Investigation Of The Preparation,Forming And Sulfate Adsorption Performance Of Zr（OH）₄/Zeolite Adsorbents

Sulfate exists ubiquitously in industrial production and daily life and sulfate contamination has negative effect on humans as well as environment.As a result,how to avoid or diminish such contamination has attracted increased attention world widely.The State Council and the World Health Organization（WHO）have strengthened the standard against sulfate by new and strict treatment.The traditional methods of removing sulfate have their own drawbacks.Therefore,much effort has been dedicated in recent years to propose and implement green,high-efficient and economical approaches to deal with desulfurization.Among these technologies,using Zr（OH）₄ as active species to adsorb sulfate has drawn much attention in this area.However,such method always suffers from easily-lost Zr（OH）₄ powder,high operation cost and unrecycled issue.In this paper,modified green and economical Zr（OH）₄/Y-type zeolite material has been synthesized and investigated for desulfurization process in water.Two methods are applied to modify Y-type zeolite,which are direct replacement of the hetero atom Zr and the Zr⁴⁺ion exchange.A stepwise impregnation method is employed to ensure that the molecular sieve pores are not blocked and more uniform distribution of active species.In order to explore the optimal production process of the adsorbent and the role of each step,a variety of adsorbents were prepared and their physiochemical,adsorption and regeneration properties were tested.A series of static adsorption experiments were carried out under different conditions using adsorbent to explore the optimal conditions for the adsorption performance and study the mechanism of the adsorbent.Also,the molding effect has been studied under different molding conditions.Furthermore,a series of dynamic adsorption experiments are carried out under different conditions in packed fixed bed,which lay a data foundation for the industrial application of the adsorbent.The dynamic adsorption data was used to map the breakthrough curve,which deepen the understanding of the dynamic adsorption process using fitted model.The results show that the inclusion of the hetero atom Zr in the framework stabilizes the active component.Ion exchange method also plays a role in increasing the loading of the active component.Surface area is slightly reduced in modified zeolite material,however,some mesopores were generated at the same time.By static adsorption and regeneration experiments,Zr（OH）₄/Y-type adsorbent shows high selectivity and strong regeneration capacity.It can hold the initial 90%adsorption capacity after 5 times of regeneration steps.Also,it shows that the adsorption capacity of SO₄^2-decreases with the increasing temperature and p H,and increases with the increase of SO₄^2-concentration.The optimal adsorption conditions in this study were as follows:the concentration of SO₄^2-was 10 g/L,the p H was 1.5,the adsorption temperature was 25°C,and the adsorption time was 60 min.The adsorption capacity can reach up to 284.22 mg/g under this condition,where Al₂O₃ was used as the binder,10 wt%nitric acid was used as the peptizer.The mass ratio of molecular sieve,binder and peptizer was 10:3:4,and the water-powder ratio was 0.85.The dynamic adsorption process of the adsorbent conforms to the Bohart-Adams model,which gives insight to the adsorption capacity in the industrial process.