Adsorption Characteristics Of Arsenic And Fluoride From Water By Bio-based And Mg-based Adsorbents

Arsenic and fluoride are considered to be the most serious inorganic pollutants,and World Health Organization(WHO)had set limit at 10 ?g/L and 1.5 mg/L for arsenic and fluorine respectively in drinking Water.At present,the arsenic removal methods included flocculation,adsorption,ion exchange,biological,and membrane treatment.The methods of fluoride removal included precipitation,adsorption,membrane technology,and electro-coagulation.Among them,adsorption had become a hot research field.It has been shown that the adsorption of arsenic and fluorine in the single adsorbent system is significant but,the removal effect is not good under the coexistence system.However,very few studies had been carried to synthesize novel sorbents for simultaneous removing of arsenic and fluoride.Bio-based and Mg-based were used as sorbents for arsenic and fluoride during batch experiments,and discussed the adsorption mechanism.The results showed that:1)Fe/Al modified biochar sorbents suggested the presence of crystalline and forming closed BET curve.The adsorption experimental results showed that removal rates were greatly influenced by pH,ionic strength(IS),and initial concentration(C0).The removal capacity of arsenic and fluorine in single system was stronger than that under coexistence conditions.There was competitive adsorption between arsenic and fluorine.The maximum removal of arsenic and fluorine followed the relationship of BC<mBC<FeAl/mBC.The maximum removal of As(V)and F as 16.38 mg/g and 10.32 mg/g of FeAl/mBC.The adsorption data were described well by the Freundlich isotherm model.Sorbents and sorbates were combined by inter-sphere complex and outer-sphere complex.2)The specific surface area of Mg/Al modified magnetic biochar decreased and the structure of carbon skeleton was destroyed.The removal rate decreased with increasing pH,ionic strength(IS),and initial concentration(C0).The maximum removal of arsenic and fluorine follows the relationship of mBC<Mg/mBC<Al/mBC<MgAl/mBC.The maximum removal of As(V)and F was 34.45 mg/g and 22.11 mg/g of MgAl/mBC respectively.The adsorption isotherm was more suitable for the Langmuir equation.The FTIR spectra showed that the sorbents and the sorbates were combined by inter-sphere complex and outer-sphere complex.3)Mg-based sorbents modified load Si,Zr formed amorphous diffuse reflection peak,the specific surface area were obviously increasedand appearedthe hollow microsphere structure with smooth surface.The pH change has no effect,which was due to the higher pHpzc,The removal rate decreased with the increase of ionic strength(IS)and the initial concentration(C0).The competitive adsorption was obtained in simultaneously removal of As(V)and F.The maximum removal of arsenic by the MgO,Mg-Si,and Mg-Si-Zr was 73.89 mg/g,52.87 mg/g,and 81.68 mg/g;the maximum removal of fluorine was 89.31 mg/g,57.38 mg/g,and 69.31 mg/g,respectively.