The removal of methylene blue from aqueous solution onto the raw, DAB and sulfuric acid pre-treated DAB over time are shown in Fig. 1. It is obvious from the figure that rapid decrease in solution phase concentration observed initially was followed by a slow decrease beyond 20 min in raw and defatted algal adsorbent. Levelling off was observed beyond 30 min in sulfuric acid pretreated defatted algal adsorbent. This may be due to the saturation of negative charges present on the surface of the adsorbent. Also, the initial slower rate of adsorption noticed with sulfuric acid pretreated DAB may be attributed to changes in the functional groups present on the surface as a result of acid pretreatment. The initial pH ofmethylene blue solution of different concentration (1–5 mg L1) were in the alkaline range (pH 7.3–7.8) and were adjusted to neutral pH for the adsorption studies. The final pH values at the equilibrium were observed to be in the acidic range (pH 6–6.5) in various experiments with different adsorbents. Two common isotherm equations namely Langmuir and Freundlich equations were applied to model the isotherms in the present study.