Copper(II)-silk fibroin complex fibers as air-purifying materials for removing ammonia

To remove ammonia, traditional activated carbon is not as effective as expected. In this paper, a new alternative method of removing ammonia with metal-silk fibroin complex fibers through a coordination displacement reaction is proposed and studied. Electron spin resonance spectra ((ESR)) and atomic absorption spectrometry show that the Cu(O)(4) complex with low copper(II) content is formed when silk fibroin is soaked in cupric aqueous solution under acid condition, while the structure of the Cu(N)(4) complex with high copper(II) content is formed in a cuprammonia solution. Experimental results further show that the Cu(O)(4) Complex is more effective than the Cu(N)4 complex in term of ammonia adsorption. It is highly desirable to prepare a deodorizing material that has both high copper(II) content and a Cu(O), complex structure. Based on our study, a novel deodorizing fiber is prepared as follows: silk fibroin fibers are first treated with tannic acid (TA), then dipped into the cuprammonia solution to obtain the Cu(O)(4) complex containing 8.5% (wt%) copper(II). Such fibers show high deodorizing performance and can be regenerated by heating.