A highly sensitive, long-time stable Ag/AgCl ultra-micro sensor for in situ monitoring chloride ions inside the crevice using SECM.

Tracking the variation of Cl- timely within the crevice is of great significance for comprehending the dynamic mechanism of crevice corrosion. The reported chloride ion selective electrodes are difficult to realize the long-time Cl- detection inside the confined crevice, due to their millimeter size or a relative limited lifespan. For this purpose, an Ag/AgCl ultra-micro sensor (UMS) with a radius of 12.5 µm was fabricated and optimized using laser drawing and electrodeposition techniques. Results show the AgCl film's structure is significantly impacted by the deposited current density, and further affects the linear response, life span and stability of Ag/AgCl UMS. The UMS prepared at current density of 0.1 mA/cm2 for 2 h shows a rapid response (several seconds), excellent stability and reproducibility, strong acid/alkali tolerance, sufficient linearity (R2 > 0.99), and long lifespan (86 days). Moreover, combined with the potentiometric mode of scanning electrochemical microscope (SECM), the Ag/AgCl UMS was successfully applied to monitor the in-situ radial Cl- concentration in micro-regions inside a 100 µm gap of stainless steel. The findings demonstrated that there was obvious radial difference in Cl- concentration inside the crevice, where the fastest rise in Cl- concentration was at the opening. The proposed method which combines the UMS with SECM has attractive practical applications for microzone Cl- monitoring in real time inside crevice. It may further promote the study of other localized corrosion mechanism and the development of microzone ions detection method.

Synchronous bio-degradation and bio-electricity generation in a Microbial Fuel Cell with aged and fresh leachate from the identical subtropical area.

Seasonal leachate from both sealed and operating landfill in the identical district were employed as the sole substrate in the Microbial Fuel Cell (MFC) to evaluate the power output performance and aqueous organic waste disposal. The electrical performance was characterized to study the power generation, while the Chemical Oxygen Demand (COD) removal ratio and Coulombic Efficiency (CE) were calculated to illustrate the substrate disposal effect. In addition, Scanning Electron Microscope (SEM) on the operated anode was conducted to preliminarily explain the microbial community difference, and the phylogenetic tree constructed on the cultivated microorganism was an insight into the dominant bacteria suitable for leachate degradation. It was found that the MFCs inoculated with seasonal leachate from both sealed and operating landfill could generate electricity successfully. Although the fresh leachate-inoculated MFCs had better electrical output performance (22.7-25.6 W/m3 versus 6.61-7.48 W/m3) and COD removal efficiency (55.8%∼61.7% versus 47.7%∼51.4%), the CEs were only 4.3%∼7.6%, which were lower than the aged leachate inoculated group (5.9%∼11.3%). Based on the SEM images and the phylogenetic tree of the operated anode, the composition impacts on the microbial community and power output performance were verified, which was instructive for the leachate disposal in the MFC.

[Preparation of Modified Watermelon Biochar and Its Adsorption Properties for Pb(â ¡)].

In this study, watermelon rind was used as a raw material to modify watermelon rind biochar (MBC) with ammonium sulphate[(NH4)2S] for adsorption of Pb(Ⅱ) ions. The effects of solution pH, adsorption time, adsorbent addition amount, initial mass concentration of Pb(Ⅱ) ions, and ionic strength on the adsorption of Pb(Ⅱ) ions were investigated. The results show that the saturated adsorption time was 5 h, the optimum pH of the adsorption reaction was 6, and when the initial mass concentration of Pb(Ⅱ) ions were 1000 mg·L-1, and the amount of adsorbent was 2.0 g·L-1. The maximum adsorption amount of MBC to Pb(Ⅱ) ions can reach 97.63 mg·g-1, which is significantly higher than unmodified watermelon husk biochar (BC). The adsorption of Pb(Ⅱ) ions by modified watermelon biochar was in accordance with the Langmuir isotherm adsorption model and the pseudo second-order kinetic model, which proves that adsorption is dominated by monolayer chemical adsorption. The desorption of MBC after adsorption of Pb(Ⅱ) ions was carried out using a sodium hydroxide solution to study the reusability of MBC, and the adsorption amount was still 64.74 mg·g-1 in the sixth cycle. Characterization and analysis of adsorbents by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption, scanning electron microscopy-energy spectroscopy, zeta potential analysis, and X-ray diffraction (XRD) were carried out, which showed that the adsorption mechanism is mainly that MBC oxygen- and MBC sulfur-containing groups adsorb Pb(Ⅱ) through complexation and precipitation. Therefore, ammonium sulfide modified watermelon rind biochar can be used as a highly efficient lead adsorbent.

[Effects and Mechanisms of Methyl Orange Removal from Aqueous Solutions by Modified Rice Shell Biochar].

Waste rice shell (RS) was used for modified biochar preparation via different activation methods. The types of modifiers, impregnation ratio, and pyrolysis temperature have significant effects on the characteristics of biochar and the adsorption capacity of methyl orange (MO). The physical and chemical properties of modified biochar and MO adsorption mechanisms were analyzed by N2-adsorption, X-ray diffraction (XRD), Fourier infrared spectroscopy (FT-IR), field emission scanning electron microscopy (SEM), thermogravimetric analyzer (TG), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that the modified biochar (named Z2RT400) prepared at 400℃ with a mass ratio of 2:1 (ZnCl2:rice shell) had the highest adsorption capacity for MO. Under the following conditions with a solution pH value of 4, adsorbent dosage of 10 mg, initial MO concentration of 2000 mg·L-1, and reaction time of 420 min, the maximum adsorption capacity of Z2RT400 was 1967.72 mg·g-1. When the adsorbent dosage was 80 mg, the maximum removal rate reached 99.52%. The adsorption data fitted well with the pseudo-second order kinetic model and Freundlich isotherm model, which indicates that chemical adsorption is the main adsorption mechanism and physical adsorption is the auxiliary adsorption mechanism. Therefore, the waste rice shell derived biochar can be used as a highly efficient dye adsorbent in applications such as sewage treatment.

Significant enhancement of electron transfer from Shewanella oneidensis using a porous N-doped carbon cloth in a bioelectrochemical system.

Modifying the surface of an anode can improve electron transfer, thus enhancing the performance of the associated bioelectrochemical system. In this study, a porous N-doped carbon cloth electrode was obtained via a simple thermal reduction and etching treatment, and then used as the anode in a bioelectrochemical system. The electrode has a high nitrogen-to­carbon (N/C) ratio (~3.9%) and a large electrochemically active surface area (145.4 cm2, about 4.4 times higher than that of the original carbon cloth), which increases the bacterial attachment and provides more active sites for extracellular electron transfer. Electrochemical characterization reveals that the peak anodic current (0.71 mA) of the porous N-doped carbon cloth electrode in riboflavin is 18 times higher than that of the original carbon cloth electrode (0.04 mA), confirming the presence of more electroactive sites for the redox reaction. We also obtained a maximum current density of 0.29 mA/cm2 during operation of a bioelectrochemical system featuring the porous N-doped carbon cloth electrode, which is 14.5 times higher than that of the original carbon cloth electrode. This result demonstrates that the adoption of our new electrode is a viable strategy for boosting the performance of bioelectrochemical systems.

Enhanced Rhodococcus pyridinivorans HR-1 anode performance by adding trehalose lipid in microbial fuel cell.

In this study, a trehalose lipid was added to a Rhodococcus pyridinivorans-inoculated MFC to improve the power output by enhancing electron transfer. Upon trehalose lipid additions of different concentrate from 0 to 20 mg/L, the maximum power density increased from 54.7 mW/m2 to 324.4 mW/m2 (5.93 times) while the corresponding current density was 3.66 times increased from 0.35 A/m2 to 1.28 A/m2. Cyclic voltammetry analysis revealed that the addition of trehalose lipid increased the electron transfer performance, while electrochemical impedance spectroscopy results proved a decrease in internal resistance. It was demonstrated that adding bio-surfactant in MFC was a novel way to enhance power output performance.

Endogenously enhanced biosurfactant production promotes electricity generation from microbial fuel cells.

Microbial fuel cell (MFC) is considered as a promising green energy source and energy-saving pollutants treatment technology as it integrates pollutant biodegradation with energy extraction. In this work, a facile approach to enhance endogenous biosurfactant production was developed to improve the electron transfer rate and power output of MFC. By overexpression of rhlA, the key gene responsible for rhamnolipids synthesis, over-production of self-synthesized rhamnolipids from Pseudomonas aeruginosa PAO1 was achieved. Strikingly, the increased rhamnolipids production by rhlA overexpression significantly promoted the extracellular electron transfer of P. aeruginosa by enhancing electron shuttle (pyocyanin) production and increasing bacteria attachment on the anode. As a result, the strain with endogenously enhanced rhamnolipids production delivered 2.5 times higher power density output than that of the parent strain. This work substantiated that the enhancement on endogenous biosurfactant production could be a promising approach for improvement on the electricity output of MFC.