Hydrogen oxidation and evolution on Pt in acid are facile processes, while in alkaline electrolytes they are two-orders-of-magnitude slower. Thus, developing catalysts that are more active than Pt for these two reactions is important for advancing the performance of anionexchange-membrane fuel cells and water electrolyzers. Herein, we detail a four-fold enhancement in Pt mass activity that we achieved using single crystalline Ru@Pt core-shell nanoparticles with two-monolayer-thick Pt shells, which doubles the activity on Pt-Ru alloy nanocatalysts. For Pt specific activity, the 2-and 1-monolayer-thick Pt shells, respectively, exhibited an enhancement factor of 3.1 and 2.3 compared to the Pt nanocatalysts in base, differing considerably from the values of 1 and 0.4 in acid. To explain such behavior and the orders-of-magnitude difference in activity on going from acid to base, we performed kinetic analyses of polarization curves over a wide range of potential from -250 to 250 mV using the dual-pathway kinetic equation. From acid to base, the activation free energies increase the most for the Volmer reaction, resulting in a switch of the rate-determining step from the Tafel-to the Volmer-reaction, and a shift to a weaker optimal hydrogen-binding energy. The much higher activation barrier for the Volmer reaction in base than in acid is ascribed to one or both of the two catalyst-insensitive factors -slower transport of OH -than H + in water, and a stronger O-H bond in water molecules (HO-H) than in hydrated protons (H 2 O-H + ).

Activated carbon derived from finger citron residue (FAC) was tested as a new type of adsorbents to remove the harmful dyes (anionic dye methyl orange (MO) and cationic dye methylene blue (MB)) from contaminated water. Liquid phase adsorption experiments were conducted and the maximum adsorptive capacity was determined. Various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and isotherm constant calculation. It was found that the adsorption capacity of FAC is much higher than those of the other types of activated carbons. Maximum equilibrium adsorption capacities of 934.58 mg/g and 581.40 mg/g for MO and MB were achieved.Three simplified kinetic models including pseudo-first-order, pseudo-second-order and intra-particle diffusion equations were used to investigate the adsorption process.The pseudo-second-order equation was followed for adsorption of MO and MB on FAC. Temperature-dependent adsorption behaviors of MO and MB show that the adsorption is a spontaneous and endothermic process accompanying an entropy increases (the driving force of the adsorption). This work indicates that FAC could be employed as a low cost alternative to commercially available activated carbon in the removal of dyes from wastewater.

Doping of Cu–BTC with a metal Ni(ii) ion plays an important role in the adsorptive removal of congo red dye.

a b s t r a c tLandfill mining is an environmentally-friendly technology that combines the concepts of material recycling and sustainable waste management, and it has received a great deal of worldwide attention because of its significant environmental and economic potential in material recycling, energy recovery, land reclamation and pollution prevention. This work applied a cost-benefit analysis model for assessing the economic feasibility, which is important for promoting landfill mining. The model includes eight indicators of costs and nine indicators of benefits. Four landfill mining scenarios were designed and analyzed based on field data. The economic feasibility of landfill mining was then evaluated by the indicator of net present value (NPV). According to our case study of a typical old landfill mining project in China (Yingchun landfill), rental of excavation and hauling equipment, waste processing and material transportation were the top three costs of landfill mining, accounting for 88.2% of the total cost, and the average cost per unit of stored waste was 12.7 USD ton À1 . The top three benefits of landfill mining were electricity generation by incineration, land reclamation and recycling soil-like materials. The NPV analysis of the four different scenarios indicated that the Yingchun landfill mining project could obtain a net positive benefit varying from 1.92 million USD to 16.63 million USD. However, the NPV was sensitive to the mode of land reuse, the availability of energy recovery facilities and the possibility of obtaining financial support by avoiding post-closure care.