Studies On Preparation And Adsorption Performance Of Alginate Gel Microspheres

The discharge of the wastewater from uranium mining, electroplating and battery industrial leads to fluoride pollution. Because of ease cooperation and low cost, adsorption has become a preferred method for removing fluorine-containing wastewater of low concentrations.In this study, the alginate bead adsorbents are prepared with sodium alginate as raw material through sodium alginate modification and high voltage electronic injection method. The adsorption properties of adsorbent for fluoride ion are investigated, which could provide the theoretic and scientific basis for the exploitation of adsorbent and the treatment technology of wastewater containing fluoride. The detail contents are as follows:(1) The influences of the concentration, pH, and metal ions on the rheological properties of sodium alginate solution were studied. The result indicated that storage modulus of sodium alginate solution was higher than loss modulus under strain sweep mode, which suggested that sodium alginate solution was the adhesive dominating fluid.(2) Aluminum alginate particle adsorbent was prepared with sodium alginate as raw materials and aluminum chloride hexahydrate solution as crosslinking agent via high voltage electronic injection method by means of a high voltage electrostatic spinning device. The adsorption characteristics of the adsorbent for fluoride ion were studied. The results indicated that the adsorption of fluoride onto aluminum alginate was well described by the Langmuir model and pseudo-second-order kinetic model. The optimal adsorption conditions were as follows:pH of 1.5, contact time of 21h, fluoride concentration of 150mg/L and the temperature of 298.15K. The uptake capacity of the aluminum alginate was 79.30mg/g at the optimal conditions. The adsorption of fluoride by aluminum alginate was a spontaneous and exothermic process when the temperature was lower than 328.15K. The elution rate of aluminum alginate particles was 54.26% after five cycles, alginate aluminum particles produced carbon dioxide gas and water after incineration, the volume reduction rate was 85.71%.(3) The porous zirconium alginate bead adsorbents were prepared via a high voltage electrostatic spinning technology, with sodium alginate as matrix material, sodium bicarbonate, calcium carbonate and sodium dodecyl benzene sulfonic acid as porogens, zirconium nitrate pentahydrate solution as the crosslinking agent. The adsorption characteristics of the adsorbent for fluoride ion were studied. Results displayed that the adsorption process was followed by the Langmuir adsorption isotherm model and the kinetics process of adsorption was followed by pseudo-second-order kinetic model (R2=0.9953). Adsorption capacity was 32.797mg/g under the optimal adsorption conditions (pH of 2.0, contact time of 20h, initial concentration of 100mg/L). The process of adsorption was exothermic and spontaneous. The adsorption mechanism was mainly the physical adsorption and coordination bond between Zr4+ and F-. The desorption efficiency was about 68.65% after two cycles.(4) The effect of flow rate, bed height and fluoride concentration on dynamic adsorption properties of aluminum alginate for fluoride ion was investigated with the fixed bed adsorption technology. The results suggested the breakthrough time of aluminum alginate column was increased with the decrease of flow rate and fluoride concentration, increase of bed height. The experimental data of dynamic adsorption was well described by the BDST and Thomas model.