Development of barium@alginate adsorbents for sulfate removal in lithium refining

The demand for lithium has been steadily growing in recent years due to the boom of electric cars.High purity lithium is commonly used in the manufacture of battery grade lithium electrolyte.Sulfate residuals originating from acid leaching of lithium ores must be limited to below 20 mg·L^?1 during refining.There are methods to remove sulfate such as membrane processing and chemical precipitation using barium salts.However,membrane separation is unable to achieve the required purity while chemical precipitation often causes secondary contamination with barium and requires extra filtration processes that lead to increased processing costs.In this study,we developed a polymeric matrix entrapped with barium ions as a novel adsorbent to selectively adsorb sulfate in aqueous solutions.The adsorbent was prepared by dropwise injection method where alginate droplets were crosslinked with barium to form hydrogel microcapsules.In a typical scenario,the microcapsules had a diameter of 3 mm and contained 5 wt-%alginate.The microcapsules could successfully reduce sulfate concentration in a solution from 100 to 16 mg·L^?1,exceeding the removal target.However,the microcapsules were mechanically unstable in the presence of an excess amount of sulfate.Hence,calcium ions were added as a secondary crosslinking agent to improve the integrity of the microcapsules.The two-step Ca/Ba@alginate microcapsules showed an exceptional adsorption performance,reducing the sulfate concentration to as low as 0.02 mg·L^?1.Since the sulfate selective microcapsules can be easily removed from the aqueous system and do not result in secondary barium contamination,these Ca/Ba@alginate adsorbents will find applications in ultra-refining of lithium in industry.     

3D Network nanostructured NiCoP nanosheets supported on N-doped carbon coated Ni foam as a highly active bifunctional electrocatalyst for hydrogen and oxygen evolution reactions

A highly active bi-functional electrocatalyst towards both hydrogen and oxygen evolution reactions is critical for the water splitting. Herein, a self-supported electrode composed of 3D network nanostructured NiCoP nanosheets grown on N-doped carbon coated Ni foam (NiCoP/NF@NC) has been synthesized by a hydrothermal route and a subsequent phosphorization process. As a bifunctional electrocatalyst, the NiCoP/NF@NC electrode needs overpotentials of 31.8 mV for hydrogen evolution reaction and 308.2 mV for oxygen evolution reaction to achieve the current density of 10 mA·cm⁻² in 1 mol·L⁻¹ KOH electrolyte. This is much better than the corresponding monometal catalysts of CoP/NF@NC and NiP/NF@NC owing to the synergistic effect. NiCoP/NF@NC also exhibits low Tafel slope, and excellent long-term stability, which are comparable to the commercial noble catalysts of Pt/C and RuO₂.     

Electrokinetic remediation of copper mine tailings: Implementing bipolar electrodes

Important process parameters to optimize in electrokinetic soil remediation are those influencing remediation time and power consumption since these directly affect the cost of a remediation action. This work shows how the electrokinetic remediation (EKR) process could be improved by implementing bipolar electrodes in the porous material. The bipolar electrodes in EKR meant two improvements: (1) a shorter migration pathway for the contaminant, and (2) an increased electrical conductivity in the remediation system. All together the remediation proceeded faster with lower electrical resistance than in similar experiments but without the bipolar electrodes.The new electrokinetic remediation design was tested on copper mine tailings with different applied electric fields, remediation times and pre-treatment. The results showed that the copper removal was increased from 8% (applying 20 V for 8 days in sulphuric acidified tailings) without bipolar electrodes to 42% when bipolar electrodes were implemented.Furthermore, the results showed that in this system sulphuric acid addition prior to remediation was better than citric acid addition. In addition, applying a too strong electric field (even with bipolar electrodes) could cause a severe polarization (e.g. a high electrical resistance) in the remediation system.     

锌-空气电池电解液Zn2+浓度对析氢过程的影响

水溶液体系的二次金属-空气电池通常具有安全环保的特点,但是充电过程中仍然存在析氢副反应的安全隐患。使用线性电势扫描方法、Tafel极化曲线及极限扩散电流密度参数定量分析了二次锌-空气电池体系电解液中Zn²⁺浓度对析氢反应过程的影响。结果表明,随着电解液中Zn²⁺浓度的提高,析氢过电势逐渐增大,Zn²⁺浓度在6 mol·L^-1 KOH溶液中达到0.4 mol·L^-1时,析氢过电势超过2.42 V,析氢过电势比空白溶液提高1.2 V,并且Tafel极化曲线的截距超过1.5 V,析氢电势达到超高过电势范围。此外,由Zn²⁺提供的极限扩散电流密度提高至8.9 A·cm^-2,所对应的过电势提高700 mV。研究结果对于确立二次锌-空气电池极限充电范围提供定量依据,对电池安全平稳运行具有重要价值。     

Effect of hydrogen peroxide on the destruction of organic contaminants-synergism and inhibition in a continuous-mode photocatalytic reactor

The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO₂-rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-chlorobenzoic acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l⁻¹. Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l⁻¹. Addition of hydrogen peroxide at small concentrations (<2 mmol l⁻¹) had a synergistic effect and increased considerably the rates of photocatalytic reactions. An optimum influent hydrogen peroxide concentration was observed at 1.6 mmol l⁻¹, which caused an increased in the rates of 4-CBA degradation and total organic carbon (TOC) mineralization by 1.72 and 2.13 times, respectively. This corresponded to an optimum oxidant to contaminant molar ratio of 5.33. At higher concentrations, hydrogen peroxide was found to cause an inhibiting effect on the photocatalytic reactions. The synergistic and inhibiting effects of hydrogen peroxide were rationalized based on the reaction rate constants between relevant radical species.     

聚苯胺中间层改性Ti/PbO2电极的制备及其降解性能

引入导电聚合物聚苯胺膜（PANI，polyaniline）对Ti/PbO₂电极进行改性，采用两步电沉积法成功制备出Ti/PANI/PbO₂电极。通过扫描电镜（SEM）、X射线衍射(XRD)、线性伏安扫描(LSV)和交流阻抗(EIS)对制备的电极进行表征，以甲基橙为目标污染物，探讨了PANI的沉积时间对电极性能的影响，并研究了Ti/PANI/PbO₂电极对罗丹明B和4-硝基苯酚的降解性能。结果表明，PANI的引入未影响活性层PbO₂的晶相结构和形貌特征，但显著提高了电极的析氧电位，Ti/PANI/PbO₂的析氧电位可达3.43V。当PANI聚合时间为30min时，电极Ti/PANI-30/PbO₂的电化学性能和电催化降解效果最佳。在电流密度为30mA/cm²、污染物初始浓度为50mg/L、Na₂SO₄浓度为0.1mol/L的实验条件下，反应120min后，Ti/PANI-30/PbO₂对甲基橙、罗丹明B和4-硝基苯酚的去除率分别为99.8%、99.9%和94.0%。     

On the interaction of oxygen with platinum

The cyclic voltammograms were obtained on both bright polycrystalline Pt and Pt---O alloy bead electrodes in both 2 N H₂SO₄ and 1 N HF solutions saturated with purified N₂. The samples were scanned between 0 and 1500 mV vs nhe at rates from 100 to 17 mV s⁻¹. In rigorously purified systems, the chief effect of polarizing Pt above 1 V is the charging of Pt with dissolved oxygen. Such a Pt--- O alloy has different electrochemical properties than Pt. On Pt there are two adsorption and desorption sites for hydrogen and possibly two adsorption sites for sulfate ions. A third hydrogen desorption site exists on Pt---O alloy.     

Hydrogen evolution reaction on smooth tungsten carbide electrodes

The open-circuit potential in H₂-saturated electrolytes, and the kinetics of hydrogen reactions, in particular of hydrogen evolution reaction, on smooth, rotating disc tungsten carbide WC electrode have been investigated, in 0.5 M sulfate solutions of pH 0.3 and 1.85, in the temperature range 30 to 80°C. Anodically activated electrodes were used too.

It was proved that values of the open-circuit potential in the near vicinity of reversible hydrogen electrode potential can be observed, under condition of high purity, and of tight mounting of the sample in the electrode holder.

Two Tafel regions have been observed for hydrogen evolution reaction, both the Tafel slopes having no systematic variation with temperature. In the lower overpotential region the experimental charge transfer coefficient attained the value of 1, when the temperature was increased up to 80°C. It was suggested that the process approached the barrierless form when the temperature was increased.

The mechanism of hydrogen reactions on WC was discussed. It was suggested that the rate of the process is possibly determined by the rates of its two steps simultaneously. The role of pH on the activation process of WC was emphasized, and implications of the hydrogen evolution reaction parameters on the mechanism of this process were pointed out.     

钛白副产硫酸亚铁光芬顿氧化降解甲基橙的研究

以钛白副产硫酸亚铁作为光芬顿的铁源和催化剂,研究了钛白副产硫酸亚铁-过氧化氢体系在紫外光照射条件下对甲基橙的氧化分解作用,并分析了温度、过氧化氢浓度、波长、钛白副产硫酸亚铁浓度和纯硫酸亚铁浓度等因素对甲基橙脱色率的影响。实验结果表明：当温度为35 ℃、过氧化氢浓度为6.4 mmol/L、副产硫酸亚铁浓度为1.0 mmol/L时,在395 nm波长下甲基橙的脱色速率最快,达到100%。在相同条件下,钛白副产硫酸亚铁对甲基橙的脱色效果优于纯硫酸亚铁的效果。因此,以钛白副产硫酸亚铁作为光芬顿催化剂,并以此来催化降解甲基橙,提高了钛白副产硫酸亚铁的资源利用率,拓宽了其资源化利用的途径。     

基于高盐条件下的Bacillus circulans WZ-12 CCTCC M 207006好氧降解氯化碳氢化合物(英文)

A novel saline-tolerant bacterium Bacillus circulans WZ-12 was evaluated for its potential to degrade four chlorinated hydrocarbons under saline conditions.CH2Cl2 was effectively degraded by Bacillus circulans WZ-12 cells in the medium containing NaCl concentrations ranging from 5 g·L-1 to 10 g·L-1,and the maximum degradation efficiency(85%) was achieved at NaCl concentration of 10 g·L-1.Similarly,Bacillus circulans WZ-12 was able to degrade CH2 BrCl,C2H4Cl2,and C2H2Cl2 in the presence of 10 g NaCl per liter within 24 h.Cells of Bacillus circulans WZ-12 grown in minimal salt medium contained low levels of glycine betaine(GB),but GB levels were 3-to 5-fold higher in cells grown in media with high salt.Kinetic analysis revealed that biodegradation of the four chlorinated hydrocarbons was concentration dependent and a linear inverse correlation(R 2-0.85-0.94) was observed between the rate of biodegradation(V) and salt concentration from 5 g·L-1 to 60 g·L-1.The growing cells(in minimal salt medium) degraded approximately 50% of the CH2Cl2 within 24 h,whereas the resting cells(in physiological saline) degraded only 25% of the CH2Cl2 within 24 h and were inactive after 36 h cultivation.Biodegradation could be repeatedly performed for more than 192 h with more than 50% removal efficiency.Bacillus circulans WZ-12 grows well in an aqueous/oil system,hence,it is effective for the treatment of industrial effluents that contain chlorinated hydrocarbons with high salt concentrations.     

Aerobic Biodegradation of Chlorinated Hydrocarbons by Bacillus circulans WZ-12 CCTCC M 207006 under Saline Conditions

A novel saline-tolerant bacterium Bacillus circulans WZ-12 was evaluated for its potential to degrade four chlorinated hydrocarbons under saline conditions. CH₂Cl₂ was effectively degraded by Bacillus circulans WZ-12 cells in the medium containing NaCl concentrations ranging from 5 g·L^-1 to 10 g·L^-1, and the maximum degradation efficiency (85%) was achieved at NaCl concentration of 10 g·L^-1. Similarly, Bacillus circulans WZ-12 was able to degrade CH₂BrCl, C₂H₄Cl₂, and C₂H₂Cl₂ in the presence of 10 g NaCl per liter within 24 h. Cells of Bacillus circulans WZ-12 grown in minimal salt medium contained low levels of glycine betaine (GB), but GB levels were 3- to 5-fold higher in cells grown in media with high salt. Kinetic analysis revealed that biodegradation of the four chlorinated hydrocarbons was concentration dependent and a linear inverse correlation (R² 0.85-0.94) was observed between the rate of biodegradation (V) and salt concentration from 5 g·L^-1 to 60 g·L^-1. The growing cells (in minimal salt medium) degraded approximately 50% of the CH₂Cl₂ within 24 h, whereas the resting cells (in physiological saline) degraded only 25% of the CH₂Cl₂ within 24 h and were inactive after 36 h cultivation. Biodegradation could be repeatedly performed for more than 192 h with more than 50% removal efficiency. Bacillus circulans WZ-12 grows well in an aqueous/oil system, hence, it is effective for the treatment of industrial effluents that contain chlorinated hydrocarbons with high salt concentrations.     

Nickel(II) ion-intercalated MXene membranes for enhanced H2/CO2 separation

Hydrogen fuel has been embraced as a potential long-term solution to the growing demand for clean energy. A membrane-assisted separation is promising in producing high-purity H₂. Molecular sieving membranes (MSMs) are endowed with high gas selectivity and permeability because their well-defined micropores can facilitate molecular exclusion, diffusion, and adsorption. In this work, MXene nanosheets intercalated with Ni²⁺ were assembled to form an MSM supported on Al₂O₃ hollow fiber via a vacuum-assisted filtration and drying process. The prepared membranes showed excellent H₂/CO₂ mixture separation performance at room temperature. Separation factor reached 615 with a hydrogen permeance of 8.35 × 10⁻⁸ mol·m⁻²·s⁻¹·Pa⁻¹. Compared with the original Ti₃C₂T_x/Al₂O₃ hollow fiber membranes, the permeation of hydrogen through the Ni²⁺-Ti₃C₂T_x/Al₂O₃ membrane was considerably increased, stemming from the strong interaction between the negatively charged MXene nanosheets and Ni²⁺. The interlayer spacing of MSMs was tuned by Ni²⁺. During 200-hour testing, the resultant membrane maintained an excellent gas separation without any substantial performance decline. Our results indicate that the Ni²⁺ tailored Ti₃C₂T_x/Al₂O₃ hollow fiber membranes can inspire promising industrial applications.     

氯代有机物污染场地的监控自然衰减修复初探

氯代有机物因其高毒性、高富集性、高环境残留的特点及其“致癌、致畸、致突变”效应被美国环保局(EPA)列为优先控制污染物。氯代有机物污染场地的传统物理、化学、生物修复方式修复费用相对较高,对污染场地周边环境影响较大。监控自然衰减(MNA)是一种国际上应用较广的污染场地修复和管理技术,近年来在我国逐渐得到关注,其利用污染物自身的自然衰减作用达到修复目标,从而降低修复成本,规避工程风险。本文重点介绍监控自然衰减技术,并结合氯代有机物自然衰减过程中的生物降解作用、降解途径与机理、主要降解菌和酶等要素对氯代有机物污染场地实施监控自然衰减修复的可行性进行初步探究。     

Investigation of the hydrogen evolution reaction at a 10 wt% palladium-dispersed carbon electrode using electrochemical impedance spectroscopy

The hydrogen evolution reaction (h.e.r.) at a 10 wt % palladium-dispersed carbon (Pd/C) electrode in 0.1 m NaOH solution has been investigated with reference to that on carbon (Vulcan XC-72) and palladium foil electrodes by analysing the a.c.-impedance spectra combined with cyclic voltammograms. From the coincidence of the maximum charge transfer resistances and the minimum hydrogen evolution resistances for the h.e.r. at the respective electrode potential for the Pd/C, carbon and Pd foil electrodes, it is suggested that the h.e.r. at the Pd/C electrode takes place along with the absorption and diffusion of hydrogen above –1.10 V vs SCE, whereas the former dominates over the latter below –1.10V vs SCE. In the case of the Pd foil electrode the transition of absorption and diffusion to evolution occurs at –0.96V vs SCE. In contrast to the Pd/C and Pd foil electrodes the h.e.r. occurs strongly at the carbon electrode below –1.20V vs SCE. The hydrogen evolution overpotential on the Pd/C electrode is decreased by 0.10 V in comparison to the carbon electrode due to the larger electrochemical active area of the finely dispersed Pd particles.     

Production of renewable fuels by blending bio-oil with alcohols and upgrading under supercritical conditions

The work studied a non-catalytic upgrading of fast pyrolysis bio-oil by blending under supercritical conditions using methanol, ethanol and isopropanol as solvent and hydrogen donor. Characterisation of the bio-oil and the upgraded bio-oils was carried out including moisture content, elemental content, pH, heating value, gas chromatography-mass spectrometry (GCMS), Fourier transform infrared radiation, ¹³C nuclear magnetic resonance spectroscopy, and thermogravimetric analysis to evaluate the effects of blending and supercritical reactions. The GCMS analysis indicated that the supercritical methanol reaction removed the acids in the bio-oil consequently the pH increased from 2.39 in the crude bio-oil to 4.04 after the supercritical methanol reaction. The ester contents increased by 87.49% after the supercritical methanol reaction indicating ester formation could be the major deacidification mechanism for reducing the acidity of the bio-oil and improving its pH value. Simply blending crude bio-oil with isopropanol was effective in increasing the C and H content, reducing the O content and increasing the heating value to 27.55 from 17.51 MJ·kg^‒1 in the crude bio-oil. After the supercritical isopropanol reaction, the heating value of the liquid product slightly further increased to 28.85 MJ·kg^‒1.     

Molecular tailoring to improve polypyrrole hydrogels’ stiffness and electrochemical energy storage capacity

This research looks at ways of tailoring and improving the stiffness of polypyrrole hydrogels for use as flexible supercapacitor electrodes. Molecules providing additional cross-linking between polypyrrole chains are added post-polymerisation but before gelation, and are found to increase gel stiffness by up to 600%, with the degree of change dependent on reactant type and proportion. It was also found that addition of phytic acid led to an increase in pseudocapacitive behaviour of the hydrogel, and thus a maximum specific capacitance of 217.07 F·g⁻¹ could be achieved. This is an increase of 140% compared to pristine polypyrrole hydrogels produced by this method.     

Novel polyethyleneimine/TMC-based nanofiltration membrane prepared on a polydopamine coated substrate

Most commercial NF membranes are negatively charged at the pH range of a typical feed solution. In order to enhance the removal of cations (such as Mg²⁺ or Ca²⁺), we utilized polyethyleneimine (PEI) and trimesoyl chloride (TMC) to perform interfacial polymerization reaction on a polydopamine coated hydrolyzed polyacrylonitrile substrate to obtain a positively charged nanofiltration membrane. Effects of polydopamine coating time, PEI concentration, TMC reaction time and concentration on the membrane physicochemical properties and separation performance were systematically investigated using scanning electron microscopy, streaming potential and water contact angle measurements. The optimal NF membrane showed high rejection for divalent ions (93.6±2.6% for MgSO₄, 92.4±1.3% for MgCl₂, and 90.4±2.1% for Na₂SO₄), accompanied with NaCl rejection of 27.8±2.5% with a permeation flux of 17.2±2.8 L·m⁻²·h⁻¹ at an applied pressure of 8 bar (salt concentrations were all 1000 mg·L⁻¹). The synthesized membranes showed promising potentials for the applications of water softening.     

高活性镍钴铁三元合金电极的制备及析氢性能研究

为进一步提高镍基电极的析氢性能,采用恒电位沉积法,通过改变镀液中各合金的质量浓度比、沉积电位、沉积时间等条件,制备出一种高活性的镍钴铁三元合金电极。通过测定电极在1 mol/L的NaOH溶液中的极化曲线,得到最佳的沉积工艺条件为:36.25 g/L NiSO_4·6H_2O,1.25 g/L NiCl_2·6H_2O,5 g/L CoSO_4·7H_2O,7.5 g/L FeSO_4·7H_2O,10 g/L H_3BO_3,0.5 g/L抗坏血酸,1 g/L十二烷基硫酸钠,pH=4.0,电沉积电位-1.45 V,电沉积时间300 s。阴极极化曲线测试结果表明在5 A/dm^2的条件下,镍钴铁三元合金电极的析氢过电位降低至121 mV,相比于纯镍电极过电位降低近50%,相比于镍钴电极过电位降低近35%。     

过一硫酸盐-高铁酸盐-FeS体系土柱淋洗修复邻二氯苯污染土壤

有机氯污染土壤的修复是目前土壤修复的一个重点和难点。针对有机氯难降解的问题，本文采用土柱淋洗模拟异位淋洗修复的方式，利用过一硫酸盐-高铁酸盐-FeS（PFI）氧化体系对邻二氯苯污染土壤进行了修复。采用土柱实验测试了过一硫酸盐和高铁酸钾的复合溶液在土壤中的渗透系数（1.46×10^-4~2.46×10^-4cm/s），实验发现随氧化物浓度增大，渗透系数变小。使用PFI对污染土壤进行了土柱淋洗修复实验，结果表明，PFI可实现对深层土壤的氧化修复，在适中浓度下经过3.8h淋洗，可将深度为5cm、15cm、25cm处的土壤中的邻二氯苯最终残留率降低为17.5%、20.0%和30.3%。在改变土壤性质方面，土柱实验表明，PFI对土壤性质的改变与土壤深度呈负相关，即土壤越浅，改变得越彻底。综上所述，PFI氧化体系对含氯苯有机污染场地修复有良好的应用前景。     

Formation of dish-like holes and a channel structure in electrodeposition of copper under hydrogen co-deposition

Copper electrodeposition from acid sulfate solutions at an overpotential of 1000 mV, which is about 250 mV outside the plateau of the limiting diffusion current density, was examined by the determination of the average current efficiency of hydrogen evolution and by the scanning electron microscopic (SEM) analysis of the morphology of the formed copper deposits. Craters or holes formed due to the attachment hydrogen bubbles were the dominant morphological forms of copper deposits obtained at this overpotential. In dependence of the concentration of Cu (II) ions in the plating solution, the two types of holes or craters were formed. One type of holes is obtained by electrodeposition from a solution with a concentration of Cu (II) ions of 0.075 M CuSO₄ in 0.50 M H₂SO₄, and a honeycomb-like structure was formed from these holes. The other types of holes are formed from a solution with a higher concentration of Cu (II) ions (0.60 M CuSO₄ in 0.50 M H₂SO₄) and the formed holes were dish-like. A mixture of both types of holes was obtained by electrodeposition from 0.30 M CuSO₄ in 0.50 M H₂SO₄. The obtained morphologies of copper deposits are discussed in terms of the effect of hydrogen evolution on the hydrodynamic conditions in the plating solution.