Acceleration of floc-water separation and floc reduction with magnetic nanoparticles during demulsification of complex waste cutting emulsions

Waste cutting emulsions are difficult to treat efficiently owing to their complex composition and stable emulsified structure. As an important treatment method for emulsions, chemical demulsification is faced with challenges such as low flocs–water separation rates and high sludge production. Hence, in this study, Fe₃O₄ magnetic nanoparticles (MNPs) were used to enhance chemical demulsification performance for treating waste cutting emulsions under a magnetic field. The addition of MNPs significantly decreased the time required to attain sludge–water separation and sludge compression equilibrium, from 210 to 20 min. In addition, the volume percentage of sludge produced at the equilibrium state was reduced from 45% to 10%. This excellent flocculation–separation performance was stable over a pH range of 3–11. The magnetization of the flocculants and oil droplets to form a flocculant–MNP–oil droplet composite, and the magnetic transfer of the composite were two key processes that enhanced the separation of cutting emulsions. Specifically, the interactions among MNPs, flocculants, and oil droplets were important in the magnetization process, which was controlled by the structures and properties of the three components. Under the magnetic field, the magnetized flocculant–MNP–oil droplet composites were considerably accelerated and separated from water, and the sludge was simultaneously compressed. Thus, this study expands the applicability of magnetic separation techniques in the treatment of complex waste cutting emulsions.     

Fulvic acid removal by nanoparticle TiO2 using a submerged membrane photocatalysis reactor

The degradation of fulvic acid（FA） by nanoparticle TiO2 in a submerged membrane photocatalysis（SMPC） reactor was studied. In this reactor, photocatalytic oxidation and membrane separation co-occured. The continuous air supplier provided O2 for the photocatalytical reaction and mixed the solution through an airflow controller. The particle TiO2 could automatically settle due to gravity without particle agglomeration so it could be easily separated by microfiltration（MF） membrane. It was efficient to maintain high flux of membranes. The effects of operational parameters on the photocatalytic oxidation rate of FA were investigated. Results indicated that photocatalyst at 0.5 g/L and airflow at 0.06 m^3/h were the optimum condition for the removal of fulvic acid, the removal efficiency was higher in acid media than that in alkaline media. The effects of different filtration duration on permeate flux rate of MF with P25 powder and with nanoparticle TiO2 were compared. Experimental results indicated that the permeate flux rate of MF was improved and the membrane fouling phenomenon was reduced with the addition of nanoparticle TiO2 catalyst compared with conventional P25 powder. Therefore, this submerged membrane photocatalysis reactor can faciliate potential application of photocatalytic oxidation process in drinking water treatment.     

跨界原生质体融合工程菌株改进合成制药废水生物处理的有效性研究

用常规生物法处理合成制药废水难以去除持久性有机污染物POPs，且存在不能稳定达标的问题，应通过用跨界原生质体融合技术，构建出具有高降解性、高絮凝性、高适应性的基因工程菌株来解决上述问题。为检验基因工程茵的有效性，对基因工程茵进行了抗生素遗传性能鉴定和电子显微镜(SEM)的形态鉴定，并在制药废水的污水处理厂进行了基因工程茵的培养和接种。结果表明：基因工程菌株能成功取代原有土著茵并具有显著的优点。     

纳米TiO_2-CS微球光催化降解亚甲基兰的研究

将用化学方法改性后的纳米TiO2与壳聚糖(CS)共混,通过反相悬浮、交联制备了纳米TiO2-CS微球光催化剂,以亚甲基兰为对象,紫外灯为光源,研究了亚甲基兰的初始浓度、光照时间、不同pH值、纳米TiO2的含量、催化剂用量对亚甲基兰光降解率的影响。结果表明:纳米TiO2-CS微球能显著地降解亚甲基兰,且易于回收、能重复使用,为其实际应用提供了有价值的参数。     

Effect of oxide nanoparticles on the morphology and fluidity of phospholipid membranes and the role of hydrogen bonds

Engineered oxide nanoparticles (NPs) are widely applied in insulators, catalyzers, paints, cosmetic products, textiles and semiconductors. Their attachment on cell membrane may lead to cytotoxicity. The effects of Al₂O₃, Fe₂O₃, SiO₂, TiO₂ and ZnO NPs on membrane integrity and fluidity were studied using giant or small unilamellar vesicles in this study. Al₂O₃ and SiO₂ NPs disrupted the oppositely charged membrane, indicating the important role of electrostatic attraction. However, Fe₂O₃, TiO₂ and ZnO NPs did not cause serious membrane disruption as Al₂O₃ and SiO₂ NPs. Membrane fluidity was evaluated by the generalized polarity (GP) values of Laurdan fluorescent emission. SiO₂ NPs induce the membrane gelation of both positively and negatively charged membrane. Al₂O₃ and ZnO NPs induced the gelation of the oppositely charged membrane, but did not cause obvious membrane gelation to the like charged membrane. The phospholipid molecular structural changes after NP exposure were analyzed by Fourier transform infrared (FT-IR) spectroscopy. FT-IR spectra revealed the hydrogen bond formation between NPs and the carbonyl/phosphate groups of phospholipids. Al₂O₃ and SiO₂ NPs showed strongest evidence of hydrogen bonding on their FT-IR spectra. It was consistent with the microscopic observation and fluorescent data that Al₂O₃ and SiO₂ NPs caused more serious membrane disruption and gelation. This study on membrane damage provides further knowledge on the cytotoxicity of nanomaterials and the safety of NP application.     

不同pH下纳米铁镍颗粒对生物降解苯酚的影响

研究不同pH(8.0、6.0和3.0)下金属纳米颗粒(Fe和Fe/Ni)对纺锤芽孢杆菌(BFN)降解苯酚的影响.实验结果发现pH在8.0和6.0时投加2种金属纳米颗粒(Fe和Fe/Ni)对BFN降解苯酚有促进作用,其原因主要是纳米颗粒在水中持续腐蚀产生H2,为BFN降解苯酚提供电子,促进BFN的生长.但在pH=3.0时,只有BFN-纳米Fe耦合体系才使苯酚得到部分降解,主要是因为纳米Fe颗粒与水反应产生OH-,使pH值有所升高,更适宜BFN的生长,同时提供电子供体H2促进BFN对苯酚的利用.扫描电镜(SEM)和能谱分析(EDS)数据证实金属纳米颗粒(Fe和Fe/Ni)在反应后附着在微生物表面,但微生物的表面形态并未发生显著改变.因此,纳米金属颗粒虽然通过附着影响微生物的活性,但其在腐蚀过程中产生的H2将作为电子供体而被BFN所利用,综合作用的结果是有利于BFN的生长进而提高苯酚的降解速率.     

Interface-mediated synthesis of monodisperse ZnS nanoparticles with sulfate-reducing bacterium culture

We have created a new method of ZnS nanospheres synthesis. By interface-mediated precipitation method (IMPM), monodisperse ZnS nanoparticles was synthesized on the particle surface of sulfate-reducing bacterium nutritious agar culture. Sulfate-reducing bacterium (SRB) was used as a sulfide producer because of its dissimilatory sulfate reduction capability, meanwhile produced a variety of amino acids acting as templates for nanomaterials synthesis. Then zinc acetate was dispersed into nutritious agar plate. Subsequently agar plate was broken into particles bearing much external surface, which successfully mediated the synthesis of monodisperse ZnS nanoparticles. The morphology of monodisperse ZnS nanospheres and SRB were examined by scanning electron microscopy (SEM), and the microstructure was investigated by X-ray diffraction (XRD). The thermostability of ZnS nanoparticles was determined by thermo gravimetric-differential thermo gravimetric (TG-DTG). The maximum absorption wavelengh was analysed with an ultraviolet-visible spectrophotometer within a range of 199–700 nm. As a result, monodisperse ZnS nanoparticles were successfully synthesized, with an average diameter of 80 nm. Maximum absorption wavelengh was 228 nm, and heat decomposed temperature of monodisperse ZnS nanoparticles was 596°C.     

Interface-mediated synthesis of monodisperse ZnS nanoparticles with sulfate-reducing bacterium culture

We have created a new method of ZnS nanospheres synthesis. By interface-mediated precipitation method (IMPM), monodisperse ZnS nanoparticles was synthesized on the particle surface of sulfate-reducing bacterium nutritious agar culture. Sulfate-reducing bacterium (SRB) was used as a sulfide producer because of its dissimilatory sulfate reduction capability, meanwhile produced a variety of amino acids acting as templates for nanomaterials synthesis. Then zinc acetate was dispersed into nutritious agar plate. Subsequently agar plate was broken into particles bearing much external surface, which successfully mediated the synthesis of monodisperse ZnS nanoparticles. The morphology of monodisperse ZnS nanospheres and SRB were examined by scanning electron microscopy (SEM), and the microstructure was investigated by X-ray diffraction (XRD). The thermostability of ZnS nanoparticles was determined by thermo gravimetric-differential thermo gravimetric (TG-DTG). The maximum absorption wavelengh was analysed with an ultravioletvisible spectrophotometer within a range of 199-700 nm. As a result, monodisperse ZnS nanoparticles were successfully synthesized, with an average diameter of 80 nm. Maximum absorption wavelengh was 228 nm, and heat decomposed temperature of monodisperse ZnS nanoparticles was 596℃.     

ZnO-PMMA复合材料光催化去除水中低浓度氨氮

通过水热法制备纳米ZnO,采用热粘固法成功地将其负载于聚甲基丙烯酸甲酯(PMMA)微球表面,并对ZnO-PMMA复合材料光催化去除水中低浓度氨氮的能力进行了考察.同时,探究了负载比例、初始氨氮浓度、催化剂浓度和pH对低浓度氨氮去除效率的影响.实验结果显示,PMMA改善了纳米ZnO的分散性和光催化能力,ZnO-PMMA能够有效地催化去除氨氮废水.在汞灯照射下,当pH=12、温度为30℃时,1 g·L~(-1)的催化剂(ZnO-PMMA)对50 mg·L~(-1)的氨氮废水去除率达到66%,且反应产物硝氮和亚硝氮含量较低,体现了该催化剂具有将氨氮转化为N2的良好的光催化降解能力.同时,纳米材料可以简单方便地回收,减轻了对环境的潜在影响,符合绿色化学的原则.     

Characterization of aluminium-based water treatment residual for potential phosphorus removal in engineered wetlands

Aluminium-based water treatment residual (Al-WTR) is the most widely generated residual from water treatment facilities worldwide. It is regarded as a by-product of no reuse potential and landfilled. This study assessed Al-WTR as potential phosphate-removing substrate in engineered wetlands. Results indicate specific surface area ranged from 28.0 m² g⁻¹ to 41.4 m² g⁻¹. X-ray Diffraction, Fourier transform infrared and energy-dispersive X-ray spectroscopes all indicate Al-WTR is mainly composed of amorphous aluminium which influences its phosphorus (P) adsorption capacity. The pH and electrical conductivity ranged from 5.9 to 6.0 and 0.104 dS m⁻¹ to 0.140 dS m⁻¹ respectively, showing that it should support plant growth. Batch tests showed adsorption maxima of 31.9 mg P g⁻¹ and significant P removal was achieved in column tests. Overall, results showed that Al-WTR can be used for P removal in engineered wetlands and it carries the benefits of reuse of a by-product that promotes sustainability.