| Arsenic is a highly toxic substance in nature because of the development of modern industry,arsenic and arsenic metal mining and smelting,the arsenic compounds are used as pigments,glass,paper and other raw materials.in addition,due to the use of arsenical pesticide,the coal combustion process can produce waste gas,waste water and waste residue arsenic,not only pollute the environment,but also threatening the human health and safety.Therefore,efficient and environmentally friendly treatment of arsenic pollution is very important.Nowadays,there are many ways to remove arsenic,which can be roughly divided into coagulation,membrane filtration,ion exchange,biological,adsorption method and so on.The advantages and disadvantages of all kinds of methods coexist,but more and more attention has been paid to the adsorption in many kinds of arsenic removal methods.It is mainly because of its simple operation,obvious effect of arsenic removal and does not produce secondary pollution.Humic acid,as a natural organic matter,has a certain number of free radicals in the natural water body,and it can exchange,chelate with metal ions.In this paper,?-FeOOH and ?-FeOOH were synthesized by hydrothermal synthesis of ferrous sulfate and ferrous chloride.The influence of different pH value,temperature,initial concentration and coexisting ions on the adsorption of arsenic by hydroxyl iron oxide in the presence of HA was investigated.The effect of pH showed that,In the absence of HA,pH reached 11,the removal rate of As(?)was reduced by?-FeOOH.Acid and weak alkaline conditions are conducive to the removal of As(?).When pH>9,with the increase of pH,the removal rate decreased.When HA is present,the removal of As is inhibited.Adsorption thermodynamic results showed that the removal rate of As was increased with the increase of the temperature.In the presence of HA,the removal of As could inhibit.The thermodynamic adsorption process is more in line with the Langmuir isotherm and the removal rate decreases with the increase of HA concentration.HA and As(III)or As(V)existence of dual phase adsorption system weaker than As(III)and As(V)adsorption alone,The inhibition of HA on As(?)is less than As(?),and the pseudo two order kinetic equation has better simulation effect.The pseudo two order kinetic equation is better.The analytical results show that the adsorption of ?-FeOOH has high stability on As removal,and HA is not easy to be replaced.The absorption edge results show that at different pH,HA and As interact with each other which indicates that As and HA compete with each other on the adsorbent surface.The effect of phosphate,sulfate and silicate on the removal of As was obvious.The results showed that the removal of As(?)and As(?)were similar on the effect of pH by ?-FeOOH,The effect of pH showed that,In the absence of HA,pH>9,the removal rate of As(?)by ?-FeOOH was reduced to half.Under acidic condition,the removal rate of As(?)reached the maximum,and the removal rate decreased with the increase of pH.In the presence of HA,the adsorption of HA on As was inhibited and the removal rate was decreased by about 2%.The adsorption thermodynamics results show that with the increase of temperature,the removal rate of As increased,Langmuir equation fit better on the As(?)thermodynamic adsorption,Freundlich isotherm is more in line with As(?)adsorption.And the inhibition of HA is proportional to its concentration.The results of adsorption kinetics showed that HA had an inhibitory effect on the adsorption of As in the presence of HA,and the inhibitory effect of HA on As was significantly higher than that of As(?),The pseudo two order kinetic simulation is better than the first order kinetic simulation.The analytical results show that the competitive adsorption of HA is weaker than As,and the adsorbed As is not replaced by HA in solution.The results of absorption edge show that,under different pH conditions,the effect of As on the absorption edge of HA is much larger than that of HA on the absorption edge of As,which indicates that the adsorption site capacity of HA on the surface of ?-FeOOH isweaker than that of As.The effect of phosphate and silicate on the removal of arsenic is the most important.Adsorption As before and after by ?-FeOOH??-FeOOH through ainfrared(FT-IR)and X ray photoelectron spectroscopy(XPS)analysis showed that,?-FeOOH removal of arsenic mainly by electrostatic adsorption and ligand exchange and sulfate adsorption agent on the surface of ion exchange.?-FeOOH removal of arsenic is mainly through electrostatic adsorption and coordination body and exchange of chloride ion and adsorbent surface exchange.The HA 3D fluorescence spectra(3DEEMs)analysis,HA competes with As on the surface of the adsorbent to influence the migration and transformation of arsenic,but on the surface of ?-FeOOH,the competition of HA is weaker than As.To understand the reaction mechanism of humic acid on the adsorption of arsenic by FeOOH could provide a theoretical basis for the study of the influence of natural organic matter on the removal of arsenic from iron minerals in natural environment. |
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