حوريه سادات رضوي

Colored industrial effluents particularly those containing the recalcitrant cationic dye methylene blue (MB) pose a critical threat to water resources. In this research, a natural pozzolan precursor (R-POZ) was modified into two advanced nanoadsorbents: a mechanochemically activated material (MM-POZ) an‎d a thermo-chemical modified derivative (TCM-POZ), targeting accelerated MB uptake an‎d higher equilibrium capacity. A multi-instrument characterization suite established a rigorous structure – composition – function relationship: FTIR indicated enhanced O–H ban‎d intensity in MM-POZ relative to R-POZ an‎d TCM-POZ, consistent with a higher density of hydrogen-bonding/acidic surface sites; XRD revealed progressive narrowing of the quartz (101) reflection accompanied by an increase in crystallite size along the transformation path R-POZ to MM-POZ an‎d then to TCM-POZ; nitrogen sorption (BET/BJH) showed specific surface areas of 6.02 m²·g⁻¹ (MM-POZ) an‎d 10.94 m²·g⁻¹ (TCM-POZ) with mean pore diameters of 37.98 nm an‎d 30.18 nm, respectively; FESEM visualized 2D nanosheets for MM-POZ an‎d TCM-POZ versus a nanoscale but less sheet-like morphology for R-POZ. Electrokinetic analysis further evidenced a more negative effective surface charge (pHzpc shift) for TCM-POZ, favoring electrostatic attraction of cationic MB. Batch adsorption was performed at pH 5.41, 30 °C, with optimized doses of 0.326 g·L⁻¹ (MM-POZ) an‎d 0.366 g·L⁻¹ (TCM-POZ). Under these conditions, equilibrium was reached in 7 min for MM-POZ an‎d 25 min for TCM-POZ, highlighting the kinetic superiority of MM-POZ attributable to greater accessibility of active sites an‎d facilitated mesopore diffusion pathways. Equilibrium data conformed well to both Langmuir an‎d Freundlich isotherms, with Freundlich providing the better fit in the investigated concentration range, consistent with heterogeneous site energies. The Langmuir theoretical capacities (qmax) were 166.23 mg·g⁻¹ for MM-POZ an‎d 126.92 mg·g⁻¹ for TCM-POZ, while the maximum experimental uptakes reached 210.3 mg·g⁻¹ (MM-POZ) an‎d 146.7 mg·g⁻¹ (TCM-POZ). The Langmuir affinity constants (KL) were estimated as 82.87 L·mg⁻¹ (MM-POZ) an‎d 115.3 L·mg⁻¹ (TCM-POZ), reflecting strong dye - surface interactions; the higher KL of TCM-POZ aligns with its more negative Zeta-potential an‎d greater charge-controlled affinity, even though its overall rate is slower than MM-POZ. Kinetic modeling indicated pseudo-second-order control for MM-POZ emphasizing chemisorption-dominated rate behavior whereas intraparticle diffusion contributed substantially to TCM-POZ uptake, in agreement with its more uniform, charge-tuned pore architecture. Post-adsorption FTIR showed attenuation of the O–H ban‎d an‎d subtle ban‎d shifts, signaling specific surface–dye interactions (hydrogen bonding an‎d electrostatic coupling); Zeta-potential measurements confirmed further negative drift for TCM-POZ after adsorption, coherently explaining its elevated Langmuir affinity an‎d robust equilibrium performance. Altogether, both modification routes significantly outperformed the raw precursor: MM-POZ excels kinetically (shortest time-to-equilibrium an‎d highest experimental uptake) owing to high site accessibility an‎d mesopore-facilitated transport, while TCM-POZ excels thermodynamically (higher effective affinity/selec‎tivity an‎d charge tuning), offering enhanced equilibrium stability. These findings provide a clear operational roadmap: mechanochemical activation to unlock rapid mass transfer an‎d site exposure, followed by thermo-chemical tuning to deepen electrostatic/chemical affinity an‎d refine mesostructure. The resulting regenerable, mineral-based nanoadsorbents are technically credible an‎d transferable to real effluent polishing, bridging crystallographic an‎d mesostructural engineering with adsorption thermodynamics an‎d kinetics for scalable water treatment.

جذب سطحي، متيلن بلو، نانو پوزولان، مدل‌هاي سينتيكي و هم‍‌دما، پساب نساجي

Adsorption,Methylene Blue,Kinetic an‎d isothermal models, textile wastewater

Hourieh Sadat Razavi

DR norouzbeigi,Dr Mahinroosta