Temperature and pH influence on Diuron adsorption by Algerian Mont-Na Clay

ABSTRACT

The United States Environmental Protection Agency (EPA) classified the phenylurea herbicide Diuron (C₉H₁₀Cl₂N₂O) as possibly carcinogenic to humans. This research is focused on the adsorbent performances of a Algerian sodium Montmorillonite (Mont-Na), for the removal of Diuron in aqueous solutions. The material is characterised before and after processing using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), specific surface area (S_BET) and thermal analysis (TGA/DTA). The tests were firstly realised at 25°C and pH = 6.3. Until 61 hours of experiment, no removal was obtained in this case. After that, the experiments were carried out on Mont-Na at high temperature and medium pH (T = 45°C, pH = 6.3) and then at ambient temperature and basic pH (T = 25°C, pH = 11). The removal was increased from 74% to 91%, respectively. The equilibrium is reached after 5 hours and the adsorption capacity is between 0.74 mg/g at 45°C and 0.91 mg/g at pH = 11. The kinetic modelling shows that the pseudo-first order describes the experimental data of the Diuron adsorption on Mont-Na and the equilibrium data are modelled perfectly by applying the Elovich model. The thermodynamic quantities indicate that the adsorption process on Mont-Na at pH = 6.3 is spontaneous (ΔG < 0) and endothermic (ΔH = 31.80 kJ.mol⁻¹). In conclusion, under the operating conditions used, local Mont-Na proved to be an excellent material for the adsorption of Diuron in aqueous solutions. That could be very promising for sewage treatment.

KEYWORDS:

• Diuron
• adsorption
• removal
• Mont-Na
• temperature
• pH

Acknowledgments

The Algerian Directorate General of Scientific Research and Technological Development (DGRSDT), and the Algerian Ministry of Higher Education and Scientific Research (MESRS) are greatly thanked for their financial support, even for making it possible to join the Algerian-French doctoral scholarships program: PROFAS B + 2019-2020, in order to accomplish and innovate this research work. The authors would like to thank the collaboration of the Institute of Chemistry of Poitiers (IC2MP) for having facilitated the analysis and characterization techniques.

Disclosure statement

No potential conflict of interest was reported by the author(s).