In this work, a chitosan/alginate multilayer film was constructed via layer-by-layer self-assembly and studied by in situ surface plasmon resonance monitoring and contact angle measurements. The results demonstrate that the surface composition of the self-assembled multilayer film can be simply tailored through pH control during the assembly process. The biological property of the assembled film was further characterized via antigen-antibody interactions, showing that the loading capacity of the antibody on the multilayered film and the binding activity of the antigen to the immobilized antibody could be also well-tuned by pH control. This work can provide more scientific insight in the interaction between protein and polymer matrix and render a novel simple approach to build high-performance biointerfaces through pH control for potential applications of highly sensitive immunosensors.

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I ncreasing interest has been given to the wastewater treatment−energy nexus due to the concern on global climate change. As such, various anaerobic processes have been investigated for energy recovery from municipal wastewater in the form of biogas. 1,2 In this viewpoint, we argue that biogas recovery from municipal wastewater through anaerobic processes might not be economically practical and environmentally friendly due to the fact that substantial amount methane is dissolved into treated effluent.Soluble COD in municipal wastewaters often ranges from 100−300 mg/L with an average of 200 mg/L. Theoretically, 0.35 L of methane can be produced from 1 g of bCOD removed. 3 Prvoided the COD removal efficiency is as high as 90%, methane produced is about 63 L/m 3 wastewater, equivalent to about 41 g/m 3 at 30°C. As shown in Figure 1, the solubility of methane at 30°C is about 18.6 g/m 3 . These mean that for anaerobic systems operated at 30°C, theoretically about 45% of methane produced would be present in its dissolved form, which will be higher at lower temperature ( Figure 1). It had been reported that dissolved methane accounted for 50% of total methane generated in an anaerobic MBR operated at 15°C feeding with synthetic wastewater at COD of 440 mg/L. 2 Dissolved methane would lead to reduced energy efficiency of anaerobic process for municipal wastewater treatment, and increasing risk of its release into the environment.Methane is known to be 25 times more powerful than carbon dioxide in terms of the greenhouse effect. 1 Therefore, methods for recovering dissolved methane from treated effluent are urgently needed, otherwise anaerobic processes for municipal wastwater tretament would be in question. For example, if 1 m 3 above municipal wastewater is treated with activated sludge process (AS), the amount of CO 2 produced is about 275 g (1 mol COD equals 1 mol CO 2 ) with 100% COD removal, and equivalent CO 2 from electric consumption of pump for aeration is about 68 g when it is calculated as 20% oxygen utilization efficiency and one kwh electricity produced from coals emits 880 g CO 2 , 5 thus the total amount of CO 2 produced from AS is about 343 g/m 3 . However, the dissolved methane only in anaerobic process would result in 465 g equivalent CO 2 /m 3 (dissolved methane multiple greenhouse gas factor), which is instead larger than that of AS.Although some technical approches for recovery of dissolved methane from treated effluent have been proposed, for example, Figure 1. Methane solubility in water at different temperature and salinity (derived from Yamamoto et al. 4 ). Viewpoint pubs.acs.org/est

CO2 flooding is used extensively as a commercial process for enhanced oil recovery. In this study, the visualization of CO2 flooding in immiscible and miscible displacements in a high-pressure condition was studied using a 400 MHz MRI system. For CO2 immiscible displacement, the phenomenon of CO2 channelling or fingering was obviously due to the difference in fluid viscosities and densities. Thus, the sweep efficiency was small, and the final residual oil saturation was 37.2%. For CO2 miscible displacement, the results showed that pistonlike displacement occurred, and the phenomenon of the miscible regions and CO2 front was obvious. The viscous fingering and gravity override caused by the low viscosity and density of the gas were restrained effectively, and the velocity of the CO2 front was uniform. The sweep efficiency was high, and the final residual oil saturation was 13.5%, indicating that CO2 miscible displacement could recover more oil compared with CO2 immiscible displacement. Finally, the average velocity of the CO2 front was evaluated by analyzing the oil saturation profile. A special core analysis method was applied to in situ oil saturation data to directly evaluate the effect of viscosity, buoyancy, and capillary pressure on CO2 miscible displacement.