Nanoflower-like MoS₂ deposited on the surface of rectangular CaTiO₃(CTO) was designed and synthesized via a simple template-free strategy. Through SEM, TEM, and other characterization methods, the MoS₂ nanoflowers were confirmed to be well deposited on the surface of CTO. LED was used as the visible light source, and rhodamine B (RhB) in an aqueous solution was used as the model pollutant to assess the photodegradation activity of the samples. The results showed that the MoS₂/CaTiO₃(MCTO) composite significantly improved the photocatalytic degradation of rhodamine B (RhB) in water, compared with a single CTO, and with the MCTO-2 composite photocatalysts, 97% degradation of RhB was achieved in 180 min, and its photocatalytic activity was about 5.17 times higher than that of the bare CTO. The main reasons for enhancing photocatalytic performance are the strong interaction between the nanoflower-like MoS₂ and rectangular CTO, which can lead to the effective separation of electron transfer and photoexcited electron–hole pairs in MCTO composites. This work provides a new notion for researching an effective method of recycling catalytic materials.

The removal of nitrate (NO₃⁻-N) and antibiotics in aquaculture tail water is urgent and necessary. A lab-scale up-flow immobilized biofilter (I-BF) filled with polyurethane foam (PUF) carriers and a microbial consortium was developed for simultaneous removal of nitrate and tetracycline (TC). The denitrification and TC removal performance of the I-BF reactor was investigated under different TC concentrations (0, 10, 50, 100 mg·L⁻¹), carbon/nitrogen (C/N) ratio (2, 4, 5, 6) and hydraulic retention times (HRT) (4, 8, 12 h). Simultaneous removal of nitrogen and TC was achieved by the I-BF reactor. Low TC concentration (≤50 mg·L⁻¹) had little effect on nitrogen removal. The denitrification performance of the I-BF reactor was inhibited at high TC load, which may be attributed to the damage of cell membranes and the inhibition of the intracellular denitrification enzymes’ activities. The optimal C/N ratio and HRT were 5 h and 8 h with almost complete denitrification and high TC removal efficiency (73.46%) at influent NO₃⁻-N and TC concentrations of 100 mg·L⁻¹ and 50 mg·L⁻¹, respectively. The I-BF reactor proposed in this study has promising applications such as the treatment of piggery wastewater, aquaculture tail water and pharmaceutical wastewater co-contaminated with nitrate and antibiotics.

The photocatalytic degradation process has been recognized as a low-cost, environmentally friendly and sustainable technology for water and wastewater treatment. As a key carrier of the photocatalytic process, the semiconductor TiO₂ has been used in many studies. Analysis and modelling of hydrodynamics in the three-phase flow system can provide useful information for process design, operation and optimization of the three-phase flow photocatalytic reactor, which requires research on the mixing and flow characteristics of the interphase regions in the reactor. In this study, we modelled the hydrodynamics in an internal air-lift circulating photocatalytic reactor using an Eulerian multi-fluid approach. Localized information on phase holdup, fluid flow patterns and mixing characteristics was obtained. The simulation results revealed that the distribution of solid particle concentration depends on the flow field in the internal air-lift circulating photocatalytic reactor. The distance between the draft tube and wall of the reactor and changes in the superficial gas velocity (U_g) were found to be influential factors in reactor performance. The computational model developed could support optimizing reactor design to improve the hydrodynamics and provide guidance for scale-up.