Three-dimensional nanoporous activated carbon electrode derived from acacia wood for high-performance supercapacitor.

Herein, the novel acacia wood based hierarchical porous activated carbons (AWCs) are easily prepared, low cost and have excellent characterization, such as special biomass nanopores via structural stability and large specific surface areas. Activating agents such as KOH, ZnCl2, and H3PO4 have been used to convert acacia wood carbon into active carbons such as AWC-K, AWC-Z, and AWC-P, respectively, which are named after the activating agent. As a supercapacitor electrode, the AWC-K sample has a high yield was 69.8%, significant specific surface area of 1563.43 m2g-1 and layer thickness of 4.6 mm. Besides that, it showed specific capacitance of 224.92 F g-1 at 0.5 A g-1 in 2 M KOH as electrolyte. In addition, the AWC-K//AWC-K symmetrical supercapacitor device displays high energy density of 23.98 Wh kg-1 at 450 W kg-1 power density with excellent cycling number stability was 93.2% long lifetime of 10,000 cycles using 0.5 M Na2SO4 as electrolyte. The high electrochemistry performance mainly contributed the special biomass pores structure. Therefore, the presented approach opens new avenues in supercapacitor applications to meet energy storage.

Effects of ZnO nanoparticles on the performance of anaerobic membrane bioreactor: An attention to the characteristics of supernatant, effluent and biomass community.

Two laboratory-scale anaerobic membrane bioreactor (AnMBRs) were built to investigate the effect of zinc oxide nanoparticles (ZnO-NPs) on their performance, and the recovery phase was also examined. Results showed that the addition of ZnO-NPs with 0.4 mg/L caused significant deteriorations of AnMBR performance, including decrements of chemical oxygen demand (COD) removal efficiency from 96.4% to 81.5% and biogas production from 0.36 to 0 L/g COD removal within 40 days. A significant increment from 13.2 to 52.1 mg/L in soluble microbial products (SMP) was obtained, while no obvious effect on colloids was observed except an increased fluctuation of colloid concentration. Additionally, gas chromatography-mass spectrometry (GC-MS) analysis revealed remarkable changes of compounds in effluent with exposure to ZnO-NPs, and some new alkanes and esters were produced, such as Cyclobutane, 1,2-diethyl-, trans-, Tetradecane, Cyclopropane, octyl-, and Butanoic acid, methyl ester. The microbial community was compared using high-throughput sequencing, clearly showing the changes in both bacteria and archaea communities. Furthermore, results for recovery phase indicated that the AnMBR performance can be recovered within around 60 days after stopping ZnO-NPs addition, accompanied by the decrement of zinc concentration mainly adsorbed by sludge.

Effects of salinity on the biological performance of anaerobic membrane bioreactor.

The performance of anaerobic membrane bioreactor (AnMBR) was evaluated treating synthetic wastewater with various concentrations of NaCl (0-40 g/L), as well as the recovery phase. The effluent COD removal efficiency decreased from 96.4% to 95.0%, 91.4%, 86.7% and 77.7% with stepwise increasing of salt concentration from 0 to 5, 10, 20 and 40 g NaCl/L, respectively, then gradually increased to 94.1% during the recovery phase. Additionally, the significant changes in the content and composition of soluble microbial products (SMP) and extracellular polymer substance (EPS) were obtained under higher salt stress. GC-MS analyses were carried out for the effluent, and some new types of compounds, such as Dodecane, Undecane, and Ethyl Acetate, were found during salt exposure phases. The characterization of the microbial community was also investigated based on the analysis of genomic 16S rDNA, revealing the increasing salinity (5-40 g NaCl/L) could reduce the diversity of sludge microbial community in AnMBR. Meanwhile, the significant effects on the composition of dominate phyla (Proteobacteria, Bacteroidetes, Firmicutes and Chloroflexi) were found during the salt exposure phase.

Investigation of the long-term desalination performance of membrane capacitive deionization at the presence of organic foulants.

A long-term performance of membrane capacitive deionization (MCDI) was investigated at the presence of organic matter, which has contributed to the understanding of fouling phenomena and energy efficiency. The commercial humic acid and sodium alginate were adopted as model substances representative of natural organic matter, and different ions including sodium and calcium were selected as important parameters considered in both model substances. The experimental results showed reductions in the salinity removal ability and increments of energy usage due to the organic fouling of ion-exchange membranes and carbon electrodes. Within a time interval of approximately 15 d, reductions of NaCl adsorbance with 5.3 and 3.3 mg per cycle were obtained for humics and alginate, respectively. Simultaneously, the energy consumptions increased by 56.9% for humics and 26.3% for alginate. Furthermore, the results in terms of calcium removal in organic feed and energy usage showed that it had a higher fouling potential in comparison to the ones for the sodium solution with equal conductivity and organic concentration. The morphology and composition of the fouling layer were further studied, and it was found that the organic adsorption onto the electrodes and the attachment or even penetration of organic matter on or into the ion-exchange membrane, which could not be efficiently desorbed during the regeneration cycle, were determined as a key problem of demineralized water production. Therefore, this study suggested the necessity of a pre-treatment to reduce the presence of organic matter for the sustainable operation of MCDI, hereby broaden the potential application fields.