Magnetic chitosan-hydroxyapatite composite microspheres: Preparation, characterization, and application for the adsorption of phenolic substances

The phenolic substances in sugarcane juice seriously affect the color value of sugar products, and gallic acid is one of the main phenolic substances. To develop a new adsorbent able to effectively adsorb phenolic substances from sugarcane juice, magnetic chitosan (CS) hydroxyapatite (HA) microspheres (MCHAM) were prepared by growing HA on magnetic CS microspheres (MCM) in-situ. MCHAM could effectively adsorb gallic acid from sucrose solution, and the highest adsorption capacity was 40.77 mg g(-1). The adsorption kinetics indicated that the adsorption process fit the pseudo-second-order mode, the dominant mechanism was chemisorption, and the Langmuir isotherm mode (q(m) = 48.12 mg g(-1)) described the adsorption behavior of MCHAM best. Recycling experiments indicated that the MCHAM adsorbent presented considerable repeatability. Compared to treating phenolic substances in sugarcane juice using traditional clarifying agents, treatment methods employing MCHAM can efficiently and simply remove phenolic substances without leaving residual sulfur in sugarcane juice.