Mohamed Mezni

The valorization of phosphogypsum (PG), a byproduct of phosphoric acid production, along with waste glass (WG) and silica fume (SF) into value-added materials has attracted growing attention in recent years. The present study aims to synthesize three types of porous geopolymers (GD, GDP, and GDG) using Tunisian clay and locally available mineral wastes, and to investigate their potential as low-cost adsorbents for the removal of methylene blue (MB) dye from aqueous solutions. The physicochemical characteristics of the raw precursors and the resulting porous geopolymers were analyzed using various techniques, including FTIR, XRD, BET, and SEM. Variations in Si/Al, Na/Al, and Ca/Al ratios play a critical role in the geopolymer structure. The high Ca/Al ratio in GDP (porous geopolymer from calcined clay and phosphogypsum) promotes the formation of C-A-S-H, leading to increased macroporosity, which favors adsorption capacity despite the presence of a more heterogeneous morphology. The results indicated that the maximum adsorption capacity (Qmax) for MB dye was obtained for the GDP sample, reaching 68 mg/g. Adsorption experiments revealed the successful removal of MB dye by geopolymers, with the Langmuir isotherm and pseudo-second-order kinetic models adequately describing the adsorption process. The MB uptake by geopolymers was facilitated by weak physicochemical interactions, including electrostatic attraction, hydrogen bonding, and π–π interactions. This study proposes a simple and effective alkali activation strategy that combines different industrial wastes within a single geopolymer system, resulting in improved porosity and adsorption efficiency. Overall, the findings highlight the potential of these waste-derived geopolymers as promising and sustainable adsorbents for wastewater treatment applications.

Enrofloxacin uptake and removal from aqueous solutions using illite and synthetic zeolite X prepared from illite, were studied in batch experiments under varying pH, contact time, and initial enrofloxacin concentrations. The X-ray diffraction and Fourier transform infrared spectroscopy caracterization were used to analyse the enrofloxacin adsorption in order to elucidate the adsorption mechanisms. It was found that enrofloxacin could be efficiently removed at pH 7 and pH 8 for clay and zeolite X, respectively. In addition, the second order model of kinetics is more adopted for the two samples. The isotherms of adsorption of enrofloxacin by illite and zeolite X show that the latter has the twice higher adsorption capacity of the clay. Equilibrium data fit well with the Langmuir and Freundlich isotherms. Moreover, the cation exchange, the electrostatic interaction, the cation bridging and the formation of bidentate ligands were the possible mechanisms of the enrofloxacin retention.

The decomposition of penicillin G and erythromycin antibiotics at concentration of 0.2 mg ml⁻¹ by gamma irradiation at 50 kGy followed by biological treatment with Cupriavidus metallidurans CH34 was evaluated. Degradation of penicillin G and erythromycin was analyzed using nuclear magnetic resonance analysis (NMR), fourier transform infrared spectroscopy (FTIR), and chemical oxygen demand (COD). The exposure to the absorbed dose of 50 kGy caused degradation of penicillin G and erythromycin in the aqueous solution. The complete disappearance of NMR and FTIR peaks following irradiation confirmed the breakage of the β-lactam ring in penicillin G, and the decarboxylation and cleavage of the thiazolidine ring and for erythromycin, the complete destruction of the three aromatic rings. Irradiation alone removed 52.8 and 65.5 % of penicillin G and erythromycin, respectively. Further reduction to 12.6 and 14 % of the original penicillin G and erythromycin COD, respectively, was achieved using treatment of the irradiation products with C. metallidurans.