Influence of anionic, cationic and nonionic surfactants on adsorption and desorption of oxytetracycline by ultrasonically treated and non-treated multiwalled carbon nanotubes

High adsorption capacity of carbon nanotubes (CNTs) may greatly determine the bioavailability and mobility of organic contaminants. The fate of contaminants adsorbed by CNTs may be substantially influenced by surfactants used both in the synthesis and dispersion of CNTs. The aim of this research was to determine the influence of surfactants (nonionic - TX100, cationic - CTAB and anionic - SDBS) on adsorption and desorption of oxytetracycline (OTC) by multiwalled carbon nanotubes (MWCNTs). The surfactants used had a substantial influence on both adsorption and desorption of OTC. The direction of changes depended clearly on the type of surfactant. In case of anionic SDBS, increased adsorption of OTC by MWCNTs was observed. The presence of TX100 and CTAB decreased the adsorption of OTC by MWCNTs significantly. The increase of OTC adsorption after ultrasonic treatment was observed in case of MWCNTs alone and MWCNTs with SDBS and TX100. However, ultrasonic treatment caused OTC adsorption decrease in the presence of CTAB. The change of pH had also an important effect on OTC adsorption in the presence of surfactants. Depending on the surfactant and pH, an increase or decrease of OTC adsorption was observed. The presence of surfactants increased OTC desorption from MWCNTs significantly as follows: SDBS = CTAB < TX100. The results obtained suggest new potential threats and constitute a basis for further research considering the bioavailability and toxicity of antibiotics in the presence of MWCNTs and surfactants.     

表面活性剂在北京碱性土壤中的吸附行为研究

通过静态吸附实验,研究了北京碱性土壤对阴离子表面活性剂SDS、阳离子表面活性剂CTAB和非离子表面活性剂Tween80的吸附行为,考察了温度对表面活性剂吸附的影响.结果表明:7种不同土样对SDS、CTAB和Tween80的吸附等温线均较好地符合Langmuir吸附模式,其吸附能力的大小顺序为2号轻壤土》轻粘土》中壤土》砂壤土》5号轻壤土》重壤土》紧砂土,这主要是由于7种土样的pH、有机质含量和机械组成不同的缘故;同一土壤中,CTAB的吸附量》Tween80的吸附量》SDS的吸附量;温度的升高,不利于SDS和CTAB在土壤中的吸附,而有利于Tween80的吸附.     

CTAB调控绿色合成纳米氧化铁及去除亚硝酸盐

采用阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）改性绿色合成纳米氧化铁（IONP）,提高其稳定性和分散性,并应用于去除水中亚硝酸盐。实验结果表明,亚硝酸盐初始浓度为20 mg·L-1,反应温度 30 ℃时,0.4 mmol·L-1 CTAB改性的绿色合成纳米氧化铁（CTAB-IONP）去除亚硝酸盐的效率最高,为 97.32%,比IONP增加了 23%。通过扫描电镜（SEM）和傅里叶变换红外光谱（FTIR）表征可知,经CTAB改性提高了IONP的稳定性和分散性,同时使其带正电,从而提高了反应活性。IONP对亚硝酸盐的去除反应遵循伪一级动力学,而CTAB-IONP则更符合伪二级动力学。     

Chemically catalyzed uptake of 2,4,6-trinitrotoluene by Vetiveria zizanioides

The efficiency of vetiver grass (Vetiveria zizanioides) in removing 2,4,6-trinitrotoluene (TNT) from aqueous media was explored in the presence of a common agrochemical, urea, used as a chaotropic agent. Chaotropic agents disrupt water structure, increasing solubilization of hydrophobic compounds (TNT), thus, enhancing plant TNT uptake. The primary objectives of this study were to: (i) characterize TNT absorption by vetiver in hydroponic media, and (ii) determine the effect of urea on chemically catalyzing TNT uptake by vetiver grass in hydroponic media. Results showed that vetiver exhibited a high TNT uptake capacity (1.026 mgg(-1)), but kinetics were slow. Uptake was considerably enhanced in the presence of urea, which significantly (p<0.001) increased the 2nd-order reaction rate constant over that of the untreated (no urea) control. Three major TNT metabolites were detected in the roots, but not in the shoot, namely 1,3,5-trinitrobenzene, 4-amino 2,6-dinitrotoluene, and 2-amino 4,6-dinitrotoluene, indicating TNT degradation by vetiver grass.     

Enhanced adsorption of tetracycline using modified second pyrolysis oil-based drill cutting ash

Environmental Science and Pollution Research - In this work, second pyrolysis oil-based drill cutting ash (OBDCA-sp) was modified using NaOH and cetyltrimethylammonium bromide (CTAB), respectively....     

Chemical methods and phytoremediation of soil contaminated with heavy metals

The effects of chemical amendments (calcium carbonate (CC), steel sludge (SS) and furnace slag (FS)) on the growth and uptake of cadmium (Cd) by wetland rice, Chinese cabbage and wheat grown in a red soil contaminated with Cd were investigated using a pot experiment. The phytoremediation of heavy metal contaminated soil with vetiver grass was also studied in a field plot experiment. Results showed that treatments with CC, SS and FS decreased Cd uptake by wetland rice, Chinese cabbage and wheat by 23-95% compared with the unamended control. Among the three amendments, FS was the most efficient at suppressing Cd uptake by the plants, probably due to its higher content of available silicon (Si). The concentrations of zinc (Zn), lead (Pb) and Cd in the shoots of vetiver grass were 42-67%, 500-1200% and 120-260% higher in contaminated plots than in control, respectively. Cadmium accumulation by vetiver shoots was 218 g Cd/ha at a soil Cd concentration of 0.33 mg Cd/kg. It is suggested that heavy metal-contaminated soil could be remediated with a combination of chemical treatments and plants.     

利用香根草进行尾矿植被恢复初探

在分析了南京幕府山采矿尾渣的基本理化性质基础上,研究了香根草在不同矿渣上的适应性,及其对尾矿植被恢复的作用。结果表明,香根草有较强的适应性,在碳质页岩和白云石矿渣上均正常生长,干物产量高,能够有效改变尾矿的地表生态环境,加速植被恢复,是修复、治理采石尾矿的优良植物。     

Effects of EDTA on solubility of cadmium, zinc, and lead and their uptake by rainbow pink and vetiver grass

Rainbow pink (Dianthus chinensis), a potential phytoextraction plant, can accumulate high concentrations of Cd from contaminated soils. Vetiver grass (Vetiver zizanioides) has strong and long root tissues and is a potential phytostabilization plant since it can tolerate and grow well in soils contaminated with multiple heavy metals. Soil was moderately artificially contaminated by cadmium (20 mg/kg), zinc (500 mg/kg), and lead (1000 mg/kg) in pot experiments. Three concentrations of Na2-EDTA solution (0, 5, and 10 mmol/kg soil) were added to the contaminated soils to study the influence of EDTA solution on phytoextraction by rainbow pink or phytostabilization by vetiver grass. The results showed that the concentrations of Cd, Zn, and Pb in a soil solution of rainbow pink significantly increased following the addition of EDTA (p < 0.05). The concentrations of Cd and Pb in the shoots of rainbow pink also significantly increased after EDTA solution was applied (p < 0.05), but the increase for Zn was insignificant. EDTA treatment significantly increased the total uptake of Pb in the shoot, over that obtained with the control treatment (p < 0.001), but it did not significantly increase the total uptake of Cd and Zn. The concentrations of Zn and Pb in the shoots of rainbow pink are significantly correlated with those in the soil solution, but no relationship exists with concentrations in vetiver grass. The toxicity of highly contaminating metals did not affect the growth of vetiver grass, which was found to grow very well in this study. Results of this study indicate that rainbow pink can be considered to be a potential phytoextraction plant for removing Cd or Zn from metal-contaminated soils, and that vetiver grass can be regarded as a potential phytostabilization plant that can be grown in a site contaminated with multiple heavy metals.     

Physiological aspects of vetiver grass for rehabilitation in abandoned metalliferous mine wastes

Physiological aspects of why vetiver grass (Vetiveria zizanioides L.) can be tolerant to heavy metals and be used as an alternative method for rehabilitation of abandoned metalliferous mine wastelands have been investigated. The results showed that high proportions of lead and zinc (Pb/Zn) tailing greatly inhibited the leaf growth, dry matter accumulation, and photosynthesis of leaves, but stimulated the accumulation of proline and abscisic acid (ABA), and enhanced the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), implying that different mechanisms to detoxify active oxygen species (AOS) existed in different parts of plants. Physiological responses to heavy metal treatments differed greatly between roots and shoots. Nitrogen fertilizer application could greatly alleviate the adverse effects of high proportions of Pb/Zn tailing on vetiver grass growth.     

Analysis of phytochelatin complexes in the lead tolerant vetiver grass [Vetiveria zizanioides (L.)] using liquid chromatography and mass spectrometry

Ethylenediamene tetraacetic acid (EDTA) has been used to mobilize soil lead (Pb) and enhance plant uptake for phytoremediation. Chelant bound Pb is considered less toxic compared to free Pb ions and hence might induce less stress on plants. Characterization of possible Pb complexes with phytochelatins (PC_n, metal-binding peptides) and EDTA in plant tissues will enhance our understanding of Pb tolerance mechanisms. In a previous study, we showed that vetiver grass (Vetiveria zizanioides L.) can accumulate up to 19,800 and 3350 mg Pb kg⁻¹ dry weight in root and shoot tissues, respectively; in a hydroponics set-up. Following the basic incubation study, a greenhouse experiment was conducted to elucidate the efficiency of vetiver grass (with or without EDTA) in remediating Pb-contaminated soils from actual residential sites where Pb-based paints were used. The levels of total thiols, PC_n, and catalase (an antioxidant enzyme) were measured in vetiver root and shoot following chelant-assisted phytostabilization. In the presence of 15 mM kg ⁻¹ EDTA, vetiver accumulated 4460 and 480 mg Pb kg⁻¹ dry root and shoot tissue, respectively; that are 15- and 24-fold higher compared to those in untreated controls. Despite higher Pb concentrations in the plant tissues, the amount of total thiols and catalase activity in EDTA treated vetiver tissues was comparable to chelant unamended controls, indicating lowered Pb toxicity by chelation with EDTA. The identification of glutathione (referred as PC₁) (m/z 308.2), along with chelated complexes like Pb-EDTA (m/z 498.8) and PC₁-Pb-EDTA (m/z 805.3) in vetiver root tissue using electrospray tandem mass spectrometry (ES-MS) highlights the possible role of such species towards Pb tolerance in vetiver grass.     

Carbon dioxide adsorption on amine-impregnated mesoporous materials prepared from spent quartz sand

Mesoporous MCM-41 was synthesized using cetyltrimethyl ammonium bromide (CTAB) as a cationic surfactant and spent quartz sand as the silica source. Modification of the mesoporous structure to create an absorbent was then completed using 3-aminopropyltrimethoxysilane. Amine-Quartz-MCM (The A-Q-MCM) adsorbents were then characterized by N₂ adsorption/desorption, elemental analysis (EA), X-ray fluorescence (XRF), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), as well as the carbon dioxide (CO₂) adsorption/desorption performance. In this study, spent quartz sand was utilized to synthesize Quartz-MCM (Q-MCM) and the amine functionalized material, A-Q-MCM, which exhibited a higher uptake of CO₂ at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The surface area, pore volume, and pore diameter were found to be as high as 1028 m²/g, 0.907 cm³/g, and 3.04 nm, respectively. Under the condition of CO₂ concentration of 5000 ppm, retention time of 50 cc/min, and the dosage of 1 g/cm³, the mean adsorption capacity of CO₂ onto A-Q-MCM was about 89 mg/g, and the nitrogen content of A-Q-MCM was 2.74%. The adsorption equilibrium was modeled well using a Freundlich isotherm.

Implications:In this study, spent quartz sand was utilized to synthesize Q-MCM. The amine functionalized material exhibited a higher uptake of CO₂ at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The adsorption equilibrium was modeled well using a Freundlich isotherm.     

介孔铁锆复合氧化物的制备及其对Cr(VI)的吸附性能

以十六烷基三甲基溴化铵(CTAB)为模板剂,以铁(Fe)和锆(Zr)为原料,采用不同Fe/Zr摩尔比例,制备出Fe/Zr复合氧化物吸附剂,对吸附剂的比表面积、孔径分布、晶型结构和零点电位(pHzpc)进行了表征.筛选吸附容量最佳的Fe/Zr吸附剂,考察了吸附条件对其去除水中Cr(VI)效果的影响,探讨了吸附动力学和等温线规律.结果表明:最佳吸附剂的Fe/Zr摩尔比为5/1,具有典型的介孔材料结构特征;该吸附剂在pH为2~8范围内均有良好的除Cr(VI)效率;30 min内即可达到吸附平衡,最大吸附容量为60.90 mg/g.介孔Fe/Zr复合氧化物与现有除Cr(VI)吸附剂相比具有更高的吸附能力,是一种具有较好应用潜力的水处理除Cr(VI)吸附剂.     

强化活性炭吸附技术深度处理焦化废水的可行性研究

采用混凝沉淀、活性炭吸附以及混凝沉淀 活性炭吸附工艺对焦化厂生化出水进行深度处理.单独混凝沉淀或活性炭吸附均可以将水样中COD降到100 mg/L以下,达到国家污水一级排放标准和冷却用水建议标准.活性炭根据不同的材质和进水而表现出不同的吸附性能,对于焦化厂生化出水,煤质炭Ⅰ和果壳炭均表现出良好的吸附效果,并使出水COD＜100 mg/L,但处理成本较高.混凝沉淀 活性炭吸附工艺充分发挥适合去除大分子污染物的混凝沉淀与适宜去除小分子污染物的活性炭吸附技术两者的协同增效作用,吸附单元采用廉价的煤质炭,使出水水质达到个别生产或生活用水回用标准,并且降低深度处理成本.研究结果表明,混凝沉淀 活性炭吸附作为焦化厂生化出水回用工艺是经济可行的.     

污泥含炭吸附剂对挥发性有机废气吸附实验研究

研究了污泥含炭吸附剂对挥发性有机污染物的吸附特性。结果表明,污泥含炭吸附剂对苯系物的吸附为典型的物理吸附,其吸附甲苯等温线的类型系优惠型吸附等温线,表明具有良好的吸附能力;在吸附反应温度为20℃,气体流量为500 mL/m in(停留时间为0.424 s),甲苯浓度为2 700 mg/m3时,甲苯的饱和吸附容量为150.0 mg/g;同时,研究表明污泥含炭吸附剂对苯系物的饱和吸附容量和吸附强弱次序为二甲苯甲苯苯。结果表明污泥含炭吸附剂适合对中低浓度有机废气的吸附净化。     

Enhanced uptake of As, Zn, and Cu by Vetiveria zizanioides and Zea mays using chelating agents

Vetiveria zizaniodes (vetiver) is commonly known for its effectiveness in soil and sediment erosion control. It can tolerate to extreme soil conditions and produce a high biomass even growing in contaminated areas. Zea mays (maize) can also produce a very high biomass with a fast growth rate and possesses some degree of metal tolerance. A greenhouse study was conducted to investigate the feasibility of using vetiver and maize for remediation of arsenic (As)-, zinc (Zn-), and copper (Cu)-amended soils and evaluate the effects of chelating agents on metal uptake by these plants. Vetiver had a better growth (dry weight yield of root and shoot) than maize under different treatment conditions. The effects of different chelating agents on As, Zn, and Cu extraction from soil to soil solution were studied. Among the nine chelating agents used, it was noted that 20 mmol NTA could maximize As and Zn bioavailability, while 20 mmol HEIDA could maximize Cu bioavailability in the soil solution. The surge time in maximizing metal uptake ranged from 16 to 20 days which indicated that timing on plant harvest was an important factor in enhanced metal accumulation. In general, vetiver was a more suitable plant species than maize in terms of phytoextraction of metals from metal-contaminated soil. Application of NTA in As-amended soil and HEIDA in Cu-amended soil at the rate of 20 mmol kg(-1) increased 3-4-fold of As and Cu in shoot of both plants, whereas application of NTA (20 mmol kg(-1)) increased 37- and 1.5-fold of Zn accumulation in shoot of vetiver and maize, respectively. The potential environmental risk of metal mobility caused by chelating agents used for phytoextraction should not be overlooked.     

磁性活性炭的制备及其对水中甲基橙的吸附

活性炭被广泛应用于水处理领域,然而吸附饱和后难以分离和再生的缺点却限制了其应用。本研究采用化学共沉淀法将铁氧化物和活性炭进行复合,制备出同时具有磁分离性能和较强的吸附性能的磁性活性炭复合材料,并对制备的复合材料进行表征,考察其对水中甲基橙的吸附性能。结果表明,制备的磁性活性炭的比表面积为666.72 m2/g,平均孔径为3.16 nm,具有良好的磁性能,在外加磁场下能快速地从溶液中分离出来且磁性能相对稳定,铁氧化物对活性炭吸附性能的影响不大。在温度为25℃、pH为5、吸附剂用量为3 g/L的情况下,吸附3 h后,该磁性活性炭对甲基橙的吸附率可达99.1%,预示着该磁性活性炭在水处理方面具有潜在的应用前景。     

十六烷基三甲基溴化铵改性生物炭对水中镉离子吸附性能的影响

针对水体重金属污染治理问题,通过十六烷基三甲基溴化铵(CTAB)对竹炭(BC)、椰壳炭(CSC)进行改性, 采用傅里叶红外变换光谱(FT-IR)、扫描电镜(SEM)、X射线光电子能谱分析(XPS)和热稳定性分析(TGA)对改性前后的材料进行了表征,探究了投加量、pH对2种改性材料吸附去除水中镉离子性能的影响,并进行了动力学方程拟合及等温吸附模型拟合,探讨了CTAB改性前后活性炭吸附水中镉离子的机理。结果表明：2种CTAB改性材料基本结构虽未改变,但提升了竹炭(BC)和椰壳炭(CSC)的吸附性能,改性后材料的饱和吸附量分别为12.56 mg·g⁻¹(CTAB-BC)、10.71 mg·g⁻¹ (CTAB-CSC),较改性前分别提高了111%和92%;同时,CTAB-BC、CTAB-CSC的吸附量受pH影响较大,对二者的最适pH分别为4~7、6~7;CTAB-BC、CTAB-CSC均能较好地拟合准二级动力学方程(R²_CTAB-BC=0.999 9, R²_CTAB-CSC=0.993 7)及Langmuir模型(R²_CTAB-BC =0.970 3, R²_CTAB-CSC=0.976 8)。通过分析可知,CTAB-CSC、CTAB-BC 2种材料对含镉废水均有较好的去除效果。     

稻壳基活性炭的制备及其对亚甲基蓝吸附的研究

以稻壳为原料,采用K2CO3活化法和H3P04活化法制备了比表面积为1312m^2／g和682m^2／g的活性炭,通过扫描电子显微镜（SEM）、X-射线衍射仪（XRD）对样品进行了表征,并将孔隙发达的活性炭样品用于对亚甲基蓝的吸附,结果表明,K2CO3活化法制备的活性炭样品具有更多的微孔结构;随着亚甲基蓝溶液初始浓度的增加、活性炭吸附时间的延长,亚甲基蓝的去除率呈现逐渐降低和逐渐增大的变化规律,当pH值为6时,活性炭对亚甲基蓝的吸附效果最佳;稻壳基活性炭对亚甲基蓝的吸附等温线符合Langmuir模型,Qm最高可达476．2mg／g;热力学参数△G^0△H^0和△S^0均为负值,表明稻壳基活性炭对亚甲基蓝的吸附是一个自发的放热反应。     

Selective adsorption of phenanthrene dissolved in surfactant solution using activated carbon

Selective adsorption of a hazardous hydrophobic organic compound (HOC) by activated carbon as a means of recovering surfactants after a soil washing process was investigated. As a model system, phenanthrene was selected as a representative HOC and Triton X-100 as a nonionic surfactant. Three activated carbons that differed in size (Darco 20–40 (D20), 12–20 (D12) and 4–12 (D4) mesh sizes) were used in adsorption experiments. Adsorption of surfactant onto activated carbon showed a constant maximum above the critical micelle concentration, which were 0.30, 0.23, 0.15 g g⁻¹ for D20, D12, and D4, respectively. Selectivity for phenanthrene to Triton X-100 was much higher than 1 over a wide range of activated carbon doses (0–6 g l⁻¹) and initial phenanthrene concentrations (10–110 mg l⁻¹). Selectivity generally increased with decreasing particle size, increasing activated carbon dose, and decreasing initial concentration of phenanthrene. The highest selectivity was 74.9, 57.3, and 38.3 for D20, D12, and D4, respectively, at the initial conditions of 10 mg l⁻¹ phenanthrene, 5 g l⁻¹ Triton X-100 and 1 g l⁻¹ activated carbon. In the case of D20 at the same conditions, 86.5% of the initial phenanthrene was removed by sorption and 93.6% of the initial Triton X-100 remained in the solution following the selective adsorption process. The results suggest that the selective adsorption by activated carbon is a good alternative for surfactant recovery in a soil washing process.     

活性炭固定床操作参数的优化

研究了操作参数对活性炭固定床处理有机废气的影响。温度升高，吸附容量下降。湿度的存在会减少活性炭对有机物的吸附容量。适当的操作气速为0.1-0.5m/s，在此范围内，气速与压降在对数坐标上呈线性关系。