Noureddine Hamdi

In this work, a low-cost activated carbon derived from walnut shells (WSAC) was developed through pyrolysis coupled with chemical activation using ZnCl₂. The preparation process was statistically optimized using the Box–Behnken design (BBD) to assess the influence of impregnation ratio, carbonization time, and carbonization temperature on the textural properties of the material. The optimal conditions, predicted by Design Expert, corresponded to a carbonization temperature of 450 °C, a carbonization time of 90 min, and an impregnation ratio of 1:1 (w/w). Under these conditions, the WSAC achieved a high specific surface area of 873 m²/g and a total pore volume of 0.490 cm³/g, indicating a predominantly mesoporous structure. The physico-chemical properties of WSAC, including thermogravimetric analysis, crystalline structure, morphology, functional groups, and surface area, were investigated using various techniques such as TGA-DTG, SEM, XRD, FTIR, pHZPC, and BET analysis. The adsorption behavior of paracetamol (PCT) from aqueous solution was systematically evaluated as a model pharmaceutical contaminant. The effects of solution pH, temperature, initial concentration, and adsorbent dosage were investigated. The adsorption data were best described by the Langmuir isotherm, with a maximum monolayer adsorption capacity of 62.06 mg.g-1, while the kinetic results followed a pseudo-second-order model (R2 = 0.999). It was found that the adsorption mechanism involves hydrogen bonding and phi–phi interactions. Thermodynamic parameters revealed that the adsorption process is spontaneous and exothermic. These results show that WSACs can be an efficient adsorbent for the removal of PCT or other pharmaceutical pollutants from water. Copyright © 2027 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Wellbore instability in clay-rich intervals remains a major drilling challenge, even when the selected fluid density satisfies the conventional pressure window. This study evaluates delayed instability during exposure to a low-salinity water-based drilling fluid using outcrop-derived Aleg and El Haria materials as analogs for clay-rich Tunisian drilling intervals. Mineralogical, chemical, geotechnical, and shear strength data were integrated with a coupled stability analysis to link fluid exposure, pore pressure redistribution, effective stress modification, and hydration-induced strength degradation. The two materials exhibited contrasting hydro-mechanical behavior. El Haria is clay-rich, with 80% total clay mineral content, including 41% smectite and 47% illite/smectite mixed layers, and has a swelling pressure of 2112 kPa. Aleg is more carbonate-influenced, with 66% total clay mineral content, 28% calcite, and a lower swelling pressure of 576 kPa. Freshwater hydration strongly reduced the shear strength envelope; between approximately 15% and 45% water content, cohesion decreased by approximately 91% in Aleg and 70% in El Haria. The stability profiles show that El Haria reached r_c/a = 1.10 after 0.3 h and the critical threshold of r_c/a = 1.30 after 21.7 h, whereas Aleg remained close to r_c/a = 1.03. This defines a practical temporal stability window for planning open-hole exposure during logging, casing, and cementing operations.

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.

Groundwater salinization and nitrate contamination pose serious threats to water resources in many agricultural regions worldwide. This study investigates groundwater quality and evaluates its suitability for drinking and irrigation in the Sidi Smail Plain (northwestern Tunisia) using geochemical, statistical, modelling and GIS-based approaches. A total of 59 groundwater samples and four surface water samples were collected during the autumn transition (October 2021) and dry summer season (August 2022) and analysed for pH, electrical conductivity, total dissolved solids and major ions. Most groundwater samples were brackish to saline, with average TDS values of 2.225 mg/L in autumn and 2.381 mg/L in summer. Increased salinity during summer was attributed to enhanced evaporation and reduced rainfall. Spatial variability was pronounced, with higher mineralization in the southern plain linked to dissolution of Triassic evaporites and lower values in the north due to dilution from rainfall infiltration and karstic formations. Water Quality Index (WQI) values ranged from 45 to 281, classifying groundwater from excellent to very poor quality. The integrated use of geochemical tools, statistical analysis, WQI and GIS mapping provides a robust framework for assessing seasonal and spatial groundwater quality variations in sub-humid to semi-arid agricultural regions and highlights the need for controlled fertilizer use to protect groundwater from nitrate pollution.

This study aims to investigate the effects of acidic phosphate solution (PS) from phosphogypsum collected from the Tunisian Chemical Group in Gabes, with a pH of 2.6, on the physico-chemical and mechanical properties of Tunisian clay soils, Aleg (AG) and El Haria (EH). Here, the feasibility of employing these soils as natural impermeable barriers for phosphogypsum (PG) disposal sites has been explored. Mineralogical and chemical compositions of raw and modified clays were identified using XRD and XRF. The contact effect of phosphoric aqueous waste in comparison to tap water on raw clays, was revealed by a clear disappearance of the carbonate peak. The drained shear strength of Aleg soil decreased to 48 kPa. Conversely, the cohesion of El Haria soil increased with phosphate solution. Triaxial test results showed c’ and φ’ decreased to 44 kPa and 21° for AG and increased to 155 kPa and 27° for EH. AG and EH clays showed an important support capacity that reached 38 m and 57 m, respectively.

Finding eco-friendly products that are beneficial to the environment and serve as tools for sustainable development is a contemporary challenge. This work illustrates the recovery of bio-waste-based materials, which not only improve the hygrothermal properties of gypsum but also promote the paper and wood recycling processes in a circular economy approach. The samples were subjected to tests for density, water absorption, ultrasonic pulse velocity, flexural strength, compressive strength, and thermophysical property characterization. A statistical analysis of variance was used to study the impact of waste on the physico-mechanical behavior of gypsum, leading to the development of predictive models that can be used to predict and optimize the performance of bio-composites in various applications. The results revealed a reduction in mechanical strength with the addition of waste, but the samples still exhibit superior insulation properties, surpassing commonly used standard boards. By adding ouate and wood wastes to a mass of 20% in its natural state, the gypsum becomes lighter and acts as a better insulator with a reduced density, thermal conductivity, and ultrasound velocity of up to 50%, 57%, and 83%, respectively. These findings show the significant implication of reducing environmental impacts while contributing to the promotion of sustainable building practices, both in new construction projects and in building renovations.