Cyanoguanidine-Modified Chitosan as an Efficacious Adsorbent for Removing Cupric Ions from Aquatic Solutions: Kinetics, Isotherms, and Mechanisms

One of the most critical environmental needs is to remove metal ions from industrial wastewater. In this investigation, chitosan modified by cyanoguanidine (CCs) was employed for the first time to adsorb cupric ions. The optimal conditions for eliminating cupric ions were adsorbent dose = 0.015 g, cupric ion concentration = 0.2 g L−1, pH = 6, and temperature = 25 °C. The adsorption kinetics fit the pseudo-second-order model, showing a value of correlation coefficient (R2) of 1.00, which is the highest. The experimental qe value was determined to be 99.05 mg g−1, which is comparable to 100 mg g−1 (the theoretical one). The adsorbent’s removal efficacy was 96.05%, and the adsorption isotherms, which conform to the Freundlich model, show that adsorption is multi-layered and homogeneous. The chemosorption and physisorption processes are major factors in the elimination of copper ions. Therefore, a good approach to generate an appropriate efficient adsorbent, which is a good alternative approach in cupric ion elimination, is to incorporate cyanoguanidine, which possesses additional binding sites for cupric ions between chitosan chains. Further, the mechanism of Cu2+ adsorption onto CCs was proposed on the basis of FTIR analysis and computational studies.