Preparation of CaC₂O₄-direct claret B/chitosan composite materials and adsorption properties for ethyl violet

A composite adsorbent of CaC₂O₄-DB/CTS was prepared using chitosan (CTS) and the hybrid materials of CaC₂O₄ and direct claret B (CaC₂O₄-DB/CTS) by the method of blending in-situ immobilization. CTS and CaC₂O₄-DB/CTS were characterized by SEM, BET and FTIR. The immobilization of CaC₂O₄-DB only increases the specific surface area and binding sites without changing the morphology and structure of CTS. The effects of adsorption time, the initial concentration of ethyl violet (EV), pH and temperature of the solution on the adsorption properties of CaC₂O₄-DB/CTS composite material were investigated in detail, and the adsorption kinetics and thermodynamic behavior of EV on CaC₂O₄-DB/CTS were preliminarily discussed. The results show that the removal rate of dye and chemical oxygen demand (COD) reach 95% and 90% for 100 mg/L EV solution (COD is 187 mg/L), respectively, under conditions of room temperature, CaC₂O₄-DB/CTS dosage of 6 g/L, adsorption time of 3 h and pH=8. The adsorption behavior of EV by the adsorbent is spontaneous and in accordance with Langmuir model and the quasi-second-order kinetic model. The adsorption process is controlled by intra-particle diffusion and the chemical adsorption.