New insight into cell wall pore structure in brown-rotted wood and its utilization as a new low-cost, sustainable adsorbent

Brown-rotted wood is a substantial agroforestry waste produced by the economic fungal cultivation industry, which lacks further utilization. This study evaluated the degradation process and structural properties of brown-rotted wood (spruce and masson pine) obtained from different decay times (0, 4, 6, 10, and 14 weeks) from the perspective of pore structure. The adsorption performance and application potential of the brown-rotted wood for methylene blue (MB) were analyzed based on its structure and properties. The results showed that hemicellulose and cellulose were significantly degraded by brown-rot fungi, disrupting the compact structure of the cell wall and creating pores, especially in earlywood. In the initial stage (4 weeks), the degradation of the amorphous component increased the pore proportion of 5–10 nm size, which was conducive to enzymatic hydrolysis by improving the enzyme's diffusion in the cell walls. The nitrogen adsorption analysis showed that the specific surface area and pore volume of the brown-rotted wood increased with decay processing. The surface areas of the brown-rotted wood were the largest at 14 weeks, which were 35.83 cm2/g (brown-rotted spruce) and 32.98 cm2/g (brown-rotted pine), respectively. The increase in the surface areas of the brown-rotted wood provided more space for adsorbing MB, of which, the adsorption capacity reached 48.22 mg/g and 44.58 mg/g, twice higher than the sound wood. The exploration of the interaction between cell wall matrix degradation and pore structure development provided new insight to elucidate the degradation mechanism of brown-rotted wood, and a vital basis for improving the adsorption efficiency of the brown-rotted wood as a new low-cost, sustainable adsorbent.