# Transformation of glass fiber reinforced epoxy from waste printed circuit boards to adsorbents for effective CO2 storage in abandoned mines

## TL;DR

This paper explores how waste printed circuit boards can be transformed into materials for capturing CO2, using methods like ultrasonication and chemical treatment.

## Contribution

A novel valorization route for FR-4 PCBs combining KOH/urea activation with ultrasonication and PEI functionalization is proposed.

## Key findings

- Ultrasonication increased BET surface area and CO2 uptake by reducing particle size.
- PEI functionalization improved CO2 affinity but caused pore blockage.
- CO2 uptake correlates strongly with microporosity and total BET area.

## Abstract

Waste printed circuit boards (PCBs) pose environmental challenges due to their toxic and varied composition. Current recycling methods prioritize metal recovery, leaving non-metallic fractions (NMFs) underutilized. These NMFs can be converted into nitrogen-doped porous carbons with good CO2 adsorption capacity. However, waste PCBs are dominated by the FR-4 type in which fibers comprise a large mass fraction and intrinsically limit carbon yield and accessible porosity. We report a targeted valorization route for FR-4 NMFs that couples one-step KOH/urea activation with post-treatments aimed at the glass-fiber/polymer composite: (i) aqueous ultrasonication to increase the surface area by enhancing surface roughness and fragmenting particles to smaller sizes, and (ii) amine functionalization with polyethylenimine (PEI) to improve CO2 affinity. Ultrasonication significantly increased BET surface area (from 444 to 928 m2 g−1) and CO2 uptake (from 1.34 to 1.90 mmol g−1), primarily through particle size reduction. PEI functionalization increased isosteric heat of adsorption (indicative of stronger CO2 affinity) but concurrently caused pore blockage, lowering net adsorption capacity. Quantitative analysis across all samples shows that CO2 uptake correlates strongly with microporosity and total BET area, weakly with external surface area. We discuss mechanistic roles of cavitation-driven fragmentation and glass-fiber/carbon interplay. Our findings suggest ultrasonication is a promising method for enhancing PCB-derived porous carbons in carbon capture applications, while PEI functionalization needs further optimization to balance affinity and accessibility.

Ultrasonication enhances surface area and CO2 uptake of FR-4 PCB-derived porous carbons, while PEI functionalization increases CO2 affinity with porosity trade-offs.