Study on the Adsorption Properties of Oxalic Acid-Modified Cordierite Honeycomb Ceramics for Neutral Red Dyes.

Removal of organic dyes from water by monolithic adsorbents is considered as an efficient and no-secondary pollution method. Herein, for the first time cordierite honeycomb ceramics (COR) treated with oxalic acid (CORA) were synthesized. This CORA exhibits outstanding removal efficiency toward the azo neutral red dyes (NR) from water. After optimizing the reaction conditions, the highest adsorption capacity of 7.35 mg·g-1 and a removal rate of 98.89% could be achieved within 300 min. Furthermore, investigation of the adsorption kinetics indicated this adsorption process could be described as a pseudo-second-order kinetic model with k 2 and q e of 0.0114 g·mg-1·min-1 and 6.94 mg·g-1, respectively. According to the fitting calculation, the adsorption isotherm could also be described as the Freundlich isotherm model. The removal efficiency could be maintained above 50% after 4 cycles, negating the need for toxic organic solvent extraction, offering a method for bringing the technology one step closer to industrial application and giving CORA promising potential in practical water treatment.

Enhanced Electrochemical Performance of LiNi0.5Mn1.5O4 Composite Cathodes for Lithium-Ion Batteries by Selective Doping of K+/Cl- and K+/F.

K+/Cl- and K+/F- co-doped LiNi0.5Mn1.5O4 (LNMO) materials were successfully synthesized via a solid-state method. Structural characterization revealed that both K+/Cl- and K+/F- co-doping reduced the LixNi1-xO impurities and enlarged the lattice parameters compared to those of pure LNMO. Besides this, the K+/F- co-doping decreased the Mn3+ ion content, which could inhibit the Jahn-Teller distortion and was beneficial to the cycling performance. Furthermore, both the K+/Cl- and the K+/F- co-doping reduced the particle size and made the particles more uniform. The K+/Cl- co-doped particles possessed a similar octahedral structure to that of pure LNMO. In contrast, as the K+/F- co-doping amount increased, the crystal structure became a truncated octahedral shape. The Li+ diffusion coefficient calculated from the CV tests showed that both K+/Cl- and K+/F- co-doping facilitated Li+ diffusion in the LNMO. The impedance tests showed that the charge transfer resistances were reduced by the co-doping. These results indicated that both the K+/Cl- and the K+/F- co-doping stabilized the crystal structures, facilitated Li+ diffusion, modified the particle morphologies, and increased the electrochemical kinetics. Benefiting from the unique advantages of the co-doping, the K+/Cl- and K+/F- co-doped samples exhibited improved rate and cycling performances. The K+/Cl- co-doped Li0.97K0.03Ni0.5Mn1.5O3.97Cl0.03 (LNMO-KCl0.03) exhibited the best rate capability with discharge capacities of 116.1, 109.3, and 93.9 mAh g-1 at high C-rates of 5C, 7C, and 10C, respectively. Moreover, the K+/F- co-doped Li0.98K0.02Ni0.5Mn1.5O3.98F0.02 (LNMO-KF0.02) delivered excellent cycling stability, maintaining 85.8% of its initial discharge capacity after circulation for 500 cycles at 5C. Therefore, the K+/Cl- or K+/F- co-doping strategy proposed herein will play a significant role in the further construction of other high-voltage cathodes for high-energy LIBs.

Synthesis and Application of a Phosphorous-Free and Non-Nitrogen Polymer as an Environmentally Friendly Scale Inhibition and Dispersion Agent in Simulated Cooling Water Systems.

A novel phosphorus-free and non-nitrogen scale inhibition and dispersion agent was synthesized from epoxysuccinic acid (ESA), itaconic acid (IA), and sodium methyl propylene sulfonate (SMAS). It was characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and elemental analysis, and its molecular weight and distribution were determined by gel permeation chromatography (GPC). Static experimental methods were used to evaluate the scale inhibition against CaCO3, Ca3(PO4)2, and CaSO4. The dispersion ability was evaluated by measuring the dispersive property of iron oxide. By observing the morphology of the CaCO3 scale, the scale inhibition mechanism was discussed. The results showed that when the ratio of raw materials (ESA/IA/SMAS) was 10:10:5, the scale inhibition rate of CaCO3 and CaSO4 reached 100% with the dosages of 20 and 10 mg/L, respectively. In addition, the scale inhibition rate against Ca3(PO4)2 was up to 96.64% with a dosage of 100 mg/L. The property of dispersing iron oxide exhibited the best results with 50 mg/L of the agent. On the 21st day, the biodegradation rate reached 63.33%. This polymer was an environmentally friendly antiscale and dispersant with good scale inhibition and biodegradability.

Manganese oxide doping carbon aerogels prepared with MnO2 coordinated by N, N - dimethylmethanamide for supercapacitors.

Carbon aerogels with excellent conductive characteristics and high specific capacitance have attracted more and more interests for next-generation energy storage applications. Three-dimensional interconnected Mn2O3/carbon aerogel supercapacitor electrodes are prepared by a novel doping method using MnO2 coordinated by N, N-dimethylmethanamide (DMF). The coordinative MnO2 (DMF/MnO2) plays a key role in the sol-gel process of resorcinol and formaldehyde. The doped carbon aerogels exhibits a high specific surface area of 859 m2 g-1 and a good pore-size distribution of 10-15 nm. All of the doped carbon aerogels exhibit higher specific capacitance than pure carbon aerogels, and the highest specific capacitance (170 F g-1), at current density of 1.0 A g-1, is obtained in Mn-CA-5% when 5 mol% DMF/MnO2 is added to the precursor solution. The specific capacitance is as high as 100 F g-1, at current density of 10.0 A g-1, and 97% of initial capacitance is retained over 1000 cycles at a current density of 5.0 A g-1. The doped carbon aerogels exhibits a high coulombic efficiency (up to 99.8%) and a good rate capability. The corresponding result is due to the novel doping method of DMF/MnO2 addition.

Facile Preparation of Rod-like MnO Nanomixtures via Hydrothermal Approach and Highly Efficient Removal of Methylene Blue for Wastewater Treatment.

In the present study, nanoscale rod-shaped manganese oxide (MnO) mixtures were successfully prepared from graphitic carbon nitride (C3N4) and potassium permanganate (KMnO4) through a hydrothermal method. The as-prepared MnO nanomixtures exhibited high activity in the adsorption and degradation of methylene blue (MB). The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Furthermore, the effects of the dose of MnO nanomixtures, pH of the solution, initial concentration of MB, and the temperature of MB removal in dye adsorption and degradation experiments was investigated. The degradation mechanism of MB upon treatment with MnO nanomixtures and H2O2 was studied and discussed. The results showed that a maximum adsorption capacity of 154 mg g-1 was obtained for a 60 mg L-1 MB solution at pH 9.0 and 25 °C, and the highest MB degradation ratio reached 99.8% under the following optimum conditions: 50 mL of MB solution (20 mg L-1) at room temperature and pH ≈ 8.0 with 7 mg of C, N-doped MnO and 0.5 mL of H2O2.

A Comparison of Electrochemical Performance of Carbon Aerogels with Adsorption Metal Ions for Super Capacitors.

Environmental problems caused by metal ions have caused widespread concern in recent years. In this work, carbon aerogels (CAs) adsorbing different metal ions were prepared. The adsorption performance and kinetics of metal ions (Cu(II), Cr(VI), and Fe(III)) on carbon aerogels were systematically investigated. The results indicated that the maximum adsorption capacity of Cu(II) was 424 mg·g-1 in 600 mg·L-1 copper solution. Adsorption performances of Cu(II), Cr(VI), and Fe(III) on CAs well fitted with a pseudo-second-order kinetic model. The structures and morphologies of metal-containing samples were characterized by scanning electron micrographs (SEM), Energy Dispersive Spectrometer (EDS), transmission electron microscope (TEM), and X-ray diffraction (XRD). The results demonstrated that the texture and electrochemical performance of CAs adsorbing metal ions exhibited a clear change. The specific surface area of CAs for adsorbing copper ions was 450 m²·g-1 and they showed a small average pore diameter (7.16 nm). Furthermore, CAs adsorbing metals could be used for the super capacitor. The specific capacitance of CAs adsorbing copper ions could reach 255 F·g-1 at a current density of 1.0 A·g-1. The CA-Cu electrode materials exhibited excellent reversibility with a cycling efficiency of 97% after 5000 cycles.

Carbon aerogel-based supercapacitors modified by hummers oxidation method.

Carbon aerogels of an inter-connected three-dimensional (3D) structure are a potential carbon material for supercapacitors. We report a new oxidation modification method to prepare a series of modified carbon aerogels (OM-CA) by Hummers oxidation method. Oxidation-modified carbon aerogels (OM-CA) are obtained from carbon aerogel powders oxidized by Hummers method. Sulfuric acid stoichiometry is studied in order to investigate the effect of the surface oxygen group on surface area and electrochemical performance. Additionally, heteroatoms are doped into carbon aerogels in the oxidation process. The effect of heteroatom doping on electrochemical performance as a supercapacitor electrode material is investigated. When the amount of sulfuric acid is 40 wt%, the dopping manganese content is 0.9 mol%, the specific surface area of OM-CA is 450 m2/g, and its specific capacitance is 151 F g-1 at 0.5 A g-1, which is achieved by heteroatom doping and texture properties. In addition, OM-CA composite supercapacitors exhibit a stable cycle life at a current density of 0.5 A g-1 and retain 98.0% of initial capacitance over 500 cycles, and OM-CA-40% still presents a higher capacity, up to 148 F g-1 at 0.5 A g-1. The high specific surface area and specific capacitance suggest the porous carbon material has potential applications in supercapacitors.

Dual-porosity Mn2O3 cubes for highly efficient dye adsorption.

Dual-porosity materials containing both macropores and mesopores are highly desired in many fields. In this work, we prepared dual-porosity Mn2O3 cube materials with large-pore mesopores, in which, macropores are made by using carbon spheres as the hard templates, while the mesopores are produced via a template-free route. The attained dual-porosity Mn2O3 materials have 24nm of large-pore mesopores and 700nm of macropores. Besides, the achieved materials own cubic morphologies with particle sizes as large as 6.0µm, making them separable in the solution by a facile natural sedimentation. Dye adsorption measurements reveal that the dual-porosity materials possess a very high maximum adsorption capacity of 125.6mg/g, much larger than many reported materials. Particularly, the adsorbents can be recycled and the dye removal efficiency can be well maintained at 98% after four cycles. Adsorption isotherm and kinetics show that the Langmuir model and the pseudo-second-order kinetics model can well describe the adsorption process of Congo Red on the dual-porosity Mn2O3 cube materials. In brief, the reported dual-porosity Mn2O3 demonstrates a good example for controlled preparation of dual-porosity materials with large-pore mesopores, and the macropore-mesopore dual-porosity distribution is good for mass transfer in dye adsorption application.