Cationic Degree Research Articles

Interdisciplinary Project-Based Learning of Fine Chemical Technology for Applied Chemistry Majors: Preparation of High Cationic Degree Cotton-Based Adsorbent

Interdisciplinary Project-Based Learning of Fine Chemical Technology for Applied Chemistry Majors: Preparation of High Cationic Degree Cotton-Based Adsorbent

N-doped LiNi0.65Co0.15Mn0.2O2 ternary cathode materials for improved electrochemical performance

LiNi0.65Co0.15Mn0.2O2 (NCM) has some advantages of high specific capacity, low cost, and environmental friendliness, but its high nickel content leads to serious cationic mixing and poor cycling and rate performance. The N doping LiNi0.65Co0.15Mn0.2O2 (NCM-x%N) is prepared by co-precipitation method. It is indicated by various representational means that N doping can reduce the particle size, effectively inhibit the cationic mixing degree, and increase lattice spacing. The means can improve the diffusion rate of lithium ions, among which N doping LiNi0.65Co0.15Mn0.2O2 (NCM-3%N) of x = 3 has the best electrochemical performance. After 100 cycles at 0.1C, the specific discharge capacity was 137.8 mA·h·g−1 (85.80 % capacity retention rate), which is 15.87 % higher than other NCM. The magnification performance is tested at 0.1C, 0.2C, 0.5C, 1C, and 2C. After 25 cycles, the capacity retention rate of NCM-3%N was 92.1 %, 11.11 % higher than that of NCM. Reaction kinetics showed that NCM-3%N has a lithium-ion diffusion coefficient that is higher than NCM.

Zwitterionic adsorbents derived from self-Exfoliated ionic covalent organic frameworks for efficient Co-Removal of anionic and cationic radionuclides

Exfoliating Covalent Organic Frameworks (COFs) into few-layer or even monolayer nanosheets not only improves the exposure of active sites and facilitates mass transfer efficiency, but also enhances their solubility or dispersion to achieve solution processability. As the Coulomb repulsion can weaken the stacking interactions, the construction of ionic COFs shows promising prospects for obtaining self-stripping nanosheets, but precisely controlling the self-exfoliated degree remains a challenge. Herein, we found for the first time that varying the number of hydroxyl groups in the building blocks could significantly affect the self-exfoliated degree for ionic COFs, and thus successfully produced a series of ionic COFs with stepwise solubility differences. Interestingly, the trend of self-exfoliated degree and solubility of cationic (EBCOFs) and anionic COFs (SDCOFs) were completely opposite to each other. Mechanistic studies indicated that more hydroxyl groups as electron donating groups increased the electron density of ionic COFs, resulting in a decrease in the Coulomb repulsion of cationic COFs (EBCOFs) but an increase in the Coulomb repulsion of anionic COFs (SDCOFs). Furthermore, in order to achieve the efficient co-removal of anionic and cationic radionuclides, we assembled cationic and anionic COF nanosheets through electrostatic attraction to obtain a novel zwitterionic COF (EB@SD COF) with both anion and cation adsorption sites. Impressively, EB@SD COF demonstrated rapid and efficient co-adsorption of ReO4- (a substitute for TcO4-) and Sr2+ with the maximum adsorption capacities of 117.6 and 122.4 mg/g, respectively. This work not only developed an effective zwitterionic COF adsorbent for the co-removal of radionuclides but also broadened the horizon of preparation methods for self-exfoliated ionic COFs.

Cyanobacterial Ampholyte Hydrogels Developed by the Cationization of Sulfated Polysaccharides and Their Cell-Compatibility.

Sacran is a cyanobacterial supergiant polysaccharide with carboxylate and sulfate groups that exhibits antiallergic and antiinflammatory properties. However, its high anionic functions restrict cell compatibility. Quaternary ammonium groups were substituted to form sacran ampholytes, and the cell compatibility of the cationized sacran hydrogels was evaluated. The cationization process involved the reaction of N-(3-chloro-2-hydroxypropyl)trimethylammonium chloride with the primary amine or hydroxyl groups of sacran. The degree of cationization ranged from 32 to 87% for sugar residues. Hydrogels of sacran ampholytes were prepared by annealing their dried sheets by thermal cross-linking; these hydrogels exhibited anisotropic expansion properties. The water contact angle on the hydrogels decreased from 26.5 to 15.3° with an increase in the degree of cationization, thereby enhancing hydrophilicity. The IC50 values of sacran ampholytes decreased with an increased degree of cationization, resulting in a reduction in cytotoxicity toward the L-929 mouse fibroblast cell line. This reduction was associated with an increase in the cell proliferation density after 3 days of incubation. Scanning electron microscopy images showed fibroblast intercellular connections. Therefore, the sacran ampholyte hydrogel exhibited increased hydrophilicity and cell compatibility, which is beneficial for various biomedical applications.

Exploiting the Mixed Entropy Strategy for the Design of Fast Ion Conductors

AbstractThe inorganic solid‐state electrolytes play a crucial role in all‐solid‐state batteries. The entropy of solid‐state electrolytes has a significant impact on ion transport. It has been reported that ionic conductivity can be enhanced by increasing the entropy by adding multiple atoms to the materials. However, there is a lack of understanding regarding the potential mechanism between entropy and ion transport in the atomic‐level microstructure of materials. Herein, a new point of view is brought up to understand the influence of entropy on lithium ionic conductivity at an atomic level only by adding one element at a time inspired by the diagonal relationship. A series of materials is designed, including Li1.75Zr0.75Ta0.25Cl6, Li1.75Zr0.75Nb0.25Cl6, Li1.75Zr0.75Mo0.25Cl6, and Li1.75Zr0.75W0.25Cl6, with various mixed entropy, directed by diagonal relationship. It reveals that the substitution increases the mixed entropy, alters the disorder degree of cations around lithium ions, and improves ionic conductivity. Highlighting the importance of mixed entropy in ion migration and establishing the close connection between mixed entropy and ion conduction could provide new insights into the design and development of solid‐state electrolytes.

Effects of Ti4+ doping on electrochemical properties of LiNi0.815Co0.15Al0.035O2 cathode materials

The high nickel ternary cathode materials LiNi0.815Co0.15Al0.035O2 (NCA) have been widely used in Li-ion batteries due to their high energy density, low cost, and little environmental pollution. However, it suffers from rapid capacity degradation and poor charging rate. In this work, Ti4+ doping NCA cathode materials are prepared by the high-temperature solid-state method. The results show that 0.5%Ti-NCA has a lower cationic mixing degree and better cycling performance. The capacity retention rate of 100 cycles is 98.91% and 96.59% at current densities of 0.5 C and 1.0 C, respectively. The CV and EIS test results show that 0.5%Ti-NCA has lower polarization and higher lithium ion diffusion coefficient DLi+(8.43×10−14 cm2/S) after 100 cycles, while Pure-NCA only has 6.92×10−15 cm2/S, which effectively enhances the electrochemical properties of NCA cathode materials.

Optimization mechanisms of density and quality factor of Ba(Mg1/3Ta2/3)O3 ceramics by adding CaO–B2O3–ZnO glass

In this study, Ba(Mg1/3Ta2/3)O3 (BMT) ceramics added with different amounts of CaO–B2O3–ZnO (CBZ) glass were prepared through the solid-state sintering route. The sintering behavior, microstructure, phase composition and dielectric properties of the BMT ceramics added with CBZ glass were investigated. The addition of CBZ glass decreased the sintering temperature of BMT ceramics by over 300 °C, resulting in a highly dense microstructure without interacting with the main BMT phase. The lower sintering temperature led to small ceramic grains and caused a decrease in the Q × f value. Prolonging the sintering time improved the ordering degree of cations on the B-site in BMT ceramic, leading to an enhancement in the Q × f value. The BMT ceramic added with 0.4 wt% CBZ glass exhibited excellent microwave dielectric properties: εr = 24.19, Q × f = 115,100 GHz, τf = 9.84 ppm/°C, after sintering at 1400 °C for 12 h.

Study on the structure-activity relationship of cationic polyacrylates for the treatment of oilfield produced water.

Cationic polyacrylates exhibit both reverse demulsification and flotation performance, which can avoid incompatibility between the reverse demulsifier and flotation agent during treatment of produced water from offshore oilfields. In our previous work, the effect of the structure of the cationic unit on the reverse demulsification and flotation performance of cationic polyacrylates was studied. However, the structure-activity relationship of cationic polyacrylates has not been systematically studied. In this study, the relationships between the structure (acrylate type, tertiary amine type, mass ratio of acrylate to tertiary amine, and degree of cationicity), interfacial properties (surface tension, interfacial tension, zeta potential, interfacial elastic modulus, interaction force between oil droplets, and film drainage time of an oil-covered bubble), and reverse demulsification and flotation performance of cationic polyacrylates were investigated. A reduction in the elastic modulus of the oil-water interface was the key factor for good reverse demulsification performance, whereas a decrease in the film drainage time of an oil-covered bubble was the key factor for good flotation performance. Ethyl acrylate (EA) was superior to methyl acrylate (MA), and dimethylaminopropyl methacrylamide (DPM) was superior to dimethylaminoethyl methacrylate (DEM). Increases in the mass ratio of ethyl acrylate to dimethylaminopropyl methacrylamide and the degree of cationicity were beneficial for reducing the elastic modulus of the oil-water interface and the film drainage time of an oil-covered bubble. This is the first time that the structure-property-performance relationship of cationic polyacrylates has been systematically studied. A cationic polyacrylate that exhibited both good reverse demulsification performance and good flotation performance is recommended.

INFUENCE OF ADSORPTION LAYERS OF POLYELECTROLYTES ON THE WETTING AND MODIFICATION OF THE POLYSTYRENE SURFACE

The adsorption of cationic and anionic polyelectrolytes from aqueous solutions on the polystyrene surface was studied by quartz crystal microbalance and contact angle measurements. It is shown that, despite the multilayer nature of adsorption, only a monolayer of polyelectrolyte macromolecules is rmly retained on the polymer surface, and the polystyrene surface is hydrophilized. It is shown that with complete monolayer lling of the surface, the degree of modi cation of the polystyrene surface does not depend on the nature of the studied polyelectrolytes, and the modifying monolayers provide the value of the polystyrene/water interfacial energy, which indicates the potential biocompatibility of the material based on the modi ed polystyrene.

Mössbauer spectral analysis and Rietveld structural refinement for cationic distribution of Cr-Co ferrites

Sol-gel autocombustion was used to prepare Chromium-substituted Cobalt ferrite nanoparticles with the chemical formulas CoCrxFe2-xO4, with x (0.1 to 0.5 in steps of 0.1).The samples were systematically examined for providing information related to their structural aspects X-ray diffractometry and energy dispersive spectrometry and for determination of accurate ionic distribution using Mössbauer spectrometry and Rietveld structural refinement. The patterns obtained from the energy dispersive spectra ensure that the elemental concentrations of the samples match well with the ionic proportions set in the empirical formulae. Cationic distributions were first made by Mössbauer spectral analysis using hyperfine fields and then by Rietveld analysis based on integrated intensity ratios and profile matching. The results of the study are explained in terms of the compositional variations, cationic inversion degree associated with the fine particle nature of the materials and the relevant cationic distributions as a result of chromium substituted cobalt ferrite.

Petrological, Geochemical and Chronological Characteristics of Dolomites in the Permian Maokou Formation and Constraints to the Reservoir Genesis, Central Sichuan Basin, China

The Middle Permian Maokou Formation in the Sichuan Basin has huge resources and is an important target for natural gas exploration. In recent years, significant exploration breakthroughs have been made in the dolomite field of member Mao-2 in central Sichuan, and the gas production of several wells has exceeded 1 × 106 m3/d, indicating promising prospects for exploration. However, the origin of the dolomite reservoir in member Mao-2 remains ambiguous, which restricts the accurate prediction of favorable reservoirs. This study focuses on drilling in the Hechuan area as its research object, by using a detailed description of the cores from member Mao-2 of seven wells; samples were selected for tests of the degree of dolomite cation ordering, stable carbon and oxygen isotopic compositions, strontium isotopic composition, rare earth elements, LA-ICP-MS element mapping and U-Pb dating. It is clarified that: (1) The crystalline dolomite of member Mao-2 in the Hechuan area is the main reservoir rock, and the heterogeneous vugs and fractures are the main reservoir space. The dolomite in member Mao-2 has been characterized by a low degree of cation ordering value (avg. 0.59), with values of δ13C (avg. 3.87‰), δ18O (avg. −7.15‰) and 87Sr/86Sr (avg. 0.707474) having similar geochemical characteristics to Middle Permian seawater; the REEs normalized distribution patterns have similar characteristics to limestone; and the U-Pb age (261.0~262.0 Ma) corresponds to the age in the Capitanian stage of the Permian Guadalupian Series. (2) Petrological studies show that member Mao-2 has vertical karstification zonation characteristics; syngenetic karstification controls the formation of a large-scale fracture-cave system in the phreatic zone; the dolomitization of sediment in the fracture-cave system occurred during the penecontemporaneous period with locally restricted seawater. (3) The main controlling factors of the reservoir were syngenetic karstification, early dolomitization and hydrothermal dissolution related to Emei taphrogenesis. The research results are of great significance for dolomite reservoir prediction; the highlands of paleogeomorphology with syndepositional faults are favorable areas for dolomite reservoirs.

Effect of different production methods on physicochemical properties and adsorption capacities of biochar from sewage sludge and kitchen waste: Mechanism and correlation analysis

Different pyrolysis methods, parameters and feedstocks result in biochars with different properties, structures and removal capacities for heavy metals. However, the role of each property on adsorption capacity and corresponding causal relationships remain unclear. Here, we investigated various physicochemical properties of biochar produced via three different methods and two different feedstocks to clarify influences of biomass sources and pyrolysis processes on biochar properties and its heavy metal adsorption performance. Experimental results showed biochars were more aromatic and contained more functional groups after hydrothermal carbonization, while they had developed pores and higher surface areas produced by anaerobic pyrolysis. The inclusion of oxygen resulted in more complete carbonization and higher CEC biochar. Different biochar properties resulted in different adsorption capacities. Biochar produced by aerobic calcination showed higher adsorption efficiency for Cu and Pb. Correlation analysis proved that pH, cation exchange capacity and degree of carbonization positively affected adsorption, while organic matter content and aromaticity were unfavorable for adsorption. Microstructure and components determined biochar macroscopic properties and ultimate adsorption efficiency for metal ions. This study identifies the degree of correlation and pathways of each property on adsorption, which provides guidance for targeted modification of biochar to enhance its performance in heavy metal removal.

Influence of the cationic degree and molar mass of modified starches on their physicochemical properties and capability to enhance the oil recovery process

Polysaccharides and their derivatives are used as additives in numerous petroleum industrial processes, especially in enhanced oil recovery (EOR). There exists however, a lack of studies concerning how their physicochemical properties affect the oil recovery process. This work presents an investigation of a series of 2-hydroxy-3-(trimethylammonium)propyl starches (HTPS) with different molar masses and cationic degrees that are potentially useful for EOR. It was investigated surface/interfacial tensions, rheological profile, emulsion index and wettability alteration. The results provide experimental evidence that the HTPS intrinsic properties affect the measured properties. The HTPS solution/oil interfacial tension (IFT) ranged from a low value of 19.0 to a high value of 34.0 mN/m and correlates positively with the molar mass of the HTPS. In contrast, the rheological behavior displays correlations with the molar mass and the degree of cationization. Furthermore, the 1 % HTPS solutions presented around 10 % of viscosity increase in comparison to brines typically used in waterflooding. The derivative with a higher molar mass and intermediate degree of cationization (HTPS 2) was more effective in changing the wetting condition of an aged limestone with a wettability alteration index (WAI) of 52 % while the commercial surfactant cetyltrimethylammonium bromide (CTAB) presented a WAI of 32.6 %.

Effects of different modifying agents on the preparation and properties of coagulants derived from excess sludge.

The contents and kinds of oxygen-containing functional groups are very significant when preparing cationic hydrochar coagulants via graft copolymerization. Herein, the hydrothermal conditions to produce sludge-based hydrochar (SBC) precursors were optimized by introducing different kinds and amounts of modifying agents (i.e., HCOOH, citric acid (CA), H2SO4, and H2O2), then the surface properties and flocculation performance of derived cationic coagulants (SBC-g-DMC) were studied. Results showed that the utilization of four modifiers raised the acidic groups on the SBC surface; thereinto, the presence of CA could evidently increase the content of phenolic hydroxyl groups. After DMC monomer grafting, the formed coagulants possess positive zeta potentials over a wide pH range (i.e., 3.0 ~ 11.0), showing a typical cationic property. The grafting ratio and efficiency, as well as the cationic degree of coagulants prepared with different SBC precursors follow a descending order of SBCCA-g-DMC > [Formula: see text]-g-DMC > SBCHCOOH-g-DMC > [Formula: see text]-g-DMC; thus, SBCCA-g-DMC coagulant with the best grafting result shows a superior flocculation performance. When a dosage of 4mg/L was adopted, the average turbidity removal rate of SBCCA-g-DMC could reach up to 94.44%. Meanwhile, due to the possible and robust oxidation with the initiator, H2O2 seems not a perfect modifier for SBC preparation. This study could provide an essential reference for the optimal synthesis of SBC and its based coagulants for organic matter recovery and pollutant removal.

Effect of undercooling on clinopyroxene crystallization in a high K basalt: Implications for magma dynamics at Stromboli volcano

We present undercooling (∆T) experiments aimed at investigating the effect of growth kinetics on the textural and compositional evolution of clinopyroxene crystals growing from a high-K basalt erupted during the 2003 paroxysm of Stromboli volcano (Italy). The experiments were performed at P = 350 MPa, T = 1050–1210 °C, H2Omelt = 0–3 wt%, and fO2 = Ni-NiO + 1.5 buffer. An initial stage of supersaturation was imposed to the melt under nominally anhydrous (∆Tanh = 10–150 °C) and hydrous (∆Thyd = 25–125 °C) conditions. Afterwards, this supersaturation state was mitigated by melt relaxation phenomena over an annealing time of 24 h. Results show that plagioclase is the liquidus mineral phase of the high-K basalt at ∆Tanh = 10 °C and dominates the phase assemblage as the degree of undercooling increases. Conversely, clinopyroxene and spinel co-saturate the melt at ∆Thyd = 25 °C, followed by the subordinate formation of plagioclase. At ∆Tanh/hyd ≤ 50 °C, the textural maturation of clinopyroxene produces polyhedral crystals with {−111} (hourglass) and {hk0} (prism) sectors typical of a layer-by-layer growth mechanism governed by an interface-controlled crystallization regime. At ∆Tanh/hyd ≥ 75 °C, the attainment of dendritic and skeletal morphologies testifies to the establishment of diffusion-limited reactions at the crystal-melt interface. 3D reconstructions of synchrotron radiation X-ray microtomographic data reveal a composite growth history for clinopyroxene crystals obtained at ∆Tanh/hyd ≥ 95 °C. The early stage of melt supersaturation produces rosette-like structures composed of dendritic branches of clinopyroxene radiating from a common spinel grain, which acts as surface for heterogeneous nucleation. As diffusive relaxation phenomena progress over the annealing time, the elongate dendrites that constitute the inner crystal domain are partially infilled by the melt and develop skeletal overgrowths in the outer domain. With the increasing degree of undercooling, TAl and M1Ti cations are progressively incorporated in the lattice site of clinopyroxene at the expense of TSi and M1Mg cations. Because of the effect of H2Omelt on the liquidus depression and melt depolymerization, crystals obtained at ∆Thyd are also more enriched in TAl and M1Ti and depleted in TSi and M1Mg than those growing at ∆Tanh. The emerging picture is that the morphological and geochemical evolution of clinopyroxene is mutually controlled by the combined effects of melt supersaturation and relaxation phenomena. A new empirical relationship based on the cation exchange reactions in the lattice site of clinopyroxene is finally proposed to estimate the degree of undercooling governing the crystallization of augitic phenocrysts erupted during normal and violent explosions at Stromboli.

The Use of a Barley-Based Well to Define Cationic Betaglucan to Study Mammalian Cell Toxicity Associated with Interactions with Biological Structures.

Among potential macromolecule-based pharmaceuticals, polycations seem particularly interesting due to their proven antimicrobial properties and use as vectors in gene therapy. This makes an understanding of the mechanisms of these molecules' interaction with living structures important, so the goal of this paper was to propose and carry out experiments that will allow us to characterize these phenomena. Of particular importance is the question of toxicity of such structures to mammalian cells and, in the work presented here, two lines, normal fibroblasts 3T3-L1 and A549 lung cancer, were used to determine this. In this work, three well-defined cationic derivatives of barley-derived betaglucans obtained in a reaction with glycidyltrimethylammonium chloride (BBGGTMAC) with different degrees of cationization (50, 70, and 100% per one glucose unit) and electrostatic charge were studied. The studies address interactions of these polymers with proteins (bovine serum proteins and BSA), nucleic acids (DNA), glycosaminoglycans (heparin), and biological membranes. The results described in this study make it possible to indicate that toxicity is most strongly influenced by interactions with biological membranes and is closely related to the electrostatic charge of the macromolecule. The presentation of this observation was the goal of this publication. This paper also shows, using fluorescently labeled variants of polymers, the penetration and impact on cell structure (only for the polymer with the highest substitution binding to cell membranes is observed) by using confocal and SEM (for the polymer with the highest degree of substitution, and the appearance of additional structures on the surface of the cell membrane is observed). The labeled polymers are also tools used together with dynamic light scattering and calorimetric titration to study their interaction with other biopolymers. As for the interactions with biological membranes, lipid Langmuir monolayers as model membrane systems were used.

Optimization Conditions to Obtain Cationic Polyacrylamide Emulsion Copolymers with Desired Cationic Degree for Different Wastewater Treatments.

The synthesis of cationic polyacrylamides (CPAMs) with the desired cationic degree and molecular weight is essential for various industries, including wastewater treatment, mining, paper, cosmetic chemistry, and others. Previous studies have already demonstrated methods to optimize synthesis conditions to obtain high-molecular-weight CPAM emulsions and the effects of cationic degrees on flocculation processes. However, the optimization of input parameters to obtain CPAMs with the desired cationic degrees has not been discussed. Traditional optimization methods are time-consuming and costly when it comes to on-site CPAM production because the input parameters of CPAM synthesis are optimized using single-factor experiments. In this study, we utilized the response surface methodology to optimize the synthesis conditions, specifically the monomer concentration, the content of the cationic monomer, and the content of the initiator, to obtain CPAMs with the desired cationic degrees. This approach overcomes the drawbacks of traditional optimization methods. We successfully synthesized three CPAM emulsions with a wide range of cationic degrees: low (21.85%), medium (40.25%), and high (71.17%) levels of cationic degree. The optimized conditions for these CPAMs were as follows: monomer concentration of 25%, content of monomer cation of 22.5%, 44.41%, and 77.61%, respectively, and initiator content of 0.475%, 0.48%, and 0.59%, respectively. The developed models can be utilized to quickly optimize conditions for synthesizing CPAM emulsions with different cationic degrees to meet the demands of wastewater treatment applications. The synthesized CPAM products performed effectively in wastewater treatment, with the treated wastewater meeting the technical regulation parameters. 1H-NMR, FTIR, SEM, BET, dynamic light scattering, and gel permeation chromatography were employed to confirm the structure and surface of the polymers.

Understanding AIE and ACQ phenomenon of organometallic iridium(III) complexes by simple cationization engineering

Understanding the relationship between structure and properties is critical to the development of solid-state luminescence materials with desired characteristics and performance optimization. In this work, we elaborately designed and synthesized a pair of mononuclear iridium(III) complexes with similar structures but different degrees of cationization. [Ir2-f][2PF6] with two counterions is obtained by simple N-methylation of the ancillary ligand of [Ir1-f][PF6] which is a classic cationic iridium(III) complex. Such a tiny modification results in tremendously different optical properties in dilute solutions and powders. [Ir1-f][PF6] exhibits weak light in solution but enhanced emission in solid-state as well as poly(methyl methacrylate) matrix, indicative of its aggregation-induced emission (AIE) activity. On the sharp contrary, [Ir2-f][2PF6] is an aggregation-caused quenching (ACQ) emitter showing strong emission in the isolated state but nearly nonemissive in aggregation states. Benefiting from the appealing characteristics of mechanochromic luminescence and AIE behavior, [Ir1-f][PF6] has been successfully applied in reversible re-writable data recording and cell imaging. These results might provide deep insights into AIE and ACQ phenomenon of iridium(III) complexes and facilitate the development of phosphorescent materials with promising properties.

Preparation of cationic aggregates derived from sewage sludge for efficient capture of organic matter

Capturing the abundant organic matter residing in wastewater can not only reduce the emission of CO2 from the source, but the enriched organics can also be used for anaerobic fermentation to generate and offset energy consumption in wastewater treatment processes. The key is to find or develop low-cost materials that can capture organic matter. Herein, sewage sludge-derived cationic aggregates (SBC-g-DMC) were successfully prepared via a hydrothermal carbonization process coupled with a graft copolymerization reaction for recovering organic matter from wastewater. Based upon preliminary screening of synthesized SBC-g-DMC aggregates regarding grafting rate, cationic degree, and flocculation performance, SBC-g-DMC2.5 aggregate prepared with 60 mg of initiator, DMC-to-SBC mass ratio of 2.5:1, 70 °C, and 2 h of reaction time was selected for further characterization and evaluation. Results showed that SBC-g-DMC2.5 aggregate has a positively-charged surface over a wide pH range of 3–11 and a hierarchical micro-/nano-structure, endowing it with an excellent organic matter capture efficiency (97.2% of pCOD, 68.8% of cCOD, and 71.2% of tCOD). Meanwhile, SBC-g-DMC2.5 exhibits inappreciable trapping ability for the dissolved COD, NH3–N, and PO43−, guaranteeing the regular running of subsequent biological treatment units. Electronic neutralization, adsorption bridging, and sweep coagulation between cationic aggregates surface and organic matter were identified as the primary mechanisms for SBC-g-DMC2.5 to capture organics. This development is expected to provide a theoretical reference for sewage sludge disposal, carbon reduction, and energy recovery during municipal wastewater treatment.

Electrochemical insights into the energy storage mechanism of birnessite in aqueous solutions

The birnessite structure of manganese dioxide makes this compound a promising electrode materials for energy storage devices including, in particular for supercapacitors, thanks to the high theoretical capacitance and pseudocapacitive response of MnO2. The effect of ionic species, in particular alkali cations, on the structure of birnessite has been intensively discussed, however their role on the charge storage mechanism is still controversial. Taking into consideration the solvation/desolvation process of different alkali cations (Li+, Na+, K+ and Cs+), this work unveils relevant new aspects of the pseudocapacitive charge storage mechanism of birnessite. The work also discusses the simultaneous contribution of non-faradaic (double-layer processes) and faradaic redox reactions to the charge storage mechanism based on electrochemical impedance spectroscopy (EIS) analysis. It was found that the relative extension of these processes was dependent on diffusional features related to the cation degree of solvation. Results revealed that the potassium birnessite exhibited an interesting specific capacitance value that reached 175.6 F g−1 at 0.5 A g−1 in a potential window of 0.8 V in 0.5 M Li2SO4. This capacitance value includes a contribution resulting from intercalation/deintercalation of cations in the interlayer region and a larger contribution from the double-layer processes (above 76%). This investigation provides new electrochemical insights on the charge storage of birnessite, highlighting the role of alkali ions intercalation in the interlayer structure of birnessite.