Hydroxide Microspheres Research Articles

The effect of spray drying parameters on drying of magnesium silicate hydroxide microspheres

Magnesium hydroxide silicate (MSH), as an antiwear additive for lubricating oil, effectively solves the problem that conventional additives contain chlorine, phosphorus and sulfur, which are harmful to environment. However, it is ineffective to prepare MSH powder by traditional drying combined with mechanical ball milling. So the purpose of this study is to prepare smooth MSH microspheres with controllable particle size and moisture content by adjusting spray drying parameters based on hydrothermal synthetic MSH suspension. Results showed that the particle size of MSH microsphere was reduced from 5.5 ± 2.9 μm to 2.78 ± 1.37 μm, and the moisture content was reduced from 7.3% to 4.43% by decreasing solid-liquid ratios and rotating speed of peristaltic pump, or raising inlet temperature of hot air, flow rate of compressed gas and inlet air. In addition, due to the surface energy difference at the interface between liquid-gas and solid-gas during the drying process, nano flaky MSH continuously moved to the center of the droplet, and the capillary force generated by gaps between MSH nanosheets discharges the moisture in the wet core, so that the MSH nanosheets gather and finally form dense and smooth MSH microspheres.

Design of Defect-Rich MgCo-Layered Double Hydroxide Microspheres as Highly Effective Sulfur Reduction Reaction Electrocatalyst for High-Performance Li-S Batteries

Design of Defect-Rich MgCo-Layered Double Hydroxide Microspheres as Highly Effective Sulfur Reduction Reaction Electrocatalyst for High-Performance Li-S Batteries

Production of MgAl/layered double hydroxide microspheres and investigation of the volumetric heat transfer coefficient in spray drying

Layered Double Hydroxides (LDH) are synthetic materials nanostructured in two dimensions that present positively charged layers with interspersed anions for charge and structure balancing. Being recognized as a promising material for various applications, a complete exploration of its possible attractive properties and its synthesis process is essential. However, drying, a necessary step in the process, is still little studied. This work aimed to produce MgAl–CO3/LDH microspheres and calculate the volumetric heat coefficient in spray drying, evaluating the drying air inlet temperature and the concentration of the feed paste in the dryer. LDH synthesis was carried out using the coprecipitation method, maintaining a 2:1 Mg/Al ratio. The infrared spectra presented the bands characteristic of the hydrotalcite-type material. Through XRD, it was possible to observe that the variation in drying air temperature and feed paste concentration produced LDHs with structural differences. The results obtained for the basal spacing ranged from 7.685 to 7.705 Å. Scanning electron microscopy images confirm the production of LDH microspheres, showing variation in the size of the agglomerates with changes in the feed paste concentration. The volumetric heat transfer coefficient values ranged from 4.31 to 5.36 W m−3 K−1, with only the air inlet temperature significantly influencing the process under the conditions studied.

Design of Defect-Rich MgCo-Layered Double Hydroxide Microspheres as Highly Effective Sulfur Reduction Reaction Electrocatalyst for High-Performance Li-S Batteries

Design of Defect-Rich MgCo-Layered Double Hydroxide Microspheres as Highly Effective Sulfur Reduction Reaction Electrocatalyst for High-Performance Li-S Batteries

Efficient NiFeCr0.1/NF by incorporating chromium to boost OER catalysis

This study developed ternary NiFeCr hydroxide microsphere composites for efficient oxygen evolution reaction (OER) in alkaline water. Compared to binary NiFe composites, the ternary composites exhibited superior electrocatalytic activity. In a 1 M KOH solution, the ternary composite demonstrated a low initial potential of 1.46 V (RHE), and the overpotential is only 268 mV @ 100 mA cm−2. Charge rearrangement due to chromium oxidation helped maintain iron's low oxidation state, preserving OER activity. The redistribution of chromium particles stabilized iron and prevented its dissolution in an alkaline solution. Consequently, the optimized NiFeCr catalyst exhibits excellent stability, with a stability of 200 h at 100 mA cm−2. This study offers a novel approach to designing efficient and stable catalysts for water decomposition.

Construction of core-shell coordination polymers@layered double hydroxides microspheres via ions-exchanging strategy for enhanced supercapacitor performances

Coordination polymers (CPs) are gained numerous investigations due to their structure talents, such as ultrahigh high specific area, abundant pores or channels, and diverse and adjustable composition in energy storage area. However, their application on supercapacitor devices is restricted by low conductivity and lack of stability. In this work, a Co- and benzenetricarboxyl-based CPs (Co-BTC) is selected as precursor, and then used as template to fabricate a layer-double-hydroxide-covered core-shell structure (noted as Co-BTC@LDH) using a cation/anion co-exchanging process. This fine tune nanomaterial is achieved by, which demonstrates a remarkable specific capacitance of 1226 F g−1 at a current density of 1 A g−1, and outstanding ratio performance of maintaining 86.79% initial capacitance even as the current density elevates tenfold to 10 A g−1. Moreover, the as-fabricated asymmetric supercapacitor based on Co-BTC@LDH and active carbon (AC), displays an energy density of 58.70 Wh kg−1 at the power density of 0.36 kW kg−1 and an impressive cycle stability of retaining 98.2 % initial capacity even after 9000 cycles.

Therapeutic potential of luteolin-loaded poly(lactic-co-glycolic acid)/modified magnesium hydroxide microsphere in functional thermosensitive hydrogel for treating neuropathic pain

Neuropathic pain (NP) is a debilitating condition stemming from damage to the somatosensory system frequently caused by nerve injuries or lesions. While existing treatments are widely employed, they often lead to side effects and lack specificity. This study aimed to alleviate NP by developing an innovative sustained-release thermosensitive hydrogel system. The system incorporates hyaluronic acid (HA)/Pluronic F127 injectable hydrogel and bupivacaine (Bup, B) in combination with poly(lactic-co-glycolic acid; PLGA)/modified magnesium hydroxide (MH)/luteolin (Lut; PML) microspheres (PML@B/Gel). The PML@B/Gel was designed for localized and prolonged co-delivery of Bup and Lut as an anesthetic and anti-inflammatory agent, respectively. Our studies demonstrated that PML@B/Gel had exceptional biocompatibility, anti-inflammatory, and antioxidant properties. In addition, it exhibited efficient pain relief in in vitro cellular assays. Moreover, this functional hydrogel showed substantial sustained drug release while diminishing microglial activation. Consequently, it effectively mitigated mechanical allodynia and thermal hyperalgesia in in vivo rat models of chronic constriction injury (CCI). Based on our research findings, PML@B/Gel emerges as a promising therapeutic approach for the protracted treatment of NP.

Chromium hydroxide microsphere synthesis using droplet microfluidics

In this work, a capillary microfluidic platform based on microbore tubes is demonstrated to continuously synthesize chromium hydroxide microspheres with a narrow particle size distribution using sol-gel process. Chromium hydroxide microspheres are later calcined to obtain chromium oxide microspheres. An in-situ mixing technique is utilized to mix the chromium precursor with the gelling agent. The effects of different design (microfluidic junction configuration, size of the microbore tube) and operating variables (continuous to dispersed phase flow rate ratio, flow velocity, residence time) on the average diameter and polydispersity index of microspheres are studied systematically. Microspheres of an average size of 574 μm with polydispersity index of 6.6% could be prepared using a double T-junction at an organic to aqueous (O/A) flow rate ratio of 60 in an 800 µm diameter microbore tube. The detailed analysis of the flow conditions reveals that the regime of drop (of aqueous phase) formation varies between transition and dripping. Finally, a correlation is proposed to predict average diameter of the microspheres based on values of capillary number (Ca) and organic to aqueous (O/A) flow rate ratio.

Controlling Nanosheet Spacing of ZnAl-Layered Double Hydroxide Assemblages for High-Efficiency Hydrogenation of CO2 to Methanol

Three different morphological variations of monodispersed Zn-Al-containing layered double hydroxide (ZnAl-LDH) microspheres were synthesized, with varying degrees of spacing between the nanosheets. The ZnAl-LDH materials were calcined into Zn-Al-containing layered double oxide (ZnAl-LDO) microspheres and loaded with Cu to be used as catalyst candidates for CO2 hydrogenation to methanol under high pressure and constant flow. Two different low-cost facile Cu loading methods were also employed, namely, wet impregnation and ion exchange. The different morphological variations were then evaluated and compared by computational fluid dynamics (CFD) simulation (ANSYS Fluent) as well as the hydrogenation reaction of CO2 to methanol with the purpose of exploring the effect of nanosheet spacing on catalyst performance in terms of the overall catalytic activity and methanol selectivity. The different metal loading methods have also led to different stability results, where there is a slight drop in performance of the incipient wet-impregnated catalyst, while the ion-exchanged catalyst retains much better performance over the same period of 40 h. Based on our simple CFD modeling, an increase in the nanosheet spacing improves convection-driven vortices within the wider channels of the LDH assemblage, with the vortices reaching deeper into the interior core of the microsphere. The simulated vortex phenomena explain the higher catalytic activities observed in our experimental results. This work indicates that catalysts with intricate morphological structure engineering would significantly enhance their catalytic activities.

Novel high-entropy layered double hydroxide microspheres as an effective and durable electrocatalyst for oxygen evolution

High entropy oxygen evolution catalysts with high efficiency and long life.

Ag-modified α-Fe2O3 spherical particles interspersed on hierarchical flower-like NiAl-LDH microspheres with Z-scheme for significantly enhanced CO2 photoreduction into CO

The conversion of carbon dioxide (CO2) into value-added C1 and/or C2 chemicals by photocatalytic technology has been regarded as a “one stone-two birds” solution for environmental degradation and energy shortage. In this work, a novel Z-scheme mechanism photocatalyst of Ag-modified α-Fe2O3 spherical particles interspersed on hierarchical flower-like layered nickel-aluminum hydroxides (NiAl-LDH) microspheres (α-Fe2O3/Ag/NiAl-LDH, designated as FALDH) is successfully prepared by a combined in-situ hydrothermal and grating strategy. As expected, the optimal sample of FALDH-5/10 exhibits significantly enhanced photocatalytic performance for CO2 reduction with a highest CO yield up to 46.7 μmol g−1 under simulated sunlight without any sacrificial reagents and photosensitizers, compared with the pristine NiAl-LDH, binary Ag/NiAl-LDH and α-Fe2O3/NiAl-LDH, as well as surpassing the previously reported LDH-based counterparts. The high activity is ascribed to strong interaction between the NiAl-LDH microspheres and highly-dispersed Ag/α-Fe2O3 particles, boosted CO2 adsorption capacity and optimized bandgap from α-Fe2O3, and increased utilization efficiency of light from Ag. This study offers a new idea for more efficient stimulating the photocatalytic activity of LDHs by the construction of Z-scheme heterojunction with the aid of plasmonic metal(s) for CO2 photoreduction, and is expected to be employed to other photocatalytic applications effectively.

Ultrasound-induced elevation of interlayer spacing and conductivity of CoNi hydroxides for high-performance Ni–Zn batteries

Nickel–zinc (Ni–Zn) batteries hold a lot of promise for energy storage thanks to their high output voltage, plentiful Zn supply, and low toxicity. Achieving the facile preparation of high-performance cathodes at ambient temperature remains a challenge, it is however essential for practical applications. Here, in the present study, an efficient ultrasound-assisted one-step fabrication of CoNi double hydroxide (UA-CoNi DH) microspheres at room temperature that performs well as a cathode for Ni–Zn batteries was proposed. This designed ultrasound-assisted method induces the formation of metal double hydroxide with an elevation of interlayer spacing and bulk conductivity while maintaining the structure features of CoNi DH prepared without ultrasound assistance. As a result, the UA-CoNi DH as an electrode material displays highly enhanced electrochemical properties relative to CoNi DH prepared without ultrasound assistance. Benefitting from the improved performance of our UA-CoNi DH electrode, the Ni–Zn battery with UA-CoNi DH as the cathode (UA-CoNi DH//Zn) delivers a good specific capacity (202.36 mAh/g) and rate performance (70.49% capacity maintained at a 10-fold higher current), presenting more than 71.61% and 21.99% improvement relative to the CoNi DH//Zn battery, respectively. This work offers guidelines for constructing high-performance Ni–Zn battery cathodes in an open environment.

Fabrication of polystyrene/CuO@calcined layered double hydroxide microspheres with high adsorption capacity for Congo red

Adsorption is gaining popularity as an efficient, fast, and low-cost method for the removal of organic dyes in the wastewater treatment. In this work, a novel inorganic-organic adsorbent, polystyrene/CuO/calcined layered double hydroxide (PS/CuO@CLDH) microspheres, was successfully fabricated through the dispersion polymerization method for the efficient removal of Conon red (CR). The structure of the microspheres of products was characterized, and the marked impact of key variables (e.g., adsorbent dosage, pH, contact time, and initial dye concentration) on its adsorption was investigated. PS/CuO@CLDH10 exhibits the highest adsorption capacity compared with other composite materials, in which the adsorption capacity can reach 484.6 mg g−1 when the addition amount is 10 mg. Furthermore, the dynamics and isotherms fit better with the pseudo-second-order and Freundlich model. The adsorption thermodynamic data illustrate that the adsorption process of PS/CuO@CLDH10 on CR is endothermic, spontaneous, and thermodynamically feasible. Moreover, PS/CuO@CLDH10 maintains high removal efficiency and structural composition after four cycles, revealing its excellent recyclability and stability. Therefore, this work provides a novel idea for designing and fabricating inorganic-organic composites for efficient adsorption in wastewater treatment.

Designing hierarchical iron doped nickel-vanadium hydroxide microsphere as an efficient electrocatalyst for oxygen evolution reaction

Exploring highly active and inexpensive electrocatalysts for oxygen evolution reaction (OER) is considered to be one of the preconditions for the development of energy and environment-related technologies. Nickel-based layered double hydroxides (LDHs) are extensively-studied OER electrocatalysts, but they still require relatively high overpotentials to achieve threshold current densities. In this work, iron-doped nickel-vanadium hydroxide microspheres (Fe-doped NiV HMS) were synthesized by doping iron ions into the NiV HMS through a facile cation-exchange method. The Fe-doped NiV HMS are hollow hierarchical structure stacked by high-density perpendicularly-lying nanosheets, which provide enough space for electrolyte penetration and diffusion. Owing to optimized composition and hollow hierarchical structure, the Fe-doped NiV HMS exhibits excellent electrocatalytic performance, which possessed a very low running overpotential (255 mV at 10 mA cm−2) and a smallest Tafel slope (56 mV dec−1) compared with hierarchical NiV HMS toward OER. Electrochemical results and density functional theory (DFT) manifest that Fe doping could regulate the electronic structure of NiV HMS, thus improving its electrical conductivity and electron transfer rate, and thus enhancing its catalytic activity. This research provides a convenient way to prepare Ni-based hydroxides as promising OER catalysts.

Template-free hierarchical trimetallic oxide photocatalyst derived from organically modified ZnCuCo layered double hydroxide

High-performance photocatalysts have considerable potential to address energy and environmental issues. In this study, dodecylbenzenesulfonate (DBS) modified ZnCuCo layered double hydroxide (DBS-ZnCuCo LDH) microspheres were synthesized through the facile template-free hydrothermal method. Subsequently, ZnCuCo mixed-metal oxides (MMOs) with morphological features of the DBS modified LDH, enhanced surface area, increased light absorption and effective charge separation were prepared by the calcination of the as-synthesized LDH at 650 °C. Structural, morphological, and photoelectrochemical properties of ZnCuCo and DBS-ZnCuCo LDHs and the corresponding MMOs (ZnCuCo MMO1 and ZnCuCo MMO2) were investigated. SEM and TEM images revealed that DBS-ZnCuCo LDH and ZnCuCo MMO2 possess 3D flower-like hierarchical morphologies with interlaced petal-like nanosheets. Although ZnCuCo LDH was inactive for photocatalytic H2 production under visible light irradiation, ZnCuCo MMO2 exhibited a high H2 production rate (3700 μmol g−1 h−1), benefiting from the synergy of the ZnO, CuO, and Co3O4. Furthermore, 95% sulfamethazine (SMZ) degradation was obtained after 60 min of photocatalysis, which is considerably higher than the degradation efficiency of ZnCuCo LDH (24%) and ZnCuCo MMO1 (58%). Based on the photoelectrochemical tests, Z-scheme and double charge transfer mechanisms were proposed to explain the enhanced photocatalytic H2 production and degradation of SMZ. Scavenging tests revealed that O2•− radicals were the main reactive species in the photodegradation of SMZ. A possible degradation pathway was proposed based on the detection of intermediate products.

Complete fabrication of a nonenzymatic glucose sensor with a wide linear range for the direct testing of blood samples

A scalable method for the fabrication of a nonenzymatic disposable blood glucose sensor was made possible by preparing large quantities of catalytic materials and using screen-printing technology. The copper-aluminium double hydroxide microspheres were synthesized by urea hydrolysis method using sulfate salts of aluminium and copper at 100 °C for 24 h. Morphological studies revealed the presence of novel coral-like copper-aluminium microspheres. The prepared compound was used for the fabrication of an electrochemical glucose sensor by screen-printing. The sensor tested in 0.15 M NaOH medium showed a sensitivity of 1111.15 ± 7.96 µA mM-1 cm-2, linear response up to 27 mM glucose concentrations and a limit of detection of 17.60 ± 0.13 µM (S/N = 3). In the presence of exogenous and endogenous interfering species, the fabricated sensor was found to be selective towards glucose. A laboratory prototype of the sensor strip was fabricated using a cellulose membrane, hydrophilic membrane, and customized adhesive layers. The prototype was calibrated and tested with whole blood samples and obtained results are highly correlative with the commercial glucose sensor strips. The sensitivity of the prototype was found to be 0.3057 ± 0.02 µA mM−1 cm−2 with a linear range upto 24.44 mM (440 mg dL−1) and a calculated LOD of 0.9873 ± 0.06 mM (17.77 ± 1.11 mg dL−1). The ease of fabrication method and the reliability of the results with real blood samples show the potential of the nonenzymatic blood glucose sensor prototype for industrial fabrication.

Recovery of Palladium and Gold from PGM Ore and Concentrate Leachates Using Fe3O4@SiO2@Mg-Al-LDH Nanocomposite

In this work, we developed a core–shell nanostructured magnetic composite by functionalizing layered double hydroxide (Mg-Al-LDH) microspheres with Fe3O4@SiO2, for the recovery of Au(III) and Pd(II). The magnetic Fe3O4 nanoparticles provided effective magnetic separation of the adsorbent from aqueous solutions. While silica protected the Fe3O4 nanoparticles, increased the adsorption sites and the stability of the material. Finally, Mg-Al-LDH was chosen because of its large anion sorption capacities which lead to the improved adsorption capacity of Fe3O4@SiO2@ Mg-Al-LDH nanocomposite. The morphology and structural composition of the nanocomposite were characterized using various analytical techniques. It was satisfactorily established that silica was coated on iron oxide and layered double hydroxide was immobilized on Fe3O4@SiO2. Parameters affecting adsorption of the composite towards Au(III) and Pd(II), such as effects of sample pH, mass of adsorbent, extraction time, eluent type and concentration were investigated using response methodology based on central composite design. Maximum adsorption capacities of Fe3O4@SiO2@ Mg-Al-LDH for Au(III) and Pd(II) were 289 mg g−1 and 313 mg g−1, respectively. Under optimum conditions, the proposed method displayed good analytical performance suggesting that the adsorbent is a good candidate for quantitative extraction of Au(III) and Pd(II) from secondary sources. Additionally, %recoveries ranging from 85%–99.6% were obtained revealing that Fe3O4@SiO2@ Mg-Al-LDH could selectively extract Au(III) and Pd(II) from leaching solutions of SARM 107 PGM ore and SARM 186 PGM concentrate.

Development of monodisperse porous microspheres of MgAl-layered double hydroxide by droplet coagulation

The present research focuses on the development of porous MgAl-layered double hydroxide microspheres with high sphericity and uniform particle size distribution. This is based on the droplet coagulation technique using alginate biopolymer as a binder. To achieve this, the suspension formulation was systematically optimized based on zeta potential and rheology measurements. The structural, microtextural and porosity characteristics of the MgAl-LDH powder and the corresponding obtained microspheres were investigated by X-ray diffraction, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, optical and scanning electron microscopy, N2 sorption and Hg intrusion characterization techniques. The combination of these techniques allowed us to highlight that this shaping process leads to the production of porous microspheres in which the LDH plate-like particles are held together in a calcium alginate network without altering their structural features. This research opens up new opportunities for the LDH-type materials towards packed bed applications, such as chemical reactors or sorption columns.

Fast removal of Congo red from aqueous solution by adsorption onto micro/nanostructured NiO microspheres

Micro/nanostructured nickel carbonate hydroxide microspheres were synthesized by a ethylene glycol ((CH2OH)2, EG) mediated solvothermal method. The chemical composition of it was determined by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analysis. After calcination, mesoporous micro/nanostructured NiO microspheres with a large surface area of 185.1 m2 g−1 were prepared. The adsorption properties towards Congo red (CR) were revealed. The adsorption of CR was well fitted by the Langmuir model, and the maximum adsorption capacity was 456.8 mg g−1. Kinetic experiment results can be described by the pseudo-second-order model. Furthermore, with the initial concentration of 300 mg L-1 of CR, over 99.41% of CR was removed within 1 min. The calculated thermodynamic parameters including the enthalpy change, change in the free Gibbs energy, entropy change revealed that the adsorption of CR on NiO microspheres was a feasible, spontaneous and endothermic process.

Flower-like NiMn-layered double hydroxide microspheres coated on biomass-derived 3D honeycomb porous carbon for high-energy hybrid supercapacitors

The efficient utilization of composites derived from the renewable biomass resources could provide a cost-effective alternative for supercapacitor applications. Herein, the honeycomb-like porous carbon conductive scaffold was prepared with biomass Chingma Abutilon seeds as the precursor. Subsequently, NiMn-layered double hydroxide (NiMn LDH) microspheres with pseudocapacitive properties were uniformly supported on the as-prepared carbon nanomaterials in the form of nanosheets. Typically, the highly conductive porous carbon skeleton provided more active sites for fast electron transport and might regulate the growth of the nanosheets. Indeed, the optimal CAS30@NiMn LDH material exhibited a large specific capacity of 1719 F g−1 (1 A g−1) and superior rate stability in the three-electrode configuration, which were relatively higher than the values of pure NiMn-LDH. Moreover, the as-assembled hybrid supercapacitor with CAS30@NiMn LDH composite could deliver a high energy density of 95.29 Wh kg−1 and impressive cycle performance (87 % retention after 5000 cycles).