Modeling of equilibrium isotherms and kinetic studies of Cr (VI) adsorption into natural and acid-activated clays

Khalfa, Leila; Cervera, M. Luisa; Zakaria, Mohamed B.; Souissi-Najar, Souad

doi:10.1007/s12517-015-2104-0

Cited by 20 publications

(14 citation statements)

References 45 publications

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“…Sulfuric acid has the ability to remove the soluble salts and impurities from the surface and interlayers of bentonite, and thus it increases the surface area, porosity, and the number of chitosan loading sites in bentonite [9,15,22]. Figure 7 shows that the chitosan loading onto bentonite first increased and then decreased with the concentration of sulfuric acid (within 3-20 %) used.…”

Section: Effects Of Activation Treatments On the Chitosan Loading Amountmentioning

confidence: 99%

“…The loading of chitosan on bentonite was examined using various reaction times (10-90 min), initial chitosan concentrations (250-2500 mg/L), stirring speeds (50-300 rpm), temperatures (30-50 °C), and pH values (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Specifically, 1 g of raw bentonite clay was dispersed in 150 mL of distilled water.…”

Section: Optimization Of Chitosan Loading Conditionsmentioning

confidence: 99%

“…The white chitosan particles adsorbed onto the surface of chitosan-loaded bentonite (Figures 11(E) and 11(F)) and into the spaces between the clumps of clay cause the surface to become relatively coarser and looser, and the interlayer distances become significantly larger. These morphological changes indicate that: (1) all three activation methods improve the spatial structure of bentonite; (2) chitosan is loaded via surface adsorption and intercalation; and (3) the loading process does not change the basic structure of bentonite [9][10][11][12].…”

Section: Materials Characterizationmentioning

confidence: 99%

“…Acidification, microwave irradiation, and calcination all increase the number of adsorption sites on bentonite and the cation exchange capacity, thus increasing the heavy metal adsorption capacity. Furthermore, the surface of the chitosan-modified clay features many amino and hydroxyl groups, which can form covalent bonds with the heavy metal ions and further improve the adsorption performance [9,27]. Figure 15 shows the removal of Cu(II), Cr(VI), and Pb(II) heavy metal ions (100 mg/L) using chitosan-loaded bentonite at the adsorbent amounts of 0.5, 1.0, 1.5, 2.0, and 2.5 g/L.…”

Section: Adsorption Performance Of Chitosanloaded Bentonite Claymentioning

confidence: 99%

“…low density, the tendency to float, and difficulty in making contact with pollutants [7,8]. On the other hand, various modification techniques, including acid and thermal (by calcination or microwave radiation) treatments, have been reported to affect the adsorption properties of nature clays for metal ions in aqueous solutions [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Bentonite Activation Methods on Chitosan Loading Capacity

Fan

et al. 2017

Bull. Chem. React. Eng. Catal.

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The adsorption capacity of bentonite clay for heavy metal removal from wastewater can be significantly enhanced by a high loading of chitosan on the surface. In order to enhance the chitosan loading, we tested activating bentonite clay by three methods prior to chitosan loading: sulfuric acid, calcination, and microwave treatments. Meanwhile, several parameters during chitosan loading, namely the initial chitosan concentration, stirring speed, reaction time, temperature, and pH value were investigated. Our results indicate that chitosan is attached to bentonite clay through intercalation and surface adsorption according to X-ray Diffraction (XRD), Scanning Eelectron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The maximum chitosan loading on 200-mesh raw bentonite clay (126.30 mg/L) was achieved under the following conditions: the initial chitosan concentration of 1000 mg/L, the stirring speed of 200 rpm, pH of 4.9, 60 min of reaction time, and temperature of 30 °C. The chitosan loading was further increased to 256.30, 233.70, and 208.83 mg/g, when using bentonite clay activated through 6 min of microwave irradiation (800 W), 10 % sulfuric acid treatment, and calcinations at 600 °C, respectively. When the chitosan loading was increased from 34.76 to 233.7 mg/g, the removal percentages of Cu(II), Cr(VI), and Pb(II) were improved, respectively from 78.90 to 95.5 %, from 82.22 to 98.74 %, from 60.09 to 86.18 %.

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Section: Effects Of Activation Treatments On the Chitosan Loading Amountmentioning

confidence: 99%

Section: Optimization Of Chitosan Loading Conditionsmentioning

confidence: 99%

Section: Materials Characterizationmentioning

confidence: 99%

Section: Adsorption Performance Of Chitosanloaded Bentonite Claymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Bentonite Activation Methods on Chitosan Loading Capacity

Fan

et al. 2017

Bull. Chem. React. Eng. Catal.

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Green Synthesis of ZnO Nanoparticles for Efficient Cr(VI) Removal and Antioxidant/Microbial Properties

Naaz,

Fakhar,

Siddiqui

et al. 2024

ChemistrySelect

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The study focuses on fabrication of a cost‐effective Zinc Oxide nanoparticles (ZnONPs) adsorbent using Syngonium podophyllum leaves extract to remove hexavalent chromium (Cr6+) from synthetically prepared wastewater. Various spectroscopic techniques, including X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray analysis (EDX), and transmission electron microscopy (TEM), were used to characterize the ZnONPs. Fourier infra‐red spectroscopy (FTIR) detected that various organic compounds like flavonoids, terpenoids, and carboxylic acids acts as stabilizing and capping agent. The batch adsorption study was conducted to investigate the effects of Cr6+ adsorption time, pH, adsorbent concentration, and initial adsorbate concentration. The maximum adsorption capacity was 267.068 mg/g at 313 K. The Freundlich isotherm model was most suitable, indicating multilayer confiscation of Cr6+ on the heterogeneous surface. Chemisorption was identified as the mechanism of sequestration. Thermodynamic studies revealed that Cr6+ removal was spontaneous and feasible, with ΔG° values suggesting predominantly physisorption. Additionally, ZnONPs displayed strong antibacterial activity against S. aureus bacteria, making them a potential alternative to antibiotics. ZnONPs exhibited impressive antioxidant activity. Overall, ZnONPs synthesized through biosynthesis proved to be excellent nano‐sorbents, antioxidants, and biocompatible materials with promising applications in water remediation and healthcare.

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