In order to achieve the effective removal of Pb 2+ from low-concentration wastewater as well as the lead recovery for direct reuse simultaneously, a simple electrodeposition method was used in this study. In this process, synthetic lead wastewater with low concentration of 4, 8, 12 and 16 mg/L was treated, more than 67% lead was recovered from wastewater and a PbO 2 /Ti electrode was fabricated in a simple reaction tank. The test results of characterizations confirmed that PbO 2 nanoeletrocatalyst was successfully deposited on a Ti substrate. Electrochemical activity tests indicated that PbO 2 /Ti electrode had advantages of high oxygen evolution potential (1.90 V) and low electron transfer resistance. Furthermore, the results of electrocatalytic degradation experiments demonstrated that prepared PbO 2 /Ti electrode had the superb decolorization and mineralization ability on Basic Red. After 120 min of electrolysis, the Basic Red removal efficiency and TOC removal efficiency could reach to 89.38% and 68.82%, respectively, which was 5.2 and 7.1 times higher than the Ti substrate alone. Besides, the calculated mineralization current efficiency for PbO 2 /Ti electrode increased from 5.18% to 36.74% after PbO 2 depositing, and thus an economical benefit was obtained by more than 5 times energy saving. The influences of the applied current density, initial dye concentration, electrolyte concentration and solution pH on the oxidation efficiency were also investigated and optimized. The prepared PbO 2 /Ti electrode also showed a great stability with high dye removal efficiency (above 85%) after 10 times repeated experiments. These results suggest that it is a promising technological process to remove and recover lead from low-concentration wastewater efficiently and reuse them as electrocatalyst for other organic wastewater treatments.
Biomass-based activated carbon materials provide a novel approach for the development of high-performance electrode materials for supercapacitors without the need for fossil fuel energy sources. Herein, activated carbon with an interconnected hierarchical architecture was designed and fabricated from hazelnut shells via H3PO4-assisted KOH activation. The results indicated that the activated carbon material with an interconnected pore framework was successfully fabricated and exhibited excellent electrochemical performance. The pore size distribution of the activated carbon could be tuned by the quantity of KOH that was added. A hierarchical architecture containing a gradient distribution from nanopores to micropores had the optimal connectivity and improved the electric double-layer capacitance and capacitance retention rate, while abundant heteroatoms on the surface or edges of the carbon matrix enhanced the pseudocapacitance. The highest specific capacitance was achieved 338 F·g–1 at a current density of 0.2 A·g–1 and the highest capacitance retention was 86.3% at 10 A·g–1 in a three-electrode system. The symmetrical capacitor (SC) device had an energy density of 16.42 W·h·kg–1 at a power density of 160 W·kg–1 in Na2SO4 electrolyte. In Na2SO4 gel electrolyte, the SC device exhibited a high energy density of 22.46 W·h·kg–1 at a power supply of 450 W·kg–1 and outstanding cycle stability with 133% of the initial capacity after 10,000 cycles in an operating potential of 1.8 V. This work provides an efficient strategy for the preparation of high-performance activated carbon electrodes from hazelnut shells.
PAN-based carbon membranes were prepared using dip-coating method, in which porous coal-based carbon tubes were used as support. The effects of carbonization condition on the properties of PAN-based carbon membranes were investigated. The results indicate that carbonization temperature and heating rate have great effects on the pore structure properties of carbon membranes, while holding time and gas flow rate have slight effects on the pore structure properties of carbon membranes. The crack-free PAN-based carbon membranes can be prepared by optimizing the experimental parameters.
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