Deciphering peroxydisulfate vs. peroxymonosulfate activation by biochar catalysts via explainable machine learning

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment Technologies

Background:

• Biochar (BC) activated persulfate advanced oxidation processes (PS-AOPs), using peroxymonosulfate (PMS) and peroxydisulfate (PDS), are effective for removing water contaminants.
• A lack of systematic comparison between PMS and PDS activation by biochar hinders catalyst design and process optimization.

Purpose of the Study:

• To systematically compare the catalytic behavior and pollutant removal performance of PMS and PDS activated by non-metal-doped biochar.
• To utilize machine learning (ML) to investigate the distinct activation mechanisms and identify key biochar properties and experimental conditions for optimizing PS-AOPs.

Main Methods:

• Development of distinct ML models for PMS and PDS activation by non-metal-doped biochar.
• Application of SHAP analysis to determine feature importance for both oxidants.
• Classification of contaminants by degradability using ionization potential and development of contaminant-directed sub-models.

Main Results:

• PMS activation is primarily influenced by experimental conditions (71.3% importance), while PDS activation is more dependent on biochar properties (70.1% importance).
• Key biochar properties (physico-porous structure, surface elements, preparation) and their optimal ranges were identified for each oxidant.
• Contaminant degradability was classified, enabling targeted mechanistic analysis and optimization strategies.

Conclusions:

• ML analysis provides mechanistic insights into PMS and PDS activation by biochar, highlighting distinct influencing factors.
• Optimal biochar design strategies require tuning specific parameters like biomass precursor, surface area, and defect degree based on the oxidant-contaminant combination.
• This study offers guidance for developing efficient, sustainable, and tailored biochar catalysts for pollutant-specific water treatment.