Glutaraldehyde and Glyoxal Crosslinked Polyethylenimine for Copper Ion Adsorption from Water

The water body can potentially be contaminated with heavy metals such as Cu²⁺ ions which beyond a certain concentration could impact human and animal health. In the past, different techniques have been developed to remove Cu²⁺ ions from water. In this study, polyethlenimine (PEI) was crosslinked with glutaraldehyde and glyoxal to yield three polymers (P1-P3). P3 consists of hydroxypropyl methylcellulose (HPMC) as a template to decrease the size of the crosslinked polymer particles. The polymer powders were used to adsorb Cu²⁺ from CuSO₄ water solutions. The addition of 50, 100 and 150 mg of P3 removed 25, 32 and 38 mg of Cu²⁺, respectively, from 0.075 M (10 mL) of CuSO₄ solution, after stirring at room temperature for 24 h. In comparison, P1 and P2 removed a lower amount. The better performance of P3 arises from the larger surface area of the polymer powder compared to P1 and P2 as revealed from scanning electron microscopy (SEM) images. Kinetic studies indicated that the polymers remove a larger amount of Cu²⁺ during the first 3 h with a slower rate of adsorption continuing until 12 h. The adsorption kinetics were fitted with Elovich and Pseudo second order models to understand the adsorption mechanism. The higher R² (∼0.99) value of the linear plots signifies the adsorption is likely to follow a Pseudo second order kinetics, with P3 showing a rate constant of 8.43x10⁻⁵ g mg⁻¹ min⁻¹. The Cu²⁺ loaded polymers (100 mg) were soaked in 10 mL of 2 % HNO₃ for 24 h for the desorption of Cu²⁺, where 12, 10 and 16 mg of Cu²⁺ desorbed from P1, P2 and P3, respectively. This indicates the polymers could potentially be reused to adsorb another batch of Cu²⁺ from water to maximize an economic benefit.