Firstly, this review introduced the research background and application status of bio-based hydrogels. According to the different crosslinking mechanisms, physical and chemical hydrogels were classified and described. Then, the hydrogels prepared from cellulose, chitosan, protein and other bio-based materials were summarized based on the classification of the used biomass, including the solvents system of cellulose, the preparation of cellulose-based hydrogels and modification of cellulose derivatization. Also, the feedstock sources and modification methods of chitosan-based hydrogels, as well as cross-linking mechanisms such as electrostatic interaction and imine bond formed by amine groups on their molecular chains were assembled. Protein-based hydrogels with good biocompatibility and bioactivity, formed by β-folded self-assembly of polypeptide chains were depicted as well in this review. Similarly, bio-based hydrogels prepared by using physical or chemical crosslinking of hydrophilic natural polymers such as starch, sodium alginate and carrageenan, were introduced respectively. At the same time, the main applications of functionalized bio-based hydrogels in the biomedical fields were described in detail, including drug sustained release, targeted delivery, cell media, tissue repair scaffolds, wound dressings, etc. In addition, the application and research progress of bio-based hydrogels as adsorbent materials in environmental field were reviewed, and their applications in packaging, sensing, photoelectric catalysis and other fields were also highlighted. Finally, the development opportunities and challenges of bio-based hydrogels were summarized, and the future research directions were prospected.
Stimulus-responsive hydrogels, as a new class of functional polymer materials, can actively sense the difference of the external environment and reflect the change to the outside world by specific ways such as swelling or contraction, and show a great application potential in many fields of life and production. As a renewable natural resources, biomass has been widely applied in the preparation of stimulus-responsive hydrogels in recent years. Particularlly for rapid development of engineering technology and applications, including controllable/active polymerization and click chemistry, dynamic covalent bond, supramolecular self-assembly and super molecular aggregation state regulatory molecules, etc, is able to overcome the instrisic structure defects of biomass macromolecule to a certain extent, and fabricate the stimulus-responsive hydrogels containing unique molecular structure of biomass raw materials, which promoted the development of new green synthesis strategies, multi-functional technology, simple modular synthesis technology, modern biotechnology and other technologies. Based on the stimulus-responsive methods and types of stimulus-responsive hydrogels, this paper assembles six types of hydrogels, including temperature response, acid-base response, light response, electric response, magnetic response and multiple response and highlights the effect of the unique molecular structure of biomass raw materials on the performance of the stimulus-responsive hydrogels. Also, the applications of biomass-based hydrogels with different environmental responses in the fields of drug controlled release, biological tissue engineering, biosensors, adsorption materials, cell culture and antibacterial materials were summarized, and the future development direction of biomass-based hydrogels was prospected.
Tannic acid(TA) is a kind of multi hydroxyl aromatic biomass. The thermal properties of TA were analyzed by thermogravimetric experiment, the carbonization process of TA was observed by muffle furnace heating experiment, the apparent activation energy was observed by KAS and Ozawa method, and the most probable function was determined by Satava method. Thermogravimetric analysis showed that TA entered the state of rapid weight loss at about 182 ℃; when the temperature reached 800 ℃, the carbon residue of TA in nitrogen atmosphere was 15.29%. In air atmosphere, the carbon residue was 1.97% due to the second rapid weight loss in the temperature range of 436-538 ℃. It was found in the macro carbonization experiment that TA would form an expanded carbon layer when heated. Among them, a hollow carbon layer appeared at 100-200 ℃, and a solid carbon layer was formed at 300-400 ℃, which had obvious expansion, integrity, compactness and good gloss. It had the potential to become a new carbon source in intumescent flame retardants. The results of thermal decomposition kinetics showed that the apparent activation energy of thermal decomposition of TA in nitrogen atmosphere was 494 kJ/mol, lgA was 111.32, and the most probable mechanism function of rapid weight loss stage was G(α)=[-ln(1-α)]1/n, n=0.105 3, and its thermal decomposition mechanism belonged to random nucleation and subsequent nucleation growth reaction.
Pretreatment was a key step in sugar platform -based biomass refinery using lignocellulosic biomass as raw material. In this paper, the advantages and disadvantages of the commonly used methods such as dilute acid/alkali, steam explosion, liquid hot water, microwave, subcritical CO2, ionic liquids, deep-eutectic solvents, organosolv, milling/grinding, and biological, and the research progress of subsequent enzymatic hydrolysis and fermentation were reviewed. Furthermore, the application of the co-production of ethanol and platform chemicals in the pretreatment of biomass feedstock at home and abroad based on Aspen Plus and techno-economic analysis were introduced. Finally, the drawbacks of Aspen Plus in biomass pretreatment for ethanol production were summarized and the further research directions were proposed.
N and P co-doped carbon aerogels(NPCA) were prepared from cattail inflorescence with NH4H2PO4 as dopant by pretreatment with acidic sodium chlorite, ultrasonic cell fragmentation, freeze-drying and carbonization at high temperature. The surface morphology, pore structure, crystalline structure and surface chemical composition of NPCA were characterized by SEM, N2 adsorption/desorption, XRD and XPS. The effects of doping amounts and carbonization temperatures on the electrochemical properties of NPCA were systematically studied. The results of research showed that NPCA was a three-dimensional network structure that composed of amorphous carbon. The nitrogen element on the surface of NPCA existed in the form of pyridine nitrogen(N-6), pyrrole nitrogen(N-5), graphitization nitrogen(N-Q) and oxidation state of nitrogen(N-X), and the phosphorus element existed in the form of P—O and P—C. The pore structure and surface chemical structure of NPCA were greatly affected by doping amount of NH4H2PO4 and carbonization temperature. The optimum preparation conditions of NPAC were that the mass ratio of cattail-based cellulose to ammonium dihydrogen phosphate was 1∶2 and the carbonization temperature was 800 ℃. The NPAC-2-800 prepared under this condition has rich pore structure and surface functional groups. Furthermore, the specific surface area was 599.88 m2/g, the total pore volume was 0.27 cm3/g, the micropore volume was 0.20 cm3/g, and the average pore size was 3.69 nm, the N and P contents of NPCA were 5.69% and 5.12%, respectively. The electrochemical properties of the NPCA were measured by three electrode system in 6 mol/L KOH solution. The specific capacitance of NPCA-2-800 was 249 F/g at a current density of 1 A/g, which was 133.4% higher than that of the undoped sample(106.7 F/g), and had good rate performance.
In recent years, levulinic acid has been considered as a key biobased platform compound and attracted wide attention, which can be utilized in the synthesis of many high value-added chemicals. Among them, levulinates, as a class of important chemical products, can be used in alternative fuels, edible spices, plasticizers and other fields, especially as alternative fuels, which provides a feasible reference scheme for sustainable development. In this paper, the recent research progress on the catalytic synthesis of levulinates in the field of biomass conversion was reviewed. The reaction performances and related mechanisms were introduced involving in several approaches, such as the esterification of levulinic acid, the alcoholysis of furfuryl alcohol, the conversion of monosaccharides and cellulosic materials, respectively. The synthesis of levulinates was summarized and prospected.
The modified coconut shell activated carbons were prepared by loading CuCl2, carbonization and CO2 activation. The Cu-loaded activated carbons were labeled as AC3, AC4, AC5, and AC7 to represent the mass fractions of cupric salt solutions 0.3%, 0.4%, 0.5% and 0.7%, respectively. The Cu-loaded activated carbons were characterized by means of N2 adsorption isotherm, SEM, XRD and XPS. Their dynamic adsorption-desorption performance was measured by the gravimetric method. After modification, the acidic oxygenated groups on the surface of activated carbon decreased. The results showed that cupric salt existed in two forms, i.e., CuO and Cu2O. It was found that the presence of Cu loading led to the decreasing of surface area and pore volume of modified sample, and the increasing of the surface area and proportion of micropore. AC5 showed the largest values of the surface area(733.20 m2/g) and proportion(72.99%) of micropore. Furthermore, AC5 had the optimal equilibrium adsorption capacity(356.40 mg/g) which increased by 33.38% compared to the raw sample, and the optimal equilibrium adsorption time(118.80 min) which increased by 33.38%. Moreover, the adsorption performance of AC5 was better than the activated carbons in the organic gas filter cartridge(3M-3301 CN and 3M-6001 CN). After five cycles of adsorbents regeneration test, 80% of adsorption capability was still able to be reserved. The Cu-loaded activated carbons improved the adsorption performance by transforming the style from physical adsorption to physical-chemical adsorption through complexation of π-bonds in benzene with hollow d-orbitals in Cu2+.
In order to promote the development of biomass gasification technology and the utilization of gasification products, the development and industrial status of biomass gasification technology, gasifier type and its development status at home and abroad were mainly introduced, and the advantages and disadvantages of biomass gasification technology were analyzed. At the same time, it is also found that China's biomass resources had great potential and biomass energy had the excellent characteristics of renewability, such as renewable, less pollution, large reserves, wide distribution, zero carbon emissions and so on. However, it was difficult to internationalize because of a series of problems such as imperfect of collection-storage-transportation system, shortage of capital chain and more by-products. It was further prospected that biomass gasification in China should not only take a basic research, but also consider the overall demand of biomass gasification technology and the competition with other technologies as the future development direction and important key point. This paper was expected to lay a solid foundation for the further development of biomass gasification technology and the high-value utilization of gasification products.
In order to explore the antioxidant activity of cinnamon polysaccharides, the protein was removed from the water extract of cinnamon(CE)to obtain crude polysaccharides. By using cellulose ion column DE-52 and propylene dextran gel S-300, the cinnamon neutral polysaccharides(CNP) was obtained. The relative molecular mass(Mr) of CNP was determined by gel permeation chromatography(GPC), and the monosaccharide component of CNP were determined by pre-column derivatization high performance liquid chromatography. The connection modes of its monosaccharides were determined by methylation method and nuclear magnetic resonance method. The in vitro chemical model was used to study the scavenging effects of CNP on DPPH· and ABTS+·. The results indicated that the weight average relative molecular mass(Mw) of CNP was 3 630 and the main monosaccharide was glucose. Three kinds of connection modes of monosaccharides were 1, 4, 5-Ac3-2, 3, 6-Me3-Glu, 1, 5-Ac2-2, 3, 4, 6-Me4-Glu, and 1, 5, 6-Ac3-2, 3, 4-Me3-Glu. The determination results of free radicals scavenging by CNP showed that when the mass concentration of CNP was 2 g/L, the DPPH· scavenging rate reached the maximum of 84%, the ABTS+· scavenging rate reached 60%. Although the free radical scavenging rate of CNP was lower than that of Vc, the DPPH· scavenging effect was comparable to that of Vc when the concentration of CNP reached 0.5 g/L. Therefore, the antioxidant activity of cinnamon neutral polysaccharide was good and had good development value.
Compounds methyl (Z)-6-((4-(5-(2-(3, 5-bis(trifluoromethyl)phenyl)-2-cyanovinyl)thiophen-2-yl) phen-yl)(4-methoxyphenyl)amino)-7-isopropyl-1, 4a-dimethyl-1, 2, 3, 4, 4a, 9, 10, 10a-octahydrophenanthrene-1-carboxylate(2) and dimethyl 6, 6'-(((1-cyanoethene-1, 2-diyl)bis(thiophene-5, 2-diyl))bis(4, 1-phenylene))bis((4-methoxyphen-yl)azanediyl))(E)-bis(7-isopropyl-1, 4a-dimethyl-1, 2, 3, 4, 4a, 9, 10, 10a-octahydrophenanthrene-1-carboxylate)(3) were obtained simply by mixing 5-(dehydroabietic acid triarylamine)-thiophene-2-carbaldehyde and 3, 5-bis(trifluoromethyl)phenylacetonitrile at room temperature and 100 ℃, respectively. The UV-Vis absorption spectra, fluorescence emission spectra, solvatochromism effect, aggregation-induced emission(AIE) characteristics, thermal stability and electrochemical performance of compounds are studied, and the relationship between their structure and performance is further studied through theoretical calculations. Compared with triarylamine-based acrylonitrile compounds, after introducing the dehydroabietic acid skeleton, the compounds show a larger stokes shift and longer red light emission in the solid state. 2 exhibits AIE characteristics, while 3 does not have AIE characteristics. Both of the two compounds have good thermal stability and morphological stability. 2 and 3 have higher highest occupied molecular orbital(HOMO), lowest unoccupied molecular orbital(LUMO) energy levels and narrow band gap, due to the introduction of dehydroabietic acid skeleton.
The hydrolysis of 5-chloromethyl furfural(CMF) in pure water or water/acetone system to 5-hydroxymethyl furfural(HMF) was studied. The effects of hydrolysis reaction conditions(such as solvent system, alkali neutralizer, temperature and CMF addition amount) on the hydrolysis of CMF were investigated, and the kinetics of the hydrolysis reaction was analyzed. The results showed that the water/acetone system is helpful to reduce the side reaction of HMF, and the addition of sodium disulfite(Na2S2O4) could further prevent the generation of humus. The optimal hydrolysis conditions are as follows: 1 g CMF was added with 0.35 g CaCO3 in a mixture of 10 mL water/acetone with volume ratio of 1∶4, and incubated at 353.15 K for 28 min. Under these conditions, the CMF conversion rate was 97%, the yield of HMF was 85%, and the yield of by-product levulinic acid(LA) was 6%. The separation rate of HMF increased from 50% to 86% with the addition of Na2S2O4. The kinetic study results showed that the activation energy of CMF hydrolysis was 12.3 kJ/mol and the hydrolysis rate constant k1=5.56exp(-1.23×104/RT) in water/acetone system.
Blue luminescent carbon quantum dots(B-CQDs) were synthesized by a simple one-step hydrothermal method using lignin and m-phenylenediamine as precursors. Green luminescent carbon quantum dots(G-CQDs) were synthesized by nitric acid oxidation. The optical properties and structures characteristics of these two CQDs were characterized by UV absorption spectroscopy, fluorescence spectroscopy, TEM, FT-IR and XPS. The cytotoxicity and cell imaging properties of G-CQDs were also tested. The results showed that nitric acid played an important role in the synthesis of G-CQDs. The oxidation of nitric acid increased the graphite N content, deepened the graphitization, passivated the surface state, and red-shifted the fluorescence emission wavelength. The results of structural characterization showed that the prepared B-CQDs and G-CQDs were mainly composed of C, N and O elements. All of them had abundant hydrophilic groups such as —OH, —NH, C—O and —COOH on the surface, which were monodisperse in water with the average particle size were 1.3 nm and 2.5 nm, respectively. The results of optical property analysis showed that the excitation wavelengths of B-CQDs and G-CQDs were Ex=392 nm and Ex=446 nm, and the corresponding emission wavelengths were 488 nm and 514 nm, respectively. They exhibited excitation-dependent fluorescence emission behavior and excitation-independent emission behavior, respectively. The results revealed that the possible emission mechanism of G-CQDs belonged to the bandgap fluorescence emissions based on conjugated π-domains. The synthesized G-CQDs with excellent photoluminescence, stable fluorescence and low cytotoxicity could be applied to bioimaging of HeLa cells.
The antibacterial effects of cinnamon essential oil and cinnamaldehyde on bacteria(Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa) and fungi(Candida albicans) were compared by filter paper method, minimum inhibitory concentration(MIC) and minimum bactericidal concentration(MBC). The antioxidant activities of cinnamon essential oil and cinnamaldehyde were compared by ABTS+· scavenging ability and ferric reducing antioxidant power(FRAP), as well as their antityrosinase activities were compared. The results showed that the two research subjects showed different sensitivities to the inhibitory effects of the five tested strains, and both had the best inhibitory effect on C. albicans. According to the results of MIC and MBC, cinnamic essential oil and cinnamaldehyde had different inhibitory effects on the tested strains, among which the inhibitory effects of cinnamaldehyde on S. aureus, C. albicans and P. aeruginosa were obviously better than those of cinnamon essential oil. The antioxidant activity of cinnamic essential oil was better than that of cinnamaldehyde. The ABTS+· scavenging rate(94.1%) of 16 g/L cinnamic essential oil was 3 times that of the same concentration of cinnamic aldehyde. The FRAP value(1 502 μmol/L) was 5.8 times that of cinnamaldehyde at the same concentration. Both cinnamon essential oil and cinnamon aldehyde could significantly inhibit tyrosinase activity. The IC50 of cinnamon essential oil to tyrosinase was 4.02 g/L, while the IC50 of cinnamaldehyde to tyrosinase was less than 1.25 g/L.
Acetic acid lignin(AAL) was fractionated by dissolution in aqueous solution of acetic acid with various mass fraction. Four fractions with different relative molecular weight, which were chosen from the fractionation products, were sulfomethylated to obtain products with different relative molecular weight and sulfonic group content. The sulfomethylated lignin(SML) was added into myclobutanil as a pesticide dispersant to get a 40% myclobutanil wettable powder(WP). The influence of relative molecular weight and sulfonic group content on the application performance of 40% myclobutanil wettable powder was investigated. The results indicated that the suspension rate of myclobutanil increased from 72.68% to 83.69% and the wetting time increased from 45 s to 62 s when the average molecular weight increased from 5 768 to 13 964. The suspension rate of myclobutanil increased from 73.56% to 84.86% and the wetting time decreased from 72 s to 57 s when the sulfonic group increased from 0.51 mmol/g to 1.78 mmol/g. The average particle size of the dispersed phase of a 40% myclobutanil WP decreased when the relative molecular weight and sulfonic group content increased. However, too high relative molecular weight resulted in a decrease of the suspension rate of myclobutanil.
Focusing on alkali-treated bagasse, the effects of solid-liquid mixing methods, addition of three kinds of deep eutectic solvents(DES), feed method of fed-batch feeding, and the addition of xylanase on the enzymatic hydrolysis efficiency at high solid loading were investigated. The results showed that magnetic stirring could accelerate enzymatic hydrolysis speed, but had little effect on the efficiency of enzymatic hydrolysis. Negligible effect on enzymatic hydrolysis was observed by addition of low-concentration DES. A fed-batch with initial substrate loading of 150 g/L was fed at 12 and 36 h, respectively, which resulted in a total solid loading of 350 g/L for enzymatic hydrolysis. After enzymatic hydrolysis for 96 h, the total sugar concentration reached 162.7 g/L with the conversion rates of approximately 51% of both cellulose and hemicellulose. On the basis of fed-batch feeding, 1 000 IU/g hemicellulase was added, and the enzyme cocktail was used for enzymatic hydrolysis for 96 h. The total sugar concentration reached 218.9 g/L, and the conversion rate of cellulose and hemicellulose were 72% and 63%, respectively, which were 40% and 22% higher than those without the addition of hemicellulase.
Based on mechanical force effect, graphite nanosheets/bamboo charcoal(GN/BC) composites with excellent electrochemical performance were prepared by high-energy ball milling and pulverization, and high-temperature carbonization using bamboo charcoal and flake graphite as raw materials. Meanwhile, the high-temperature porous bamboo charcoal(PBC) prepared without flake graphite was used as the control sample under the same conditions. The surface morphology and structure of the material were characterized by X-ray diffraction(XRD), Raman spectroscopy(Raman), scanning electron microscope(SEM) and specific surface area and pore distribution analyzer. The electrochemical performance of the product was tested by a three-electrode system. The results showed that the addition of flake graphite with higher crystallinity could improve the crystallinity of the composites. High-energy ball milling could break the graphite flakes into nanostructures and embed them in the bamboo charcoal. The specific surface area of the prepared GN/BC was 863.47 m2/g, the total pore volume was 0.56 cm3/g, the micropore volume was 0.26 cm3/g, and the average pore diameter was 2.58 nm. At a current density of 1A/g, the composite material had a high specific capacitance of 280.97 F/g and good rate performance.
China was rich in forest resources, and it was an important direction and approach of the development of forestry industry for exploiting the active components of forest resources which were beneficial to human health. With the rapid development of forestry bio-agent industry based on the active components as important material basis in China, targeted molecular imprinting materials have important industrial application value in the accurate separation and high-value processing of forest active components. This article introduced the principle and classification of targeted molecular imprinting technology, as well as the carrier types of several new-style targeted molecularly imprinted adsorption materials in recent years, mainly include graphene, silica, carbon dots and bio-based carriers. It focused on the application status in the separation of flavonoids, polyphenols, alkaloids, organic acids and other forest source active ingredients by targeted molecularly imprinted adsorption materials. Finally, the development of targeted molecular imprinting materials for the separation of active components from forest sources was summarized and prospected, the limitation of targeted molecular imprinting materials and the development trend of targeted molecular imprinting materials in the separation of active components from forest sources were also analyzed.
Gum rosin derived methacrylate(GRGMA) was firstly synthesized by the esterification reaction between gum rosin(GR) and glycidyl methacrylate(GMA). Subsequently, atom transfer radical polymerization(ATRP) was applied to fabricate ethyl cellulose-gum rosin-fatty acid derived co-polymer(EC-R-LMA). The structure and properties of GRGMA and EC-R-LMA were then characterized by FT-IR, 1H NMR, DSC, TG/DTG, universal tensile machine and contact angle measurement. It was found that the monomer conversion was higher than 90%. With the increase of the molar ratio of GRGMA from 10% to 70%, the Tg of EC-R-LMA increased from -61.3 ℃ to 62.58 ℃. Particularly, when the molar ratio of GRGMA increased from 30% to 35%, the tensile strength at break increased from 0.41 MPa to 0.50 MPa, whereas the tensile strength at break of the cross-linking polymer(BMI-EC-R-LMA) increased to 1.04 and 1.27 MPa respectively after cross-linking. It was also observed that when the molar ratio of GRGMA and LMA was set to 1∶9 and 2∶8, the Tg of EC-R-LMAs were -61.3 ℃ and -52.9 ℃, respectively, which could be used as a pressure-sensitive adhesive(PSA). Notably, GRGMA acted as a new type of hard monomer for the PSA rather than as a tackifying resin. While the molar content of GRGMA increased from 10% to 20%, the 180° peel strength of PSA increased from 0.56 N/cm to 1.08 N/cm, and the shear resistance property increased from 2 h to more than 72 h.
A rosin-based anionic surfactant with azobenzene group named sodium 4-maleopimaric acid ethyl ester azophenol(E-MPA-AZO-Na) was synthesized through D-A addition, amidation, diazotization, coupling reaction, esterification, and acid-base neutralization using rosin as raw material. Its structure was characterized by FT-IR and NMR. The surface activities and foam properties were investigated by surface tension method, Nile red(NR) fluorescence probe method and polarizing microscope. The results showed that the critical micelles concentration(Ccmc) of surfactant E-MPA-AZO-Na was only 0.035 mmol/L, the surface tension at the Ccmc(λcmc) was 47.11 mN/m, and the minimum area per molecule(amin) was 1.35 nm2, which meant that E-MPA-AZO-Na possesses excellent surface activities. Stable foams could be stabilized when the concentrations of E-MPA-AZO-Na were 0.375, 0.750 and 1.500 mmol/L. Better foaming abilities, smaller foam size and more stable foam emerged with increasing E-MPA-AZO-Na concentration. What's more, the half-life time of the foams formed at 0.375, 0.750 and 1.500 mmol/L were 1 292, 1 770 and 2 534 min, respectively, indicated that E-MPA-Azo-Na possessed outstanding foam stability.
By using different activated carbons as adsorbents, the effects of pore size distribution and surface properties on the adsorption capacity of activated carbon for lubricant wear elements were studied, which based on the analysis of activated carbon by basic properties, specific surface area and pore structure, FT-IR, XPS and surface functional group analysis. The results showed that the mesopore volume and the contents of carboxyl and hydroxyl groups of activated carbon were the key factors affecting the adsorption capacity. Moreover, the adsorption effect of activated carbon on wear elements in simulated oil continuously increased with the increasing of the mesopore volume and the content of carboxyl and hydroxyl groups. Among the six kinds of activated carbons, AC4 with a mesopore volume of 0.901 cm3/g and a total carboxyl and hydroxyl group contents of 0.929 2 mmol/g, exhibited the best wear elements removal performances. Under the optimal adsorption conditions of temperature 80 ℃, adsorption time 60 min and additive amount of activated carbon 5%, the removal rates of Fe, Cu, Pb and Al in the simulated lubricant by AC4 were more than 95%. The removal effect of wear elements by activated carbon was significantly better than that of sawdust, activated clay, silica gel and filter paper, indicating that activated carbon could be used as an excellent adsorbent for waste lubricating oil regeneration and the high-performance material of oil filter.
By changing the solvent system and pretreatment conditions, a series of studies were carried out on the electricity generation performance of the four types of lignin (enzymatic hydrolysis lignin(EHL), alkaki lignin(AL), sodium ligninsulfonate(SL) and furfural residue(FR))in direct biomass fuel cells. The UV spectrum, FT-IR spectrum and 1H NMR spectrum before and after the reaction of alkali lignin were analyzed. The results showed that the alkali lignin exhibited the best power generation performance, the open circuit voltage(OCV) could reach 392.7 mV, and the peak power density(PPD) was 0.198 W/m2. And lignin had the best power generation performance in NaOH solution. Water bath heating pretreatment could improve the power generation performance of lignin. The higher the temperature and the longer the treatment time, the better the power generation performance of the lignin would be. When lignin was irradiated with ultraviolet light, the electricity production performance increased first and then decreased with the passage of time. The electricity production performance was the best when it was treated for 24 hours. The OCV could be increased to 431.2 mV, and PPD was increased to 0.371 W/m2. After the oxidation reaction in the fuel cell, the benzene ring structure of lignin had been destroyed to a certain extent, and the hydroxyl group on the benzene ring had been oxidized to a carbonyl structure. The UV absorption peak of alkali lignin produced red-shift and color enhancement effects. And in the FT-IR spectrum, the carbonyl absorption peak was enhanced. Especially, the signals of aromatic protons, phenolic hydroxyl groups and aliphatic hydroxyl groups were weakened in 1H NMR spectrum.
Bagasse-based phosphorus-doped activated carbon(PAC-900) was prepared with bagasse as carbon source, phytic acid as phosphorus source and activator, and used as electrode for the electrosorption of Cu2+. The pore structure, surface chemical properties and elemental composition of the samples were characterized by nitrogen adsorption-desorption isotherm, XPS and SEM-EDX. The research results showed that when the initial concentration of Cu2+ was 100 mg/L, the electrosorption of Cu2+ by PAC-900 was as high as 86.85 mg/g, which was much higher than 35.15 mg/g of undoped activated carbon(C-900). After 10 times of desorption, the adsorption capacity could still reach 45.38 mg/g. The activation of phytic acid could produce the activated carbon with the specific surface area as high as 1 671.75 m2/g, and the total pore volume and micropore volume of 1.33 cm3/g and 0.09 cm3/g, respectively, which could significantly improve its electrochemical performance and hydrophilicity. The adsorption process was mainly affected by the electric double layers adsorption and Faraday adsorption. The adsorption isotherm and adsorption kinetic process analysis showed that the adsorption process conformed to the Freundich isotherm and pseudo-second-order kinetic process, it indicated that there was not only single-layer adsorption but also multi-layer adsorption in the adsorption process; XPS and SEM-EDX analysis results showed that the P element mainly existed in the form of C—P—O, C—O—P and C—P＝O, and C—P was very rare, among which C—P=O contributed the most to the Faradaic adsorption of Cu2+.
The filter paper was used as raw material to prepare cellulose nanocrystals(CNCs) and gold nanoparticles(GNPs) were prepared by sodium citrate reduction method. Subsequently, CNCs/GNPs composite iridescence was prepared by blending GNPs and CNCs at different mass ratios, following by adding fructose to the above system in order to study the influence of fructose on the plasmon absorption resonance effect. Then, the composite films were analyzed by transmission electron microscopy(TEM), reflection spectroscopy, scanning electron microscopy(SEM), polarized light microscopy, infrared spectroscopy, X-ray diffraction(XRD), ultraviolet-visible(UV) spectroscopy and circular dichroism(CD). The results showed that CNCs have self-assembled during the film formation process and formed a left-handed chiral layered liquid crystal structure; the composite film had obvious iridescent color, periodic layered structure and fingerprint texture. The addition of GNPs did not change the CNCs itself, but the composite membrane had obvious plasmon resonance absorption peak and blue-shifted. Moreover, the addition of fructose could make the color of the film red-shifted and promote the more uniform dispersion of GNPs, thereby enhancing the plasmon resonance absorption effect of GNPs. Particularly, the addition of GNPs and fructose did not change the crystal structure of CNCs, nor did it affect the crystallinity of cellulose.
Semi-terminated isocyanate epoxy itaconate resin modified by silicone(IPDIHSiIE) was synthesized by graft copolymerization of polysiloxane modified epoxy itaconate resin(SiIE) that was prepared from the reaction between hydroterminated polysiloxane modified epoxy itaconic acid ester resin and half-terminated isocyanate. The chemical structure of IPDIHSiIE was characterized by FT-IR and 1H NMR. Effects of the amount of polysiloxane on the physical and chemical properties of the modified resin and the film were investigated. The results showed that the reaction between polysiloxane and epoxy itaconate resin was completed at 90 ℃ for 8 h, indicating that the target product could be successfully prepared by silicohydride addition. With the increase of the amount of polysiloxane, the particle size of the modified resin dispersion gradually increased, the storage stability became worse, and the gel first risen and then fell. When the content of polysiloxane was 5%, the Z-mean particle size of aqueous dispersion was 129.8 nm, the aqueous dispersion was translucent and had no obvious change after storage for one month. Meanwhile, the gel rate reached the maximum of 93.1%. The hydrophobic property of the modified film was improved with the increase of polysiloxane content, and the film had good thermal stability. With the increase of polysiloxane content, the pencil hardness and flexibility of the film were improved, the adhesion decreased slightly and the glass transition temperature decreased gradually.
The effects of acid hydrotrope(p-toluenesulfonic acid(p-TsOH)) on the fractionation of bamboo residues, and the preparation of monosaccharides, lignin nanoparticles and furfural were investigated. The physicochemical structure variations of bamboo residues before and after the pretreatment were analyzed using scanning electron microscopy(SEM), X-ray diffraction(XRD) and infrared spectroscopy(FT-IR), and the lignin nanoparticles were analyzed by transmission electron microscopy(TEM). Under the conditions of p-TsOH mass fraction of 55%, temperature of 90 ℃ and pretreatment time of 120 min, the results showed that the removal rates of xylan and lignin were 82.72% and 82.16% respectively, while the retention rate of cellulose was as high as 87.3%.The glucose yield was 96.4% after 72 h enzymatic hydrolysis. After pretreatment, the spent liquor was diluted by slowly adding water to precipitate the lignin nanoparticles(with an average particle size of 69.33 nm). The liquid after lignin precipitation was concentrated by vacuum evaporation. Furfural was then prepared by subjecting the concentrated liquid to a reactor at 170℃ for 5 min, and the yield of furfural was 78.5%. The results of mass balance demonstrated that 1 000 g dried bamboo residues could produce 426.6 g of fermentable sugars(including 390.9 g glucose and 35.7 g xylose), 217.1 g lignin nanoparticles and 85.4 g furfural.
Lignin-based phenolic resin(LPF)with high phenol substitution rate(≥70%) were synthesized based on alkali lignin(UL)from black liquor of kraft pulping of spruce, or based on demethylated lignin(DUL) and hydroxymethylated lignin(HUL) obtained from the modification of UL. The effects of the hydroxyl content of three types of lignin on the adhesive strength and free formaldehyde content of LPF adhesives were compared and analyzed in this paper. The results of structure analysis of lignin showed that the hydroxyl ratios of DUL and HUL increased by 26.41% and 72.35%, respectively, while compared to raw UL. UL, DUL and HUL were separately used to replace phenol for the preparation of LPF that were applied in the bonding experiment of poplar veneer. The experimental results showed that demethylation of UL could further improve the heat-resistant water-based bonding strength((σHWT). At 30% lignin substitution rate, DUL showed the largest σHWT of 1.09 MPa, which was 39.39% higher than PF(0.78 MPa). The replacement rate of lignin increased from 30% to 70%. Meanwhile, the content of free formaldehyde in plywood decreased from 0.33 mg/L to 0.29 mg/L, which was still less than the requirement of national standard GB 9846.2—2004(< 0.5 mg/L). The bonding strength of LPF prepared from HUL was significantly improved after modification of UL by hydroxymethylation. At 30% lignin replacement rate, the dry bonding strength(σdry) and wet bonding strength(σWST) were 2.55 MPa and 1.99 MPa which increased by 79.02% and 135.31% respectively, while compared those with PF(1.43 MPa and 0.84 MPa).
Using bamboo as raw material, the effect of formaldehyde/1, 4-dioxane pretreatment on the yield of enzymatic hydrolysis sugar from bamboo cellulose was studied. The producing process of lactic acid through fermentation with the enzymatic hydrolysate was also investigated. The results showed that the pretreatment could remove lignin and greatly increase the cellulose content of the pretreated bamboo substrate, with cellulose content reaching 75.6%-90.7%. The highest yield of cellulose-to-glucose by enzymatic hydrolysis after pretreatment was 92.8%. The enzymatic hydrolysate could be directly used for fermentation to produce lactic acid, and the yield of the glucose to lactic acid could reach 73.2%. The changes of bamboo structure before and after pretreatment were observed by scanning electron microscope(SEM), X-ray diffraction(XRD) and ion chromatograph. After pretreatment, the bamboo surface curled, the wax layer on the surface of bamboo was almost completely dissolved and removed, and the structure became loose.
Cellulose acetate nanofibers(CANFs)were prepared by electrospinning cellulose acetate(CA), followed by deacetylation to obtain cellulose nanofibers(CNFs). Subsequentially, in-situ polymerization of polypyrrole was perform to fabricate the conductive composite nanofibers(CNFs-PPy), which was combined with cellulose paper as a flexible substrate for assembling a flexible pressure sensor. The materials were characterized by FT-IR, XRD and SEM, and the mechanical and sensing performance of the devices were analyzed using a universal material testing machine and an electrochemical workstation. The results showed that polypyrrole was successfully coated on the surface of cellulose nanofibers, and the nitrogen content of composite nanofiber was 24.8%. The current-voltage curves of the sensor maintained a good linear relationship under 1-15 kPa pressure load, and the relative current change rate increased with increasing pressure. The sensitivity values of the sensor were up to 1.77 kPa-1 in the range of low pressure(0-0.99 kPa), 0.43 kPa-1 in the range of medium pressure(1.00-8.33 kPa) and 0.22 kPa-1 in high pressure(8.53-15 kPa), respectively. The sensor had excellent signal reliability and stability, i.e., the sensing signal remained stable after 3 000 cycles of loading. The sensor could realize the real-time monitoring of external pressure changes such as finger touch, which provided a new insights into the development of green electronics.
The methanol extract of the pink flowers of Bauhinia variegata L. was isolated and purified by chromatography on Sephadex LH-20, MCI gel CHP 20P and Toyopearl Butyl-650C were used to isolate and purify, a total of 14 compounds were obtained. The structures of the compounds were identified by NMR spectroscopy, and their tyrosinase inhibitory activities were screened by the method of tyrosinase-catalyzed levodopa oxidation rate. Fourteen compounds isolated and purified from the pink flowers of B. variegata, were identified as pyrocatechol(1), protocatechuic acid(2), phydroybenzoic acid(3), 2, 5-dihydroxy methyl phenylacetate(4), trans-p-coumaric acid(5), cis-p-coumaric acid(6), caffeic acid(7), ethyl caffeic acid(8), trans ferulic acid(9), guaiacol β-D-glucopyranoside(10), p-hydroxybenzoic acid glucose ester(11), (E)-2, 3-dihydroxycyclopentyl-3-(3′, 4′-dihydroxyphenyl) acrylate(12), chlorogenic acid(13), and isoorientin(14) by spectral analysis and comparison with literature data. Compounds 5, 6, 9, 10, 11, 12, 14 were obtained from this plant for the first time. The results of tyrosinase inhibition activity test showed that, compounds 2 and 7 showed relatively good tyrosinase inhibitory activity with IC50 values of (4.804±0.939) g/L and (7.339±0.549) g/L, respectively. Their inhibitory activity increased with the increase of compound concentration, showing a positive dose-effect relationship.
Using acid-rich oil as raw materials, the acid value was reduced by esterification with glycerol in the absence of a catalyst. The optimum conditions were obtained as follows: the mole ratio of glycerol to fatty acid was 1.2∶1, the reaction temperature was 240 ℃, and the acid value could be reduced to below 1.66 mg/g for 2 h. The results showed that this process could not only achieve the purpose of fast deacidification within two hours, but also directly produce biodiesel through transesterification. FT-IR analysis confirmed the disappearance of carboxylic acid and the formation of triglyceride. The results of GPC analysis showed that the composition of the oil after deacidification was 21.93% triglyceride, 37.93% diglyceride and 40.14% diglyceride. And the obtained biodiesel was relatively pure fatty acid methyl esters. In addition, the improvement of the process also directly completed the "process roadmap of biodiesel production from oils with different acid values", which had a certain reference value for the development of biodiesel industry.