不同C/N下花生粕与果蔬皮联合厌氧发酵产酸效率研究

花生粕和果蔬皮等农业固体废弃物有机质含量高,适合厌氧发酵处理来回收沼气能源或生产挥发性脂肪酸(VFAs)。研究花生粕和果蔬皮C/N比对厌氧发酵产VFAs转化率(VFAs的当量总有机碳(TOC)和发酵底物TOC的比值)的影响,同时考察蛋白质、氨氮、溶解性多糖在VFAs积累过程中的变化。结果表明,C/N=37∶1时,VFAs转化率达到91%。皮尔逊相关系数分析表明,VFAs和多糖呈显著负相关,VFAs与蛋白质呈显著负相关,VFAs与氨氮呈显著正相关。     

玉米芯与鸡粪混合发酵提高甲烷发酵性能

为提高玉米芯和鸡粪厌氧发酵甲烷产率,研究了玉米芯和鸡粪混合发酵性能。实验结果表明,玉米芯与鸡粪最佳混合比为5∶1,沼气和甲烷产率最高,分别是200mg/g和121.2mL/g（玉米芯/鸡粪,VS,下同),与单一鸡粪厌氧发酵相比,沼气产量提高了700%,玉米芯与鸡粪混合发酵有助于更多的生物质向甲烷转化。玉米芯与鸡粪在最佳比例下混合发酵时挥发性脂肪酸（VFAs）最高达2.56g/L,乙酸在VFAs中起主导作用。适当的鸡粪添加有助于体系氨氮含量增大和甲烷菌活性提高,过多鸡粪添加不利于甲烷总产量的提高。氨氮与VFAs的中和作用促进了体系的pH稳定。底物进料量对沼气产率有明显的影响,混合底物进料量为50g/L时总产气量最高,为7800mL,对应的甲烷体积分数为68.7%,而进料量为20g/L时沼气产率和甲烷产率最高,分别为325mg/g和184.3mL/g。玉米芯与鸡粪混合发酵能够改善碳氮底物（C/N）的发酵比、提高微量金属元素含量,是甲烷产率提高的主要原因。     

剩余污泥中温和高温厌氧水解酸化产VFAs性能研究

通过对比中温（35℃）和高温（50℃）厌氧产酸过程中挥发性有机酸（VFAs）含量与成分的变化,研究温度对剩余污泥的颗粒粒径、颗粒有机物降解情况、可溶性化学需氧量（SCOD）及挥发性有机酸（VFAs）的影响。结果表明,高温厌氧发酵可以显著促进污泥絮体解离,污泥分解率可达41.10%,微生物反应机率增加,反应效率提高。中温发酵和高温发酵过程中颗粒性有机物的水解过程均遵循一级反应动力学,且高温水解速率常数显著高于中温水解速率常数。中温水解液中未知溶解性有机物积累量高,转化慢,可能是中温发酵产酸效果低于高温条件的原因之一。高温发酵获得的VFAs约为中温VFAs产量的2倍,其中有机酸异戊酸和异丁酸的比例较高,二者约占VFAs的50%;中温发酵过程VFAs的组分单一,主要为乙酸。水解液中氨氮的增加量与颗粒型蛋白质的分解量存在强相关关系,高温发酵下的氨氮转化因子显著高于中温发酵的氨氮转化因子。     

餐厨垃圾干式厌氧发酵技术研究进展及展望

总结了餐厨垃圾干式厌氧发酵的关键影响因素(温度、pH、含固率、有机负荷、含盐量和含油量、C/N、氨氮、挥发性脂肪酸),概述了强化餐厨垃圾干式厌氧发酵的主要策略(外源添加剂、预处理、接种物、共发酵)。对餐厨垃圾干式厌氧发酵的发展方向提出了展望及建议。     

酒精废水优化产酸及其强化低C/N污水氮磷去除

对木薯酒精废水厌氧产酸的预处理条件进行优化,并探究以其厌氧发酵液作外碳源,对处理低C/N生活污水的影响。结果表明,在热处理且pH为9条件下,木薯酒精达到最佳产酸效能,VFAs产量高达30～35 g COD/L。以木薯酒精厌氧发酵液为外碳源,处理低C/N生活污水的TN、TP去除效果更佳,分别为73.2%和69.6%,显著优于乙酸钠系统。在木薯发酵液系统中,Bacteroides、Janthino-bacterium sp.、Pseudomonas和Microvirgula aerodenitrificans等优势菌群表现出良好的硝化反硝化及反硝化除磷效果,而乙酸钠系统中检测出一种重要的GAOs(Defluviicoccus vanus),导致除磷效果受到一定影响。以木薯酒精厌氧发酵液作外碳源的投加,成本远低于乙酸钠等常用商业碳源,具有较好的应用价值。     

不同C/N对一体化MBR中微生物产物的影响

采用一体式膜生物反应器处理模拟生活污水,在葡萄糖作为碳源的条件下,通过调整C/N,分析C/N的变化对微生物代谢产物的影响趋势。结果表明,当m(C)/m(N)在2.5~3.6变化时,胞外聚合物(EPS)和溶解性微生物代谢产物(SMP)的积累程度均随着C/N的增加而增大。此外,通过对EPS和SMP含量分析发现,EPS和SMP中多糖的含量要高于蛋白质的含量,污泥中多糖含量的增加相对于蛋白质更容易引起膜污染。     

热、碱预处理对厨余垃圾厌氧发酵产挥发性脂肪酸的影响

有机质水解效率低是厌氧发酵过程的主要限速步骤,本研究通过探究不同温度下热预处理和不同p H值条件下的碱预处理对厨余垃圾厌氧发酵产生挥发性脂肪酸(VFAs)的影响。结果表明,调整适合的热预处理温度和碱预处理p H值对厨余垃圾厌氧发酵合成终产物VFAs有明显的促进作用。优化厨余垃圾热预处理温度发现100℃热预处理为最优条件,在反应6天时达到最大VFAs产量11.99±0.77 g/L,相比于130℃和160℃预处理VFAs最大产量提升40.62%～75.47%。优化碱预处理p H值发现,在p H=8条件下进行预处理对于VFAs产量的提升最为明显,在反应8天时达到最大VFAs产量15.60±1.04 g/L相比于p H=6和p H=10条件下提升84.24%～103.82%。     

苯酚对氨氧化菌硝化和污泥性能冲击影响

以苯酚为毒性抑制剂,短程硝化污泥为对象,分析研究了不同苯酚浓度对氨氧化菌硝化过程的抑制特性和抑制动力学,以及对污泥胞外聚合物组分及呼吸速率的短期冲击影响。结果表明,55 mg·L-1苯酚的存在使硝化速率降低37%;低浓度苯酚条件下（< 80 mg·L-1）符合Monod单分子一级动力学方程,且为可逆性抑制,恢复后呼吸速率可达20～25 mg O2·L-1·h-1;且因接种污泥含大量异养菌使得抑制常数（52.871 mg·L-1）远大于纯硝化菌群系统。另外,苯酚的存在促使菌群启动自我保护机制产生更多的胞外聚合物(EPS)抵抗环境变化。苯酚浓度升至135 mg·L-1时,蛋白质和多糖分别增加87.4%和311.7%;而且EPS组分发生相应变化,蛋白质/多糖（P/C）与初始COD/氨氮（C/N）比呈负相关性,P/C从22.1降至3.80。     

花生粕制备活性肽复合工艺研究

利用木瓜蛋白酶和中性蛋白酶水解花生粕提取花生蛋白。研究了温度、粕水比、提取时间对多糖提取率的影响,确定最佳提糖条件为温度80℃、粕水比1：25、提取时间1h。通过正交实验研究了加酶量、液固比、水解时间对蛋白质提取率的影响。确定最佳工艺参数为加酶量3％、粕水比1：25、水解时间2h,在此条件下,蛋白质转化率为80％。最终先去糖再酶解复合工艺蛋白收率为60％,相对分子量1000Da以下的活性肽占87％。     

表观厌氧环境下短程硝化同步反硝化的实现与特征分析

近年来,水体富营养化引起的水环境安全事件频发。总氮(TN)是引起水体富营养化的其中一个关键因素,废水脱氮处理能够有效减少TN的排放。研究采用序批式反应器(SBR),通过控制曝气量,建立溶解氧(DO)低于0.01 mg/L的表观厌氧环境,成功启动并维持了短程硝化及同步反硝化。低氨氮进水(80 mg/L)下,氨氮氧化率和亚硝酸盐氮(NO₂^--N)转化率分别为99%和94%;高氨氮进水(160 mg/L)下,氨氮氧化率和NO₂^--N转化率分别为98%和88%。比较分析发现,进水碳氮比(C/N)为2∶1时,短程硝化同步反硝化具有最高的成本效益,TN去除率和出水氨氮平均质量浓度分别约为50%和4.8 mg/L,去除1 g TN实际消耗4.94 g碱度(以CaCO₃计)。     

Polymorphism of LiGa5O8 and of LiGa5O8-MgGa2O4Solid Solutions

High-temperature X-ray diffraction and differential thermal analyses showed that LiGa₅O₈ exists in two polymorphs related by the first-order transition at 1138°±3°C of the low-temperature simple-cubic form, space group (probably) O⁷, to the high-temperature spinel (fcc) form, space group O _h ⁷. The transition is rapid, and the high-temperature form in pure LiGa₅O₈ could not be quenched to room temperature under the conditions used. However, the high-temperature polymorph can be quenched under equilibrium conditions when 40 mol% or more MgGa₂O₄ is present. The subsolidus equilibrium relations in the system MgGa₂O₄-LiGa₅O₈ are discussed.     

Magnetoresistance of CuxCo1-xFe2O4 Ferrites

Magnetoresistance measurements (Δ/R) were carried out on Cu _x Co_{1- x} Fe₂O₄ samples with x =1, 0.75, 0.50, 0.25 and cobalt ferrite in the range of magnetic intensity (H) from 1.0 to 4.5 kG. Linear plots were obtained between log (Δ/R) and log H for all compositions except that of cobalt ferrite. The values of n at x =0.5 do not agree with the results of some authors. The discrepancy may be attributed to the value of magnetic field intensity at which such measurements were carried out. The similarity of features of n and μ_D with composition leads us to believe that the magnetoresistance may arise from the scattering of conduction electrons by localized electrons involving the s-d exchange interaction.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Expansive properties of the mixture C4ASH12 − 2CS III. Effects of temperature and restraint

The effects of temperature and restraint upon the hydration and the expansion of $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}\text{? 2}\text{C}\text{S}$ mixture compacts in different contact solutions have been investigated. Temperatures above 20°C do apparently hinder the formation of an impervious felt-like layer of ettringite around the $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}$ particles, thus greatly reducing the retarding effect of the lime. An uniaxial restraint of 1 Kg/cm² is enough to reduce sensibly the expansions which remain however high (about 100%). The results can be satisfactorily interpreted by the reaction and expansion mechanism hypothesized in our previous papers.     

Raman Study of Glasses of Ba2TiSi2O8 and Ba2TiGe2O8

Raman spectra are reported for fresnoite (Ba₂Ti(Si,Ge)₂O₈ glasses, and comparison is made between the Raman spectra of the corresponding crystalline powders and glasses of Ba₂TiSi₂O₈ and Ba₂TiGe₂O₈. The Ba₂TiGe₂O₈ glass spectra show correspondence with the Ba₂TiGe₂O₈ crystalline Raman spectra; the v _s(Ge–O–Ge) mode occurs at 518 cm⁻¹ in the glass and at 521 cm⁻¹ in the crystalline material. Five-fold coordinated titanium is the majority species present in the Ba₂TiGe₂O₈ glass as revealed by a strong band at 824 cm⁻¹ in the I glass spectrum. The Ba₂TiSi₂O₈ glass spectra are similar to the Ba₂TiSi₂O₈ crystalline spectrum; the strongest band is found at 836 cm⁻¹ in the I glass spectrum. Through comparison with the previous Raman data of other titania silicate glasses, we conclude that the Ba₂TiSi₂O₈ glass has a structure similar to the crystalline phase.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Effects of metal-support interactions on the hydrogenation of CO over PdSiO2 and PdLa2O3

A study of CO hydrogenation over $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$ has been carried out for the purpose of identifying the effects of Pd dispersion, Pd morphology, and support composition on the catalytic activity of supported Pd. The specific activity of each catalyst for methanol and methane synthesis was determined from microreactor studies carried out at a fixed set of reaction conditions. Palladium dispersion was measured by H₂O₂ titration, and the morphology of the Pd crystallites, as expressed by the distribution of Pd(100) and Pd(111) planes, was determined from in situ infrared spectra of adsorbed CO. The crystallite morphology of the $\text{Pd}\text{SiO}{}_2$ catalysts is the same, independent of Pd weight loading: 90% of the surface is comprised of Pd(100) planes and 10% of the surface is comprised of Pd(111) planes. By contrast, the crystallite morphology of the $\text{Pd}\text{La}{}_2\text{O}{}_3$ catalysts changes with Pd loading. Primarily Pd(100) planes are exposed at low-weight loadings while Pd(111) planes are exposed at high-weight loadings. The Pd dispersion has little effect on the methanol turnover frequency over both $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$, for dispersions between 10 and 20%. On the other hand, the methane turnover frequency is independent of Pd dispersion over $\text{Pd}\text{SiO}{}_2$, but increases with decreasing dispersion over $\text{Pd}\text{La}{}_2\text{O}{}_3$. It is further observed that the Pd morphology influences the specific activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ for methanol synthesis: Pd(100) is nearly threefold more active than Pd(111). For a fixed morphology, the specific methanol synthesis activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ is a factor of 7.5 greater than that of $\text{Pd}\text{SiO}{}_2$.     

In situ laser raman spectroscopy of the sulfiding of Moγ-Al2O3 catalysts

Raman spectra of sulfided $\text{Mo}\text{γ-}\text{Al}{}_2\text{O}{}_3$ catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% $\text{H}{}_2\text{S}\text{H}{}_2$ at 400 °C, MoS₂ structures were observed. A stepwise sulfiding using 10% $\text{H}{}_2\text{S}\text{H}{}_2$, with spectra recorded at 150, 250, and 350 °C, resulted in observation of molybdenum oxysulfide, reduced molybdate, and surface “MoS₂” phases. Reexposure of these samples to air led to radical modification of the oxysulfide structures as well as transformation of some sulfide phases. A model incorporating terminal and bridging MoS bonding and anion vacancies is proposed. This model is based on the conversion of isolated and aggregated molybdate and MoO₃ species to oxysulfide and reduced molybdenum phases. Conversion of reduced molybdenum phases to sulfides is observed to be slow.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.