Influence of acid–base properties of cobalt–molybdenum catalysts supported on magnesium orthophosphates in isomerization of 3,3-dimethylbut-1-ene

AbstractSynthesis and physico-chemical characterization of a pure magnesium phosphate (MgP) prepared by coprecipitation, and MgP modified by introduction of cobalt–molybdenum (4–12wt.% of MoO3 with the Co/Mo ratio fixed at 0.5) have been carried out. The structural properties of these catalysts were characterized by X-ray diffraction, their textural properties were determined by N2 adsorption–desorption isotherms and the dispersion of cobalt–molybdenum was studied by XPS spectroscopy. Their acid properties have been investigated by in situ FT-IR spectroscopy of adsorbed molecules, often, 2,6-dimethylpyridine (pKa=6.7), pyridine (pKa=5.3). Co–Mo incorporation leads to a modification in the MgP acid–base properties, especially on the acid sites type and number. Thus, lower loading of cobalt–molybdenum species decreased the number of strong Lewis acid sites whereas higher loading increased it. It was found that Lewis acid sites on magnesium phosphates play an important role in the isomerization of 3,3-dimethylbut-1-ene.The 3,3-dimethylbut-1-ene (33DMB1) conversion increases with the reaction temperature from 493 to 653K for MgP, but decreases after 573K for MgP supported by Co–Mo. A linear relationship between both types of acid sites and conversion values was found. The deactivation of the catalysts appears at high reaction temperature (>573K)

Synthesis, characterization, and photocatalytic degradation of anionic dyes using a novel ZnO/activated carbon composite

Zinc oxide/activated carbon from Thapsia transtagana stems (ZnO/ACTTS) composite demonstrated good photocatalytic properties for removing methyl orange (MO) dye from aqueous solution. This study utilized the chemical activation method using phosphoric acid to prepare activated carbon, which was then used to synthesize the ZnO/ACTTS composites by the hydrothermal technique at different percentages of the amount of ZnO (15, 30, 50 and 75 %). XRD, FTIR, and SEM-EDX were used to characterize the produced composite materials. The photocatalytic degradation of the catalysts was investigated for the degradation of MO dye from aqueous solution. The effects of zinc oxide content, pH of solution, and catalyst dosage were studied. Experimental results indicate that the ZnO/ACTTS (75 %) composite with exhibited good activity under acid pH conditions with an optimal catalyst dosage of 0.5 g/L. Photodegradation kinetics followed a pseudo-second order kinetics. ZnO/ACTTS composite will be a catalyst to degrade a wide range of dyes from the textile industry in the aquatic medium

Synthesis, characterization and efficient photocatalytic properties of spinel materials for dye degradation

In this research, Co0.5Zn0.5Al2O4 spinel oxides photocatalysts were elaborated from layered double hydroxides Co-Zn-Al/CO3 precursor by calcination at 300, 400, 500, 600, 800, and 1000 °C. XRD, FTIR, TGA/DTA, and SEM/EDX analysis were used for characterized of prepared photocatalysts. The photocatalytic efficiency of the prepared materials was tested by photodegradation of methyl orange (MO) azo dye as a model of textile contaminants under UV illumination. The effect of various operational factors such as irradiation time, initial pH, catalyst dose, methyl orange concentration and reuse were investigated. The enhancement of the photodegradation was strongly dependent on the calcination temperature. A synergic effect between the adsorption and photodegradation was observed. After 50 min of irradiation, the catalyst calcined at 400 °C showed the highest efficiency (98.2%). After regeneration (up to five cycles), the photocatalyst showed high stability

Adsorption behavior of methylene blue onto powdered Ziziphus lotus fruit peels and Avocado kernels seeds

In this research, two agroforestry by‐products were used as adsorbents for the removal of methylene blue (MB), as a model dye, from aqueous solution. The Ziziphus lotus fruit peels (ZLP) and Avocado kernel seed (AKS) were dried and powdered to particles of sizes <125 μm. Adsorption study was carried out in batch mode under different condition by varying initial dye concentration, contact time, initial solution pH, adsorbent dosage and reaction temperature. Rate constants of the adsorption were calculated by kinetic measurements. Equilibrium data were correlated to Langmuir and Freundlich isotherm models. The best fit was obtained by Langmuir model with maximum monolayer adsorption capacities of 66.04 mg/g in the case of ZLP and 59.07 mg/g in the case of AKS. The surface properties of the adsorbents were characterized by FTIR spectroscopy, SEM‐EDX analysis and the point of zero charge

Treatment of textile effluents by chloride-intercalated Zn-, Mg- and Ni-Al layered double hydroxides

This work involved the preparation, characterization and dyes removal ability of Zn-Al, Mg-Al and Ni-Al layered double hydroxide (LDH) minerals intercalated by chloride ions. The materials were synthetized by the co-precipitation method. X-ray diffraction, Fourier transform infrared, thermogravimetric-differential thermal analysis and transmission electron microscopy characterization exhibited a typical hydrotalcite structure for all the samples. Adsorption experiments for methyl orange were performed in terms of solution pH, contact time and initial dye concentration. Experimental results indicate that the capacity of dye uptake augmented rapidly within the first 60 min and then stayed practically the same regardless of the concentration. Maximum adsorption occurred with acidic pH medium. Kinetic data were studied using pseudo-first-order and pseudo-second-order kinetic models. Suitable correlation was acquired with the pseudo-second-order kinetic model. Equilibrium data were fitted to Langmuir and Freundlich isotherm models. The maximum Langmuir monolayer adsorption capacities were 2,758, 1,622 and 800 mg/g, respectively, for Zn-Al-Cl, Mg-Al-Cl and Ni-Al-Cl. The materials were later examined for the elimination of color and chemical oxygen demand (COD) from a real textile effluent wastewater. The results indicated that the suitable conditions for color and COD removal were acquired at pH of 5. The maximum COD removal efficiency from the effluent was noted as 92.84% for Zn-Al-Cl LDH

New Sustainable Biosorbent Based on Recycled Deoiled Carob Seeds: Optimization of Heavy Metals Remediation

In this study, an efficient biosorbent was developed from deoiled carob seeds, a agroindustrial waste. The biosorption efficiency was evaluated for cadmium and cobalt ions removal from aqueous solution under various parameters such as treating agent, solution pH, biosorbent dosage, contact time, initial metal ions concentration, and temperature. The effect of some major inorganic ions including Na+, K+, Ca2+, Mg2+, and Al3+ on the biosorption was also established. Based on this preliminary study, four independent variables including solution pH, biosorbents dosage, initial metal concentration, and treating agent were chosen for the optimization of the process using full-factorial experimental design. It was found that chemical pretreatment of the raw deoiled carob seeds with NaOH strongly enhances its biosorption potential. Thus, the optimal conditions for high biosorption of cadmium(II) and cobalt(II) were achieved at pH of 6, biosorbent dosage of 1 g/L, and initial metal concentration of 50 mg/L. The biosorbents were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Boehm titration, and the point of zero charge (pHPZC)