Two hypercrosslinked polymeric adsorbents NG-99 and NG-100 were employed to remove four phenylhydrazine derivatives, phenylhydrazine (PH), 1-methyl-1-phenylhydrazine (1-MPH), 1-acetyl-2-phenylhydrazine (1-APH) and p-rnethylphenylhydrazine (p-MPH) from aqueous solutions. A comparison of the thermodynamic behaviors against the two hypercrosslinked resins and the conventional macroporous resin Amberlite XAD-4 was made. It was found that the equilibrium adsorption data for the four phenylhydrazine compounds fitted well to the Langmuir isotherms, suggesting a physical and mono-molecular layer adsorption process. The results showed that the equilibrium adsorption capacities of PH, 1-MPH, 1-APH and p-MPH on NG-99 and NG- 100 were all higher than that on Amberlite XAD-4 by 20-70%, which may be attributed to the uniform micropore structure and partial polarity on the network of the hypercrosslinked resins, as well as the enhanced pi-pi interactions and the better compatibility between the adsorbates and adsorbents, and NG-100 demonstrated the highest adsorption capacity. The sorption enthalpies were calculated to interpret the adsorption mechanism. In addition a kinetic study of the sorption of PH onto NG-100 was also carried out. A first-order irreversible reaction rate equation was assumed for the sorption system and was suitable to describe the physisorption process. The hypercrosslinked polymer NG-100 exhibited optimum potential for removing PH derivatives from aqueous solutions. (C) 2003 Elsevier B.V. All rights reserved.