Study On Adsorption Materials And Their Arsenic Removal Properties In Acidic Water

The metallurgy and sulphuric-acid industries let out a vast amount of arsenic-contained waste acid,in which the sulphuric acid content can reach 10-15wt.%,and a certain amount of valuable metals are also contained.Lime neutralization-precipitation method is usually used to process waste acid in industry.However,this method cannot recover the valuable metals and sulphuric acid from the waste acid;meanwhile,a large amount of gypsum waste will be produced.Therefore,how to deal with industrial waste acid efficiently is of significantly scientific and technic interests.Adsorption is an important method for selective arsenic removal because of its merits such as simple operation,large adsorption capacity,low adsorption equilibrium concentration and reproducible adsorbents.In this paper,the adsorption behaviors of arsenic in strong acid aqueous solution were studied by using acid-resistant gel-type ion-exchange resin and Ti₃SiC₂ oxidation-derivatives TiO₂ as adsorbent materials.Their adsorption properties were evaluated and the related adsorption mechanisms were discussed.The main research contents are as follows.（1）The adsorption performance of gel-type ZJ517 resin for pentavalent arsenic in strong acidic water was studied by static and dynamic adsorption experiments.The effects of processing conditions such as acidity,temperature and flow rate on arsenic adsorption were investigated.Meanwhile,the effect of desorption solution composition and desorption conditions on desorption efficiency was studied.The results showed that the maximum static adsorption capacity of the resin for pentavalent arsenic was 24.15 mg·g^-1 at 293K and 4 M H⁺concentration.In the dynamic adsorption experiments,the adsorption capacity can reach 32.71 mg·g^-1when the H⁺concentration was 4 M,the temperature was 293K and the flow rate was5 BV·h^-1.The maximum desorption efficiency can reach 92.53%by using the 2 M H₂SO₄ desorption solution containing 1%thiomalic acid.As such,recycling of the resin can be realized.（2）The adsorption performance of ZJ517 resin for trivalent arsenic in strong acid water was evaluated by static adsorption and dynamic adsorption-desorption experiments.The effects of static and dynamic adsorption conditions on the adsorption of arsenic on this resin were studied and the effects of desorption solution composition and desorption conditions on the desorption efficiency were also studied.The results showed that the maximum adsorption capacities of the resin for arsenic trivalent were 13.12 mg g^-1 and 24.46 mg g^-1 for static and dynamic adsorption in strong acidic water at 293K,respectively.The desorption solution was composed of 2M H₂SO₄ solution and 0.5%thiomalic acid.The maximum desorption efficiency can reach 97.5%.After repeated cycles,desorption efficiency could still be maintained above 90%,which indicated the good stability of the resin.（3）The porous Ti₃SiC₂-oxidized derivative TiO₂ modifications were used as the adsorption material and their adsorption performances for arsenic in strong acid water were investigated.The experimental results showed that two different oxidation derivatives,namely anatase and rutile,could be obtained by pre-oxidizing the reactively synthesized porous Ti₃SiC₂ at high temperatures.Surface hydroxylation of oxidized derivatives could be realized by hydrothermal treatment and NaOH treatment.It was found that the arsenic adsorption capacities of different hydrothermal-treated TiO₂ derivatives were weak,while the arsenic adsorption capacities of TiO₂ derivatives treated by NaOH were improved.The maximum adsorption capacity of trivalent arsenic on NaOH-treated anatase TiO₂ in the strong acid water was 3.02 mg·g^-1 at 303K,while that of rutile TiO₂ treated by NaOH hydrothermal treatment was only 0.28 mg·g^-1.