Utilization of nano-gold tracing technique: Study the adsorption and transmission of laccase in mediator-involved enzymatic degradation of lignin during solid-state fermentation

Removal of mercury(II) from contaminated water by gold-functionalised Fe3O4 magnetic nanoparticles

Fe₃O₄ nanoparticles were prepared by co-precipitation of Fe²⁺ and Fe³⁺ and then modified with Au to produce an effective adsorbent (Fe₃O₄/Au) for aqueous Hg(II) in contaminated water. Rietveld refinement on the XRD pattern confirmed that the Fe₃O₄/Au was synthesised. Mössbauer spectra exhibited broad and asymmetric resonance lines with two sextets which can be assigned to tetrahedral Fe³⁺; and octahedral Fe³⁺/Fe²⁺. The quantitative analysis of magnetite confirms that the sample shows around 3 wt.% Au and 97 wt.% partially oxidised Fe₃O₄. High surface area: 121 m² g^-1, average pore sizes: 6.3 nm and pore volume: 1.64 cm³ g^-1. The kinetics data were better fitted with a pseudo-second-order and Dubinin-Radushkevich isotherm suggests the Hg(II) adsorption onto Fe₃O₄/Au nanoparticles was mainly by chemical adsorption forming complex with the Au metal immobilised on Fe₃O₄ surfaces. Adsorption capacity of 79.59 mg g^-1. Ionic strength and co-existing ions had a slight influence on the adsorption capacity.

Immobilized laccase on bentonite-derived mesoporous materials for removal of tetracycline

Bentonite is a natural and environmentally clay mineral, and bentonite-derived mesoporous materials (BDMMs) were obtained conveniently from the alkali and acid treatment of bentonite. In the present study, BDMMs were explored for immobilization of laccase obtained from Trametes versicolor. As a result, bentonite-derived mesoporous materials-Laccase (BDMMs-Lac) was developed for the removal of tetracycline (TC). The enzyme immobilization process was carried out through physical adsorption contact (ion exchange adsorption, hydrogen bond adsorption, and Van der waals adsorption) between the BDMMs and laccase. The process of immobilization remarkably increased its operating temperature. The BDMMs-Lac exhibited over 60% removal efficiency for TC within 3 h in the presence of 1-hydroxybenzotriazole (HBT). In conclusion, BDMMs-Lac showed more promising potential than free laccase for practical continuous applications.

Synthetic strategies and application of gold-based nanocatalysts for nitroaromatics reduction

With the increasing requirement of efficient organic transformations on the basic concept of Green Sustainable Chemistry, the development of highly efficient catalytic reaction system is greatly desired. In this case, gold (Au)-based nanocatalysts are promising candidates for catalytic reaction, especially for the reduction of nitroaromatics. They have attracted wide attention and well developed in the application of nitroaromatics reduction because of the unique properties compared with that of other conventional metal-based catalysts. With this respect, this review proposes recent trends in the application of Au nanocatalysts for efficient reduction process of nitroaromatics. Some typical approaches are compared and discussed to guide the synthesis of highly efficient Au nanocatalysts. The mechanism on the use of H₂ and NaBH₄ solution as the source of hydrogen is compared, and that proposed under light irradiation is discussed. The high and unique catalytic activity of some carriers, such as oxides and carbons-based materials, based on different sizes, structures, and shapes of supported Au nanocatalysts for nitroaromatics reduction are described. The catalytic performance of Au combining with other metal nanoparticles by alloy or doping, like multi-metal nanoparticles system, is further discussed. Finally, a short discussion is introduced to compare the catalysis with other metallic nanocatalysts.

Molecular docking simulation on the interactions of laccase from Trametes versicolor with nonylphenol and octylphenol isomers

The biodegradation of nonylphenol (NP) and octylphenol (OP) isomers by laccase has attracted increasing concerns. However, the interaction mechanism between these isomers and laccase remains unclear, especially for fungal laccase. In this work, molecular docking was employed to study this issue. The results indicated that the structural characteristic of alkyl chain (position and branching degree) affected the interactions between Trametes versicolor (T. versicolor) laccase and isomers. The binding affinity between them was closely related to the position and branching degree of alkyl chain in isomers. The binding affinities between linear isomers and T. versicolor laccase were para-position < meta-position < ortho-position. For selected branched 4-NP, the isomers with bulky α-substituent in alkyl chain had higher binding affinities. In addition, hydrophobic contacts between T. versicolor laccase and NP or OP isomers were necessary, while H-bonds were optional. The isomers with similar structure may have more common residues involved in hydrophobic contacts. The H-bonds of selected NPs and OPs were all connected with phenolic hydroxyl. These findings provide an insight into detailed interaction mechanism between T. versicolor laccase and isomers of NP and OP. It is helpful to broaden the knowledge of degradation technology of NPs and OPs and provide theoretical basis on biological remediation of these contaminants.

Efficacy of carbonaceous nanocomposites for sorbing ionizable antibiotic sulfamethazine from aqueous solution

This paper investigated the key factors and mechanisms of sulfamethazine (SMT) sorption on a novel carbonaceous nanocomposite, and the effects of harsh aging on SMT sorption in the presence and absence of soil and before as well as after aging. The carbonaceous nanocomposites were synthesized by dip-coating straw biomass in carboxyl functionalized multi-walled carbon nanotubes solution and then pyrolyzed at 300 °C and 600 °C in the absence of air. The sorption performance of high temperature carbonaceous nanocomposite on SMT was excellent, as measured sorption distribution coefficient in the order of 10(3)-10(5.5) L kg(-1). Carbonaceous nanocomposites were aged either alone or mixed with soil via exposure to nutrients and soil extract (biological aging) or 80 °C for 100 d (chemical aging). No obvious effects of harsh aging on SMT sorption were observed in the presence of soil and/or biological and chemical aging. The primary mechanisms for SMT sorption included partition caused by Van der Waals forces and adsorption caused by hydrogen bonding and π-π electron-donor-acceptor interaction. Comprehensively considering the cost, renewability, and the application to real water samples, the carbonaceous nanocomposites have potential in removal of SMT and possibly other persistent organic pollutants from wastewater.

Nanoporous Au-based chronocoulometric aptasensor for amplified detection of Pb(2+) using DNAzyme modified with Au nanoparticles

The authors herein described an amplified detection strategy employing nanoporous Au (NPG) and gold nanoparticles (AuNPs) to detect Pb(2+) ions in aqueous solution. The thiol modified Pb(2+)-specific DNAzyme was self-assembled onto the surface of the NPG modified electrode for hybridizing with the AuNPs labeled oligonucleotide and for forming the DNA double helix structure. Electrochemical signal, redox charge of hexaammineruthenium(III) chloride (RuHex), was measured by chronocoulometry. Taking advantage of amplification effects of the NPG electrode for increasing the reaction sites of capture probe and DNA-AuNPs complexes for bringing about the adsorption of large numbers of RuHex molecules, this electrochemical sensor could detect Pb(2+) quantitatively, in the range of 0.05-100nM, with a limit of detection as low as 0.012nM. Selectivity measurements revealed that the sensor was specific for Pb(2+) even with interference by high concentrations of other metal ions. This sensor was also used to detect Pb(2+) ions from samples of tap water, river water, and landfill leachate samples spiked with Pb(2+) ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. This simple aptasensor represented a promising potential for on-site detecting Pb(2+) in drinking water.

Sensitive and selective detection of mercury ions based on papain and 2,6-pyridinedicarboxylic acid functionalized gold nanoparticles

Here we demonstrate the rational design of a sensitive and selective colorimetric method for mercury ion (Hg²⁺) detection by using papain and 2,6-pyridinedicarboxylic acid (PDCA) functionalized gold nanoparticles (AuNPs).

Influence of morphological and chemical features of biochar on hydrogen peroxide activation: implications on sulfamethazine degradation

This paper investigated how morphological and chemical features of biochars influenced hydroxyl radical generation and sulfamethazine degradation in the presence of hydrogen peroxide.