Green synthesis of Cr-BDC@ɣ-Al2O3 granular adsorbents for effective removal of monoethylene glycol (MEG) from industrial wastewater

A novel environmentally friendly approach was developed to synthesize Cr-BDC@ɣ-Al2O3 granular adsorbents for the purpose of removing mono-ethylene glycol (MEG) as an organic pollutant. The synthesis method employed ethanol and water as greener alternatives to dimethylformamide (DMF). Although the granular form of the adsorbent exhibited slightly lower performance compared to the powdered form, it demonstrated superior suitability for separation, regeneration, and industrial applications, such as packed-bed systems. To investigate the influential parameters, the response surface methodology (RSM) was applied, revealing that variations in pH had an insignificant effect on the efficiency of adsorption. The maximum adsorption capacity of 124.45 mg/g was achieved at the highest concentration of the pollutant, attributed to the abundance of pollutant molecules. Based on the RSM results, the optimal conditions for MEG removal were determined as pH 7, a pollutant concentration of 500 ppm, and an adsorbent dosage of 2 g/L. The adsorption kinetics followed the pseudo-quadratic model, with the majority of adsorption occurring within the initial 70 minutes. Thermodynamic studies confirmed the spontaneous and exothermic nature of the adsorption process. The experimental data fitting exhibited good agreement with both the Langmuir and Dubinin-Radushkevich (D-R) isotherms, indicating predominant physisorption and a maximum Langmuir adsorbent capacity of 166.667 mg/g. Additionally, the granular adsorbent demonstrated excellent regeneration capability and remarkable stability even after six consecutive cycles. This study highlights the potential of Cr-BDC@ɣ-Al2O3 granular adsorbents as effective and environmentally friendly materials for the removal of organic pollutants from aqueous systems. [Display omitted] •Green synthesis of Cr-BDC@ɣ-Al2O3 using water and ethanol, replacing DMF as a solvent.•Comparison and optimization of green and conventional solvothermal synthesis methods.•Evaluation of granular and powder forms of adsorbents in MEG removal.•RSM method for optimal operating conditions, achieving a maximum adsorption capacity of 124 mg/g.•Excellent regeneration and stability of the granular adsorbent even after 6 cycles.