预应力螺栓安装的力学性能计算方法

采用张拉器安装螺栓能使其产生比较一致的预紧力,因而得以广泛使用,推导出张拉量和残余预紧力之间的函数关系式,并给出计算实例,为这种预紧螺栓安装法提供了理论依据。     

颗粒物对无电压作用下离子交换膜分离去除铜离子的影响

在无外加电压条件下研究了颗粒物对阳离子交换膜分离去除铜离子效果的影响。选用硅酸、二氧化硅、氧化铝和水杨酸等4种物质作为颗粒物分别进行实验,其添加量均为50 mg/L。Cu2+及其补偿离子K+的浓度分别为0.0787mmol/L(5 mg/L)和0.787 mmol/L,水温为25±1℃,搅拌强度为600 r/min,水力停留时间为12 h。在所述实验条件下运行96 h后,水中无颗粒物干扰时,铜离子去除率为84%;水中存在带负电荷颗粒物(硅酸)和不带电荷颗粒物(二氧化硅和氧化铝)时,铜离子去除率略为下降至81%;而当水中存在带正电荷颗粒物(水杨酸)时,铜离子的去除率进一步下降为79%。研究结果表明带正电荷颗粒物对铜离子的交换去除影响较带负电荷或不带电荷颗粒物大,因为带正电荷颗粒物更易迁移至阳离子交换膜表面甚至进入膜内,并与膜表或膜内离子交换基团结合,从而导致铜离子交换去除明显下降。     

交联壳聚糖对铀的吸附研究

以壳聚糖(CTS)为原料,在碱性条件下用环氧氯丙烷对壳聚糖进行化学改性,制得不溶水的交联壳聚糖(CCTS)。利用CCTS吸附铀(UO22+),探讨吸附动力学规律以及初始浓度,pH值的影响。实验结果表明,CCTS对UO22+的吸附符合Langmu ir吸附等温模型,并能用准二级速率方程对吸附动力学加以描述。当在CCTS为10 mg,pH为3,UO22+初始浓度为50μg/mL条件下,CCTS对UO22+的吸附去除率为98%以上。     

北京和上海典型复合包装废物处置环境影响比较

采用生命周期评价法研究比较了北京和上海两地纸塑铝复合包装处置阶段的环境影响。通过现场和资料调研的方式获得此阶段的能量物质的输入输出和环境外排数据。结果表明:北京和上海两地纸塑铝复合包装处置阶段的环境影响潜值分别为-0.428 Pt和9.776 Pt,其主要集中在气候变化、土地占用和无机物对健康的损害三方面;每提高10%的回收率,其环境影响潜值北京和上海可分别降低5.446 Pt和5.799 Pt;上海地区纸塑铝复合包装处置阶段对环境的影响在任何同回收率的情况都要高于北京地区,其主要原因是上海地区填埋产生的温室气体释放量过大和再生企业距离打包点较远。     

基于因子分析法优选河流水体中氮浓度预测方法的研究

定量的河流水体中氮浓度预测方法有很多种,如何优选出预测精度较高的方法一直是学术界多年来致力于研究的重点。本研究采用因子分析法对预测方法的精度评价指标进行分析,并建立了预测方法精度的评价模型,对回归分析法、神经网络法、灰色系统法和增长率统计法4种水体氮浓度预测方法进行综合评估,优选出精度较高的河流水体氮浓度预测模型——BP神经网络预测模型。结果表明,此评估模型对类似研究具有一定的参考价值,能为选择出合适的河流水体氮浓度预测方法提供依据。     

树脂固载纳米铁对偶氮染料直接湖蓝5B的脱色性能研究

以FeSO4和NaBH4水溶液为前驱溶剂,以聚苯乙烯型阳离子交换树脂为载体,制备了树脂固载的纳米铁,室温下用于对偶氮染料直接湖蓝5B水溶液进行脱色研究。研究结果发现,脱色反应遵循准一级反应动力学,在初始pH为3~10的范围内,反应进行14 m in时,50 mg/L的染料溶液脱色率均能达到83%以上。固载的纳米铁材料可多次重复利用,溶液中释放的铁离子浓度不超过0.1 mg/L。     

运用LCA方法分析污水再生处理的成本效益

运用生命周期评价(LCA)方法,以西安市北石桥污水净化中心的污水处理与再生利用全过程为例进行环境影响评价,通过清单分析、当量计算和权重分析等一系列分析过程,计算出污水处理过程的投入成本及污水再生处理前后对环境的影响,得出污水在经过处理后,能够很大程度上减小其对环境的影响,从而产生环境正效益。该研究明确了污水处理在环境保护中的重要地位,同时对优化污水处理与再生利用工艺过程具有重要的参考价值和指导意义。     

Carbon nanotubes-incorporated MIL-88B-Fe as highly efficient Fenton-like catalyst for degradation of organic pollutants

CNTs were incorporated into MIL-88B-Fe to get a new Fenton-like catalyst (C@M). Fe(II) was introduced in C@M to get a fast initiation of Fenton-like reaction. Fe(II) content in C@M was related with oxygen-containing functional groups on CNTs. C@M shows efficient catalytic degradation of pollutants over a wide pH range. Iron-based metal organic frameworks have been verified to be efficient heterogeneous Fenton catalysts due to their open pore channels and highly uniform distribution of metallic centers. In these catalysts, however, the iron element is mainly in the form of Fe(III), which results in a process required to reduce Fe(III) to Fe(II) to initiate Fenton reaction. To address this problem, carbon nanotubes (CNTs) with electron-rich oxygen-functional groups on the surface were incorporated into the metal organic frameworks (MIL-88B-Fe) to improve Fe(II) content for an enhanced Fenton-like performance. The prepared CNT@MIL-88B-Fe (C@M) showed much stronger catalytic ability toward H₂O₂ than MIL-88B-Fe. The pseudo-first-order kinetic constant for phenol degradation by C@M (0.32 min^–1) was about 7 times that of MIL-88B-Fe, and even higher than or comparable to the values of reported heterogeneous Fenton-like catalysts. Moreover, the Fenton-like system could effectively degrade various kinds of refractory organic pollutants and exhibited excellent catalytic activity over a wide pH range (4–9). XPS analysis confirmed that Fe(II) content of the catalyst gradually increased with CNT loadings. Electron spin resonance analysis showed that the signal intensity (•OH) of C@M was much higher than MIL-88B-Fe, which was consistent with the degradation efficiency of pollutants. Furthermore, the Fe(II) content of the catalyst gradually increased along with the oxygen-functional group content of CNTs. The result demonstrated that oxygen-containing functional groups of CNTs have a significant impact on the enhanced catalytic performance of C@M. This study provides a new insight to enhance Fenton reaction by using nanocarbon materials.     

Comparison of CNT-PVA membrane and commercial polymeric membranes in treatment of emulsified oily wastewater

CNT-PVA membrane was fabricated and compared with polymeric membranes. The separation performance was evaluated by homemade and cutting fluid emulsions. The three membranes show similar oil retention rates. CNT-PVA membranes have higher permeation fluxes compared with polymeric membranes. CNT-PVA membrane shows higher fouling resistance. Membrane separation is an attractive technique for removal of emulsified oily wastewater. However, polymeric membranes which dominate the current market usually suffer from severe membrane fouling. Therefore, membranes with high fouling resistance are imperative to treat emulsified oily wastewater. In this study, carbon nanotube-polyvinyl alcohol (CNT-PVA) membrane was fabricated. And its separation performance for emulsified oily wastewater was compared with two commercial polymeric membranes (PVDF membrane and PES membrane) by filtration of two homemade emulsions and one cutting fluid emulsion. The results show that these membranes have similar oil retention efficiencies for the three emulsions. Whereas, the permeation flux of CNT-PVA membrane is 1.60 to 3.09 times of PVDF membrane and 1.41 to 11.4 times of PES membrane, respectively. Moreover, after five consecutive operation circles of filtration process and back flush, CNT-PVA membrane can recover 62.3% to 72.9% of its initial pure water flux. However, the pure water flux recovery rates are only 24.1% to 35.3% for PVDF membrane and 6.0% to 26.3% for PES membrane, respectively. Therefore, CNT-PVA membrane are more resistant to oil fouling compared with the two polymeric membranes, showing superior potential in treatment of emulsified oily wastewater.     

Enhanced activation of peroxymonosulfate by CNT-TiO2 under UV-light assistance for efficient degradation of organic pollutants

CNT-TiO₂ composite is used to activate PMS under UV-light assistance. Superior performance is due to the enhanced electron-transfer ability of CNT. SO₄•⁻, •OH and ¹O₂ play key roles in the degradation of organic pollutants. In this work, a UV-light assisted peroxymonosulfate (PMS) activation system was constructed with the composite catalyst of multi-walled carbon nanotubes (CNT) - titanium dioxide (TiO₂). Under the UV light irradiation, the photoinduced electrons generated from TiO₂ could be continuously transferred to CNT for the activation of PMS to improve the catalytic performance of organic pollutant degradation. Meanwhile, the separation of photoinduced electron-hole pairs could enhance the photocatalysis efficiency. The electron spin resonance spectroscopy (EPR) and quenching experiments confirmed the generation of sulfate radical (SO₄•⁻), hydroxyl radical (•OH) and singlet oxygen (¹O₂) in the UV/PMS/20%CNT-TiO₂ system. Almost 100% phenol degradation was observed within 20 min UV-light irradiation. The kinetic reaction rate constant of the UV/PMS/20%CNT-TiO₂ system (0.18 min⁻¹) was 23.7 times higher than that of the PMS/Co₃O₄ system (0.0076 min⁻¹). This higher catalytic performance was ascribed to the introduction of photoinduced electrons, which could enhance the activation of PMS by the transfer of electrons in the UV/PMS/CNT-TiO₂ system.