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The application of persulfate (PS) for the remediation of petroleum hydrocarbon contamination is among the most widely employed in situ chemical oxidation (ISCO) techniques, and it has received widespread attention due to its limited impact on soil integrity. This study employed a FeSO4-activated PS oxidation method to investigate the feasibility of remediating soil contaminated with total petroleum hydrocarbons (TPHs). The factors tested included the TPH concentration, different PS:FeSO4 ratios, the reaction time for remediation, soil physical and chemical property changes before and after remediation, and the effect of soil before and after remediation on soybean growth. The TPH degradation rate in soil was highest for high-, medium-, and low-TPHs soils—81.5%, 81.4%, and 72.9%, respectively, with minimal disruption to the soil's physicochemical properties—when PS:FeSO4 = 1:1. The remediation verification results indicated that the condition of the soybeans was optimal when PS:FeSO4 = 1:1. Under this condition, the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate all remained high. Therefore, the best remediation effect was achieved with PS:FeSO4 = 1:1, which also minimized the damage to the soil and the effects on crop growth. [ABSTRACT FROM AUTHOR]

Coupling chemical oxidation and biodegradation to remediate polycyclic aromatic hydrocarbon (PAH)-contaminated sediment has recently gained significant attention. In this study, calcium peroxide nanoparticles (nCaO2) were utilized as an innovative oxygen-releasing compound for in-situ chemical oxidation. The study investigates the bioremediation of phenanthrene (PHE)-contaminated sediment inoculated with Sphingomonas sp. DSM 7526 bacteria and treated with either aeration or nCaO2. Using three different culture media, the biodegradation efficiencies of PHE-contaminated anoxic sediment, aerobic sediment, and sediment treated with 0.2% w/w nCaO2 ranged from 57.45% to 63.52%, 69.87% to 71.00%, and 92.80% to 94.67%, respectively. These values were significantly higher compared to those observed in non-inoculated sediments. Additionally, the type of culture medium had a prominent effect on the amount of PHE removal. The presence of minerals in the culture medium increased the percentage of PHE removal compared to distilled water by about 2–10%. On the other hand, although the application of CaO2 nanoparticles negatively impacted the abundance of sediment bacteria, resulting in a 30–42% decrease in colony-forming units after 30 days of treatment, the highest PHE removal was obtained when coupling biodegradation and chemical oxidation. These findings demonstrate the successful application of bioaugmentation and chemical oxidation processes for treating PAH-contaminated sediment. [ABSTRACT FROM AUTHOR]

The use of antioxidants is known to reduce lipid oxidation. This study aimed to assess the interaction of two antioxidant mechanisms, namely, "chain‐breaking" and "termination‐enhancing" by combining natural antioxidants derived from "oregano" (Origanum vulgare L.) and "peperina" (Minthostachys mollis K.) essential oils (EOs) in an accelerated oxidation process of sunflower oil at 60°C. Concentrations of 0.05% w/w (1) and 0.02% w/w (2) of the combined oregano and peperina EOs were evaluated. Chemical and volatile oxidation markers were determined in comparison with the pure compounds, an antioxidant‐free control, and a BHT‐treated sample (0.02% w/w). Although the combinations exhibited lower oxidation indicator values (Anisidine ≈ 136) compared to the control (Anisidine ≈ 213), no evidence of a synergistic effect was observed (Anisidine: Oregano 1 ≈ 52; Oregano 2 ≈ 199; Peperina 1 ≈ 155; Peperina 2 ≈ 153), indicating that the combination did not enhance their antioxidant activity beyond that of the pure EOs. Thus, evaluating these combinations in other food matrices is important. Practical Application: Food oxidation is one of the main causes of food spoilage, and the search for natural antioxidants has become a necessity for society's increasing food knowledge and consumption preference. The research is focused on demonstrating that not only natural phenolic compounds with a "chain‐breaking" mechanism have efficient antioxidant activity but also non‐phenolic terpenes using the "termination enhancer" mechanism are efficient, but also the combination of them, which provides more alternative antioxidants for industrial applications. [ABSTRACT FROM AUTHOR]

The study delved into the rate of browning (A420 nm) within a model wine solution, aiming to elucidate mechanisms impacting real product scenarios, including low‐ and no‐alcohol wines. The model wine solutions were prepared by adding tartaric acid, caffeic acid, and catechin into an aqueous ethanol solution containing transition metals (iron [Fe] and copper [Cu]) along with sulfur dioxide (SO2). The results indicated that the model wines without ethanol exhibited the highest browning rates both in the presence (k = 0.0022 day−1) and absence (k = 0.0035 day−1) of SO2. Notably, ethanol concentration showed a negative correlation with kinetic rates in both scenarios: with SO2 (r = −0.9317) and without SO2 (r = −0.9667). The addition of Fe and Cu separately led to a slight elevation in browning, particularly evident with Fe, while adding only Cu exhibited nonsignificant impact. However, their combined addition revealed a marked synergistic effect, rendering the rate notably sensitive to Cu concentration. [ABSTRACT FROM AUTHOR]

Silver nanoparticles modified copper oxide nanocomposite thin films (Ag‐CuO NC TFs) and pristine CuO TF were successfully synthesized on copper substrates using a chemical oxidation route. X‐ray diffractometry (XRD) characterization of Ag‐CuO NC TFs revealed the formation of monoclinic crystal structured CuO. Scanning electron microscopy (SEM) images showed a star‐like grain morphology of the Ag‐CuO NC TFs. Energy dispersive X‐ray spectroscopy (EDX) analysis ascertained the presence of anticipated elements without impurities. Fourier transform infrared spectroscopy (FTIR) investigation confirmed the presence of Ag NPs on CuO in the Ag‐CuO NC TFs. Raman spectroscopy examination indicated the presence of a spinel structure with vibrational and tetrahedral sites. UV‐Vis‐NIR reflectance analysis demonstrated that Ag‐CuO NC TFs with 2.0 wt.% Ag NPs exhibited solar absorptance of 72.39 %, thermal emittance of 4.3 %, and a highest solar selectivity of 16.83 among the prepared thin films. These results suggest that the Ag‐CuO NC TFs could be promising candidates for use as solar selective absorbers in solar thermal energy conversion devices. [ABSTRACT FROM AUTHOR]

The study intended to devise a sustainable treatment scheme for acrylic fiber dyeing process effluents, which significantly differ from other textile plant wastewaters. The necessary experimental support was generated from a set of tests conducted on the wastewater of a plant operation, focused solely on acrylic fiber dyeing. Related experiments involved effluent characterization, biological treatability, and chemical settling/oxidation performed on raw and bio‐treated effluent, as pre‐treatment and/or polishing steps. A total COD level of 910 mg/L with a 70% soluble ratio, low total N and P contents below 10 mg/L, a detergent content of 50 mg/L and a dark/black color of 1150 Pt‐Co unit defined the average properties of the raw plant effluent. Experimental support indicated that activated sludge operation at a sludge age level above 25 d, remained insufficient as it could only provide an effluent with a soluble COD level above 150 mg/L, a biomass escape in the range of 40 to 100 mg/L and with an intense dark color. A similar experimental template, including chemical settling, chemical oxidation by NaOCl and combination of the two processes, was tested as pre‐treatment and a polishing step after biological treatment. Pre‐treatment, although with some benefit to remove toxic and inhibitory compounds, proved to be highly costly, due to excessive chemical usage and sludge generation for a sustainable, cost‐effective approach. The sequence of chemical oxidation and settling steps implemented as a polishing stage was quite effective as it secured complete color removal, a major source of concern for the selected wastewater and also, it reduced COD down to 60 mg/L, a level significantly below the residual COD threshold for biological treatment. This approach, although case‐specific for this study, provided a scientific and general perspective for similar work. [ABSTRACT FROM AUTHOR]

Seafood processing wastewater contains many organic pollutants and nutrients that harm the environment if discharged without treatment. It is urgent to search for a solution to treat seafood processing wastewater for sustainable development purposes. This study aims to examine the different physico-chemical techniques used in seafood processing wastewater treatment, focusing on their ability to reduce pollutants with the aim of carbon neutrality. This study compares the effectiveness of coagulation-flocculation using Polyaluminium Chloride (PAC)/Anionic Polyacrylamide (APAM), chemical oxidation using Sodium hypochlorite (NaOCl), and adsorption using granular activated carbon (GAC). The results show that coagulation-flocculation with a PAC concentration of 125 mg/L after 30 minutes achieved a removal efficiency of 73.0 % for total suspended solids (TSS), 14.6 % for total dissolved solids (TDS), 65.0 % for chemical oxygen demand (COD), 50.0 % color, 10.0 % total nitrogen (TN), 1.0 % ammonium (NH4+), and 10.0 % total phosphorus (TP). The addition of 62.5 mg/L APAM increased the removal efficiencies to 75.0 % TSS, 15.0 % TDS, 68.0 % COD, 50.3 % color, 10.1 % TN, 1.01 % NH4+, and 10.5 % TP. pH 6.5 was ideal for the pollutant removal efficiencies in seafood processing wastewater using coagulation/flocculation. On the other hand, when using 500 mg/L of NaOCl in chemical oxidation for 15 minutes, it resulted in much lower pollutant removal efficiencies of 11.0 % TSS, 26.0 % COD, 50.0 % color, 6.80 % TN, 35.0 % NH4+, while the TDS removal efficiency was not significant. Finally, using 20 g/L of GAC after 60 minutes recorded removal efficiencies of 75.0 % TSS, 18.0 % TDS, 56.8 % COD, 55.0 % color, 11.9 % TN, 20 % NH4+, and 12.1 % TP. It was found that coagulation-flocculation was the most effective treatment method for seafood processing wastewater treatment when considering both the removal efficiency and cost benefit, at about 0.21 €/m3. These findings will help to develop efficient physico-chemical treatments for seafood processing wastewater with the aim of carbon neutrality.

Nutrient resources contained in human urine have great potential to alleviate global agricultural fertilizer demand. Microbial nitrification is a recognized strategy for stabilizing urine ammonia into ammonium nitrate, a common fertilizer worldwide, but faces a core bottleneck of process instability due to microbial inhibition. This study reports a new approach by developing a hybrid oxidation process involving three stages—microbial ammonia oxidation, chemical nitrite oxidation and microbial nitrite oxidation. Candidatus Nitrosoglobus, a γ-proteobacterial ammonia oxidizer highly tolerant to free nitrous acid, was introduced in the first stage to oxidize half of the total ammonia in the influent (8 g NH4+-N/L) to nitrite. The nitrite was then chemically oxidized by using hydrogen peroxide via a rapid chemical reaction to form nitrate. The third stage, microbial nitrite oxidation, was employed to ensure the complete removal of residual nitrite following chemical oxidation. The overall concept demonstrated in this work showcased the robust performance of the hybrid system. Moreover, the system also had a dual advantage in achieving antimicrobial ability in the first and second stages, making treated urine a safe fertilizer.

Titanium dioxide nanoparticles (TiO2 NPs) have traditionally been utilized as industrial catalysts, finding widespread application in various chemical processes due to their exceptional stability and minimal toxicity. However, quantitatively assessing the reactive sites on TiO2 NPs remains a challenge. In this study, we employed a fluorogenic reaction to probe the apparent reactivity of TiO2 NPs. By manipulating the number of defect sites through control of hydrolysis speed and annealing temperature, we determined that the Ti(III) content is positively correlated with the reactivity of TiO2 NPs. Additionally, these Ti(III) sites could be introduced by reducing commercial TiO2 NPs using NaBH4. Our findings suggest that fluorogenic oxidation of Amplex Red is an effective method for probing defect site densities on TiO2 NPs. Utilizing single‐molecule fluorescence imaging, we demonstrated the ability to map defect site density within TiO2 nanowires. Achieving sub‐nanoparticle spatial resolution, we observed significant intraparticle and interparticle variations in the defect site distribution, leading to substantial reactivity heterogeneity. [ABSTRACT FROM AUTHOR]

In-situ chemical oxidation (ISCO) has been widely utilized for the remediation of organic contaminated soil, while the long-term remediation efficiency and mechanism have been rarely explored, which is of great importance to the field implementation due to the potential for secondary pollution in later stages after remediation. The geotechnical centrifuge has proven to be a reliable tool for simulating long-term geoenvironmental issues. Nevertheless, its application in oxidative remediation has been hindered by the lack of suitable apparatus and scaling principles. For this purpose, a series of centrifuge model tests are comprehensively designed and performed in this study. A comprehensive analysis was carried out to evaluate the long-term effectiveness of the site remediation. The investigation focused on analyzing the transport mechanisms of contaminants and secondary contaminants at various time scales (7 and 10 years) and spatial scales. The results of the modeling of model tests indicate that simulating chemical oxidation processes in the centrifuge is feasible with a Damoner number above 100. The model effectively represents the target contaminant (diesel) removal rate and the remaining diesel concentration at 10 years was significantly lower and more uniform than that at 7 years, with a removal rate of approximately 64%. The variation in the secondary pollutants (SO42−) was more complicated, as its generation and migration are influenced by multiple processes and pH values. The diesel concentrations meet permitted values at 7 and 10 years while further remediation is needed for residual SO42−. The remediation process lowers soil pH by 2, shifting it from neutral to acidic. The centrifuge model offers substantial data support for the evaluation of long-term remediation effectiveness at contaminated sites. [ABSTRACT FROM AUTHOR]

Arsenopyrite (FeAsS) stands as one of the primary host minerals for refractory gold, where the gold is finely disseminated or chemically locked up within the matrix of these raw materials. Therefore, oxidation of this sulfide mineral is necessary for the liberation of gold (Au), and then improving its extraction. This paper aims to study the chemical oxidation of arsenopyrite by four oxidizing agents: S2O82-, H2O2, ClO4- and Cr2O72-. The objective was to enhance the oxidation efficiency of arsenopyrite through examining the impact of pH, acid type, and reaction time. The findings showed that S2O82- is the most effective oxidant for arsenopyrite, and the oxidation efficiency varies in the following order: S2O82- > H2O2 > ClO4- > Cr2O72-. The optimum pH for all the studied oxidizing agent was pH=2. The effect of acid type experiments revealed that, for each oxidant, HClO4 was the optimum acid to be used in regulating pH, and the effect of acid type varies in the following order: HClO4 > HNO3 > HCl > H2SO4. The highest oxidation rate recorded in this study was in the case of S2O82- oxidizing agent with pH regulated by HClO4, for which the oxidation efficiency achieved 81.90 % for As oxidation, and 63.94 % for Fe oxidation. This study will help to develop an oxidative pretreatment processes for refractory arsenopyritic gold ores. [ABSTRACT FROM AUTHOR]

Microbial degradation is an important process for removing many organic chemicals from natural waters. The estimation of biodegradability of chemicals which reach the aquatic environment is necessary in assessing the hazard associated with their use. Phenol has many industrial applications and it finds its way into wastewater streams. It is toxic to several biochemical reactions. However, biological transformation of phenol to non-toxic entities is possible. In this article, the data of biodegradation of phenol at different concentrations were studied. For phenol concentrations equal to or less than 147 mg/L, the plateau (the stage associated with the termination of carbon) BOD (biochemical oxygen demand) was calculated to be 169.47% of the corresponding initial phenol concentration, the BOD of the biomass produced up to the plateau was calculated to be 70% of the corresponding initial phenol concentration. This study shows that the biomass produced up to the plateau, the plateau BOD, and the ultimate BOD can all be estimated for phenol concentrations less than 147 mg/L just if the initial phenol concentration is known and without having to repeat the time-consuming BOD experiments. [ABSTRACT FROM AUTHOR]

Investigating soil and water contamination is essential for assessing environmental risks and monitoring remediation processes. This study, located in São Paulo, Brazil, highlights the presence of chlorinated solvents, especially tetrachloroethylene, with the application of remediation measures such as chemical oxidation. Both contamination and remediation processes have led to changes in geophysical signatures, enabling the use of electrical resistivity, despite challenges in urban areas due to consolidated infrastructure. The objective is to integrate data from direct methods and surveys of electrical resistivity and induced polarization, obtained through direct current and resistive capacitive methods, to refine the conceptual model of the area, delineating the influence zone of the contaminant and remediation processes. The resistive capacitive method allows continuous data acquisition in large areas without the need for electrode insertion into the soil. Geoelectrical data, correlated with soil sample descriptions, allow analysis of subsurface characteristics and areas affected by contamination. Variations in resistivity identify differences between lithologies, while induced polarization highlights clayey areas. Chemical oxidation to remediate PCE contamination increases conductivity, allowing for delineation of the remediation's influence zone. Despite urban challenges, the electrical resistivity method helps fill data gaps and improve the conceptual model of the area, demonstrating a rapid and effective approach. [ABSTRACT FROM AUTHOR]

In this study, a microcosm experiment was conducted to investigate the effects of Na2S2O8 preoxidation combined with biostimulation on petroleum-contaminated soil remediation. The response of microbial community during this process was explored using BIOLOG ECO microplate carbon utilization method and 16 s rDNA high-throughput sequencing. The results showed that use of 10 mg/g Na2S2O8 removed 19.8 % of the petroleum hydrocarbons, reduced soil biotoxicity and did not affect soil microbial activity compared to other concentrations. Therefore, sodium persulfate of ca. 10 mg/g was used to oxidize petroleum in soil before the biostimulation experiment with organic and inorganic fertilizers. Our finding showed that the content of total petroleum hydrocarbons (TPHs) in soil was reduced by 43.3 % in inorganic fertilizer treatment after 60 days. The results of BIOLOG ECO microplate carbon utilization analysis and 16 S rDNA high-throughput sequencing further confirmed that biostimulation quickly restored the microbial activities in oxidant treated soil. The main marker bacteria in chemical oxidation combined with biostimulation remediation were Arthrobacter and Paenarthrobacter, and their relative abundances were both significantly negatively correlated with the content of petroleum hydrocarbons in soil.

Abstract This study investigated the use of heat-activated persulfate (HAP) as a chemical oxidation technique for removing tinidazole (TNZ) antibiotic from aqueous solutions. The impact of various operating parameters, including TNZ initial concentration (20 μM), persulfate (PS) initial dose (0.2–2 mM), solution pH (3–11), solution temperature (20–60 °C), and reaction time (10–120 min), was examined. The results indicated that sulfate radicals were the primary species responsible for TNZ degradation. Higher temperatures and PS concentrations improved the process, while higher pH values and TNZ initial concentrations slowed it down. Additionally, chloride and bicarbonate ions reduced reaction rates, with chloride ions having a more significant effect. Under optimal conditions (including [TNZ]0 = 20 μM, pH = 7, [PS]0 = 1 mM, temperature = 60 °C, and reaction time = 120 min), the removal efficiency achieved was 91.15%, with a mineralization rate of 85.8%. These results suggest that the process is relatively safe. The degradation of TNZ was best described by the pseudo-first-order model compared to other models. Additionally, the process was found to be exothermic and spontaneous, with a negative Gibbs free energy change indicating that it is thermodynamically feasible. The study found HAP to be an effective and cost-efficient technique for removing TNZ antibiotic due to its ease of operation and the absence of the need for additional chemicals or waste handling. Based on these findings, HAP can be considered an advanced oxidation technique for treating antibiotic-contaminated water.

Red ginseng extract is one of the most widely used herbal medicines to prevent and cure various diseases. Among the processed products derived from red ginseng, the water-insoluble part as red ginseng residual (RGR) becomes waste, even though it contains important ingredients. TEMPO-oxidation (TO) can be used as a pre-treatment with different degrees of oxidation (DO) (0 to 0.4) in red ginseng residual (RGR-TO) by introducing chemical oxidation and high-pressure homogenizer (HPH) as a nanofibrillation process. 1H NMR was used to determine the carbohydrate composition and calculate DO, size was examined using a nanoparticle analyzer, and the zeta potential was used to determine surface charge density. RGR-TO with different concentrations had different compositions; glucose and uronic acid were the main ingredients. All treated RGR-TO showed higher oxidant levels than the untreated counterpart (RGR-TO 0). As the oxidant levels increased, the zeta potential and uronic acid increased, but the size of the nanofibril from RGR-TO decreased. The results of this study showed that TEMPO-oxidation pretreatment was effective in producing RGR cellulose nanofibril (CNF) with a variety of properties by adjusting the level of oxidation pretreatment and the number of HPH passes. [ABSTRACT FROM AUTHOR]

This manuscript proposes a method for effective discharging method of pulsed energy in industrial effluents. The proposed approach is based on the dielectric barrier discharge (DBD) and Electro hydraulic Plasma Discharge (EHPD). The objective function of the proposed approach is minimizing the concentration of the ethylene blue (MB) dye in the industrial waste water. Using DBD and EHPD technique, treating such industrial effluents before mixing to the running water can effectively prevent polluting the water bodies and human health. It is one of the tertiary waste water treatments, which can also degrade biological substances. DBD technique is one of the advanced oxidation technique to de-color MB dye and the EHPD reactor is a strong and extremely efficient method for the degradation of MB. By then, the proposed model is implemented in the MATLAB platform and the implementation is calculated with the present procedure. The study concludes that the DBD and EHPD method outperforms other methods in terms of degradation efficiency. De-colorization of methylene blue (MB) took just 15 s using a 3 KV, 50μs pulse. • Hybrid method using optimal power quality enhancement. • Honey Badger Algorithm (HBA). • Golden Jackal optimization (GJO). • Electro hydraulic Plasma Discharge (EHPD). [ABSTRACT FROM AUTHOR]

This study investigated the use of heat-activated persulfate (HAP) as a chemical oxidation technique for removing tinidazole (TNZ) antibiotic from aqueous solutions. The impact of various operating parameters, including TNZ initial concentration (20 μM), persulfate (PS) initial dose (0.2–2 mM), solution pH (3–11), solution temperature (20–60 °C), and reaction time (10–120 min), was examined. The results indicated that sulfate radicals were the primary species responsible for TNZ degradation. Higher temperatures and PS concentrations improved the process, while higher pH values and TNZ initial concentrations slowed it down. Additionally, chloride and bicarbonate ions reduced reaction rates, with chloride ions having a more significant effect. Under optimal conditions (including [TNZ]0 = 20 μM, pH = 7, [PS]0 = 1 mM, temperature = 60 °C, and reaction time = 120 min), the removal efficiency achieved was 91.15%, with a mineralization rate of 85.8%. These results suggest that the process is relatively safe. The degradation of TNZ was best described by the pseudo-first-order model compared to other models. Additionally, the process was found to be exothermic and spontaneous, with a negative Gibbs free energy change indicating that it is thermodynamically feasible. The study found HAP to be an effective and cost-efficient technique for removing TNZ antibiotic due to its ease of operation and the absence of the need for additional chemicals or waste handling. Based on these findings, HAP can be considered an advanced oxidation technique for treating antibiotic-contaminated water. [ABSTRACT FROM AUTHOR]

This study investigates the degradation kinetics of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil using hydrogen peroxide (H2O2) and the Fenton process (H2O2/Fe2+). The effect of oxidant concentration and the Fenton molar ratio on PAH decomposition efficiency is examined. Results reveal that increasing H2O2 concentration above 25 mmol/samples leads to a slight increase in the rate constants for both first- and second-order reactions. The Fenton process demonstrates higher efficiency in PAH degradation compared to H2O2 alone, achieving decomposition yields ranging from 84.7% to 99.9%. pH evolution during the oxidation process influences PAH degradation, with alkaline conditions favoring lower elimination rates. Fourier-transform infrared (FTIR) spectroscopy analysis indicates significant elimination of PAHs after treatment, with both oxidants showing comparable efficacy in complete hydrocarbon degradation. The mechanisms of PAH degradation by H2O2 and the Fenton process involve hydroxyl radical formation, with the latter exhibiting greater efficiency due to Fe2+ catalysis. Gaussian process regression (GPR) modeling accurately predicts reduced concentration, with optimized ARD-Exponential kernel function demonstrating superior performance. The Improved Grey Wolf Optimizer algorithm facilitates optimization of reaction conditions, yielding a high degree of agreement between experimental and predicted values. A MATLAB 2022b interface is developed for efficient optimization and prediction of C/C0, a critical parameter in PAH degradation studies. This integrated approach offers insights into optimizing the efficiency of oxidant-based PAH remediation techniques, with potential applications in contaminated soil remediation. [ABSTRACT FROM AUTHOR]

Recent innovative research efforts on the usage of plastic wastes as a cheap carbon source for carbon nanotubes (CNTs) production have emerged as a low-cost and sustainable means of producing CNTs. However, plastic waste-derived CNTs are rarely used in some purity-sensitive and high-alignment needed applications due to the poor quality of CNTs resulting from the abundance of impurities such as non-crystalline amorphous carbon, metallic nanoparticles, and other impurities. Therefore, purification is a crucial issue to be addressed to fully harness all potential applications of CNTs derived from waste plastic materials. Here, the effect of employing different purification methods on the morphology and purity of waste plastic-derived CNTs was investigated. CNTs were synthesized using waste polypropylene plastic as carbon feedstock via a single-stage catalytic chemical vapour deposition (CVD) technique. As-produced CNTs were purified using liquid-phase oxidation (chemical oxidation in nitric acid), gas-phase oxidation in air, and a combination of both liquid- and gas-phase oxidation methods. The synthesized and purified CNTs were characterized for morphology, purity, surface functional groups, thermal stability, and crystallinity using Transmission electron microscopy (TEM), Raman spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and X-ray diffraction (XRD), respectively. Results obtained showed that a combination of both liquid and gas phase oxidation purification techniques resulted in purer, better quality, and less defective CNTs with an IG’/IG value of 0.89 and ID/IG value of 0.86, while chemically treated CNTs (CNT-PC) presented more structurally defective CNTs and shortened nanotubes compared to other investigated treatment methods with an ID/IG value of 0.96. CNTs purified by a multi-step protocol (CNT-PAC) showed the highest weight loss of 72.3% indicating the highest quality and the presence of filamentous carbon. This study confirms that the choice of purification techniques influences the morphology and quality of plastic-derived CNTs. [ABSTRACT FROM AUTHOR]

Naphthalene (NAP) was chosen as a target contaminant due to its increasing environmental concern in this work. Using hydrogen peroxide (H2O2), nano-calcium peroxide (nCP), peroxydisulfate (PDS), and peroxymonosulfate (PMS) as oxidants activated by Fe(II)-citric acid (CA) in aqueous solution, 92.8, 95.0, 97.5, and 99.9% of NAP were removed, respectively, in which CA could significantly enhance NAP degradation. HO• was demonstrated to be the major radical responsible for NAP removal in H2O2/Fe(II)/CA and nCP/Fe(II)/CA processes; both HO• and SO4•− were major radicals in PDS/Fe(II)/CA process, whereas SO4•− was the sole dominant radical in PMS/Fe(II)/CA process. The impacts of water matrices (anions, natural organic matters, and surfactants) and initial solution pH on NAP removal as well as the practicalities of these four systems in groundwater were explored. The efficient NAP degradation of nCP/Fe(II)/CA and PMS/Fe(II)/CA processes in the actual groundwater indicated that these two systems have great potential and advantages in the remediation of NAP-contaminated groundwater. HIGHLIGHTS Citric acid (CA) significantly enhanced naphthalene (NAP) degradation in peroxide/Fe(II)/CA systems.; Mechanisms of NAP degradation in various peroxide/Fe(II)/CA systems were revealed.; NAP degradation performance in complex solution matrixes was investigated.; Excellent reactivity for NAP degradation in actual groundwater was achieved.;

Efficient trivalent actinides/lanthanides(Am3+/Ln3+) separation is one of the key components of advanced nuclear fuel cycle. Owing to their similar chemical behavior in condensed phase, it remains a challenge to adopt traditional liquid-liquid extraction techniques. The strategy of separating Am by oxidizing Am(Ⅲ) to its penta- and hexa-valent states has the benefit of high efficiency and large space of improvement and is attracting growing attention. The obstacle to adopt this strategy is the high oxidation potential, which impedes the efficient conversion of Am(Ⅲ) to Am(Ⅴ,Ⅵ) under mild conditions, and the low stability of high oxidation states of Am. This poses two questions to solve: (1) how to minimize the oxidation potential of Am? (2) how to stabilize Am in its high oxidation state? In this work, we surveyed the advances in the chemical and electrochemical oxidation of Am towards its separation from lanthanides. In its chemical oxidation, copper(Ⅲ) periodate was identified as a superior oxidants over bismuthate and persulfate in view of its high oxidizing power and high yield of Am(Ⅴ,Ⅵ). In its electrochemical oxidation, functionalization of electrode by appropriate ligands can significantly decrease the oxidation potential of Am and increase the overpotential of water, which circumvents the side reactions, e.g. oxidation of water. These results provide insights for the design and optimization of novel protocols for Am/Ln separation, and calls for improved understanding of the underlying mechanisms to stimulate extensive advances of efficient Am/Ln separation.

Two new pentagon‐embedded carbo[11]helicenes have been designed and synthesized in a three‐step process, which are the first example of carbo[11]helicenes through the post‐functionalization of twistacene. TD‐DFT analyses indicate that both of them possess high enantiomerization barriers of 42.29 kcal/mol and 40.76 kcal/mol, respectively. They emit strong red fluorescence and can be chemically oxidized into stable cationic radicals upon addition of AgSbF6 evidenced by the bathochromic‐shifted absorption spectra and the appearance of electronic paramagnetic resonance (EPR) signals. In addition, such helical derivatives can be chosen as radiative cooling materials in a glass model house, and the maxima of 5.4 °C for the former and 6.5 °C for the latter are found in the comparative tests, which might be caused by the NIR reflective response. [ABSTRACT FROM AUTHOR]

Slow-releasing tablets combined with persulfate acting as an oxidant and ferrous iron acting as an activator were manufactured for in situ chemical oxidation. The trichloroethylene (TCE) removal efficiency according to the molar ratio of the oxidizer and activator in the 0, 0.5, 1, 1.5, 2, and 2.5 molar ratio (persulfate: ferrous iron) reactors were 15%, 89%, 90%, 82%, 71%, and 55%, respectively. In a batch reactor injected with an oxidation-activation combined tablet (OACT) and a liquid oxidizing/activator, the TCE removal efficiencies were 100% and 70%, respectively, showing that the tablet form had a high efficiency in contaminant removal. The evaluation of the dissolution characteristics and TCE removal efficiency of OACT 0.5 (tablet with a 1:0.5 molar ratio of persulfate to activator) and OACT 1.0 (tablet with a 1:1 molar ratio of persulfate to activator) under continuous flow conditions showed that the TCE removal efficiency of the OACT 1.0 column was approximately 1.4 times higher than that of OACT 0.5. The longevities of persulfate and ferrous iron of the OACT 1.0 tablet were 43.2 days and 41.7 days, respectively. Thus, OACT 1.0, which was manufactured effectively, was suitable for in situ slow-release chemical oxidation systems. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate Fenton reaction, permanganate and persulfate oxidation as in-situ remediation technology for the treatment of gasoline-diesel contaminated soil. These oxidants were compared in various soils to study the influence of soil texture and soil organic matter. The different fractions of hydrocarbons, which have been scarcely investigated, were also analyzed and the compounds were clustered into aliphatic and aromatic hydrocarbons. Maximal removal rates were obtained with permanganate (74%), followed by persulfate (60%) and hydrogen peroxide (55%). High levels of clay in the soil (silty clay soil) reduced the efficiency of permanganate and persulfate hydrocarbon oxidation by 18%. On the other hand, 5% soil organic matter decreased the effectiveness of permanganate (18%). The removal rates of hydrocarbons decreased while hydrocarbon size increased, and aromatic hydrocarbons were more oxidized than aliphatic ones. In general, elimination percentages higher than 80% are achieved for chains >C6-C8 and lower than 20% for those in the range >C21-C35. The results observed can be used to increase the efficiency and improve the design of advanced oxidation processes for treating gasoline and diesel contaminated soil. [ABSTRACT FROM AUTHOR]

In this paper, MnO2/CNTs composite materials have been studied and fabricated by hydrothermal-assisted chemical oxidation. Oxidation reactions of KMnO4 with MnSO4 and CNTs to form the composites were carried out at 140°C for 20 h. The obtained materials were morphologically observed by FESEM, analyzed for elemental composition by EDX, phase composition by XRD, and thermogravimetric analysis. Results show that the materials were composite of rod-shaped α-MnO2 crystals, diameter from 20 to 30 nm, about 1 μm long, with scattered CNTs. The electrochemical properties of the materials were studied by cyclic voltammetry (CV) and chronopotentiometry (CP) methods. CNTs have improved electrochemical properties of the materials, the discharge rate increased two times and the specific capacity increased 20% higher compared to α-MnO2 with the same fabricated conditions. The MnO2/CNTs 1% material has the best properties, the specific capacity reaches 113 mAh/g, the electrode can still work well after 100 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

Polyolefin plastics play an important role in both production and life due to the excellent characteristics, such as east processing, low price and outstanding performance. It has become the most widely used plastics at present. The main raw materials of polyolefin plastics are non-renewable resources such as coal and oil. Waste polyolefin plastics are difficult to degrade in the natural environment, and will break into small particles. The micro plastics are transferred into lakes, rivers, oceans and soil, which will cause serious impact and damage to the environment and the health of animals and plants. Therefore, in terms of energy conservation and environmental protection, the recycling of polyolefin plastics is a very important topic. Among the recycling methods of polyolefin plastics, oxidative degradation can effectively degrade macromolecular polyolefin plastics to generate high-value small molecule chemical raw materials, realize the recycling and high-value utilization of polyolefin plastics, and provide a good solution to the existing micro plastic pollution problem in the environment. In this paper, the oxidative degradation of polyolefin plastics is studied, and the research progress related to the oxidative degradation in recent years is summarized. The reaction process, oxidation mechanism and degradation products of three oxidative degradation methods, chemical oxidative degradation, biological oxidative degradation and photooxidative degradation, are analyzed and discussed. Based on the current research situation, the development prospect of the oxidative degradation and recovery of polyolefin plastics in the future is also prospected.

Many studies have successfully built iron-mediated materials to activate or catalyze Fenton-like reactions, with applications in water and wastewater treatment being investigated. However, the developed materials are rarely compared with each other regarding their performance of organic contaminant removal. In this review, the recent advances of Fenton-like processes in homogeneous and heterogeneous ways are summarized, especially the performance and mechanism of activators including ferrous iron, zero valent iron, iron oxides, iron-loaded carbon, zeolite, and metal organic framework materials. Also, this work mainly compares three O-O bond containing oxidants including hydrogen dioxide, persulfate, and percarbonate, which are environmental-friendly oxidants and feasible for in-situ chemical oxidation. The influence of reaction conditions, catalyst properties and benefits are analyzed and compared. In addition, the challenges and strategies of these oxidants in applications and the major mechanisms of the oxidation process have been discussed. This work can help understand the mechanistic insights of variable Fenton-like reactions, the role of emerging iron-based materials, and provide guidance for choosing appropriate technologies when facing real-world water and wastewater applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Sulfate radical-based advanced oxidation processes have been applied in the remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil, during which sulfate can be activated in different ways. In this work, effects of four different ways (FeSO4, NaOH, H2O2, and Heat) activated sodium persulfate (PS) on PAHs removal and soil physicochemical properties (pH, organic matter, functional groups, surface morphology, and partial heavy metal elements) were compared, and the influencing factors and mechanism of soil PAHs removal by thermally activated PS were also studied. The results showed that at the dosage of 3% of persulfate, the removal efficiency of PAHs followed the sequences of Heat (91.4%) > FeSO4 (86.6%) > H2O2 (86.2%) > NaOH (72.9%). However, thermal activation decreased the soil pH and organic matter content more significantly than other treatments. The reaction tended to reach equilibrium at 6 h when the dosage of persulfate was 3% and the activation temperature was 60 °C, and the reaction obeyed pseudo-first-order kinetics. Through quenching experiments, it was found that the free radicals playing a dominant role in the oxidation process were sulfate radicals. Compared with pH, liquid to soil (L/S ratio) and the temperature had more significant impacts on the degradation efficiency of PAHs. [ABSTRACT FROM AUTHOR]

The accumulation of manganese (Mn) in drinking water distribution systems (DWDS) is the main reason for ‘black water’ occurrences at customers' taps. Here, we focused on the impact of hydraulic conditions on Mn accumulation in well chlorinated DWDS, particularly on the physical pathway (i.e., the attachment of particulate Mn to the inner pipe surface) and the chemical pathway (i.e., the autocatalytic oxidation of Mn2+ on the surface of accumulated Mn). Mn accumulation on epoxy resin, a typical lining material for distribution pipes in Japan, was observed in laboratory-scale experiments under different water velocity conditions. The results showed that Mn accumulation was significantly enhanced under higher velocity conditions, which was then fitted with the numerical models describing Mn accumulation by the physical and chemical pathways and the detachment. The rate constants for the physical and chemical pathways had a positive relationship with the flow turbulence in the investigated range, suggesting that hydraulic conditions in DWDS play an important role in Mn accumulation. Effects of Mn speciation and water characteristics on the accumulation process were also simulated under various hydraulic conditions. Based on the obtained results, appropriate countermeasures to control manganese accumulation were then discussed. HIGHLIGHTS Effect of hydraulic condition on Mn accumulation in distribution pipes was studied.; Mn accumulated in pipes via the physical and chemical pathways in chlorinated condition.; The contribution of the chemical pathway of Mn accumulation increased with time.; The rates of both pathways were greatly affected by water velocity.; Increasing the water velocity alone may not be sufficient to reduce Mn accumulation.;

Fabrication of noble metal nanoparticles by using green chemical method with plant extract as reducing agent to the in situ oxidation toxic water contaminants have been the subject of various investigators due to their enhanced catalytic efficiencies. This paper describes the extraction of caffeic acid from Artemisia herba-alba aqueous extract, and preparation of silver (Ag), platinum (Pt), and silver-platinum (Ag-Pt) nanoparticles with caffeic acid as a reducing and capping agent. The as-prepared Ag-Pt NPs was used as a heterogeneous activator of persulphate (K2S2O8) for the in situ chemical oxidation of malachite green (MG). The Ag-Pt NPs shows no surface Plasmon resonance absorption band. The malachite green dye was completely decolorized in presence of Ag-Pt/K2S2O8 system. SO4-• and HO• radicals generated by the cleavage of S2O82- peroxide activation with Ag-Pt were responsible for the MG decolorization as well as mineralization. The Ag-Pt NPs acted as a sacrificial electron donor. The Ag-Pt NPs were characterized by using conventional techniques such as, UV–visible, FTIR, SEM, TEM, EDX, XPS, and XRD spectroscopic methods.

Arsenopyrite (FeAsS) is a typical gold-bearing sulfide mineral. It usually encapsulates the gold particles and seriously inhibits the leaching of gold, so oxidation pretreatment of arsenopyrite is prerequired for the effective leaching of gold. However, the oxidation of arsenopyrite is accompanied by arsenic mobility, potentially resulting in serious environmental issues. An eco-friendly oxidant, δ-MnO2, was herein used to effectively oxidize arsenopyrite and control the fate of arsenic under acidic conditions. Via characterization of the variation of leaching parameters, morphology change, and elemental speciation transformation on the mineral surface, it was found that adding δ-MnO2 significantly provoked the oxidation of Fe(II) and As(−I) to Fe(III) and As(V), and mediated the speciation transformation of Fe/As to FeAsO4. δ-MnO2 dosage remarkably controlled the oxidation efficiency of arsenopyrite and arsenic speciation transformation, efficiently regulating arsenic fate. These results suggest that δ-MnO2 could simultaneously promote the dissolution of arsenopyrite and the immobilization of arsenic, which could have implications for the oxidation pretreatment of refractory gold minerals and the source management of arsenic-contaminated environments. [ABSTRACT FROM AUTHOR]

Various methods for the oxidation of different types of carbon nanotubes (CNTs) in nitric acid and a mixture of nitric and sulfuric acids at various temperatures and durations of exposure are studied. Oxidation conditions that provide the high sorption activity of sorbents with respect to REE are found. Oxidized CNTs are characterized by acid-base titration and scanning electron microscopy, and the electrokinetic (ζ) potential of nanotube suspensions is determined as a function of pH. The elemental composition of CNTs is determined by ICP MS/AES methods. The sorption capacity of the oxidized CNTs with respect to a wide range of elements is determined. Their unique selectivity with respect to REE is revealed. A possibility of using oxidized CNTs for the efficient sorption preconcentration of REE with the aim to determine their ultralow concentrations in rocks is proved. [ABSTRACT FROM AUTHOR]

In this study, the formation and evolution of a corrosion product film on a 304 stainless steel exposed to an HCl pickling solution containing H2O2 were evaluated. Electrochemical polarization, spectroscopy, and characterization techniques including scanning electron microscopy, energy-dispersive x-ray spectroscopy, confocal laser scanning microscopy, and x-ray photoelectron spectroscopy were employed to investigate the characteristics of the corrosion product film and its effect on the corrosion of the stainless steel. The composition and structure of the corrosion product films were governed by the chemical oxidation of H2O2, which was dependent on the H2O2 concentration. The formation of a loosened CrCl3, FeCl2, and FeCl3 salt film occurs in the presence of 0.05-M H2O2. With a higher H2O2 concentration (0.15–0.60 M), the Fenton's reaction creates an environment for the production of chromium oxides and hydroxides. A compact film consisting of Cr(OH)3 and Cr2O3 covers the stainless steel. The dissolution of metal is then governed by the random availability of cation vacancies at the metal/film interface rather than the lattice structure of the metal, which contributes to the anodic brightening of the stainless steel. The compact film can dissolve in the HCl–H2O2 solution and transform into chloride salts again. Once the compact film breaks without self-repair, it causes a local attack at grain boundaries of the stainless steel. [ABSTRACT FROM AUTHOR]

Carbon paper has been synthesized by paper making process followed by composite formation, and further chemically oxidized by immersing into a mixture of sulphuric acid and potassium dichromate to be used as an electrode for supercapacitor applications. XRD and Raman spectra were used to analyze the structure, and the defects in the samples respectively, in due course of oxidation. FESEM images revealed the morphology of oxidized samples to be rougher, which contributes towards increased active sites for reaction. The sample (COCP‐60) optimized via electrochemical studies, was further tested in various electrolytes to study the electrode/electrolyte interaction. It delivered a highest areal capacitance of 6.02 F/cm2 (231.5 F/g) in acidic electrolyte at a current density of 5 mA/cm2 (0.19 A/g). This findings were further corroborated by surface and diffusion contribution studies wherein it was found that diffusion is more profound with acidic electrolyte. The supercapacitor device fabricated with COCP‐60 electrode delivered an energy density of 0.41 Wh/cm2 at 2.83 W/cm2 power density with coulombic efficiency of 98 %, and cyclic stability of ∼90 % for over 5000 cycles. [ABSTRACT FROM AUTHOR]