Finding a cost-effective adsorbent can be an obstacle to large-scale applications of adsorption. This study used an efficient activated carbon adsorbent based on agro-waste for dye removal. Pistachio shells as abundant local agro-wastes were used to prepare activated carbon. Then, it was modified with iron to improve its characteristics. Acid red 14 was used as a model dye in various conditions of adsorption (AR14 concentration 20–150 mg L−1, pH 3–10, adsorbent dosage 0.1–0.3 g L−1, and contact time 5–60 min). A mesoporous adsorbent was prepared from pistachio shells with 811.57 m2 g−1 surface area and 0.654 cm3 g−1 pore volume. Iron modification enhanced the characteristics of activated carbon (surface area by 33.3% and pore volume by 64.1%). Adsorption experiments showed the high effectiveness of iron-modified activated carbon for AR14 removal (>99%, >516 mg g−1). The adsorption followed the pseudo-second kinetic model (k = 0.0005 g mg−1 min−1) and the Freundlich isotherm model (Kf = 152.87, n = 4.61). Besides, the reaction occurred spontaneously (ΔG0 = −36.65 to −41.12 kJ mol−1) and was exothermic (ΔH0 = −41.86 kJ mol−1 and ΔS0 = −3.34 J mol−1 K−1). Iron-modified activated carbon derived from pistachio shells could be cost-effective for the treatment of industrial wastewater containing dyes.

This study evaluated silica aerogel as an adsorbent for phenol removal from aqueous solutions. Silica aerogel was prepared through the sol-gel process and characterized by different analyses. Then, it was used for phenol removal under various conditions of operational parameters. Also, twelve isotherm parameters were employed to describe the behavior of phenol-silica aerogel adsorption system. The chemical structural analysis confirmed -OH functional groups in amorphous SiO₂ and proved the adsorption of phenol onto the surface of silica aerogel. The findings of the adsorptive behavior of silica aerogel toward phenol showed increasing pH, up to 8.5, and contact time, and adsorbent dose increased the phenol removal. The removal efficiency reached over 90% when phenol concentration was below 50 mg L^-1. The reaction kinetics followed the pseudo-first order model. The isotherm study showed that equilibrium adsorption data were well-described by Freundlich and Halsey equations, among two-parameter isotherms, and Hill, Sips, and Koble-Corrigan, among three-parameter isotherms. Jovanovic and BET were the worst isotherm models for prediction of experimental equilibrium data. The maximum adsorption capacity of 75.23 mg.g^-1 was calculated in phenol-silica aerogel adsorption system. The study showed silica aerogel as an efficient adsorbent to remove phenol from phenol-containing solutions. Keywords: Adsorption; Kinetics; Phenol; Silica Aerogel; Aqueous Solution

Multi-criteria decision-making (MCDM) can introduce the best option based on evidence. We integrated the Analytic Hierarchy Process (AHP) and the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS) to prioritize the alternatives for photocatalytic diazinon removal in a bench scale and characterized TiO₂-MIL-53(Fe) for this purpose. Criteria and alternatives were listed based on systematic literature reviews and expert opinions. Then, AHP and TOPSIS questionnaires were developed and distributed to an expert panel for pairwise comparisons. We converted the linguistic variables into the corresponding fuzzy values and used R for mathematical calculations. Then, TiO₂-MIL-53(Fe) was synthesized and characterized for diazinon removal under LED visible light. The AHP ranked criteria as availability > degradation efficiency > safety for the environment > material cost > energy consumption > mineralization efficiency > photocatalyst reusability > safety for personnel > equipment cost. Based on TOPSIS, the order of alternatives was TiO₂-containing/Visible light > ZnO-containing/UV light > TiO₂-containing/UV light > ZnO-containing/Visible light > WO₃-containing/UV light. With a bandgap of 1.8 eV, TiO₂-MIL-53(Fe) could remove 89.35% of diazinon at 10 mg/L diazinon concentration, 750 mg/L catalyst dose, pH 6.8, and 180-min reaction time. Hybrid AHP-TOPSIS identified the best option for photocatalytic diazinon removal from aqueous solutions. Thus, MCDM techniques can use systematic review results to overcome the uncertainty in designing experimental studies.