| This paper studied the oxidative removal of4-tert-octylphenol (4-t-OP) in water suspension by synthetic δ-MnO2, degradation products and the influence of pH, initial concentration of reactant and δ-MnO2, and calculated the reaction orders as well. Moreover, the effects of metal ions on the removal of4-t-OP by synthetic δ-MnO2were also studied.Experimental results showed that δ-MnO2degraded4-t-OP rapidly with Mn2+ions generated, which correlated closely with pH and initial concentrations of reactant and δ-MnO2. Three degradation products had been detected at pH4.0in total. The apparent reaction order for4-t-OP and MnO2were both1.0at pH4.0, while the reaction order for H+was0.3between pH4.0and8.0. At pH4.0, the removal of4-t-OP by δ-MnO2achieved100%at reaction time of150min, but it was restrained when metal ions added. Ten metal ions had been tested, in general, the inhibition effect increased with the concentration of metal ions increased. However, the degree of inhibition changed as different tested metal ions added. Firstly, Pb2+and Mn2+had the strongest effect in the condition of pH4.0, next with the other heavy metal ions (Zn2+, Ni2+, Cd2+, and Cu2+), then the tested alkaline earth ions (Mg2+and Ca2+), except that the alkali metal ions (K+and Na+) had little influence on the removal of4-t-OP by δ-MnO2.The results of adsorption metal ions on δ-MnO2showed that Pb2+had the greatest attraction with δ-MnO2, next with heavy metal ions and alkaline earth metal ions. The inhibiting effects of metal ions depended on its occupying reactive sites on the δ-MnO2surface which competed with4-t-OP. Moreover, the degree of inhibition were contributed to the different adsorption capacities, surface structure change of δ-MnO2and the difference of metal free ion percentage in solution as well as metal ions radii. |
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