# Sargassum biochar from Taiyuan captures 120.5 mg CO₂ per gram in laboratory tests

- Published: 2026-11-06 03:22 UTC
- Section: Machines & Making › Materials science
- Tags: Sargassum biochar, CO₂ adsorbent, KOH activation before pyrolysis, carbon capture material, Biochar X, regeneration cycles, microporous biochar
- URL: https://realtech.media/news/rt-6c1e641980406c5b139f56e9_sargassum_biochar_from/

**A Taiyuan University of Science and Technology team treated Sargassum with KOH before pyrolysis at 400 °C. The lab adsorbent kept 98.9% of its capacity after nine cycles.**

A team led by Lina Liu at Taiyuan University of Science and Technology has made a reusable CO₂ adsorbent from the seaweed Sargassum tenerrimum. The study was published in Biochar X on 27 July 2026 [1]. Biomass treated with potassium hydroxide (KOH) before pyrolysis at 400 °C gave the sample Sar-KOH, which captured 120.5 mg of CO₂ per gram at 313 K (40 °C) [1]. According to the release, this is five times the capacity of untreated biochar prepared at the same temperature. After nine regeneration cycles the material retained 98.9% of its initial capacity [1]. The results were obtained in the laboratory.

## Sample preparation and testing

The researchers washed, dried and ground the seaweed. They then heated the powder under nitrogen at 400, 500, 600 or 700 °C for two hours. To test the effect of treatment order, they compared KOH mixed with the biomass before heating at 400 °C against KOH applied to biochar after an initial heating step [1].

Morphology, surface area and pore size were examined by electron microscopy and gas adsorption. Surface chemistry was probed by infrared spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed CO₂ desorption. CO₂ uptake was measured by thermogravimetry at 40 °C and one bar with dry, pure CO₂. Regeneration was performed under nitrogen at 120 °C.

## Capacity, pores and cycling

Raising the temperature alone increased surface area but did not consistently improve capture. Untreated biochar adsorbed 24.1 mg/g when prepared at 400 °C, and 20.2, 10.9 and 16.5 mg/g at 500, 600 and 700 °C. KOH applied after initial carbonization raised uptake to 40.0 mg/g, and KOH applied before carbonization gave 120.5 mg/g [1].

The specific surface area of Sar-KOH was 569.66 m²/g, against 1.14 m²/g for untreated biochar prepared at 400 °C. Pore analysis showed many narrow pores, with a prominent width near 0.6 nm. The authors attribute the performance to physical adsorption in these micropores, together with hydroxyl groups that bind CO₂ by hydrogen bonding [1].

Sar-KOH reached adsorption equilibrium in about 11 minutes, compared with 26–28 minutes for untreated samples. Its capacity declined by 1.1% over nine cycles. The authors note that humid conditions, gas mixtures and selectivity remain to be tested, and that the powder must be shaped into durable particles or structures suitable for reactors.

## Sources

1. [Biochar X](https://doi.org/10.48130/bchax-0026-0019)
2. [EurekAlert](https://www.eurekalert.org/news-releases/1150691)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-6c1e641980406c5b139f56e9_sargassum_biochar_from/