Bioinspired Lignin-Aluminosilicate Composite for CO2 Storage

Abstract

In the effort to decarbonize hard-to-abate industries, the issue of CO₂ emissions from the cement production process must be addressed, primarily due to the calcination reaction and high-temperature requirements. To achieve a sustainable process to produce carbon-neutral construction materials, utilizing nature-abundant resources without relying on calcium oxide chemistry or sintering could be a promising approach. Here, a new method is presented to prepare construction material by strengthening highly abundant kaolinite clay with Kraft lignin at 100 °C. Due to the electrostatic interactions between Kraft lignin and kaolinite particles, the resulting lignin-aluminosilicate composite displayed compressive strengths of up to 20 MPa. Additionally, the simultaneous use of kaolinite and smectite enabled the fabrication of a strong composite, which could store up to 10 g of CO₂ per 1 kg under high-pressure CO₂ treatment at room temperature. Furthermore, the scalability of the proposed method to real-sized bricks and artworks was demonstrated, thereby opening new pathways toward a carbon-negative construction industry.

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Schematic illustration of the fabrication process and global distribution of raw materials. (a) A scheme comparing the proposed brick-making process with the conventional geopolymerization reaction. The process enables brick fabrication by directly mixing clay powder with a Kraft lignin solution, imparting CO₂ storage capacity through high-pressure CO₂ treatment. (b) Global map illustrating the distribution of kaolinite and smectite in the subsoil layer by location. Adapted from the data set compiled by Ito and Wagai, under a Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). (c) The global pulp market share distribution by type of pulp mill and the theoretical maximum and current production of Kraft lignin, calculated from the current global Kraft pulp mill capacity (Mt: million tons). Reproduced with permission from ref . Copyright 2020 Elsevier.

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Molecular structure and compressive strength of clay minerals. (a) Crystal structure of kaolinite and smectite clay minerals. The basic particle shape of each clay mineral and the crystal structure of each layer are illustrated, with green representing the tetrahedral sheet (T sheet) and yellow representing the octahedral sheet (O sheet). (b) Compressive strength of kaolinite and smectite bricks as a function of NaOH content (0, 1, 2.5, 5, 10 wt %). (c) XRD spectra of kaolinite and smectite bricks, comparing the spectrum of bricks made without NaOH to those with 10 wt % NaOH content. Peaks corresponding to hydrosodalite are marked with red asterisks.

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Lignin-enabled compressive strength enhancement of lignin-clay brick. (a) Compressive strength of kaolinite bricks with and without lignin. The dark orange bars represent the compressive strength of lignin-kaolinite (LK) bricks with varying lignin contents (2, 4, 6, 8, 10 wt %), while the light orange bars represent the compressive strength of kaolinite bricks containing NaOH in the amounts needed to dissolve the corresponding lignin contents. (b) Compressive strength of smectite bricks with and without lignin. The dark blue bars represent the compressive strength of LK bricks with varying lignin contents (2, 4, 6, 8, 10 wt %), while the light blue bars represent the compressive strength of smectite bricks containing NaOH in the amounts needed to dissolve the corresponding lignin contents. (c) Full FT-IR spectra of LK brick and kaolinite brick. The lignin content in the LK brick is 50 wt %, and the NaOH content in the kaolinite brick corresponds to the amount required to dissolve 50 wt % lignin. The two smaller graphs show a magnified view of the spectra in the areas highlighted by the yellow boxes. (d) Compressive strength of bricks as a function of kaolinite-to-smectite ratio (100:0, 75:25, 50:50, 25:75, 0:100) and lignin content (0, 2, 4, 6, 8, 10 wt %), represented by color. The color of each point indicates compressive strength, ranging from 1 to 20 MPa, as indicated by the scale bar on the right. (e) High-resolution TEM image and diffraction pattern of the kaolinite-smectite brick, where the orange areas represent kaolinite, and the blue areas represent smectite. Scale bars, 20 nm (TEM image), 2 nm^–1 (diffraction pattern).

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CO₂ storage capacity of lignin-clay brick. (a) Full XRD spectra of the lignin-kaolinite-smectite (LKS) brick before and after CO₂ treatment. The smaller graph shows a magnified view of the spectra in the area highlighted by the yellow box. (b) Time-dependent CO₂ uptake changes of lignin-Ca²⁺-smectite (LS­(Ca)) brick and LS brick following high-pressure CO₂ treatment. (c) XRD spectra of Na⁺-smectite powder and Ca²⁺-smectite powder (2θ = 3–25°). (d) Time-dependent CO₂ uptake changes of lignin-kaolinite-Ca²⁺-smectite (LKS­(Ca)) brick, LS­(Ca) brick, and LK brick following high-pressure CO₂ treatment.

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Fabrication process and potential applications of lignin-clay bricks. Digital photographs of real-sized bricks and artworks. (a) Process for fabricating lignin-clay bricks. Lignin solution is poured onto clay powder, then homogeneously mixed into a paste and molded into the desired shape. (b) Real-sized brick made from lignin, kaolinite, and smectite. (Length of the ruler: 150 mm) (c) Artworks made from lignin and kaolinite, inspired by the presence of lignin in wood, shaped to resemble tree bark.