Adsorption of oxytetracycline from aquaculture wastewater by modified carbon nanotubes: kinetics,isotherms and thermodynamics

Abstract

In the present study, lanthanum modified carbon nanotubes (La-CNTs) were prepared by the impregnation method and used as adsorbents to remove oxytetracycline (OTC) from aquaculture wastewater. La-CNTs were characterized by SEM, EDS, XRD, BET analysis. The effects of adsorbent dosage, concentration of OTC, adsorption time, pH and interfering ions on the adsorption of OTC by La-CNTs were investigated. The optimum adsorbent dosage, OTC concentration, adsorption equilibrium time and pH for OTC adsorption by La-CNTs are 0.03?g, 20?mg/L, 180?min and 7, respectively. The outcome of the kinetics studies showed a significant linear correlation between the experimental results and the quasi-second-order kinetics model. As an adsorption isotherm model, the Langmuir model showed a very good consistency with the adsorption of OTC by La-CNTs, as the maximum adsorption quantity reached 117.23?mg/g. Through the thermodynamic analysis showed that the adsorption of OTC by La-CNTs was an endothermic process of entropy increase, which occurs spontaneously. The predominant forces promoting this adsorption were van der Waals force, π-π electron donor-acceptor interaction, and electrostatic interaction.     

类金刚石膜对铝合金疏水结构耐久性能影响

为提高2024铝合金疏水及耐蚀性能,利用电化学刻蚀结合等离子体增强化学气相沉积(PECVD)技术,在其表面制备微纳米浮凸疏水结构及类金刚石(DLC)薄膜。利用接触角测量仪、电化学工作站及冲刷试验装置,对不同处理工艺下2024铝合金的疏水、耐蚀及疏水耐久性能进行了研究,并讨论了相应的作用机制。结果表明,电化学刻蚀后2024铝合金与水的静态接触角可达到130o以上,疏水性能显著提高。阻抗结果表明,刻蚀后阻抗模值提高了约8倍,腐蚀电流密度降低了两个数量级,耐蚀性能显著提高。刻蚀后镀非晶态惰性DLC膜的铝合金,其阻抗模值可达1.016×10⁷Ω·cm^-2,可有效阻碍腐蚀过程的电荷转移和离子传输电荷的传递,显著延长疏水结构的耐久性能。     

碳纤维增强聚合物基复合材料回收再利用现状

优异性能的碳纤维增强聚合物基复合材料(CFRPs)在各领域的快速应用发展给复合材料废弃物的回收带来了挑战,尤其是碳纤维增强热固性复合材料.为有效回收碳纤维增强复合材料,促进复合材料产业的可持续发展,本文从多个角度对废弃CFRPs回收再利用研究现状进行综述,包括各回收工艺技术特点、应用领域及可降解树脂实现回收CFRPs的...     

RH冶炼超低碳钢内部脱碳机理及控制工艺

为了研究RH真空处理过程脱碳反应速率及其影响因素,并有效地控制超低碳钢在RH真空处理过程中碳含量的变化,根据热力学、动力学原理建立了RH真空处理脱碳数学模型,通过RH真空处理脱碳数学模型研究了内部脱碳反应深度和脱碳速率之间的关系.模型计算结果表明,反应深度的变化和内部脱碳的反应速率是相对应的,采取预真空操作,提升了反应深度,淡化了前期脱碳转折点的影响,加速了前期的脱碳反应,并在RH处理后期找到了内部脱碳向表面脱碳转变的时间临界点.     

机器学习的可解释性

近年来,机器学习发展迅速,尤其是深度学习在图像、声音、自然语言处理等领域取得卓越成效.机器学习算法的表示能力大幅度提高,但是伴随着模型复杂度的增加,机器学习算法的可解释性越差,至今,机器学习的可解释性依旧是个难题.通过算法训练出的模型被看作成黑盒子,严重阻碍了机器学习在某些特定领域的使用,譬如医学、金融等领域.目前针对机器学习的可解释性综述性的工作极少,因此,将现有的可解释方法进行归类描述和分析比较,一方面对可解释性的定义、度量进行阐述,另一方面针对可解释对象的不同,从模型的解释、预测结果的解释和模仿者模型的解释3个方面,总结和分析各种机器学习可解释技术,并讨论了机器学习可解释方法面临的挑战和机遇以及未来的可能发展方向.     

Adsorption of Chromium (VI) Using an Activated Carbon Derived from Petroleum Coke Feedstock

This study aims to determine the main adsorption mechanism by which chromium (VI) is adsorbed onto the surface of a petroleum-coke sourced activated carbon, a feedstock not prevalent in current literature. The study also aims to produce an activated carbon adsorbent that is both cost-effective and efficient for the removal of chromium (VI) in neutral waters. The efficacy of thermally-treated petroleum coke-activated carbon and nitrogenated petroleum coke-activated carbon using ammonium chloride is compared to the efficacy of commercially available activated carbon. X-ray photoelectron spectroscopy of the activated carbons was obtained both before and after exposure to chromium (VI) for characterization of the materials and confirmation of chromium adsorption. The thermally-treated and nitrogenated activated carbons showed significant enhancement of chromium (VI) removal compared to the non-treated petroleum coke-activated carbon (22.4 mg/g, 21.9 mg/g, and 17.0 mg/g, respectively). However, there was no significant difference observed between the thermally-treated and nitrogenated materials. This indicates that the nitrogenation of the surface does not improve the adsorption capacity of the activated carbon, but rather the thermal treatment itself. X-ray photoelectron spectroscopy showed a significant increase in the alcohol functional groups on the surface of the activated carbon material as a result of the heat-treatment process; from 16.02 atomic percent in the non-treated activated carbon to 26.3 atomic percent in the thermally-treated activated carbon. The alcohol functional groups present on the surface allow for chromium (VI) to undergo reduction to chromium (III) under a similar mechanism to the well-known Jones Oxidation Reaction where the reduced chromium (III) species are then physisorbed to the surface of the activated carbon. XPS results are consistent with this as the chromium species present on the surface of the adsorbent is primarily Cr(OH)₃ (85.6% in the standard AC and 82.5% in the thermally-treated AC). Pseudo-first-order and pseudo-second-order kinetic modeling of the adsorbents indicate that they follow a pseudo-second-order reaction where the rate-limiting step is the chemical sorption of the adsorbate itself.     

硅碳管的特性及使用方法

介绍了硅碳管的特性,并根据作者单位化验室的使用经验,介绍了硅碳管在使用过程中的一些应注意事项。     

Q235低碳钢高温变形过程的动态组织演化分析

通过Gleeble 2000上的热模拟压缩实验,分析了Q235低碳钢在不同热加工参数下的动态组织演化特征.结果表明:应变速率和温度对Q235钢的奥氏体形变特征影响强烈.在相同变形温度下,应变速率的提高可以明显推迟动态再结晶的发生:应变速率较低时,降低温度同样可以延迟动态再结晶的发生.利用定量金相技术及线性、非线性拟合算法,建立了 Q235钢热变形过程的唯像本构关系及组织演化动力学模型,并将其应用于Autoforge3.1有限元软件平台.压缩过程有限元模拟分析表明,分别采用Arrhenius双曲正弦方程描述Q235钢的唯像本构关系及Yada模型表征Q235钢变形过程的平均晶粒尺寸,可以满足预测精度,与实际变形过程基本吻合.     

珠光体对铁素体动态再结晶的影响

利用Gleeble 1500热模拟实验机进行单轴压缩实验,研究了工业纯铁和两种不同含碳量的低碳钢在700℃、不同应变速率条件下的热变形行为.实验结果表明,变形组织中的珠光体对铁素体动态再结晶行为具有重要影响,即增加钢中珠光体含量,可以促进铁素体动态再结晶过程的发生和发展,使得可以发生铁素体动态再结晶的应变速率范围变宽.