Competitive Adsorption Of Arsenic And Phosphate Onto Fe/Al-mn Binary Oxide

Arsenic pollution in water has a enormous harm to human health.In recent years,a large number of studies have been carried out on the removal of arsenic from water by adsorption.Inhibition of phosphorus for adsorbing arsenic is a significant and general problem to solve.In order to strengthen the arsenic removal,iron and manganese binary oxide(FMBO)and aluminum and manganese binary oxide(AMBO)were used as adsorbents.The synchronous adsorption characteristics and competition law of arsenic and phosphorus were studied by adsorption kinetics experiment,effect of pH and adsorption sequence influence experiment.By analyzing the surface morphology of the adsorbent before and after the reaction,the competitive mechanism of arsenic and phosphorus on the micro interface of oxidation /adsorption was tentatively revealed.Some conclusions can be drawn as follows:1.The kinetics data of As(III)&P and As(V)&P were well described by the Power model and Elovich model.In the complex pollution conditions,adsorption process included diffusion of solutes at the solution and the interfaces,combination of solute with the active sites which had different adsorbents surface energy on the suface of adsorbent,electron transfer and share et al.In the process,the activation energy of the system changed greatly,and the activation-deactivation occurred.2.The lower ratio of Mn in FMBO was more favorable to the adsorption of As(III)&P and As(V)&P,but the adequate Mn content in AMBO is beneficial to the adsorption of As(III)&P and As(V)&P.The oxidation of MnO2 to As(III)in FMBO is stronger than that in AMBO,which can oxidize As(III)to As(V)more effectively than AMBO.3.The influence of changing pH on adsorbing As(V)on FMBO and AMBO is greater than that on As(III).Adsorption capacity of As(III)and As(V)decreased with the increase of pH.Adsorption capacity of As(III)and phosphorus on FMBO is higher than that on AMBO when adsorbed As(III)&P,and capacity of As(V)is higher but the capacity of phosphorus is lower than that on AMBO.4.A portion of the initially adsorbed ion is replaced by the competing ion under differentpH conditions.Replacement of As(III)/As(V)by P is weaker than P by As(III)/As(V).Due to the simultaneous of oxidation and adsorption for As(III),a large number of pores can be generated on the surface of the material and more active sites are exposed,the adsorption of As(V)is only affected by hydroxyl binding and electrostatic attraction,the loss ratio of As(V)was higher than As(III).When adsorbed As(III)/P by AMBO,the replacement ratio of As(III)and P were higher than that of the same Mn ratio onto FMBO.while As(V)/P was more likely to be replaced onto FMBO than ABMO.5.Scanning electron microscope showed that FMBO and AMBO were aggregated by a lot of small particles,and the surface was rich pore structure is rough.Material surface was distribution of Fe/Al,Mn and O elements.Fourier transform infrared spectroscopy indicated that there also were lots of hydroxyl groups on the surface.The deviation of surface hydroxyl groups and the corresponding spectra of the elements showed that As/P was successfully adsorbed onto the surface of the material.6.When adsorbed As(III)/P by both AMBO and FMBO,the change of the relative contents of As-O and P-O indicated that there were competitive adsorption between As(III)and P.The latter iron can replace a part of former which had adsorbed.Compared with As(III),the weaker exchange of As(V)ratio in the As3 d peak showed that the replacement of P with As was mainly associated with the As(III).When adsorbed As(V)/P,the relative content of As was lower than that of As(III)/P,indicating that the ability of As(III)to compete for adsorption sites with P was stronger than that of As(V).In addition,the relative content of As(V)was more stable onto AMBO than FMBO illustrated As(V)combined more film with AMBO than FMBO,namely the effect of Fe-OH on As(V)is stronger than that of Al-OH.The ratio change of the As(III)/As(V)and Mn(II)/Mn(IV)showed that FMBO adsorbed As(III)more easier than that AMBO,and FMBO adsorbed As(III)directly while AMBO converted As(III)to As(V)then adsorbed it to the surface.