Preparation Of SA/Rare Earth Polymer Gel Spheres And Its Adsorption Properties For Dye

The rapid development of the printing and dyeing industry has led to the production of a large number of high-density printing and dyeing wastewater,and its effective treatment technology has become the focus of water treatment.As a renewable natural marine resource,sodium alginate?SA?has been widely used in the treatment of printing and dyeing wastewater because it contains a large number of reactive groups in its molecular chain and can interact with various dye molecules.In this paper,two kinds of alginate gel ball adsorption materials,namely SA/La?III?and SA/Y?III?,were prepared by the raction between SA and rare earth ions.The materials were analyzed by SEM,XRD,FT-IR,UV-Vis DRS and TGA,and were used for the adsorption Direct Green BE?DG BE?,Weak Acid Dark Blue 5R?WAB5R?Direct Red 4BE?DR 4BE?,and Weak Acid Brilliant Blue RAW?WABB RAW?,respectively.The preparation and adsorption conditions,adsorption kinetics,adsorption thermodynamics,isothermal adsorption and gel ball regeneration performance of the materials were investigated in detail,and the adsorption mechanism was analyzed.The conclusions are as follows:?1?SA/La?III?and SA/Y?III?adsorbent materials were prepared by injection method,and the optimized conditions for the material preparation were as follows:SA solution 2g/100 mL of was stirring at room temperature and resting for a certain time.Then,it was dropped into La?NO₃?₃?3.5 g/100 mL?and Y?NO₃?₃?4.0 g/100 mL?two cross-linking agent solutions,respectively.After 2 hours of cross-linking reaction,the pellet was taken out,rinsed 3 times or more and dried to obtain SA/La?III?and SA/Y?III?gel adsorbents.?2?The optimal conditions for the adsorption of DG BE and WAB 5R dyes by SA/La?III?were that:when the initial concentrations of the two dyes are 3000 mg/L and 2000 mg/L,the pH is 6.0,the dosage is 0.06 g,and the adsorption time was 120min at 25?,capacities and removal rates of adsorption DG BE and WAB 5R were605 mg/g,618 mg/g,97%and 96%,respectively.The optimum conditions for the adsorption of DR 4BE and WABB RAW dyes by SA/Y?III?are as follows:the initial dye concentrations were 3000 mg/L and 2000 mg/L,the natural pH values of the dyes were 9.84 and 7.11,the dosage was 0.05 g,the adsorption reaction time was 120 min at 25?,and the adsorption capacity of DR 4BE and WABB RAW was obtained.They were up to 1411 mg/g and 953 mg/g,respectively,with removal rates of 94%and 95%,respectively.SA/La?III?and SA/Y?III?adsorbents have a wide pH range.?3?The adsoption kinetic studies of DG BE,WAB 5R and DR 4BE and WABB RAW by SA/La?III?and SA/Y?III?respectively show that the adsorption process can be well described by the second-order rate equation?R²>0.9991?at different temperatures?298K,313K and 328K?the adsorption rates is faster and the adsorption equilibrium can be reached within 120 min.Intraparticle diffusion is the main rate-control step.?4?The Langmuir isotherm model can be used to describe the adsorption behavior of DG BE,WAB 5R and DR 4BE and WABB RAW on SA/La?III?and SA/Y?III?,respectively?R²>0.9960?,and the values of Langmuir separation factor R_L are less than 1,indicating that the adsorption rection is easy to carry out.According to the values of apparent activation energy Ea and thermodynamic parameters?H,?G and?S,the adsorption of DG BE and WAB 5R on SA/La?III?are spontaneous endothermic reaction;The adsorption of DR 4BE and WABB RAW on SA/Y?III?are spontaneous exothermic reaction.In addition,adsorption is mainly through electrostatic adsorption and hydrogen bonding,accompanied by chemical adsorption.?5?The regeneration results show that SA/La?III?adsorbent saturated by DG BE and WAB 5R are shaking with distilled water at room temperature for 1 h,the first regeneration rate is 99.3%and 99.7%,respectively.The second regeneration rate dropped to 71%and 74%,respectively.It is indicated that SA/La?III?can be regenerated at least once time.?6?Characterization of SA,SA/La?III?and SA/Y?III?by SEM,EDS,XRD,UV-Vis DRS,FT-IR and TGA revealed that the SA powder consisted of irregular blocks and rod-shaped particle composition.SA/La?III?and SA/Y?III?gel particles are irregularly spherical with rugged surface,rich layered structure and fissured rugae.La?III?and Y?III?successfully exchanged with most of the Na⁺in the SA molecule,and coordinated to form a three-dimensional network of gel spheres.The adsorption of four dyes on SA/La?III?and SA/Y?III?has also chemical effects in addition to important electrostatic adsorption and hydrogen bonding.In addition,the thermal stability of both materials are superior to that of SA,which are very convenient for storage and use at room temperature.The two gel adsorbents SA/La?III?and SA/Y?III?prepared in the study can effectively treat high-concentration dye wastewater.The preparation method of materials are simple and time-consuming,the obtained gel adsorbents has low cost,large adsorption capacity and environmental protection and avoids secondary pollution,and has a wide range of pH application.This provides a way for the future treatment of printing and dyeing wastewater by sodium alginate-based adsorbent materials,and it is expected to have a broad development prospect in the field of wastewater treatment.