Pub Date : 2024-09-23eCollection Date: 2024-10-11DOI: 10.1021/acsestengg.4c00317
Kyungho Kim, Cesar Castillo, Gyoung G Jang, Yuxuan Zhang, Costas Tsouris, Shankararaman Chellam
Electrocoagulation has attracted significant attention as an alternative to conventional chemical coagulation because it is capable of removing a wide range of contaminants and has several potential advantages. In contrast to most electrocoagulation research that has been performed with nonporous electrodes, in this study, we demonstrate energy-efficient iron electrocoagulation using porous electrodes. In batch operation, investigation of the external pore structures through optical microscopy suggested that a low porosity electrode with sparse connection between pores may lead to mechanical failure of the pore network during electrolysis, whereas a high porosity electrode is vulnerable to pore clogging. Electrodes with intermediate porosity, instead, only suffered a moderate surface deposition, leading to electrical energy savings of 21% and 36% in terms of electrocoagulant delivery and unit log virus reduction, respectively. Neutron computed tomography revealed the critical role of electrode porosity in utilizing the electrode's internal surface for electrodissolution and effective delivery of electrocoagulant to the bulk. Energy savings of up to 88% in short-term operation were obtained with porous electrodes in a continuous flow-through system. Further investigation on the impact of current density and porosity in long-term operation is desired as well as the capital cost of porous electrodes.
{"title":"Porous Iron Electrodes Reduce Energy Consumption During Electrocoagulation of a Virus Surrogate: Insights into Performance Enhancements Using Three-Dimensional Neutron Computed Tomography.","authors":"Kyungho Kim, Cesar Castillo, Gyoung G Jang, Yuxuan Zhang, Costas Tsouris, Shankararaman Chellam","doi":"10.1021/acsestengg.4c00317","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00317","url":null,"abstract":"<p><p>Electrocoagulation has attracted significant attention as an alternative to conventional chemical coagulation because it is capable of removing a wide range of contaminants and has several potential advantages. In contrast to most electrocoagulation research that has been performed with nonporous electrodes, in this study, we demonstrate energy-efficient iron electrocoagulation using porous electrodes. In batch operation, investigation of the external pore structures through optical microscopy suggested that a low porosity electrode with sparse connection between pores may lead to mechanical failure of the pore network during electrolysis, whereas a high porosity electrode is vulnerable to pore clogging. Electrodes with intermediate porosity, instead, only suffered a moderate surface deposition, leading to electrical energy savings of 21% and 36% in terms of electrocoagulant delivery and unit log virus reduction, respectively. Neutron computed tomography revealed the critical role of electrode porosity in utilizing the electrode's internal surface for electrodissolution and effective delivery of electrocoagulant to the bulk. Energy savings of up to 88% in short-term operation were obtained with porous electrodes in a continuous flow-through system. Further investigation on the impact of current density and porosity in long-term operation is desired as well as the capital cost of porous electrodes.</p>","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"4 10","pages":"2573-2584"},"PeriodicalIF":7.4,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11474953/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142455524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-20DOI: 10.1021/acsestengg.4c00462
Ning Zhang, Ruoxi Yang, Haonan Danny Huang, Jenny Meng, Wencai Zhang, Ah-Hyung Alissa Park, Aaron Moment
This study proposed a sustainable method for the concurrent recovery of metals from olivine minerals and carbon sequestration through carbon mineralization to address the challenges of climate change and critical mineral recovery for the renewable energy transition. It developed a comprehensive development in leaching processes, recovery of metals, and reagent recycling while assessing its economic benefits and environmental impact. Employing hydrometallurgical leaching, our approach facilitates the selective recovery of Ni2+ while converting Mg2+ into their carbonates. This approach is further refined through a stepwise technique that controls operating conditions to generate high-purity valuable products, enabling nearly 90% of Mg2+ and Ni2+ to be dissolved and converted to carbonates. This study evaluated various organic and inorganic acids for the leaching process, followed by Fe extraction and pH swing, to yield pure Fe salts and amorphous silica. Separately extracting iron from the solution significantly reduces the loss of valuable metals in subsequent stages by minimizing the coprecipitation of iron with silicon. A techno-economic assessment (TEA) was performed to evaluate the economic impact of removing iron before the solvent extraction of nickel. This analysis, based on mass balance flow comparisons, determined that the independent removal of iron is more profitable, resulting in the production of more and higher-value products. Ni2+ was selectively extracted from the leachate using Versatic 10, which forms a complex with nickel in the organic phase. The solution containing either a strong acid or a greener agent (i.e., gaseous CO2) was effectively used to strip Ni2+ from the organic phase. Different polymorphs of Mg carbonates were produced under ambient conditions. The proposed process flow results in high-purity products suitable for use in various industries, which enhances the economy, facilitating the rapid adoption of this technology.
{"title":"Integrated Recovery of Iron and Nickel from Olivine Ores Using Solvent Extraction: Synergistic Production of Amorphous Silica and Carbonates through pH Adjustment and Carbon Mineralization","authors":"Ning Zhang, Ruoxi Yang, Haonan Danny Huang, Jenny Meng, Wencai Zhang, Ah-Hyung Alissa Park, Aaron Moment","doi":"10.1021/acsestengg.4c00462","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00462","url":null,"abstract":"This study proposed a sustainable method for the concurrent recovery of metals from olivine minerals and carbon sequestration through carbon mineralization to address the challenges of climate change and critical mineral recovery for the renewable energy transition. It developed a comprehensive development in leaching processes, recovery of metals, and reagent recycling while assessing its economic benefits and environmental impact. Employing hydrometallurgical leaching, our approach facilitates the selective recovery of Ni<sup>2+</sup> while converting Mg<sup>2+</sup> into their carbonates. This approach is further refined through a stepwise technique that controls operating conditions to generate high-purity valuable products, enabling nearly 90% of Mg<sup>2+</sup> and Ni<sup>2+</sup> to be dissolved and converted to carbonates. This study evaluated various organic and inorganic acids for the leaching process, followed by Fe extraction and pH swing, to yield pure Fe salts and amorphous silica. Separately extracting iron from the solution significantly reduces the loss of valuable metals in subsequent stages by minimizing the coprecipitation of iron with silicon. A techno-economic assessment (TEA) was performed to evaluate the economic impact of removing iron before the solvent extraction of nickel. This analysis, based on mass balance flow comparisons, determined that the independent removal of iron is more profitable, resulting in the production of more and higher-value products. Ni<sup>2+</sup> was selectively extracted from the leachate using Versatic 10, which forms a complex with nickel in the organic phase. The solution containing either a strong acid or a greener agent (i.e., gaseous CO<sub>2</sub>) was effectively used to strip Ni<sup>2+</sup> from the organic phase. Different polymorphs of Mg carbonates were produced under ambient conditions. The proposed process flow results in high-purity products suitable for use in various industries, which enhances the economy, facilitating the rapid adoption of this technology.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"16 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142255992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.1021/acsestengg.4c00326
Lu Wang, Guoshuai Liu, Qifang Lu, Hua Zou, Shijie You
Degradation of fluorinated organic pollutants remains a challenge due to the strong electronegativity of fluorine and the high structural stability of C–F bonds. Advanced reduction processes (ARPs) based on strong reducibility of hydrated electrons (eaq–) are effective for destroying recalcitrant fluorinated organic pollutants. Ultraviolet (UV) photolysis is a frequently used method for producing eaq–, but it is limited by the need for chemical addition and light-shielding effects. This study reported the generation of eaq– via electron tunneling based on the n+Si/Al2O3 cathode with a metal–insulator-semiconductor (MIS) structure for the rapid reductive degradation of a halogenated emerging pollutant (florfenicol, FLO). The results demonstrate that the n+Si/Al2O3 cathode achieved 97.5% degradation (30 min), accounting for 92.3% defluorination and 97.0% dechlorination (120 min). The electrogenerated eaq– was responsible for the degradation and dehalogenation of FLO, as indicated by electron spin resonance (ESR) measurements, scavenger experiments, and electrochemiluminescence (ECL) tests. The theoretical calculations revealed the occurrence of electron tunneling on the thin Al2O3 film at the n+Si/Al2O3 cathode, where the tunneling electron jumped to the water to form eaq–. The ARPs based on electrogenerated eaq– also demonstrated efficient degradation of chloramphenicol (CAP), hydroxychloroquine (HCQ), and levofloxacin (LVF). This study not only provides a simple approach to eaq– generation via the electron tunneling effect but also suggests a possible strategy for developing ARPs to remove halogenated emerging organic pollutants in water.
{"title":"Reductive Degradation of Florfenicol by Electrogenerated Hydrated Electrons via the Electron Tunneling Effect","authors":"Lu Wang, Guoshuai Liu, Qifang Lu, Hua Zou, Shijie You","doi":"10.1021/acsestengg.4c00326","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00326","url":null,"abstract":"Degradation of fluorinated organic pollutants remains a challenge due to the strong electronegativity of fluorine and the high structural stability of C–F bonds. Advanced reduction processes (ARPs) based on strong reducibility of hydrated electrons (e<sub>aq</sub><sup>–</sup>) are effective for destroying recalcitrant fluorinated organic pollutants. Ultraviolet (UV) photolysis is a frequently used method for producing e<sub>aq</sub><sup>–</sup>, but it is limited by the need for chemical addition and light-shielding effects. This study reported the generation of e<sub>aq</sub><sup>–</sup> via electron tunneling based on the n<sup>+</sup>Si/Al<sub>2</sub>O<sub>3</sub> cathode with a metal–insulator-semiconductor (MIS) structure for the rapid reductive degradation of a halogenated emerging pollutant (florfenicol, FLO). The results demonstrate that the n<sup>+</sup>Si/Al<sub>2</sub>O<sub>3</sub> cathode achieved 97.5% degradation (30 min), accounting for 92.3% defluorination and 97.0% dechlorination (120 min). The electrogenerated e<sub>aq</sub><sup>–</sup> was responsible for the degradation and dehalogenation of FLO, as indicated by electron spin resonance (ESR) measurements, scavenger experiments, and electrochemiluminescence (ECL) tests. The theoretical calculations revealed the occurrence of electron tunneling on the thin Al<sub>2</sub>O<sub>3</sub> film at the n<sup>+</sup>Si/Al<sub>2</sub>O<sub>3</sub> cathode, where the tunneling electron jumped to the water to form e<sub>aq</sub><sup>–</sup>. The ARPs based on electrogenerated e<sub>aq</sub><sup>–</sup> also demonstrated efficient degradation of chloramphenicol (CAP), hydroxychloroquine (HCQ), and levofloxacin (LVF). This study not only provides a simple approach to e<sub>aq</sub><sup>–</sup> generation via the electron tunneling effect but also suggests a possible strategy for developing ARPs to remove halogenated emerging organic pollutants in water.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"4 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There is an urgent need to develop effective methods for converting nitrous oxide (N2O) into nonharmful N2 because N2O is a potent greenhouse gas, and its increasing concentration in the atmosphere is a major concern for global warming. In this study, we developed a two-step N2O capture and reduction system, employing CaO-incorporated zeolites (Ca-zeolites) as N2O adsorbents and Pd nanoparticles on La-containing Al2O3 (Pd/La/Al2O3) as catalysts for N2O reduction. This process is suitable for continuous operation over a temperature swing of 50–150 °C. The N2O capture capacity and subsequent reduction ability were preserved for at least 15 h (10 cycles). Notably, this system can operate at low temperatures (below 150 °C) using a simple temperature-swing process in the presence of O2.
一氧化二氮（N2O）是一种强效温室气体，其在大气中浓度的增加是全球变暖的一个主要问题，因此迫切需要开发有效的方法，将一氧化二氮（N2O）转化为无害的二氧化氮（N2）。在这项研究中，我们开发了一种两步式氧化亚氮捕获和还原系统，采用 CaO 嵌合沸石（Ca-zeolites）作为氧化亚氮吸附剂，以含 La 的 Al2O3 上的钯纳米颗粒（Pd/La/Al2O3）作为氧化亚氮还原催化剂。该工艺适合在 50-150 °C 的温度范围内连续运行。N2O 捕获能力和随后的还原能力至少保持了 15 小时（10 个循环）。值得注意的是，在有氧气存在的情况下，该系统可通过简单的温度摆动过程在低温（低于 150 °C）下运行。
{"title":"Continuous N2O Capture and Reduction to N2 Using Ca-Zeolite Adsorbent and Pd/La/Al2O3 Reduction Catalyst","authors":"Yuan Jing, Chenxi He, Li Wan, Jiahuan Tong, Jialei Zhang, Shinya Mine, Ningqiang Zhang, Yuuta Kageyama, Hironori Inomata, Ken-ichi Shimizu, Takashi Toyao","doi":"10.1021/acsestengg.4c00560","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00560","url":null,"abstract":"There is an urgent need to develop effective methods for converting nitrous oxide (N<sub>2</sub>O) into nonharmful N<sub>2</sub> because N<sub>2</sub>O is a potent greenhouse gas, and its increasing concentration in the atmosphere is a major concern for global warming. In this study, we developed a two-step N<sub>2</sub>O capture and reduction system, employing CaO-incorporated zeolites (Ca-zeolites) as N<sub>2</sub>O adsorbents and Pd nanoparticles on La-containing Al<sub>2</sub>O<sub>3</sub> (Pd/La/Al<sub>2</sub>O<sub>3</sub>) as catalysts for N<sub>2</sub>O reduction. This process is suitable for continuous operation over a temperature swing of 50–150 °C. The N<sub>2</sub>O capture capacity and subsequent reduction ability were preserved for at least 15 h (10 cycles). Notably, this system can operate at low temperatures (below 150 °C) using a simple temperature-swing process in the presence of O<sub>2</sub>.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"202 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effective removal of soluble Fe(II) and Mn(II) is problematic in water supply utilities. This study explored the oxidation behavior, kinetics, and reaction mechanisms of using peroxymonosulfate (PMS) to mediate the co-oxidation of Fe(II) and Mn(II) in natural water. At [Fe(II)] and [Mn(II)] of 1 mg/L, PMS oxidized all Fe(II) spontaneously within 15 s, irrespective of the oxidant concentration (50–500 μM) and solution pH (6–9), while it required 7–30 min for complete Mn(II) oxidation, indicating its distinctive behavior in reacting with Fe(II) and Mn(II). Scavenging assays and electron paramagnetic resonance (EPR) analysis revealed the dominant presence of O2•– in the system. EPR analysis combined with chemical probing experiments using nitroblue tetrazolium chloride suggested that O2•– was produced exclusively via surface reactions of ferric oxide with PMS. PMS co-oxidation eventually yielded amorphous hydrous manganese-bearing ferric co-oxides (hMnFeOx), with increasing Mn:Fe compositional ratios over time and pH, i.e., Mn0.31Fe0.69, Mn0.67Fe0.33, Mn0.93Fe0.07 at pH 7 and Mn0.68Fe0.32, Mn0.89Fe0.11, Mn0.90Fe0.10 at pH 9. The co-occurrence of Fe(II) provided hydrous FeOx surfaces enriched with chemisorbed oxygen (∼60%), acting as nucleation sites for the heterogeneous MnOx oxidation through enhanced electron transfer and surface complexation pathways. This co-occurrence thus reduced the half-life time of PMS-induced Mn(II) oxidation, by 5.3–18.7 times compared to the Mn(II) oxidation alone. This study provides fresh evidence, underscoring the significance of O2•– in PMS-mediated metal oxidation systems.
{"title":"Iron Enhancing Superoxide-Mediated Mn(II) Oxidation by Peroxymonosulfate: Elucidating the Role of Superoxide Radicals","authors":"Lap-Cuong Hua, Chia-Yu Weng, Yi-Hsueh Brad Chuang, Maria Kennedy, Chihpin Huang","doi":"10.1021/acsestengg.4c00333","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00333","url":null,"abstract":"The effective removal of soluble Fe(II) and Mn(II) is problematic in water supply utilities. This study explored the oxidation behavior, kinetics, and reaction mechanisms of using peroxymonosulfate (PMS) to mediate the co-oxidation of Fe(II) and Mn(II) in natural water. At [Fe(II)] and [Mn(II)] of 1 mg/L, PMS oxidized all Fe(II) spontaneously within 15 s, irrespective of the oxidant concentration (50–500 μM) and solution pH (6–9), while it required 7–30 min for complete Mn(II) oxidation, indicating its distinctive behavior in reacting with Fe(II) and Mn(II). Scavenging assays and electron paramagnetic resonance (EPR) analysis revealed the dominant presence of O<sub>2</sub><sup>•–</sup> in the system. EPR analysis combined with chemical probing experiments using nitroblue tetrazolium chloride suggested that O<sub>2</sub><sup>•–</sup> was produced exclusively via surface reactions of ferric oxide with PMS. PMS co-oxidation eventually yielded amorphous hydrous manganese-bearing ferric co-oxides (hMnFeO<sub><i>x</i></sub>), with increasing Mn:Fe compositional ratios over time and pH, i.e., Mn<sub>0.31</sub>Fe<sub>0.69</sub>, Mn<sub>0.67</sub>Fe<sub>0.33</sub>, Mn<sub>0.93</sub>Fe<sub>0.07</sub> at pH 7 and Mn<sub>0.68</sub>Fe<sub>0.32</sub>, Mn<sub>0.89</sub>Fe<sub>0.11</sub>, Mn<sub>0.90</sub>Fe<sub>0.10</sub> at pH 9. The co-occurrence of Fe(II) provided hydrous FeO<sub><i>x</i></sub> surfaces enriched with chemisorbed oxygen (∼60%), acting as nucleation sites for the heterogeneous MnO<sub><i>x</i></sub> oxidation through enhanced electron transfer and surface complexation pathways. This co-occurrence thus reduced the half-life time of PMS-induced Mn(II) oxidation, by 5.3–18.7 times compared to the Mn(II) oxidation alone. This study provides fresh evidence, underscoring the significance of O<sub>2</sub><sup>•–</sup> in PMS-mediated metal oxidation systems.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"8 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142255993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1021/acsestengg.4c00389
Jingyi Zhu, Yuanxi Huang, Lingjun Bu, Yangtao Wu, Shiqing Zhou
Machine learning (ML) has become a crucial tool to accelerate research in advanced oxidation processes via predicting reaction parameters to evaluate the treatability of micropollutants (MPs). However, insufficient data sets and an incomplete prediction mechanism remain obstacles toward the precise prediction of MP treatability by a hydroxyl radical (HO•), especially when k values approach the diffusion-controlled limit. Herein, we propose a novel graph neural network (GNN) model integrating self-supervised pretraining on a large unlabeled data set (∼10 million) to predict the kHO values on MPs. Our model outperforms the common-seen and literature-established ML models on both whole data sets and diffusion-controlled limit data sets. Benefiting from the pretraining process, we demonstrate that k-value-related chemistry wisdom contained in the pretrained data set is fully exploited, and the learned knowledge can be transferred among data sets. In comparison with molecular fingerprints, we identify that molecular graphs (MGs) cover more structural information beyond substituents, facilitating a k-value prediction near the diffusion-controlled limit. In particular, we observe that mechanistic pathways of HO•-initiated reactions could be automatically classified and mapped out on the penultimate layer of our model. The phenomenon shows that the GNN model can be trained to excavate mechanistic knowledge by analyzing the kinetic parameters. These findings not only well interpret the robust model performance but also extrapolate the k-value prediction model to mechanistic elucidation, leading to better decision making in water treatment.
通过预测反应参数来评估微污染物（MPs）的可处理性，机器学习（ML）已成为加速高级氧化过程研究的重要工具。然而，数据集不足和预测机制不完整仍然是精确预测羟基自由基（HO-）对 MP 的可处理性的障碍，尤其是当 k 值接近扩散控制极限时。在此，我们提出了一种新颖的图神经网络（GNN）模型，该模型整合了对大量无标记数据集（1000 万）的自监督预训练，用于预测 MP 的 kHO 值。在整个数据集和扩散控制极限数据集上，我们的模型都优于常见的和文献中建立的 ML 模型。得益于预训练过程，我们证明了预训练数据集中包含的与 k 值相关的化学智慧得到了充分利用，并且所学知识可以在数据集之间转移。与分子指纹相比，我们发现分子图（MGs）涵盖了取代基以外的更多结构信息，有助于在扩散控制极限附近进行 k 值预测。特别是，我们观察到，在我们模型的倒数第二层，HO--引发反应的机理路径可以自动分类和绘制。这一现象表明，通过分析动力学参数，可以训练 GNN 模型挖掘机理知识。这些发现不仅很好地诠释了稳健模型的性能，而且将 k 值预测模型推向了机理阐释，从而在水处理方面做出更好的决策。
{"title":"Graph Neural Network Integrating Self-Supervised Pretraining for Precise and Interpretable Prediction of Micropollutant Treatability by HO•-Based Advanced Oxidation Processes","authors":"Jingyi Zhu, Yuanxi Huang, Lingjun Bu, Yangtao Wu, Shiqing Zhou","doi":"10.1021/acsestengg.4c00389","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00389","url":null,"abstract":"Machine learning (ML) has become a crucial tool to accelerate research in advanced oxidation processes via predicting reaction parameters to evaluate the treatability of micropollutants (MPs). However, insufficient data sets and an incomplete prediction mechanism remain obstacles toward the precise prediction of MP treatability by a hydroxyl radical (HO<sup>•</sup>), especially when <i>k</i> values approach the diffusion-controlled limit. Herein, we propose a novel graph neural network (GNN) model integrating self-supervised pretraining on a large unlabeled data set (∼10 million) to predict the <i>k</i><sub>HO</sub> values on MPs. Our model outperforms the common-seen and literature-established ML models on both whole data sets and diffusion-controlled limit data sets. Benefiting from the pretraining process, we demonstrate that <i>k</i>-value-related chemistry wisdom contained in the pretrained data set is fully exploited, and the learned knowledge can be transferred among data sets. In comparison with molecular fingerprints, we identify that molecular graphs (MGs) cover more structural information beyond substituents, facilitating a <i>k</i>-value prediction near the diffusion-controlled limit. In particular, we observe that mechanistic pathways of HO<sup>•</sup>-initiated reactions could be automatically classified and mapped out on the penultimate layer of our model. The phenomenon shows that the GNN model can be trained to excavate mechanistic knowledge by analyzing the kinetic parameters. These findings not only well interpret the robust model performance but also extrapolate the <i>k</i>-value prediction model to mechanistic elucidation, leading to better decision making in water treatment.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"18 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1021/acsestengg.4c00384
Jiasi Sun, Xi Zhang, Jianjun Guan, Zhen He
Producing volatile fatty acids (VFAs) in anaerobic digestion (AD) is of strong interest because of VFAs’ potential values in biomanufacturing. Despite some success of VFA production via pretreatment, in situ inhibition of methanogens for VFA accumulation has yet to be explored. Herein, a system consisting of hydrogen peroxide (H2O2) production, application of H2O2 for inhibiting methanogens in AD, and VFA separation was investigated. A polytetrafluoroethylene-based electrospinning electrode was synthesized and capable of generating ∼4.2 g L–1 H2O2. When the generated H2O2 was applied to the AD, methanogens were inhibited, and VFA accumulation occurred. With the addition of 80 mg L–1 H2O2, an average VFA concentration of 10.6 g COD L–1 was obtained. The long-term H2O2 inhibition effect on methanogenesis was examined for nearly 100 days. A 2.3- to 3.3-fold increase in malondialdehyde levels, which indicated increased cell damage, along with a significant decrease in methane production and an increase in VFA concentration, might suggest that H2O2 could potentially inhibit methanogens while allowing acidogenic bacteria to remain functional. The accumulated VFAs were separated and then recovered using an electrodialysis unit, with a maximum VFA concentration of 26.7 g COD L–1. The results of this study will encourage further exploration of the proposed system for VFA production by addressing several challenges, including a better understanding of the inhibition mechanism and a further increase in VFA yields.
{"title":"Volatile Fatty Acid Production through Arresting Methanogenesis by Electro-Synthesized Hydrogen Peroxide in Anaerobic Digestion and Subsequent Recovery by Electrodialysis","authors":"Jiasi Sun, Xi Zhang, Jianjun Guan, Zhen He","doi":"10.1021/acsestengg.4c00384","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00384","url":null,"abstract":"Producing volatile fatty acids (VFAs) in anaerobic digestion (AD) is of strong interest because of VFAs’ potential values in biomanufacturing. Despite some success of VFA production via pretreatment, in situ inhibition of methanogens for VFA accumulation has yet to be explored. Herein, a system consisting of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) production, application of H<sub>2</sub>O<sub>2</sub> for inhibiting methanogens in AD, and VFA separation was investigated. A polytetrafluoroethylene-based electrospinning electrode was synthesized and capable of generating ∼4.2 g L<sup>–1</sup> H<sub>2</sub>O<sub>2</sub>. When the generated H<sub>2</sub>O<sub>2</sub> was applied to the AD, methanogens were inhibited, and VFA accumulation occurred. With the addition of 80 mg L<sup>–1</sup> H<sub>2</sub>O<sub>2</sub>, an average VFA concentration of 10.6 g COD L<sup>–1</sup> was obtained. The long-term H<sub>2</sub>O<sub>2</sub> inhibition effect on methanogenesis was examined for nearly 100 days. A 2.3- to 3.3-fold increase in malondialdehyde levels, which indicated increased cell damage, along with a significant decrease in methane production and an increase in VFA concentration, might suggest that H<sub>2</sub>O<sub>2</sub> could potentially inhibit methanogens while allowing acidogenic bacteria to remain functional. The accumulated VFAs were separated and then recovered using an electrodialysis unit, with a maximum VFA concentration of 26.7 g COD L<sup>–1</sup>. The results of this study will encourage further exploration of the proposed system for VFA production by addressing several challenges, including a better understanding of the inhibition mechanism and a further increase in VFA yields.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"18 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1021/acsestengg.4c00269
Puranjan Mishra, Ifunanya R. Akaniro, Ruilong Zhang, Peixin Wang, Yiqi Geng, Dongyi Li, Qiuxiang Xu, Jonathan W. C. Wong, Jun Zhao
The coordinated system of inorganic nanoparticle-intact living cells has shown great potential in fermentative hydrogen (H2) production. Meanwhile, sluggish electron transfer and energy loss during transmembrane diffusion restrict the production of biohydrogen (BioH2). Herein, iron oxide, nickel oxide, and Ni/Fe2O3 bimetallic nanocomposites were prepared through the coprecipitation method to investigate their potential effect on the dark fermentative hydrogen production (DFHP) system. The results showed that BioH2 production could be enhanced by using nickel and iron oxide composites in DFHP, surpassing the performance of individual iron oxide or nickel oxide and their physical mixture. Specifically, Ni/Fe2O3-5% added to the feed at 150 mg/L increased the BioH2 yields by 51.24% compared to that in its controlled experiment. The microbial community analysis confirmed a significant change in compositional proportions of the microbiome structure of DFHP in response to Ni/Fe2O3-5 wt %. The Enterobacter species proportions increased from 32.0% to 39.0%, along with some unclassified genera of microbial communities, from 34.0% to 42.0%, by supplementation of the nanomaterials. Enterobacter species are versatile facultative hydrogen producers and can use various organic wastes as the sole carbon source. The results suggested that the supplemented Ni/Fe2O3-5% induced the glycolytic efficacy and Fe and Ni availability, thereby increasing the hydrogenase activities. This study provided novel insights into integrating Ni/Fe2O3 into the DFHP system and depicted its potential as an excellent catalyst to increase BioH2 production. The distinctive microbial communities, unidentified hydrogen-producing bacteria, and increased BioH2 yield due to the presence of Ni/Fe2O3 in the DFHP system suggest unique and substantial advantages for the sustainable use of bimetallic nanomaterials in fermentation technology.
{"title":"Unlocking the Potential of Ni/Fe2O3 Bimetallic Nanoparticles for Fermentative Biohydrogen Production","authors":"Puranjan Mishra, Ifunanya R. Akaniro, Ruilong Zhang, Peixin Wang, Yiqi Geng, Dongyi Li, Qiuxiang Xu, Jonathan W. C. Wong, Jun Zhao","doi":"10.1021/acsestengg.4c00269","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00269","url":null,"abstract":"The coordinated system of inorganic nanoparticle-intact living cells has shown great potential in fermentative hydrogen (H<sub>2</sub>) production. Meanwhile, sluggish electron transfer and energy loss during transmembrane diffusion restrict the production of biohydrogen (BioH<sub>2</sub>). Herein, iron oxide, nickel oxide, and Ni/Fe<sub>2</sub>O<sub>3</sub> bimetallic nanocomposites were prepared through the coprecipitation method to investigate their potential effect on the dark fermentative hydrogen production (DFHP) system. The results showed that BioH<sub>2</sub> production could be enhanced by using nickel and iron oxide composites in DFHP, surpassing the performance of individual iron oxide or nickel oxide and their physical mixture. Specifically, Ni/Fe<sub>2</sub>O<sub>3</sub>-5% added to the feed at 150 mg/L increased the BioH<sub>2</sub> yields by 51.24% compared to that in its controlled experiment. The microbial community analysis confirmed a significant change in compositional proportions of the microbiome structure of DFHP in response to Ni/Fe<sub>2</sub>O<sub>3</sub>-5 wt %. The Enterobacter species proportions increased from 32.0% to 39.0%, along with some unclassified genera of microbial communities, from 34.0% to 42.0%, by supplementation of the nanomaterials. Enterobacter species are versatile facultative hydrogen producers and can use various organic wastes as the sole carbon source. The results suggested that the supplemented Ni/Fe<sub>2</sub>O<sub>3</sub>-5% induced the glycolytic efficacy and Fe and Ni availability, thereby increasing the hydrogenase activities. This study provided novel insights into integrating Ni/Fe<sub>2</sub>O<sub>3</sub> into the DFHP system and depicted its potential as an excellent catalyst to increase BioH<sub>2</sub> production. The distinctive microbial communities, unidentified hydrogen-producing bacteria, and increased BioH<sub>2</sub> yield due to the presence of Ni/Fe<sub>2</sub>O<sub>3</sub> in the DFHP system suggest unique and substantial advantages for the sustainable use of bimetallic nanomaterials in fermentation technology.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"40 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-17DOI: 10.1021/acsestengg.4c00421
Weimin Cheng, Ke Shi, Duc-Viet Nguyen, Jianliang Xue, Qing Jiang, Di Wu, Yanlu Qiao, An Liu
Microbial electrolysis cells (MECs) are promising for the treatment of sulfate-laden wastewater. The performance of the MEC cathode biofilms is influenced not only by the wastewater quality but also by the hydrodynamic mixing condition. Yet, the combined effects of these combined conditions have seldom been explored. This study examines the effectiveness and operational patterns of MECs in treating sulfate-laden wastewater under varying heavy-metal (Cu2+ as representative) concentrations (0–80 mg L–1) and different hydrodynamic conditions (complete-mixing (CM) and nonmixing (NM, as control)). Results showed that CM-MECs achieved higher sulfate reduction efficiency (51 to 76%) compared to NM-MECs (with 46–69% of sulfate reduction) across the range of Cu2+ concentrations. Kinetic analysis revealed that CM-MECs reduced sulfate faster due to increased expression of genes involved in sulfate reduction and electron transport. Furthermore, CM-MECs maintained intact cell structures, enhanced electron transfer, and increased the relative abundance of Desulfobulbus when treating wastewater with low Cu2+ concentrations (<40 mg L–1). Microbial defense mechanisms against Cu2+ also contributed to the enhanced sulfate reduction efficiency in the CM-MECs. These findings offer new insights into the design MECs with flowing conditions and pave the way for their future application in the treatment of heavy metal and sulfate-laden wastewater.
{"title":"Enhancing Sulfate Reduction Efficiency in Microbial Electrolysis Cells: The Impact of Mixing Conditions and Heavy-Metal Concentrations on Functional Genes, Cell Activity, and Community Structure in Sulfate-Laden Wastewater Treatment","authors":"Weimin Cheng, Ke Shi, Duc-Viet Nguyen, Jianliang Xue, Qing Jiang, Di Wu, Yanlu Qiao, An Liu","doi":"10.1021/acsestengg.4c00421","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00421","url":null,"abstract":"Microbial electrolysis cells (MECs) are promising for the treatment of sulfate-laden wastewater. The performance of the MEC cathode biofilms is influenced not only by the wastewater quality but also by the hydrodynamic mixing condition. Yet, the combined effects of these combined conditions have seldom been explored. This study examines the effectiveness and operational patterns of MECs in treating sulfate-laden wastewater under varying heavy-metal (Cu<sup>2+</sup> as representative) concentrations (0–80 mg L<sup>–1</sup>) and different hydrodynamic conditions (complete-mixing (CM) and nonmixing (NM, as control)). Results showed that CM-MECs achieved higher sulfate reduction efficiency (51 to 76%) compared to NM-MECs (with 46–69% of sulfate reduction) across the range of Cu<sup>2+</sup> concentrations. Kinetic analysis revealed that CM-MECs reduced sulfate faster due to increased expression of genes involved in sulfate reduction and electron transport. Furthermore, CM-MECs maintained intact cell structures, enhanced electron transfer, and increased the relative abundance of <i>Desulfobulbus</i> when treating wastewater with low Cu<sup>2+</sup> concentrations (<40 mg L<sup>–1</sup>). Microbial defense mechanisms against Cu<sup>2+</sup> also contributed to the enhanced sulfate reduction efficiency in the CM-MECs. These findings offer new insights into the design MECs with flowing conditions and pave the way for their future application in the treatment of heavy metal and sulfate-laden wastewater.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"12 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142255865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The oxygen functionalization of multiwalled carbon nanotubes (CNTs) could enhance their reactivity in catalytic ozonation for hydroxyl radical (•OH) formation. However, the detailed pathway for the transformation of ozone to •OH and the mechanism for the decreased treatment performance at acidic pH values remain unclear. In this study, surface oxygen-functionalized CNTs (O-CNTs) were prepared and used in catalytic ozonation to reveal the pathway for •OH formation. The efficiencies of ozone utilization and its conversion to •OH were increased by 2.7 and 554.8 times, respectively, under the catalysis of the O-CNTs. The great reactivity of the O-CNTs was related to their high surface oxygen contents and increased dispersion. Hydrogen peroxide was generated as a significant intermediate during the catalytic ozonation of the O-CNTs. The exposure of this substance linearly correlated with •OH exposure and pollutant degradation constants, with correlation coefficients of 0.991 and 0.911, respectively. The formation of hydrogen peroxide was relatively slower at acidic pH values, which explains the low performance of catalytic ozonation. A mechanism was proposed that involved the generation of hydrogen peroxide to trigger the peroxone process for free •OH formation. These findings deepen our understanding of oxygen functionalization and offer insights into the catalytic ozonation of surface oxygen-rich carbonaceous materials.
{"title":"Oxygen Functionalization of Carbon Nanotubes Shifted the Formation Pathway of Hydroxyl Radicals in Catalytic Ozonation: The Overlooked Role of Hydrogen Peroxide","authors":"Yanye Tian, Yingtong Li, Guang-Guo Ying, Deli Wu, Kaimin Shih, Yong Feng","doi":"10.1021/acsestengg.4c00403","DOIUrl":"https://doi.org/10.1021/acsestengg.4c00403","url":null,"abstract":"The oxygen functionalization of multiwalled carbon nanotubes (CNTs) could enhance their reactivity in catalytic ozonation for hydroxyl radical (<sup>•</sup>OH) formation. However, the detailed pathway for the transformation of ozone to <sup>•</sup>OH and the mechanism for the decreased treatment performance at acidic pH values remain unclear. In this study, surface oxygen-functionalized CNTs (O-CNTs) were prepared and used in catalytic ozonation to reveal the pathway for <sup>•</sup>OH formation. The efficiencies of ozone utilization and its conversion to <sup>•</sup>OH were increased by 2.7 and 554.8 times, respectively, under the catalysis of the O-CNTs. The great reactivity of the O-CNTs was related to their high surface oxygen contents and increased dispersion. Hydrogen peroxide was generated as a significant intermediate during the catalytic ozonation of the O-CNTs. The exposure of this substance linearly correlated with <sup>•</sup>OH exposure and pollutant degradation constants, with correlation coefficients of 0.991 and 0.911, respectively. The formation of hydrogen peroxide was relatively slower at acidic pH values, which explains the low performance of catalytic ozonation. A mechanism was proposed that involved the generation of hydrogen peroxide to trigger the peroxone process for free <sup>•</sup>OH formation. These findings deepen our understanding of oxygen functionalization and offer insights into the catalytic ozonation of surface oxygen-rich carbonaceous materials.","PeriodicalId":7008,"journal":{"name":"ACS ES&T engineering","volume":"31 1","pages":""},"PeriodicalIF":7.1,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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