小分子有机酸对铁(氢)氧化物表面吸附的砷酸盐的解吸作用研究

The Desorption Characteristics of Arsenate from Iron( Hydr. ) Oxides by Low-molecular-weight Organic Acid

采用等温解吸热力学的方法,结合X射线衍射(XRD)与比表面积分析,研究了柠檬酸、草酸和NaCl溶液在pH 6.5环境下对水铁矿、针铁矿和赤铁矿表面吸附砷酸盐的解吸特性。实验结果表明,柠檬酸的解吸能力最强,草酸次之,NaCl最差。这主要是由于柠檬酸和草酸可通过配位交换和诱导配体溶解来解吸砷。但由于柠檬酸分子中可配位-OH多于草酸,因而其解吸能力强于草酸。赤铁矿吸附的砷酸盐最易解吸,而水铁矿吸附的砷酸盐则最难解吸,这与水铁矿具有较大的比表面积和较高的表面活性有关。

Arsenic adsorbed by iron （hydr.）oxides can be desorbed by low-molecular-weight organic acid.Through the method of isothermal desorption thermodynamics,combined with the techniques of X-ray diffraction （XRD） and specific surface area analysis,the desorption characteristics of arsenate adsorbed on the surface of ferrihydrite,goethite and hematite by citric acid,oxalic acid and NaCl solution were researched.The results showed that desorption ability of three desorption systems was as the order：citric acid ＞ oxalic acid ＞ NaCl solution.This could be attributed to the mechanism,that citric acid and oxalic acid could significantly promote desorption reaction through ligand exchange and ligand-enhanced dissolution.However,for the molecule of citric acid has more-OH ligand than oxalic acid,citric acid had greater desorption ability.Arsenic adsorbed by hematite was the easiest to be desorbed,whereas that adsorbed by ferrihydrite was the hardest to be desorbed,which was connected with larger specific surface area and higher surface activity of ferrihydrite.