| Arsenic is a kind of metalloid element with high toxicity.In natural environments,there are four valence states of arsenic:-3,0,+3 and +5.While soluble arsenic exists in two predominant species,arsenate[As(?)]and arsenite[As(?)].Arsenic can be accumulated in the body by direct drinking water or food chain enrichment,and pruduce carcinogenic,teratogenic and mutagenic effects on organisms.Therefore,arsenic remval has aroused the researchers' concern.Compared with other traditional treatment technologies for arsenic removal,adsorption is considered one of the most popular and practical methods for arsentic removal.However,the adsorption material is the key to improve the arsenic removal efficiency.Our exisiting studies indicated that iron manganese oxides has good adsorption effect on the removal of As(?)and As(?).And cerium can reinforce the matereial performance when combined with other materials.Fe-Mn-Ce trimetal oxide nanoadsorbent were synthesized,which combined the Fe-Mn bimetal oxide and the cerium oxide.And a systematic investigation,including characterization of adsorbent,evaluation of arsenic adsorption behavior and removal mechanisms was conducted in present paper.The main results showed as following:1.The arsenic adsorption on Fe-Mn-Ce trimetal oxide is better than the Fe-Mn bimetal oxide.2.The Fe-Mn-Ce trimetal oxide is aggregates of nanosized particles and is mainly in amorphous form.It has a high specific area of 227 m2·g-1,a pore volume of 0.28 cm3·9-1 and an isoelectric point of 5.6.3.The Fe-Mn-Ce trimetal oxide showed better adsorption property for both As(?)and As(?)removal.And when pH was 7.0,the maximal adsorption capacities of As(?)and As(?)were 133 mg·g-1 and 70.0 mg·g-1,respectively.This indicated that the adsorption material have better adsorption effect on As(?).The adsorption speed of As(?)and As(?)was fast and chemical adsorption was the finite step.The As(?)and As(?)adsorption on Fe-Mn-Ce trimetal oxide is pH-dependent,however,ionic strength has little effect on arsenic adsorption.The effects of coexisting anions on arsenic adsorption decrease in the order of:PO43->SiO32->CO32->SO42-.Cation Ca2+,Mg2+ and organic matter had little effects on arsenic adsorption.4.The Fe-Mn-Ce trimetal oxide adsorbent has better regeneration performance.After stripping of arsenic by a sodium hydroxide solution,it can be reused for many times.Under the condition of different pH,the concentration of iron,manganese,cerium element from the adsorbent was very low and it can not produce secondary pollution to water.5.As(?)and As(?)was removed by forming an inner-sphere complex on surface of the adsorbent.However,The removal mechanism of As(?)is an oxidation coupled with sorption approach and is of great differert from that of As(?).In conclusion,the Fe-Mn-Ce trimetal oxide adsorbent showed good adsorption properties of arsenic and it can be resued after regenerating effectively by alkaline liquor.Therefore,it is a promising adsorption for arsenic removal. |
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