Preparation And Study Of The Properties Of Sodium Alginate-Coated Nanoscale Montmorillonite Clay For The Removal Of Organic Dyes

Ayman Ali Hussein

Authors

Ayman Ali Hussein Chemistry Department / Division of Pure Sciences and Agricultural Sciences / Maragheh University / Iran

Keywords:

organic synthesis, sodium alginate, montmorillonite, adsorption mechanisms, statistical optimization

Abstract

This study presents an advanced organic synthetic approach for the preparation of a hybrid nanocomposite consisting of montmorillonite (MMT) coated with sodium alginate (SA) for the removal of organic dyes from water. The synthetic route was designed to rely on specific organic interaction mechanisms, including directed hydrogen bonding between hydroxyl groups in the alginate and the surface silanol chains of the clay, as well as multi-site ionic coordination interactions according to the Egg-box model using calcium ions as cross-linking agents, which enabled the formation of a three-dimensional polymer network that stabilizes the clay sheets and prevents their agglomeration. The biosynthesis conditions were optimized using a factorial design (2³ FFD), where the results showed that the highest chemical coupling yield reached 94.31% at an alginate concentration of 2.0%, pH = 4.0, and a temperature of 55°C. FT-IR and XRD characterization techniques confirmed the occurrence of distinctive functional shifts, manifested as a 15 cm⁻¹ shift in the carboxyl band and a 5.43 Å increase in the interplanar spacing (d₀₀₁), reflecting the success of the intercalation process and the formation of stable coordinate bonds. Principal component analysis (PCA) revealed that the carboxyl group contributes 32.1% to the total variance, confirming its pivotal chemical role. A response surface methodology (RSM) and Box-Behnken design were applied to optimize the adsorption process, where the compound achieved a removal efficiency of 98.12% for methylene blue dye at pH = 10.0, with an experimental maximum adsorption capacity of 230.46 mg/g. Nonlinear modeling demonstrated the superiority of the Langmuir model (χ²=0.042, RMSE=0.015) and the pseudo-second-order model (R²=0.9992), confirming that the adsorption process proceeds via a monolayer chemical mechanism at energetically homogeneous sites, while the thermodynamic parameters (ΔG°=-25.75 kJ/mol, ΔH°=+14.11 kJ/mol) confirmed the spontaneity of the process and its endothermic nature. The integrated results demonstrate that the developed hybrid nanocomposite represents an advanced functional platform with high chemical stability and superior adsorption capacity, making it a sustainable strategic solution in green chemistry applications for the treatment of industrial wastewater contaminated with refractory organic dyes.

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