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

Performance of Zn‐, Mg‐ and Ni‐Al layered double hydroxides in treating an industrial textile wastewater

In this study, Zn‐Al, Mg‐Al and Ni‐Al layered double hydroxides were successfully synthesized via co‐precipitation method. Samples were characterized by XRD, FTIR, TGA‐DTA, TEM and pHPZC analysis. XRD patterns showed a basal spacing increase in the order of Zn‐AlNO3 (8.85Å)> Mg‐AlNO3 (7.95Å)> Ni‐AlNO3 (7.82Å). TEM images indicated that the Zn‐AlNO3 presents circular to shaped particles with an average particle size of approximately 30 to 40 nm. Small plates assigned to sheets with hexagonal form were observed in the case of Mg‐AlNO3. Ni‐AlNO3 display nanostructured sphere in diameter between 5 and 10 nm. The materials were used for the removal of methyl orange (MO), as a model dye and for the treatment of a real effluent generated by a textile factory. Maximum adsorption was occurred in acidic pH solution. Kinetic data were tested using pseudo‐first‐order, pseudo‐second‐order kinetic and intra‐particle diffusion models. The best fit was obtained with the pseudo‐second‐order kinetic model. Equilibrium data were correlated to Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models. The best conditions for color and COD removal from the textile effluent sample were obtained at lower values of pH. Reduction of COD to limits authorized by Moroccan standards was obtained with 0.5g/L of LDH dosage

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

Effectiveness of beetroot seeds and H3PO4 activated beetroot seeds for the removal of dyes from aqueous solutions

Raw beetroot seeds (BS) and H3PO4 activated beetroot seeds (H3PO4-BS) were evaluate for their effectiveness in removing methylene blue (MB) and malachite green (MG) from aqueous solution. BS were carbonized at 500°C for 2 h, and then impregnated with phosphoric acid (phosphoric acid to BS ratio of 1.5 g/g). The impregnated BS were activated in a tubular vertical furnace at 450°C for 2 h. Batch sorption experiments were carried out under various parameters, such as solution pH, adsorbent dosage, contact time, initial dyes concentration and temperature. The experimental results show that the dye sorption was influenced by solution pH and it was greater in the basic range. The sorption yield increases with an increase in the adsorbent dosage. The equilibrium uptake was increased with an increase in the initial dye concentration in solution. Adsorption kinetic data conformed more to the pseudo-second-order kinetic model. The experimental isotherm data were evaluated by Langmuir, Freundlich, Toth and Dubinin–Radushkevich isotherm models. The Langmuir maximum monolayer adsorption capacities were 61.11 and 74.37 mg/g for MB, 51.31 and 213.01 mg/g for MG, respectively in the case of BS and H3PO4-BS. The thermodynamic parameters are also evaluated and discussed

Enhanced photocatalytic degradation of caffeine as a model pharmaceutical pollutant by Ag-ZnO-Al2O3 nanocomposite

International audienceIn this paper, an Ag-ZnO-Al2O3 nanocomposite with enhanced photocatalytic activity has been obtained by calcination of an Ag-loaded zinc/aluminum layered double hydroxide (LDH). First, LDH materials intercalated by carbonates ions (Zn-Al-CO3) were synthesized by the co-precipitation method at a Zn/Al molar ratio of 3 and were calcined at different temperatures (300, 400, 500, 600, 800, and 1000 degrees C). Thereafter, in order to increase photocatalytic activity, catalysts obtained at optimal temperature were doped by Ag noble metal with various amounts (1, 3, and 5 wt %) using a ceramic process. Samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM/EDX). The photocatalytic activity was evaluated for the degradation of caffeine as a model of pharmaceutical pollutant in aqueous solutions under UV irradiation. The effect of irradiation time, initial concentration of caffeine, catalyst dosage, solution pH, and reuse were investigated. The Ag-doped calcined LDH materials showed significantly higher photocatalytic activity compared with undoped and standard Degussa P-25 titanium dioxide. The photocatalytic degradation of caffeine was increased with an increase in the Ag-loaded amounts. The photocatalyst showed high stability after three regeneration cycles

Performance of Zn-, Mg- and Ni-Al layered double hydroxides in treating an industrial textile wastewater

In this study, Zn-Al, Mg-Al and Ni-Al layered double hydroxides were successfully synthesized via co-precipitation method. Samples were characterized by XRD, FTIR, TGA-DTA, TEM and pHPZC analysis. XRD patterns showed a basal spacing increase in the order of Zn-AlNO3 (8.85Å)> Mg-AlNO3 (7.95Å)> Ni-AlNO3 (7.82Å). TEM images indicated that the Zn-AlNO3 presents circular to shaped particles with an average particle size of approximately 30 to 40 nm. Small plates assigned to sheets with hexagonal form were observed in the case of Mg-AlNO3.Ni-AlNO3 display nanostructured sphere in diameter between 5 and 10 nm. The materials were used for the removal of methyl orange (MO), as a model dye and for the treatment of a real effluent generated by a textile factory. Maximum adsorption was occurred in acidic pH solution. Kinetic data were tested using pseudo-first-order, pseudo-second-order kinetic and intra-particle diffusion models. The best fit was obtained with the pseudo-second-order kinetic model. Equilibrium data were correlated to Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models. The best conditions for color and COD removal from the textile effluent sample were obtained at lower values of pH. Reduction of COD to limits authorized by Moroccan standards was obtained with 0.5g/L of LDH dosage

Color and organic matter removal from textile effluents by synthetic layered double hydroxides and natural clays

This study focused on the removal of dyes and the reduction of COD of textile effluents by natural clay and a synthesized layered double hydroxide (HDL). The raw clay used in this work was collected from the region of Safi in Morocco. Mg/Fe-LDH adsorbent was synthesized using co-precipitation method at room temperature. Samples were characterized by XRD, SEM. The different physical and chemical parameters of the textile discharges (Electrical conductivity, TSS, COD, BOD5, NO2 and Total phosphorus) were evaluated. Experimental results showed that the maximum color and COD removal depends on the adsorbent dose and solution pH

Ni/Fe and Mg/Fe layered double hydroxides and their calcined derivatives: preparation, characterization and application on textile dyes removal

In this study, Mg/Fe and Ni/Fe layered double hydroxides (LDHs) with molar ratio (M2+/Fe3+) of 3 and intercalated with carbonate ions were synthesized by co-precipitation method. The as-synthesized materials and their calcined products (CLDHs) were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analyses (TGA–DTA), transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDX), inductively coupled plasma (ICP) and elemental chemical analysis CHNSO. The materials were used as adsorbents for the removal availability of textile dyes from aqueous solution. Methylene blue (MB) and malachite green (MG), representative of cationic dyes, and methyl orange (MO) representative of anionic dyes were used as model molecules. Adsorption experiments were carried out under different parameters such as contact time, temperature, initial dyes concentration and solution pH. Experimental results indicate that CLDHs had much higher adsorption capacities compared to LDHs. Adsorption kinetic data fitted well the pseudo-second order kinetic model. The process was spontaneous, endothermic for cationic dyes and exothermic for the anionic dye. Equilibrium sorption data fitted the Langmuir model instead of Freundlich model