The potential use of raw hard coals as low-cost adsorbents for the removal of 4-chlorophenol (4-CP) from aqueous solutions was examined. The effect of experimental parameters such as the pH and salt presence was evaluated. The kinetic studies showed the equilibrium time was found to be 2 h for all of the adsorbents and that the adsorption process followed the pseudo-second order kinetic model. The adsorption isotherms of the 4-CP on the hard coals were fitted to the Langmuir, Freundlich, Langmuir–Freundlich, Sips and Redlich–Peterson equations. Based on the results obtained, hard coals appear to be a promising adsorbent for the removal of some hazardous water pollutants, like 4-CP and related compounds.

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