Enhancement of Sono-Fenton by P25-Mediated Visible Light Photocatalysis: Analysis of Synergistic Effect and Influence of Emerging Contaminant Properties

Systematic study of the synergistic and kinetics effects on the removal of contaminants of emerging concern from water by ultrasound in the presence of diverse oxidants

The enhancement of the ultrasound system by adding diverse oxidants to remove a model contaminant (acetaminophen, ACE) in water was investigated. Different parameters were evaluated to study their effect on both the degradation kinetics and the synergy of the combination. The variables studied were the ultrasonic frequency (575, 858, and 1135 kHz), type of oxidant (hydrogen peroxide, sodium peroxydisulfate (or persulfate, PDS), and potassium peroxymonosulfate (PMS)), ACE concentration (4, 8, and 40 µM), and oxidant concentration (0.01, 0.1, 1, and 5 mM). Particular interest was placed on synergistic effects, implying that one process (or both) is activated by the other to lead to greater efficiency. Interestingly, the parameters that led to the higher synergistic effects did not always lead to the most favorable degradation kinetics. An increase in ACE removal of 20% was obtained using the highest frequency studied (1135 kHz), PMS 0.1 mM, and the highest concentration of ACE (40 µM). The intensification of degradation was mainly due to the ability of ultrasound to activate oxidants and produce extra hydroxyl radicals (HO•) or sulfate radicals (SO4•-). Under these conditions, treatment of ACE spiked into seawater, hospital wastewater, and urine was performed. The hospital wastewater matrix inhibited ACE degradation slightly, while the urine components inhibited the pollutant degradation completely. The inhibition was mainly attributed to the competing organic matter in the effluents for the sono-generated radical species. On the contrary, the removal of ACE in seawater was significantly intensified due to "salting out" effects and the production of the strong oxidant HOCl from the reaction of chloride ions with PMS.

Advances on sonophotocatalysis as a water and wastewater treatment technique: efficiency, challenges and process optimisation

Due to water shortage and increased water pollution, various methods are being explored to improve water quality by treating contaminants. Sonophotocatalysis is a combination of two individual water treatment processes i.e., photocatalysis and sonocatalysis. With advantages including shorter reaction times and enhanced activity, this technique shows possible futuristic applications as an efficient water treatment technology. Herein, background insight on sonophotocalysis as a water and wastewater treatment technique as well as the general mechanism of activity is explained. The commonly used catalysts for sonophotocatalytic applications as well as their synthesis pathways are also briefly discussed. Additionally, the utilisation of sonophotocatalysis for the disinfection of various microbial species as well as treatment of wastewater pollutants including organic (dyes, pharmaceuticals and pesticides) and inorganic species (heavy metals) is deliberated. This review also gives a critical analysis of the efficiency, enhancement strategies as well as challenges and outlooks in this field. It is thus intended to give insight to researchers in the context of facilitating future developments in the field of water treatment, and advancing sonophotocatalysis towards large-scale implementation and commercialization.

Phthalate esters: occurrence, toxicity, bioremediation, and advanced oxidation processes

Phthalic acid esters are emerging pollutants, commonly used as plasticizers that are categorized as hazardous endocrine-disrupting chemicals (EDCs). A rise in anthropogenic activities leads to an increase in phthalate concentration in the environment which leads to various adverse environmental effects and health issues in humans and other aquatic organisms. This paper gives an overview of the research related to phthalate ester contamination and degradation methods by conducting a bibliometric analysis with VOS Viewer. Ecotoxicity analysis requires an understanding of the current status of phthalate pollution, health impacts, exposure routes, and their sources. This review covers five toxic phthalates, occurrences in the aquatic environment, toxicity studies, biodegradation studies, and degradation pathways. It highlights the various advanced oxidation processes like photocatalysis, Fenton processes, ozonation, sonolysis, and modified AOPs used for phthalate removal from the environment.

N-doped porous bowl-like carbon with superhigh external surface area for ultrafast degradation of bisphenol A: Key role of site exposure degree

High-temperature nitrogen (N) doping boosts the activity of biochars for peroxymonosulfate (PMS) activation, but the N heat loss causes the unsatisfactory catalytic efficiency. Improving the surface area for obtaining the high exposure of N sites is a promising solution. Herein, a soft template-KHCO₃ etching strategy is used to synthesize the N-doped porous bowl-like carbon (NPBC) with ultrahigh external surface area (1610.8 m² g^-1). The bowl-like structure eliminates inert bulk interior and allows unobstructed mass transfer of reactants onto both outer and inner surfaces, while the large pore channels by KHCO₃ etching further improves the exposure degree of limited N sites. Although NPBC has only 0.43% N content, 93.1% of bisphenol A (BPA) is removed within 1 min through the electron-transfer pathway by fully utilizing the N active centers, and the kinetic rate constant (k) reaches 5.29 min^-1, exceeding reported values by 2-270 times. Moreover, the NPBC/PMS system possesses excellent applicability for various organics and conditions, effectively mineralizes BPA and reduces effluent biotoxicity. A quantitative index W representing N exposure degree is first proposed and shows high linearity with the k values of BPA degradation (R²=0.992, 0 <W<3750 m² g^-1%^-1), proving the critical role of W in determining catalytic efficiency.

A Comparison Study between Wood Flour and Its Derived Biochar for the Enhancement of the Peroxydisulfate Activation Capability of Fe3O4

In this study, both wood flour (WF) and wood flour-derived biochar (WFB) were used as supports for Fe3O4 to activate peroxydisulfate (PDS). The role of different carriers was investigated emphatically from the aspects of catalyst properties, the degradation kinetics of bisphenol A (BPA), the effects of important parameters, and the generation of reactive oxygen species (ROS). Results showed that both WF and WFB could serve as good support for Fe3O4, which could control the release of iron into solution and increase the specific surface areas (SSAs). The WFB/Fe3O4 had stronger PDS activation capability than WF/Fe3O4 mainly due to the larger SSA of WFB/Fe3O4 and the PDS activation ability of WFB. Both radical species (•OH and SO4•−) and non-radical pathways, including 1O2 and high-valent iron-oxo species, contributed to the degradation of BPA in the WFB/Fe3O4–PDS process. Moreover, the WFB/Fe3O4 catalyst also showed stronger ability to control the iron release, better reusability, and higher BPA mineralization efficiency than WF/Fe3O4.