New Framework Identifies Sustainable Adsorbents for Water Treatment with Net-Zero Potential

A new study published in Frontiers of Environmental Science & Engineering proposes an integrated framework for selecting sustainable adsorbents that align with net-zero objectives in water treatment. The research addresses the environmental burden of conventional activated carbons, which are typically derived from fossil-based feedstocks and involve energy-intensive processing. By combining adsorption performance testing with life cycle assessment and end-of-life analysis, the framework identifies materials that simultaneously achieve high contaminant removal efficiency and reduced greenhouse gas emissions.

The study, reported by researchers from Kyung Hee University on August 23, 2025, focuses on bio-based activated carbons derived from pine bark as renewable alternatives to coal-derived materials. The team synthesized activated carbons using five different chemical activation strategies and found that dual activation with sodium hydroxide followed by hydrochloric acid produced the most effective adsorbent. This material demonstrated a maximum humic acid adsorption capacity of 15.84 mg per gram, significantly outperforming both singly activated biochars and commercially available activated carbons.

To assess environmental impact, the researchers applied life cycle assessment using both mass-based and adsorption-capacity-based functional units. While mass-based comparisons showed similar carbon footprints across several activation methods, performance-based assessment revealed a clear advantage for the dual-activated adsorbent. Because less material was required to remove the same amount of contaminant, its greenhouse gas emissions and cumulative energy demand per unit of pollutant removed were the lowest among all candidates. The study identified electricity use during drying and pyrolysis as major environmental hotspots in the production process.

The analysis further demonstrated that industrial-scale production could reduce carbon emissions per kilogram of adsorbent by nearly 90% compared with laboratory-scale synthesis. End-of-life scenarios were also evaluated, showing that regenerating spent adsorbents offers substantial emission savings relative to landfilling or incineration. This finding reinforces the value of circular material strategies in achieving sustainability goals. The researchers emphasize that evaluating adsorbents solely on adsorption capacity or production emissions provides an incomplete picture of sustainability, and that performance-based life cycle metrics better reflect real-world environmental benefits.

The proposed multi-factor selection framework offers a practical tool for researchers, engineers, and policymakers seeking sustainable water treatment solutions. By aligning adsorption efficiency with life cycle performance and end-of-life considerations, the approach supports informed decision-making for low-carbon material deployment. The findings suggest that bio-based activated carbons, when optimally designed and regenerated after use, can significantly reduce the environmental footprint of water purification systems. The framework can be extended to other functional materials where performance and sustainability must be jointly optimized, contributing to broader net-zero and circular economy goals. The study is available at https://doi.org/10.1007/s11783-025-2068-6.