Refining hydrogel-based sorbent design for efficient toxic metal removal using machine learning-Bayesian optimization

Hydrogel-based sorbents show promise in the removal of toxic metals from water. However, optimizing their performance through conventional trial-and-error methods is both costly and challenging due to the inherent high-dimensional parameter space associated with complex condition combinations. In this study, machine learning (ML) was employed to uncover the relationship between the fabrication condition of hydrogel sorbent and their efficiency in removing toxic metals. The developed XGBoost models demonstrated exceptional accuracy in predicting hydrogel adsorption coefficients (K_d) based on synthesis materials and fabrication conditions. Key factors such as reaction temperature (50–70 °C), time (5–72 h), initiator ((NH₄)₂S₂O₈: 2.3–10.3 mol%), and crosslinker (Methylene-Bis-Acrylamide: 1.5–4.3 mol%) significantly influenced K_d. Subsequently, ten hydrogels were fabricated utilizing these optimized feature combinations based on Bayesian optimization, exhibiting superior toxic metal adsorption capabilities that surpassed existing limits (logK_d (Cu): increased from 2.70 to 3.06; logK_d (Pb): increased from 2.76 to 3.37). Within these determined combinations, the error range (0.025–0.172) between model predictions and experimental validations for logK_d (Pb) indicated negligible disparity. Our research outcomes not only offer valuable insights but also provide practical guidance, highlighting the potential for custom-tailored hydrogel designs to combat specific contaminants, courtesy of ML-based Bayesian optimization.