Abstract:

Sodium lignin sulfonate(Lgs) was introduced into the solution based on sodium alginate(SA) and acrylamide(AAm) as the matrix, and the porous three-dimensional composite hydrogels(SA/AAm-Lgs) were successfully prepared by free radical polymerization method. The structure and properties of SA/AAm-Lgs were analyzed by scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FT-IR) and mechanical property tester and it was also applied to remove Fe³⁺ from wastewater. The results showed that SA/AAm-Lgs with porous three-dimensional network structure were successfully prepared. When the amount of Lgs increased, the elongation at break and the tensile strength of hydrogel increased correspondingly, and the swelling property also increased to a certain extent. The best static adsorption process of SA/AAm-Lgs for Fe³⁺ was as follows: the amount of Lgs was 7 mg, the temperature was 25 ℃, and the initial mass concentration of Fe³⁺ was 2 g/L. Under these conditions, the adsorption capacity of SA/AAm-Lgs on Fe³⁺ could reach 143 mg/g, showing good adsorption and recycling performance. The adsorption kinetics and adsorption isotherm simulation results showed that the adsorption process of Fe³⁺ by SA/AAm-Lgs conformed to the quasi-second-order kinetics and Langmuir model. In addition, the dynamic adsorption experiments on Fe³⁺ by fixed bed technology proved that the SA/AAm-Lgs had good industrial value. The effects of fixed bed height, initial mass concentration of Fe³⁺ and flow rate on the breakthrough curve were discussed. The results showed that with the increase of fixed bed height, the breakthrough time was extended. When the initial mass concentration and flow rate of Fe³⁺ increased, the breakthrough time was shortened sharply. The BDST model could accurately predict the breakthrough time at different flow rates or concentrations, and the average deviation of theoretical breakthrough time and actual breakthrough time was less than 15%.

Key words: sodium alginate, sodium lignosulfonate, ferric ion, static adsorption, dynamic adsorption