An efficient and mild recycling of waste melamine formaldehyde foams by alkaline hydrolysis

Melamine formaldehyde foam(MFF)generates many poisonous chemicals through the traditional recycling methods for organic resin wastes.Herein,a high MFF degradation ratio of ca.97 wt.%was achieved under the mild conditions(160℃)in a NaOH–H2O system with ammelide and ammeline as the main degradation products.The alkaline solvent had an obvious corrosion effect for MFF,as indicated by scanning electron microscopy(SEM).The reaction process and products distribution were studied by Fourier-transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),and ^(13)C nuclear magnetic resonance(NMR).Besides,the MFF degradation products that have the similar chemical structures and bonding performances to those of melamine can be directly used as the raw material for synthesis of melamine urea-formaldehyde resins(MUFs).Moreover,the degradation system demonstrated here showed the high degradation efficiency after reusing for 7 times.The degradation process generated few harmful pollutants and no pre-or post-treatments were required,which proves its feasibility in the safe removal or recovery of waste MFF.

Qualitative analysis of aromatic compounds via 1D TOCSY techniques

The aromatic compounds,including o-xylene,m-xylene,p-xylene,and ethylbenzene,primarily originate from the catalytic reforming of crude oil,and have a wide variety of applications.However,because of similar physical and chemical properties,these compounds are difficult to be identified by gas chromatography(GC)without standard samples.With the development of modern nuclear magnetic resonance(NMR)techniques,NMR has emerged as a powerful and efficient tool for the rapid analysis of complex and crude mixtures without purification.In this study,the parameters of one-dimensional(1D)total correlation spectroscopy(TOCSY)NMR techniques,including 1D selective gradient TOCSY and 1D chemicalshift-selective filtration(CSSF)with TOCSY,were optimized to obtain comprehensive molecular structure information.The results indicate that the overlapped signals in NMR spectra of nonpolar aromatic compounds(including o-xylene,m-xylene,p-xylene and ethylbenzene),polar aromatic compounds(benzyl alcohol,benzaldehyde,benzoic acid),and aromatic compounds with additional conjugated bonds(styrene)can be resolved in 1D TOCSY.More importantly,full molecular structures can be clearly distinguished by setting appropriate mixing time in 1D TOCSY.This approach simplifies the NMR spectra,provides structural information of entire molecules,and can be applied for the analysis of other structural isomers.

生物质基酸性低共熔溶剂用于高效溶解木质素及溶解机理

设计能高效溶解木质素的溶剂对木质素的高值化利用具有重要意义。本文中设计了基于氯化胆碱、甜菜碱和左旋肉碱作为氢键受体(HBA)和四种氢键供体(HBD)的生物质衍生的酸性低共熔溶剂(DESs),可以溶解包括碱木质素(AL)、脱碱木质素(DAL)、酶解木质素(EHL)和硫酸盐木质素(KL)在内的不同类型的木质素。在大多数所设计的DESs中,EHL比AL、KL和DAL更容易溶解,而不同木质素中羟基的含量对木质素的溶解有显著影响,但是并非在所有DESs中木质素的溶解情况都符合上述规则。氯化胆碱是构建DESs的首选HBA,具有良好的性能并适应于不同类型木质素的溶解,而合适的酸度使苯甲酸和没食子酸乙酯成为对木质素溶解有利的HBDs。研究表明能有效溶解木质素的DESs应具有强的氢键酸度(α值>0.95)以及与溶解的木质素匹配的合适极性。此外,HBD的pKa值和DESs的酸度也是评价酸性DESs溶解木质素性能的有效指标。通常具有适中pKa值的HBDs能够用于构建具有高效的木质素溶解性能的DESs。DESs的粘度对木质素溶解也有一定影响,较低的粘度有助于木质素溶解。

Progress in the study of algae and mosses in biological soil crusts

Algae and mosses are not only two of the familiar communities in the process of desert vegetational succession,but also have the highest biomass in biological soil crusts.Meanwhile,being the pioneer plants,algae and mosses are involved in the establishment of biological soil crusts,which have great importance in arid environments and play a major role in desert ecosystems,such as being the indicator of the vegetation type,soil-holding,preventing erosion by water and wind,and sand fixation.This paper reviews the advances in the study of algae and mosses in arid and semi-arid areas.It mainly describes the ecological functions of algae and mosses including their influences on water cycle,circulation of substances,and community succession.In addition,the relationships between algae and mosses are discussed.Finally,some suggestions are proposed for the research orientations of algae and mosses in biological soil crusts.Ecologically,algae and mosses have significant ecological importance in arid areas,especially in those areas where environmental problems are becoming increasingly serious.

Chlorophytes of biological soil crusts in Gurbantunggut Desert,Xinjiang Autonomous Region,China

In this paper,chlorophytes collected from 253 biological soil crust samples in Gurbantunggut Desert in Xinjiang Autonomous Region,China were studied by field investigation and microscopical observation in lab.The flora composition,ecological distribution of chlorophytes in the desert and dynamic changes of species composition of chlorophytes in different developing stages of biological soil crusts are preliminarily analyzed.Results showed that there were 26 species belonging to 14 genera and 10 families,in which unicellular chlorophytes were dominant.There existed some differences in distribution of varied sand dune positions.The taxa of chlorophytes in leeward of sand dunes are most abundant,but the taxa in windward,interdune and the top of sand dunes reduced gradually.Chlorophytes were mainly distributed within the crust and the taxa of chlorophytes decrease obviously under the crust.In the devel-oping stages of the biological soil crust,species diversity of chlorophytes changed a little,but species composition pre-sented some differences.Chlorococcum humicola,Chlorella vulgaris,Chlamydomonas ovalis and Chlamydomonas sp.nearly existed in all developing stages of biological crusts.In several former stages of the biological soil crust there were spherical chlorophytes and filamentous ones.When moss crust formed,filamentous chlorophytes disappeared,such as Microspora and Ulothrix.

Assessment of Hebei flora against the IUCN Red List Criteria in China

Some plants of Hebei Province in China are under threat from human activities,such as over-herding and over-exploitation of wild medicinal plants and industrial plants,etc.To identify the plants in danger in the province and to inspect the quality of the environment encompassing Beijing and Tianjin,a red list of the threatened flora of Hebei Province was produced by using the IUCN Red List Criteria(version 3.1)and its guidelines(version 6.2).Some 262 species were assessed and the results were as follows:(1)the threatened flora include 211 species,accounting for 7.95%of the total native vascular plants.Among them,44 are Critically Endangered,80 Endangered and 87 Vulnerable;(2)the destruction of the habitat caused by human activities and the actual or potential exploitation of the plants themselves were the main threat factors of Hebei flora;(3)most of the threatened plants are located in the western,northern and northeastern mountainous regions,namely the key regions of Hebei plant diversity;the endemic and regionally endemic species are severely threatened.Consequently,the assessment not only presented the threatened status of Hebei flora but also indicated the relatively fragile health status of the environment of Beijing and Tianjin.Thus,it is suggested that the application of the IUCN Red List Criteria at the regional level,as an index,could reflect the health status of the local ecosystem.In addition,more concrete measures are needed to conserve the plant diversity and the natural ecosystem of Hebei Province and even the whole region encompassing Beijing and Tianjin.