Evaluating the metal recovery potential of coal fly ash based on sequential extraction and machine learning

Given the depletion of metal resources and the potential leaching of toxic elements from solid waste, secondary recovery of metal from solid waste is essential to achieve coordinated development of resources and the envi-ronment. In this study, hybrid models combining the gradient boosting decision tree and particle swarm opti-mization algorithm were constructed and compared based on two different datasets. Additionally, a new, quantitative evaluation index for metal recovery potential (MRP) was proposed. The results showed that the model constructed using more elemental properties could more accurately predict metal fractions in coal fly ash (CFA) with an R2 value of 0.88 achieved on the testing set. The MRP index revealed that the DAT sample had the greatest recovery potential (MRP = 43,311.70). Ca was easier to recover due to its high concentration and presence mostly in soluble fractions. Model post-analysis highlighted that the elemental properties and total concentrations generally exerted a greater influence on the metal fractions. The innovative evaluation strategy based on machine learning and sequential extraction presented in this work provides an important reference for maximizing metal recovery from CFA to achieve environmental and economic benefits with the goal of sus-tainable development.

Automated summary

Given the depletion of metal resources and potential leaching of toxic elements, it is crucial to recover metals from solid waste for sustainable development. This study constructed hybrid models using gradient boosting decision trees and particle swarm optimization algorithms and proposed a new evaluation index for metal recovery potential. The results showed that the model with more elemental properties accurately predicted metal fractions in coal fly ash, and the DAT sample had the highest recovery potential. The innovative evaluation strategy provides an important reference for maximizing metal recovery from coal fly ash.