Synthesis and preservation performance of lanthanum-tannin complex from Cercis glabra Pampan

This article explores the feasibility of rare earth element-tannin complexes as a wood preservative. The tannins (T) from Cercis glabra Pampan. are extracted, sulfonated (ST), and coordinated with lanthanum (La) elements to fabricate the complexes (La-T, and La-ST). Results show that two stable complexes, La-T and La-ST, are successfully formed by coordinating the La-ions with the phenolic hydroxyl groups in T and ST. Sulfonated tannins have a better adsorption capacity for lanthanum ions. The mass percentage of La in La-ST (36.50%) is higher than that in La-T (24.85%). The results of the white-rot decay test reveal that wood treated with La-T (1.98%) and La-ST (2.58%) preservatives has significantly lower weight loss rates compared to the untreated (28.94%). However, the brown rot decay test demonstrates that wood treated with La-T (62.68%) and La-ST (50.81%) only has slightly lower weight loss rates compared to the untreated (71.84%). Finally, the leaching of La-T and La-ST treated poplar wood was significantly lower than La self-treated ones. This novel approach can produce stable rare earth-wood preservatives and improve the wood's bio-durability and anti-leaching properties, thus remarkably enhancing the outdoor performance of modified wood products.