Study on the adsorption properties of multiple-generation hyperbranched collagen fibers towards isolan-series acid dyes.

In the present study, collagen fibers derived from leather solid wastes were used and modified as insoluble vectors and successfully employed as adsorbents for the removal of acid dyes. A "one-step" method was applied to synthesis effective adsorbents, which provided a sustainable way to reuse leather solid wastes via multifunctional modification. The adsorption properties of amino-terminated hyperbranched polymer (HBPN)-modified collagen fibers for the removal of different kinds of acid dyestuff from aqueous solutions were studied. The adsorption capacities of the second generation of modified collagen fibers (CF-HBPN-II) toward Isolan Black 2S-LD, Supralan Yellow, Isolan Grey K-PBL 02, Isolan Dark Blue 2S-GL 03, and Isolan Brown NHF-S were determined to be 224.87, 340.14, 287.36, 317.80, and 251.25 mg g-1, respectively. Three kinetic models, namely, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were used to analyze the kinetic data. The fitting result indicated that the adsorption process of Isolan Black 2S-LD on CF-HBPN-II followed a pseudo-second-order rate model. The adsorption equilibrium of amino-terminated hyperbranched polymer-modified collagen fibers (CF-HBPN) was analyzed using the Langmuir, Freundlich and Temkin isotherm models. The Langmuir isotherm was suitable to describe the adsorption process of Isolan Black 2S-LD. R L was observed to be in the range of 0-1. The values of ΔH, ΔS and ΔG suggest that adsorption is an endothermic and spontaneous process. The adsorbed dye from the modified collagen fiber was successfully desorbed by 0.1 M NaOH. This research provides theoretical guidance for the engineering and recycling application of bio-based adsorbents.