[Metal ions restrain the elimination of 4-tert-octylphenol by delta-MnO2]

The effect of metal ions on elimination of 4-t-OP by synthetic delta-MnO2 suspension at pH 4.0 was studied. Experiments indicated that the removal of 4-t-OP by delta-MnO2 achieved 100% at reaction time of 150 min. However, the removal of 4-t-OP by delta-MnO2 was restrained when metal ions were added, and the higher concentration of metal ion was, the stronger the inhibition produced. Additionally, there were apparent differences among the inhibitory effect of the tested metal ions. Firstly, Pb2+ and Mn2+ had the strongest effect at pH 4.0, followed by the transition metal ions, then the alkaline earth ions, while the alkali metal ions had little influence on the removal of 4-t-OP by delta-MnO2. Also comparing the adsorption results of metal ions by delta-MnO2, Pb2+ showed the greatest attraction with delta-MnO2, and among the other metal ions, transition metal ions were adsorbed a little more strongly on delta-MnO2 than alkaline earth metal ions. Consequences showed that the inhibitory effects of metal ions were due to their occupying reactive sites on delta-MnO2 surface, which competed with 4-t-OP. Moreover, the dissimilar suppressions were contributed by the different adsorption capacities, surface structure change of MnO2 and the difference of free metal ion percentage in solution as well as metal ions radii.