A complete review on the oxygen-containing functional groups of biochar: Formation mechanisms, detection methods, engineering, and applications.

Biochar is a porous carbon material generated by the thermal treatment of biomass under anaerobic or anoxic conditions with wealthy Oxygen-containing functional groups (OCFGs). To date, OCFGs of biochar have been extensively studied for their significant utility in pollutant removal, catalysis, capacitive applications, etc. This review adopted a whole system philosophy and systematically summarizes up-to-date knowledge of formation, detection methods, engineering, and application for OCFGs. The formation mechanisms and detection methods of OCFGs, as well as the relationships between OCFGs and pyrolysis conditions (such as feedstocks, temperature, atmosphere, and heating rate), were discussed in detail. The review also summarized strategies and mechanisms for the oxidation of biochar to afford OCFGs, with the performances and mechanisms of OCFGs in the various application fields (environmental remediation, catalytic biorefinery, and electrode material) being highlighted. In the end, the future research direction of biochar OCFGs was put forward.

Biomimetic mercury immobilization by selenium functionalized polyphenylene sulfide fabric.

Highly efficient decontamination of elemental mercury (Hg0) remains an enormous challenge for public health and ecosystem protection. The artificial conversion of Hg0 into mercury chalcogenides could achieve Hg0 detoxification and close the global mercury cycle. Herein, taking inspiration from the bio-detoxification of mercury, in which selenium preferentially converts mercury from sulfoproteins to HgSe, we propose a biomimetic approach to enhance the conversion of Hg0 into mercury chalcogenides. In this proof-of-concept design, we use sulfur-rich polyphenylene sulfide (PPS) as the Hg0 transporter. The relatively stable, sulfur-linked aromatic rings result in weak adsorption of Hg0 on the PPS rather than the formation of metastable HgS. The weakly adsorbed mercury subsequently migrates to the adjacent selenium sites for permanent immobilization. The sulfur-selenium pair affords an unprecedented Hg0 adsorption capacity and uptake rate of 1621.9 mg g-1 and 1005.6 µg g-1 min-1, respectively, which are the highest recorded values among various benchmark materials. This work presents an intriguing concept for preparing Hg0 adsorbents and could pave the way for the biomimetic remediation of diverse pollutants.

Self-Constructing 100% Water-Resistant Metal Sulfides through In Situ Acid Etching for Effective Elemental Mercury (Hg0) Capture.

Metal sulfides (MSs) can efficiently entrap thiophilic components, such as elemental mercury (Hg0), and realize environmental remediation. However, there is still a critical problem challenging the extensive application of MSs in related areas, i.e., how to self-regulate their water (H2O) resistance without complexing the sorbent preparation procedure. This work for the first time developed an in situ acid-etching method that self-engineered the water affinity of MSs through changing the interfacial interaction between MSs and Hg0/H2O. The introduction of abundant, undercoordinated sulfur onto the sorbent surface was the primary reason accounting for the significantly improved H2O resistance. The high surface coverage of undercoordinated sulfur induced the formation of polysulfur chains (Sx2-) that stabilized Hg0 via a bridging bond and repelled H2O, attributed to the favorable electron configurations. These properties made the surface of MSs highly hydrophobic and increased the adsorption selectivity toward Hg0 over H2O. The MSs exhibited 100% H2O resistance even in the presence of 20% H2O, which is much higher than the H2O concentration under most practical scenarios. From these perspectives, this work for the first time overcame the detrimental effects of H2O on MSs through a self-regulating way that is scalable and negligibly complexes the sorbent preparation pathway. The highly water-resistant and cost-effective MSs as prepared can serve as efficient Hg0 removal from industrial flue gas in the future.

In situ acid etching boosts mercury accommodation capacities of transition metal sulfides.

Transition Metal sulfides (TMSs) are effective sorbents for entrapment of highly polluting thiophiles such as elemental mercury (Hg0). However, the application of these sorbents for mercury removal is stymied by their low accommodation capacities. Among the transition metal sulfides, only CuS has demonstrated industrially relevant accommodation capacity. The rest of the transition metal sulfides have 100-fold lower capacities than CuS. In this work, we overcome these limitations and develop a simple and scalable process to enhance Hg0 accommodation capacities of TMSs. We achieve this by introducing structural motifs in TMSs by in situ etching. We demonstrate that in situ acid etching produces TMSs with defective surface and pore structure. These structural motifs promote Hg0 surface adsorption and diffusion across the entire TMSs architecture. The process is highly versatile and the in situ etched transition metal sulfides show over 100-fold enhancement in their Hg0 accommodation capacities. The generality and the scalability of the process provides a framework to develop TMSs for a broad range of applications.

Machine learning assisted predicting and engineering specific surface area and total pore volume of biochar.

Biochar produced from pyrolysis of biomass is a platform porous carbon material that have been widely used in many areas. Specific surface area (SSA) and total pore volume (TPV) are decisive to biochar application in hydrogen uptake, CO2 adsorption, and organic pollutant removal, etc. Engineering biochar by traditional experimental methods is time-consuming and laborious. Machine learning (ML) was used to effectively aid the prediction and engineering of biochar properties. The prediction of biochar yield, SSA, and TPV was achieved via random forest (RF) and gradient boosting regression (GBR) with test R2 of 0.89-0.94. ML model interpretation indicates pyrolysis temperature, biomass ash, and volatile matter were the most important features to the three targets. Pyrolysis parameters and biomass mixing ratios for biochar production were optimized via three-target GBR model, and the optimum schemes to obtain high SSA and TPV were experimentally verified, indicating the great potential of ML for biochar engineering.

Activation of ozone by peroxymonosulfate for selective degradation of 1,4-dioxane: Limited water matrices effects.

The presence of 1,4-dioxane in various water streams poses a threat to the health of human beings. In this study, the oxidative combination of ozone with peroxymonosulfate (PMS) was for the first time used to remove 1,4-dioxane from water. Near complete abatement of 1,4-dioxane was achieved by ozone-PMS after reaction of only 15 min and the degradation kinetics was found to be positively correlated with doses of PMS and ozone. Ozone-PMS oxidation had the optimum performance at slight base pH values. Both sulfate radicals and hydroxyl radicals were generated in ozone-PMS oxidation and these radicals resulted in the degradation of 1,4-dioxane. The effects of common water constituents and real water matrices were investigated. It was found that bicarbonate ions with a concentration up to 10 mM had a slight promoting effect, while either chloride ions or natural organic matter inhibited only slightly the degradation. Meanwhile, no obvious difference in the degradation of 1,4-dioxane was found among the real water matrices and deionized water, which demonstrates that ozone-PMS oxidation has high tolerance and stability. The results from this study demonstrate that ozone-PMS may be a promising technology for the removal of 1,4-dioxane from various water matrices.

Tetrahydroxydiboron and Nickel Chloride Cocatalyzed Rapid Radical Cyclization toward Pyrrolizidine and Indolizidine Alkaloids.

A novel tetrahydroxydiboron and nickel chloride cocatalyzed radical cyclization cascade with a broad substrate scope and an ultrashort reaction time was developed. The mechanistic investigation indicated that the reaction might involve a homocleavage of tetrahydroxydiboron and nickel hydride intermediates. This approach enables the simple and efficient synthesis of a series of heteropolycycles.

Correlation between serum C-peptide-releasing effects and the risk of elevated uric acid in type 2 diabetes mellitus.

Our study aimed to investigate the C-peptide-releasing effect associated with the risk of elevated serum uric acid (SUA) levels in patients with type 2 diabetes mellitus (T2DM). In the cross-sectional study, 345 patients with T2DM hospitalized at the First Affiliated Hospital of Harbin Medical University were consecutively enrolled, and their baseline data were collected. The study design used two parameters for C-peptide releasing effects: the multiplication effect of 1 h postprandial C-peptide to fasting C-peptide ratio (1hCp/FCp) and 2hCp/FCp; the incremental effect of 1hCp minus FCp (1hΔCp) and 2hΔCp. The patients with T2DM in the upper quartiles of SUA had higher FCp, 1hCp, 1hΔCp, 2hCp, and 2hΔCp. Multiple linear regression analysis revealed that after adjusting all the confounding factors, the serum C-peptide including 1hCp (ß = 5.14, p = 0.036), 1hΔCp (ß = 7.80, p = 0.010), 2hCp (ß = 4.27, p = 0.009) and 2hΔCp (ß = 5.20, p = 0.005) were still positively correlated with SUA levels in patients with T2DM. In female patients, only the 2hCp (ß = 4.78, p = 0.017) and 2hΔCp (ß = 5.28, p = 0.019) were associated with SUA level; however, in male patients, no C-peptide parameter was associated with SUA levels in T2DM (all p > 0.05). Within a certain range, the elevated SUA levels might be associated with the better C-peptide incremental effect of islet ß cell function in T2DM, especially in female patients.

Removal of flue gas mercury by porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt medium.

Porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt (LiCl-KCl) medium were employed for Hg0 removal. The carbons derived from molten salt carbonization (MSC) displayed much superior Hg0 removal performance comparing with the carbons derived from N2 pyrolysis method (NC). The best molar ratio of LiCl-KCl was 59:41, the optimal molten salt temperature was 700 °C, and the best mass ratio of wood sawdust to molten salt was 1:10. The MSC displayed good applicability at 50-125 °C. The saturation Hg0 adsorption capacity of MSC was about 7828.39 µg·g-1, far exceeding those for carbonaceous adsorbents reported in literatures. A Hg0 removal mechanism over MSC was proposed, i.e., the hierarchical porous structure accelerated mass transfer of Hg0, and the CO groups served as electron acceptors from Hg0 atoms to form organic matter bonded mercury (Hg-OM). The molten salt could be easily separated from the mixture of MSC for recycling multiple times. Thus, molten salt carbonization method appears to be promising in one-pot carbonization and activation of biomass as efficient adsorbents for gaseous Hg0.

Coordinatively Unsaturated Selenides over CuFeSe2 toward Highly Efficient Mercury Immobilization.

Metal selenides have been demonstrated as promising Hg0 remediators, while their inadequate adsorption rate primarily impedes their application feasibility. Based on the critical role of coordinatively unsaturated selenide ligands in immobilizing Hg0, this work proposed a novel strategy to enhance the Hg0 adsorption rate of metal selenides by magnitudes by purposefully adjusting the selenide saturation. Copper iron diselenide (CuFeSe2), in which the surface reconstruction tended to occur at ambient temperature, was adopted as the concentrator of unsaturated selenides. The adsorption rate of CuFeSe2 reached as high as 900.71 µg·g-1·min-1, far exceeding those of the previously reported metal selenides by at least 1 magnitude. The excellent resistance of CuFeSe2 to flue gas interference and temperature fluctuation warrants its applicability in real-world conditions. The theoretical investigations and mechanistic interpretations based on density functional theory (DFT) calculation further confirmed the indispensable role of unsaturated selenides in Hg0 adsorption. This work aims not only to develop a Hg0 remediator with extensive applicability in coal combustion flue gas but also to take a step toward the rational design of selenide-based sorbents for diverse environmental remediation by the facile surface functionalization of coordinatively adjustable ligands.

Activation of peroxymonosulfate by molybdenum disulfide-mediated traces of Fe(III) for sulfadiazine degradation.

The activation of persulfate by ferrous iron (Fe(II)) is of great interest to the environmental remediation community, but the reduction of ferric iron (Fe(III)) to Fe(II) is slow and the accumulation of iron sludge resulted from the precipitation of Fe(III) is a great concern. Here, molybdenum disulfide (MoS2) was studied as a co-catalyst to improve the activation of peroxymonosulfate (PMS) by Fe(III) for sulfadiazine (SDZ) degradation and different characterization technologies were used to reveal the reactive species. The results showed that a strong synergy existed between MoS2 and Fe(III); approximately 94.3% of the SDZ was removed by MoS2-Fe(III)-PMS after reaction for 30 min, while only 8.5% and 56.4% of the SDZ was removed by Fe(III)-PMS and MoS2-PMS, respectively. Both hydroxyl radicals and sulfate radicals were generated and the latter was the primary species. In addition to the radicals, singlet oxygen was found to be generated and contributed to the degradation of SDZ. The chemical probe reaction with methyl phenyl sulfoxide showed that the generation of high-valent iron-oxo species was not obvious by MoS2-Fe(III)-PMS under both acidic and neutral conditions. MoS2 had good stability. No noticeable deactivation was observed during the 1st to 5th run and no obvious oxidation of surface Mo(IV) occurred. Based on the characterization of catalyst and oxidizing species, a mechanism for the activation of PMS by MoS2-Fe(III) was proposed. The results from this study are expected to clarify the reactive species and deepen the understanding of MoS2-promoted persulfate activation by Fe(II)/Fe(III).

Self-Assembly of Size-Controlled m-Pyridine-Urea Oligomers and Their Biomimetic Chloride Ion Channels.

The m-pyridine urea (mPU) oligomer was constructed by using the intramolecular hydrogen bond formed by the pyridine nitrogen atom and the NH of urea and the intermolecular hydrogen bond of the terminal carbonyl group and the NH of urea. Due to the synergistic effect of hydrogen bonds, mPU oligomer folds and exhibits strong self-assembly behaviour. Affected by folding, mPU oligomer generates a twisted plane, and one of its important features is that the carbonyl group of the urea group orientates outwards from the twisted plane, while the NHs tend to direct inward. This feature is beneficial to NH attraction for electron-rich species. Among them, the trimer self-assembles into helical nanotubes, and can efficiently transport chloride ions. This study provides a novel and efficient strategy for constructing self-assembled biomimetic materials for electron-rich species transmission.

Synthesis and preliminary evaluation of a PET-FI bimodal imaging agent targeting estrogen receptor.

Estrogen receptor is an attractive target for the diagnosis and treatment of breast cancer. This article reports for the first time a dual-modality imaging agent targeting estrogen receptor that can use PET imaging to diagnose breast cancer and utilize fluorescence imaging to achieve intraoperative navigation. Fluorescence experiments show that [natGa] 1 has typical aggregate induced emission characteristics. Above the critical concentration, [natGa] 1 can form biocompatible nanomicelles. [natGa] 1 can quickly light up estrogen receptor positive MCF-7 cells. Cell uptake experiments show that [68Ga] 1 is mediated by estrogen receptor. Therefore, [nat/68Ga] 1 shows the characteristics of highly sensitive diagnosis and visualization of breast cancer, and can be used as a lead compound for the development of a novel PET-FI bimodal imaging agent targeting the estrogen receptor.

Binary mineral sulfides sorbent with wide temperature range for rapid elemental mercury uptake from coal combustion flue gas.

Developing efficient sorbents with rapid kinetics is the main challenge encountered for Hg0 capture from coal combustion flue gas in a sorbent injection scenario. Binary mineral sulfide-based materials combining copper sulfide (CuS) and zinc sulfide (ZnS) to exert their capabilities for Hg0 capture at the low- and high-temperature was for the first time reported for Hg0 removal to realize a wide temperature range sorbents. When the molar ratio between CuS and ZnS was 10%, the as-synthesized 10Cu-Zn nanocomposite exhibited excellent Hg0 uptake rate at 150°C that could degrade 40 µg/m3 of Hg0 to undetectable level at the end of a 60-s experiment with the dosage of only 1 mg. This Hg0 uptake rate is folds higher compared to that when bare CuS or ZnS was adopted alone at this specific temperature. The typical flue gas atmospheres had negligible effect on Hg0 removal over 10Cu-Zn in a short contact time, which further suggests that the binary sorbents were proper to be injected before the electrostatic precipitator system. Moreover, it is found that, by adjusting the ratio between CuS and ZnS, it is potential to develop binary sorbent suiting any temperature conditions that may achieve an exceedingly high Hg0 capture performance. Thus, this work not only justified the candidature of 10Cu-Zn as a promising alternative to traditional activated carbon for Hg0 capture from coal combustion flue gas but also guided the future development of multi-component mineral sulfide-based sorbents for Hg0 pollution remediation from various industrial flue gases.

Surface-Engineered Sponge Decorated with Copper Selenide for Highly Efficient Gas-Phase Mercury Immobilization.

The paramount challenge in design and synthesis of materials for vapor-phase elemental mercury (Hg0) immobilization is to achieve a balance between performance and economy for practical applications. Herein, a newly designed electroless plating coupled with an in situ selenization method was developed to construct a copper selenide (Cu2Se)-functionalized commercial polyurethane sponge (PUS) as an efficient Hg0 trap. Intrinsic features such as easy availability of the raw material, facile preparation, and excellent performance guarantee the Cu2Se/PUS to be applicable in industrial uses. The Cu2Se/PUS exhibits a maximum adsorption capacity (Qm,Cu2Se/PUS) of 25.90 mg·g-1, while this value is 758.80 mg·g-1 when normalized to the Cu2Se coating amount. This value of Qm,Cu2Se is equal to 79.7% of its corresponding theoretical value (Qt,Cu2Se), far exceeding the availability of Cu2Se anchored on other supports. Meanwhile, the Cu2Se/PUS exhibited a quick response for Hg0, with an extremely high uptake rate of 1275.84 µg·g-1·min-1. Even under harsh conditions, the Cu2Se/PUS still immobilizes Hg0 effectively, which is crucial for real-world applications. This work not only provides a promising trap for permanent Hg0 sequestration from industrial sources but also illustrates a versatile platform for the economic fabrication and practical application of advanced functional sponges in diverse environmental remediation.

Toward an Understanding of Fundamentals Governing the Elemental Mercury Sequestration by Metal Chalcogenides.

The lack of fundamental understanding of the chemistry governing elemental mercury (Hg0) immobilization over metal chalcogenides (MChals) is the key challenge impeding the interpretations of Hg0 behaviors in global cycles. This work therefore made the first endeavor toward the establishment of a roadmap capable of describing and depicting Hg0 sequestrations by various MChals. The results suggest that the binding energy between the metal cations and chalcogen anions is a proper descriptor that could predict the immobilization behaviors of Hg0 over zinc chalcogenides (ZnS and ZnSe) that exhibit an identical molecular structure, i.e., the lower the binding energy was, the higher the Hg0 sequestration performance that was obtained. The validity of this descriptor was further demonstrated over a series of MChals sharing structural similarities. A scaling relationship was thus established, which further proved the Hg0 immobilization performance of MChals was generally in reverse proportion to the above-mentioned binding energy. Although there is still a long way toward the proposal of a full roadmap that can predict and depict the Hg0 immobilization behaviors over all MChals, this work marks the first step on this road and provides guides for further studies by understanding the fundamentals governing Hg0 sequestration over MChals with structural similarities.

Sulfate radical-induced destruction of emerging contaminants using traces of cobalt ions as catalysts.

Cobalt is part of vitamin B12, which is essential to maintain human health, and trace levels of cobalt ions are ubiquitous in water and soil environments. In this study, the destruction of 1,4-dioxane (1,4-D) by peroxymonosulfate (PMS) under the catalysis of trace levels of Co2+ was investigated under buffered conditions. The results showed that near 100% removal of 1,4-D was achieved after reaction for 6 and 10 min with 50 and 25 µg/L Co2+, respectively, in the presence of 5 mM phosphate ions. Mechanism studies revealed that radicals mediated the destruction of 1,4-D and sulfate radicals were the primary reactive species. The traces of Co2+ had the greatest reactivity for the catalysis of PMS in neutral environments (pH 7.0). However, pH 5.5 was observed to be the best condition for 1,4-D destruction, which was probably caused by the involvement of phosphate radicals. Common water components including chloride ions and bicarbonate ions were observed to have promoting and inhibiting effects, respectively, on the removal of 1,4-D. To further demonstrate the potential of Co2+-PMS in practical applications, we explored the simultaneous degradation of 20 antibiotics using trace levels of Co2+. The results showed that all the investigated antibiotics, except for lomefloxacin, could be efficiently degraded by Co2+-PMS with removal rates of greater than 97%. The findings from this study demonstrate the promise of using trace levels of cobalt for environmental remediation applications, even when high concentrations of phosphate ions are co-present.

In Situ Decoration of Selenide on Copper Foam for the Efficient Immobilization of Gaseous Elemental Mercury.

Mercury emission from industrial activities is a great threat to public health and ecosystems. Developing new strategies and materials to remove mercury still remains a serious task. Herein, selenide-decorated copper foam prepared by a heating-stirring method (Cu-hs) was used as a monolithic mercury adsorption material. The Cu-hs exhibited much better adsorption of elemental mercury (Hg0) compared with the selenide-decorated cordierite honeycomb prepared by the same method (Cordierite-hs). Nearly 100% Hg0 adsorption efficiency was obtained under a high gaseous hourly space velocity of 6.0 × 104. Excellent Hg0 adsorption capacity was obtained in a wide range of reaction temperatures from 40 to 120 °C, suggesting the good adaptability of Cu-hs in different operating conditions. The Cu-hs exhibited high selectivity for Hg0 against H2O and SO2, which is advantageous for real applications in industrial flue gas. The Hg0 adsorption capacity of Cu-hs reached 3743 g/m3, about 14 times higher than the 243 g/m3 of Cordierite-hs. The excellent Hg0 adsorption performance of Cu-hs was attributed to the high affinity of the selenium in Cu2Se for mercury, the homogeneous distribution of Cu2Se, and the superior fluid characteristics of the Cu foam substrate. The adsorption performance of the spent Cu-hs could be effectively recovered by HCl solution leaching and subsequent reselenization. The utilization of recyclable Cu-hs provides a cost-effective and environmentally friendly method for removing mercury from industrial flue gas.

PET probe with Aggregation Induced Emission characteristics for the specific turn-on of aromatase.

Aromatase is an attractive target for the diagnosis and treatment of breast cancer. To combine the anti-photobleaching properties of Aggregation Induced Emission (AIE) with the high sensitivity and whole-body imaging characteristics of positron emission tomography (PET), we designed a bifunctional complexing agent with AIE characteristics by modifying the structure of tetraphenylethene, which is linked with triazole derivatives capable of complexing with natGa3+/68Ga3+ to obtain [natGa/68Ga] 2 for targeting the aromatase. [natGa] 2 has typical AIE characteristics, which can form uniform nanomicelles above the critical micelle concentration, and illuminate estrogen receptor (+) MCF-7 cells. [natGa] 2 itself is almost nonemissive in PBS buffer solution, but it turns on its fluorescence upon interaction with human aromatase, with a detection limit of 0.15 µg/mL [68Ga] 2 is easy to prepare and has high stability. Compared to the estrogen receptor that is negatively expressed by MDA-MB-231  cells, MCF-7  cells positively expressing estrogen have a higher uptake of [natGa] 2. The distribution of aromatase in a tumor can be co-localized by using [68Ga] 2. These results can be used to effectively assess estrogen receptor status and aromatase levels at the cellular level. We anticipate that this research could provide a new strategy for the fabrication of PET probes with AIE characteristics, providing useful probes for PET- FL (Fluorescence imaging) bimodal imaging.

Amorphous Molybdenum Selenide Nanosheet as an Efficient Trap for the Permanent Sequestration of Vapor-Phase Elemental Mercury.

The key challenge of vapor-phase elemental mercury (Hg0) sequestration is the rational design of a sorbent with abundantly available ligands that exhibit excellent affinity toward Hg0 to simultaneously achieve a high uptake capacity and rapid capture rate. In this work, it is demonstrated how the correct combination of functional ligands and structural properties can form an ideal remediator for permanent Hg0 immobilization. The adsorption capacity of an amorphous molybdenum triselenide (MoSe3) nanosheet greater than 1000 mg g-1 is the highest recorded value compared to previously reported sorbents tested in a fixed-bed reactor. Meanwhile, the uptake rate of 240 µg g-1 min-1 is also the highest recorded rate value. Mercury selenide as formed exhibits extremely low leachability when environmentally exposed. This impressive performance is primarily attributed to the appropriate layer space between the nanosheets that permeated Hg0 and the existence of diselenide (Se2 2-) ligands that exhibit excellent affinity toward Hg0. Thus, this work not only provides a promising trap for permanent Hg0 sequestration from industrial and domestic sources with minimum hazard but also provides a detailed illustration of using structural advantages to obtain an ideal sorbent as well as guidance for the further development of Hg0 decontamination techniques.