Catalytic hydrotreatment of humins into cyclic hydrocarbons over solid acid supported metal catalysts in cyclohexane

Humins are common undesirable sideproducts during many acid-catalyzed reactions in renewable biomass platform conversion. However, few studies have been reported to the efficient utilization of humins.For the first time, the selective catalytic conversion of biomass-derived humins into cyclic hydrocarbons with high conversion rate and selectivity is presented using a home-made Ru/W-P-Si-O bifunctional catalyst. The multistage polymerization structure of humins was studied through controlled experiments.Results show that the CAC bond network can be efficiently depolymerized at a mild reaction temperature of 340–380 °C, catalyzed by the cooperative catalysis of nano-Ru particles and porous strong Lewis solid acid. Particularly, 95.4% conversion of humins was achieved under the optimal condition with up to 88.3%yield of cyclic hydrocarbons. The detailed composition after liquefaction was also analyzed. This study paves the way for the efficient production of cyclic and aromatic hydrocarbons from furan-derived humin polymer through Lewis acid-catalyzed Diels–Alder reactions between furan rings.

Yolk-shell structure synergistic defect engineering for boosting electromagnetic wave absorption in Co_(9)S_(8)@Humins-derived carbon

Exploring new strategies to incorporate the concepts of green chemistry and defect engineering into new architectures to address the problem of severe electromagnetic wave(EMW)pollution is challenging.In this work,by using a by-product of catalytic conversion of biomass as a carbon source,we prepare two-dimensional(2D)Co_(9)S_(8)-coated humins-derived carbon nanomaterials with a yolk-shell structure.The EMW attenuation ability is finally optimized by controlling the morphology and defects of the composite material through the pyrolysis temperature.As expected,with the synergy of conductive loss/interfacial polarization and defects regulating,the composite material achieves a reflection loss(RL)value of−51.4 dB in Ku-band and the effective absorption bandwidth(EAB)can be as high as 5.92 GHz(12.08–18.00 GHz)at 1.8 mm ultra-thin coating thickness.A strong absorption capacity in the low-frequency C-band(6.4 GHz)reaches RL value of−49.9 dB and a thickness of 3.50 mm,which grants it the characteristic of convertible microwave absorption from high frequency to low frequency.Taking account of the facile synthesis and tunable absorption properties,the encouraging findings shed light on exploring waste-turned-microwave absorbents with promising practical applications.

Mapping out the reaction network of humin formation at the initial stage of fructose dehydration in water

The formation of humins hampers the large-scale production of 5-hydroxymethylfurfural(HMF)in biorefinery.Here,a detailed reaction network of humin formation at the initial stage of fructose-to-HMF dehydration in water is delineated by combined experimental,spectroscopic,and theoretical studies.Three bimolecular reaction pathways to build up soluble humins are demonstrated.That is,the intermolecular etherification of β-furanose at room temperature initiates the C12 path,whereas the C-C cleavage of a-furanose at 130-150℃ leads to C11 path,and that of open-chain fructose at 180℃ to C11' path.The successive intramolecular dehydrations and condensations of the as-formed bimolecular intermediates lead to three types of soluble humins.We show that the C12 path could be restrained by using HCl or AlCl_(3) catalyst,and both the C12 and C110 paths could be effectively inhibited by adding THF as a co-solvent or accelerating heating rate via microwave heating.

Effects of Fe3+ and Ca2+ on sorption of phenanthrene by Humin in karst soil,Southwest China

Humin(HM) is the main organic matter component to af fect the migration and transformation of polycyclic aromatic hydrocarbons(PAHs) in soil. The study on infl uence of the morphology change of inorganic ions on the adsorption of PAHs in soil and its organic matter is still rare at microscopic scale. In this paper, yellow soil humin(YS-HM) and lime soil humin(LS-HM) were chosen as samples, then Fe^(3+) and Ca^(2+) were added into samples to facilitate the precipitation by changing the existing conditions of ions, and the mechanism by which inorganic precipitation changed adsorption capacity of karst soil was analyzed from the microscopic scale. The results showed that the adsorption capacity of HM reduced with the inorganic precipitation increasing. The precipitation of Ca^(2+)and Fe^(3+) both reduced the adsorption capacity of YS-HM and LS-HM by 61.71% and 71.83% on average, respectively. The results of scanning electron microscope-energy dispersive spectrometry(SEM-EDS) and pore analysis showed that the HM porosity decreased after formation of Ca^(2+) and Fe^(3+) precipitation. According to the value of Freundlich parameter n, it may be because the precipitation or colloid of Ca^(2+) and Fe^(3+) fi lled micropores and covers high-energy adsorption sites of the HM. This research provides theoretical support for studying the PAHs migration and bioavailability of Calcium-rich in karst soil.

Carbon Sequestration in Soil Humic Substances Under Long-Term Fertilization in a Wheat-Maize System from North China

The changes in humic substances （HS） is fundamental in detecting soil carbon sequestration mechanisms in natural and cultivated environments. Based on a long-term trial, the amounts of water dissolved substances （WSS）, humic acid （HA）, fulvic acid （FA） and humin （HU） were determined to explore the impact of long-term fertilization on HS. Increases in the amounts of WSS, HA, FA and HU were significant different among the treatments with manure. A significant correlation was found between the increased soil organic carbon （SOC） and HS （R^2=0.98, P〈0.01）. The change in the E4/E6 ratio was significantly correlated with the increased SOC （R2=0.88, P〈0.01）, HA （R^2=0.91, P〈0.01）, FA （R^2=0.91, P〈0.01） and HU （R^2=0.88, P〈0.01）. The cluster was mainly divided into two parts as manure fertilization and inorganic fertilization, based on the increases in HA, FA and HU. These results suggest that long term fertilization with manure favours carbon sequestration in HS and is mainly stabilized as HU, while the HA becomes more aliphatic. We conclude that increases in SOC can be linked to changes in the molecular characteristics of HS fractions under long term fertilization.

Adsorption mechanism of Cd(Ⅱ)by calcium‑modifed lignite‑derived humin in aqueous solutions

Lignite-derived humin(CHM)was extracted from raw coal in Heihe City,China,producing calcium-modifed lignite-derived humin(Ca-CHM)by Ca(OH)_(2).The physical and chemical performances of CHM and Ca-CHM were analyzed with SEM,^(13)C spectra and XPS techniques.The results show that Ca-CHM exhibited weaker aliphatic,more aromatic polar compared with CHM,which improves the adsorption capacity for Cd(Ⅱ).XPS analysis indicates that Ca(Ⅱ)has been loaded onto Ca-CHM successfully after modifcation.This batch adsorption experiments report the adsorption performance of CHM and Ca-CHM for Cd(Ⅱ).The adsorption process of CHM and Ca-CHM for Cd(Ⅱ)conform to pseudo-second-order model,which is chemical adsorption,and the adsorption data presented good fts to the Langmuir model.The maximum adsorption amount(Q_(m))of Cd(Ⅱ)onto CHM and Ca-CHM by the Langmuir model is 15.29 mg/g and 41.84 mg/g,respectively.Based on the results of SEM,^(13)C spectra,and XPS analysis,we concluded that the main adsorption mechanism of Ca-CHM on Cd(Ⅱ)was ion exchange of Cd(Ⅱ)for Ca(Ⅱ),static-adsorbed and surface complexation.Therefore,Ca(Ⅱ)can be loaded on the surface of Ca-CHM by chemical modifcation,improving the adsorption capacity of materials in aqueous solutions.

Humic substances:Structure,function and benefits for agroecosystems—a review

The increasing global demand for food production,often causing excessive use of chemical fertilizers,has led to the deterioration of soil health.Immediate action is required to restore soil health in a sustainable manner.This review advocates switching to use of organic matter(manure and compost)that contains vital nutrients for plant growth and helps restore soil health.Humic substances(HSs),derived from degraded plant remains and found ubiquitously in nature,are an important source of organic matter.The application of HSs to soil enhances essential nutrient supply and assimilation of atmospheric CO_(2)due to increasing biomass yield.Promoting HS application globally can help lower atmospheric CO_(2)concentrations and create a sustainable agricultural practice.However,the process of humification and the molecular structure of HSs remain poorly understood subjects in soil science.Therefore,it is imperative to understand the mechanisms underlying various roles of HSs in agroecosystems.This review offers an insight into the various structural and functional aspects of HSs,particularly fulvic acid and humic acid.The dynamic and interactive nature of HSs creates a framework for sustainable agriculture.

中国东部森林土壤腐殖碳组分纬度格局及其影响因素（英文）

Soil humic carbon is an important component of soil organic carbon （SOC） in ter- restrial ecosystems. However, no study to date has investigated its geographical patterns and the main factors that influence it at a large scale, despite the fact that it is critical for exploring the influence of climate change on soil C storage and turnover. We measured levels of SOC, humic acid carbon （HAC）, fulvic acid carbon （FAC）, humin carbon （HUC）, and extractable humus carbon （HEC） in the 0-10 cm soil layer in nine typical forests along the 3800-km North-South Transect of Eastern China （NSTEC） to elucidate the latitudinal patterns of soil humic carbon fractions and their main influencing factors. SOC, HAC, FAC, HUC, and HEC increased with increasing latitude （all P〈0.001）, and exhibited a general trend of tropical 〈 subtropical 〈 temperate. The ratios of humic C fractions to SOC were 9.48%-12.27% （HAC）, 20.68%-29.31% （FAC）, and 59.37%-61.38% （HUC）. Climate, soil texture, and soil microbes jointly explained more than 90% of the latitudinal variation in SOC, HAC, FAC, HEC, and HUC and interactive effects were important. These findings elucidate latitudinal patterns of soil humic C fractions in forests at a large scale, and may improve models of soil C turnover and storage.

Experimental and molecular dynamic simulation study of perfluorooctane sulfonate adsorption on soil and sediment components

Soil and sediment play a crucial role in the fate and transport of perfiuorooctane sulfonate （PFOS） in the environment. However, the molecular mechanisms of major soil/sediment components on PFOS adsorption remain unclear. This study experimentally isolated three major components in soil/sediment： humin/kerogen, humic/fulvic acid （HA/FA）, and inorganic component after removing organics, and explored their contributions to PFOS adsorption using batch adsorption experiments and molecular dynamic simulations. The results suggest that the humin/kerogen component dominated the PFOS adsorption due to its aliphatic features where hydrophobic effect and phase transfer are the primary adsorption mechanism. Compared with the humin/kerogen, the HA/FA component contributed less to the PFOS adsorption because of its hydrophilic and polar characteristics. The electrostatic repulsion between the polar groups of HA/FA and PFOS anions was attributable to the reduced PFOS adsorption. When the soil organic matter was extracted, the inorganic component also plays a non-negligible role because PFOS molecules might form surface complexes on SiO2 surface. The findings obtained in this study illustrate the contribution of organic matters in soils and sediments to PFOS adsorption and provided new perspective to understanding the adsorption process of PFOS on micro-interface in the environment.

Reliability of radiocarbon dating on various fractions of loess-soil sequence for Dadiwan section in the western Chinese Loess Plateau

The accurate radiocarbon dating of loess-soil sequences plays an essential role in the reconstruction of the environmental and climatic changes in continental settings during the last glaciation and Holocene. However, our knowledge about the reliability of radiocarbon ages of various fractions of soil and loess samples is still insufficient. Here, we present our study results on radio- carbon ages based on bulk organic matter, humin fraction, and carbonate of samples collected from a loess-paleosol section in the western Chinese Loess Plateau. We compare these observations with the optically stimulated luminescence ages and charcoal radiocarbon ages to evaluate the reliability of these fractions. We observed that the radio- carbon ages of humin fraction are very close to those of charcoal and are consistent with the optically stimulated luminescence ages within the experimental errors. We observed a significant deviation in the radiocarbon ages of carbonate and bulk organic matter from those of charcoal and optically stimulated luminescence ages, likely due to the dilution of these fractions during the pedogenetic process. Our results reveal that, except for charcoal, the humin fraction may yield reliable laC ages for the Chinese loess-soil sequence.