Enhanced adsorption performance of hierarchical S-doped Ni(OH)<Subscript>2</Subscript> hollow nanocomposites for the removal of Congo red

In this work, nonmetallic S was doped into hierarchical Ni(OH)₂ hollow microspheres by ethanol solvothermal method using thiourea as sulfur source. Although the morphology of precursor Ni(OH)₂ is maintained, the surface states and pore properties had greatly changed after S doping. Using the as-prepared S-doped Ni(OH)₂ as adsorbents for the removal of Congo red (CR), the S-doped Ni(OH)₂ exhibited much better adsorption capacity compared with undoped Ni(OH)₂. The adsorption behavior of both Ni(OH)₂ and S-doped Ni(OH)₂ followed the pseudo-second-order kinetic model and intraparticle diffusion model. The equilibrium data of Ni(OH)₂ could be better fitted by Langmuir model, while Freundlich model could be better used to describe the S-doped Ni(OH)₂ with a much larger adsorption capacity toward CR. The tuned microstructure and changed surface states of adsorbent after S doping may be responsible for the enhanced adsorption performance. Therefore, the doping of S species into hierarchical Ni(OH)₂ paves a new way to tune the microstructure and surface states of Ni-based materials.     

Novel hollow microspheres of hierarchical zinc-aluminum layered double hydroxides and their enhanced adsorption capacity for phosphate in water

Hollow microspheres of hierarchical Zn-Al layered double hydroxides (LDHs) were synthesized by a simple hydrothermal method using urea as precipitating agent. The morphology and microstructure of the as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), nitrogen adsorption-desorption isotherms and fourier transform infrared (FTIR) spectroscopy. It was found that the morphology of hierarchical Zn-Al LDHs can be tuned from irregular platelets to hollow microspheres by simply varying concentrations of urea. The effects of initial phosphate concentration and contact time on phosphate adsorption using various Zn-Al LDHs and their calcined products (LDOs) were investigated from batch tests. Our results indicate that the equilibrium adsorption data were best fitted by Langmuir isothermal model, with the maximum adsorption capacity of 54.1-232 mg/g; adsorption kinetics follows the pseudo-second-order kinetic equation and intra-particle diffusion model. In addition, Zn-Al LDOs are shown to be effective adsorbents for removing phosphate from aqueous solutions due to their hierarchical porous structures and high specific surface areas.     

Microwave-mediated synthesis for improved morphology and pseudocapacitance performance of nickel oxide

Synthetic methods greatly control the structural and functional characteristics of the materials. In this article, porous NiO samples were prepared in conventional-reflux and microwave assisted heating method under homogeneous precipitation conditions. The NiO samples synthesized in conventional reflux method showed flakelike morphology, whereas the sample synthesized in microwave methods showed hierarchical porous ball like surface morphology with uniform ripple-shaped pores. The NiO samples characterized using BET method were found to bear characteristic meso- and macroporosity due to differently crystallized Ni(OH)(2) precursors under various heating conditions. Thermogravimety analysis showed morphology dependent decomposition of Ni(OH)(2) precursors. The microwave synthesized porous NiO sample with unique morphology and pore size distribution showed significantly improved charge storage and electrochemical stability than the flaky NiO sample synthesized by employing conventional reflux method. The cyclic voltammetry measurements on microwave synthesized NiO sample showed considerably high capacitance and better electrochemical reversibility. The charge-discharge measurements made at a discharge current of 2 A/g showed higher rate specific capacitance (370 F/g) for the NiO sample synthesized by microwave method than the sample synthesized by reflux method (101 F/g). The impedance study illustrates lower electronic and ionic resistance of rippled-shaped porous NiO due to its superior surface properties for enhanced electrode-electrolyte contact during the Faradaic redox reactions. It has been further established from the Ragone plot that the microwave synthesized NiO sample shows higher energy and power densities than the reflux synthesized NiO sample. Broadly, this study reveals that microwave-mediated synthesis approach is significantly a better strategy for the synthesis of porous NiO suitable to electrochemical supercapacitor applications.     

A new perspective on carbon nano-onion/nickel hydroxide/oxide composites: Physicochemical properties and application in hybrid electrochemical systems

Carbon nano-onion (CNO) and Ni(OH)₂ or NiO composites were prepared by chemical loading of Ni(OH)₂ on the carbon surface. The samples were characterized by transmission electron microscopic (TEM) and scanning electron microscopic (SEM) methods, powder X-ray diffraction (XRD) technique and by differential-thermogravimetric analyses (TGA-DTG). The porosity properties were characterized by using nitrogen gas adsorption analyses. Pristine inorganic samples of NiO and Ni(OH)₂ revealed different morphologies and porous characteristics when compared to those of the CNO composites, which showed unique electrochemical properties. The electrochemical performance of the CNO/Ni(OH)₂ or CNO/NiO composites is largely affected by the mass, the morphology, the crystal phases of the inorganic component and the distribution of the Ni(OH)₂/NiO phase. The CNO composites were used as materials for hybrid charge-storage devices.     

1D hierarchical CdS NPs/NiO NFs heterostructures with enhanced photocatalytic activity under visible light irradiation

One-dimensional (1D) hierarchically structured CdS nanoparticles (NPs)/NiO nanofibers (NFs) heterostructures with remarkable removal efficiency for diazo dye Congo red (CR) were fabricated by a stepwise synthesis process, which was involved a chemical bathing deposition combined with calcination, and a microwave-assisted wet chemical reaction. The crystal phases, morphologies, optical absorption properties, and adsorption/photocatalytic activity of as-prepared products were investigated by XRD, FESEM, TEM, high-resolution TEM (HRTEM), N₂ adsorption/desorption isotherms, UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum respectively. The experimental results indicated that binary satellite- core CdS NPs/NiO NFs heterojunctions are comprised of n-type CdS NPs with size of 10–30 nm decorated onto 1D p-type NiO NFs with diameter of 60–180 nm and length up to microns, which are self-assembled by nanoparticles with 30–100 nm in size. The possible formation mechanism for satellite-core structured CdS/NiO heterojunction is proposed. Interestingly, the decolorization efficiency over CdS/NiO heterostructures reached up to 91.2% in removal of aqueous CR at high concentration within 40 min under visible light irradiation, which was approximately 5.2 and 3.8 times as high as that of pure CdS nanocrystals (NCs) and the mixture of NiO NFs and CdS NCs. Furthermore, the possible photocatalytic mechanism was also investigated. The as-designed hybrid CdS NPs/NiO NFs heterostructures exhibited improved photocatalytic activity, which is attributed to the enhancement of the visible light adsorption, the efficient separation of photogenerated electrons and holes, and the high adsorption capacity towards CR molecules, thereby displaying superior visible- light-driven photodegradation of CR in high concentration. This work may provide a green engineering heterojunction technology to develop the advanced multifunctional nanocomposites for their applications in wastewater purification.     

一种新型膦酸锆孔材料的合成及其对金属离子的吸附性质

骨架含强配位基的有机无机杂化多级孔材料合成是目前吸附研究的一个重要领域。以bis (hexamethylene) triamino-N, N-bisacetyl-phosphonic acid和ZrOCl₂·8H₂O为原料、应用水热合成技术合成了一种新型膦酸锆多级孔材料ZrPTA, 并通过FT-IR、TGA、XRD、XPS、SEM以及元素分析等手段对制备产物进行了表征。研究结果表明, ZrPTA具有棒状微形貌, 其内部存在大量直径为1.38 nm和1.93 nm的微孔以及直径为2.99 nm的介孔, 其表面积为112.2 m²/g。ZrPTA对水溶液中Pb²⁺、Cu²⁺和Cd²⁺三种金属离子具有良好的吸附作用, 最大吸附量分别为742.7、689.8和627.0 mg/g, 远远高于文献报道值。这一性质使ZrPTA具有潜在的废水处理功效, 显示出诱人的应用前景。     

Batch study of liquid-phase adsorption of methylene blue using cedar sawdust and crushed brick

This paper presents a study on the batch adsorption of basic dye, methylene blue, from aqueous solution (40 mg L(-1)) onto cedar sawdust and crushed brick in order to explore their potential use as low-cost adsorbents for wastewater dye removal. Adsorption isotherms were determined at 20 degrees C and the experimental data obtained were modelled with the Langmuir, Freundlich, Elovich and Temkin isotherm equations. Adsorption kinetic data determined at a temperature of 20 degrees C were modelled using the pseudo-first and pseudo-second-order kinetic equations, liquid-film mass transfer and intra-particle diffusion models. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were represented well by a Langmuir isotherm equation with maximum adsorption capacities of 142.36 and 96.61 mg g(-1) for cedar sawdust and crushed brick, respectively. The second-order model best describes adsorption kinetic data. Analysis of adsorption kinetic results indicated that both film- and particle-diffusion are effective adsorption mechanisms. The Influence of temperature and pH of the solution on adsorption process were also studied. The extent of the dye removal decreased with increasing the solution temperature and optimum pH value for dye adsorption was observed at pH 7 for both adsorbents. The results indicate that cedar sawdust and crushed brick can be attractive options for dye removal from dilute industrial effluents.     

Characteristics of equilibrium, kinetics studies for adsorption of Hg(II), Cu(II), and Ni(II) ions by thiourea-modified magnetic chitosan microspheres

Magnetic chitosan microspheres were prepared and chemically modified with thiourea (TMCS) for adsorption of metal ions. TMCS obtained were investigated by means of X-ray diffraction (XRD), IR, magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of TMCS toward Hg(2+), Cu(2+), and Ni(2+) ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetics was evaluated utilizing the pseudo-first-order, pseudo-second-order, and the intra-particle diffusion models. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 625.2, 66.7, and 15.3mg/g for Hg(2+), Cu(2+), and Ni(2+) ions, respectively. TMCS displayed higher adsorption capacity for Hg(2+) in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded TMCS with were regenerated with an efficiency of greater than 88% using 0.01-0.1M ethylendiamine tetraacetic acid (EDTA).     

Adsorption characteristics of Congo Red onto the chitosan/montmorillonite nanocomposite

A series of biopolymer chitosan/montmorillonite (CTS/MMT) nanocomposites were prepared by controlling the molar ratio of chitosan (CTS) and montmorillonite (MMT). The nanocomposites were characterized by FTIR and XRD. The effects of different molar ratios of CTS and MMT, initial pH value of the dye solution and temperature on adsorption capacities of samples for Congo Red (CR) dye have been investigated. The adsorption capacities of CTS, MMT and CTS/MMT nanocomposite with CTS to MMT molar ratio of 5:1 for CR were compared. The results indicated that the adsorption capacity of CTS/MMT nanocomposite was higher than the mean values of those of CTS and MMT. The adsorption kinetics and isotherms were also studied. It was shown that all the sorption processes were better fitted by pseudo-second-order equation and the Langmuir equation.     

Controllable Synthesis of 3D Ni(OH)2 and NiO Nanowalls on Various Substrates for High‐Performance Nanosensors

Large‐area and uniform three‐dimensional (3D) β‐Ni(OH)₂ and NiO nanowalls were synthesized on a variety of rigid and flexible substrates via a simple aqueous chemical deposition process. The β‐Ni(OH)₂ nanowalls consist of single‐crystal Ni(OH)₂ nanosheets that were vertically grown on different substrates. The height, crystallinity, and morphology of the Ni(OH)₂ nanowalls can be readily modified by adjusting the reaction time and concentration of the NiCl₂ solution. The synthesis mechanism of the Ni(OH)₂ nanowalls was determined through heterogeneous nucleation and subsequent oriented crystal growth. 3D NiO nanowalls were obtained by thermal decomposition of the Ni(OH)₂ nanowalls at 400 °C in Ar atmosphere. Highly sensitive, selective gas sensors and electrochemical sensors based on these NiO nanowalls were developed. The chemiresistive gas sensors based on the NiO nanowalls grown on ceramic substrates exhibited an excellent performance with low detection limit for formaldehyde (8 ppb) and NO₂ (15 ppb). The electrochemical sensor based on the NiO nanowalls grown on an FTO glass substrate had a superior selectivity to non‐enzymatic glucose with a detection limit of 200 nm .     

以玉米衣为模板生物遗态ZnO的制备及Pb2+吸附性能

以玉米衣为模板,利用生物模板法制备了生物遗态多孔ZnO。经过预处理的玉米衣在醋酸锌前驱体溶液中浸渍24h,烘干,800℃煅烧3h得到最终的产物。利用X射线衍射(X-ray)、扫描电镜(SEM)和透射电镜(TEM)对其进行表征,并研究了对铅离子的吸附性能。结果表明:通过原位生长技术,结晶度良好的ZnO晶粒自组装形成表面多孔的类卷叶状生物遗态ZnO;生物遗态ZnO对铅离子有良好的吸附性能,吸附量为49.9mg/g,在120min可基本达到吸附平衡,吸附过程符合准二级动力学模型,吸附等温线拟合结果较为符合Langmuir模型,且升温有利于吸附的进行。     

Simple template-free solution route for the synthesis of Ni(SO(4))(0.3)(OH)(1.4) nanobelts and their thermal degradation

Nanobelts of nickel hydroxyl sulfate have been prepared on a large scale via a simple template-free hydrothermal reaction on the basis of a complex [Ni(NH(3))(6)](2+) formed with Ni(2+) and ammonia in an ethanol-water solution. The as-synthesized nanobelts were single crystals, with several tens of microns in length and 50-150?nm in width. The nanobelts were enclosed by top surfaces (100) and side surfaces (001) and their growth direction was parallel to [010]. The function of aqueous ammonia and ethanol was discussed. Furthermore, nanostructures of a mixture of crystralline NiO and amorphous nickel sulfate with various morphologies, such as nanobelts, porous nanobelts, and nanoparticles, were obtained by the thermal treatment of the as-synthesized Ni(SO(4))(0.3)(OH)(1.4) nanobelts at different temperatures.     

Microwave-assisted hydrothermal synthesis of Ni(OH)2 architectures and their in situ thermal convention to NiO

The Ni(OH)₂ architectures with flower-like morphology assembled from nanosheets have been successfully synthesized through a microwave-assisted hydrothermal method using urea as a hydrolysis-controlling agent and polyethylene glycol (PEG) as a surfactant. The NiO architectures with similar morphology were obtained by a simple thermal decomposition process of the precursor Ni(OH)₂. The as-obtained products were well characterized by XRD, TG-DTA, SEM, TEM, FTIR and UV–Vis. The experimental results shown that flower-like Ni(OH)₂ architectures with a diameter of 2.5–4.0 μm are assembled from nanosheets with a thickness of 10–20 nm and width of 0.5–1.5 μm. The UV–Vis experimental results shown that the absorption edge of the NiO architectures have a blue-shift with the increasing of the calcination temperature.     

基于沉淀转化法制备的纳米NiO混合电容器研究

运用沉淀转化法制备Ni(OH)2超微粉末,并通过热处理得到纳米NiO.利用TG、XRD、TEM、N2吸附,循环伏安和恒流充放电测试对样品进行了分析和表征.结果表明,实验制备的NiO粒径为10nm左右,比表面积达到186.3m2/g,并具有合适的孔径分布,NiO赝电容器的工作电压为0.35V,在电流密度为60mA/g时,其比容达到243F/g.以NiO和中孔活性炭分别作为正极和负极材料组装成NiO-AC混合电容器,混合电容器的工作电压达到1.5V,其能量密度为NiO赝电容器的17.2倍,并具有更好的功率特性.     

分级介孔结构组成的ZnO微球及光催化性能

以硝酸锌、脲素及酒石酸为反应物, 采用水热法制备碱式碳酸锌前驱体微球, 通过煅烧前驱体制备了介孔氧化锌微球。通过扫描电子显微镜(SEM)可以观察到, 氧化锌微球的直径约为2~4 μm, 由大量厚度约为10 nm的介孔纳米片组装而成。X 射线衍射(XRD)和透射电镜(TEM)结果表明: ZnO微球为六方纤锌矿结构, 并结晶较好。比表面积测试(BET)表明ZnO微球为介孔材料, 孔径为20~50 nm, ZnO微球比表面积约为29.8 m²/g。以亚甲基蓝为目标降解物, 对介孔氧化锌微球进行了光催化降解实验。实验结果表明, 所合成的介孔ZnO微球对亚甲基蓝的光催化性能较好。     

Application of maize tassel for the removal of Pb, Se, Sr, U and V from borehole water contaminated with mine wastewater in the presence of alkaline metals

In this study, the removal of Pb(II) from aqueous solutions by tassel powder was studied and optimised. Batch experiments were conducted on simulated solutions using tassel powder adsorbent and the effects of contact time, pH and concentration on the extent of Pb (II) removal was studied. Equilibrium and kinetic models for Pb(II) sorption were developed by considering the effect of contact time and concentration at optimum pH 4 and fixed temperature(25 degrees C). The Freundlich model was found to describe the sorption energetics of Pb(II) on tassel more fully than the Langmuir. A maximum Pb(II) loading capacity of 333.3mg/g on tassel was obtained. The adsorption process could be well described by both the Langmuir and Freundlich isotherms with R(2) values of 0.957 and 0.972, respectively. The kinetic parameters were obtained by fitting data from the effect of contact time on adsorption capacity into the pseudo-first, pseudo-second-order and intra-particle diffusion equations. The kinetics of Pb(II) on tassel surface was well defined using linearity coefficients (R(2)) by pseudo-second-order (0.999), followed by pseudo-first-order (0.795) and lastly intra-particle diffusion (0.6056), respectively. The developed method was then applied to environmental samples taken from borehole waters contaminated with mine wastewater. The removal of Pb (ND-100%), Se (100%), Sr (5.41-59.0%), U (100%) and V (46.1-100%) was attained using tassel. The uptake of the metals from environmental samples was dependent on pH, ionic strength and levels of other competing species.     

Equilibrium and kinetic data and process design for adsorption of Congo Red onto bentonite

The adsorption of Congo Red onto bentonite in a batch adsorber has been studied. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of Congo Red onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. Adsorption of Congo Red onto bentonite followed the Langmuir isotherm. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm.     

Electrochemical properties and controlled-synthesis of hierarchical β-Ni(OH)2 micro-flowers and hollow microspheres

β-Ni(OH)₂ hierarchical micro-flowers, hierarchical hollow microspheres and nanosheets were synthesized via a facile, single-step and selected-control hydrothermal method. Both hierarchical micro-flowers and hierarchical hollow microspheres were built from two-dimensional nanosheets with thickness of 50–100 nm. The as-obtained products were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). It was observed that marked morphological changes in β-Ni(OH)₂ depended on the initial concentrations of Ni²⁺ ions and glycine. A possible growth mechanism was proposed based on experimental results. In addition, the effect of morphology on the electrochemical properties was also investigated. Both hierarchical micro-flowers and hierarchical hollow microspheres exhibited enhanced specific capacity and high-rate discharge ability as compared with pure Ni(OH)₂ nanosheets. Investigations confirmed that hierarchical structures had a pronounced influence upon the electrochemical performance of nickel hydroxide.     

Template-free synthesis of ordered mesoporous NiO/poly(sodium-4-styrene sulfonate) functionalized carbon nanotubes composite for electrochemical capacitors

We report the first example of a practical and efficient template-free strategy for synthesizing ordered mesoporous NiO/poly(sodium-4-styrene sulfonate) (PSS) functionalized carbon nanotubes (FCNTs) composites by calcining a Ni(OH)₂/FCNTs precursor prepared by refluxing an alkaline solution of Ni(NH₃) _x ²⁺ and FCNTs at 97 °C for 1 h. The morphology and structure were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermal decomposition of the precursor results in the formation of ordered mesoporous NiO/FCNTs composite (ca. 48 wt% NiO) with large specific surface area. Due to its enhanced electronic conductivity and hierarchical (meso- and macro-) porosity, composite simultaneously meets the three requirements for energy storage in electrochemical capacitors at high rate, namely, good electron conductivity, highly accessibleelectrochemical surface areas owing to the existence of mesopores, and efficient mass transport from the macropores. Electrochemical data demonstrated that the ordered mesoporous NiO/FCNTs composite is capable of delivering a specific capacitance (SC) of 526 F/g at 1 A/g and a SC of 439 F/g even at 6 A/g, and show a degradation of only ca. 6% in SC after 2000 continuous charge/discharge cycles.      

纤维素-海藻酸钠-海泡石多孔微球的制备及其对亚甲基蓝吸附性能

以微晶纤维素(Microcrystalline cellulose,MCC)和海藻酸钠(Sodium alginate,SA)为网络框架,海泡石(Sepiolite,SEP)为功能单元,采用悬浮液滴法构建纤维素-海藻酸钠-海泡石(MCC-SA-SEP)双网络多孔复合微球。通过SEM和TG对复合微球结构和热稳定性能进行表征,并研究该微球对亚甲基蓝(Methylene blue,MB)水溶液的吸附性能。结果表明,MCC-SA-SEP复合微球呈现三维网络多孔结构,且随着SEP含量的增加热稳定性逐渐提高。吸附结果显示MCC-SA-SEP符合准二级动力学模型和Langmuir等温线,对MB的饱和吸附容量高达333.3 mg/g。经过五次再生循环后,对MB吸附能力仍能维持85.4%,表明该多孔复合微球可以作为一种高效可再生的有机-无机复合吸附剂用于染料废水处理。