Studies On Preparation And Application Of Alginate Coated NZVI Core Shell Beads

With the development of industrial technology,environmental pollution is becoming more and more serious.Heavy metals are one of the most harmful pollutants in environmental pollution.Heavy metals in the waste water can be enriched in the human body through the food chain,causing great harm to the environmentandhumanbeings.Hence,theremovalmethodand material research of heavy metals are of great importance.For many years,many experts and scholars are committed to the removal of heavy metal.The main research methods include ion exchange,chemical precipitation and solvent extraction,but they also have some shortcomings,such as high cost,and easy to create second pollution.Adsorption is widely used because of its advantages of low cost.Two kinds of adsorbents were prepared in this study,one is core–shell nanoscale zero-valent iron@alginate sodium composite loaded with calcium?n ZVI@SA-Ca?beads,theotheriscore–shellnanoscalezero-valent iron@alginate/carboxymethyl cellulose sodium composite loaded with calcium?n ZVI@SA/CMC-Ca?beads.To study the removal mechanism of U?VI?and Cu?II?,the main contents include the following aspects::1.Alginate,nanoscale zero valent iron as the raw materials,calcium chloride as cross-linking agents were used to prepare core-shell n ZVI@Alg-Ca beads by coaxial electric spray method,and were applied to remove uranium.The results showed that the maximum adsorption capacity of core-shell n ZVI@Alg-Ca beads for uranium was 204.12 mg/g when the p H was 3,the initial concentration was 280 mg/L,the reaction time was 10 h and the temperature was 318.15 K.The adsorption process is in accordance with the pseudo-second-order kinetics model and the Langmuir isothermal model,and the adsorption process is endothermic and spontaneous.The coexisting ions had little effect on the adsorption of uranium.After four cycles of core-shell n ZVI@Alg-Ca beads,the removal rate of the besds is 62.671%,indicating that the core-shell n ZVI@Alg-Ca beads can be recycled many times.2.Sodium alginate,sodium carboxymethyl cellulose and nanoscale zero-valent iron as raw materials,core-shell n ZVI@SA/CMC-Ca beads were synthesized in this study using coaxial electronic injection method.Effect of mass ratio of alginate/carboxymethyl cellulose,mass concentration of Ca²⁺on gel strength was studied.Results showed that the optimum gel strength condition were alginate/carboxymethyl cellulose mass ratio of 3:1 and the concentration of alginate/carboxymethyl cellulose solution was 2 wt%,mass concentration of Ca²⁺was 2 wt%.The adsorption studies for copper onto core-shell n ZVI@SA/CMC-Ca beads in copper aqueous solution system were investigated.The results showed that when the p H value of the solution was 4,the reaction temperature was 298.15 K,and the reaction time was 6 h,the core-shell n ZVI@SA/CMC-Ca beads has the maximum adsorption amount for copper.The adsorption process is in accordance with the pseudo-second-order kinetics model and the Langmuir isothermal model.The process of the adsorption process was spontaneous and endothermic.The coexisting ions had little effect on the adsorption of copper.After 5 times of regeneration,the adsorption capacity of adsorbents for copper was almost unchanged.3.Sodium alginate,sodium carboxymethyl cellulose and nanoscale zero-valent iron as raw materials,core-shell n ZVI@SA/CMC-Ca beads were synthesized in this study using coaxial electronic injection method.The adsorption studies for uranium and copper onto core-shell n ZVI@SA/CMC-Ca beads in copper-uranium mixed aqueous solution system showed that the maximum adsorption amount for uranium and copper were 138.92 mg/g and52.51 mg/g at p H 4.0,298.15 K,concentration 340 mg/L for 10 h.The adsorption process accords with the pseudo-second-order kinetics model and the Langmuir and Freundlich isothermal models.The removal process of core-shell n ZVI@SA/CMC-Ca beads for uranium and copper mainly includes adsorption and reduction.4.The dynamic adsorption properties of the adsorbent for uranium was measured under variable operating conditions,such as initial influent ions concentration,bed depths and flow rates.The results showed that the breakthrough time and depletion time were increased with an increase in bed heights but obviously shortened with an increase in influent concentration and flow rates,respectively.