From sawdust waste to high-value hierarchical ceramics-based phase change materials: Efficient dual functional thermal and solar energy storage

Latent heat thermal energy storage(LHTES) technology is gaining extensive attention due to its capability to balance supply and demand mismatch in solar energy utilization. However, phase change material as the core of storing latent heat still suffers from low thermal conductivity and poor shape stability, which severely restricts its practical application. Here, an eco-friendly strategy for achieving high-performance dual functional thermal and solar energy storage is proposed via turning wood processing waste into high-value hierarchical porous SiC ceramic-based composite phase change materials. The porosity of prepared porous SiC skeletons is highly adjustable from 59.4% to 90.2%, overcoming low porosity limitations of traditional wood materials and enabling tunable energy storage density for various applications. High thermal conductivity is achieved by benefiting from large grains and continuous skeletons with a value up to 37.93 and 1.87 W/(m K) for porosity of 59.4% and 90.2%, respectively.Excellent stabilities are demonstrated with only slight decreases of thermal conductivity and energy storage density over 1000 cycles and good anti-leakage properties are confirmed due to capillary adsorption forces induced by hierarchical pores. Benefiting from high thermal conductivity and high solar absorptance, fast and efficient solar thermal energy storage is successfully demonstrated. This work provides a new strategy for the high-value utilization of wood processing waste and efficient thermal/solar energy storage.

Rapid conversion of alkaline bauxite residue through co-pyrolysis with waste biomass and its revegetation potential

The extreme alkalinity of bauxite residue(BR)leads to difficulty with its reuse.Alkaline leachate and dust generation during the stacking process can pollute surrounding soil,air and water.In this work,co-pyrolysis of bauxite residue and sawdust was applied to rapidly produce a soil-like matrix that met the conditions for plant growth as demonstrated by ryegrass pot experiments.The present study aimed to characterize the detailed changes in physicochemical,mineral weathering,and microbial communities of the pyrolyzed BR with different ratios of saw dust after plant colonization for 2 months.With increasing sawdust addition during co-pyrolysis,the pH of BR decreased from 11.21 to 8.16,the fraction of macro-aggregates 0.25-2 mm in the water-stable agglomerates increased by 29.3%,and the organic carbon concentration increased from 12.5 to 320 mg/kg,whilst facilitating the degree of humification,which were all beneficial to its revegetation performance.The backscattered electron-scanning electron microscope-energy-dispersive X-ray spectrometry(BSE-SEM-EDS)results confirmed the occurrence of sodalite and calcite weathering on aggregate surfaces,and X-ray photoelectron spectroscopy(XPS)results of surface Al and Si compounds identified that some weathering products were clay minerals such as kaolinite.Furthermore,bacterial community composition and structure shifted towards typical soil taxonomic groups.These results demonstrate soil development of treated BR at an early stage.The technique is a combination of alkalinity regulation and agglomerate construction,which accelerates soil formation of BR,thus proving highly promising for potential application as an artificial soil substitute.