Water pollution is regarded as a dangerous problem that needs to be resolved right away. This is largely due to the positive correlation between the increase in global population and waste production, especially food waste. Hydrogel beads based on sodium alginate (Alg) and pomegranate fruit peels (PP) were developed for the adsorption of Safranin O dye (SO) in aqueous solutions. The obtained Alg−PP beads were widely characterized. The effects of the contact time (0–180 min), initial concentration (10–300 mg/L), initial pH (2–10), adsorbent dosage (1–40 g/L) and the temperature (293–333 K) were investigated through batch tests. The data proved that the adsorption kinetics of SO reached equilibrium within 30 min and up to 180 min. The dye adsorption is concentration dependent while a slight effect of pH was observed. The adsorption data of SO onto synthesized beads follow the pseudo second-order model. The experimental data fitted very well to Langmuir model with correlation factor of 0.92 which demonstrated the favourable nature of adsorption. The maximum adsorption capacity of Alg−PP could reach 30.769 mg/g at 293 K. Calculation of Gibbs free energy and enthalpy indicated that adsorption of SO onto Alg−PP is spontaneous (negative ΔG) and endothermic (ΔH = 9.30 kJ/mol). Analysis of diffusion and mass transport phenomena were presented. The removal efficiency was found to be 88% at the first cycle and decreased to 71% at the end of the seventh cycle. The reported results revealed that the Alg−PP beads could be used as a novel natural adsorbent for the removal of high concentrated solutions of Safranin O which is a cationic dye from liquid affluents and as future perspective, it can be used to remove various pollutants from wastewater.

In this study, an efficient and cost-effective nanocomposite material based on Opuntia ficus indica (cactus) powder modified with iron oxide nanoparticles was developed as an adsorbent for the removal of methylene blue (MB), a common water pollutant. The nanocomposite was synthesized through the co-precipitation method of Fe²⁺ and Fe³⁺ ions and characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA). Batch adsorption experiments were conducted over 24 h, varying different operational conditions, such as pH, temperature and initial pollutant concentration. Furthermore, a Box–Behnken design was employed to develop an empirical model for predicting removal efficiency and optimizing the adsorption conditions. The effects of adsorption variables including contact time (1–60 min), initial MB concentration (20–100 mg/L), pH (2–12), adsorbent dosage (2–6 g/L) and temperature (25–55 °C) on the removal capacity were examined. Under optimal conditions, the maximum removal efficiency of MB reached approximately 96%, with a maximum adsorption capacity of 174 mg/g, as predicted by the Langmuir model. The synthesized cactus/iron oxide nanocomposite demonstrated significant potential as an adsorbent for treating MB-contaminated water.

This work proposes the fabrication of a novel adsorbent based on agro-waste resources with functional adsorption properties to remove a recalcitrant pollutant, such as Nimesulide, from water effluents. An aerogel system, produced through supercritical carbon dioxide drying, was made of cactus powder and 1-ethyl-3-methylimidazolium dicyanamide ionic liquid. The use of ionic liquid allowed to obtain a 3D porous structure showing a mean pore size of 0.12 μm. Its incorporation into cactus-based aerogel improved the adsorption capacity, allowing a drug removal of 88% compared to pristine aerogel, which showed a removal capacity of 15%. Different parameters such as temperature, contact time, pH, initial drug concentration, adsorbent dosage, and salt presence were changed, and their effects on the removal of Nimesulide were assessed. According to the Langmuir model, the maximum adsorption capacity is q_m = 109.9 mg/g, while the kinetic data obeyed the pseudo-second-order model. The reusability tests proved that the adsorbent can be reused for up to 10 cycles without significant adsorption performance loss.