Efficient S-scheme heterojunction photocatalysts were prepared through in situ growth of AgBiO₃ on BiOBr.

Traces of Molybdenum (Mo) in drinking water pose potent dangers owing to its harmful effects on the health of humans. This study used nanoscale zero-valent iron (Fe⁰) supported by activated carbon (NZVI/AC) for removing Mo(VI) from raw water. In an attempt to gain an understanding of the various factors that affect the process, we designed the study to look into the impact of various experimental parameters including pH, adsorption kinetics, and coexisting ions on the Mo(VI) removal using fixed-bed column runs and a batch-adsorption method and for Mo(VI) removal using NZVI/AC. The optimum conditions were found to be pH 4.5 and an equilibrium time of 9 h and 72 h for simulation water (SW) and raw water (RW), respectively. The removal of Mo(VI) was remarkably inhibited by the presence of silicate (${\mathrm{SiO}}_4^{2-}$) and phosphate (${\mathrm{PO}}_4^{3-}$), while the impact of humic acid and some other anions was insignificant. Metal cations such as Fe³⁺, Al³⁺, Zn²⁺, and Ni²⁺ enhanced the adsorption of Mo(VI). The influent contaminant concentration Mo(VI) in raw water was found to be 0.1603 mg/L, the empty-bed contact time (EBCT) was 3 and 6 min, whereas the breakthrough empty-bed volumes were 800 and 1100 and at the value of 70 μg/L provided by WHO provisional guidelines, respectively.

Antimony (Sb) traces in water pose a serious threat to human health due to their negative effects. In this work, nanoscale zero-valent iron (Fe⁰) supported on activated carbon (nZVI) was employed for eliminating Sb(V) from the drinking water. To better understand the overall process, the effects of several experimental variables, including pH, dissolved oxygen (DO), coexisting ions, and adsorption kinetics on the removal of Sb(V) from the SW were investigated by employing fixed-bed column runs or batch-adsorption methods. A pH of 4.5 and 72 h of equilibrium time were found to be the ideal conditions for drinking water. The presence of phosphate (${\mathrm{PO}}_4^{3-}$), silicate (${\mathrm{SiO}}_4^{2-}$), chromate (${\mathrm{CrO}}_4^{2-}$) and arsenate (${\mathrm{AsO}}_4^{3-}$) significantly decreased the rate of Sb(V) removal, while humic acid and other anions exhibited a negligible effect. The capacity for Sb(V) uptake decreased from 6.665 to 2.433 mg when the flow rate was increased from 5 to 10 mL·min⁻¹. The dynamic adsorption penetration curves of Sb(V) were 116.4% and 144.1% with the weak magnetic field (WMF) in fixed-bed column runs. Considering the removal rate of Sb(V), reusability, operability, no release of Sb(V) after being incorporated into the iron (hydr)oxides structure, it can be concluded that WMF coupled with ZVI would be an effective Sb(V) immobilization technology for drinking water.

Proposed charge transfer and photocatalytic mechanisms over the AgBr/BiFeO ₃ heterojunction.

The effectiveness of nanoscale zero-valent iron(nZVI) immobilized on activated carbon (nZVI/AC) in removing antimonite (Sb(III)) from simulated contaminated water was investigated with and without a magnetic fix-bed column reactor. The experiments were all conducted in fixed-bed columns. A weak magnetic field (WMF) was proposed to increase the exclusion of paramagnetic Sb(III) ions by nZVI/AC. The Sb(III) adsorption to the nZVI and AC surfaces, as well as the transformation of Sb(III) to Sb(V) by them, were both increased by using a WMF in nZVI/AC. The increased sequestration of Sb(III) by nZVI/AC in the presence of WMF was followed by faster nZVI corrosion and dissolution. Experiments were conducted as a function of the pH of the feed solution (pH 5.0–9.0), liquid flow rate (5–15 mL·min⁻¹), starting Sb(III) concentration (0.5–1.5 mg·L⁻¹), bed height nZVI/AC (10–40 cm), and starting Sb(III) concentration (0.5–1.5 mg·L⁻¹). By analyzing the breakthrough curves generated by different flow rates, different pH values, different inlet Sb(III) concentrations, and different bed heights, the adsorbed amounts, equilibrium nZVI uptakes, and total Sb(III) removal percentage were calculated in relation to effluent volumes. At pH 5.0, the longest nZVI breakthrough time and maximal Sb(III) adsorption were achieved. The findings revealed that the column performed effectively at the lowest flow rate. With increasing bed height, column bed capacity and exhaustion time increased as well. Increasing the Sb(III) initial concentration from 0.5 to 1.5 mg·L⁻¹ resulted in the rise of adsorption bed capacity from 3.45 to 6.33 mg·g⁻¹.

A novel and highly efficient photocatalyst of a AgBiO₃/BiOCl heterojunction has been developed via a facile water bath and in situ precipitation method. The photocatalytic activities of the catalysts were investigated by the degradation of ciprofloxacin (CIP) under visible-light irradiation (>420 nm). The experiment results revealed that the photocatalytic performance of the optimized AgBiO₃/BiOCl heterojunction was much higher than pure AgBiO₃ and BiOCl. The degradation efficiency of the as-prepared AgBiO₃/BiOCl heterojunction (ABC-30) for CIP could reach 88% within 160 min, with 2.89 and 3.76 times higher activity than pure AgBiO₃ and BiOCl, respectively. The improved photocatalytic performance of AgBiO₃/BiOCl was attributed to the synergistic effect of the enhanced light absorption range and effective separation and transfer of the photo-induced charge carrier. The optimized heterojunction showed broad-spectrum catalytic activities towards various organic contaminants. The degradation efficiencies varied with the nature of the pollutant and decreased in the following order: Lanasol Red 5B (100%) > methyl orange (99%) > methylene blue (98%) > tetracycline (92%) > ciprofloxacin (88%) > ofloxacin (85%) > norfloxacin (78%) > rhodamine B (59%) > metronidazole (43%) > phenol (40%) > carbamazepine (20%). Furthermore, the trapping experiments and ESR indicated that superoxide radicals and holes were the main reactive species.