Accelerated transformation of sodium dodecylbenzene sulfonate surfactant in the UV/chlorine process: Kinetics and formation of chlorinated disinfection by-products

Sodium dodecylbenzene sulphonate (SDBS) present in detergents: action on the gills, skin, and blood of D. rerio fish

1. Sodium dodecylbenzene sulphonate (SDBS) is one of the surfactants used worldwide in detergents which, due to high residual discharges, has great potential to cause ecotoxicological impacts. Therefore, the sublethal effects of SDBS on the gills and skin of male Danio rerio fish were investigated.

2. The fish were distributed into three groups: GC (control), GT1 (0.25 mg/L of SDBS), and GT2 (0.5 mg/L of SDBS) and exposed for 21 days. After the experiment, histopathological analyses of the gills, histochemical analyses (counting of mucous cells), and biochemical analyses (antioxidant defense enzyme analysis, SOD, and CAT) were conducted.

3. A significant increase (p < 0.05) in the incidence of circulatory disorders, progressive, and regressive alterations occurred in the GT1 and GT2 groups. Due to these changes, the total histopathological index of the gills was higher in these groups. Mucous cells in the gills and skin increased. There was an increase in SOD activity and a reduction in CAT activity in these groups. Haematology revealed neutrophilia and lymphocytosis in the blood of GT1 and GT2.

4. The results clearly demonstrate that a 21-day exposure to SDBS causes severe morphophysiological damage to the gills, skin, and blood of D. rerio fish.

High-performance Cu/Mn modified ceramsite as a persulfate activator to degrade oxytetracycline in batch Erlenmeyer flask and continuous-flow fixed-bed column systems: An exploration of its practicability and non-radical mechanisms

Persulfate non-radical oxidation have excellent catalytic capability for degrading specific contaminants in complicated water environments. Nevertheless, the preparation of high-performance activators and their application in actual water treatment in continuous flow mode are still scarce and unsatisfactory. In this work, copper-, manganese-, and copper/manganese-doped ceramsites (Cu-C, Mn-C and Cu/Mn-C), successfully fabricated through a facile impregnation-calcination approach, were characterized and evaluated for their performance to activate potassium peroxydisulfate (PDS) and degrade oxytetracycline (OTC) under different pH, ceramsite dosages, and PDS dosages. Compared with Cu-C and Mn-C, Cu/Mn-C showed the highest OTC degradation rate (0.0264 min-1) via activating PDS with an OTC removal efficiency of 98.2% in 240 min at an initial OTC concentration of 40 mg/L. The removal efficiency of OTC by Cu/Mn-C only decreased to 92.8% after 5 cycles; the activating ability of the used Cu/Mn-C was almost completely recovered through 2 h of calcination at 500 °C. The results of electron paramagnetic resonance and radical quenching suggest that singlet oxygen (1O2) was unveiled to be the dominant reactive oxygen species (ROS) for contaminant degradation, originating from the regrouping of superoxide ions or reduction of active Cu/Mn sites. Synergies between Cu and Mn species to enhance ROS yield were the primary activating mechanisms. Six possible routes of OTC decomposition were inferred. Additionally, Cu/Mn-C behaved excellently in treating an actual wastewater using a continuous flow fixed-bed reactor. It is believed that this novel Cu/Mn-C/PDS system may create a fresh path to design effective and cheap metal-ceramsite hybrid activators for degrading recalcitrant contaminants in the actual application process.