Toxic effects of ship exhaust gas closed-loop scrubber wash water.

To meet the strict requirements of reducing sulfur emissions, an increasing number of commercial ships have installed exhaust gas cleaning systems (EGCSs). However, wash water produced during the cleaning process is discharged back to the marine environment. We investigated the effects of closed-loop scrubber (natrium-alkali method) wash water on three trophic species. Severe toxic effects were found when Dunaliella salina, Mysidopsis bahia, and Mugilogobius chulae were exposed to 0.63-6.25, 0.63-10, and 1.25-20% concentrations of wash water, respectively. The 50% effective concentration in 96 h (EC50-96 h) for D. salina was 2.48%, and the corresponding total polycyclic aromatic hydrocarbons (PAHs) and heavy metals were 22.81 and 23.67 µg L-1. The 50% lethal concentration in 7 d (LC50-7 d) values for M. bahia and M. chulae were 3.57% and 20.50%, respectively. The lowest observed effect concentration (LOEC) values for M. bahia and M. chulae were 1.25% and 2.5%, respectively, and the corresponding total PAHs and heavy metals were 11.50 and 11.93 and 22.99 and 23.86 µg L-1. M. bahia's body weight was negatively correlated with the amount of wash water. Low concentrations of wash water (0-5%) had no significant effect on the reproduction of M. bahia. Although concentrations of 16 PAHs and 8 heavy metals are known, different compounds might react with each other and form more unknown toxic substances, and the measured toxicity comes from synergistic effects between various pollutants. Therefore, future work is needed to clarify other more toxic contaminants in wash water. We highly recommend that wash water be treated before being discharged to the marine environment.

Magnetic seeds promoted high-density sulfonic acid-based hydrochar derived from sugar-rich wastewater for removal of methylene blue.

Methylene blue (MB) removal from dyeing wastewater using low-cost bio-derived adsorbent is a significant and challenging field. Herein, magnetic sugar hydrochar (MGHC) precursors derived from sugar-rich wastewater with small particle size and rich oxygen-containing functional groups (OCFGs) are prepared from sugar-rich aqueous solution via Fe salt-modified hydrothermal procedure. The role of Fe3O4 nanoparticles formed during the sugar carbonization is to provide numerous magnetic seeds to generate MGHC with core-shell structure, which reduces the particle size of hydrochar. This increases the amount of OCFGs on the surface of MGHC for bonding the sulfonic acid groups. Therefore, sulfonic acid-modified MGHC-SA shows the rapid MB adsorption rate and excellent adsorption capacity. The highest MB capacity is 869.6 mg/g at pH = 11.0 and 298 K. Additionally, the MGHC-SA can be easily recovery by magnet. And the stability of MGHC-SA was also evaluated, no degradation of adsorption performance was observed, even the adsorbent was regenerated 10 times. This study puts forward a promising way to acquire functional groups rich and easy recovery hydrochar from sugar wastewater for MB removal.

Dehydrogenation of Cyclohexanones to Phenols: A Mini Review.

BACKGROUND: Phenol and its derivatives are important intermediates in the chemical industry, especially the pharmaceutical and electronic industries. The synthesis of phenols has attracted the attention of scientists due to their importance. Dehydrogenation of cyclohexanones is one of the promising aromatization strategies for phenols manufacture because the raw materials are low cost and stable. In recent years, some efficient and green methods with the use of H2, O2 and air, alkene, H2 and O2-free are described. OBJECTIVE: This mini-review will summarize some recent developments relating to the dehydrogenation of cyclohexanones to phenols, along with their interesting mechanism aspects. The challenges and future trends of the transformation will be prospected. CONCLUSION: The synthesis of phenols from the dehydrogenation of cyclohexanones has recently attracted much attention. Some synthetic methods have been established, and interesting mechanisms have been proposed in some cases. Lots of catalysts were developed for the transformation to afford the corresponding product. Although the present methods still have drawbacks and limitations, it is supposed that many novel methods would probably be developed in the near future.

Quasi-Covalently Coupled Ni-Cu Atomic Pair for Synergistic Electroreduction of CO2.

Developing highly active, selective, and stable electrocatalysts for the carbon dioxide reduction reaction (CO2RR) is crucial to establish a CO2 conversion system for industrial implementation and, therefore, to realize an artificially closed carbon loop. This can only be achieved through the rational material design based upon the knowledge of the operational active site at the molecular scale. Enlightened by theoretical screening, herein, we for the first time manipulate a novel Ni-Cu atomic pair configuration toward improved CO2RR performance. Systematic characterizations and theoretical modeling reveal that the secondary Cu metal incorporation positively shifts the Ni 3d orbital energy to the Fermi level and thus accelerates the rate-determining step, *COOH formation. In addition, the intrinsic inactivity of Cu toward the competing hydrogen evolution reaction causes a considerable reaction barrier for water dissociation on the Ni-Cu moiety. Due to these attributes, the as-developed Ni/Cu-N-C catalyst exhibits excellent catalytic activity and selectivity, with a record-high turnover frequency of 20,695 h-1 at -0.6 V (vs RHE) and a maximum Faradaic efficiency of 97.7% for CO production. Furthermore, the dynamic structure evolution monitored by operando X-ray absorption fine-structure spectroscopy unveils the interaction between the Ni center and CO2 molecules and the synergistic effect of the Ni-Cu atomic pair on CO2RR activity.

Manipulating Au-CeO2 Interfacial Structure Toward Ultrahigh Mass Activity and Selectivity for CO2 Reduction.

Deploying the application of Au-based catalysts directly on CO2 reduction reactions (CO2 RR) relies on the simultaneous improvement of mass activity (usually lower than 10 mA mg-1 Au at -0.6 V) and selectivity. To achieve this target, we herein manipulate the interface of small-size Au (3.5 nm) and CeO2 nanoparticles through adjusting the surface charge of Au and CeO2 . The well-regulated interfacial structure not only guarantees the utmost utilization of Au, but also enhances the CO2 adsorption. Consequently, the mass activity (CO) of the optimal AuCeO2 /C catalyst reaches 139 mA mg-1 Au with 97 % CO faradaic efficiency (FECO ) at -0.6 V. Moreover, the strong interaction between Au and CeO2 endows the catalyst with excellent long-term stability. This work affords a charge-guided approach to construct the interfacial structure for CO2 RR and beyond.

Deep-Breathing Honeycomb-like Co-Nx-C Nanopolyhedron Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries.

Metal organic framework (MOF) derivatives have been extensively used as bifunctional oxygen electrocatalysts. However, the utilization of active sites is still not satisfactory owing to the sluggish mass transport within their narrow pore channels. Herein, interconnected macroporous channels were constructed inside MOFs-derived Co-Nx-C electrocatalyst to unblock the mass transfer barrier. The as-synthesized electrocatalyst exhibits a honeycomb-like morphology with highly exposed Co-Nx-C active sites on carbon frame. Owing to the interconnected ordered macropores throughout the electrocatalyst, these active sites can smoothly "exhale/inhale" reactants and products, enhancing the accessibility of active sites and the reaction kinetics. As a result, the honeycomb-like Co-Nx-C displayed a potential difference of 0.773 V between the oxygen evolution reaction potential at 10 mA cm-2 and the oxygen reduction reaction half-wave potential, much lower than that of bulk-Co-Nx-C (0.842 V). The rational modification on porosity makes such honeycomb-like MOF derivative an excellent bifunctional oxygen electrocatalyst in rechargeable Zn-air batteries.

A novel method to prepare a magnetic carbon-based adsorbent with sugar-containing water as the carbon source and DETA as the modifying reagent.

A novel magnetic heavy metal adsorbent was prepared via diethylenetriamine (DETA) modification on magnetic hydrothermal carbon, with glucose and sugar-containing waste water as the carbon source. The prepared materials were characterized by FT-IR, SEM, TEM, EDXRF, TGA, elemental analysis, XPS, and magnetic moment determination. In this paper, the adsorption mechanism of the modified and unmodified adsorbents was well discussed. Four kinds of waste water (watermelon juice, expired sprite, sugar-pressing waste water, and confectionary waste water) were employed to produce heavy metal ion adsorbents; the chemical properties of hydrothermal carbon derived from the proposed sources were analyzed as well. The maximum uptake capacity for Cu2+, Pb2+, and Cd2+ of the adsorbent produced from glucose was 26.88, 103.09, and 25.38 mg g-1, respectively. After 5 cycles, the adsorption ability was still well preserved. This work represents an efficient new direction for the treatment of heavy metal ions in water and the reuse of sugar-containing waste water. Graphical abstract The schemetic of DETA-modified magnetic carbon preparing from sugar-containing wastewater.