Removal Of 17?-estradiol From Water By Multi-walled Carbon Nanotubes Stabilized Fe-mn Binary Oxide Nanomaterials And Its Mechanism

There is growing concern about the possible health threat to animal and human posed by endocrine-disrupting chemicals(EDCs)in the environment.EDCs exist widely in water sources,soil and foods.At present,EDCs have been detected in various water sources around the world,but the corresponding treatment methods are still blank.The persistence of these compounds makes harmless treatment tricky.Estrogens are well-known as EDCs,which include endogenous hormones like 17?-estradiol(E2)and synthetic estrogens like 17?-ethinylestradiol(EE2).E2 is a steroidal hormone and naturally synthesized by wildlife and livestock to promote their growth and reproduction.The main source of estrogen in the environment is the increasing discharge of wastewater from pharmaceutical and intensive farms.All kinds of reproductive diseases,such as testicular cancer,breast cancer and malignant tumors of reproductive system,are directly related to estrogen.Among all kinds of methods for removing refractory organic pollutants,adsorption has been widely used in the water treatment process of detoxification and purification of wastewater because of its availability,simple operation,no harmful by-products and low cost.However,the disadvantages of traditional adsorbents,such as low adsorption capacity and complex preparation,limit their applicability to new pollutants.In order to effectively remedy the estrogen-contaminated water and improve the aquatic environment,it is urgent to develop a new and efficient adsorption material.Ferromanganese oxides widely exist in nature.It was widely used as adsorbents to remove pollutants from water.Manganese oxide is a widely used solid-phase oxidant with high redox potential,which can promote the oxidation of various synthetic and natural organic pollutants,including humus,phenols,endocrine disruptors and chlorinated organic compounds.Ferromanganese oxides stabilized by specific materials have good thermal stability,dispersibility and better adsorption performance in aqueous solution.In this work,the multi-walled carbon nanotubes(MWCNTs stabilized ferromanganese oxide nanocomposites(MWCNTs/FMBO)were prepared by coprecipitation method and applied to in-situ removal of E2 from wastewater.The characterizations of the mesoporous adsorbent were analyzed by using SEM,TEM,VSM,FTIR,XRD and XPS measurements.The maximum monolayer adsorption capacity(qm)of MWCNTs/FMBO for E2 in the experiment was 47.25 mg/g as verified by the Langmuir sorption isotherm study.The adsorption process was pH-sensitive with an optimum pH of 7.0.On the kinetics study,the adsorption data could be satisfactorily fitted by the pseudo-second-order kinetics.The adsorption process was spontaneous and exothermal.The foreign ions did not show any noticeable inhibition for E2 removal from water solution at low concentrations.However,the ionic strength of solution has a significant influence on the adsorption process.The maximum removal of E2 by MWCNTs/FMBO is 37.78 mg/g when NaCl concentration is 0.005 mol/L.Electrostatic attraction,hydrogen bonding and ?-? interaction might be the dominating adsorption mechanisms for E2 adsorption onto MWCNTs/FMBO.In addition,the adsorption capacities of the mesoporous adsorbent remained at 86.16 % even after five adsorptiondesorption cycles without significant loss of capacity,which demonstrated the stability and reusability of materials for further removal of E2 and the reduction of total cost in wastewater treatment.