复合型絮凝剂PAC-PAM处理含乳化油废水的试验研究

研究了不同条件下的聚合氯化铝和聚丙烯酰胺复合絮凝剂(PAC-PAM)对含乳化油废水的絮凝效果,并与使用单一絮凝剂的效果进行了对比。通过单因素条件试验研究pH值、PAC:PAM配比、溶液温度和沉降时间等操作条件对PAC-PAM复合絮凝剂处理含油废水效果的影响,从而得到PAC-PAM复合絮凝剂处理含油废水的最优条件及絮凝机理。结果表明:PAC-PAM复合絮凝剂处理含乳化油废水的最佳操作条件为:PAC为30mg/L、PAM为6mg/L、溶液温度40℃、溶液pH值为7和沉降时间30min。以COD去除率代表絮凝效果的好坏,最优条件下的COD去除率达到84.57%。复合絮凝剂处理含乳化油废水的絮凝机理主要是:电中和破乳及高分子链的架桥综合作用。与使用单一絮凝剂PAC或PAM相比,PAC-PAM复合絮凝剂对含乳化油废水的絮凝效果更好。     

油田含聚丙烯酰胺废水的絮凝处理研究

油田聚合物驱采油废水中聚丙烯酰胺的去除是实现废水回用的关键。采用絮凝法去除模拟废水中的聚丙烯酰胺。以聚合氯化铝（PAC）作为絮凝剂,研究了投加量、pH值、搅拌时间、沉降时间等主要操作条件对絮凝效果的影响。结果表明：在絮凝剂投加量300 mg/L、pH值为中性、快搅时间1.5min、慢搅时间15min、沉降时间15min的条件下,PAM去除率达96.88%,废水中PAM浓度可达3.74mg/L。     

马铃薯淀粉废水的混凝预处理研究

本文介绍了用PAC（聚合氯化铝）、PFS（聚合硫酸铁）、PAM（聚丙烯酰胺）等絮凝剂处理高浓度有机淀粉废水的效果。通过对废水处理前后CODcr值的比较,结果得知PAC作为马铃薯淀粉废水的混凝剂最为合适,PAC的最佳投药量为500mg／L,对废水的CODcr去除率可达到44％左右。再经超滤膜分离,CODcr去除率可达到77％。     

絮凝技术用于高有机物海水预处理的研究

为了将盐田海水用作海水淡化水源,针对高有机物海水的预处理进行了烧杯絮凝实验,考察了絮凝条件、絮凝剂和助凝剂等参数对絮凝效果的影响。结果表明,最佳絮凝条件为:快速搅拌350 r/min、3 min,慢速搅拌80 r/min、8 min,沉淀时间30 min。聚合氯化铝铁去除浊度效果最好,在添加量为100 mg/L时,去除率达到85.37%;聚合硫酸铁去除COD效果最好,在同样添加量下,去除率为43.63%;而三氯化铁去除二者的效果均处于中间水平。骨胶和聚丙烯酰胺(PAM)均可以提高絮凝效果,其中PAM效果略好,在三氯化铁40 mg/L时,添加1 mg/L的PAM可使浊度和COD的去除率分别提高8.23%和8.10%。     

PAC-PAM复合絮凝剂处理燃煤电厂脱硫废水的研究

考察了现阶段燃煤电厂脱硫废水常用水处理药剂聚合氯化铝(PAC)与聚丙烯酰胺(PAM)联合用于预处理脱硫废水时,药剂的离子形态、絮凝剂选择、药剂投加量、反应转速、溶液pH对絮凝效果的影响及其影响机理。絮凝试验结果表明,非离子形态PAM在低投加量情况下的絮凝效果优于C-PAM和A-PAM;相较于PAFC、PAFS、PFS等絮凝剂,PAC的絮凝效果较好,且其与PAM质量比为10∶1、pH=8、转速为250 r/min条件下,除浊率达99.3%,此时上清液浊度为30.2 NTU,SS值为58 mg/L,可满足脱硫废水水质指标中对SS的出水要求。     

PAC-PAM复合混凝处理钻井液废水研究

以某地钻井液废水为研究对象,投加混凝剂聚合氯化铝(PAC)和助凝剂聚丙烯酰胺(PAM)对钻井液废水进行预处理。通过单因素实验和正交实验确定了最佳混凝条件为PAC投加量5 g/L,PAM投加量10 mg/L,pH值7左右,搅拌速率300 r/min。在上述最佳处理条件下,钻井液废水COD由14256 mg/L降至2578 mg/L,COD去除率达81.92%。浊度由147 NTU下降到23 NTU,浊度去除率为84.35%;预处理后废水中的各项污染指标均有较大降幅,可生化性大大提高,为后续的生化处理减轻负荷。     

一种新型景观水体絮凝剂的研究

文章研究了用无机絮凝剂硫酸铝、聚丙烯酰胺（PAM）和天然高分子絮凝剂壳聚糖（CTS）进行复配对景观水体的处理效果。实验结果表明：在硫酸铝、聚丙烯酰胺和壳聚糖投加量分别为99.5 mg/L、2.0 mg/L和2.0 mg/L时,絮凝效果最佳,CODCr和浊度的去除率可分别达67.4%与91.0%,与传统的Al2（SO4）3-PAM絮凝剂相比,CODCr和浊度的去除率分别提高了13.8%和4.7%,而且大大减轻了硫酸铝和聚丙烯酰胺对环境的二次污染,具有明显的环境效益。     

壳聚糖对PAC的助凝效果及机理研究

以壳聚糖(CTS)作为水厂常用絮凝剂聚合氯化铝(PAC)的助凝剂,以实际水体为实验水样,考察了CTS投加量、搅拌速度和水样pH值对絮凝出水COD_(Mn)和浊度的影响,并结合Zeta电位分析助凝机理。结果表明,pH为中性及弱碱性,PAC浓度30 mg/L,CTS投加0.2 mg/L时,助凝效果最佳;搅拌速度越快,形成絮体越松散细小,不利于聚集沉降。CTS的助凝机理以桥联作用为主,电性中和作用次之。     

壳聚糖对PAC的助凝效果及机理研究

以壳聚糖(CTS)作为水厂常用絮凝剂聚合氯化铝(PAC)的助凝剂,以实际水体为实验水样,考察了CTS投加量、搅拌速度和水样pH值对絮凝出水COD_(Mn)和浊度的影响,并结合Zeta电位分析助凝机理。结果表明,pH为中性及弱碱性,PAC浓度30 mg/L,CTS投加0.2 mg/L时,助凝效果最佳;搅拌速度越快,形成絮体越松散细小,不利于聚集沉降。CTS的助凝机理以桥联作用为主,电性中和作用次之。     

聚合氯化铝和聚丙烯酰胺复合絮凝剂处理造纸废水

研究了用聚合氯化铝和聚丙烯酰胺复合絮凝剂处理造纸废水,考察了酸度、混凝剂加人量、搅拌速度、搅拌时间、沉降时间对CODCr去除率的影响。实验结果表明：调节废液pH值在3-4之间,能够沉降废液中大部分悬浮物质,使废液CODCr明显降低;在搅拌速度为300r／min时,上层清液（废液调回至碱性）中加入PAC质量浓度300mg／L和PAM质量浓度15mg／L,可以将废液的CODCr值降到400mg／L左右。对絮凝后的废液用次氯酸钙进一步氧化处理,废液的CODCr值降到国家规定的造纸工业污水排放标准（150mg／L）。     

Compact Swelling in Bi1.4Pb0.6Sr2Ca2Cu3.6Oy During the Formation of High-Tc Superconducting Phase

Compact swelling in Pb-doped Bi-Sr-Ca-Cu-O superconductor has been studied by observing the effects of the size of calcined powders, volatilization of materials, and sintering of high- T _c (2223) powders. The bulk density increases at the early stage of sintering, for about 20 h, and then decreases. Densification occurs when the low- T _c (2212) phase and a liquid phase exist, whereas dedensification occurs with the formation of the 2223 phase regardless of the presence of the liquid. Gas evolution from specimens does not appear to be responsible for compact swelling. Compact swelling is explained by anisotropic growth of thin, platelike 2223 grains in random orientation. When 2223 grains grow in a preferred direction, compact swelling is suppressed.     

Synthetic routes to nanoscale BxCyNz architectures

B_xC_yN_z nanoscale materials, hybrids of h-BN and graphite, have been recently synthesised using various techniques. Here, we present the latest advances in the synthesis and characterisation of B-C-N nanotubes and nanofibres. In particular, we focus on layered BC₂N, BN, BC and CN_x systems, reviewing their production methods as well as their structural and electronic properties. These materials may find important applications in the fabrication of nanotransistors, robust nanocomposites, conducting polymers, storage components and field emission sources.     

Microwave Dielectric Properties of CaTiO3-CaAl1/2Nb1/2O3 Ceramics Doped with Li3NbO4

The microwave dielectric properties of CaTi_{1− x} (Al_1/2Nb_1/2) _x O₃ solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO₃. The substitution of Ti⁴⁺ by Al³⁺/Nb⁵⁺ improved the quality factor Q of the sintered specimens. A small addition of Li₃NbO₄ (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛ_r) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τ_f) of −2 ppm/K. Li₃NbO₄ as a sintering additive had no harmful influence on τ_f of ceramics.     

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.     

Structure Evolution from Pb(Mg1/3Nb2/3)O3 to La(Mg2/3Nb1/3)O3

The crystal structure of lanthanum-modified lead magnesium niobates having composition (Pb_{1− x} La _x ) (Mg_{(1+ x )/3}-Nb_{(2− x )/3})O₃ with X = 0 to 1 was investigated by X-ray powder diffraction. It was found that the fundamental reflections from perovskite structure remain in the whole range of composition. The superlattice reflections from the A(B'_1/2-B"_1/2)O₃ ordered structure are also well preserved for La content greater than 50 at.%; however, a series of extra peaks of mixing indices appears, with intensities gradually enhanced with the increase of La content. For the complete substitution of Pb by La, a splitting of some reflections can be observed in the diffraction pattern. The results indicate that the crystal structure evolves continuously with the La content, from disordered cubic perovskite of space group Pm 3 m for X = 0, to ordered cubic perovskite of space group Fm 3 m for X = 0.5, distorted cubic perovskite of space group Pa 3 for 0.5 < X < 0.9, and finally to a rhombohedral perovskite, possibly belonging to the space group R 3 , for X ≥ 0.9. In the evolution of structure, a linear reduction of the lattice constant of the perovskite cell from 4.048 to 3.964 Å was observed.     

Characteristic Spherulitic Microstructure in Partial-Melt-Processed YBa2Cu3Ox/HfO2

The microstructure of partial-melt-processed YBa₂Cu₃O _x /HfO₂ has been studied by transmission electron microscopy. A characteristic spherulitic microstructure is formed in the system. A model for the growth mechanism has been proposed. The critical heterogeneous nucleation of the YBa₂Cu₃O _x phase appears to occur from the melt in an epitaxially controlled manner on CuO particles. Subsequent growth of YBa₂Cu₃O _x platelets from the nucleus region is repeatedly interrupted by the nucleation of hafnium-rich phases in the liquid at the solid/liquid interface in a manner that again appears to be epitaxially controlled and that promotes the splay of the c orientation of the YBaCuO grain.