The effects of impurities in carbide slag on the morphological evolution of CaCO3 during carbonation.

Carbide slag (CS) is a kind of solid waste generated by the hydrolysis of calcium carbide for acetylene production. Its major component is Ca(OH)2, which shows great potential in CO2 mineralization to produce CaCO3. However, the types of impurities in CS and their mechanisms for inducing the morphological evolution of CaCO3 are still unclear. In this work, the influence of impurities in CS on the morphology evolution of CaCO3 was investigated. The following impurities were identified in the CS: Al2O3, MgO, Fe2O3, SiO2 and CaCO3. Ca(OH)2 was used to study the influence of impurities (Al2O3 and Fe2O3) on the evolution of CaCO3 morphology during CS carbonation. Calcite (CaCO3) was the carbonation product produced during CS carbonation under varying conditions. The morphology of calcite was changed from cubic to rod-shaped, with increasing solid-liquid ratios. Moreover, rod-shaped calcite was converted into irregular particles with increasing CO2 flow rate and stirring speed. Rod-shaped calcite (CaCO3) was formed by CS carbonation at a solid-liquid ratio of 10:100 under a stirring speed of 600 rpm and a CO2 flow rate of 200 ml/min; and spherical calcite was generated during Ca(OH)2 carbonation under the same conditions. Al2O3 impurities had negligible effects on spherical CaCO3 during Ca(OH)2 carbonation. In contrast, rod-shaped CaCO3 was generated by adding 0.13 wt% Fe2O3 particles, similar to the content of Fe2O3 in CS. Rod-shaped calcite was converted into particulate calcite with increasing Fe2O3 content. The surface wettability and surface negative charge of Fe2O3 appeared to be responsible for the formation of rod-shaped CaCO3. This study enhances our understanding and utilization of CS and CO2 reduction and the fabrication of high-value rod-shaped CaCO3.

Enhancing the Startup Rate of Microbial Methanogenic Systems through the Synergy of ß-lactam Antibiotics and Electrolytic Cells.

The slow startup and suboptimal efficiency of microbial carbon sequestration and methane-production systems have not been fully resolved despite their contribution to sustainable energy production and the reduction of greenhouse gas emissions. These systems often grapple with persistent hurdles, including interference from miscellaneous bacteria and the slow enrichment of methanogens. To address these issues, this paper examines the synergistic effect of coupling ß-lactam antibiotics with an electrolytic cell on the methanogenic process. The results indicated that ß-lactam antibiotics exhibited inhibitory effects on Campylobacteria and Alphaproteobacteria (two types of miscellaneous bacteria), reducing their relative abundance by 53.03% and 87.78%, respectively. Nevertheless, it also resulted in a decrease in hydrogenogens and hindered the CO2 reduction pathway. When coupled with an electrolytic cell, sufficient electrons were supplied for CO2 reduction to compensate for the hydrogen deficiency, effectively mitigating the side effects of antibiotics. Consequently, a substantial improvement in methane production was observed, reaching 0.57 mL·L-1·d-1, exemplifying a remarkable 6.3-fold increase over the control group. This discovery reinforces the efficiency of methanogen enrichment and enhances methane-production levels.

Freeing Fluoride Termination of Ti3C2Tx via Electrochemical Etching for High-Performance Capacitive Deionization.

Ti3C2Tx MXene is a promising Faradic capacitive deionization (CDI) electrode for high salt removal in future desalination, whereas the surface termination group of fluoride (-F) significantly impedes ion access to Ti3C2 and charge-transfer efficiency. Herein, we propose an electrochemically etched strategy to synthesize -F-free Ti3C2Tx through three-electrode cyclic voltammetry scanning within a narrowed potential window in an alkaline electrolyte. The resulting assembly of an asymmetric electrochemical-etched Ti3C2Tx//activated carbon CDI device can deliver an excellent salt removal capacity of 20.27 mg·g-1 with an adsorption rate of 1.01 mg g-1 min-1 owing to the enhanced hydrophilicity and ion transport. The tiny CDI device is demonstrated, which can generate an electric current during the electrosorption of salt ions, thus facilitating the powering of a red light-emitting diode. This study opens a new avenue for the surface chemistry of Ti3C2Tx and is expected to achieve future applications in desalination and renewable energy.

Liquid marble-derived solid-liquid hybrid superparticles for CO2 capture.

The design of effective CO2 capture materials is an ongoing challenge. Here we report a concept to overcome current limitations associated with both liquid and solid CO2 capture materials by exploiting a solid-liquid hybrid superparticle (SLHSP). The fabrication of SLHSP involves assembly of hydrophobic silica nanoparticles on the liquid marble surface, and co-assembly of hydrophilic silica nanoparticles and tetraethylenepentamine within the interior of the liquid marble. The strong interfacial adsorption force and the strong interactions between amine and silica are identified to be key elements for high robustness. The developed SLHSPs exhibit excellent CO2 sorption capacity, high sorption rate, long-term stability and reduced amine loss in industrially preferred fixed bed setups. The outstanding performances are attributed to the unique structure which hierarchically organizes the liquid and solid at microscales.

Effect of impure components in flue gas desulfurization (FGD) gypsum on the generation of polymorph CaCO3 during carbonation reaction.

As one of the typical solid-wastes, FGD gypsum usually occupies land and causes resource waste and environmental pollution. Its high content of CaSO4·2H2O shows highly potential in synthesizing CaCO3 by incorporating CO2. Nevertheless, the impurities in FGD gypsum have significant effects on polymorph of CaCO3 and the formation mechanism of CaCO3 polymorph during FGD gypsum carbonation was still unclear. Here, we selected CaSO4·2H2O as model to explore the effects of impurities of muscovite and dolomite in FGD gypsum on polymorph of CaCO3 during carbonation. Results showed that the carbonation products of FGD gypsum are a mixture of vaterite (˜60%) and calcite (˜40%), while only pure vaterite was obtained in CaSO4·2H2O carbonation reaction. Muscovite has negligible effects on obtaining pure vaterite during CaSO4·2H2O carbonation. Interestingly, the content of calcite increases to the maximum value (˜27%) at 1.0 wt% dolomite and then decreases with the increment of dolomite in CaSO4·2H2O carbonation reaction. Correspondingly, vaterite declines first and then increases. Mechanism study shows that hydrophilicity and negative surface charge of dolomite might be the key factors to selectively form calcite during the carbonation of FGD gypsum. These findings might contribute to further utilization of FGD gypsum.

Catalyst-TiO(OH)2 could drastically reduce the energy consumption of CO2 capture.

Implementing Paris Climate Accord is inhibited by the high energy consumption of the state-of-the-art CO2 capture technologies due to the notoriously slow kinetics in CO2 desorption step of CO2 capture. To address the challenge, here we report that nanostructured TiO(OH)2 as a catalyst is capable of drastically increasing the rates of CO2 desorption from spent monoethanolamine (MEA) by over 4500%. This discovery makes CO2 capture successful at much lower temperatures, which not only dramatically reduces energy consumption but also amine losses and prevents emission of carcinogenic amine-decomposition byproducts. The catalytic effect of TiO(OH)2 is observed with Raman characterization. The stabilities of the catalyst and MEA are confirmed with 50 cyclic CO2 sorption and sorption. A possible mechanism is proposed for the TiO(OH)2-catalyzed CO2 capture. TiO(OH)2 could be a key to the future success of Paris Climat e Accord.

Adsorption properties of zeolites synthesized from coal fly ash for Cu (II).

This study explored the hydrothermal synthesis of zeolites in a homogeneous reactor using coal fly ash (CFA) as a raw material via a two-step method at normal pressure. Fourier transform infrared spectroscopy and X-ray powder diffraction analysis showed that the synthetic products has the basic structural unit of microporous zeolite molecular sieves, and consiste of zeolite 4A and zeolite X. The ability of zeolites synthesized from CFAto adsorb Cu(ll) was studied. The optimal conditions for adsorption were as follows: pH 5 and dosage of modified CFA 4g l(-1). The isothermal adsorption of zeolites of Cu(ll) showed that the maximum adsorption quantity ranged from 69.44 (at 20 degrees C) to 140.85 mg g(-1) (at 50 degrees C). Adsorption kinetics analysis showed that chemical adsorption was the rate-controlling step. Apparent activation energy data, however, showed that the process of adsorption of Cu(II) had the features of physical adsorption. Thus, the adsorption process included both chemical and physical adsorption.