Adsorption behavior of tetracycline on carboxymethyl starch grafted magnetic bentonite

Accumulation of tetracycline (TC) in soul and aqueous environments threatens the ecology balance and human health. In this work, Magnetic bentonite (MB) modified with two kinds of starch (corn starch and carboxymethyl starch) were synthesized for removal of TC. The composite materials were characterized by XRD, SEM, VSM and FTIR techniques. The adsorption capacities of TC for raw bentonite (RB), magnetic bentonite (MB), corn starch modified magnetic bentonite (ST-MB) and carboxymethyl starch modified magnetic bentonite (CMS-MB) were evaluated with batch adsorption equilibrium experiments. The modeling of isothermal adsorption and kinetic adsorption for four materials was done. The fitting results shows adsorption of CMS-MB composite follows the Langmuir model and pseudo-second model. The CMS-MB composite showed the best adsorption performance with Langmuir theoretical adsorption maximum of 169.7 mg/g. The adsorbent CMS-MB can be easily separated by magnetic force from solution with extremely low turbidity. The adsorption mechanism was also discussed.