Removal of paraquat and atrazine from water by montmorillonite‐(Ce or Zr) phosphate cross‐linked compounds

The adsorption of paraquat (1,1′‐dimethyl‐4,4′‐bipyridilium dichloride) and atrazine (6‐chloro‐N ²‐ethyl‐N ⁴‐isopropyl‐1,3,5‐triazine‐2,4‐diamine) from aqueous solution onto two montmorillonite‐(Ce or Zr) phosphate cross‐linked compounds at different temperatures (288 K and 308 K) has been studied using batch experiments. The adsorption isotherms obtained for paraquat on both adsorbents may be classified as H‐type of the Giles classification, which suggests that paraquat molecules are strongly adsorbed on the samples. For the adsorption of atrazine, L‐type isotherms were obtained for both montmorillonite‐(Ce or Zr) phosphate compounds, which suggests that these compounds have a medium affinity for this herbicide. The increase in temperature from 288 K to 308 K did not have any clear effect on the adsorption process of paraquat on either adsorbent whereas atrazine adsorption decreased slightly as temperature increased, possibly due to a mainly physical process. Fourier transform infrared (FTIR) spectroscopic studies revealed that at the pH generated by the adsorbents, the cationic herbicide interacted to a greater extent with the negatively charged surface of the adsorbents than did atrazine. For both herbicides, the Ce‐montmorillonite adsorbent showed a higher adsorption capacity than the Zr‐montmorillonite adsorbent. © 2000 Society of Chemical Industry