Research On Adsorption And Desorption Properties Of Congo Red On Lignocellulose-based Nanocomposites

The lignocellulose and the Ca-montmorillonite were used as raw materials to prepare lignocellulose(carboxymethylcellulose)/montmorillonite nanocomposites through a solution intercalation technique in this paper. The optimum preparation conditions of the nanocomposites were determined by changing the mass ratio of lignocellulose(carboxymethylcellulose) and montmorillonite, the concentration of NaOH, the contact temperature and the contact time. The microstructure of the nanocomposites were characterized by X-ray diffraction (XRD), transimission electron microscope (TEM), scanning electron microscope (SEM) and infrared spectroscope (FT-IR) and the effect of the BET specific surface area and average pore of the nanocomposite on adsorption properties were researched. On this basis, the adsorption characteristics of the nanocomposites were investigated by changing adsorption temperature, the pH values of dye solution, adsorption time and the initial concentrations of dye solution. In order to explore the adsorption mechanism of the nanocomposites, the adsorption kinetics and adsorption isotherm models of the nanocomposites were determined further and the adsorption thermodynamics were investigated. Subsequently, the desorption properties of the nanocomposites were studied by shaker method and ultrasonic wave method. The best desorption conditions of the nanocomposites were determined by changing the concentration of NaOH, desorption time, desorption temperature and ultrasonic wave desorption time. As a result, the regeneration properties were preliminary explored.The research results of this paper were summarized as follows:1. Preparation results showed that the optimal preparation conditions of the lignocellulose/montmorillonite nanocomposite was the mass ratio of1:1at the NaOH concentration of20%after being treated at60℃for6hours; The optimal preparation conditions of the carboxymethylcellulose/montmorillonite nanocomposite was the mass ratio of1:1after being treated at60℃for6hours.2. The characterization results showed that lignocellulose(carboxymethylcellulose) intercalated into montmorillonite interlayer via destroying the crystalline structure of montmorillonite, and the intercalated-exfoliated structure was formed in lignocellulose(carboxymethylcellulose)/montmorillonite nanocomposite, and the adsorption characteristics of the nanocomposite would be effected by the formed intercalated-exfoliated structure.3. The adsorption results indicated that the adsorption properties were effected by adsorption temperature, the pH values of dye solution, adsorption time and the initial concentrations of dye solution. The adsorption capacity of congo red on the carboxymethylcellulose/montmorillonite nanocomposite(161.08mg/g) was much higher than the adsorption capacity on the lignocellulose/montmorillonite nanocomposite(84.17mg/g) and the carboxymethylcellulose(62.42mg/g) at the pH value of4. The sorption processes of the two nanocomposites were better fitted by pseudo-second-order equation and the Langmuir equation. From thermodynamic studies, it was seen that the adsorption was spontaneous, endothermic and increased randomness at the solid/solution interface.4. Desorption results showed that the desorption efficiency of the lignocellulose/montmorillonite nanocomposite and the carboxymethylcellulose/montmorillonite nanocomposite was74.1%and80.17%after using desorption agent of0.01mol/L NaOH at30℃and being treated by the ultrasonic wave for30minutes and50minutes. As a result, the two nanocomposites possessed of the potential of certain regeneration and reuse.