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A Novel Approach for Separation and Recovery of Titanium, Scandium, Iron from Acidic Wastewater and Red Gypsum Utilization
No full textAt present, acidic wastewater is directly neutralized with lime or limestone, which wastes resources such as titanium, scandium, and iron and generates a great deal of solid waste. This study proposes a novel approach for the separation and recovery of titanium, scandium, and iron from acidic wastewater and red gypsum utilization. The recovery efficiency of titanium in acidic wastewater was 97.59% under the molar ratio of titanium dioxide to phosphoric acid of 1:2.2, the reaction temperature of 85 degrees C, and the reaction time of 45 min. The scandium in the filtrate after the recovery of titanium can be finely extracted with P507, and 99.79% scandium can be extracted by single-stage extraction under the P507 concentration of 15%, the phase ratio (O/A) of 1:13, and extraction time of 6 min. In addition, the process of extracting scandium with P507 is an exothermic reaction by thermodynamic analysis. The raffinate after extracting scandium can be used for leaching red gypsum. As a result, calcium sulfate with a purity of 98.34% and whiteness of 94.27% was obtained under the leaching temperature of 60celcius, the leaching time of 30 min, and the ratio of raffinate volume to red gypsum mass (L/S) of 3.5:1. Subsequently, the 97.64% iron in the leaching solution was recovered by the ammonium jarosite precipitation process, and ammonium sulfate with a purity of 99.65% can be obtained. The process can competently be applied to recover titanium, scandium, and iron in acidic wastewater and resource treatment of red gypsum
Vanadium-based catalytic fibers for selective reduction of NO by NH3 and their potential use on co-processing of dust and NOx
No full textThis work is dedicated to fabrication of catalytic fibers for the process of selective catalytic reduction of NOx by NH3 (NH3-SCR). By employing vanadium-titanium as main catalytic components, we investigated the effect of different inorganic supports (glass fiber, aluminum silicate fiber and quartz fiber), preparation methods (a sol-gel method and a hydrothermal method) and loading weight of V2O5 on the NH3-SCR performance of catalytic fibers. The catalytic aluminum silicate fiber with 5% vanadium/titanium ratio prepared by a sol-gel method (denoted as V5Ti/AF) showed the best SCR and mass transfer performance. Characterization results indicated that a relatively large surface area, strong acidity, well-dispersed catalyst particles, and good redox and desorption properties derived from the interaction between catalytic components and supports all contributed to the good performance of V5Ti/AF. The pressure drop of catalytic fibers were measured, and the total pressure drop of catalytic fibers and de-dust ceramic membranes was much lower than previously prepared catalytic ceramic membranes, indicating their potential use in the co-processing of dust and gaseous pollutants
<p>Simultaneously achieving selective catalytic reduction of NOx with NH3 and catalytic oxidation of CO with O-2 over one finely optimized bifunctional catalyst Mn2Cu1Al1Ox at low temperatures</p>
No full textFor coke oven flue gases, the simultaneous removal of NOx and CO pollutants is highly demanded but still re-mains a big challenge. So far there isn't a single efficient catalyst that can simultaneously achieve selective catalytic reduction of NOx by NH3 and the catalytic oxidation of CO to CO2 in the presence of excessive O-2 at low temperatures (180-220 ?). Here, we report a bifunctional catalyst Mn2Cu1Al1Ox that possesses dual active sites and is highly active for both NH3-SCR and CO oxidation reactions under the above mentioned conditions. By tuning the redox properties and surface oxygen vacancies, the optimized Mn2Cu1Al1Ox catalyst achieved high conversions of both NOx and CO in the NH3-NO-CO-O-2 system, with a NOx conversion of 86.8% and a CO conversion of 100% at 200 ?. The active reaction sites and the interaction principal between NH3-SCR and CO oxidation reactions were thoroughly investigated by well-designed experiments, in-situ DRIFTS and DFT calculations. It was revealed that NH3 and CO competed for the same active sites, which significantly influenced the catalytic performance of Mn3Al1Ox and Cu3Al1Ox for CO oxidation reactions. For the bifunctional Mn2Cu1Al1Ox catalyst, CO is more easily adsorbed on the Cu sites, while NH3 is more inclined to adsorb on the Mn sites, which enables both NH3-SCR and CO oxidation reactions to proceed simultaneously on one catalyst. The improvement of CO oxidation performance on Mn2Cu1Al1Ox catalyst is mainly attributed to the reduced Jahn-Teller effect of Cu atoms by doping into Mn3O4, which leads to the lift of d-band center and finally enhances the CO adsorption
Synergistic Effect of TMSPi and FEC in Regulating the Electrode/Electrolyte Interfaces in Nickel-Rich Lithium Metal Batteries
No full textNickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) with respect to Li metal can enhance the energy density of lithium batteries effectively. However, the unstable Li deposition, together with the dissolution and migration of transition metal (TM) ions toward the anode deteriorate the cycle performance of NCM811 parallel to Li battery, especially when commercial carbonate electrolyte is used. Herein, tris(trimethylsilyl)phosphite (TMSPi) and fluoroethylene carbonate (FEC) are used to construct a dual-additive electrolyte, by which both electrodes can be protected. It is found that TMSPi can be preferentially adsorbed on the cathode surface through its strong coordination with Ni4+, playing the role as a HF scavenger and suppressing TM ions dissolution, as well as mitigating the structural degradation of the cathode effectively. When it comes to the lithium anode, the presence of TMSPi may lead to side reactions with Li metal, accompanied by fast dendrite growth. The introduction of FEC could facilitate the formation of stable electrode/electrolyte interfaces on both sides. Particularly, reduce the direct contact between TMSPi and Li anode, thus ameliorate the incompatibility issue. Consequently, the NCM811 parallel to Li cell with dual-additive demonstrates excellent capacity retention of 81.2% after 500 cycles at 1 C rate. As a sharp contrast, it only retains 13.9% in the one with blank electrolyte. The findings of this work provide a new insight into enhancing the cycle performance of NCM811 parallel to Li system via the synergistic effect between additives
<p>PEO-based CO2-philic mixed matrix membranes compromising N-rich ultramicroporous polyaminals for superior CO2 capture</p>
No full textPolymer molecular sieve materials (PMS) are promising porous fillers that can be used to fabricate highperformance gas separation mixed matrix membranes (MMMs) to overcome the inherent trade-off. In this work, a nitrogen-rich ultramicroporous (0.34 nm, 0.50 nm) polyaminal network (PAN-NH2) was introduced into crosslinked PEO polymer to prepare CO2-philic MMMs with superior CO2 capture performance. Due to the synergistical interaction of the dipole-quadrupole and molecular sieving effect, PAN-NH2 demonstrates excellent molecular recognition of CO2. PAN-NH2 can be well dispersed in polymer matrix to achieve good polymer-filler interface compatibility. The incorporation of PAN-NH2 significantly improves the CO2 permeability and selectivity of membranes by increasing the CO2 solubility and providing a selective CO2 transport highway. For instance, the CO2 permeability of mixed gas (15% CO2/85% N-2, 50% CO2/50% CH4) permeation tests for 2.0 wt % PAN-NH2/PEO was increased from 340 Barrer (crosslinked PEO) to 1160 Barrer along with CO2/N-2 selectivity of 73.0 and CO2/CH4 selectivity of 19.7, surpassing the Upper bound (2019) and Upper bound (2008), respectively. The long-time stability of PAN-NH2/PEO MMMs is good, which endow them with great potential in practical CO2 capture. In addition, this work demonstrates the potential of functional ultramicroporous PMS in the preparation of high-performance MMMs for other gas separation processes
Catalytic deoxygenation of carboxyl compounds in the hydrothermal liquefaction crude bio-oil via in-situ hydrogen supply by CuO-CeO2/gamma-Al2O3 catalyst
No full textHydrothermal liquefaction (HTL) has drawn great attention as a potential method to produce bio-oil from biomass waste. However, bio-crude from HTL shows undesired high-oxygen content and needs further deoxygenation upgrading. Herein, stearic acids as a model carboxylic compounds in HTL bio-crude was employed to investigate catalytic deoxygenation performance. Results showed that (CuO)(10)-CeO2/gamma-Al2O3 had the most superior catalytic deoxygenation performance for the stearic acids. The maximum stearic acid conversion rate (96.36%) and total hydrocarbon yield (88.79%) were obtained at 300 degrees C, 12 h, ratio of stearic acid to water 1 : 4. The main catalytic deoxygenation pathways were proposed: carbon monoxide generation (decarbonylation) - in-situ hydrogen generation (water-gas shift) - short-chain fatty acid generation (hydrogenolysis) - n-alkanes generation (decarboxylation, hydrodeoxygenation and hydrogenation). DFT calculation elucidated that CuO-CeO2 reduced the activation energy from 24.8 kcal mol(-1) (vacuum) to 15.0 kcal mol(-1) (catalytic). Thus, deoxygenation via CuO-CeO2/gamma-Al2O3 would be an effective method for upgrading HTL bio-crude
