At present, there are various wound dressings that can protect the wound from further injury or isolate the external environment in wound treatment. Whereas, infection and slow self-healing still ...exist in wound healing process. Therefore, it is urgent to develop an ideal wound dressing with good biocompatibility and strong antibacterial activity to promote wound healing. Bacterial cellulose is a kind of promising biopolymer because it can control wound exudate and provide a moist environment for wound healing. However, the lack of antibacterial activity limits its application. In this paper, the advantages of bacterial cellulose as wound dressings were introduced, and the preparation and research progress of bacterial cellulose-based antibacterial composites in recent years were reviewed, including adding antibiotics, combining with inorganic antibacterial agents or organic antibacterial agents. Finally, the existing problems and future development direction of bacterial cellulose-based antibacterial wound dressings were discussed.
There is limited study focusing on the bioaccumulation of heavy metals in vegetables and human exposure to bioaccessible heavy metals in soil. In the present study, heavy metal concentrations (Cr, ...Ni, Cu, Pb and Cd) were measured in five types of vegetables, soil, root, and settled air particle samples from two sites (at a domestic waste incinerator and at 20km away from the incinerator) in Guangzhou, South China. Heavy metal concentrations in soil were greater than those in aerial parts of vegetables and roots, which indicated that vegetables bioaccumulated low amount of heavy metals from soil. The similar pattern of heavy metal (Cr, Cd) was found in the settled air particle samples and aerial parts of vegetables from two sites, which may suggest that foliar uptake may be an important pathway of heavy metal from the environment to vegetables. The highest levels of heavy metals were found in leaf lettuce (125.52μg/g, dry weight) and bitter lettuce (71.2μg/g) for sites A and B, respectively, followed by bitter lettuce and leaf lettuce for sites A and B, respectively. Swamp morning glory accumulated the lowest amount of heavy metals (81.02μg/g for site A and 53.2μg/g for site B) at both sites. The bioaccessibility of heavy metals in soil ranged from Cr (2%) to Cu (71.78%). Risk assessment showed that Cd and Pb in soil samples resulted in the highest non-cancer risk and Cd would result in unacceptable cancer risk for children and risk. The non-dietary intake of soil was the most important exposure pathway, when the bioaccessibility of heavy metals was taken into account.
Aiming at the ecological footprint model, the traditional trade adjustment method only considered the international trade process at the urban scale, ignoring the trade footprint generated by ...domestic trade and indirect trade in various products. This paper adopts the urban-scale ecological footprint model based on the macro-trade adjustment method to calculate the trade adjustment coefficient of biological products and the energy trade adjustment coefficient respectively to correct the trade footprint. The results showed that the per capita ecological deficit showed a straight upward trend, from 0.07351 hm
in 2013 to 0.15472 hm
in 2018. From 2013 to 2018, the per capita ecological footprint of Guangdong Province was greater than the per capita ecological carrying capacity, and the ecological economic system of Guangdong Province was in an unsustainable state. According to the trade ecological footprint, Guangdong Province was a completely foreign resource and service exporting city, which was consistent with Guangdong Province's own economic development direction; the analysis results of the ecological product trade footprint were more consistent with the current city positioning of biological resource products of each city, and the energy indirect trade footprint. The improved ecological footprint model could more accurately assess the true status of ecological vitality above the urban scale.
The application of porous carbon microspheres derived from pure biomass in supercapacitors is restricted due to their limited reactive groups. MXene owns a combination of redox Faradic surface with ...good metallic conductivity and hydrophilicity, which assists to obtain high pseudocapacitance and energy density. Herein, Ti3C2Tx MXene was introduced to chitosan-based porous carbon microsphere (CPCM) to fabricated sandwich-like structure (CPCM/MXene) through electrostatic interaction. The Ti3C2Tx protected the spherical structure of CPCM. Meanwhile, CPCM hindered the reaggregation of Ti3C2Tx by inserting in the Ti3C2Tx layers, promoting the electrolyte migration kinetics. The synergistic effect endowed CPCM/MXene high specific capacitance of 362 F/g at current density of 0.5 A/g and acceptable cycling stability with 93.87% capacitance retention at a high current density of 10 A/g after 10,000 cycles. Furthermore, CPCM/MXene displayed a high energy density of 27.8 W/(h•kg) at 500.0 W/kg of power density. These satisfactory performances prove that combining Ti3C2Tx MXene nanosheets with porous carbon microspheres is a considering method to construct a new generation electrode material of supercapacitor.
•The cross-linking chitosan/rectorite nano-hybrid composite resins were prepared.•The adsorption of the resins was investigated in single and binary metal systems.•The adsorption capacity of the ...resins followed the order of Cu(II)>Cd(II)>Ni(II).•EDTA desorbed metals from resins better than HCl.•Coordination bonds were formed between metals and the nitrogen atoms of resins.
Chitosan/rectorie (CTS/REC) nano-hybrid composite microsphere was prepared by changing the proportion of CTS/REC with 2:1, 3:1 and 4:1. Compared with the pure cross-linking chitosan microsphere, the nano-hybrid composite microsphere was proved to have better sorption capacity of Cd(II), Cu(II) and Ni(II), especially 2:1(CTS/REC-1). The adsorption behavior of the microsphere of Cd(II), Cu(II) and Ni(II) was investigated in single and binary metal systems. In single system, the equilibrium studies showed that the adsorption of Cd(II), Cu(II) and Ni(II) followed the Langmuir model and the pseudo-second-order kinetic model. The negative values of (ΔG) suggested that the adsorption process was spontaneous. In binary system, the combined action of the metals was found to be antagonistic and the metal sorption followed the order of Cu(II)>Cd(II)>Ni(II). The regeneration studies indicated that EDTA desorbed Cd(II), Cu(II) and Ni(II) from cross-linking microspheres better than HCl. The FT-IR and XPS spectra showed that coordination bonds were formed between Cd(II), Cu(II) and Ni(II) and the nitrogen atoms of cross-linking CTS/REC nano-hybrid composite microspheres.
For the high-valued utilization of hemicelluloses and for realizing the controllable synthesis of NPs, this paper's aim is to combine xylan, chitosan and nanometal materials at the same time. In this ...research study, firstly, propargyl xylan was synthesized via nucleophilic substitution reaction between xylan and propargyl bromide in NaOH solution. On the other hand, a tosyl group was introduced onto the 6th position of synthesized quaternized chitosan (QCS), and the azide group replaced the tosyl group to obtain 6-amido-QCS (QCS-N
). The synthesis conditions of the above reactions were optimized. Subsequently, the novel xylan-click-QCS polymer was obtained via click reaction between terminal alkyne groups on the xylan chains and azide groups on QCS. Then, AgNPs and AuNPs were synthesized by adopting the xylan-click-QCS polymer as the reducing and stabilizing agent, and the reaction conditions were optimized to obtain well-dispersed and highly stable nanoparticles. There were two kinds of Ag nanomaterials, with diameters of 10~20 nm and 2~5 nm, respectively, indicating the formation of Ag nanoclusters, except for Ag nanoparticles, in this reaction. The diameter of the synthesized AuNPs was 20~30 nm, which possessed a more uniform size distribution. The Ag nanoclusters with a smaller size (2~5 nm) could inhibit MCF-7 cell proliferation effectively, indicating their application potential in cancer therapy. The study gives a new approach to the high-value utilization of biopolymers.
The persistence of antibiotics in sewage treatment plants in recent years has become a serious problem. Meanwhile, humic acid and ammonia nitrogen are widely distributed in natural reservoirs and ...might influence the sorption, migration and transformation of antibiotics. In this study, natural zeolite (NZ) was evaluated as an adsorbent for the removal of levofloxacin (LEV). The physical and chemical properties of NZ before and after adsorption were characterized by various analytical techniques to develop the mechanism. The effects of ammonia nitrogen and humic acid (HA) on the interfacial behavior of LEV on NZ were explored. Comparative experiments revealed that LEV adsorption on NZ involved electrostatic interactions and ion exchange, and the adsorption processes were well fitted by the Langmuir isotherm model and pseudosecond-order kinetic model. The maximum experimental adsorption capacity of LEV was 22.17 mg·g
at pH 6.5. The presence of ammonia nitrogen and HA significantly suppressed the adsorption of LEV due to competitive adsorption, and the adsorption capacity decreased 58 and 46%, respectively. It is obvious that low concentrations of ammonia nitrogen and HA are conducive to improving the treatment effect of sewage. This study demonstrates that NZ is a promising and efficient material for LEV adsorption.
As the largest output and export province of ceramic tiles in China, Guangdong has been faced with the contradictory problem that the ceramic tile industry brings both huge economic benefits and ...adverse environmental impacts. To promote energy conservation and emission reduction in the ceramic tile industry, the activity of “Cleaner Production Auditing for a Thousand Voluntary Industrial Enterprises” has been held since 2010 in Guangdong. This study presents a comprehensive application of cleaner production in a typical medium-scale ceramic tile plant, which has initially taken part in the cleaner production activity. On the basis of pre-auditing conducted in the selected plant, key auditing procedures and main objectives were determined. After the analysis of material balance and energy efficiency in key auditing procedures, 31 different measures, including facility replacement, technology improvement, process control, raw material and waste reutilization, plant management, and worker training, have been proposed and implemented in a feasible way. Through the cleaner production application, the plant achieved the expected objectives and obtained obvious progress in energy conservation and emission reduction. For each unit product, the consumption of energy and water were cut down by 4.3% and 22.33%, respectively. The SO2 emission per unit product was also reduced by 8% after the cleaner production. Although the cleaner production is a continuous process in this case, it provides a theoretical and practical basis for the sustainable development of other ceramic tile production enterprises.
► Powder preparation step and sintering step consumed most of the resources. ► Material balance analysis was used for developing cleaner production measures. ► 31 measures were suggested in six aspects and implemented in different schedule. ► Water consumption per unit product reduced by 22.3% after cleaner production. ► Comprehensive energy consumption per unit product was cut down by 4.3%.
Rectorite is a kind of layered silicate, with the structure and characteristic much like those of montmorillonite. It is a regularly interstratified clay mineral with alternate pairs of dioctahedral ...mica-like layers (nonexpansible) and dioctahedral montmorillonite-like layers (expansible) in a 1:1 ratio. Chitosan/organic rectorite (chitosan/OREC) nanocomposite films with different mass ratios of chitosan to organic rectorite and corresponding drug-loaded films were successfully obtained by a casting/solvent evaporation method. The structures of the films were evaluated by FTIR-ATR, XRD and SEM. A wide variety of material characteristics for the chitosan/OREC nanocomposite films were investigated, including the water resistance, mechanical property, optical transmittance, anti-ultraviolet capacity and bactericidal activity. The characteristics of the nanocomposite films were related to the amount and the interlayer distance of OREC in them.
In vitro drug-controlled release studies showed a slower and more continuous release for the nanocomposite films in comparison with pure chitosan film, and the drug-delivery cumulative release was proportional to the amount and the interlayer distance of OREC. The chitosan/OREC nanocomposites films provide promising applications as antimicrobial agents, water-barrier compounds, anti-ultraviolet compounds, and drug-controlled release carriers in antimicrobial food packaging and drug-delivery system.
The transcriptomic response of green microalga
Chlorella sorokiniana
exposure to environmentally relevant concentration of cadmium(II) (Cd) and 4-
n
-nonylphenol (4-
n
-NP) was compared in the ...present study. Cd and 4-
n
-NP exposure showed a similar pattern of dys-regulated pathways. The photosystem was affected due to suppression of chlorophyll biosynthesis via down-regulation of Mg-protoporphyrin IX chelatase subunit ChlD (CHLD) and divinyl chlorophyllide a 8-vinyl-reductase (DVR) in Cd group and via down-regulation of DVR in 4-
n
-NP group. Furthermore, the reactive oxygen species (ROS) could be induced through down-regulation of solanesyl diphosphate synthase 1 (SPS1) and homogentisate phytyltransferase (HPT) in Cd group and via down-regulation of HPT in 4-
n
-NP group. Additionally, Cd and 4-
n
-NP would both cause the dys-regulation of carbohydrate metabolism and protein synthesis. On the other hand, there are some different responses or detoxification mechanism of
C. sorokiniana
to 4-
n
-NP stress compared to Cd exposure. The increased ROS would cause the DNA damage and protein destruction in Cd exposure group. Simultaneously, the RNA transcription was dys-regulated and a series of changes in gene expressions were observed. This included lipid metabolism, protein modification, and DNA repair, which involved in response of
C. sorokiniana
to Cd stress or detoxification of Cd. For 4-
n
-NP exposure, no effect on lipid metabolism and DNA repair was observed. The nucleotide metabolism including pyrimidine metabolism and purine metabolism was significantly up-regulated in the 4-
n
-NP exposure group, but not in the Cd exposure group. In addition, 4-
n
-NP would induce the ubiquitin-mediated proteolysis and proteasomal degradation to diminish the misfolded protein caused by ROS and down-regulation of heat shocking protein 40. In sum, the Cd and 4-
n
-NP could cause the same toxicological effects via the common pathways and possess similar detoxification mechanism. They also showed different responses in nucleotide metabolism, lipid metabolism, and DNA repair.
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