Tunable schiff-based networks with different bonding sites for enhanced photocatalytic activity under visible-light irradiation: The effects of steric hindrance.

Organic polymers hold great potential in photocatalysis considering their low cost, structural tailorability, and well-controlled degree of conjugation for efficient electron transfer. Among the polymers, Schiff base networks (SNWs) with high nitrogen content have been noticed. Herein, a series of SNWs is synthesized based on the melamine units and dialdehydes with different bonding sites. The chemical and structural variation caused by steric hindrance as well as the related photoelectric properties of the SNW samples are investigated, along with the application exploration on photocatalytic degradation and energy production. The results demonstrate that only SNW-o based on o-phthalaldehyde responds to visible light, which extends to over 550 nm. SNW-o shows the highest tetracycline degradation rate of 0.02516 min-1, under 60-min visible light irradiation. Moreover, the H2O2 production of SNW-o is 2.14 times higher than that of g-C3N4. The enhanced photocatalytic activity could be ascribed to the enlarged visible light adsorption and intramolecular electron transfer. This study indicates the possibility to regulate the optical and electrical properties of organic photocatalysts on a molecular level, providing an effective strategy for rational supramolecular engineering to the applications of organic materials in photocatalysis.

Manganese-enhanced degradation of lignocellulosic waste by Phanerochaete chrysosporium: evidence of enzyme activity and gene transcription.

Lignolytic fungi initiate lignocellulose decay by producing extracellular oxidative enzymes. For better understanding the enzymatic degradation of lignocellulose by white-rot fungi, we investigated the effect of manganese on the organic matter loss, manganese peroxidase (MnP) activity, and manganese peroxidase gene (mnp) transcription levels during solid-state fermentation of rice straw with Phanerochaete chrysosporium. The results showed that the addition of manganese improved MnP activity and made it reach the peak earlier, promoted fungal growth at the early period (0-9 days), and enhanced the degradation of lignocellulosic waste. The total organic matter loss had a good correlation with fungal biomass during 30 days of cultivation, and manganese amendment promoted the ability of P. chrysosporium to degrade lignocellulose. Quantitative real-time RT-PCR revealed the differential expression of mnp1, mnp2, and mnp3: manganese amendment increased the transcription of mnp1 and mnp2 but not mnp3. The results indicated that manganese stimulated mnp transcription levels and played a post-transcriptional role in MnP production. These findings provide opportunity of development in enzymatic degradation of lignocellulosic waste by P. chrysosporium amended with manganese.

Deciphering the Fenton-reaction-aid lignocellulose degradation pattern by Phanerochaete chrysosporium with ferroferric oxide nanomaterials: Enzyme secretion, straw humification and structural alteration.

Nowadays, Nano-biotechnology is emerging to be one of the most promising tools in environmental remediation. In this study, the degradation efficiency of lignocellulose by white-rot fungi was improved by addition of Fe3O4 nanomaterials (NMs) in solid-state fermentation. The highly-ordered cellulose crystalline was demonstrated to be broken down through infrared spectroscopy (FT-IR) and crystallinity index analysis. The decay of fluorescence intensity presented a lower degree of aromatic polycondensation and less conjugated chromophores in lignocellulose. Mechanistic analysis showed that NMs participated in the Fenton reaction and affected lignocellulose biodegradation process by regulating enzyme secretion. Specifically, the time variation curves of hydroxyl radicals and Fe2+ were discussed to illustrate the degradation pattern. The NMs remained stable after the fermentation and were possible to be recycled for the next cycle. All the results support that the synergism of Fe3O4 NMs and white-rot fungi would be a promising research direction in lignocellulose treatment.

A novel biosorbent prepared by immobilized Bacillus licheniformis for lead removal from wastewater.

Magnetic polyving akohol (PVA) immobilized the endogenous bacterium Bacillus licheniformis with sodium alginate to get a novel biosorbent. The optimum preparation and adsorption conditions were studied. The optimal preparation conditions was the fraction of magnetic PVA was 9%, the fraction of sodium alginate was 0.8%, the fraction of microbial suspensions was 5% and the crosslinking time was 20 h. The best adsorption conditions were listed as follows: pH was 6, the biosorbent dosage was 0.7 g L-1, the initial concentration of lead ions was 200 mg L-1 and the optimal adsorption time was 12 h. The results of SEM and FTIR spectroscopy analysis displayed this novel biosorbents had good structure and the functional groups on the surface was abundant. The VSM analysis confirmed the novel biosorbents had good magnetic magnetization and were easily separated from aqueous medium. Under the optimum conditions, the removal rate of lead ions from waste water could reach 98%, the calculated maximum adsorption capacity could be up to 113.84 mg g-1. The whole adsorption process was well fit by the pseudo-second order kinetic and it was also a Langmuir monolayer adsorption. The desorption experiments showed the biosorbent had good re-usability.

Responses of microbial carbon metabolism and function diversity induced by complex fungal enzymes in lignocellulosic waste composting.

Composting is an economic and effective technology for solid waste treatment, which is an essential method to promote the biogeochemical cycle of contaminants. However, the application of this technology was limited by the bio-degradative recalcitrance of lignin and other kind of phytotoxic substances release. The combination with microorganisms and enzymes is a popular and efficient way to enhanced composting. This study, referring to metabolic mechanisms, fungal molecular and biogeochemical cycles, was performed to investigate the effects of lignin degradation, carbon metabolic diversity, as well as the related changes induced by these two kinds of complex enzymes in composting. The biological diversity is important indicator in ecosystem, which concerns the environmental applicability of one technology. The carbon metabolism diversity reflected the biogeochemical cycles of organic matter, which was also an essential input to analyze the effects of composting. The changes on the diversity characteristics of carbon are essential to comprehensively understand the deep mechanisms of this process, and extended the application of complex enzymes in the field of enhanced composting. The analysis of Biolog revealed that the utilization of pyruvic acid methyl ester, α-Cyclodextrin, d-Mannitol, d-Galacturonic, Itaconic acid and l-asparagine were deeply promoted, and that of d, l-α-Glycerol-phosphate, l-Threonine, Glycyl-l-Glutamic acid and putrescine were depressed by adding the complex enzyme in composting. Moreover, according to the data, the addition of complex enzymes improved the degradation efficiency and the metabolic capacity of carbon in composting. These findings undoubtedly contribute to the development of enzyme-based technologies and the applications of complex enzymes in composting, which is of great benefit to eliminate the limitation and extend the application of composting.

Microplastic pollution in surface sediments of urban water areas in Changsha, China: Abundance, composition, surface textures.

Microplastics pollution in the global marine environment has received much recent research attention. However, microplastics contamination of the freshwater environment has not been fully studied, especially with respect to the surface sediments of urban water areas in China. This study investigated surface sediment samples from twelve selected sites in Changsha, China. The average microplastic concentrations in the surface sediments of the urban water areas ranged from 270.17 ±â€¯48.23 items·kg-1 to 866.59 ±â€¯37.96 items·kg-1, and the highest concentration of microplastics was found in Yuejin Lake sediments. Most of the collected microplastics were transparent, and most were classified as fragments. Most microplastics (58.31%) were smaller than 1 mm across all samples. Raman analysis indicated that polystyrene dominated the sediments samples. This study provided framework for future studies of microplastics pollution in the surface sediment of urban water areas in China.

Growth, metabolism of Phanerochaete chrysosporium and route of lignin degradation in response to cadmium stress in solid-state fermentation.

This study examines the growth, metabolism of Phanerochaete chrysosporium (P. chrysosporium) and route of lignin degradation in response to cadmium (Cd) stress in solid-state fermentation of rice straw. Less living fungi biomass was found under Cd exposure, suggesting that Cd had strong toxicity to P. chrysosporium. The maximum values of lignin peroxidase and manganese peroxidase were 0.34 and 5.21 U g(-1) at the Cd concentration of 32 mg kg(-1), respectively, lower than that in control, which indicated Cd stress would inhibit ligninolytic enzymes. The production of reactive oxygen species (ROS) including hydroxyl radicals (OH), superoxide anion radical (O2(-)) and hydrogen peroxide (H2O2) increased after Cd exposure. Higher concentration of oxalate was detected at high Cd concentrations. Cd stress also had influence on the rates of lignocelluloses degradation and the route of lignin degradation. Partial Cd could be removed by P. chrysosporium.

Application of molecularly imprinted polymers in wastewater treatment: a review.

Molecularly imprinted polymers are synthetic polymers possessing specific cavities designed for target molecules. They are prepared by copolymerization of a cross-linking agent with the complex formed from a template and monomers that have functional groups specifically interacting with the template through covalent or noncovalent bonds. Subsequent removal of the imprint template leaves specific cavities whose shape, size, and functional groups are complementary to the template molecule. Because of their predetermined selectivity, molecularly imprinted polymers (MIPs) can be used as ideal materials in wastewater treatment. Especially, MIP-based composites offer a wide range of potentialities in wastewater treatment. This paper reviews the latest applications of MIPs in wastewater treatment, highlights the development of MIP-based composites in wastewater, and offers suggestions for future success in the field of MIPs.