No abstract

Though an excellent protection material, graphene possesses an unpleasant adverse side effect, which refers to the phenomenon that graphene can aggravate metal corrosion. This effect potentially impedes its applications in metal protection. This work aims to demonstrate a facile graphene encapsulation strategy to effectively inhibit the corrosion-promotion activity of graphene. We encapsulated reduced graphene oxide (rGO) with (3-aminopropyl)-triethoxysilane (APTES). The composite of encapsulated rGO (rGO@APTES) has a flake-like structure with high aspect-ratio. Embedding appropriate amounts of rGO@APTES in polyvinyl butyral coating effectively enhances the barrier properties of the coating by suppressing the penetration of aggressive species. Besides, scratch tests further reveal that the corrosion-promotion activity of the graphene incorporated into the coating is completely inhibited. The strategy of graphene encapsulation can be extended to develop new graphene-based materials with superior physical and chemical properties for the protection of metal components.

The US National Research Council recently recommended direct potable water reuse (DPR), or potable water reuse without environmental buffer, for consideration to address US water demand. However, conveyance of wastewater and water to and from centralized treatment plants consumes on average four times the energy of treatment in the USA, and centralized DPR would further require upgradient distribution of treated water. Therefore, information on the cost of unit treatment processes potentially useful for DPR versus system capacity was reviewed, converted to constant 2012 US dollars, and synthesized in this work. A logarithmic variant of the Williams Law cost function was found applicable over orders of magnitude of system capacity, for the subject processes: activated sludge, membrane bioreactor, coagulation/flocculation, reverse osmosis, ultrafiltration, peroxone and granular activated carbon. Results are demonstrated versus 10 DPR case studies. Because economies of scale found for capital equipment are counterbalanced by distribution/collection network costs, further study of the optimal scale of distributed DPR systems is suggested.

Performance degradation caused by the oxidation of carbon anodes during capacitive deionization (CDI) remains a major problem that may greatly restrict the practical application of CDI. To improve the cyclic stability of CDI, carbon-based anode materials were replaced by pseudocapacitive MnO 2 in this work. The cation-selective MnO 2 anode was assembled with an anion-selective quaternized poly(4-vinylpyridine)coated activated carbon cathode into a hybrid CDI cell. The cell exhibited inverted CDI performance with a wide operating voltage window of 1.4 V and a salt adsorption capacity (SAC) of 14.9 mg/g in 500 mg/L NaCl. The SAC retention ratio of the cell can be as high as 95.4% after 350 adsorption−desorption cycles at 1.0/0 V, while that of the CDI cell consisting of activated carbon electrodes was only 15.7% after 285 cycles. The enhanced cyclic stability of the hybrid CDI cell is attributed to the employment of the MnO 2 anode, which avoided the use and oxidation of carbon anodes.