Effects Of Small Molecule Organic Acids/salts On The Ferrous Particles For Stabilization Of Arsenic In Gold Mine Tailings Of Dandong

Arsenic is widely present in natural environment.Arsenic-bearing tailings are piled up on the earth's surface in the process of mining.Due to weathering,natural rainfall leaching,and so on,arsenic of tailings is released into the surrounding environment.So the surrounding soil and water will be polluted.Nanoscale zero-valent iron?NZVI?or granular iron and other ferrous particles can effectively stabilize arsenic in gold mine tailings.However,in the reclamation process of gold tailings,small molecule organic acids released from the surface plants,may lead to the release of arsenic which has been stabilized by the NZVI.In this paper,we chose two different types of gold mine tailings as the research objects to analyze the pentavalent arsenic[As???]in samples which were collected in Dandong,Liaoning Province,China.Acetic acid and malic acid were selected as the representative small molecule acids,on a basis of ferrous particles removing As???,the effects of small molecule acids on the stabilization of As???were researched through batch experiments.SEM-EDS,FTIR,IR and RS were combined to explore the stabilization mechanisms and provide the theoretical and data support for As???stabilization in the process of mine reclamation.The main research findings are as follows:1.The release amounts of arsenic,other heavy metals and common ions in the tailings were obtained.Tailings leaching liquids are both CaSO₄ type.Ion species and contents were different,and the ion content of bio-oxidation tailings was higher than that of flotation tailings.2.Removal rates of arsenic in different substrates were different,mainly related to the mineral phase characteristics in tailings.Within a certain range of pH,the influence of pH on NZVI removing As???was very small.When pH was less than 4,it would inhibit NZVI removing As???.This was due to the effect of the acid on dissolving iron oxides.3.NZVI could remove As???rapidly via complexation occuring on the iron oxide of NZVI's surface.The removal rate of As???under the aerobic condition is bigger than that under the anaerobic condition.Removal rates of arsenic by NZVI aerobic corrosion in the flotation and bio-oxidation tailings increased by 18.03%and15.21%respectively than those by NZVI without corrosion.4.A certain concentration of acetate or malic acid could cause As???stabilized by NZVI or granular iron to release,as ligand exchange and complexing dissolution affected the stability of As???.Secondary release rate of As???in the bio-oxidation tailings was larger than that in the flotation tailings,mainly related to the mineral characteristics of tailings.5.The influence of different concentrations of acetate on the reaction systems was different.The highest concentration of acetate,which widely distributes in nature,would not cause the secondary release of As???stabilized by NZVI.Desorption rates of arsenic in the flotation and bio-oxidation tailings stablized by NZVI aerobic corrosion decreased by 7.56%and 20.01%respectively,compared to those tailings stablized by NZVI without corrosion.Increasing the amount or the aerobic corrosion degree of NZVI did not result in the secondary release of As???in a large concentration range of acetate.