Comparative study of KOH and H₃PO₄ activated Lvzhou No. 1-based shape-stabilized phase change materials: Properties and potential application in phosphogypsum

With the continuous growth of global building energy consumption, the development of efficient energy-storage building materials is of great significance to promote the sustainable development of the construction industry. In this study, Arundo donax cv. Lvzhou No.1 (LZ1) was chemically activated using KOH and H₃PO₄ to prepare two activated carbons, denoted as KALZ1 and PALZ1, respectively. These activated carbons were then used as supporting materials and loaded with capric acid-stearic acid eutectic mixture (CA-SA) using vacuum impregnation method. The resulting shape-stabilized phase change materials (SSPCMs) were designated as CA-SA/KALZ1 and CA-SA/PALZ1, corresponding to their respective activated carbon carriers. PALZ1 exhibited superior encapsulation capability with a loading rate of 78.62 %, which was attributed to its larger specific surface area (318.46 m²/g) and uniform pore size (0.827 nm). The thermal conductivity of CA-SA/PALZ1 was 0.406 W/(m·K), which was 98 % higher than the 0.205 W/(m·K) of pure CA-SA. Its latent heat value was 112.87 J/g, and only decreased by 6.50 J/g after 500 thermal cycles, showing excellent thermal performance and thermal stability. Furthermore, CA-SA/PALZ1 was added into phosphogypsum (PG) to prepare energy-storing PG-based composite. At a dosage of 15 wt%, the compressive strength and flexural strength of the composite were increased by 6.18 % and 12.12 % compared with the control group, respectively, with a latent heat value of 18.81 J/g. This study demonstrated the feasibility of using LZ1-based activated carbon as a phase-change material carrier. This strategy achieved synergistic value-addition of biomass resources and industrial by-products, providing insights for developing novel energy-efficient building materials.