Dissolution kinetics of malachite in ammonia/ammonium sulphate solution

The dissolution kinetics of malachite was investigated in ammonia/ammonium sulphate solution. The effects of ammonia and ammonium sulphate concentration, pH, leaching time, reaction temperature, and particle size were determined. The results show that the optimum leaching conditions for malachite ore with a copper extraction more than 96.8% are ammonia/ammonium concentration 3.0 mol/L NH₄OH + 1.5 mol/L (NH₄)₂SO₄, liquid-to-solid ratio 25:1 mL/g, leaching time 120 min, stirring speed 500 r/min, reaction temperature 25 °C and particle size finer than 0.045 mm. The dissolution process of malachite with an activation energy of 26.75 kJ/mol is controlled by the interface transfer and diffusion across the product layer. A semi-empirical rate equation is obtained to describe the leaching process and the reaction orders with respect to concentration of ammonia and ammonium sulphate are 2.983 0 and 0.941 1, respectively.     

Leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system

The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69μm, holding at 80℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2：1, and the ratio （g/mL） of solid to liquid being 1：10.     

Improved GaN grown on Si(111) substrate using ammonia flow modulation on SiNx mask layer by MOCVD

In this paper, 1 μm n-GaN was grown by using varied and fixed ammonia flow (NH₃) on SiN _x mask layer on Si(111) substrate using metal organic chemical vapor deposition (MOCVD). In-situ optical reflectivity traces of GaN growth show that the three- to two-dimensional process has been prolonged by using varied ammonia flow on SiN _x mask layer method compared with that grown by fixing ammonia flow. Structural and optical properties were characterized by high-resolution X-ray diffraction and photoluminescence, and compared with the sample grown by fixing ammonia flow, GaN grown using the varied ammonia flow on SiNx mask layer showed better structure and optical quality. It was assumed that the low NH₃ flow in the initial growth stage considerably increased the GaN island density on the nano-porous SiN _x layer by enhancing vertical growth. Lateral growth was significantly favored by high NH₃ flow in the subsequent step. As a result, the improved crystal and optical quality was achieved utilizing NH₃ flow modulation for GaN buffer growth on Si(111) substrate.     

Melt synthesis and characterization of poly(L-lactic acid) chain linked by multifunctional epoxy compound

High molecular weight(Mw) poly(L-lactic acid)s(PLLAs) were synthesized using multifunctional epoxy compound(Joncryl-ADR4370) as chain extender. The products were characterized by gel permeation chromatography(GPC) and spectroscopy(¹HNMR and FTIR). The results indicated that the Mw of PLLA increased with the increasing of the ratio of epoxy compound and the extending of reaction time. The highest M _w of PLLA reached 360 000 g/mol when the ratio of epoxy compound was 1.5 wt%. However, the reactants turned to cross-linking when the ratio of epoxy compound was over 1.5 wt%. Differential scanning calorimetry(DSC) measurements demonstrated that the glass transition(T _g) and melting temperatures(T _m ) of products increased slightly as the increase of the molecular weight. Analysis of the hydrolytic degradation in vitro showed that the branched PLLA possessed the quicker degradability than that of the linear PLLA.     

Experimental Study on Enhancement of Bubble Absorption of Gaseous CO2 with Nanofluids in Ammonia

纳米颗粒强化氨水鼓泡吸收CO₂实验研究

方立军,刘洪锟,边岩,刘玉东,杨亚利

（华北电力大学（保定） 能源动力与机械工程学院）

研究目的：

探究纳米颗粒对鼓泡塔氨法吸收二氧化碳的强化作用

研究方法：

（1）试剂：氨水,质量分数为25%-28%,天津化工有限公司生产;二氧化碳气体,纯度为99.99%,氮气,99.99%,保定北方特种气体有限公司生产;纳米颗粒（SiO₂、TiO₂、CuO）,由南京埃普瑞纳米材料有限公司提供。

（2）本文纳米流体的制备方法采用的是“两步法”,首先用天平准确称取所需的纳米TiO₂、CuO、SiO₂,量取所需要的蒸馏水,然后通过机械分散20分钟,加入一定量的氨水,继续机械分散10分钟制备为不同质量分数的纳米流体,纳米流体的分散稳定性良好。

（3）实验系统：纳米颗粒强化氨水鼓泡吸收CO₂实验系统如图所示,主要包括鼓泡吸收塔、烟气配送系统、尾气测量处理系统。

实验步骤：

（1）实验前先计算出配制纳米流体所需的纳米颗粒、氨水、蒸馏水的量,用电子秤称出纳米颗粒的质量,将其加入到蒸馏水中,机械搅拌20min,加入一定量的氨水,继续机械分散10分钟制备为不同质量分数的纳米流体;

（2）打开分析仪预热30min,开通N2对整个系统进行吹扫,待CO2烟气分析仪示数降为0时。按照比例将氮气与二氧化碳充入混合瓶,混合均匀后通入分析仪,待示数达到预设值且稳定;

（3）将配制好的纳米流体加入到反应塔内,开始计数,每5s计数一次,待示数不再降低,停止计数。

为减少偶然误差带来的影响,每组实验均进行5次,然后取其平均值。为减少氨水浓度对本实验的影响,每次实验都要测量配制好的溶液的pH值,保证初始溶液具有相同pH值。

结果：

（1）纳米颗粒种类和固含量对增强因子的影响

对氨水质量分数为1%,CuO、TiO₂、SiO₂颗粒添加量分别为1g/L、2g/L、3g/L、4g/L、5g/L的纳米流体进行鼓泡吸收实验,增强因子如图所示：

增强因子与纳米颗粒种类的关系

从图中可以看到只有添加TiO₂这一种纳米颗粒时,其增强因子一直大于1;添加SiO₂ 纳米颗粒,只有在1g/L、2g/L时,增强因子略大于1,其他添加量则小于1;添加CuO 纳米颗粒,其增强因子始终在1左右徘徊,没有出现出明显的增强或抑制作用。

（2） 氨水浓度对增强因子的影响

从图中可以看出,不同氨水浓度下,增强因子的变化趋势随固含量的增加先升高后降低。但是,它们的最佳固含量不同,随着氨水浓度的升高,最佳固含量降低。

（3） 纳米颗粒种类对脱除率的影响

从图中可以看出,TiO2纳米流体的吸收率要大于空白溶液,CuO纳米流体的吸收率和空白溶液相同,而SiO2纳米流体的吸收率小于空白溶液。

（4）纳米颗粒添加量对脱除率的影响

从图中可以看出,脱除率随纳米颗粒添加量的增加先增高后降低,且脱除率一直大于空白溶液实验,在纳米颗粒添加量为3.0g/L时脱除率达到最大值。

结论：

（1）纳米颗粒的添加对于部分有化学反应气液传质过程具有强化作用,其强化作用与纳米颗粒和溶剂的性质有关;

（2）对气体溶质具有选择吸附性、增溶剂性的纳米颗粒可对有化学反应的气液传质过程有强化作用。其强化作用随着纳米颗粒添加量的增加先增大后减小,即纳米TiO2的含量对强化氨水捕集CO₂存在一个最佳固含量;

（3）对气体溶质没有吸附性但具有亲溶剂性的纳米颗粒可对有化学反应的气液传质过程有抑制作用。其抑制作用随着纳米颗粒添加量的增加而逐渐增强;

（4）纳米颗粒强化有化学反应的气液传质过程的机理可总结为,纳米颗粒在布朗运动的作用下会使吸收工质内部形成微对流,从而使分子扩散系数增大。纳米颗粒对气体溶质的吸附性,使传质边界层内气相溶质浓度降低,传质边界层内的浓度梯度增大,传质推动力增加,气体吸收得到强化。

关键词：纳米颗粒;鼓泡塔吸收;氨水;CO₂捕集;强化吸收

     

300 MW无烟煤锅炉选择性催化还原系统积灰原因分析

无烟煤锅炉由于挥发分含量低,着火困难,所以设计过程中都采用了较高的燃烧温度,从而导致选择性催化还原系统入口NOx排放浓度较高,脱硝系统压力较大。设计过程中灰颗粒尺寸选型不合理、灰黏性偏高、系统安装结构不合理以及喷氨量偏大等问题是引起脱硝系统积灰堵塞的主要原因。通过对脱硝系统优化改造和提高喷氨调整的自动化程度等,可以有效缓解选择性催化还原系统的堵塞情况;通过计算氨氮摩尔比,可以对氨逃逸浓度的测量结果进行校核。     

Thermodynamic study on reaction path of Hg（ II ） with S（ II ） in solution

The mercury sulfidation experiments were conducted in the pH range from 1 to 13. The results show that Hg(Ⅱ) reacted with equimolar S(Ⅱ) has the lowest remained Hg(Ⅱ) concentration (9.7 μg/L) at pH 1.0 and the highest remained concentration (940.8 ug/L) at pH 13.0. Meanwhile, the changes of pH values were monitored exactly, which reveal that solution pH values change when mixing the same pH value solutions of HgCl_2 and Na_2S. In order to explain the phenomena and determine the reaction paths of Hg(Ⅱ) reacting with S(Ⅱ) in the solution, the concerned thermodynamics was studied. Species of S(Ⅱ)-H_2O system and Hg(Ⅱ)-H_2O system at different pH values were calculated, and then the species distribution diagrams of S(Ⅱ)-H_2O system, Hg(Ⅱ)-H_2O system and Hg(Ⅱ)-Cl~-0H~~-H_2O system were drawn. Combining the experimental data and thermodynamic calculation, the mechanism of Hg(Ⅱ) reacting with S(Ⅱ) was deduced. The results indicate that different species of S(Ⅱ) and Hg(Ⅱ) have the diverse reaction paths to form HgS precipitate at different pH values and the standard Gibbs free energies change(△_rG_m~Θ) of those equations are also calculated, which can provide a guidance for mercury-containing wastewater treatment with Na_2S.     

Synthesis of calixarenes and their extraction performance for ester catechins

A series of extractants (tert-butylcalix[6]arene, tert-butylcalix[8]arene and octeacetate of tert-butylcalix[8]arene) were synthesized, and their structures were identified by IR and 1H-NMR. The distribution behavior of ester catechins monomer in the aqueous and chloroform two-phase system containing one of calixarene was studied. The influences of different extractants, concentration of tert-butylcalix[8]arene and extraction temperature on the partition coefficients and the separation factors were investigated. The experiment results show that tert-butylcalix[8]arene is the best extractant that forms a more stable supramolecular compound with gallocatechin gallate (GCG) than with epigallocathechin gallate (EGCG) or epicatechin gallate (ECG). When the concentration of p-tert-butylcalix[8]arene is 3.79 mmol/L, the extraction temperature is 4 ℃, the partition coefficients of KGCG, KECG, KEGCG are 0.987, 0.629, 0.449,the separation factors of α1 and α2 are 1.450 and 1.596, respectively. The important factors influencing the extraction properties of calixarene are discovered to be its cavity size and hydrogen bonding.     

Use of Tetrazolium Salt INT for Estimation of Biological Activity of Activated Sludge Cultivated in SBR Process

The tetrazolium salt 2-（4-Iodophenyl） -3-（ 4-nitrophenyl ） -5-phenyltetrazolium chloride （INT） was used as a tool fi）r estimating the activity of the electron transport system （ETS） in activated sludge in a 40 L sequencing batch reactor （SBR） and domestie sewage as the organic substrate. The activity of INT-ETS during one SBR cycle, and the effeet of the ammonia concentration and the concentration of organic matter influent on the INT-ETS activity were investigated. The results show that： the use of INT is reliable in estimating of biological activity of activated sludge of SBR system; Biological activity of organic matter biodegradation, nitrification and denitrification process in SBR system reduce orderly. Obviously, INT-ETS activity reduces from 232.59 rny/（g · h） to 190. 65 rag/（ g ·h） at first and then decreases to 113.88 my/（ g · h） when influent concentration of COD and NH4＋-N is 300 my/L and 40 mg/L respectively. In addition, various influent Nitrogen （NH4＋-N are 14.5 mg/L and 42.0 my/L） and organic shock loading （COD are 293 mg/L and 685 my/L） experimenntions cure prove that operational conditions have no obvious effect on INT-ETS variation rule. However, the time of the appearance of feature points marking different reaction phase is influenced.     

Effects of different conditions on Pb2+ adsorption from soil by irrigation of sewage in South China

Pb²⁺ adsorption onto a soil by irrigation of sewage in the Pearl River Delta of South China was examined as a function of the reaction time, solution pH, initial lead concentration, organic matter (humic acid) and competitive ions (Cu²⁺). The adsorption of Pb²⁺ onto the soil was investigated on batch equilibrium adsorption experiments. Results show that the Pb²⁺ adsorption on the soil is relatively rapid in the first 30 min and reaches equilibrium at 2 h, and the kinetics of the adsorption process on the soil is well characterized by the pseudo-second order reaction rate. Langmuir, Freundlich and Temkin isothermal models are fit for the adsorption of Pb²⁺ onto the soil, and the maximum amount of Pb²⁺ adsorption (Q _m) is 7.47 mg/g. The amount of Pb²⁺ adsorption increases with increasing the pH at the range of 1.2–4.5 and reaches a plateau at the range of 4.5–12. The presence of humic acid in soil decreases the adsorption of Pb²⁺ onto the soil at solution pH of 8 since the negatively charged humic acid with Pb²⁺ is difficult to be adsorbed on the negatively charged soil surface. The adsorption of Pb²⁺ onto the soil also decreases in the presence of Cu²⁺ due to the competition adsorption between Pb²⁺ and Cu²⁺.     

Advanced sludge reduction and phosphorous removal process

An advanced sludge reduction process, i.e. sludge reduction and phosphorous removal process, was developed. The results show that excellent sludge reduction and biological phosphorous removal can be achieved perfectly in this system. When chemical oxygen demand ρ（COD） is 332 - 420 mg/L, concentration of ammonia p（NH3-N） is 30 - 40 mg/L and concentration of total phosphorous p（TP） is 6.0 -9.0 mg/L in influent, the system still ensures ρ（COD）〈23 mg/L, ρ（NH3-N）〈3.2 mg/L and ρ（TP）〈0. 72 mg/L in effluent. Besides, when the concentration of dissolved oxygen ρ（DO） is around 1.0 mg/L, sludge production is less than 0. 140 g with the consumption of 1 g COD, and the phosphorous removal exceeds 91 %. Also, 48.4% of total nitrogen is removed by simultaneous nitrification and denitrification.     

Synthesis and photocatalytic property of the ZrO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> pillared laponite

The ZrO2/TiO2 pillared laponite (Ti-Zr-lap) photocatalysts were prepared with intercalation reaction by supercritical fluid drying (SCFD),and characterized by XRD,TEM,SEM and BET surface area analysis,and the photocatalytic properties of Ti-Zr-lap were investigated by degradation of azo dye acid red B (ARB).The results showed that the ZrO2/TiO2 pillared structures in laponite could be formed,with the mass fraction of (Zr4++Ti4+)/laponite (Xm) increasing,the basal spacing and the BET surface area of Ti-Zr-lap significantly increased.The Ti-Zr-lap used as photocatalyst had the advantages of stable and porous layered structure,large surface area with the anatase type TiO2.Compared with the Ti-Zr-lap dried by air drying,the Ti-Zr-lap dried by SCFD showed better photocatalytic property which was very close to that of P25 TiO2.Using the Ti-Zr-lap as photocatalyst with the optimum Xm of 0.16 and the calcination temperature of 500 ℃,under the conditions of the initial concentration of ARB 20 mg/L,photocatalyst concentration of 1.5 g/L and irradiation time 60 min,the decoloring rate of ARB could achieve 98.3%,indicating that the Ti-Zr-lap had excellent photocatalytic property.     

丙烯酰胺-DMC的水溶液共聚反应

采用复合引发体系,用水溶液聚合法制备出丙烯酰胺(AM)和甲基丙烯酰氧乙基三甲基氯化铵(DMC)的共聚物。考察了反应温度、单体质量分数、引发剂质量分数和pH等因素对聚合物特性黏数和水溶性的影响,得到的较佳工艺条件为:反应温度25℃,单体质量分数45%,引发剂质量分数0.010%,pH 3.0。在上述条件下,产物的特性黏数为9.346 5 dL.g-1。用红外光谱技术对聚合物的结构进行了表征。     

人工红树林碳通量变化特征及其影响因素分析

红树林是重要的滨海蓝碳生态系统.人工红树林在恢复过程中碳交换过程受到气候、植被等环境的影响,与成熟红树林呈现较大差异.本研究采用闭路涡动相关系统对珠江河口人工红树林湿地生态系统进行二氧化碳(CO₂)通量和甲烷(CH₄)通量的观测,并基于通径分析方法探讨了环境要素对总初级生产力(GPP)、生态系统呼吸(R_e)、CO₂和CH₄通量的影响.结果表明：CO₂通量呈现明显的日变化特征,受到GPP和R_e的协同影响,其季节变化特征不明显;CH₄通量则呈现明显的季节变化特征.2019—2020年CO₂年通量为74.9～138.4 g·m^-2·a^-1(以C计,下同),CH₄年通量为25.1～25.9 g·m^-2·a^-1.CO₂变化特征受到GPP的直接影响,总辐射(R_a<...     

Thermodynamic assessment of Au-Zr system

1　INTRODUCTIONChemicalvapordeposition (CVD)diamondholdsgreatpromiseinsolvingthermalmanagementprobleminhigh performancemulti chipmodules (MCMs) .However ,thismaterialdoespresentsometechnologi calchallenges ,onebeingthedevelopmentofreliablemetallizationsystems[1] .Thedesirablecharacteristicsofametallizationsystemare goodadhesiontothesubstrate ,lowstress ,goodelectricalconductivityandminimalreactionsatsubsequentprocessingtempera tures (upto 4 0 0℃ ) [2 ] .Goldisusuallychosenasthemetalfor…     

甲基磺酸- 双氧水体系对印刷电路板拆解技术

废印刷电路板上元器件的拆解技术是电路板资源化再利用的重要环节。通过研究甲基磺酸-双氧水体系下元器件的脱落率,得出优化的实验条件为:甲基磺酸浓度范围为3.0～3.5 mol/L,双氧水浓度范围为0.4～0.6 mol/L,反应时间45 min。在该实验条件下,实验样品中焊接元器件脱落率达到100%,实现了电路板基板与元器件的快速高效分离,为废旧电路板上元器件的拆解技术提供一定的技术支撑。     

Study on the spectral response of <Emphasis Type="Italic">Brassica Campestris L.</Emphasis> leaf to the copper pollution

Brassica Campestis L. was cultivated in the soil at the laboratory. The red edge, the visual spectrum and the near-infrared spectrum of Brassica Campestis L. leaf were used to explore the spectral response of Brassica Campestis L. leaf to the copper stress. As the Cu content in the soil gets increased, the copper level in Brassica Campestris L. leaf would be increased, and the chlorophyll level in Brassica Campestris L. leaf would be decreased. As a result, the visual spectral reflectance (A ₁) of Brassica Campestris L. leaf is increased, and the blue-shift (moving towards the shorter waveband) degree (S) of the red edge (the ascending region of the reflectivity at 680–740 nm) gets increased. However, the near-infrared spectral reflectance (A ₂) decreases. With the correlation coefficient R ² more than 0.95, these parameters of A ₁, A ₂ and S can be perfectly used to simulate and predict the copper level in Brassica Campestris L. leaf. Supported by the Major State Basic Research Development Program (Grant Nos. 2003CB415007 and 2003CB415104)     

Investigation on extremal and critical characteristics of ignition time for H<Subscript>2</Subscript>/O<Subscript>2</Subscript> combustion system and their applications

The L, H and C curves in P-T phase are proposed to describe the minimal, maximal and critical characteristics of ignition time of H₂/O₂ combustion system, respectively. The features of H₂/O₂(Air) combustion system, including explosion or not as well as the time delay to achieve its explosion status, can be well shown by explosion limits and these proposed curves. These curves can be described by 1.2k ₁=k _s [M_s], (k ₁₁/k ₁₀+1)k ₁=k _s [M_s], and 2k ₁=k _s [M_s], respectively, which provide a physical explanation for these curves and give another way to establish them. Based on the contour of ignition time, the Z-type explosion limits can be explained by thermal explosion theory. Furthermore, the ignition distance of supersonic combustion is predicted according to the ignition time obtained in a Semenov system, which is very reasonable.     

Synthesis of γ-Al2O3 nanoparticles by chemical precipitation method

Highly pure active γ-Al₂O₃ nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al₂O₃ nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor Al(OH)₃ sols are produced by using 0.1 mol/L Al(NO₃)₃ · 9H₂O and 0.16 mol/L (NH₄)₂CO₃ · H₂O reaction solutions, according to the volume ratio 1.33, adding 0.024% (volume fraction) surfactant PEG600, and reacting at 40 °C, 1 000 r/min stirring rate for 15 min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80°C for 8 h, final calcined at 800 °C for 1 h in the air, and high purity active γ-Al₂O₃ nanoparticles can be prepared with cubic in crystal system, O _H ⁷ -FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131. 35 m²/g in BET specific surface area, 7 – 11 nm in pore diameter, and not lower than 99.93% in purity. Foundation item: Project(03JJY3015) supported by the Natural Science Foundation of Hunan Province     

一种基于 MXene 的Fe2O3/Nb2O5/Nb4C3Tx 高灵敏丙酮传感器

MXene 具有较大比表面积和优异的导电性, 当与金属氧化物半导体结合时可以抑制片层团聚, 还可以大大提高载流子转移速率, 提高气敏性能。通过简单的水热和煅烧两步法成功合成了Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 三元复合材料。通过表征, Fe₂O₃ 微米球分布在 MXene 纳米片层之间。气敏测试结果表明, 与原始Fe₂O₃相 比, Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器对丙酮的响应能力有明显的提高。传感器灵敏度高, 选择性较好, 对环境中 浓度为 5 ×10^?6 的丙酮响应高 (R_a /R_g = 7.81, 30% RH), 响应和恢复速度快, 具有出色的重复性和长期稳定性。Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器具有良好的气敏性能, 主要因为三元复合材料提供了较大比表面积和丰富的氧空位, 增强了活性位点, 使得气体易于在传感器表面扩散, 为开发丙酮敏感复合材料提供了参考。