Recent progress on ultrasound-assisted electrochemical processes: A review on mechanism, reactor strategies, and applications for wastewater treatment.

The electrochemical advanced oxidation processes (EAOPs) have received significant attention among the many other water and wastewater treatment technologies. However, achieving a desirable removal effect with a single technique is frequently difficult. Therefore, the integration of ultrasound technique with other processes such as electrocoagulation, electro-Fenton, and electrooxidation is a critical way to achieve effective organic pollutants decomposition from wastewater. This review paper is focused on ultrasound-assisted electrochemical (US/electrochemical) processes, so-called sonoelectrochemical processes of various organic pollutants. Emphasis was given to recently published articles for discussing the results and trends in this research area. The use of ultrasound and integration with electrochemical processes has a synergistic impact owing to the physical and chemical consequences of cavitation, resulting in enhancing the mineralization of organic pollutants. Various types of sonoelectrochemical reactors (batch and continuous) employed in the US/electrochemical processes were reviewed. In addition, the strategies to avoid passivation, enhanced generation of reactive oxygen species, and mixing effect are reviewed. Finally, concluding remarks and future perspectives on this research topic are also explored and recommended.

PPARα agonist fenofibrate attenuates iron-induced liver injury in mice by modulating the Sirt3 and ß-catenin signaling.

Iron accumulation is frequently associated with chronic liver diseases. However, our knowledge on how iron contributes to the liver injury is limited. Aberrant Wnt/ß-catenin signaling is a hallmark of several hepatic pathologies. We recently reported that peroxisome proliferator-activated receptor α (PPARα) agonist, fenofibrate, prevents iron-induced oxidative stress and ß-catenin signaling by chelating the iron. Sirtuin3 (Sirt3), a type of NAD+-dependent deacetylase, that plays a critical role in metabolic regulation was found to prevent ischemia reperfusion injury (IRI) by normalizing the Wnt/ß-catenin pathway. In the present study, we explored if fenofibrate prevents iron-induced liver injury by regulating the Sirt3 and ß-catenin signaling. In vitro and in vivo iron treatment resulted in the downregulation of PPARα, Sirt3, active ß-catenin, and its downstream target gene c-Myc in the mouse liver. Pharmacological activation of Sirt3, both in vitro and in vivo, by Honokiol (HK), a known activator of Sirt3, abrogated the inhibitory effect of iron overload on active ß-catenin expression and prevented the iron-induced upregulation of α smooth muscle actin (αSMA) and TGFß expression. Intrinsically, PPARα knockout mice showed significant downregulation of hepatic Sirt3 levels. In addition, treatment of iron overload mice with PPARα agonist fenofibrate reduced hepatic iron accumulation and prevented iron-induced downregulation of liver Sirt3 and active ß-catenin, mitigating the progression of fibrosis. Thus, our results establish a novel link between hepatic iron and PPARα, Sirt3, and ß-catenin signaling. Further exploration on the mechanisms by which fenofibrate ameliorates iron-induced liver injury likely has significant therapeutic impact on iron-associated chronic liver diseases.NEW & NOTEWORTHY Hepatic intracellular iron accumulation has been implicated in the pathophysiology of chronic liver diseases. In this study, we identified a novel mechanism involved in the progression of fibrosis. Excess iron accumulation in liver caused downregulation of PPARα-Sirt3-Wnt signaling leading to fibrosis. This work has significant translational potential as PPARα agonist fenofibrate could be an attractive therapeutic drug for the treatment of liver disorders associated with iron overload.

Performance of non-catalytic thermal hydrolysis and wet oxidation for sewage sludge degradation under moderate operating conditions.

Land disposal of waste activated sludge pose environmental risks due to the presence of heavy metals, pathogens and organic pollutants. Anaerobic digestion (AD) is one of the preferred treatment methods for sludge treatment. However, sludge hydrolysis is often found the rate-limiting step thereby reducing the biogas generation potential. Therefore, an effort was made to determine the optimum conditions for sludge solubilization by means of hydrothermal pretreatment. In this study, response surface methodology using Box Behnken design approach was used to optimize four hydrothermal reaction variables (i.e., initial pH, time, temperature, and oxidation coefficient) for sludge solubilization and total chemical oxygen demand (tCOD) reduction. Temperature and pH were found to be the most significant parameters. The maximum tCOD reduction and volatile suspended solids solubilization of 58% and 52%, respectively, were obtained at the following optimum conditions: temperature = 180 °C, time = 5 h, pH = 3.3 and oxidation coefficient = 0.5. Under similar conditions and alkaline pH, Maillard's reaction occurs which may have adverse impact on the performance of downstream AD process. The highest NH4+N and volatile fatty acids (VFAs) concentrations were detected in the treated sludge at the optimum conditions. The future studies should be aimed at the recovery of proteins, VFAs and biogas using appropriate methods.

Canonical Wnt Signaling in the Pathology of Iron Overload-Induced Oxidative Stress and Age-Related Diseases.

Iron accumulates in the vital organs with aging. This is associated with oxidative stress, inflammation, and mitochondrial dysfunction leading to age-related disorders. Abnormal iron levels are linked to neurodegenerative diseases, liver injury, cancer, and ocular diseases. Canonical Wnt signaling is an evolutionarily conserved signaling pathway that regulates many cellular functions including cell proliferation, apoptosis, cell migration, and stem cell renewal. Recent evidences indicate that iron regulates Wnt signaling, and iron chelators like deferoxamine and deferasirox can inhibit Wnt signaling and cell growth. Canonical Wnt signaling is implicated in the pathogenesis of many diseases, and there are significant efforts ongoing to develop innovative therapies targeting the aberrant Wnt signaling. This review examines how intracellular iron accumulation regulates Wnt signaling in various tissues and their potential contribution in the progression of age-related diseases.

Occurrence of organic micropollutants in municipal landfill leachate and its effective treatment by advanced oxidation processes.

Landfilling is the most prominently adopted disposal technique for managing municipal solid waste across the globe. However, the main drawback associated with this method is the generation of leachate from the landfill site. Leachate, a highly concentrated liquid consisting of both organic and inorganic components arises environmental issues as it contaminates the nearby aquifers. Landfill leachate treatment by conventional methods is not preferred as the treatment methods are not much effective to remove these pollutants. Advanced oxidation processes (AOPs) based on both hydroxyl and sulfate radicals could be a promising method to remove the micropollutants completely or convert them to non-toxic compounds. The current review focuses on the occurrence of micropollutants in landfill leachate, their detection methods and removal from landfill leachate using AOPs. Pharmaceuticals and personal care products occur in the range of 10-1 to more than 100 µg L-1 whereas phthalates were found below the detectable limit to 384 µg L-1, pesticides in the order of 10-1 µg L-1 and polyaromatic hydrocarbons occur in concentration from 10-2 to 114.7 µg L-1. Solid-phase extraction is the most preferred method for extracting micropollutants from leachate and liquid chromatography (LC) - mass spectrophotometer (MS) for detecting the micropollutants. Limited studies have been focused on AOPs as a potential method for the degradation of micropollutants in landfill leachate. The potential of Fenton based techniques, electrochemical AOPs and ozonation are investigated for the removal of micropollutants from leachate whereas the applicability of photocatalysis for the removal of a wide variety of micropollutants from leachate needs in-depth studies.

Hydrothermal carbonization of centrifuged sewage sludge: Determination of resource recovery from liquid fraction and thermal behaviour of hydrochar.

Safe disposal of the sludge generated from sewage treatment plant is a major challenge worldwide. Hydrothermal carbonization (HTC) is considered a potential pretreatment alternative for sewage sludge to facilitate the improved resource recovery. In the present study, the mixed centrifuged sewage sludge (CSS) was subjected to the HTC pretreatment to determine characteristics of the solid hydrochar (HC) and liquid fraction (LF) with a purpose of energy recovery and extraction of value-added compounds, respectively. HTC was performed in a high pressure batch reactor at 200 °C temperature for 1-8 h duration. The HC produced after HTC resembled with the low quality peat coal whereas the LF contained value-added chemicals such as humic acid (HA) and phosphate phosphorous (PO43-P). Using ammonium sulphate as 'salting out' agent, ~70% of the total HA (~15-16 g/L) could be recovered from the LF. Using the recovered HA, an improvement in the root and shoot lengths of the seeds could be observed. In the subsequent step, the total PO43--P recovery of ~80% was obtained as struvite from the residual wastewater.

Tea waste derived activated carbon for the adsorption of sodium diclofenac from wastewater: adsorbent characteristics, adsorption isotherms, kinetics, and thermodynamics.

The present experimental study reports the performance of tea waste (TW) derived adsorbent for the adsorption of sodium diclofenac (SD) from aqueous solution (SD concentration = 10-50 mg/L). The waste-derived activated carbon was prepared by chemical activation process of raw waste using H2SO4, KOH, ZnCl2, and K2CO3 as activating agents (TW: activating agent = 1:1 by weight). Subsequently, the oven-dried material was carbonized at 600-°C temperature for 2 h. The synthesized adsorbents were porous and their Brunauer-Emmett-Teller (BET) surface area was ranged 115-865 m2/g. Among all synthesized adsorbents, the adsorbent activated by ZnCl2 exhibited the highest adsorption capacity (= 62 mg/g), though it was much lower compared to 91 mg/g obtained with commercial activated carbon (CAC) (SD concentration = 30 mg/L, adsorbent dose = 300 mg/L and initial wastewater pH = 6.47). SD equilibrium data could be described by Langmuir isotherm adequately, while pseudo-second-order rate model showed better fit to the time based adsorption data. Low activation energy of the adsorption process suggests the reaction to be temperature independent. Thermodynamic parameters showed the spontaneous and endothermic nature of adsorption process conducted in the presence of waste derived adsorbent.