Mineralogical,surface Chemical And Arsenic Removing Characterization Of Typical Ferrous Manganese Ores

The materials for the removal of heavy metals are current focus of environmental science,and the iron oxides and manganese oxides are the typical adsorption materials which are always as the research objects.Natural Ferrous Manganese ores(FMOs),characterized by iron oxides and manganese oxides,have a good effect on heavy metals removal.FMOs have a very good application prospect in remediation of polluted environment due to their vast resources.However,there are few studies on the mechanisms for heavy metals removal by natural FMOs.In this paper,typical natural FMOs and artificial Fe/Mn oxides and Fe-Mn binary oxide(FMBO)were used as the objects to understand the element content,fractionation,mineralogical and chemical characterizaton as well as the heavy metals(Lead,zinc,cadmium,chromium and arsenic)removal from water and the machanisms by using the techniques of XRD,FTIR,TG,XPS,SEM and the lab batching experiments.The main results were summarized as follows:1.Analysis of XRD and FTIR showed that the main minerals in natural FMOs were pyrolusite,magnetite,hematite and limonite,and in addition the siderite and rhodochrosite in natural manganese carbonate ores.The morphological characterizations of the FMOs by scanning electron microscopy(SEM)indicated that the natural FMOs were in the form of blocks,and the surface were smooth.Small particles were formed on the massive surface after arsenic adsorption.However the artificial ores had small particles,and the surface areas were much larger than the natural FMOs.2.Test of TG found that the mass weight of FMOs,were largely reduced at 47?,260? and 590?,in which resulted in the loss of hygroscopic moisture,the crystal water and the structural water respectively,and the material structure might be damaged at the same time.For the artificial FMBO,the mass weight was largely reduced before 300?.3.Fractionation Fe/Mn in the ores was carried out by a sequential extraction procedure.The results showed that Mn mainly existed as oxidable form(18%~20%),reducible form(11%~21%),and residure form(59%~68%).The Fe mainly existed as the residure form,which was about 95%,indicating that the Fe element in the ores played the role in adsorption and Mn element played the role in oxidation in the process of As adsorption by FMOs.4.Lab batch experiments on heavy metals removal from water found that natural FMOs had a strong adsorption capacity for heavy metals.The adsorption capacity for Pb was the greatest,with the average removal rate of 92.17%;Followed by As,with the average removal rate of 61.60%.Although manganese carbonate ore had the weakest adsorption capacity for As,with the average removal rate of 15.54%,it had a good adsorption capacity for Zn and Cd,with the average removal rates of 66.93% and 42.62% respectively.For artificial FMBO,the adsorption capacity for Pb,Cr and As were very strong,and the average removal rates were 97.25%,99.34% and 99.98% repectively,but the adsorption capacity for Zn and Cd were weak,and the average removal rates were 67.61% and 53.85% respectively.For Fe oxides and Mn oxides,the adsorption capacity for Pb and As were also very strong,and had the selective adsorption capacity for Zn,Cr and Cd.In addition,the Cr removal rate by FMOs had the positive correlation with the surface area and Fe content,and had the negative correlation with the oxidation degree of manganese.The As removal rate by FMOs had the positive correlation with the surface area and Fe content.5.Arsenic isothermal adsorption by FMOs could be well fitted with Freundlich isothermal adsorption equation.Through the adsorption kinetics results,the FMOs reacted quickly with the arsenic solution in the first 4 hours,and then the reactions were stable after 12 hours.6.Analysis of XRD,FTIR and XPS for the FMOs before and after arsenic adsorption indicated that the manganese element as the oxidant oxidized the As(?)to As(?),and at the same time,Mn(?)was reduced to Mn(?).The state of iron element did not change during the reaction,suggesting that Mn was redoxed during the arsenic adsorption,and Fe just involved in the adsorption reaction,and promoted the arsenic removal by FMOs.