Study On Removal Of Sb(Ⅲ) And Sb(Ⅴ) From Water By 4A Type Molecular Sieveloaded Ce And Magnetic Iron Oxides

Antimony(Sb) mainly exists in the form of Sb(Ⅲ)and Sb(Ⅴ)in aquatic environments,with Sb(Ⅲ)being 10 times more toxic than Sb(V).The antimony concentration in the drainage during the desizing and dyeing stages of the printing and dyeing process can exceed 4.0 mg/L and 7.0 mg/L respectively,far exceeding the requirement of the "Discharge standards of water pollutants for dyeing and finishing of textile industry" that the antimony concentration in the drainage is below 100 μg/L.It is urgent to develop efficient treatment technologies for antimony containing wastewater.This study selected 4A type molecular sieve as the carrier,loaded with rare earth cerium(Ce)and magnetic iron oxide(Fe3O4 or γ-Fe2O3),synthesized two new magnetic antimony removal adsorbents and studied their adsorption behavior and mechanism.There are main conclusions:(1)Ce and Fe3O4 were simultaneously loaded on 4A molecular sieve,and the optimal adsorbent was synthesized by coprecipitation with 1:1 mass ratio of CeCl3 and Fe3O4,named 4A@Ce/Fe3O4.The results of XRD,EDS,FTIR,and XPS confirmed the successful loading of Ce and Fe3O4,as well as the adsorption of antimony and the oxidation of the loaded Fe3O4.At pH=7.0,The maximum adsorption capacities of.4A@Ce/Fe3O4 for Sb(Ⅲ)and Sb(Ⅴ)are 22.29 mg/g and 13.02 mg/g,respectively.The saturation magnetization of 4A@Ce/Fe3O4 adsorbent is 13.21 emu/g,which can be separated from solid and liquid by an external magnetic field.The coexisting anion experiment showed that Cl-promoted the adsorption of Sb(Ⅲ),while H2PO4inhibited the adsorption of Sb(Ⅲ)and Sb(Ⅴ).The adsorbent was desorbed by 1.0 mol/L NaOH,and after 4 cycles of reuse,it still had 54.02%of the original adsorption capacity for Sb(Ⅲ).Mechanism exploration has found that adsorption involves both physical and chemical interactions,and possible adsorption mechanisms include surface complexation,redox reactions,electrostatic interactions,and internal diffusion.(2)Ce and γ-Fe2O3 were simultaneously loaded on 4A molecular sieve,and the optimal adsorbent was synthesized by coprecipitation with 1:3 mass ratio of CeCl3 and γ-Fe2O3,named 4A@Ce/γ-Fe2O3.The successful loading of cerium iron and the adsorption of antimony were also confirmed through characterization methods.At pH=7.0,The maximum adsorption capacities of 4A@Ce/γ-Fe2O3 for Sb(Ⅲ)and Sb(Ⅴ)are 50.50 mg/g and 10.03 mg/g,respectively.The saturation magnetization of 4A@Ce/γ-Fe2O3 adsorbent is 23.70 emu/g,the magnetic separation performance is good,and there is no obvious dissolution of cerium and iron when the initial pH is 4.0～9.0.The experiment of coexisting anions shows that HCO3-will inhibit the adsorption of Sb(Ⅴ),while H2PO4-will compete with Sb(Ⅲ)and Sb(Ⅴ)for active site,inhibiting the adsorption of Sb(Ⅲ)and Sb(Ⅴ).After 4 cycles of reuse,the adsorption capacity of Sb(Ⅲ)remained around 70.88%of its original value,indicating a good reuse effect.Mechanism exploration revealed that adsorption is mainly a chemical process,and possible adsorption mechanisms include ion exchange,surface complexation,redox reactions.Among them,the formation of M-O-Sb complexes plays a major role in the adsorption of antimony.(3)The adsorption test results of simulated printing and dyeing wastewater indicate that,4A@Ce/Fe3O4 has a better adsorption effect on antimony in low concentration simulated printing and dyeing wastewater.When the dosage is 2.0 g/L,the remaining antimony concentration in the wastewater after adsorption by both composite magnetic adsorbents is less than 100 μg/L,in accordance with the requirements of the "Discharge standards of water pollutants for dyeing and finishing of textile industry"(GB 4287-2012).pH and temperature have a significant impact on the adsorption of antimony,while lower temperatures are not conducive to antimony adsorption.