Environmental remediation of emerging contaminants using subcritical water: A review.

The continuous rise of emerging contaminants (ECs) in the environment has been a growing concern due to their potentially harmful effects on humans, animals, plants, and aquatic life, even at low concentrations. ECs include human and veterinary pharmaceuticals, hormones, personal care products, pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organic dyes, heavy metals (HMs), and others. The world's growing population contributes to the release of many kinds of chemicals into the environment, which is estimated to be more than 200 billion metric tons annually and results in over 9 million deaths. The removal of these contaminants using conventional physical, chemical, and biological treatments has proven to be ineffective, highlighting the need for simple, effective, inexpesive, practical, and eco-friendly alternatives. Thus, this article discusses the utilization of subcritical water oxidation (SBWO) and subcritical water extraction (SBWE) techniques to remove ECS from the environment. Subcritical water (water below the critical temperature of 374.15 °C and critical pressure of 22.1 Mpa) has emerged as one of the most promising methods for remediation of ECs from the environment due to its non-toxic properties, simplicity and efficiency of application. Furthermore, the impact of temperature, pressure, treatment time, and utilization of chelating agents, organic modifiers, and oxidizing agents in the static and dynamic modes was investigated to establish the best conditions for high ECs removal efficiencies.

Solubility and Decomposition of Organic Compounds in Subcritical Water.

In this article, studies on organic solubility and stability in subcritical water reported during the past 25 years have been reviewed. Data on the solubility and decomposition of organic compounds in subcritical water, a green solvent, are needed in environmental remediation, chemistry, chemical engineering, medicine, polymer, food, agriculture, and many other fields. For solubility studies, the experimental systems used to measure solubility, mathematical equations derived and applied for the modeling of the experimentally determined solubility data, and the correlation between the predicated and experimental data have been summarized and discussed. This paper also reviewed organic decomposition under subcritical water conditions. In general, the solubility of organics is significantly enhanced with increasing water temperature. Likewise, the percentage of organic decomposition also increases with higher temperature.

Anticancer potential of Origanum munzurense extract against MCF-7 breast cancer cell.

Origanum munzurense (O. munzurense) is an endemic species of Tunceli region of Turkey. In this study, we investigated in vitro anticancer effect of aqueous extract of O. munzurense (OME) on breast cancer cells (MCF-7). In vitro cytotoxic effect of OME was evaluated in MCF-7 cells by MTT assay. The wound-healing assay was used to examine the inhibition of migration. Annexin V/propidium iodide staining, cell-cycle distribution was assessed by flow cytometry for MCF-7 cells treated with OME. MTT results show that OME demonstrated in vitro cytotoxicity with 600 mg at 48 h on MCF-7. Doses of 400 µg/mL and 600 µg/mL OME significantly suppressed the migration rate of MCF-7 cells. OME significantly decreased the percentage of live cancer cells and showed an apoptotic effect after 48 h of incubation. These results show that OME is effective against breast cancer when administered at high doses and for a long time.

A comparison of the performance of conventional and eco-friendly extraction methods in the evaluation of total phenolics, antioxidant activity, and chemical composition of anise.

In this work, the essential oil of Pimpinella anisum seeds was obtained by six different extraction methods. In the chemical composition analysis, 4, 6, 4, 1, 20, and 8 compounds were detected in the extracts obtained by Soxhlet, Ultrasonic-assisted (UAE), hydrodistillation using Clevenger apparatus (HDC), subcritical water extraction (SWE), supercritical carbon dioxide extraction (ScCO2) using three solvents (methanol (ScCO2-Met), ethanol (ScCO2-Et), and hexane (ScCO2-H)) and supercritical 1,1,1,2-tetrafluoroethane (ScR134a) methods, respectively. Also, the performances of the applied methods were compared by analysing the total phenolic content (TPC) and antioxidant activity of the extracts. Anethole was the main component of all extracts obtained by SWE (94.5%) and Soxhlet (94.5%) methods, respectively. Also, TPC values were the highest (508.5 mg GAE/100 g kb) in ScR134a extract and the lowest (27.77 mg GAE/100 g kb) in HDC extracts. The antioxidant capacity was found to be the highest in ScCO2-H (IC50 = 1.58 mg/mL) and the lowest in Soxhlet extracts (IC50 = 0.07 mg/mL). The results showed the great effectiveness of eco-friendly extraction SWE, ScCO2-Et, and ScR134a methods.

Treatment of agrochemical wastewater by subcritical water oxidation method: chemical composition and ion analysis of treated and untreated samples.

This work aimed at offering an effective and environmentally friendly approach to the real wastewater of an industrial agrochemicals production plant containing high amounts of many hazardous compounds that threaten human health. The removal of total organic carbon (TOC) (59.45%) and colour (97.92%) of the wastewater was achieved using subcritical water oxidation method. The fate of the detected compounds was followed by GC-MS analysis. Several pollutants such as phenol, fumaric acid, chlorpyrifos, penconazole, brassilexin, buprofezin, etoxazole, pyriproxyfen and 2-naphthalene-sulphonic acid which are bio-refractory and harmful to human health, were effectively degraded. Inorganic ions exist in the wastewater or formed through the process and their possible effects on the applied method were analysed. The central composite design was used to optimise the method and fully evaluate the single or combined effects of the method parameters on the removal rates. The precision of the applied design models was evaluated employing ANOVA, Regression coefficients and validation analysis. F and P and R2 values were obtained as 107.43, <0.0001, and 0.9898, respectively in the TOC removal model and 39.45, <0.0001, and 0.9726 in the colour removal model.[Formula: see text].

Application of ultrasound-assisted and subcritical water oxidation methods in the mineralisation of Procion Crimson H-EXL using response surface methodology and artificial neural network.

Eco-friendly methods, the ultrasound-assisted oxidation (UAO) and the subcritical water oxidation (SWO) methods, were applied to mineralise the widely used commercial reactive azo dye, Procion Crimson H-EXL in the presence of H2O2. 72.20% and 72.86% of total organic carbon removal were achieved in the UAO and SWO methods, respectively. The Box-Behnken design (BBD) was applied to design the experimental processes and optimise both methods. ANOVA and validation tests were performed to assess the employed models. F and P values were obtained as 36.72 and <0.0001 in the UAO method, respectively, and 605.97 and <0.0001 in the SWO method, respectively. The artificial neural network (ANN) was applied in both the UAO and the SWO methods. The predictive performance of the BBD and ANN models were evaluated and compared to each other over R2, root mean square error and absolute average deviation values.

Degradation of acid red 97 dye in aqueous medium using wet oxidation and electro-Fenton techniques.

Degradation of the acid red 97 dye using wet oxidation, by different oxidants, and electro-Fenton systems was investigated in this study. The oxidation effect of different oxidants such as molecular oxygen, periodate, persulfate, bromate, and hydrogen peroxide in wet oxidation system was compared. Mineralization of AR97 with periodate appeared more effective when compared with that of the other oxidants at equal initial concentration. When 5 mM of periodate was used, at the first minute of the oxidative treatment, the decolorization percentage of AR97 solution at 150 and 200 degrees C reached 88 and 98%, respectively. The total organic carbon removal efficiency at these temperatures also reached 60 and 80%. The degradation of AR97 was also studied by electro-Fenton process. The optimal current value and Fe(2+) concentration were found to be 300 mA and 0.2 mM, respectively. The results showed that electro-Fenton process can lead to 70 and 95% mineralization of the dye solution after 3 and 5h giving carboxylic acids and inorganic ions as final end-products before mineralization. The products obtained from degradation were identified by GC/MS as 1,2-naphthalenediol, 1,1'-biphenyl-4-amino-4-ol, 2-naphthalenol diazonium, 2-naphthalenol, 2,3-dihydroxy-1,4-naphthalenedion, phthalic anhydride, 1,2-benzenedicarboxylic acid, phthaldehyde, 3-hydroxy-1,2-benzenedicarboxylic acid, 4-amino-benzoic acid, and 2-formyl-benzoic acid.

Oxidative degradations of reactive blue 4 dye by different advanced oxidation methods.

The degradations of an anthraquinone dye, the reactive blue 4 (RB4), were studied by wet air oxidation (WAO), wet peroxide oxidation (WPO), photocatalytic oxidation, and electro-Fenton (EF) advanced oxidation. The RB4 oxidation was evaluated by the decrease in total organic carbon (TOC) content and concentration. The most efficient method for mineralization of RB4 was WPO, but in all methods TOC removal efficiency was above 75% after 60 min of treatment.