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.     

Shrunken Pore Syndrome Is Frequently Occurring in Severe COVID-19

A selective decrease in the renal filtration of larger molecules is attributed to the shrinkage of glomerular pores, a condition termed Shrunken Pore Syndrome (SPS). SPS is associated with poor long-term prognosis. We studied SPS as a risk marker in a cohort of patients with COVID-19 treated in an intensive care unit. SPS was defined as a ratio < 0.7 when the estimated glomerular filtration rate (eGFR), determined by cystatin C, calculated by the Cystatin C Caucasian-Asian-Pediatric-Adult equation (CAPA), was divided by the eGFR determined by creatinine, calculated by the revised Lund–Malmö creatinine equation (LMR). Clinical data were prospectively collected. In total, SPS was present in 86 (24%) of 352 patients with COVID-19 on ICU admission. Patients with SPS had a higher BMI, Simplified Physiology Score (SAPS3), and had diabetes and/or hypertension more frequently than patients without SPS. Ninety-nine patients in the total cohort were women, 50 of whom had SPS. In dexamethasone-naïve patients, C-reactive protein (CRP ), TNF-alpha, and interleukin-6 did not differ between SPS and non-SPS patients. Demographic factors (gender, BMI) and illness severity (SAPS3) were independent predictors of SPS. Age and dexamethasone treatment did not affect the frequency of SPS after adjustments for age, sex, BMI, and acute severity. SPS is frequent in severely ill COVID-19 patients. Female gender was associated with a higher proportion of SPS. Demographic factors and illness severity were independent predictors of SPS.     

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.     

壳聚糖硬脂酸盐制备新方法及其结构性能研究

以固体壳聚糖醋酸盐为原料,水为反应介质,制备了壳聚糖硬脂酸盐。通过红外光谱、X-射线衍射、电子扫描显微镜等对壳聚糖硬脂酸盐的结构进行表征,并考察了其油脂吸附性能。实验结果表明:壳聚糖硬脂酸盐的制备适宜条件为:原料物质的量比1:1,反应温度70⁷5℃,反应时间30 min;产品微观结构表面粗糙、多空隙;在弱酸和中性条件下,壳聚糖硬脂酸盐的油脂吸附量比壳聚糖提高3⁵倍,不受介质pH影响。新壳聚糖硬脂酸盐制备方法无需调节反应介质pH,无有机溶剂,反应快,产品易抽滤、洗涤,产率达85%以上,便于规模生产。      

偕胺肟基团功能化共轭介孔聚合物用于可监控快速海水提铀

海水提铀是核能可持续发展的重要保障之一。快速提铀材料凭借短吸附周期可减少生物污损、老化而延长使用寿命,因此优化吸附周期可获得更高的提铀效率和经济效益。为此,本研究设计了一种偕胺肟修饰的共轭介孔聚合物（CMPAO）用于可监控的快速海水提铀。以具有优良聚集诱导发光性质的三苯胺和修饰有偕胺肟的芴衍生物为构建单元合成吸附材料,UO2+2被偕胺肟基团捕捉后,经共振能量转移增强CMPAO的电化学发光（ECL）信号,从而实现吸附过程的监测,以确定最优的吸附周期。结果表明：CMPAO在铀酰溶液（5×10-5 mol/L）中可在20 min内达到吸附平衡,对U的吸附容量为1825 mg/g;在真实海水中,3 d即可基本完成吸附过程,CMPAO对U的吸附容量达到16 mg/g,同时CMPAO在海水中可实现铀吸附量与ECL强度的正相关,能够实时监测吸附过程,指示吸附量的变化,以确定最优吸附周期。     

Interaction between zinc dialkyldithiophosphate and amine

This paper reports work on complex formation from ZDP and various aliphatic amines, and their equilibrium states in oil, adsorptivities and antiwear properties are investigated. Complex formation from ZDP and amine was proven by isolation and identification of solid crystals, and various complexes were found from mono- and diamines. The complex from monoamine has lower adsorptivity than free ZDP, while the poorer adsorptivity of ZDP/monoamine complex makes its antiwear property worse.     

变压吸附制氮技术的发展和应用

综述了变压吸附技术的原理、发展及碳分子筛和沸石分子筛两种吸附剂变压吸附技术制氮的国内外研究进展,提出了变压吸附技术制氮的发展方向。     

Improvement of antioxidation and antiwear properties of polyalphaolefin oils

Polyalphaolefin-based lubricating oils were tested on a four-ball tester, and in a stability test, with antiwear and antioxidant additives of different types, along with other (petroleum and alkylbenzene) base oils and additives. Antioxidant additives for PAOs essentially influence their thermo-oxidation stability. It was found that binary inhibitors increased thermo-oxidation stability effectively. In the antiwear tests, the addition of additives to PAOs sharply decreased wear scar diameters. A significant difference was observed in the action of small concentrations of antiwear additives as between PAO, alkylbenzene and mineral oils. Explanations of this behaviour are put forward.     

Heparin-Functionalized Adsorbents Eliminate Central Effectors of Immunothrombosis,including Platelet Factor 4, High-Mobility Group Box 1 Protein and Histones

Inflammation and thrombosis are closely intertwined in numerous disorders, including ischemic events and sepsis, as well as coronavirus disease 2019 (COVID-19). Thrombotic complications are markers of disease severity in both sepsis and COVID-19 and are associated with multiorgan failure and increased mortality. Immunothrombosis is driven by the complement/tissue factor/neutrophil axis, as well as by activated platelets, which can trigger the release of neutrophil extracellular traps (NETs) and release further effectors of immunothrombosis, including platelet factor 4 (PF4/CXCL4) and high-mobility box 1 protein (HMGB1). Many of the central effectors of deregulated immunothrombosis, including activated platelets and platelet-derived extracellular vesicles (pEVs) expressing PF4, soluble PF4, HMGB1, histones, as well as histone-decorated NETs, are positively charged and thus bind to heparin. Here, we provide evidence that adsorbents functionalized with endpoint-attached heparin efficiently deplete activated platelets, pEVs, PF4, HMGB1 and histones/nucleosomes. We propose that this elimination of central effectors of immunothrombosis, rather than direct binding of pathogens, could be of clinical relevance for mitigating thrombotic complications in sepsis or COVID-19 using heparin-functionalized adsorbents.     

Silk Sericin Enrichment through Electrodeposition and Carbonous Materials for the Removal of Methylene Blue from Aqueous Solution

The recycling and reuse of biomass waste for the preparation of carbon-based adsorbents is a sustainable development strategy that has a positive environmental impact. It is well known that a large amount of silk sericin (SS) is dissolved in the wastewater from the silk industry. Utilizing the SS instead of discharging it into the environment without further treatment would reduce environmental and ecological problems. However, effective enrichment of the SS from the aqueous solution is a challenge. Here, with the help of carboxymethyl chitosan (CMCS), which can form a gel structure under low voltage, an SS/CMCS hydrogel with SS as the major component was prepared via electrodeposition at a 3 V direct-current (DC) voltage for five minutes. Following a carbonization process, an SS-based adsorbent with good performance for the removal of methylene blue (MB) from an aqueous solution was prepared. Our results reveal that the SS/CMCS hydrogel maintains a porous architecture before and after carbonization. Such structure provides abundant adsorption sites facilitating the adsorption of MB molecules, with a maximum adsorptive capacity of 231.79 mg/g. In addition, it suggests that the adsorption is an exothermic process, has a good fit with the Langmuir model, and follows the intra-particle diffusion model. The presented work provides an economical and feasible path for the treatment of wastewater from dyeing and printing.