A Comparative Study of Removal of CR(III) from Contaminated Water Using Ribose, Valine and Their Mixture as Facilitating Agents on Selected Adsorbents

Abstract

Adsorption of Cr(III) and Cr(III)-ligands (ribose and valine) on selected adsorbents Celite, Bentonite, Cellulose, Activated carbon (AC), and Carbon Nanoparticles (CNP) studies showed that clay-based materials and cellulose poorly adsorbed the Cr(III). Conversely, carbon adsorbents exhibited increased adsorption for Cr(III) complexed with ligands. Notably, carbon nanoparticles (CNP) remained the most efficient adsorbent (867.05 ppm) with valine complexed Cr(III), suggesting its porous structure could accommodate the larger complex. The Cr(III)-ribose-valine complex displayed an intermediate adsorption capacity, implying the smaller valine ligand partially counteracts the steric effect caused by ribose. XRD analysis confirmed the formation of crystalline structures for all Cr(III)-CNP and Cr(III)-ligand complexes. SEM images provided visual evidence for stronger interactions between the CNP and metal and metal-ligand complexes. TGA-DTA revealed a multi-step decomposition process for the Cr(III)-ligand complexes, with complete removal around 670°C, suggesting a well-defined crystalline structure between Cr(III) and both ligands. Complexation of Cr(III) with ligands significantly increases its adsorption on various materials. While clay and cellulose are less effective, carbon adsorbents offer some degree of adsorption even with the bulky complex. The size and geometry of the complex play a crucial role in its adsorption behaviour.