Heterogeneous Fenton-like removal of tri(2-chloroisopropyl) phosphate by ilmenite (FeTiO3): Kinetic, degradation mechanism and toxic assessment.

Tri(2-chloroisopropyl) phosphate (TCPP), a common organophosphate flame retardant, was frequently detected in the environment and posed threats to human health. In this work, the main component of ilmenite FeTiO3 was synthesized by the sol-gel method and employed as the catalyst for the degradation of TCPP by activating persulfate (PS) under UV irradiation. The degradation processes were fitted by the pseudo-first-order kinetic. The kobs value in UV/FeTiO3/PS system was up to 0.0056 min-1 and much higher than that in UV/PS (0.0014 min-1), UV/FeTiO3 (0.0012 min-1) and FeTiO3/PS (0.0016 min-1) systems, demonstrating a distinct synergistic effect in TCPP removal. The degradation efficiency of TCPP increased with the increase of UV intensity, PS concentration and catalyst dosage, and with the decrease of pH. By quenching experiment and EPR analysis, ·OH was confirmed to be the dominant radical in the reaction of the UV/FeTiO3/PS system. The possible degradation pathways of TCPP were dechlorination, dealkylation, and further oxidation of alkyl groups based on the theoretical calculation of frontier molecular orbits. The toxicity of degradation intermediates evaluated by luminescence inhibition rate of photoluminescence was higher than TCPP. Thus, TCPP can be degraded in the UV/FeTiO3/PS system effectively at the premise of introducing controlling measures to reduce the toxicity of degradation intermediates.

Perylene diimide supermolecule (PDI) as a novel and highly efficient cocatalyst for photocatalytic degradation of tetracycline in water: A case study of PDI decorated graphitic carbon nitride/bismuth tungstate composite.

Employing perylene diimide supermolecule (PDI) as metal-free cocatalyst, a novel PDI/g-C3N4/Bi2WO6 (PCB) photocatalyst was constructed for the effective degradation of antibiotics. Both the photocatalytic activity and photostability of g-C3N4/Bi2WO6 (gCB) were further improved after loading PDI. Under simulated sunlight illumination, the apparent rate constant of tetracycline (TC) degradation by PCB reached 2.6 times that of gCB. The photocatalytic activity of PCB still kept over 80% after 4 cycle experiments, while gCB only remained around 21%. The superior activity of PCB was ascribed to the synergism between the extended visible light absorption range through the participation of PDI cocatalyst and facilitated gCB-to-PDI photoelectron transfer. TC would finally be transformed into non-toxic ring opening products and mineralized. This work demonstrated that PDI was an excellent metal-free cocatalyst and exhibited great potential to boost the activity of photocatalysts.

A comparative study on adsorption behavior of iodinated X-ray contrast media iohexol and amidotrizoic acid by magnetic-activated carbon.

As persistent and ubiquitous contaminants in water, iodinated X-ray contrast media (ICM) pose a non-negligible risk to the environment and human health. In this study, we investigated the adsorption behavior of two typical ICM compounds, iohexol (IOH) and amidotrizoic acid (DTZ), on magnetic activated carbon. Theoretical investigations, using density functional theory, identified the molecule structures and calculated the molecular diameters of IOH (1.68 nm) and DTZ (1.16 nm), which revealed that ICM could be adsorbed by mesopores and larger micropores. Therefore, magnetic activated carbon with a porous structure was prepared by the co-precipitation method to investigate the adsorption mechanism of IOH and DTZ. MAC--5 (magnetic activated carbon with a theoretical iron oxide content of 37%) showed the best adsorption ability for both IOH and DTZ, with maximum adsorption capacities of 86.05 and 43.00 mg g-1, respectively. Adsorption kinetics and isotherm models were applied to explore the mechanisms involved, and the effects of solution pH, initial concentration, temperature, ionic strength, and natural organic matter were also investigated. The pore filling effect, π-π stacking, hydrogen bonding, and electrostatic interaction, were found to be the main adsorption mechanisms. The co-adsorption data showed that competition may occur in ICM coexisting environments. Interestingly, the used MAC--5 could be successfully regenerated and its adsorption efficiency did not decrease significantly after five cycles, indicating that it is a promising adsorbent for ICM. The results from this study provide some new insights for the treatment of water containing ICM.