Villaverde Jaime, Maqueda Celia, Morillo Esmeralda
Instituto de Recursos Naturales y Agrobiología (CSIC), Sevilla, Spain.
J Agric Food Chem. 2005 Jun 29;53(13):5366-72. doi: 10.1021/jf0502449.
The effect of beta-cyclodextrin (beta-CD) on the removal of the herbicide norflurazon (NFL) from soils has been investigated. The interaction of NFL with beta-CD in solution yielded the formation of a water-soluble inclusion complex at 1:1 stoichiometric ratio, which gave an increase in NFL solubility. Desorption studies of NFL previously adsorbed on six soils of different characteristics have been performed in the presence of 0.01 M beta-CD or 0.01 M Ca(NO(3))(2) as extractant solutions. Positive hysteresis was observed in all soils when 0.01 M Ca(NO(3))(2) solution was used, indicating that desorption of NFL from these soils was not completely reversible. On the contrary, the application of beta-CD solutions to soils where NFL had been previously adsorbed increased very much its desorption, and a negative hysteresis was obtained for all soils studied; that is, more NFL was desorbed with respect to NFL adsorption isotherm. A clear relationship was observed between the physicochemical characteristics of the soils and the beta-CD concentration necessary to remove the herbicide, the percentages of desorption observed for each soil being inversely related to the values obtained for the Freundlich sorption capacity parameter of the herbicide, K(f). In general, high desorption yields can be obtained with very low beta-CD concentrations, which is an important advantage from an economic point of view, although in those soils that present an extremely high NFL adsorption, higher amounts of beta-CD should be used. The results obtained indicate the high extracting power of beta-CD toward the herbicide previously adsorbed on the soils and the potential use of beta-CD for in situ remediation of pesticide-contaminated soils.
研究了β-环糊精（β-CD）对从土壤中去除除草剂氟乐灵（NFL）的效果。NFL与β-CD在溶液中的相互作用以1:1化学计量比形成了水溶性包合物，这使得NFL的溶解度增加。以0.01 Mβ-CD或0.01 M Ca(NO₃)₂作为萃取剂溶液，对预先吸附在六种不同特性土壤上的NFL进行了解吸研究。当使用0.01 M Ca(NO₃)₂溶液时，在所有土壤中均观察到正滞后现象，这表明NFL从这些土壤中的解吸并非完全可逆。相反，将β-CD溶液应用于预先吸附了NFL的土壤中，极大地增加了其解吸量，并且在所研究的所有土壤中均获得了负滞后现象；也就是说，相对于NFL吸附等温线，有更多的NFL被解吸。观察到土壤的物理化学特性与去除除草剂所需的β-CD浓度之间存在明显关系，每种土壤的解吸百分比与除草剂的弗伦德利希吸附容量参数K(f)的值呈反比。一般来说，使用非常低的β-CD浓度就能获得较高的解吸率，从经济角度来看这是一个重要优势，不过对于那些对NFL吸附极高的土壤，应使用更高量的β-CD。所得结果表明β-CD对预先吸附在土壤上的除草剂具有很高的萃取能力，以及β-CD在原位修复农药污染土壤方面的潜在用途。
