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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.

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 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.

Aromatic amines (AAs), which are components of synthetic dyes, are recalcitrant to the wastewater treatment process and can accumulate in sludge produced by textile-dyeing, which may pose a threat to the environment. A comprehensive investigation of 10 textile-dyeing plants was undertaken in Guangdong Province in China. The contents and component distributions of AAs were evaluated in this study, and a risk assessment was performed. The total concentrations of 14 AAs (Σ14 AAs) varied from 11 μg g −1 dw to 82.5 μg g −1 dw, with a mean value of 25 μg g −1 dw. The component distributions of AAs were characterized by monocyclic anilines, of which 2-methoxy-5-methylaniline and 5-nitro-o-toluidine were the most dominant components. The risk quotient (RQ) value was used to numerically evaluate the ecological risk of 14 AAs in the environment. The result showed that the 14 AAs contents in textile-dyeing sludge may pose a high risk to the soil ecosystem after being discarded on soil or in a landfill.

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.

The effects of micro-electrolysis treatment on textile dyeing sludge dewatering and its mechanisms were investigated in this study. Capillary suction time (CST) and settling velocity (SV) were used to evaluate sludge dewaterability. Extracellular polymeric substances (EPS) concentration and sludge disintegration degree (DDSCOD) were determined to explain the observed changes in sludge dewaterability. The results demonstrated that the micro-electrolysis could significantly improve sludge dewaterability by disrupting the sludge floc structure. The optimal conditions of sludge dewatering were the reaction time of 20 min, initial pH of 2.5, Fe/C mass ratio of 1/1, and the iron powder dosage of 2.50 g/L, which achieved good CST (from 34.1 to 27.8 s) and SV (from 75 to 60%) reduction efficiency. In addition, the scanning electron microscope (SEM) images revealed that the treated sludge floc clusters are broken up and that the dispersion degree is better than that of a raw sludge sample. The optimal EPS concentration and DDSCOD to obtain maximum sludge dewaterability was 43-46 mg/L and 4.2-4.9%, respectively. The destruction of EPS was one of the primary reasons for the improvement of sludge dewaterability during micro-electrolysis treatment.

The effect of potassium ferrate/ultrasonic (K2FeO4/US) treatment on the physicochemical features of textile dyeing sludge was studied. The soluble chemical oxygen demand (SCOD), deoxyribonucleic acid (DNA), sludge volume index (SVI), sludge viscosity, capillary suction time (CST) and particle size were measured to understand the observed changes in the sludge physicochemical features. The results showed that the combined K2FeO4/US treatment presented great advantages for disrupting the sludge floc structure over K2FeO4 or ultrasonic treatments alone. The optimal parameters of sludge disintegration were found to be a K2FeO4 treatment time of 60 min, a K2FeO4 dosage of 0.5936 g/g SS, an ultrasonic time of 15 min and an ultrasonic intensity of 0.72 W/mL. The initial median diameter of the sludge particles was 15.24 μm, and this value decreased by 35.89%. The CST was initially 59.6 s and increased by 231%, whereas the SVI was 97.78 mL/g and decreased by 25.89%. Scanning electron microscope (SEM) images indicated that the sludge surface was irregular and loose with a large amount of channels or voids during K2FeO4/US treatment. K2FeO4/US treatment synergistically enhanced the sludge solubilization and reached 668.67 mg/L SCOD, which is 31.81% greater than the additive value obtained with K2FeO4 treatment alone (215.95 mg/L) or with ultrasonic treatment alone (240 mg/L).

A solar-heated anaerobic reactor system was applied to decompose livestock wastewater, in which cattle manure and chopped straw were mixed (CODCr 15,000~25,000 mgl-1), the commercial microorganisms were added to ambient acidification (about 32°C) and the acclimated sludge was inoculated. Then, the experiments were carried out on wastewater anaerobic degradation and biogas production at 40~42°C, as fed every 10 days till stable running. The results showed that NH3-N and PO4 3- of the biogas slurry were 441 mgl-1 and 65.0 mgl-1 on the 35th day, respectively. The concentration of K was up to 350 mgl-1 in the biogas slurry, rather higher than that of Mg and Fe, which indicated that the available K could contribute more in the agricultural irrigation. Total amino acids were up to 23.7 mgl-1 after anaerobic digestion, in which Lys, Thr, Ala and Arg were prominent in the biogas slurry. These amino acids could be beneficial to seed soaking, feed adding and apply as foliar fertilizer. The major volatile organic compounds were detected in the biogas slurry, including toluene, m-cresol (up to 0.036% in the process of ambient acidification) and triethylsilane, which could be reduced to scarcely influence on agricultural application after anaerobic digestion.

The occurrence and removal of benzene, toluene, ethylbenzene, xylenes, styrene and isopropylbenzene (BTEXSI) from 6 textile dyeing wastewater treatment plants (TDWTPs) were investigated in this study. The practical capacities of the 6 representative plants, which used the activated sludge process, ranged from 1200 to 26000 m(3) d(-1). The results indicated that BTEXSI were ubiquitous in the raw textile dyeing wastewater, except for isopropylbenzene, and that toluene and xylenes were predominant in raw wastewaters (RWs). TDWTP-E was selected to study the residual BTEXSI at different stages. The total BTEXSI reduction on the aerobic process of TDWTP-E accounted for 82.2% of the entire process. The total BTEXSI concentrations from the final effluents (FEs) were observed to be below 1 μg L(-1), except for TDWTP-F (2.12 μg L(-1)). Volatilization and biodegradation rather than sludge sorption contributed significantly to BTEXSI removal in the treatment system. BTEXSI were not found to be the main contaminants in textile dyeing wastewater.

As components of synthetic dyes, polycyclic aromatic hydrocarbons (PAHs) are present as contaminants in textile dyeing sludge due to the recalcitrance in wastewater treatment process, which may pose a threat to environment in the process of sludge disposal. In order to evaluate PAHs in textile dyeing sludge, comprehensive investigation comprising 10 textile dyeing plants was undertaken. Levels, composition profiles and risk assessment of 16 EPA-priority PAHs were analyzed in this study. The total concentrations of 16 PAHs (∑16 PAHs) varied from 1463 ± 177 ng g(-1) to 16,714 ± 1,507 ng g(-1) with a mean value of 6386 ng g(-1). The composition profiles of PAHs were characterized by 3- and 4-ring PAHs, among which phenanthrene, anthracene and fluoranthene were the most dominant components. The mean benzo[a]pyrene equivalent (BaPeq) concentration of ∑16 PAHs in textile dyeing sludge was 423 ng g(-1), which was 2-3 times higher than concentrations reported for urban soil. According to ecological risk assessment, the levels of PAHs in the textile dyeing sludge may cause a significant risk to soil ecosystem after landfill or dumping on soil.