Valorization of Rice Husk Waste for CO<sub>2</sub> Capture and Utilization

Pinto, Ingrid S.; Duarte, Evandro A. C.; Santos, Leonardo dos; Faria, Douglas; Bernard, Franciele L.; Einloft, Sandra

doi:10.21577/0103-5053.20260029

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Full Paper • J. Braz. Chem. Soc. 37 • 2026 • https://doi.org/10.21577/0103-5053.20260029 linkcopy

Valorization of Rice Husk Waste for CO₂ Capture and Utilization

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Global challenges such as health crises, rising sea levels, deforestation and biodiversity loss are linked to climate change, which is primarily caused by carbon dioxide (CO₂) emissions. To address these issues, research into CO₂ capture and reuse has gained prominence. Abundant, non-toxic to humans and inexpensive, CO₂ is a promising raw material for energy and material production. However, converting CO₂ into value-added products requires innovative approaches, such as the development of synthetic materials and catalytic processes. This study focuses on the use of silica extracted from rice husk ash, an agricultural residue comprising 20% of raw rice mass, as a support for metals such as cobalt (Co) and iron (Fe). The supported materials were evaluated for CO₂ sorption and their catalytic performance in the direct synthesis of dimethyl carbonate (DMC) from methanol and CO₂. Comprehensive characterization techniques, including field emission scanning electron microscopy (FE-SEM), surface area analysis (Brunauer Emmett Teller (BET) method), Fourier transform infrared spectroscopy with universal attenuated total reflectance (FTIR UATR), solid-state nuclear magnetic resonance (NMR-MAS), temperature-programmed oxidation-reduction (TPO), and temperature-programmed desorption (TPD), were employed. Catalytic performance was assessed using a Shimadzu GC 2014 gas chromatograph. The best CO₂ sorption capacity was achieved with the sample Si-Co 10% (100 mg CO₂ g^-1) at 30 bar and 25 °C. The best conversion to DMC was for the sample Si-Fe 10% (22.91%), at 80 °C and 40 bar of CO₂. This study demonstrates the potential of repurposing agricultural waste to extract silica and utilize it as a metal catalyst support, offering a promising solution for both CO₂ capture and conversion.

Keywords:
silicate; CO₂ adsorbent; conversion; DMC

Sample	T_onset / °C
Sample	1^st degradation	2^nd degradation	3^rd degradation
Si	137.53	680.16
Si-Fe 5%	140.43	548.35
Si-Fe 10%	447.32	562.42	645.71
Si-Co 5%	129.41	555.92
Si-Co 10%	434.92	561.13	629.55

Sample	Diameter at 10% / µm	Diameter at 50% / µm	Diameter at 90% / µm	Average diameter / µm
Si	14.52	60.69	122.69	66.29
Si-Fe 5%	3.13	20.94	65.85	28.16
Si-Fe 10%	2.16	14.47	41.84	19.20
Si-Co 5%	2.06	13.34	69.22	24.67
Si-Co 10%	1.77	11.16	32.66	13.95

Sample	BET / (m² g^-1)	Pore volume / (cm³ g^-1)	Average pore radius / nm	Density / (g cm^-3)
Si	64 ± 0.5	0.385 ± 0.003	11.887 ± 0.002	3.021
Si-Fe 5%	44 ± 0.3	0.168 ± 0.004	1.721 ± 0.003	2.609
Si-Fe 10%	48 ± 0.6	0.225 ± 0.002	1.721 ± 0.004	2.638
Si-Co 5%	72 ± 0.4	0.348 ± 0.004	11.815 ± 0.002	2.028
Si-Co 10%	90 ± 0.6	0.389 ± 0.003	11.807 ± 0.003	2.117

Sample	Temperature / °C	Pressure / bar	Sorption / (mg CO₂ g^-1)	Reference
Si-Fe 10%	25	4	36.38 ± 0.32	this work
Si-Co 5%	25	4	41.50 ± 0.55	this work
Si-Co 10%	25	4	42.98 ± 0.52	this work
Si-Co 10%	25	30	100.56 ± 0.33	this work
Oliseed rape straw	25	1	26.53	Cao et al.⁸²
Wheat straw	25	1	32.00	Cao et al.⁸²
Rambutan peel	30	-	27.83	Zhang et al.⁸³
ILBF₄M50	25	4	20.00	Aquino et al.⁸⁴
ILTf₂NM50	25	4	20.00	Aquino et al.⁸⁴
CL-TBA	25	30	71.00	Bernard et al.⁸⁵

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Valorization of Rice Husk Waste for CO2 Capture and Utilization

Abstract

Valorization of Rice Husk Waste for CO₂ Capture and Utilization