The adsorption kinetics and isotherms of methylene blue (MB) on raw and thermally activated date pits, an agricultural solid waste, were investigated. The effects of activation temperature, solution temperature, solution pH, adsorbent particle size, and solution salinity on methylene blue removal were studied. Dye removal increased with an increase in solution pH but decreased with an increase in solution temperature. Raw date pits were effective in removing MB from aqueous solutions and are a promising adsorbent material. Unexpectedly, it was found that physical activation of date pits reduced the adsorption capacity. The measured adsorption kinetics was well described by a pseudo-second order kinetic model. Furthermore, the Langmuir isotherm model fitted the experimental equilibrium data. (C) 2003 Elsevier Ltd. All rights reserved.