Expression and characterization of a CALB-type lipase from Sporisorium reilianum SRZ2 and its potential in short-chain flavor ester synthesis

A lipase from Sporisorium reilianum SRZ2 (SRL) with 73% amino acid sequence identity to Candida antarctica lipase B (CALB) was cloned and overexpressed in Pichia pastoris. The recombinant SRL showed a preference for short-chain p-nitrophenyl esters. It achieved maximum activity at pH 8.0 and 65°C for p-nitrophenyl hexanoate (C6) with K_m and k_cat/K_m values of 0.14 mmol∙L⁻¹ and 1712 min⁻¹∙mmol∙L₋₁ at 30°C, respectively. SRL displayed excellent thermostability and pH stability, retaining more than 79% of its initial activity after incubation at 60°C for 72 h and 75% at pH 3 to 11 for 72 h. It also maintained most of its activity in the presence of inhibitors and detergents except sodium dodecyl sulfate, and it tolerated organic solvents. SRL was covalently immobilized and successfully used for ethyl hexanoate synthesis in cyclohexane or in a solvent-free system with a high conversion yield (>95%). Furthermore, high conversion yield was also achieved for the synthesis of various short-chain flavor esters when high substrate concentrations of 2 mol∙L⁻¹ were applied. This study indicated that a CALB-type lipase from S. reilianum SRZ2 showed great potential in organic ester synthesis.     

Purification and concentration of gluconic acid from an integrated fermentation and membrane process using response surface optimized conditions

A response surface method was used to optimize the purification and concentration of gluconic acid from fermentation broth using an integrated membrane system. Gluconobacter oxydans was used for the bioconversion of the glucose in sugarcane juice to gluconic acid (concentration 45 g·L^-1) with a yield of 0.9 g·g^-1. The optimum operating conditions, such as trans-membrane pressure (TMP), pH, cross-flow rate (CFR) and initial gluconic acid concentration, were determined using response surface methodology. Five different types of polyamide nanofiltration membranes were screened and the best performing one was then used for downstream purification of gluconic acid in a flat sheet cross-flow membrane module. Under the optimum conditions (TMP=12 bar and CFR=400 L·h^-1), this membrane retained more than 85% of the unconverted glucose from the fermentation broth and had a gluconic acid permeation rate of 88% with a flux of 161 L·m^-2·h^-1. Using response surface methods to optimize this green nanofiltration process is an effective way of controlling the production of gluconic acid so that an efficient separation with high flux is obtained.     

Efficient MgO-doped CaO sorbent pellets for high temperature CO2 capture

Novel MgO-doped CaO sorbent pellets were prepared by gel-casting and wet impregnation. The effect of Na⁺ and MgO on the structure and CO₂ adsorption performance of CaO sorbent pellets was elucidated. MgO-doped CaO sorbent pellets with the diameter range of 0.5-1.5 mm exhibited an excellent capacity for CO₂ adsorption and adsorption rate due to the homogeneous dispersion of MgO in the sorbent pellets and its effects on the physical structure of sorbents. The results show that MgO can effectively inhibit the sintering of CaO and retain the adsorption capacity of sorbents during multiple adsorption-desorption cycles. The presence of mesopores and macropores resulted in appreciable change of volume from CaO (16.7 cm³∙mol⁻¹) to CaCO₃ (36.9 cm³∙mol⁻¹) over repeated operation cycles. Ca2Mg1 sorbent pellets exhibited favorable CO₂ capture capacity (9.49 mmol∙g⁻¹), average adsorption rate (0.32 mmol∙g⁻¹∙min⁻¹) and conversion rate of CaO (74.83%) after 30 cycles.     

Synthesis of graphene oxide nanoribbons/chitosan composite membranes for the removal of uranium from aqueous solutions

In this study, a graphene oxide nanoribbons/chitosan (GONRs/CTS) composite membrane was successfully prepared by encapsulating CTS into GONRs, which were unzipped from multi-walled carbon nanotubes. The GONRs/CTS composite membrane so prepared was characterized using scanning electron microscopy, X-Ray diffraction and Fourier transform infrared spectroscopy. The effects of the experimental conditions such as the pH (2‒7), adsorbent dosage (10‒50 mg), experimental time (5 min–32 h), uranium concentration (25‒300 mg∙L⁻¹), experimental temperature (298 K‒328 K) on the adsorption properties of the composite membrane for the removal of U(VI) were investigated. The results showed that the U(VI) adsorption process of the GONRs/CTS composite membrane was pH-dependent, rapid, spontaneous and endothermic. The adsorption process followed the pseudo-secondary kinetics and Langmuir models. The maximum U(VI) adsorption capacity of the GONRs/CTS composite membrane was calculated to be 320 mg∙g⁻¹. Hence, the GONRs/CTS composite membrane prepared in this study was found to be suitable for separating and recovering uranium from wastewater.     

Preparation and characterization of novel carbon molecular sieve membrane/PSSF composite by pyrolysis method for toluene adsorption

Carbon molecular sieve membrane (CMSM)/paper-like stainless steel fibers (PSSF) has been manufactured by pyrolyzing poly (furfuryl alcohol) (PFA) coated on the metal fibers. PFA was synthesized using oxalic acid dihydrate as a catalyst and coated on microfibers by dip coating method. For the purpose of investigating the effects of final carbonization temperature, the composites were carbonized between 400°C and 800°C under flowing nitrogen. The morphology and microstructure were examined by X-ray diffraction, Fourier transforms infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, N₂ adsorption and desorption, Raman spectra and X-ray photoelectron spectra. The consequences of characterization showed that the CMSM containing mesopores of 3.9 nm were manufactured. The specific surface area of the CMSM/PSSF fabricated in different pyrolysis temperature varies from 26.5 to 169.1 m²∙g⁻¹ and pore volume varies from 0.06 to 0.23 cm³∙g⁻¹. When pyrolysis temperature exceeds 600°C, the specific surface, pore diameter and pore volume decreased as carbonization temperature increased. Besides, the degree of graphitization in carbon matrix increased with rising pyrolysis temperature. Toluene adsorption experiments on different structured fixed bed that was padded by CMSM/PSSF and granular activated carbon (GAC) were conducted. For the sake of comparison, adsorption test was also performed on fixed bed packed with GAC. The experimental results indicated that the rate constant k′ was dramatically increased as the proportion of CMCM/PSSF composites increased on the basis of Yoon-Nelson model, which suggested that structured fixed bed padded with CMSM/PSSF composite offered higher adsorption rate and mass transfer efficiency.     

Interface engineering for enhancing electrocatalytic oxygen evolution reaction of CoS/CeO2 heterostructures

To realize renewable energy conversion,it is important to develop low-cost and high-efficiency electrocatalyst for oxygen evolution reaction.In this communication,a novel bijunction CoS/CeO₂ electrocatalyst grown on carbon cloth is prepared by the interface engineering.The interface engineering of CoS and CeO₂ facilitates a rapid charge transfer from CeO₂ to CoS.Such an electrocatalyst exhibits outstanding electrocatalytic activity with a low overpotential of 311 mV at 10 mA·cm?2 and low Tafel slope of 76.2 mV·dec?1,and is superior to that of CoS(372 mV)and CeO₂(530 mV)counterparts.And it has long-term durability under alkaline media.     

Tuning porosity of coal-derived activated carbons for CO2 adsorption

A simple method was developed to tune the porosity of coal-derived activated carbons, which provided a model adsorbent system to investigate the volumetric CO₂ adsorption performance. Specifically, the method involved the variation of the activation temperature in a K₂CO₃ induced chemical activation process which could yield activated carbons with defined microporous (< 2 nm, including ultra-microporous < 1 nm) and meso-micro-porous structures. CO₂ adsorption isotherms revealed that the microporous activated carbon has the highest measured CO₂ adsorption capacity (6.0 mmol∙g^–1 at 0 °C and 4.1 mmol∙g^–1 at 25 °C), whilst ultra-microporous activated carbon with a high packing density exhibited the highest normalized capacity with respect to packing volume (1.8 mmol∙cm⁻³ at 0 °C and 1.3 mmol∙cm^–3 at 25 °C), which is significant. Both experimental correlation analysis and molecular dynamics simulation demonstrated that (i) volumetric CO₂ adsorption capacity is directly proportional to the ultra-micropore volume, and (ii) an increase in micropore sizes is beneficial to improve the volumetric capacity, but may lead a low CO₂ adsorption density and thus low pore space utilization efficiency. The adsorption experiments on the activated carbons established the criterion for designing CO₂ adsorbents with high volumetric adsorption capacity.     

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.     

Effects of additive NaI on electrodeposition of Al coatings in AlCl3-NaCl-KCl molten salts

Effects of NaI as an additive on electrodeposition of Al coatings in AlCl₃-NaCl-KCl(80-10-10 wt-%)molten salts electrolyte at 150°C were investigated by means of cyclic voltammetry,chronopotentiometry,scanning electron microscopy and X-ray diffraction(XRD).Results reveal that addition of NaI in the electrolyte intensifies cathodic polarization,inhibits growth of Al deposits and increases number density of charged particles.The electrodeposition of Al coatings in the AlCl₃-NaCl-KCl molten salts electrolyte proceeds via three-dimensional instantaneous nucleation which however exhibits irrelevance with NaI.Galvanostatic deposition results indicate that NaI could facilitate the formation of uniform Al deposits.A compact coating consisting of Al deposits with an average particle size of 3μm was obtained at a current density of 50 mA?cm^?2 in AlCl₃-NaCl-KCl molten salts electrolyte with 10 wt-%NaI.XRD analysis confirmed that NaI could contribute to the formation of Al coating with a preferred crystallographic orientation along(220)plane.     

Nickel-carbonate nanowire array: An efficient and durable electrocatalyst for water oxidation under nearly neutral conditions

It is highly attractive but still remains a great challenge to develop an efficient electrocatalyst for oxygen evolution reaction under nearly neutral conditions. In this work, we report the transformation of Ni₃S₂ nanowire array on nickel foam into the amorphous nickel carbonate nanowire array on nickel foam (NiCO₃/NF). The resulting NiCO₃/NF shows high electrocatalytic activity towards water oxidation and affords current density of 50 mA·cm⁻² at overpotential of 395 mV in 1.0 mol·L⁻¹ KHCO₃. Moreover, this NiCO₃/NF is also durable with a long-term electrochemical durability of 60 h. This catalyst electrode achieves a high turnover frequency of 0.21 mol O₂·s⁻¹ at the overpotential of 500 mV.     

Improving the activity and stability of a Pt/C electrocatalyst for direct methanol fuel cells

Ketjen Black (KB) as an electrocatalyst support was treated at 900 °C in the presence of cobalt and nickel nitrates, and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and nitrogen adsorption measurement. The treated KB (T-KB) exhibits better graphitization and a larger mesopore volume than the untreated material. A Pt electrocatalyst supported on T-KB was prepared by a modified polyol process. Cyclic voltammetry and single cell tests show that the Pt/T-KB electrocatalyst exhibits better electrochemical activity and stability than a Pt/KB electrocatalyst.     

Lithium-based draw solute for forward osmosis to treat wastewater discharged from lithium-ion battery manufacturing

As draw solute is the core element of forward osmosis (FO) technology, here Li-Bet-Tf₂N synthesized from a customized ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf₂N]) and Li₂CO₃ recovered from lithium-ion battery (LIB) wastes is proposed as a novel draw solute to treat Li⁺-containing wastewater from LIB manufacturing through FO filtration. Having high dissociation ability and an extended structure, Li-Bet-Tf₂N generates a sufficiently high osmotic pressure to drive the FO filtration efficiently along with insignificant reverse solute diffusion. Li-Bet-Tf₂N produces a water flux of 21.3 L·(m²·h)⁻¹ at 1.0 mol∙L^–1 against deionized water, surpassing conventional NaCl and MgCl₂ draw solutes with a higher water recovery efficiency and a smaller solute loss. Li-Bet-Tf₂N induces a more stable and higher water permeation flux with a 10.0% water flux decline than NaCl and MgCl₂ for which the water fluxes decline 16.7% and 16.4%, respectively, during the treatment of 2000 mg∙L^–1 Li⁺-containing wastewater for 12 h. More remarkably, unlike other draw solutes which require intensive energy input and complicated processes in recycling, Li-Bet-Tf₂N is easily separated from water via solvent extraction. Reproducible results are achieved with the recycled Li-Bet-Tf₂N. Li-Bet-Tf₂N thus demonstrates a novel class of draw solute with great potentials to treat wastewater economically.     

4-Amino-1,8-naphthalimide based fluorescent photoinduced electron transfer (PET) pH sensors as liposomal cellular imaging agents: The effect of substituent patterns on PET directional quenching

Four new fluorescent sensors (1-4) based on the 4-amino-1,8-naphthalimide fluorophores (Naps) have been synthesized based on the classical fluorophore-spacer-receptor model. These four compounds all gave rise to emission bands centred at ca. 535 nm, which were found to be highly pH dependent, the emission being ‘switched on’ in acidic media, while being quenched due to PET from the amino moieties to the excited state of the Nap at more alkaline pH. The luminescent pH dependence for these probes was found to be highly dependent on the substitution on the imide site, as well as the polyamine chain attached to the position 4-amino moiety. In the case of sensor 2 the presence of the 4-amino-aniline dominated the pH dependent quenching. Nevertheless, at higher pH, PET quenching was also found to occur from the polyamine site. Hence, 2 is better described as a receptor₁-spacer₁-fluorophore-spacer₂-receptor₂ system, where the dominant PET process is due to (normally less favourable) ‘directional’ PET quenching from the 4-amino-aniline unit to the Nap site. Similar trends and pH fluorescence dependences were also seen for 3 and 4. These compounds were also tested for their imaging potential and toxicity against HeLa cells (using DRAQ5 as nuclear stain which does now show pH dependent changes in acidic and neutral pH) and the results demonstrated that these compounds have reduced cellular viability at moderately high concentrations (with IC₅₀ values between ca. 8–30 µmol∙L⁻¹), but were found to be suitable for intracellular pH determination at 1 µmol∙L⁻¹concentrations, where no real toxicity was observed. This allowed us to employ these as lysosomal probes at sub-toxic concentrations, where the Nap based emission was found to be pH depended, mirroring that seen in aqueous solution for 1-4, with the main fluorescence changes occurring within acidic to neutral pH.     

Effect of sodium bicarbonate solution on methyltrimethoxysilane-derived silica aerogels dried at ambient pressure

Here we present an economical ambient pressure drying method of preparing monolithic silica aerogels from methyltrimethoxysilane precursor while using sodium bicarbonate solution as the exchanging solvent. We prepared silica aerogels with a density and a specific surface area of 0.053 g∙cm⁻³ and 423 m²∙g⁻¹, respectively. The average pore diameter of silica aerogels is 23 nm as the pore specific volume is 1.11 cm³∙g⁻¹. Further, the contact angle between water droplet and the surface of silica aerogels in specific condition can be as high as 166°, which indicates a super-hydrophobic surface of aerogels.     

Electrochemical characterization of platinum–ruthenium nanoparticles prepared by water-in-oil microemulsion

The synthesis, physical characterization, decontamination and some electrocatalytic properties of PtRu nanoparticles prepared using the microemulsion method are reported. The nanoparticles are synthesized by reduction with sodium borohydride of H₂PtCl₆ and RuCl₃ in a water-in-oil microemulsion of water/polyethylenglycol-dodecylether (BRIJ^® 30)/n-heptane. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive analysis by X-rays (EDAX) experiments were carried out to characterize the single and bimetallic nanoparticles obtained. Cyclic voltammograms (CV) of clean nanoparticles were obtained after a controlled decontamination procedure of their surfaces. CO adsorption–oxidation and methanol electrooxidation were used as test reactions to check the electrocatalytic behaviour of the bimetallic nanoparticles. Pt₈₀Ru₂₀ (nominal atomic composition) nanoparticles are the best electrocatalyst for both CO_ad and methanol oxidation. All these results show that the microemulsion method can be used to produce bimetallic nanoparticles in a very easy way. The method can be very easily scaled-up for industrial use.     

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.     

PEMFC用Pt纳米线阴极催化剂的制备及在电堆中的应用

采用无模板法制备了用于质子交换膜燃料电池（PEMFC）的碳载铂纳米线（Pt NWs/C）阴极催化剂,使用透射电镜（TEM）和X射线衍射图谱技术（XRD）对催化剂的微观结构和形貌进行了表征。研究结果表明,制备的铂催化剂具有纳米线的结构,平均截面直径为（4.0±0.2）nm,线长为15～25 nm。利用循环伏安（CV）法和线性伏安扫描法（LSV）表征催化剂的电化学活性和氧还原反应（ORR）特性,结果表明制备的Pt NWs/C催化剂电化学特性良好。利用Pt NWs/C和Pt/C作为阴极催化剂制备膜电极（MEA）,并进行测试,最大功率密度分别为705.6 mW·cm^-2和674.4 mW·cm^-2。然后以Pt NWs/C和Pt/C为阴极催化剂组装了18片和20片的电堆,并进行性能测试,电堆的最大功率密度分别为409.2 mW·cm^-2和702.7 mW·cm^-2,单电池电压差异系数（C_v）分别为16.1%和4.36%,这表明Pt NWs/C作为阴极催化剂在放大后的膜电极组件（MEA）里表现出较好的催化活性,但与商业催化剂相比其性能与均一性还有待提高。该研究可为Pt NWs/C催化剂放大制备提供依据,同时可为后续的基于Pt NWs/C的电堆的耐久性测试和车载应用奠定基础。     

二氧化铈掺杂中空碳纳米纤维的制备及电化学性能

以葡萄糖为碳源,硝酸铈为铈源,去离子水做溶剂合成前体,使用实验室自制阳极氧化铝模板（anodized aluminum oxide,AAO）作为硬模板,采用真空压力诱导技术将前体注入到AAO的纳米孔道内,热分解合成二氧化铈纳米粒子（CeO₂-NPs）掺杂的中空碳纳米纤维（CeO₂/HCFs）。使用拉曼光谱、电感耦合等离子体质谱（ICP-MS）、透射电镜（TEM）、X射线衍射仪（XRD）、X射线光电子能谱（XPS）对样品进行表征,结果表明,CeO₂/HCFs具有平均直径约为200nm的中空管状结构,具有较好的碳化程度,CeO₂-NPs均匀分布在HCFs中,其晶型为面心立方晶系。通过循环伏安法（CV）与安倍电流-时间法（I-t曲线）技术,研究了支持电解质的pH对检测结果的影响以及CeO₂/HCFs对抗坏血酸的电化学催化性能,实验结果表明支持电解质在pH=4.18时具有最稳定的检测电流,CeO₂/HCFs对抗坏血酸有较高的电化学活性,修饰电极的灵敏度为505.4μA/(cm²·mmol),检出限为0.55μmol/L,线性范围为2.5~8.4mmol/L,具有良好的选择性、稳定性和重现性。该方法快捷、灵敏、稳定、操作简便,具有较大的应用潜力。     

Using ultrasound to improve the sequential post-synthesis modification method for making mesoporous Y zeolites

Mesoporous Y zeolites were prepared by the sequential chemical dealumination (using chelating agents such as ethylenediaminetetraacetic acid, H₄EDTA, and citric acid aqueous solutions) and alkaline desilication (using sodium hydroxide, NaOH, aqueous solutions) treatments. Specifically, the ultrasound-assisted alkaline treatment (i.e., ultrasonic treatment) was proposed as the alternative to conventional alkaline treatments which are performed under hydrothermal conditions. In comparison with the hydrothermal alkaline treatment, the ultrasonic treatment showed the comparatively enhanced efficiency (with the reduced treatment time, i.e., 5 min vs. 30 min, all with 0.2 mol·L⁻¹ NaOH at 65°C) in treating the dealuminated Y zeolites for creating mesoporosity. For example, after the treatment of a dealuminated zeolite Y (using 0.1 mol·L⁻¹ H₄EDTA at 100°C for 6 h), the ultrasonic treatment produced the mesoporous zeolite Y with the specific external surface area (S_external) of 160 m²·g⁻¹ and mesopore volume (V_meso) of 0.22 cm³·g⁻¹, being slightly higher than that by the conventional method (i.e., S_external = 128 m²·g⁻¹ and V_meso = 0.19 cm³·g⁻¹). The acidic property and catalytic activity (in catalytic cracking of n-octane) of mesoporous Y zeolites obtained by the two methods were comparable. The ultrasonic desilication treatment was found to be generic, also being effective to treat the dealuminated Y zeolites by citric acid. Additionally, the first step of chemical dealumination treatment was crucial to enable the effective creation of mesopores in the parent Y zeolite (with a silicon-to-aluminium ratio, Si/Al= 2.6) regardless of the subsequent alkaline desilication treatment (i.e., ultrasonic or hydrothermal). Therefore, appropriate selection of the condition of the chemical dealumination treatment based on the property of parent zeolites, such as Si/Al ratio and crystallinity, is important for making mesoporous zeolites effectively.     

Fe2Mo3O8 nanoparticles self-assembling 3D mesoporous hollow spheres toward superior lithium storage properties

Unique self-assembled iron(II)molybdenum(IV)oxide(Fe₂Mo₃O₈)mesoporous hollow spheres have been facilely constructed via the bubble-template-assisted hydrothermal synthesis method combined with simple calcination.The compact assembly of small nanoparticles on the surface of the hollow spheres not only provides more active sites for the Fe₂Mo₃O₈,but also benefits the stability of the hollow structure,and thus improved the lithium storage properties of Fe2Mo3O8.The Fe₂Mo₃O₈ mesoporous hollow spheres exhibit high initial discharge and charge capacities of 1189 and 997 mA?h?g^?1 respectively,as well as good long-term cycling stability(866 mA?h?g^?1 over 70 cycles)when used as a lithium-ion battery anode.This feasible material synthesis strategy will inspire the variation of structural design in other ternary metal molybdates.