N/Fe/Zn co-doped TiO2 loaded on basalt fiber with enhanced photocatalytic activity for organic pollutant degradation.

To avoid the loss of catalytic material powder, a loaded catalytic material of TiO2 with basalt fiber as the carrier (TiO2@BF) was synthesized by an improved sol-gel method. The TiO2@BF was doped with different contents of N, Fe and Zn elements and was used to degrade rhodamine B (RhB) under ultraviolet light. The physical characterization analysis indicated that the co-doping of the N, Fe and Zn elements had the effects of reducing grain size, increasing sample surface area, and narrowing the electronic band gap. The electronic band gap of nitrogen-iron-zinc co-doped TiO2@BF (N/Fe/Zn_TiO2@BF) was 2.80 eV, which was narrower than that of TiO2@BF (3.11 eV). The degradation efficiency of RhB with N/Fe/Zn_TiO2@BF as a photocatalyst was 4.3 times that of TiO2@BF and its photocatalytic reaction was a first-order kinetic reaction. Quenching experiments suggested that the reactive species mainly include photoinduced holes (h+), superoxide radicals (˙O2 -) and hydroxyl radicals (˙OH). In brief, this study provides a prospective loaded catalytic material and routine for the degradation of organic contaminants in water by a photocatalytic process.

Combined impact of organic matter, phosphorus, nitrate, and ammonia nitrogen on the process of blackwater.

Blackwater events are frequently reported over the world and become a serious environmental problem. However, the mechanisms of blackwater occurrence are not fully understood yet. This study simulated the process of blackwater with the combined pollution in an orthogonal experiment, which had 4 factors (TOC, TP, NH4+-N, and NO3--N) and 4 levels (None, Low, Middle, and High). Results showed that the process of water condition changes was divided into two parts, which were "exogenous" and "algae-derived" blackwater, and the influence of four different pollutants on the occurrence of the blackwater was ranked as follows: TOC > TP > NO3--N > NH4+-N. With the increase of organic matter addition, the anaerobic condition in water was prolonged and the concentration of Fe2+ had a significant increase. In addition, under the None phosphorus condition, the descent rates of DO and COD in the water were reduced, and the algae bloom was obviously deferred. Moreover, the addition of organic matter or phosphorus changed the microbial community structure and led to different water processes. Particularly, only on the condition of the high content of TOC and phosphorus, the diversity of sulfate-reducing bacteria (e.g., Pseudomonas, Paludibacter, and Bacteroides) increased significantly, which accounted for 51.4%, causing the significant production of S2- in the water. Water's lack of phosphorus showed a low rate of decomposition of organic matter, which might be the result of a considerable increase in the abundance of aerobic Trichococcus and Malikia. This study shows that organic matter and phosphorus have synergistic effect on blackwater occurrence. In the treatment of blackwater, the exogenous pollutant control should reduce the discharge of organic pollutants, and endogenous control should focus on phosphorus abatement and reduce nitrogen control.