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采用静态与动态实验相结合的方法,研究了2,4-二氯苯酚在黄土性土壤中的吸附和解吸规律,测定吸附动力学和吸附热力学曲线,获得吸附热力学模型。研究表明,2,4-二氯苯酚在黄土性土壤中吸附等温线可用Freundlich和Langmuir方程描述,其中q0描述饱和吸附量,由Langmuir吸附等温式拟合数据可以看出:TS-2土的饱和吸附量大于TM-1土(这是因为2,4-二氯苯酚在土壤中的吸附量与土壤中有机质的含量密切相关);由Freundlich吸附等温式拟合得到的常数,1/n均1,证明是优惠吸附;根据吸附符合Langmuir方程,说明在土壤表面,2,4-二氯苯酚为单分子层吸附;吸附-解吸具有一定的可逆性,黄土性土壤对2,4-二氯苯酚的吸附能力不强,2,4-二氯苯酚极易穿透土壤,污染地下水。 相似文献
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《广东化工》2021,48(14)
本实验主要研究了草甘膦在树木园土壤中的环境化学行为,分别从烷基多苷(APG)浓度、土壤p H对草甘膦吸附解吸的影响进行了试验。结果表明,吸附实验中,APG浓度对草甘膦的吸附没有表现出明显影响,而随p H(3~9)的增大吸附量逐渐减小。草甘膦在树木园土壤中的吸附在实验开始8小时之内,吸附量明显上升。解吸实验中,解吸量随p H的升高而下降。在APG浓度较低的情况下,随APG浓度的增大,解吸量随之上升,APG/Gly等于0.75时解吸量达到最大值,浓度比达1后,解吸量变化趋于平缓。解吸动力学试验中,解吸量在实验开始12小时后趋于平缓,草甘膦在树木园土壤上的解吸量与吸附量呈一定比例的正相关关系。 相似文献
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近年来,人们对农药在土壤中的吸附-解吸的研究颇为重视,因由此能清楚地了解有关农药在土壤系统中的存在状况。此外,通过定量分析所获得的吸附-解吸的动力学方程,将此方程与农药的降解、迁移模型结合起来,就能预测农药的环境行为,为评价农药的安全性提供依据。本文对目前常用农药的有关吸附-解吸的研究方法进行归类,并比较各方法的特点及适用性,也提出了农药吸附-解吸研究中几个值得注意的问题。 相似文献
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研究了土壤对矸石填充时溶出重金属的吸附性能.通过一系列的试验表明:重金属Mn和As离子均符合Freundlich等温式,Mn和As的饱和吸附量分别为0.0083 mg/g和0.069 μg/g; Mn和As的解吸过程都分为两个阶段,而不同离子的反应阶段时间不同;解吸动力学曲线的快速阶段对应于静电吸附态Mn和As解吸,慢速阶段主要对应于专性吸附态Mn和As的解吸.Mn和As的解吸率分别为2.55% 和0.78%,而解吸因数分别为2.62×10-2和7.9×10-3.由此可知土壤对Mn和As的吸附稳定性都较高,土壤一旦吸附后就不易解吸. 相似文献
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选择长三角地区具有代表性的4种土壤,采用不同浓度的外源Zn溶液进行吸附,用模拟雨水作为解吸剂,研究4种土壤对Zn的吸附-解吸特性,以及Zn的连续解吸特性.结果表明:4种土壤对Zn的吸附量均随吸附平衡浓度的增大而增加,且吸附量与土壤的pH正相关;吸附等温线可以用Freund lich方程和Temkin方程来描述.由Langmu ir方程求得的4种土壤的最大吸附量的大小顺序为:q(青紫泥)>q(滩潮土)>q(乌黄土)>q(黄泥沙田).最大缓冲容量的顺序为:MBC(滩潮土)>MBC(乌黄土)>MBC(青紫泥)>MBC(黄泥沙田).4种土壤对Zn的解吸量均随着解吸平衡浓度的增大而线性增加.连续解吸可提高土壤对Zn的解吸率,但连续解吸数次后,解吸过程趋于稳定. 相似文献
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Richard U. Edgehill G. Q. Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1998,71(1):27-34
The potential of using carbonized slash pine bark as a substitute for activated carbon was examined in this study. The bark was carbonized by slow heating in nitrogen for 6·5 h to 672°C. The BET-N2 surface area, average micropore and mesopore diameter, and micropore volume were 332 m2 g−1 21·7 Å, and 0·125 cm3 g−1, respectively. The adsorption capacities for phenol and pentachlorophenol (PCP) at pH 2 and pH 8 were evaluated. The Langmuir equation provided a slightly better fit than the Freundlich equation to two sets of phenol data. The calculated Freundlich constants, K = 0·41–0·58 mmol/g/(mmol dm−3)1/n and 1/n = 0·30–0·41, were lower and higher, respectively, than literature values for activated carbons. The adsorption capacity of the carbonized bark was much lower for PCP than for phenol. The protonated and anionic PCP isotherms were Type II or III, respectively, in the Brunauer classification. The BET equation provided the best fit to protonated PCP isotherm data. The anionic PCP data were fitted to both the BET model and an equation used in the literature to represent phosphate adsorption on activated carbons. Non-linear regression of the data for both phenol and PCP adsorption with the Freundlich, Langmuir and BET equations generally gave more accurate param-eters, compared with the use of linearized equations to obtain the parameters. © 1998 SCI. 相似文献
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《Gas Separation & Purification》1993,7(4):207-212
Modelling of fixed bed adsorption and desorption kinetics for gas separation and purification is based on the correct representation of mass transport mechanisms on the single-pellet scale. In the case of adsorption it is commonly assumed that pore mass transport within the adsorbent particle is rate limiting. It has been questioned whether this is also true for desorption. Here the exchange step between the adsorbed state on the solid surface and the mobile state within the pore fluid was considered as being the dominant kinetic resistance. Therefore, experimental and theoretical investigations of single component adsorption and desorption of water vapour, n-hexane, cyclohexane and tetrachloroethylene on single pellets of activated carbon were performed. From the results it can be concluded that for most cases of physical gas-phase adsorption as well as desorption the overall kinetics is controlled by mass transport within the pore system of the adsorbent. The exchange step between the adsorbed phase and the fluid phase happens infinitely fast justifying the assumption of adsorption equilibrium at every position along the pellet radius. 相似文献
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采用丙烯酸接枝改性聚丙烯非织造布(PP-g-AA)对阳离子红X-GRL染料进行吸附与解吸,探讨了PP-g-AA对染料的吸附动力学机理、解吸过程和解吸动力学机理,以及基于动态吸附的过滤分离操作,分析了PP-g-AA对染料吸附-解吸再生循环利用的可行性。结果表明:不同初始染料浓度下,PP-g-AA的吸附动力学符合Lagergren's准二级动力学模型和双指数模型;解吸液的最佳配比为表面活性剂质量分数5%,乙醇与水的体积比3∶7,解吸率随吸附量的增大呈现先增大后减小的趋势,解吸符合Lagergren's准二级动力学模型;动态吸附-解吸再生循环10次后,染料的去除率达96%以上,再生循环8次时,PP-g-AA的跨膜压力为37.1 k Pa,水通量最大达38.6 L/(m2·h)。 相似文献
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Environmental hazards caused by halogenated hydrocarbons and increasingly stringent regulations for limiting their emission require comprehensive investigations of these substances. The present work deals with the adsorption and desorption of halogenated hydrocarbons on activated carbon. The results could be useful in the utilization of landfill gases because halogenated hydrocarbons must be removed in order to avoid pollution and the loaded activated carbons have to be regenerated. Activated carbons are well suited to removal and recovery of halogenated hydrocarbons from gas flows. 相似文献
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Qinzhong Feng Zhiyong Zhang Yuhui Ma Xiao He Yuliang Zhao Zhifang Chai 《Nanoscale research letters》2012,7(1):84
The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential
impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are
emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate
the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that
the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating
that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical
reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters
(ΔH
0
, ΔS
0
, and ΔG
0
) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction
was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption
hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the
synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment. 相似文献
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Chang-shen Ye Hong-xing Wang Guo-qiang Huang Ting Qiu 《Chemical Engineering Research and Design》2013
To reduce the high energy consumption during the traditional ordinary distillation process for recycling N,N-dimethyl formamide (DMF), this paper utilized the NKA-II macroporous adsorptive resin in combination with a distillation process to recycle DMF in wastewater. First, the adsorption equilibrium data were measured in the intermittent agitation tank, which showed that the DMF adsorption equilibrium on the NKA-II resin complies with the Henry equation. The dynamic experimental studies indicated that the adsorption temperature has little effect on the adsorption process; the flow rate and the bed height affect the breakthrough time but have little effect on the mass transfer zone. With the combination of the fixed-bed adsorption model and the breakthrough curve, the surface diffusion coefficient of the DMF on the resin in the fixed bed was approximately 3.50 × 10−10 to 1.06 × 10−9 m2 s−1. The simulated values were in good agreement with the breakthrough curves determined by experiments. Furthermore, ethanol was selected as a better desorption agent. The appropriate desorption conditions were determined to be a flow rate of 8.00 × 10−5 m s−1 to 1.58 × 10−4 m s−1 and a temperature of 308–318 K. Under these conditions, the desorption rates were all greater than 99%. Finally, wastewater that contained 5% DMF was used as an example to analyze the energy consumption. The results indicated that the adsorption–distillation process can reduce the energy consumption by 79%. The adsorption–distillation process has a good applicable value for the recovery of DMF in wastewater, especially for wastewater with a low concentration of DMF. 相似文献
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Zhinan Xu} Yong Chen Wenhe Shen Peilin Cen 《Korean Journal of Chemical Engineering》2006,23(1):108-112
S-adenosyl-L-methionine (SAM) is one of most versatile molecules in nature and has wide medical applications. The ion-exchange
separation process of SAM of the extract of yeast cells has many advantages over selective precipitation by picrolonic acid.
Experiments of the dynamic column process of SAM on JK110 resin were carried out in a fixed-bed ion-exchange column. The effects
of different operation parameters on the adsorption and desorption behaviors of SAM were investigated. The results show that
the ion-exchange adsorption of SAM is successfully implemented at 2BV/h, 10 g/L, pH 5.0; the adsorbed SAM in the ion-exchanged
bed is efficiently desorbed by 0.2 N H2SO4 solution at the flow rate of 2BV/h. According to material balance, the recovery yield of SAM for this ion-exchange process
is 90.1%. Finally, this ion-exchange process was successfully scaled up to separate SAM at high yield and purity. 相似文献
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Adsorption and desorption of phosphorus in soils are among the key processes governing its availability to crops. There have been very few studies on the phosphorus adsorption and desorption characteristics of Vertisols. The P adsorption and desorption characteristics of four Vertisols belonging to three agriculturally important soil series were studied. The amounts of P adsorbed by the soils at 0.2µg ml–1 equilibrium solution P concentration was low and ranged from 34.3 to 79.5µg g–1 soil. The phosphate adsorption was very well described by Langmuir and Freundlich isotherms. The P adsorbed by a Vertisol (BR-1) fertilized with different rates of P in the previous season (0, 10, 20 and 40 kg P ha–1) was similar (34.3–41.3µg g–1 soil) indicating little effect of fertilization on P adsorption. The correlation studies indicated that the DTPA-extractable Fe was the most important factor accounting for P adsorption in these soils. Clay and CaCO3 content were found to be relatively less important factors affecting P adsorption in the soils studied.The capacity of the two extractants and EUF (electro-ultrafiltration) to desorb the adsorbed P followed the order: EUF (400V, 80°C)>sodium bicarbonate>EUF (200V, 20°C)>calcium chloride. The average amounts of P desorbed from the four Vertisols using these methods were 74, 63, 50, and 3% respectively of the adsorbed P. In the Begamganj soil, the amount of P desorbed by EUF (400V, 80°C) exceeded 100%, indicating that all of the adsorbed P was desorbable including some native P.In conclusion the results of our study show that the Vertisols studied have low phosphate adsorption capacity and that the P they adsorbed is easily desorbable.Approved for publication as Journal Article No. 983 by International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). 相似文献