Abstract
AbstractSulphate is an important ion occurring in both natural waters and industrial effluents. Granular ferric hydroxide (GFH), a poorly crystallized β-FeOOH, was used to remove sulphate in a series of batch experiments. Sulphate removal increased with increase in GFH dose and more than 50% of the adsorption happened within the first 15 min of agitation. In addition, sulphate adsorption was influenced by pH and the optimum pH range was 2–7. Adsorption also increased by increasing temperature from 15 to 55°C, indicated the endothermic nature of the process. Among the co-existing anions, phosphate and bicarbonate strongly inhibited the sulphate removal. The kinetics of the process follows the pseudo-second-order with a high correlation coefficient value (R2 > 0.99). Equilibrium tests also showed that the sulphate removal by GFH fitted well with the Freundlich model, which indicated the multilayer adsorption of sulphate and heterogeneous distribution of adsorption sites on GFH surface.
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