Synthesis and characterization of chemically functionalized novel smart guar gum xanthate based hydrogel: Swelling, isotherm, kinetics, thermodynamic and reusability studies

Abstract

The eco-friendly smart guar gum xanthate-based hydrogel (GGmXHs hydrogel) has been synthesized using a free radical polymerization process via grafting of two monomers viz., acrylamide and acrylic acid on guar gum xanthate (GGmX) using KPS as an initiator and taking MBA as the crosslinker. Numerous analytical techniques viz., UV, FTIR, GPC, TGA, SEM, XRD, and EDAX analysis have been used to characterize the synthesized GGmXHs hydrogel. The synthesized GGmXHs hydrogel has been utilized to eliminate the Ni²⁺, Co²⁺ and Cu²⁺ ions from aqueous solutions. The optimal removal percentage has been found to be 91.4, 95.1 and 98.0 for Ni²⁺, Co²⁺ and Cu²⁺ ions respectively. In addition, the swelling of GGmXHs hydrogel was obtained to be 313.6, 436.1 and 483.4 g/g and % WRR has been found to be 67.64, 74.34 and 81.28 % in grey, tap and distilled water, at optimized conditions. The Langmuir isotherm has been studied as most fitted with adsorption capacity of 420.16, 448.43 & 471.69 mg/g for Ni²⁺, Co²⁺ and Cu²⁺ ions respectively. The kinetic studies for the adsorption mechanism suggest pseudo-first order kinetic model with rate constant of −3.9 × 10⁻² min⁻¹ for Ni²⁺, −4.8 × 10⁻² min⁻¹ for Co²⁺, and −6.7 × 10⁻² min⁻¹ for Cu²⁺ ions. The reusability of GGmXHs hydrogel has been studied fourth times and the desorption efficiency has been found to be 88.82, 91.38 and 95.01 % for Ni²⁺, Co²⁺ and Cu²⁺ ions respectively. Finally, GGmXHs hydrogel emerges as an economical adsorbent that is efficient to clean heavy metal ions (HMIs) from wastewater.