Fixed Bed Column Sorption Studies of Diclofenac Sodium (DS) From Aqueous Solution Using Synthesized Novel Organoclay Based On Two Different Amino Acids

Abstract

This study focuses on the removal of Diclofenac Sodium (DS), a common pharmaceutical pollutant found in water sources, using novel adsorbents based on amino acid (protonated forms of L-arginine and L-phenylalanine) functionalized bentonite. Both raw bentonite (BT), L-arginine/bentonite (BTA) and Lphenylalanine/bentonite (BTP) were all characterized using X-ray florescence (XRF) spectroscopy, Brunauer, Emmet and Teller (BET) Surface Area analyzer, Dynamic Light Scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric/differential thermal analysis (TGA/DTA), indicating successful modification with increased surface area and the introduction of vital functional groups, such as the guanidinium group in BTA and aromatic rings in BTP. Continuous fixed-bed column adsorption experiments investigated the influence of various fixed-bed column adsorption experimental conditions such as inlet concentration (5 -20 mg/L), flow rate (2 – 6 mL/min) and bed height (30 -100 mm). The results showed that both organoclays successfully removed DS from aqueous medium, with BTA showing more superiority in adsorption capacity, attributed to an established strong electrostatic interaction between the guanidinium group of the arginine and the DS molecule. Scalability of the entire adsorption process was achieved by effectively modelling Breakthrough curves (BTC) utilizing the Thomas, Yoon-Nelson, and Bohart-Adams models. To complement experimental findings, Density Functional Theory (DFT) calculations provided insights into possible molecular interactions as well as underlying adsorption mechanisms involved in DS removal by the novel organoclay, revealing DS's electronic properties. Therefore, this study validates the potential application of arginine and phenylalaninemodified organoclays as promising, cost-effective, and sustainable adsorbents for continuous pharmaceutical removal from aqueous solutions.