0.08–1.6) of cordierite-based ceramics produced at 1350 and 1300 °C were also determined.