Abstract:BACKGROUND: Layered double hydroxide compounds (LDHs) have been applied for the removal of oxyanions including arsenate (As(V)). However, the aim of this present research is to develop a LDH to treat arsenite (As(III)). Both batch and column sorption studies were conducted to assess the effect of LDH dosage, contact time, solution pH and initial As(III) concentrations on the As(III) removal performance. The potential re-use of this sorbent was also investigated.
“…4a and 4b inserted) is obtained using the BJH method based on a discrete analysis of the desorption branch of the isotherm. It is seen that the pore diameters are 38.36 Å and 53.25 Å for RCG and CCG, respectively, indicating a mesoporous structure [48].Fig. 4N 2 adsorption/desorption isotherms of RCG (a) and CCG (b).…”
Section: Resultsmentioning
confidence: 94%
“…H3 type hysteresis is a characteristic of porous solids whose size, distribution and pore shape are not uniform. The specific surface area (Table 2) obtained by the B.E.T method [48] is 25.35 m 2 /g and 62.20 m 2 /g for RCG and CCG, respectively. The distribution of the pore diameters (Fig.…”
In this work, the phenols removal of phenol from water by raw clay (RCG) and calcined one at 1000 °C (CCG) of Goulmima city (Morocco) was investigated. The kinetics and isotherms experiments were also studied at pH = 4. The results indicated that the phenol adsorption reached equilibrium within 3 h, and the removal of phenol was enhanced at the same temperature by CCG (2.932 mg/g) adsorbent, compared to RCG (1.640 mg/g) due to the removal of organic matter by heat treatment, and an increase in adsorption temperature, indicating the endothermic process. The adsorbents were characterized by means of X-ray fluorescence, FTIR, XRD, B.E.T, and TGA/DTA analysis and showed that the clay consists essentially of silica and alumina. The experimental data were examined by using linear and nonlinear forms of the kinetics and the isotherms models. Based on the errors of the calculated values of R
2
(Coefficient of determination), χ
2
(Chi-square) and standard deviation (Δq (%)), it was found that the nonlinear forms of second-order kinetic model and Freundlich and Redlich-Peterson (R–P) isotherm models are best fit the experimental data for both adsorbents. However, the enthalpy ΔH° is less than 20 kJ/mol and the free energy ΔG° has a negative value, which shows that the adsorption is done physically and spontaneously on heterogeneous sites. The interest of this study is the use of FTIR and XRD to determine the effect of calcination on the phenol adsorption mechanism. However, the analysis of both adsorbents, before and after adsorption of phenol, shows that the adsorption mechanism of phenol is provided by the hydrogen bonding of the water molecules.
“…4a and 4b inserted) is obtained using the BJH method based on a discrete analysis of the desorption branch of the isotherm. It is seen that the pore diameters are 38.36 Å and 53.25 Å for RCG and CCG, respectively, indicating a mesoporous structure [48].Fig. 4N 2 adsorption/desorption isotherms of RCG (a) and CCG (b).…”
Section: Resultsmentioning
confidence: 94%
“…H3 type hysteresis is a characteristic of porous solids whose size, distribution and pore shape are not uniform. The specific surface area (Table 2) obtained by the B.E.T method [48] is 25.35 m 2 /g and 62.20 m 2 /g for RCG and CCG, respectively. The distribution of the pore diameters (Fig.…”
In this work, the phenols removal of phenol from water by raw clay (RCG) and calcined one at 1000 °C (CCG) of Goulmima city (Morocco) was investigated. The kinetics and isotherms experiments were also studied at pH = 4. The results indicated that the phenol adsorption reached equilibrium within 3 h, and the removal of phenol was enhanced at the same temperature by CCG (2.932 mg/g) adsorbent, compared to RCG (1.640 mg/g) due to the removal of organic matter by heat treatment, and an increase in adsorption temperature, indicating the endothermic process. The adsorbents were characterized by means of X-ray fluorescence, FTIR, XRD, B.E.T, and TGA/DTA analysis and showed that the clay consists essentially of silica and alumina. The experimental data were examined by using linear and nonlinear forms of the kinetics and the isotherms models. Based on the errors of the calculated values of R
2
(Coefficient of determination), χ
2
(Chi-square) and standard deviation (Δq (%)), it was found that the nonlinear forms of second-order kinetic model and Freundlich and Redlich-Peterson (R–P) isotherm models are best fit the experimental data for both adsorbents. However, the enthalpy ΔH° is less than 20 kJ/mol and the free energy ΔG° has a negative value, which shows that the adsorption is done physically and spontaneously on heterogeneous sites. The interest of this study is the use of FTIR and XRD to determine the effect of calcination on the phenol adsorption mechanism. However, the analysis of both adsorbents, before and after adsorption of phenol, shows that the adsorption mechanism of phenol is provided by the hydrogen bonding of the water molecules.
“…The calculated maximum adsorption capacities of the product for As(III) and As(V) using the Langmuir equation are 15.90 mg/g and 10.48 mg/g, respectively. The adsorption amounts of As(III) and As(V) of the product and the adsorbents reported in previous studies [13][14][15][16][17] are shown in Table 5. The product in this work indicated a high adsorption amount compared to that by the adsorbents reported in previous publications.…”
In Japan, biomass power generation is being promoted for effective biomass utilization. However, a major problem is the large amount of biomass combustion ash discharged and disposed of as industrial waste. Environmental problems caused by arsenic (As) occur throughout the world, including Japan. In this study, we attempted to synthesize an Fe-type layered double hydroxide (Fe-LDH) from biomass combustion ash for As removal. During this experiment, the combustion ash was added to HCl to dissolve divalent cations, Ca and Mg, in the ash, and then filtrated. Iron chloride hexahydrate (FeCl 3 •6H 2 O) was added to the filtrate to prepare an acidic liquid mixture with a molar ratio of (Ca+Mg)/Fe = 2-2.5, which was added to 0.3 M NaCl solution and stirred for 6 h to synthesize LDH at 20, 40, and 60°C maintaining a pH 8.5, 10.5, and 12.5, respectively. In addition, the As removal ability of the product was investigated. As a result, the product, including Fe-LDH, prepared from the biomass combustion ash at pH 12.5 at 40 o C demonstrated a strong ability to remove arsenite (As(III)) and arsenate (As(V)), and the removal percentage of As(III) using the product was higher than that of As(V).
“…LDHs, also known as hydrotalcites, are a class of two-dimensional anionic intercalation materials with a bimetallic hydroxide laminate and exchangeable intercalation anions [ 13 ]. They are widely applied in adsorption, catalysis [ 14 , 15 , 16 ], energy storage [ 17 , 18 ], biology [ 19 ], medicine release [ 20 , 21 , 22 ], heavy metal ions [ 23 , 24 ], and functional materials [ 25 , 26 , 27 , 28 ]. Their general formula can be given by (M 2+ 1−x M 3+ x (OH) 2 ) (A n− ) x/n ·mH 2 O [ 29 ].…”
The increasing threat of chloride ions (Cl−) has led researchers to explore efficient removal technologies. Sewage treatment with a double-layer hydroxide/oxide (LDH/LDO) is receiving increasing attention. In this work, Mg-Al LDO adsorbents were produced by the calcination of the Mg-Al LDH precursor, which was constituted by improved coprecipitation. The influence of calcination temperature, calcination time, adsorbent dosage, Cl− initial concentration, contact time, and adsorption temperature on Cl− elimination was investigated systematically. The experimental results showed that a better porous structure endowed the Mg-Al LDO with outstanding adsorption properties for Cl−. The adsorption process was well matched to the pseudo-second-order kinetics model and the Freundlich model. Under optimal conditions, more than 97% of the Cl− could be eliminated. Moreover, the removal efficiency was greater than 90% even after 11 adsorption–desorption cycles. It was found that the electrostatic interaction between Cl− and the positively charged Mg-Al LDO laminate, coupled with the reconstruction of the layer structure, was what dominated the Cl− removal process.
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