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A novel adsorbent (Fe3O4/HCO) was prepared via co-precipitation from a mix of ferriferrous oxide and a Ce-rich waste industrial sludge recovered from an optical polishing activity. The effect of system parameters including reaction time, pH, dose, temperature as well as initial concentration on the adsorption of Sb(III) were investigated by sequential batch tests. The Sb(III)/Fe3O4/HCO system quickly reached adsorption equilibrium within 2 h, was effective over a wide pH (3–7) and demonstrated excellent removal at a 60 mg/L Sb(III) concentration. Three isothermal adsorption models were assessed to describe the equilibrium data for Sb(III) with Fe3O4/HCO. Compared to the Freundlich and dubinin-radushkevich, the Langmuir isotherm model showed the best fit, with a maximum adsorption capacity of 22.853 mg/g, which exceeds many comparable absorbents. Four kinetic models, Pseudo-first-order, Pseudo-second-order, Elovich and Intra-particle, were used to fit the adsorption process. The analysis showed that the mechanism was pseudo-second-order and chemical adsorption played a dominant role in the adsorption of Sb(III) by Fe3O4/HCO (correlation coefficient R2 = 0.993). Thermodynamic calculations suggest that adsorption of Sb(III) ions was endothermic, spontaneous and a thermodynamically feasible process. The mechanism of the adsorption of Sb(III) on Fe3O4/HCO could be described by the synergistic adsorption of Sb (III) on Fe3O4, FeCe2O4 and hydrous ceric oxide. The Fe3O4/HCO sorbent appears to be an efficient and environment-friendly material for the removal of Sb(III) from wastewater.

The nutrient (nitrogen and phosphorus) removal from municipal wastewater was investigated by sequencing batch reactor (SBR) with different aeration rates. The results indicated that the removal performances of nitrogen and phosphorus both increased first and then decreased with increasing aeration rates, and that the aeration rate should be controlled at 25 L.h–1 (dissolved oxygen = 2.7 mg.L–1) in order to achieve ideal removal efficiencies of total nitrogen (TN) and total phosphorus (TP). Aeration rate had a prominent effect on the occurrence of nitrification and denitrification (SND), and excessive aeration would weaken nitrogen removal during SND process. In contrast, excessive aeration had no effect on the release rate of the anaerobic phosphorus, and the decrease of these polyhydroxyalkanoates (PHAs) could significantly influence phosphorus uptake, which was very essential for controlling the biological phosphate removal.