Synthesis of a novel magnetically recyclable starch-based adsorbent for efficient adsorption of crystal violet dye

A novel magnetic starch-based adsorbent (MSBA) was synthesized from the copolymer solution of starch-grafted acrylic acid treated by an alkali homogeneous phase as the precursor and Fe3O4@SiO2 particles as raw materials. The feasibility of dye wastewater treatment was studied using crystal violet (CV) cationic dye as the model dye. The research results have indicated when the optimum condition kept the temperature of 308 K, CV concentration of 10 mg·L-1, pH of 9.0, the adsorbent dosage of 0.10 g, and the adsorption time of 50 min, 90.31% of the CV can be removed by the MSBA. In terms of the Langmuir isotherm model, the maximum adsorption capacity for CV was 49.10 mg·g−1. The magnetic saturation intensities of MSBA were 14.80 emu·g−1. The kinetics results showed that the adsorption process conformed to the first-order model and the rate-controlling step was determined by multiple stages. In addition, the adsorption isotherms displayed that CV adsorption was well fitted to the Langmuir model, and thermodynamic parameters depicted the spontaneous endothermic process. The adsorption mechanism of CV involved electrostatic interaction and hydrogen bonding. The adsorbents can be regenerated in ethanol solution and the removal efficiency remained at 83.04% even after five adsorption-desorption cycles. MSBA can be recovered with a magnet and only experience a 7.6% loss of adsorbent with each reuse cycle. These results suggest MSBA is a promising candidate adsorbent for dye wastewater treatment because of its excellent properties, including high adsorption efficiency, simple magnetic separation and reusability.