Advanced removal of phosphate from water by a novel lanthanum manganese oxide: Performance and mechanism

A novel lanthanum manganese oxide (La_0.96Mn_0.96O₃, LMO) was synthesized for advanced phosphate removal to alleviate water eutrophication process. The adsorbent had a specific surface area of 18.51 m²/g with pH at point of zero charge of 6.6; exhibited excellent phosphate adsorption capacity of 168.4 mg/g; performed well in a wide pH range from 3 to 10. The phosphate removal was not interfered by coexisting ions. The adsorbent remained 94.8% of its initial adsorption efficiency after reused for four times. Phosphate adsorption process conformed to pseudo-second-order model (R²=0.992) and Langmuir model (R²=0.935). Ligand exchange and electrostatic interaction played important roles in phosphate removal. In addition, the actual sewage secondary effluent was used to further verify the phosphate removal performance of LMO. For practical water treatment, the LMO showed high phosphate removal efficiency of 83.4% and low residual P of 0.1 mg/L. LMO is a potential candidate for low-concentration phosphate removal in real water environment.

MnCeOX with high efficiency and stability for activating persulfate to degrade AO7 and ofloxacin

An efficient MnCeO_x composite was successfully synthesized for activation of persulfate to degrade acid orange 7 (AO7) and ofloxacin. Pollutants degradation efficiencies with different catalytic systems were investigated. Results showed the performance of MnCeO_x was better than MnO_x, CeO₂ and MnO_x + CeO₂. Thus, there was a clear synergistic effect (Se) between Mn and Ce in the composite, and the Se was 73.8% for AO7 and 39.6% for ofloxacin. In addition, AO7 removal fitted 1st order reaction while ofloxacin removal fitted 2nd order reaction in MnCeO_x/persulfate system. Moreover, MnCeO_x/persulfate system showed high efficiency in pH range of 5-9. Mechanism analysis showed that SO₄^- and OH on the surface of the catalyst were the main active species, and O₂^- also played an important role in pollutants degradation. Furthermore, MnCeO_x showed high activity in actual water. Finally, the possible degradation pathway of ofloxacin was proposed according to the high performance liquid chromatography-mass spectrometry result. Overall, this study provides an efficient and stable catalyst to activate persulfate to degrade refractory pollutants.