In the present research, zeolite is used for the removal of toxic Congo red dye from water solution. The effects of different operating conditions such as hydrogen potential (pH), contact time (time), zeolite dose (D), initial dye concentration (C₀), and ionic strength (I) are investigated for Congo red adsorption under batch mode. It was found that the adsorption process was greatly affected by the initial pH of the dye solution. The removal efficiency decreased from 97.68 to 5.22% when the pH varied from 3 to 5; thus, acidic conditions clearly improve Congo red adsorption on zeolite. At pH 3, an increase in C₀ and I and decrease in D resulted in an increase in the adsorption capacity q_e. The effects of these three parameters and their interactions were also investigated using the 2³ full factorial design experiments approach where q_e was chosen as the response. The results obtained from this method followed by the analysis of variance and the Student’s t-test show that, the influence of these parameters on dye adsorption process are in the order I < C₀ < D. The kinetic studies revealed that adsorption follows a pseudo-second-order kinetic model. The adsorption isotherms experimental data were analyzed using the Langmuir, Freundlich, and Temkin isotherms models. The Freundlich isotherm was the best-fit model to the experimental data. The fitting of kinetics and isotherm models was evaluated by using non-linear modeling, R², MSE, and RMSE.

Algerian kaolinite, sourced from Djebel Debbagh nuance 3 (DD3), was used as a low-cost adsorbent to remove methylene blue (MB) dye from water. Its adsorption capacity was enhanced through sulfuric acid treatment (treated-DD3). In response to the urgent demand for clean water, various technologies have been developed to address dye removal from wastewater. This study, specifically delving into the treatment of textile wastewater, examined the efficacy of treated-DD3 through adsorption processes. The acid treatment increased the surface area and pore volume of DD3. X-ray diffraction showed crystalline phases in both, with treated-DD3 having higher crystallinity. Fourier-transform infrared spectroscopy found no significant differences post-acid treatment. Scanning electron microscopy revealed DD3 had large, stacked particles with low surface area, while treated-DD3 had increased porosity and a smoother surface. Various parameters affecting MB adsorption were studied. The Langmuir and Freundlich models were used for isotherm parameters. Treated-DD3 exhibited a higher MB adsorption capacity (64.58 mg/g according to the Langmuir model) than DD3 (44.48 mg/g). Thermodynamic analysis indicated spontaneous and endothermic MB adsorption onto both DD3-BM and treated-DD3-BM systems under different pH conditions. Treated-DD3 effectively reduced chemical oxygen demand (from 304.056 mg/L to 34.44 mg/L) and biological oxygen demand (from 80 mg/L to 20 mg/L) in real textile wastewater. The adsorbent exhibited rapid removal and decolorization, surpassing 93% within the first 7 min of the experiment. The Gaussian process regression and particle swarm optimization (GPR–PSO) predicted MB adsorption capacity effectively (R = 0.9989, R² = 0.9978, adj-R² = 0.9978, RMSE = 1.1390, and MAE = 0.3926).

This research aimed to assess the adsorption properties of raw walnut shell powder (WNSp) for the elimination of methylene blue (MB) from an aqueous medium. The initial MB concentration (2–50 mg/L), the mass of the biomaterial (0.1–1 g/L), the contact time (10–120 min), the medium’s pH (2–12), and the temperature (25–55 °C) were optimized as experimental conditions. A maximum adsorption capacity of 19.99 mg/g was obtained at an MB concentration of 50 mg/L, a medium pH of 6.93 and a temperature of 25 °C, using 0.2 g/L of WNSp. These conditions showed that the MB dye elimination process occurred spontaneously. Different analytical approaches were used to characterize the WNSp biomaterial, including functional groups involved in MB adsorption, the surface characteristics and morphological features of the WNSp before and after MB uptake, and identification of WNSp based on their diffraction pattern. The experimental isotherm data were analyzed by the Langmuir and Freundlich models for the adsorption of MB dye. The corresponding values of parameter R_L of Langmuir were between 0.51 and 0.172, which confirmed the WNSp’s favorable MB dye adsorption. The experimental kinetic data were examined, and the pseudo-second-order model was shown to be more suitable for describing the adsorption process, with an excellent determination coefficient (R² = 0.999). The exchanged standard enthalpy (H° = −22.456 KJ.mol⁻¹) was calculated using the van ‘t Hoff equation, and it was proven that the adsorption process was exothermic. The spontaneous nature and feasibility of the MB dye adsorption process on WNSp were validated by negative standard enthalpy values (G°) ranging from −2.580 to −0.469 at different temperatures. It was established that WNSp may be employed as a novel, effective, low-cost adsorbent for the elimination of methylene blue in aqueous solutions.

Due to their cost-effectiveness, low toxicity, and naturally renewable properties, bio-coagulants for water treatment are gaining popularity. In this context, four bio-coagulants were tested for their ability in turbidity reduction in a synthetic bentonite suspension: Opuntia ficus indica (OFI) and Moringa oleifera (MO) seeds, two well-established vegetal materials in the domain of bio-coagulation, and Algerian Aloe vera (AV) and Pinus halepensis seeds (PHS), both of which have received very few or no study in turbidity reduction in water and wastewater. A comparative study was conducted with regard to two well-known inorganic coagulants, ferric chloride and Alum. Extraction salts, pH, coagulant dose, initial turbidity, and aging effects were examined. When compared to chemical coagulants, the four bio-coagulants worked very well, removing approximately 100% of the turbidity at natural pH of 7.5 using optimal doses of 1.5, 3, 3, 3.5, 1.5, and 1.5 mL/200 mL for AV, OFI, MO, PHS, Alum, and FeCl₃, respectively, at a broad range of pH (2 to 8), and causing no pH alteration of the treated water. Polysaccharides and proteins involved in inter-particle bridging and charge neutralization may be the active coagulation-flocculation molecules. The four bio-coagulants produced less sludge amount than Alum and Ferric chloride. This research not only shows that MO and OFI are effective in eliminating turbidity, but it also highlights the great potential of Algerian AV and PHS seeds as promising bio-coagulants in the treatment of polluted water.