Adsorption of phenylhydrazine derivatives on hypercrosslinked polymeric adsorbents

Abstract

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-methylphenylhydrazine ( 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 π–π 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.