An organo-zeolite was prepared by loading hexadecyltrimethylammonium (HDTMA) onto clinoptilolite and was used to remove ceftriaxone sodium and paracetamol in aqueous solutions. Batch experiments were ...conducted to perform kinetics and sorption isotherms at 25 °C and 100 rpm. The results indicate that the equilibration times were 24 h for ceftriaxone sodium and 9 h for paracetamol. Furthermore, sorption capacities were 0.7288 and 0.0058 mg/g, respectively. The data were treatment with different models including pseudo first order, second order, and Elovich, the results suggested a chemical adsorption mechanism, and the adsorption equilibrium data for the two drugs show that they follow a linear trend, indicating a partitioning mechanism. Physicochemical properties such as solubility, log Kow, and pka play an important role in the adsorption process. Finally, the values obtained for zero charge point (ZPC) for zeolitic materials were 6.90, 6.94, and 6.90 for natural zeolite (ZN), sodium zeolite (ZNa), and zeolite modified surface at 30 mM HDTMA (ZMS-30), respectively.
•A novel multi-sensor infrared non-dispersive was developed.•The new multi-sensor NDIR was probed to measure carbon dioxide (CO2) and methane (CH4) from river sediments in situ.•A gas extraction ...chamber was designed and built based on the biogas yield under the extraction by ultrasound.•The specific methanogenic activity was measured to evaluate the biogas yield.
A novel multi-sensor infrared non-dispersive was developed and used to measure carbon dioxide (CO2) and methane (CH4) from river sediments. The infrared filters were developed considering the bandwidth (BW) and central wavelength (CWL) of the infrared spectra of gases. Experiments were performed using sediments from the Lerma River taken during the rainy and dry seasons in order to determine the dimensions of sensor and the gas concentration detection limits (SPAN). The sensor and the extraction chamber dimensions were determined based on the biogas yield under the extraction by ultrasound and specific methanogenic activity (SMA), while SPAN values were established from the results of gas concentration measured by gas chromatography. The volume of sensor was 2.23 mL and selected SPAN values were fixed to 20% for CH4 and CO2 from the calibration and the gas obtained from sediments.
Clindamycin (CLD), an antibiotic derivate of lincomycin, is widely used; the presence of this drug in the wastewater and the environment could produce resistance in bacteria. In this work, the ...sorption of this drug by two surfactant-modified zeolitic tuffs was studied considering contact time, initial concentration, pH, and temperature. The kinetic behavior indicates that the equilibrium times were between 15 and 12 h for all materials, and the results were best adjusted to Ho and Mc Kay model. The highest adsorption was obtained with the hexadecyltrimethylammonium-modified zeolitic tuff from Oaxaca, Mexico (1.56 mg/g). The sorption isotherms obtained showed a linear behavior, indicating a partition mechanism. The thermodynamic parameters were determined from the isotherms at different temperatures and Van Ho equation; the processes are exothermic and not spontaneous. The best pH for the adsorption is between 8 and 11. The results show that the modified zeolitic tuffs are potential materials for the adsorption of CLD from water.
A hybrid system of a sequential oxic-anoxic bioreactor and a fluidized immobilized cell carbon oxidation with Kaldnes K1 as supporting material and activated carbon were used to evaluate the removal ...efficiencies for biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from domestic wastewater collected at the entrance of the biological reactor from a municipal wastewater treatment plant. The laboratory-scale hybrid biofilm treatment system was fabricated with 5 mm acrylic sheets, the effective volume of the system was 31.6 L. The operation of the treatment system was carried out with an optimal hydraulic retention time of 31.33 h and flow rate of 15 mL/min for 170 d at a mean temperature of 20°C, the pH of the wastewater was between 6.54 and 7.50, and a variable organic loading rate from 0.077 to 1.13 kg BOD5/(m3 d) depending on the daily influent wastewater to the wastewater treatment plant. The means removal efficiencies in the 170 d of operation achieved for BOD5, COD, TN, TP were between 84%–99%, 80%–97%, 24%–97% and 21%–94%, respectively.
Natural magnetite ore (Fe3O4) was modified incorporating aluminum and lanthanum ions to increase the fluoride removal efficiency from aqueous solutions. The modified magnetite samples show excellent ...fluoride removal efficiencies of 90 and 96% respectively.
Display omitted
•Natural magnetite ore was used to remove fluoride ions.•Behavior of fluoride on modified magnetite with aluminum and lanthanum ions was evaluated.•Experimental data indicated chemisorption mechanism on a homogeneous material.•Aluminum and lanthanum modified magnetite show excellent fluoride removal efficiencies.•All experimental data was analyzed using isotherm and kinetic models.
Natural magnetite ore (Fe3O4) was modified with aluminum and lanthanum ions to increase the fluoride removal efficiency from aqueous solutions. The modified and unmodified magnetite samples were characterized by X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), infrared spectroscopy (IR), surface area (BET) and zeta potential (ζ). The adsorption and stability of fluoride on magnetite were investigated using modified magnetite in batch systems. The SEM results indicate the formation of a lanthanum oxide layer around the magnetite and that aluminum oxide is dispersed between the particles. Al and La were deposited as hydroxides (IR), which increased the surface area by 7.5 and 9.5 times higher than natural magnetite and shifted the surface potential toward positive values. The IR results indicated that fluoride replaces a hydroxyl group from the aluminum hydroxides whereas no such replacement was detected for materials with La. Batch tests showed that adsorption increased from 30 to 90% and 96% for the aluminum and lanthanum modified materials, respectively.
The behavior of praseodymium in a forest soil with different quantities of organic matter was investigated. The forest soil (FS) was treated with acid and alkali solutions to separate the soluble ...organic matter (fulvic and humic acids) (IM-FS), and then IM-FS was treated with hydrogen peroxide (IM-FS(b)). The materials (FS, IM-FS, and IM-FS(b)) were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM)-EDS, and Fourier-transformed infrared spectroscopy (FT-IR). The points of the zero charge (PZC) and the organic carbon percentages were also determined. The effect of the organic matter, contact time, praseodymium concentration, temperature, and praseodymium desorption were evaluated. The minerals found in the materials were quartz, albite, and kaolinite; the PZC were 6.12, 7.28, and 6.11 for FS, IM-FS, and IM-FS(b), respectively, and their organic carbon percentages were 9.1 ± 0.1, 7.2 ± 0.6, and < 0.1, respectively. The adsorption kinetic data for FS and IM-FS were best adjusted to the pseudo second-order model, and the isotherms data to the Langmuir–Freundlich model indicating a chemical adsorption mechanism on heterogeneous materials, the maximum adsorption capacities were 18.53, 12.98 mg/g and virtually negligible for FS, IM-FS, and IM-FS(b) respectively. The adsorption processes were exothermic; the desorption processes showed that praseodymium is more stable in FS than IM-FS, and Na
2
H
2
EDTA was the best desorbent agent. The adsorption capacities and praseodymium stability depend on the organic matter content. The adsorption capacities followed the order: FS > IM-FS > IM-FS(b).
Abstract
The behavior of composite beads of Zea mays rachis and sodium alginate (AL) for Pb (II) adsorption was studied. The Zea mays rachis–sodium alginate was prepared and characterized. The IR ...spectra showed interactions of the functional groups and the metal ions after adsorption. The kinetic data were fitted to the pseudo-first- and pseudo-second-order models, the maximum adsorption capacity was 60 mg/g for Pb (II), and the isotherm data were best adjusted to the Freundlich model, indicating that the adsorbent is heterogeneous. The thermodynamic study shows that the process is physisorption. The service time of columns increases as the height of columns increases, and this behavior was attributed to the active sites available in the columns. The initial concentration of Pb (II) had a significant effect on the breakthrough curves. As the concentration increases, the saturation time decreases. The material was regenerated four times (adsorption–desorption cycles), without a significant change in the removal efficiencies.
Display omitted
•Al-iron oxides were used for removal of fluoride from solutions and drinking water.•The breakthrough curves could be fitted to Thomas, Bohart–Adams, and BDST.•The results show that ...the adsorption efficiency decreases as the bed depth increases.•The adsorption is controlled by the mass transport resistance.•Adsorption efficiency for fluoride is higher for aqueous solutions than drinking water.
The purpose of this work was to evaluate the potential of aluminum modified iron oxides, in a continuous flow for removal of fluoride ions from aqueous solutions and drinking water. The breakthrough curves obtained for fluoride ions adsorption from aqueous solutions and drinking water were fitted to Thomas, Bohart–Adams, and bed depth service time model (BDST). Adsorption capacities at the breakthroughs, Thomas model constant, kinetic constant and the saturation concentration were determined. The results show that in general, the adsorption efficiency decreases as the bed depth increases, and this behavior shows that the adsorption is controlled by the mass transport resistance. The adsorption capacity for fluoride ions by CP-Al is higher for fluoride aqueous solutions than drinking water.
The composites sodium alginate (AL): Zea mays rachis (ZMR) with different ratios were prepared and tested for the adsorption of lead. The composite with the 1:2 ratio showed the highest adsorption ...capacity for lead, this material was characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy and the zero point charge was determined. The wastewater was taken from one discharge to a marsh and used for the removal of Pb(II), this wastewater was acidified, the solids were allowed to sediment and water was filtered to avoid excessive fouling of the adsorbent material. The kinetic experimental data were best fitted to the pseudo-first-order model and the equilibrium data to linear models. The biosorption process was endothermic, the ΔH value was 49.84 kJ mol–1 and ΔG decreased as increasing the temperature, suggesting a spontaneous process. 96% of initial Pb(II) concentration was removed using an optimal AL:ZMR ratio of 1:2, at pH solution value of 5. The results indicate that the adsorption of lead takes place by chemisorption.
Metronidazole (MNZ) is an antiparasitic that has been found in wastewater. In this paper, the removal of MNZ by using modified zeolitic tuffs with two different surfactants ...(hexadecyltrimethylammonium bromide and benzyl hexadecyl dimethyl ammonium chloride) was studied. These modified materials were characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy and Brunauer–Emmett–Teller analysis. The cation exchange capacities and the points of zero charge were determined. The sorption kinetics show that the equilibrium times for all systems were similar about 15 h, the experimental data were best adjusted to the Ho–McKay model. The isotherms were linear indicating partition mechanism and the maximum adsorption capacity was in the order of 0.5 mg/g with an initial concentration of 20 mg/L of MNZ; the adsorption behavior of MNZ data at different temperatures was exothermic and the maximum adsorption capacity was observed between pH 5 and 6. The results show that the sorption efficiency depends on the origin of the zeolitic tuff and the surfactant used for the modification. These modified materials are effective to remove MNZ from aqueous solutions.
PDF
