Effect of activated carbon microstructure and adsorption mechanism on the efficient removal of chlorophyll a and chlorophyll b from Andrographis paniculata extract
Di Liang, Baoyu Ji, Yun Wang, Xia Li, Wenyuan Gao
Abstract
Abstract In order to reveal the effect of activated carbon (AC) properties on the adsorption of chlorophyll a (Chl a) and chlorophyll b (Chl b) in Andrographis paniculata extract, four commercial activated carbons were first tested and characterized. The results showed that activated carbon 1 (AC1) had the best surface area, pore structure and adsorption capacity. Therefore, adsorption isotherms, adsorption kinetics and adsorption mechanism were further carried out on AC1. The application of Langmuir model ( R 2 > 0.978) and Freundlich model ( R 2 > 0.977) indicated that the adsorption process of Chl a and Chl b on AC1 may be a complex adsorption process of single-layer and multilayer adsorption. The adsorption kinetics indicated that the pseudo-second-order kinetic model ( R 2 > 0.999) was dominant and was mainly chemisorption. The intra-particle diffusion model ( R 2 > 0.937) shows that the intra-particle diffusion is the rate-limiting step. The decrease of adsorption of AC1 to Chl a and Chl b due to the oxidation of acrylic acid proves the importance of π–π interaction.