A long-acting hygroscopic and antibacterial composite filler: A new approach to phytoextraction solid residues from Citrus aurantium L.

A promising new composite filler with hygroscopic and antibacterial properties was developed based on the Fructus Aurantii Immaturus solid residues (FAIR) from Citrus aurantium L. , a typical bulk forest industrial crops. FAIR@AM-APTAC composite filler was established using FAIR as substrate, allyl glycidyl ether (AGE) as the cross-linker, while functional monomers of acrylamide (AM) and (3-acrylamidopropyl) trimethyl ammonium chloride (APTAC) were introduced. The structure of FAIR@AM-APTAC was characterized by FTIR, SEM, BET and TG–DSC analysis. The results confirmed that the FAIR@AM-APTAC composite filler was successfully prepared, which exhibited a three-dimensional(3D) network structure with a specific surface area of 0.1758 m²/g and exhibited excellent thermal stability. The equilibrium percent moisture absorption of FAIR@AM-APTAC (63.0%) was higher than that of FAIR (15.7%) under RH= 80% at 25 ℃ for 48 h, and much better moisture adsorption was achieved. The moisture adsorption process of FAIR@AM-APTAC followed a type III moisture adsorption isotherm and conformed to GAB, Peleg and pseudo-second order kinetics model. The moisture adsorption process of FAIR@AM-APTAC was a multi-layer adsorption process with enthalpy driven non-spontaneous and endothermic, which was dominated by chemical adsorption simultaneous existing physical adsorption, and the adsorption force was the synergy of both hydrogen bond and van der Waals force. The inhibition ratio of FAIR@AM-APTAC was 97.1% for E. coli and 95.4% for S. aureus . The antimicrobial efficacy of FAIR@AM-APTAC was enormously improved compared with that of FAIR due to the introduction of quaternary ammonium groups. The antibacterial mechanism of FAIR@AM-APTAC may be that the surface contact between bacterial and FAIR@AM-APTAC leads to inactivation. Significantly, FAIR@AM-APTAC showed long-acting hygroscopic and antibacterial properties, with little weakness even after 120 times cycle of wetting-drying. It is expected to be applied to an indoor air purifier or filter.