Competitive and cooperative adsorption behaviors of phenol and aniline onto nonpolar macroreticular adsorbents

The adsorption behaviors of phenol and aniline on nonpolar macroreticular adsorbents(NDA100 and Amberlite XAD4) were investigated in single or binary batch system at 293K and 313K respectively in this study. The results indicated that the adsorption isotherms of phenol and aniline on both adsorbents in both systems fitted well Langmuir equation, which indicated a favourable and exothermic process. At the lower equilibrium concentrations, the individual amount adsorbed of phenol or aniline on macroreticular adsorbents in single-component systems was higher than those in binary-component systems because of the competition between phenol and aniline towards the adsorption sites. It is noteworthy, on the contrast, that at higher concentrations, the total uptake amounts of phenol and aniline in binary-component systems were obviously larger than that in single-component systems, and a large excess was noted on the adsorbent surface at saturation, which is presumably due to the cooperative effect primarily arisen from the hydrogen bonding or weak acid-base interaction between phenol and aniline.

BINARY COMPETITIVE AND COOPERATIVE ADSORPTION OF AROMATIC COMPOUNDS ON POLYMERIC RESINS

The adsorption behaviors of 2-naphthalenesulfonic acid and aniline on a conventional macroporous resin Amberlite XAD4 and the other two newly-developed hypercrosslinked resins NDA101 and NDAI00 were investigated in a single or binary batch system at 293 K and 313 K, respectively. All the adsorption isotherms of 2-naphthalenesulfonic acid and aniline on the test resins in both systems can fit well with the Langmuir equation, indicating that the adsorption is a favorable process. At the identical equilibrium concentration, the amount of aniline adsorbed on polymeric resins in the single system is higher than that in the binary system because of the competitive adsorption between 2-naphthalenesulfonic acid and aniline on the resin surface. However, the uptake amount of 2-naphthalenesulfonic acid in the binary system is markedly larger than that in the single system, which is presumably due to the cooperative effect arisen from the electrostatic interaction between 2-naphthalenesulfonic acid and aniline adsorbed on the resin surface. The simultaneous adsorption system was proven to be helpful for the selective adsorption toward 2-naphthalenesulfonic acid due to its larger selective index.

Adsorption of sulfonamides on lake sediments

Sulfonamides （SAs） are one class of the most widely used antibiotics around the world. Their fate and transport in the aquatic environment is of great concern. In this study, adsorption of four SAs--sulfadiazine （SD）, sulfamethoxazole （SMZ）, sulfadimethoxine （SDM） and sulfamethazine （SM2）---in single-solute and multi-solute systems on sediments of Dianchi （DC） Lake and Taihu （TH） Lake, China was investigated with batch experi- ments. In the single-solute adsorption system, the Langmuir model and the dual-mode model described the adsorption process better than the Freundlich model. Model fitness was better on DC sediment than on TH sediment. The order of adsorption capacity approximately followed a decreasing order of SDM ~ SD 〉 SM2 〉 SMZ on both sediments, which was likely attributed to the distinctly different water solubility of the four SAs. In the multi-solute system, the order of adsorption capacity was SM2 〉 SDM 〉 SD 〉 SMZ, which was probably related to the compound speciation caused by the pH values of the experimental solution. In the multi-solute system, both competitive and cooperative adsorption played important roles in the adsorption of sulfonamides on sediments.

苯酚和苯胺在超高交联吸附树脂上的共吸附行为

研究了水溶液中苯酚和苯胺在超高交联吸附树脂NDA103、NDA101、NDA100上的竞争吸附和协同吸附行为.实验结果表明,单组分苯酚或苯胺水溶液和双组分共存水溶液中吸附质分子在超高交联吸附树脂上的吸附等温线均符合Langmuir模型.当双组分摩尔比为1∶1时,在较低平衡浓度范围内苯酚和苯胺在树脂上呈现竞争吸附行为,其主导机制是两种吸附质分子对树脂内外表面上π-π作用吸附位点的直接竞争;而在较高平衡浓度范围内呈现协同吸附行为,其主导机制是两种吸附质分子之间的氢键作用.吸附温度由293K升至313K时,苯酚和苯胺在NDA103上的协同吸附作用加强,而在NDA101和NDA100上的协同吸附作用变化不明显.

黄河沉积物对稀土元素的吸附特性研究

针对自然水体的实际情况,开展了黄河沉积物对La3+,Ce3+,Nd3+,Sm3+等4种离子的吸附竞争及其特性研究.结果表明,在较宽的初始浓度范围内(2～11mg·L-1),4种离子之间处于弱吸附竞争或无吸附竞争状态;当初始浓度较高,泥沙浓度较低时,4种离子之间的竞争吸附才得以体现,此时有Sm3+>Nd3+≥La3+>Ce3+的初步吸附竞争能力序列;黄河沉积物对4种离子的吸附受控于pH值,随pH的增加4种离子吸附量逐渐增大,但弱碱性或碱性更有利于吸附;当初始浓度较低(<11mg·L-1)时,主要环境因子对4种离子的吸附竞争影响均不明显;当初始浓度较高(>11mg·L-1)时,各环境因子对4种离子的吸附竞争均有显著影响,总体上,降低离子强度、去除有机质、减小颗粒物粒度,均使Sm3+,Nd3+,La3+等3种离子与Ce3+表现不同的吸附行为.

重金属在松花江沉积物中的竞争吸附行为及pH的影响

研究了复合污染的重金属体系(多元体系)中松花江沉积物吸附Hg2+,Cu2+,Pb2+,Zn2+和Cd2+的热力学和动力学特征,以及pH对重金属吸附量的影响.结果表明:Langmuir吸附等温线可以很好地描述多元体系中沉积物吸附重金属的热力学过程,沉积物吸附5种重金属离子能力的顺序为Hg2+>Cu2+>Pb2+>>Zn2+>Cd2+.在相同的条件下,与单一体系相比,多元体系中Pb2+,Zn2+和Cd2+吸附量减小的程度远远大于Hg2+和Cu2+,Pb2+,Zn2+和Cd2+的吸附量分别减少了31.9%,32.1%和68.1%.一级动力学方程和Langmuir动力学方程可以较好地描述沉积物吸附Hg2+,Cu2+,Pb2+,Zn2+和Cd2+的动力学过程.沉积物对5种重金属的吸附速率为Cd2+>Zn2+>Pb2+>Cu2+>Hg2+.沉积物对Cu2+,Pb2+,Zn2+和Cd2+的吸附能力随pH的降低而减小,pH的降低造成锰氧化物的溶解,可能在一定程度上影响沉积物对重金属的吸附能力.

磺胺类抗生素在辽西河流沉积物中吸附行为研究

为了研究磺胺抗生素在辽西流域沉积物中的吸附行为特性。实验采用OECD Guideline批量平衡法,研究了磺胺甲恶唑在辽西流域沉积物中吸附动力学特性和热力学特性。动力学研究结果表明磺胺甲恶唑在沉积物中吸附动力学过程以容积扩散为主,并且是一个先快速后缓慢的非均相扩散过程。热力学研究表明磺胺甲恶唑在沉积物中的吸附,是一个自发进行的吸热过程,升高温度能够增加磺胺甲恶唑在沉积物中的吸附能力(Kd)。因此,磺胺甲恶唑容易在辽西河流沉积物中吸附残留,应当重视其在水-底泥环境体系中潜在的环境风险。

水动力条件对太湖底泥吸附苯胺性能的影响

应用平衡研究法研究不同水动力条件下苯胺在太湖底泥中的吸附特性及其吸附动力学特征。结果表明,太湖底泥对苯胺具有较强的吸附能力,苯胺在太湖底泥上的最大吸附量为1.131 mg/g,其吸附行为可以用Freundlich型吸附等温式描述。采用Lagrange伪一级动力学和伪二级动力学模型对不同水动力条件下的苯胺吸附动力学数据进行了拟合,结果表明,沉积物对苯胺的吸附动力学更符合Lagrange伪二级动力学模型,且吸附速率随着初始浓度的增大而显著增大。此外,自吸附开始至1 h左右,吸附速率与水动力条件呈明显的正相关性。说明水动力条件的增大,增加了苯胺与沉积物的接触面积,使其扩散系数相对增大,更有利于沉积物对苯胺的表面吸附。自1 h过后,随着时间的延长,吸附速率基本不受水动力条件的影响。

外源重金属离子在黄河沉积物中的竞争吸附

以黄河包头段上游清洁河段的沉积物为吸附剂,采用吸附竞争系数对Pb2+、Cu2+、Zn2+、Cd2+等4种外源重金属离子在黄河沉积物中的竞争吸附进行了探讨。结果表明,当外源重金属离子浓度或体系的离子强度增加时,Pb2+、Cu2+的吸附竞争系数增大,Zn2+、Cd2+的吸附竞争系数减小;不同离子间的竞争吸附有显著的拮抗或协同效应,且此效应的显著程度随体系中离子总量的增加而减弱;黄河沉积物对4种重金属离子的吸附能力排序为:Pb2+≥Cu2+>Zn2+≈Cd2+;温度对外源重金属离子间竞争吸附的影响较为复杂。

河流沉积物对镉和铊的竞争吸附-解吸特性

探讨了不同粒径的表层沉积物对镉(Cd^(2+))和铊(Tl^+)的单一、竞争吸附-解吸特性,并通过对吸附前后沉积物颗粒进行红外光谱和X-光电子能谱分析,探讨了其吸附机理。结果表明,重金属吸附量均随溶液初始质量浓度增加而增大,且随沉积物粒径增大而减小;吸附率随初始质量浓度增加而减小。沉积物对Cd^(2+)的吸附量高于Tl^+,且Cd^(2+)和Tl^+的吸附等温线均符合Langmuir和Freundlich吸附模型。重金属解吸量随吸附量增加而呈指数增加趋势。当重金属Cd^(2+)和Tl^+共存时,各吸附量均有不同程度的下降,而解吸率略高于单一环境。红外光谱分析表明,沉积物中羟基与羧基均参与了Cd^(2+)和Tl^+的吸附;X-射线光电子能谱分析表明,沉积物吸附Cd^(2+)和Tl^+后,金属价态不发生改变。

酚类化合物在黄河水体沉积物中的竞争吸附

研究了邻硝基苯酚、五氯苯酚、2,4-二氯苯酚和2,4-二硝基苯酚等酚类化合物在黄河水体沉积物上的竞争吸附行为。结果表明,水-沉积物体系中,当两种以上的酚类化合物同时存在时,可以产生竞争吸附,竞争吸附能力由该种化合物的吸附能力和吸附速率大小决定,吸附能力和吸附速率大的酚类化合物在水体沉积物中具有较大的竞争吸附能力。

水环境中共存重金属对不同固相物质吸附镉和铜的影响

利用采集的固相物质(生物膜、悬浮颗粒物和沉积物)模拟水环境中多种固相物质共存吸附体系,研究共存金属对固相物质吸附镉和铜的影响.结果表明,各固相物质对镉的吸附均受共存金属(铜和铅)的抑制作用.当悬浮颗粒物吸附镉时,铜和铅的浓度增大,对镉吸附的抑制程度增强;当生物膜和沉积物吸附镉时,铅浓度的增加使得铅抑制镉的吸附作用增强,不同浓度的铜对镉吸附作用的抑制程度差别较小.共存铅对铜吸附有抑制作用,当铅浓度增加时,3种固相物质吸附铜所受的抑制作用均增强,而共存镉对铜的吸附影响较小.即在重金属总浓度较低时,重金属间的相互影响较小;随着重金属总浓度的增加,重金属间的相互影响增强.共存金属浓度变化对悬浮颗粒物吸附铜和镉受到的抑制程度影响较大,共存金属浓度越大,共存金属对悬浮颗粒物吸附镉和铜的抑制作用越强.

Cd^(2+)、Pb^(2+)在湘江流域河床表层沉积物上的吸附特性研究

以湘江流域河床表层沉积物为吸附剂,用于去除水中Cd^(2+)、Pb^(2+),系统研究了沉积物对Cd^(2+)、Pb^(2+)的吸附规律,并探讨了其吸附Cd^(2+)、Pb^(2+)后的化学稳定性。结果表明,当2种离子单独存在时,沉积物对Cd^(2+)、Pb^(2+)均具有较好的吸附效果;当2种离子同时存在时,由于竞争作用,沉积物对Cd^(2+)和Pb^(2+)的吸附量分别减小了约40%和16%。对吸附平衡的溶液进行曝气和用双蒸水清洗吸附饱和的沉积物后,Cd^(2+)、Pb^(2+)的释放比例较小,说明湘江流域河床表层沉积物吸附Cd^(2+)、Pb^(2+)后,其化学稳定性较好。沉积物的SEM、FTIR和XRD分析发现,沉积物结构多孔,表面含有大量—OH、—NH,这些基团在吸附重金属阳离子过程中起重要作用。研究结果表明,湘江流域河床表层沉积物对去除水中的Cd^(2+)、Pb^(2+)有较好的效果,该成果对湘江流域重金属污染控制具有重要参考价值。

基于位点能量分布理论对苯酚和双酚A在沉积物中的竞争吸附研究

河流水体和沉积物中酚类EDCs因其广泛存在和危害持久受到广泛关注,为研究自然条件下河流沉积物上多种酚类EDCs共存的吸附行为,本文以苯酚(phenol)和双酚A(bisphenol A,BPA)为目标污染物,灞河表层沉积物为吸附剂,通过静态吸附实验研究二者在单溶质和双溶质体系下的吸附等温特性,在此基础上,采用位点能量分布理论分析污染物之间的竞争吸附机理.结果表明,相同浓度(1～50 mg·L^(-1))条件下,单溶质体系的苯酚吸附位点主要集中于高能量位;双酚A吸附位点主要分布于低能量区.双溶质体系下,相同浓度的两种物质位点分布函数均随着位点能量的增大而呈指数降低,苯酚下降趋势较为平缓,吸附位点分布更均匀.两种体系相比较,双溶质体系下苯酚平均位点能量和位点能量非均质性分别降低0.867%和3.473%,吸附位点数量降低1.230%;双酚A平均位点能量和位点能量非均质分别增大了6.074%和14.992%,吸附位点数量增大6.389%.即双溶质体系下,二者之间存在一定的竞争吸附,双酚A处于竞争优势.