The Effect Of DOM-ferrite Composite Colloid On The Migration Behavior Of Inorganic Arsenic In Porous Media

Arsenic has migratory variability and cumulative variability in both surface water and groundwater environments.The problem of arsenic pollution caused by the change of environmental media has been paid more attention.Therefore,it is of great practical significance to research the migration and transformation process and regulation mechanism of arsenic in soil environment in porous media,which can provide theoretical and practical basis for arsenic pollution control and remediation.In the paper,As(?)contaminated groups and arsenic compound colloids contaminated groups were chosen as two research objects.The effects of dissolved organic matter,pH,ionic strength,iron ions,and iron oxides(a-Fe2O3)on the migration behavior of As(?)in quartz sand column were investigated.The main work was as follows:As(?)pollutant migration behavior in water-saturated quartz sand column;Research on the behavior of ferric humate carrying arsenic in quartz sand column;Research on the behavior of humic acid iron oxide carrying arsenic in quartz sand column.The main results and conclusions were as follows:1.The migration behavior of arsenate entering quartz sand column as pollution mass was greatly affected by humic acid concentration,pH,ionic strength and iron ion concentration.The increase of humic acid concentration and pH had a positive effect on the migration of As(?)in quartz sand column.High ionic strength and iron ion concentration inhibited the migration behavior of As(?)in quartz sand column.The experiment showed obvious tailing phenomenon.The migration mechanism of As(?)was adsorption,including electrostatic adsorption and complexation.2.The migration behavior of ferric humate carrying arsenic in quartz sand column was studied in the paper.There were two reasons why humic acid inhibits As(?)migration.One was humic acid and arsenic acid competing for adsorption sites on quartz sand surface and the other one was humic acid and arsenate reacting to form macromolecular substances.pH influenced the charge on the surface of humic acid and quartz sand by changing the H+ concentration,thus changing the interaction between arsenate and humic acid and quartz sand.The low pH had a promoting effect on As(?)migration behavior but the effect of high pH was opposite.The double electron layer of ferric humate and quartzite colloid changed with the variety of ionic strength.With the increasing of ionic strength,the migration ability of As(?)decreased.Fe(?)reacted with phenolic hydroxyl and carboxyl groups in HA to produce Fe(?)resulting in a decrease of adsorption sites and facilitating migration of As(?).The main migration mechanism of As(?)was adsorption,including electrostatic adsorption,complexation,ion exchange,and chemical reaction.3.The migration behavior of humic acid iron oxide carrying arsenic in quartz sand column was studied in the paper.The interaction between humic acid and nano iron oxide made iron oxide unable to provide more adsorption sites and promoted the migration of As(?).pH changed experiment acid-base conditions.In the H+ rich system,Fe-OH on the surface of iron oxide reacted with H+ to generate FeOH2+ enhanced the adsorption.However,in the OH' rich system,Fe-OH reacted with OH-to form Fe-O',which weakened the adsorption and promoted As(?)migration.The ionic strength influenced As(?)migration by changing the double layer and surface charge of humic acid nano-iron oxide colloids.Low ionic strength promoted As(?)migration and high ionic had the opposite effect.The reason that the increase of iron oxide content promoted the migration of As(?)was that the redox of iron oxide and humic acid produced Fe(?),and the available adsorption sites were reduced.The main migration mechanism of As(V)was adsorption,including electrostatic adsorption,complexation and chemical reaction.4.Time fractional convection-diffusion model fited experiment data of As(?)migration in quartz sand column.The solute migration behavior with anomalous diffusion was well described.It showed that time fractional convection-diffusion model was suitable for the migration behavior of pollutants with abnormal diffusion in porous media.