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  1 - Study of Kinetic and Isotherm Models of Lead Ions from Aqueous Solution by Montmorillonite and Montmorillonite Modified with HDTMA-Br
  Mahboobeh Abolhasani Zeraatkar Hamidreza Rafiei-Sarbijan
  10.30495/wsrcj.2023.73541.11379
  Background and Aim: Because of its high specific surface area and high cation exchange capacity (CEC), as well as its availability and low price, sodium montmorillonite (Mt) is used as an adsorbent for a wide range of pollutants, including heavy metals and organic compo More

  Background and Aim: Because of its high specific surface area and high cation exchange capacity (CEC), as well as its availability and low price, sodium montmorillonite (Mt) is used as an adsorbent for a wide range of pollutants, including heavy metals and organic compounds; but the structure of this type of natural clay, however, is unstable, and usually damaged by harmful substances of sewage liquid in the process of infiltration. The organic surfactant hexadecyltrimethylammonium bromide (HDTMA) was used to modify montmorillonite clay to solve this problem. The next step was to investigate lead removal using modified montmorillonite clay (Mt-H). Method: In this study, sodium montmorillonite organic clays modified with hexadecyltrimethylammonium bromide with a CEC two times greater than clay (Mt-H) were prepared. These modified clays were identified using X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The effect of initial lead concentration on lead adsorption from aqueous solution by two adsorbents (montmorillonite clay and modified montmorillonite clay) was investigated. The lead adsorption process was studied using Langmuir and Freundlich adsorption isotherm models. The mechanisms of lead adsorption were investigated and compared using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. Results: The results showed that the organic surfactant hexadecyltrimethylammonium bromide (Mt-H) successfully modified montmorillonite clay, and the interlayer space of the first order peak in montmorillonite clay increased from 11 to 19.7 Å after modification. According to the findings of this study, increasing the initial concentration of lead increased the amount of lead adsorption (Qi) in both adsorbents, sodium montmorillonite clay (Mt) and modified montmorillonite clay (Mt-H). Surface adsorption of lead in montmorillonite clay (Mt) with the Langmuir model and adsorption in modified montmorillonite clay (Mt-H) with the Freundlich model both showed good agreement with experimental data. According to the results, montmorillonite clay (Mt) adsorbed approximately 40% of the lead ions in the first 80 minutes of the reaction, but surface adsorption of lead by modified montmorillonite clay (Mt-H) reached approximately 40% after 1280 minutes. The maximum monolayer adsorption capacity calculated from the Langmuir model at 30°C in modified montmorillonite clay (Mt-H) was 32.54 mg/g, which was approximately 34% lower than the value obtained in montmorillonite clay (Mt). Surface adsorption in montmorillonite clay (Mt) showed the best fit with the Elovich kinetic model, but modified montmorillonite clay (Mt-H) showed the best fit with the intraparticle diffusion kinetic model. Conclusion: The results showed that adding hexadecyltrimethylammonium organic surfactant to sodium montmorillonite clay reduced its lead adsorption capacity. However, modified clay (Mt-H) adsorbs lead ions more strongly. Manuscript profile