Study On Preparation And Arsenic Removal Performance Of Magnesium Oxide Composite Adsorbent

Arsenic is a ubiquitous and widely used metal-like element,which is enriched and polluted in the environment through specific natural processes or human activities,and is harmful to the human body through direct inhalation or biogeochemical circulation.In recent years,arsenic pollution has become a serious threat to human health and social stability.Therefore,how to effectively prevent and control arsenic pollution has become a hot spot and difficult point in the world.Among the methods of arsenic removal,the adsorption method has become one of the hot spots of arsenic wastewater treatment technology research because of its advantages such as simple operation,good removal effect,no or little secondary pollution to the environment,wide source of adsorption materials and reusable use.In recent years,metal oxides have been widely used in arsenic pollution adsorption treatment due to their rich surface functional groups,diverse chemical components,and varied structure and morphology.Magnesium oxide materials are widely used for their high specific surface area,rich hydroxyl groups on the surface,large number of active sites,high adsorption performance,low cost,green and pollution-free properties.However,it is difficult for a single magnesium oxide material to achieve a good arsenic removal effect.Previous studies have found that polyhydroxyl polysaccharides can effectively improve the arsenic removal performance of magnesium oxide adsorption,and also has the advantages of non-toxic,easy biodegradation,and no secondary pollution.However,the actual adsorption effect still needs to be improved,and the mechanism has not been explored and clarified.Therefore,this paper modified magnesium oxide by adding pullulan,soluble starch and pectin,which are three natural non-toxic and polyhydroxyl polysaccharides,to prepare safe and efficient magnesium oxide composite adsorbent,and explore its performance and mechanism of arsenic adsorption and removal.The specific contents and conclusions are as follows:(1)by adding the three polysaccharides of the starch,the soluble starch and pectin,the modified sol gel method was modified by the MgO-P,MgO-D MgO-G compound adsorbent.The adsorption effect of As(V)by using the preparation condition of the good condition can significantly improve the adsorption effect of As(V),and it has the advantages of simple,safe and efficient and no secondary pollution,and provides a new idea for the treatment of arsenic waste water.(2)The use of a wide range of soluble starch to replace the soluble starch in the solution to magnesium oxide is modified by the sol gel,and the magnesium oxide-soluble starch composite adsorbent(MgO-D),which is used to effectively adsorption and remove the As(V).The experiment showed that the adsorption capacity of the concentration of the solution in the 50mg/L concentration was 97.38mg/g,compared with 83.68mg/g of MgO-P,which was able to improve the 16.4%,and also available in the pH of 3～11,which is a more obvious advantage in industrial application.(3)Magnesium oxide was modified by the use of magnesium oxide in the field of magnesium oxide,and the combined adsorbing agent(MgO-G)has a better adsorption effect on As(V),which can reach 111.7mg/g,and have a better removal effect in the wider pH range(3.0～11.0),which provides a lot of potential for the application of MgOG industrial applications.(4)The removal mechanism of As(V)by magnesium oxide-polysaccharide composite adsorbent was further studied by SEM,XRD,XPS,FT-IR and other characterization techniques.SEM-EDS showed that magnesium oxide was modified by adding different polyhydroxyl sugars(such as pullulan,soluble starch,pectin).The adsorbents prepared showed different morphologies and structures.XRD analysis showed that the crystal shape of Mg(OH)2 formed by MgO-G was the best.After adsorbing As(V),Mg(OH)2 and As(V)formed complex precipitation on the surface of the adsorbent.Combined with XRD,XPS and FT-IR analysis,the magnesium oxidepolysaccharide composite adsorbent mainly removed As(V)in the form of surface adsorption and complexation precipitation.