Efficient Removal of Co(II) Ions from Aqueous Solutions Using Polyampholyte Resin: Synthesis, Properties, and Performance

This paper presents the properties of a novel polyampholyte resin synthesized through the phosphinomethylation of diethylenetriamine. The resin, derived from inexpensive and safe building blocks, avoids the typical crude-oil resin matrix, such as poly(DVB), offering a notable advantage over commercially available solutions. Moreover, the synthesis process is straightforward and environmentally benign, aligning with the principles of sustainability and environmental protection. The primary objective of this study was to evaluate the efficiency of Co(II) ion removal from aqueous solutions using the synthesized resin under both static and kinetic conditions. Key parameters, including the initial metal ion concentration, pH, temperature, contact time, and resin dosage, were systematically investigated. A comprehensive mathematical analysis of static, kinetic, and thermodynamic parameters confirmed the effectiveness of the polyampholyte resin in removing Co(II) ions from aqueous solutions. Data analysis using the Langmuir isotherm model revealed a maximum sorption capacity of 191.7 mg/g at 328 K. Kinetic data were assessed using pseudo-first order, pseudo-second order, and Elovich kinetic models, while the Weber-Morris model was employed to determine the rate-controlling step in the Co(II) ion removal process. The results indicated that the removal of Co(II) ions follows a pseudo-second-order kinetic model, suggesting chemisorption as the dominant mechanism, with diffusion identified as the rate-controlling step according to the Weber-Morris model. Thermodynamic analysis demonstrated that the removal of Co(II) ions is spontaneous and endothermic (Delta H = 24.83 kJ/mol), with efficiency increasing at higher temperatures. Desorption studies using various reagents showed that 2 M H2SO4 achieved the maximum desorption of Co(II) ions (98%). The high ion removal efficiency and ease of regeneration make the synthesized resin a competitive alternative to currently available commercially adsorbents. Notably, the use of this novel polyampholyte resin represents a significant advancement in environmental protection (through reduced reliance on crude oil derivatives) and water treatment (via the removal of toxic ions).