Study on the influence of carboxyethyl chitosan concentration on composite fouling characteristics: Experiments, functional group analysis, and molecular dynamics simulations

To explore the scale inhibition characteristics of carboxyethyl chitosan (CEC) on composite fouling, this study employed experimental methods, functional group analysis, and molecular dynamics simulations to investigate the effects of CEC at different concentrations on the inhibition of Al₂O₃ and CaCO₃ composite fouling. The experimental results demonstrate that CEC, obtained through functional group substitution, serves as an environmentally friendly scale inhibitor capable of altering the morphology of composite fouling. Moreover, the scale inhibition efficiency of CEC improves with increasing inhibitor concentration. Under the experimental conditions, the best anti-scaling performance was achieved when the inhibitor concentration was 100 mg/L. Functional group analysis indicates that the carboxyl groups on the CEC molecular chain exhibit a strong adsorption affinity for Ca²⁺. Molecular dynamics simulations reveal that there is a strong interaction between the Ca²⁺ and the carboxyl groups of CEC in solution. CEC's impact on the composite clusters is observed to alter their aggregation state and reduce both the probability and intensity of Ca²⁺ and CO₃^2- adsorption on the particle surface. When the number of CEC molecules (N) reaches 20, the particle no longer adsorbs Ca²⁺; however, some CEC molecules start to bind with the particle, and this interaction becomes more pronounced as the concentration increases. At N = 30, the binding energy between CEC and Ca²⁺ increases to 11,767.9 kcal/mol, while the binding energy between CEC and Al₂O₃ particle rises to 352.6 kcal/mol. This study provides insights into the mechanism by which scale inhibitors suppress composite fouling and offers theoretical guidance as well as novel approaches for addressing composite fouling issues in future research.