Guar Gum Hydrogel as a Biosorbent for Cd(II) and Cu(II) Ions: Kinetic, Equilibrium, and Thermodynamic Insights

Abstract

Abstract The effectiveness of modified guar gum ( Cyamopsis tetragonoloba ) as a Cd(II) and Cu(II) adsorbent in aquatic media was investigated. Synthesis of modified guar gum based on copolymerization with 2‐Acrylamido‐2‐methyl‐1‐propane sulfonic acid and acrylamide in presence of methylene bis‐acrylamide as a cross linker and in the form of hydrogel adsorbent. Various analytical techniques were employed to describe the surface morphology of the modified adsorbent. Adsorption tests were carried out under different conditions of adsorbent dose (10–50 mg), Cd(II) and Cu(II) initial concentration (25–150 mg/L), pH (1.0–7.0), temperature (∼25–55 °C), and time (∼15–120 min). The maximum uptakes (88 and 82 mg/g) were achieved at pH 6.0 and 5.0 for cadmium (II) and copper (II) ions, respectively. For both metal ions, the kinetics data for the adsorption process obeyed a pseudo second‐order rate equation ( R 2 = 0.9814 and 0.9845, respectively). The adsorption isotherm data were described using 3 models. Thermodynamic parameters such as enthalpy ( ∆H ), entropy ( ∆S ), and Gibbs free energy ( ∆G ) changes were calculated. Cadmium and copper ions adsorption on modified guar gum was discovered to be endothermic and non‐spontaneous. For both metal ions, 5 M HCl and 1 M EDTA were utilized as de‐sorbents, with the latter having a higher desorption efficiency. The prepared hydrogel was proved as an effective promising adsorbent at capturing cadmium and copper ions from laboratory wastewaters and it could be used for further treatment of other effluent wastes.