Removal of ortho-phosphate from aqueous solution by adsorption onto dolomite

• The removal of phosphate increased with increase in the ionic strength of solution.
• Equilibrium data were best described by the Redlich–Peterson isotherm.
• The overall kinetic data fitted very well for the pseudo-first-order rate model.
• Adsorption of phosphate onto dolomite was pH dependent.
• Phosphate adsorption favoured acidic conditions.

An experimental study on the adsorption of phosphate onto cost effective fine dolomite powder is presented. The effect of solution pH, solution ionic strength and adsorption isotherm were examined. The adsorption of phosphate was pH dependent and phosphate adsorption favoured acidic conditions. The adsorption was significantly influenced by solution ionic strength indicating outer-sphere complexation reactions. The experimental data further indicated that the removal of phosphate increased with increase in the ionic strength of solution. The experimental data were modelled with different isotherms: Langmuir, Freundlich and Redlich–Peterson isotherms. It was found that the Redlich–Peterson isotherm depicted the equilibrium data most accurately. The overall kinetic data fitted very well the pseudo-first-order rate model.

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