Effect of endogenous hydrogen utilization on improved methane production in an integrated microbial electrolysis cell and anaerobic digestion： Employing catalyzed stainless steel mesh cathode

Improving the production of methane, while maintaining a significant level of process stability, is the main challenge in the anaerobic digestion process. Recently, microbial electrolysis cell(MEC) has become a promising method for CO_2 reduction produced during anaerobic digestion(AD) and leads to minimize the cost of biogas upgrading technology. In this study, the MEC-AD coupled reactor was used to generate and utilize the endogenous hydrogen by employing biocompatible electrodeposited cobalt-phosphate as catalysts to improve the performance of stainless steel mesh and carbon cloth electrodes. In addition, the modified version of ADM1 model(ADM1 da) was used to simulate the process. The result indicated that the MEC-AD coupled reactor can improve the CH_4 yield and production rate significantly. The CH_4 yield was enhanced with an average of 48% higher than the control. The CH_4 production rate was also increased 1.65 times due to the utilization of endogenous hydrogen.The specific yield, flow rate, content of CH_4, and p H value were the variables that the model was best at predicting(with indexes of agreement: 0.960/0.941, 0.682/0.696, 0.881/0.865, and 0.764/0.743) of the process with SSmeshes 80/SS-meshes 200, respectively. Employing the catalyzed SS mesh cathode, in the MEC-AD coupled reactor, could be an effective approach to generate and facilitate the utilization of endogenous hydrogen in anaerobic digestion of CH_4 production technology, which is a promising and feasible method to scale up to the industrial level.

Catalytic effects of NH4+ on hydrogen evolution and manganese electrodeposition on stainless steel

The effects of(NH4)2SO4 concentration(c((NH4)2SO4))on hydrogen evolution and Mn electrodeposition on stainless steel(SS)in different potential ranges were investigated by linear sweep voltammetry(LSV),electrochemical impedance spectroscopy(EIS),potentiostatic polarization,chronoamperometry,scanning electron microscope(SEM)and X-ray diffraction(XRD)techniques.The results show that the NH4^+discharge reaction(NDR)intensifies the overall hydrogen evolution kinetics,and the NDR is catalyzed by increasing c((NH4)2SO4)and over-potential.The electro-crystallization of Mn on SS follows a three-dimensional progressive nucleation and diffusion-limited growth mechanism.Increasing the over-potential could accelerate the nucleation rate and also cause the decline of the nucleation density.The absorbed Mn^2+preferably discharges at low over-potential.Increasing c((NH4)2SO4)at medium over-potential could improve the current efficiency and produce more block-like grains.The nucleation process is suppressed by increasing c((NH4)2SO4)at high over-potential,at which the formation of columnar grains with higher hydrogen contents becomes prevailing.

Effect of Cr on Characteristic of Rust Layer Formed on Low Alloy Steel in Flow-accelerated Corrosion Environment

The flow-accelerated corrosion experiments were carried out to research the effect of Cr on the rust layers formed on the carbon steel and Cr-containing steel,as well as the structure of rust layer of the two experimental steels.The influence of Cr on the flow-accelerated corrosion resistance and the corrosion morphology of inner rust layer formed on the Cr-containing steel were studied by the methods of polarization curves,scanning electron microscope,transmission electron microscope,and X-ray photoelectron spectroscope.The distribution of Cr and its form of existence in the inner rust layer were analyzed.The results show that corroded mass loss of Cr-containing steel is lower than that of carbon steel and its inner rust layer is compact.Cr exists in the form of Fe2CrO4 and is enriched in the inner rust layer.This concentration could make the inner rust layer exhibit the tendency of amorphous.This phenomenon is related to fine Fe2CrO4.The inner rust layer becomes more compact because of the formation of fine Fe2CrO4,and the protectiveness of inner rust layer could be improved remarkably.