Removal of Fulvic Acids from Aqueous Solutions via Surfactant Modified Zeolite1

A surfactant modified zeolite (SMZ), i.e., a zeolite modified by using hexadecyl trimethyl ammonium bromide (HDTMA) was used to remove fulvic acids (FA) from aqueous solution. The effects of the relevant parameters, such as the loading level of HDTMA, the contact time, the initial FA concentration, the pH, and the types of the metal cations and organics were examined. The results show that SMZ with an HDTMA loading-level of 120% of the external cation exchange capacity (ECEC) of zeolite exhibits the best performance. Although the removal of fulvic acids by SMZ occurs rapidly within the first 30 min of the contact time, a contact time of at least 4 h is required to attain the adsorption equilibrium. The removal capacity of FA by SMZ decreases with the increase of the initial FA concentration. The pH has an effect on the FA removal efficiency because it can influence the characteristics of the FA molecules. The removal of FA is considerably enhanced by Ca2+ or Mg2+ ions and is adversely affected by phenol or pentachlorophenol(PCP). Under the optimum conditions, 98% of FA could be removed by SMZ. Furthermore, the desorption of FA and the regeneration of SMZ were studied. The results show that a 30% ethanol solution is sufficient for the regeneration of SMZ.