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This study examines the specific effect of Tween 80 on the conversion of anthracene (ANT) in laccase medium system regarding surfactant chemical changes and mechanism. The conversion rate and degradation products of ANT were investigated in different concentrations of Tween 80 solution. Between Tween 80 concentration 0–40 critical micelle concentrations (CMC), the kinetic parameter-k (h−1) and corresponding half-life T1/2 decreased with increasing concentration. When Tween 80 was above 20 CMC the laccase-medium system converted > 95% of ANT to anthraquinone within 12 h. During the entire enzymatic reaction, the laccase activity in the system increased with increasing Tween 80 concentration. Combined with GC/MS analysis of the product, it was speculated that hydrogens belonging to the ether-oxygen bond and carbon–carbon double bond α-CH of Tween 80, were removed by the laccase-media system, promoting its degradation. Additionally, enhanced activity caused by oxygen free radicals (ROS) such as RO• and ROO•, continuously oxidized Tween 80, which in turn produced free radicals while converting ANT. This study provides new theoretical support toward the application of surfactants in the elimination of polycyclic aromatic hydrocarbons.

Carbon nanotubes (CNTs) have been widely exploited to improve anodic performance, but information is needed on their long-term stability for improvement. Herein, we prepared a novel CNTs-modified graphite felt (CNTs-GF) by a simple and scalable process and evaluated its long-term performance using anaerobic sludge as inoculum. the MFC with CNTs-GF yielded a sustained enhancement of power output, increasing from 1.93 ± 0.09 W m−2 after 1 month to 2.10 ± 0.05 W m−2 after 3 months and reaching 2.00 ± 0.10 W m−2 after 13 month, indicating the enhancement in electricity generation by the CNTs was not declined over one year. However, the bare GF showed a declining tendency of performance during 13 months. The long-term enhancement can be explained by the facts that the CNTs-GF was beneficial to electrochemically active biofilms (EABs) growth and interacted better with EABs and increased the extracellular electron transfer. Community analysis showed an increase in Geobacter in response to CNTs modification. These results demonstrated that CNTs modification could sustain a superior long-term enhancement in MFC performance.

In this study, novel geopolymers based on solid wastes (coal gangue and red mud) were used in the adsorption of heavy metals (Pb2+ and Cu2+) from solution. The correlations between the composition and quantity of the geopolymer gels and heavy metal adsorption were investigated under various conditions using hydrochloric acid dissolution and spectroscopic techniques. The results showed that the geopolymer gel positively correlated with the Pb2+ and Cu2+ adsorption capacities in the absence of external silica and aluminum. Moreover, external silica and aluminum sources promoted Al2O3 and SiO2 dissolution in the raw materials, which increased and decreased the specific surface areas, respectively. All of the tested geopolymers exhibited Pb2+ and Cu2+ adsorption based on the Langmuir isotherm and the pseudo-second-order kinetic model, with adsorption maxima of 137.7 and 90 mg g−1, respectively. This research first determined the correlation between the geopolymer gel and its heavy metal adsorption performance, and demonstrated industrial waste-based geopolymers could be effectively applied for the removal of heavy metal which can help reduce the burden of waste management and provide new insights about the resource recovery of solid wastes.

A novel anthraquinone-2,6-disulfonate/MnOx-doped polypyrrole film (AQDS/Mn/PPy) electrode was prepared by one-step electropolymerization method and was used to improve performance of a reversible photo-bioelectrochemical cell (RPBEC). The RPBEC was operated in polarity reversion depended on dark/light reaction of alga Chlorella vulgaris by which sequential decolorization of azo dye and mineralization of decolorization products coupled with bioelectricity generation can be achieved. The results showed that formation of uniform AQDS/Mn/PPy film significantly enhanced electroactive surface area and electrocatalytic activity of carbon electrode. The RPBEC with AQDS/Mn/PPy electrodes demonstrated 77% increases in maximum power and 73% increases in Congo red decolorization rate before polarity reversion, and 198% increases in maximum power and 138% increases in decolorization products mineralization rate after polarity reversion, respectively, compared to the RPBEC with bare electrode. This was resulted from simultaneous dynamics improvement in half-reaction rate of anode and photo-biocathode due to enhanced electron transfer and algal-bacterial biofilm formation.

Spent mushroom substrate (SMS) is a bulky waste byproduct of commercial mushroom production, which can cause serious environmental problems and, therefore, poses a significant barrier to future expansion of the mushroom industry. In the present study, we explored the use of SMS as a biochar to improve the quality of bio-fertilizer. Specifically, we performed a series of experiments using composting reactors to investigate the effects of SMS biochar on the physio-chemical properties of bio-fertilizer. Biochar was derived from dry SMS pyrolysed at 500°C and mixed with pig manure and rice straw. Results from this study demonstrate that the addition of biochar significantly reduced electrical conductivity and loss of organic matter in compost material. Nutrient analysis revealed that the SMS-derived biochar is rich in fertilizer nutrients such as P, K, Na, and N. All of these findings suggest that SMS biochar could be an excellent medium for compost.

Biocathode microbial fuel cell performances with respect to azo dye decolorization and electricity generation were examined using two anodic inoculums, textile dyeing sludge (MFC-I) and municipal sludge (MFC-M), to determine the potential performance regulation of the MFC via the selection of anodic inoculum. The results showed that the MFC-I exhibited excellent performance in Congo red decolorization, whereas the MFC-M performed well in electricity generation. The MFC-I achieved fast Congo red decolorization with a first-order rate constant k = 0.0501, which was 34% higher than that obtained by MFC-M (k = 0.0375). The MFC-M exhibited 3.22 times higher power output (29 mW/m2 vs. 9 mW/m2) and 38.0% lower anode impedance (749 Ω vs. 1208 Ω) compared to MFC-I. The functional stains isolated from the anodic biofilm of MFC-I were identified as Pseudomonas sp. and Aquamicrobium sp., while isolates from MFC-M belonged to Pseudomonas sp. and Bacillus sp. Four selected isolates were proved to be exoelectrogens and bacterial decolorizer simultaneously but exhibited different bioelectrocatalytic activities and dye decolorizing capabilities, which could partly explain the performance difference between the two MFCs with different anodic inocula.

A novel series of adamantane-based gemini quaternary ammonium salts (GQASs) named as m-Ad-m (bromides, alkyl chain length, m = 12, 14, 16) are synthesized from 1,3-adamantanedicarboxylic acid. Their chemical structures are confirmed by 1H NMR, FT-IR and ESI-MS. The surface activities in aqueous solutions of m-Ad-m are evaluated by surface tension. Unlike conventional GQASs with a flexible spacer, m-Ad-m possessing a rigid adamantane spacer show lower surface tension (γCMC) values as compared to conventional GQASs bearing the same alkyl chains. The thermodynamic properties of m-Ad-m are examined by electrical conductivity measurements at different temperatures, including molecular interaction parameters (β), standard Gibbs free energy (ΔG0m), enthalpy (ΔH0m) and entropy (ΔS0m), which show that the micellization of m-Ad-m is entropy-driven. TEM study exhibits that the aggregate morphologies of m-Ad-m change from micelles and spheroidal vesicles of varying size to network aggregates and then to globular vesicles with the increase in m-Ad-m concentration. Furthermore, the antimicrobial efficacy of m-Ad-m against both Gram-positive bacteria (S. aureus and B. subtilis) and Gram-negative bacteria (E. coli, P. aeruginosa and V. parahaemolyticus) is systematically studied by minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) methods, which indicates the favorable antibacterial activity of 12-Ad-12 against the studied bacteria.

In order to develop surfactant-enhanced remediation for nitrogen heterocyclic compounds (NHCs) (aniline, indole, and quinolone), the solubilization properties of micellar solutions of five surfactants, namely sodium dodecyl sulfate (SDS), rhamnolipid (RL), polysorbate (Tween 80), sorbitan monolaurate (Span 20), and iso-octyl phenoxy polyethoxy ethanol (TX-100) were investigated in this work. The solubilization capacities were quantified using critical micelle concentration (CMC) as well as thermodynamic and kinetic experiments. Besides, nuclear magnetic resonance (1H NMR) spectra were used to infer the locus of NHCs solubilized by SDS and TX-100. The results from the properties of five surfactants indicated that CMC was affected by temperature, while the micellization was spontaneous and could be both endothermic and exothermic based on the type of surfactant and temperature. Furthermore, the difference in compensation temperature was caused by different solubilization mechanism for various surfactants. The solubilization results showed that the solubilization of NHCs in the surfactant solutions followed a pseudo-first-order kinetic model. Meanwhile, the change in proton’s chemical shift depended on the structure of NHCs and the solubilization ability of surfactants. Finally, the orthogonal experiment (L16(43)) was elementarily designed to optimize the solubilization conditions of indole and the results showed that RL could be a better choice for solubilizing NHCs.

Heavy metals play an important role in the conductivity of solution, power generation and activity of microorganisms in bioelectrochemical systems (BESs). However, effect of heavy metal on the process of exoelectrogenesis metabolism and extracellular electron transfer of electrochemically active biofilms (EABs) was poorly understood. Herein, we investigated the impact of Cu2+ at gradually increasing concentration on the morphological and electrochemical performance and bacterial communities of anodic biofilms in mixed-culture BESs. The voltage output decreased continuously and dropped to zero at 10 mg L−1, which was attributed to the toxic inhibition that cased anodic biofilm damage and decreased secretion of outer membrane cytochromes. When stopping the introduction of Cu2+ to anodic chamber, the maximum voltage production recovered 75.1% of the voltage produced from BES and coulombic efficiency was higher but acetate removal rate was lower than that before Cu2+ addition, demonstrating the recovery capability of EABs was higher compared to nonelectroactive bacteria. Moreover, SEM-EDS and XPS suggested that most of Cu2+ was adsorbed by the anode electrode and reduced by EABs on anode. Compared to the open-circuit BES, the flow of electrons through a circuit could improve the reduction of copper. Community analysis showed a decrease in Geobacter accompanied by an increase in Stenotrophomonas in response to Cu2+ shock in anodic chamber.