纳米塑料聚苯乙烯对水中铅离子的吸附行为研究

纳米塑料作为一种新兴污染物在水中可长久稳定存在,其表面吸附的重金属对水环境产生了潜在危害.本文研究了纳米塑料聚苯乙烯微球在吸附时间、溶液pH、氯化钠溶液、锰离子、温度等不同实验条件下对铅离子的吸附行为.结果表明,粒径为400 nm的单分散聚苯乙烯微球可快速吸附铅离子,吸附平衡时间约为30 min,吸附率达到53.30%.聚苯乙烯微球对铅离子的吸附动力学符合伪一级动力学,吸附等温线遵循Freundlich模型,吸附过程主要为非线性吸附.随着溶液pH的增加,铅离子平衡吸附量增加,静电作用是影响铅离子在聚苯乙烯微球上吸附的关键因素.增加溶液盐浓度,微塑料发生聚集,比表面积减小,吸附位点减少,铅离子的吸附量显著降低,在3.5%氯化钠溶液中,纳米塑料对铅离子的吸附率仅为7.5%.与重金属锰离子共存,可促进聚苯乙烯微球对铅离子的吸附.升高温度,纳米塑料对铅离子的平衡吸附量增加.     

N,N-双(二硫代羧基)乙二胺对微量络合镍的深度脱除特性研究

以柠檬酸镍(CA-Ni)、酒石酸镍(TA-Ni)、焦磷酸镍(SP-Ni)3种低浓度模拟络合镍废水为研究对象,选用自制的重金属捕集剂N,N-双(二硫代羧基)乙二胺(EDTC),对废水中的Ni进行深度脱除.重点研究了EDTC投加量、初始p H、反应时间对Ni去除效果的影响及螯合沉淀物的沉淀性能和溶出特性,同时分析了EDTC去除络合Ni的机理.研究结果表明,处理初始浓度5 mg·L~(-1)的CA-Ni、TA-Ni、SP-Ni,p H为4~8,EDTC最佳投加量分别为60 mg·L~(-1)、55 mg·L~(-1)和70 mg·L~(-1),PAM(聚丙烯酰胺)为1 mg·L~(-1),反应时间2 min,Ni的出水浓度均低于0.05mg·L~(-1),去除率达99%以上.螯合沉淀物沉降性能好且在弱酸弱碱条件下能稳定存在.红外光谱图和元素分析结果表明:EDTC与Ni发生螯合反应,即EDTC直接脱除络合镍中的Ni2+,并与Ni2+生成更稳定的螯合产物EDTC-Ni,进而有效地去除废水中Ni.     

The biological effect of metal ions on the granulation of aerobic granular activated sludge

As a special biofilm structure, microbial attachment is believed to play an important role in the granulation of aerobic granular activated sludge (AGAS). This experiment was to investigate the biological effect of Ca^2 +, Mg^2 +, Cu^2 +, Fe^2 +, Zn^2 +, and K⁺ which are the most common ions present in biological wastewater treatment systems, on the microbial attachment of AGAS and flocculent activated sludge (FAS), from which AGAS is always derived, in order to provide a new strategy for the rapid cultivation and stability control of AGAS. The result showed that attachment biomass of AGAS was about 300% higher than that of FAS without the addition of metal ions. Different metal ions had different effects on the process of microbial attachment. FAS and AGAS reacted differently to the metal ions as well, and in fact, AGAS was more sensitive to the metal ions. Specifically, Ca^2 +, Mg^2 +, and K⁺ could increase the microbial attachment ability of both AGAS and FAS under appropriate concentrations, Cu^2 +, Fe^2 +, and Zn^2 + were also beneficial to the microbial attachment of FAS at low concentrations, but Cu^2 +, Fe^2 +, and Zn^2 + greatly inhibited the attachment process of AGAS even at extremely low concentrations. In addition, the acylated homoserine lactone (AHL)-based quorum sensing system, the content of extracellular polymeric substances and the relative hydrophobicity of the sludges were greatly influenced by metal ions. As all these parameters had close relationships with the microbial attachment process, the microbial attachment may be affected by changes of these parameters.     

融雪对土壤溶解性有机质溶析作用的影响

利用土壤浸提实验和土柱淋洗实验,考察了化学离子的种类与浓度对进入融雪径流的土壤溶解性有机物(DOM)的含量和光谱学特性的影响,以及不同化学特征的积雪融化过程中土壤DOM的释放规律.土壤浸提实验结果表明,随着Na~+、Mg~(2+)和Ca~(2+)浓度的升高,土壤浸提液中的溶解性有机碳(DOC)浓度显著降低;随着Cl~-、SO_4~(2-)、Mg~(2+)和Ca~(2+)浓度的升高,土壤浸提液中波长254 nm处的紫外吸光度(UV-254)逐渐降低;随着Na~+和Mg~(2+)浓度的升高,土壤浸提液中单位浓度DOC的紫外吸收值(SUVA)值逐渐升高.NO_3~-、SO_4~(2-)和Na~+的浓度过高或过低时,土壤浸提液中DOM的类腐殖酸和类富里酸荧光峰强度较低;随着Cl~-、Mg~(2+)和Ca~(2+)浓度的升高,土壤浸提液中DOM的类腐殖酸荧光峰强度逐渐降低.土柱淋溶实验结果表明,类腐殖酸和类富里酸荧光物质是土壤淋滤液中的主要荧光物质.与纯水相比,融雪水作为淋洗液导致土壤淋滤液中DOC浓度的降低,以及类微生物代谢产物荧光峰强度的增高.冻融交替抑制DOM自土壤解吸进入淋滤液,并且导致土壤淋滤液中芳香族化合物相对含量的降低.     

多元竞争体系下的微界面动力学响应机理研究——以细颗粒泥沙吸附多元重金属离子铅、铜和镉为例

研究微界面动力学响应机理能更好地了解动力学扩散模式的内在机制.通过竞争吸附实验,采用微界面作用模式识别多元重金属离子铅、铜和镉在泥沙颗粒上的扩散模式,探究多元重金属离子的液相浓度和吸附速率变化规律,剖析多元竞争体系下的微界面动力学响应机理.结果显示,10 min前,多元竞争体系下离子的液相浓度和吸附速率变化较大,为快速吸附阶段,与扩散速率较大的膜扩散过程对应.10 min后,离子的液相浓度波动变化,吸附速率变化呈“N型”、“倒N型”、“W型”和“倒W型”特征,吸附解吸交替进行,不同竞争体系离子的液相浓度和吸附速率变化不同,进入孔隙的时间存在差异,此阶段为膜扩散和颗粒内扩散并存,不同竞争体系的离子的颗粒内扩散时间不一致.60 min后, 离子的液相浓度较稳定和吸附速率较小,微界面作用趋于稳定,为扩散速率较小的颗粒内扩散阶段.研究结果可为多元竞争体系的微观界面动力学响应机理提供理论支撑.     

甘肃南部典型城镇PM2.5浓度及水溶性离子特征分析

为研究甘肃南部城镇PM_2.5及水溶性离子（WSIIs）浓度水平,于2019年4月—2020年2月在甘肃成县按季度进行PM_2.5样品采集,分析了其变化特征,并运用相关和主成分分析法进行来源解析.结果表明：采样期间甘肃成县PM_2.5年平均质量浓度为（57.2±26.9） μg·m^-3,表现为冬季>春季>秋季>夏季的季节变化特征,冬季质量浓度约为夏季的1.9倍,全年空气质量优良率为81%,其中夏季达100%.WSIIs质量浓度呈现SO₄^2->NO₃^->Na⁺>NH₄⁺>Ca²⁺> K⁺>Cl^->Mg²⁺的特征.SNA是浓度水平最高的3种水溶性离子,占8种主要水溶性离子浓度的70.1%.ρ（NO₃^-）/ρ（SO₄^2-）平均值为0.6,表明工农业生产及化石燃料燃烧排放等固定源是颗粒物污染的主要来源.新型冠状病毒疫情期间人员管控对PM_2.5和水溶性离子中SNA质量浓度影响显著,PM_2.5平均质量浓度降幅达44.2%.源解析表明,PM_2.5中WSIIs主要来自化石燃料燃烧、生物质燃烧及二次源和道路建筑扬尘等.     

Shellac-coated iron oxide nanoparticles for removal of cadmium(II) ions from aqueous solution

This study describes a new effective adsorbent for cadmium removal from aqueous solution synthesized by coating a shellac layer, a natural biodegradable and renewable resin with abundant hydroxyl and carboxylic groups, on the surface of iron oxide magnetic nanoparticles. Transmission Electron Microscopy (TEM) imaging showed shellac-coated magnetic nanoparticle (SCMN) adsorbents had a core-shell structure with a core of 20 nm and shell of 5 nm. Fourier Transform Infrared Spectroscopic analysis suggested the occurrence of reaction between carboxyl groups on the SCMN adsorbent surface and cadmium ions in aqueous solution. Kinetic data were well described by pseudo second-order model and adsorption isotherms were fitted with both Langmuir and Freundlich models with maximum adsorption capacity of 18.80 mg/g. SCMN adsorbents provided a favorable adsorption capacity under high salinity conditions, and cadmium could easily be desorbed using mild organic acid solutions at low concentration.     

Aminobenzenesulfonamide functionalized SBA-15 nanoporous molecular sieve: A new and promising adsorbent for preconcentration of lead and copper ions

A rapid method for the extraction and monitoring of nanogram level of Pb²⁺ and Cu²⁺ ions using uniform silanized mesopor (SBA-15) functionalized with aminobenzenesulfonamide groups and flame atomic absorption spectrometry (FAAS) is presented. Aminobenzenesulfonamide functionalized SBA-15 was synthesized according to procedure in the literature and the presence of organic groups in the silica framework was demonstrated by FT-IR spectra. The functionalized product showed the BET surface area 110 m²/g and pore diameter 5.1 nm, based on adsorption-desorption of N₂ at 77 K. The effect of several variables such as (amount of adsorbent, stirring time, pH and presence of other ions in the medium) has been studied. Lead and copper were completely extracted at pH greater than 3 after stirring for 10 min. The maximum capacity of the adsorbent was found to be 191.3 ± 1.4 and 155.0 ± 1.0 μg of lead and copper ions/mg functionalized SBA-15, respectively. The preconcentration factor of the method was found to be 200. The detection limit of the technique was 3.4 and 0.4 ng/mL for Pb²⁺ and Cu²⁺, respectively. The applications of this methodology for real samples were examined by various water type, black tea and pepper samples.     

华南地区大气气溶胶中EC和水溶性离子粒径分布特征

利用1988~2010年在华南地区广州、深圳、海口等多地采得的126组样品,初步分析了华南地区不同时段不同地区和水溶性离子成分的浓度变化及其粒径分布特征.结果表明:各站的AEC(等效元素碳)浓度和水溶性无机离子浓度差异较大,Na+和Cl-基本表现为海岛站点>海岸站点>乡村站点>城市站点,其余主要离子成分和AEC则表现为城市站点>乡村站点>海岸站点>海岛.城市站点、乡村站点、海岸站点和海岛站点AEC质量浓度在不同年段随粒径分布的变化趋势比较一致的,基本呈双峰结构,主峰主要位于0.43~0.65mm,次峰主要位于4.7~5.8mm.根据各离子的粒径分布的相似性可以将各种离子的垂直分布形态分为3类:二次离子(SO42-、NO3-和NH4+)呈现明显的三峰分布形态;F-、Ca2+、Mg2+、Na+和Cl-呈双峰分布形态;K+和AEC呈单峰分布形态,主峰位于细粒子模态.各成分浓度随高度的变化则呈现不同的变化规律.降水对气溶胶粒子的清除作用是显著的,尤其是粒径大于1μm的颗粒,而1.1~2.1μm的粒子段是降水清除的关键区.局地污染中,AEC质量浓度随粒径的分布呈现出了很明显的“单峰”结构,且主要集中在次微米段粒径范围内.     

香河夏季PM2.5水溶性无机离子组分特征

2013年6月在中科院香河观测站对大气气溶胶化学组分特征进行研究.对PM2.5和PM10质量浓度进行在线监测,结果表明,观测期间PM2.5和PM10质量浓度均值与方差分别为(151.78±82.48)μg/m3和(250.47±106.99)μg/m3;SNA(SO42-、NO3-、NH4+)占PM2.5质量浓度的44.8%,且大多富集在粒径0.5~2.5μm的细颗粒物中.硫氧化率(SOR)、氮氧化率(NOR)平均值分别为0.35、0.31,SO2主要通过非均相的氧化反应转化为SO42-,NOx主要通过白天光化学反应转化为NO3-;灰霾和轻雾天较高的SOR和NOR表明,灰霾和轻雾天相比于清洁天有较多的SO2、NOx转化为SO42-、NO3-.气流后向轨迹分析表明灰霾和轻雾天空气质量受经过河北、山东及江苏北部气流影响.