Removal of nickel ions and methylene blue dyes from aqueous solutions using alkaline algae biomass

The sorption of nickel (II) and methylene blue dye (MB) from aqueous solution by alkaline treated algae biomass was investigated. 0.05 M NaOH resulted in increasing the removal efficiency of algae biomass from 77.48 to 97.43% and from 79.71 to 97.53 % for Ni (II) and MB, respectively. Pseudo first order, pseudo second order and intra- particle diffusion kinetic models were tested, good coefficients of determination (R2) were attained from pseudo second order kinetic model for both contaminants; therefore, chemical adsorption was the mechanism that governed the sorption process by alkaline treated algae. The data were best fitted to Langmuir isotherm model and a maximum sorption capacity achieved were 2.889 mg/g for Ni (II) and 6.406 mg/g for MB. The separation factor shows irreversible isotherm type due to RL  1 for both contaminants. Alkali pretreatment of algae mixture could be an effective and low cost strategy for enhancing Ni (II) and MB sorption from aqueous solution.