HUMIC ACID ADSORPTION ON OXIDES:A MEANINGFUL COMPARISON OF DATA

摘要

Interaction of mineral particles with natural organic material(NOM,humic and fulvic acids)and model compounds is widely studied.Hydrophobic and coordinative interactions exist basically,however,the accumulation of organic acids at mineral-water interface exhibits both an electrostatic and a chemical feature;in principle,it is a ligand-exchange reaction,which takes place at an electrified interface(Tombacz,2003).The adsorbed amount of well-defined organic acids is given in molar amount related to unit mass or surface of adsorbent(mmol/g or mmol/m~2),while the mass of OM or C(mg/g or mg C/g and also mg/m~2)is used in the case of ill-defined natural acids(NOM,DOM,humic substances).If the well-and ill-defined acids are compared or a probable ligand exchange is supposed,the adsorbed amount is often re-calculated relating it to the carboxylic or total acidity of natural samples(e.g.Gu et al.,1995).The molar amount of acidic groups given in moles for dissolved OM is used in speciation calculation and modeling(e.g.Hees et al.,2001,Koretsky,2000).This work shows some advantages why to use a meaningful unit of adsorbed amount,which relates the molar amount of acidic functional groups of humic acid to 1 g solid phase,and only the material balance is supposed in the experiments to obtain it.