Zero-valent bimetallic catalyst/absorbent for simultaneous facilitation of MgSO3 oxidation and arsenic uptake

Experimental Study on the Erosion-Corrosion Characteristics of Desulfurization Slurry on Stainless Steel Pipe Materials

The recovery of low-grade waste heat from power plants greatly benefits energy conservation and emission reduction during electricity generation, while the waste heat utilization directly from desulfurization slurry is a significantly promising method to deeply recover such low-grade energy and has been developed in practical application. However, the pipe materials are subjected to erosion and corrosion challenges due to the high level of solid compositions and the presence of harmful ions, such as Cl-1, which requires further evaluation under the condition of slurry heat exchange. The present study aimed at an experimental study on the erosion-corrosion characteristics of desulfurization slurry on three types of stainless steel, including type 304, 316L, and 2205. Both mass loss and micromorphology features were analyzed with possible mechanisms elucidated. The erosion-corrosion rate is weak at low temperatures, while the increase in the slurry temperature clearly promotes its rate. The influence of the temperature on the corrosion resistance of 304 is much greater than that of 2205. With an increase in duration time, the weight loss rate of stainless steel in the desulfurization slurry declines, and the changing trend of metal mass slightly slows down. The present study offers a better understanding of the erosion-corrosion behaviors of three types of stainless steel under flow and heat transfer conditions of a desulfurization slurry.

Use of La-Co@NPC for Sulfite Oxidation and Arsenic Detoxification Removal for High-Quality Sulfur Resources Recovery in Desulfurization Process

Ammonia desulfurization is a typical resource-recovery-type wet desulfurization process that is widely used in coal-fired industrial boilers. However, the sulfur recovery is limited by the low oxidation rate of byproduct (ammonium sulfite), leading to secondary SO2 pollution due to its easy decomposability. In addition, the high toxic arsenic trace substances coexisting in desulfurization liquids also reduce the quality of the final sulfate product, facing with high environmental toxicity. In this study, nitrogen-doped porous carbon coembedded with lanthanum and cobalt (La-Co@NPC) was fabricated with heterologous catalytic active sites (Co0) and adsorption sites (LaOCl) to achieve sulfite oxidation and the efficient removal of high toxic trace arsenic for the recovery of high-value ammonium sulfate from the desulfurization liquid. The La-Co@NPC/S(IV) catalytic system can generate numerous strongly oxidizing free radicals (·SO5- and ·O2-) for the sulfite oxidation on the Co0 site, as well as oxidative detoxification of As(III) into As(V). Subsequently, arsenic can be removed through chemical adsorption on LaOCl adsorption sites. By using the dual-functional La-Co@NPC at a concentration of 0.25 g/L, the rate of ammonium sulfite oxidation reached 0.107 mmol/L·s-1, the arsenic (1 mg/L) removal efficiency reached 92%, and the maximum adsorption capacity of As reached up to 123 mg/g. This study can give certain guiding significance to the functional material design and the coordinated control of multiple coal-fired pollutants in desulfurization for high-value recovery of sulfur resources.

Introducing high-valence molybdenum to stimulate lattice oxygen in a NiCo LDH cathode for chloride ion batteries

Layered double hydroxides (LDHs) have been intensively investigated as promising cathodes for the new concept chloride ion battery (CIB) with multiple advantages of high theoretical energy density, abundant raw materials and unique dendrite-free characteristics. However, driven by the great compositional diversity, a complete understanding of interactions between metal cations, as well as a synergetic effect between metal cations and lattice oxygen on LDH host layers in terms of the reversible Cl-storage capability, is still a crucial but elusive issue. In this work, we synthesized a series of chloride-inserted trinary Mox-doped NiCo2-Cl LDH (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) with gradient oxygen vacancies as enhanced cathodes toward CIBs. The combination of advanced spectroscopic techniques and theoretical calculations reveals that the Mo dopant facilitates oxygen vacancy formation and varies the valence states of coordinated transition metals, which can not only tune the electronic structure effectively and promote Cl-ion diffusion, but improve the redox activity of LDHs. The optimized Mo0.3NiCo2-Cl LDH delivers a reversible discharge capacity of 159.7 mA h g-1 after 300 cycles at 150 mA g-1, which is almost a triple enhancement compared to that of NiCo2Cl LDH. The superior Cl-storage of trinary Mo0.3NiCo2Cl LDH is attributed to the reversible intercalation/deintercalation of chloride ions in the LDH gallery along with the oxidation state changes in Ni0/Ni2+/Ni3+, Co0/Co2+/Co3+ and Mo4+/Mo6+ couples. This simple vacancy engineering strategy provides critical insights into the significance of the chemical interaction of various components on LDH laminates and aims to effectively design more LDH-based cathodes for CIBs, which can even be extended to other halide-ion batteries like fluoride ion batteries and bromide ion batteries.