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首页> 外文期刊>Adsorption Science & Technology >Adsorption of Biologically Active Compounds from Aqueous Solutions on to Commercial Unmodified Activated Carbons. Part V. The Mechanism of the Physical and Chemical Adsorption of Phenol
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Adsorption of Biologically Active Compounds from Aqueous Solutions on to Commercial Unmodified Activated Carbons. Part V. The Mechanism of the Physical and Chemical Adsorption of Phenol

机译：生物活性化合物从水溶液到商业未改性活性炭的吸附。第五部分苯酚的物理和化学吸附机理

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The study presented described the influence of temperature as well as pH on phenol adsorption (and the adsorption kinetics) on to three unmodified commercial carbons. The first section of the paper provided a description of the characterization of the carbons employing the most sophisticated method of carbon porosity characterization at present available, i.e. the method of Do and co-workers (the ND method). It was then shown that the ND method leads to the same results as the Density Functional Theory (DFT). The TPD results for D43/1, WD and AHD carbons were then presented and discussed with deconvolution of the peaks being performed. The results obtained together with those already published led to an assignment of the chemical structures of the surface functionalities for all the carbons studied. Thermogravimetric analysis of phenol adsorption indicated that the number of molecules bonded chemically was small. Adsorption of phenol under acidic conditions (pH 1.5) was lower than at neutral pH for all the carbons studied. A description of the corresponding isotherms applying adsorbability, quasi-Freundlich and DA models, together with enthalpy measurements, led to a mechanism for the adsorption of phenol at both pH values. This mechanism was further confirmed by some empirical correlations and by a comparison with data obtained recently for modified chemically carbons. Some new correlations between the properties of the carbon surface and the constants characterizing the process of phenol adsorption suggested recently were extended from data which had been measured for six carbons initially. Analysis of the average hysteresis on the adsorption/desorption isotherms, as well as a comparison of phenol adsorption under oxic and anoxic conditions, led to a mechanism for the irreversible adsorption of phenol. It was suggested that such irreversibility resulted from two effects: the creation of strong complexes between the phenol molecule and surface carbonyl and lactone groups, as well as polymerization. The latter effect arose from the ability of carbon to adsorb oxygen from solution and form superoxo ions. A mechanism for such polymerization was proposed. Finally, the kinetics of the process were considered. The diffusion coefficients were calculated from an application of the analytical solution of Fick's law of diffusion for adsorption in cylindrical particles. It was shown that phenol diffusion occurs via a mixed process involving the carbon surface and pores. The diffusion energy obtained was correlated with the values for the physicochemical parameters of the carbons studied. It was concluded that the mechanism of phenol adsorption was determined not only by so-called 'π-π interactions' and 'donor-acceptor complex' formation, but also by a 'solvent effect' balancing the influence of the two above-mentioned factors, this solvent effect being strongly dependent on the temperature.
机译：提出的研究描述了温度和pH值对苯酚在三种未改性的商品碳上的吸附（和吸附动力学）的影响。本文的第一部分介绍了使用目前可用的最复杂的碳孔隙率表征方法（即Do和同事的方法（ND方法））表征碳的方法。然后表明，ND方法得出的结果与密度泛函理论（DFT）相同。然后介绍和讨论了D43 / 1，WD和AHD碳的TPD结果，并对峰进行了反卷积。与已经发表的结果一起获得的结果导致对所研究的所有碳的表面官能度的化学结构进行了分配。苯酚吸附的热重分析表明，化学键合的分子数量很少。对于所有研究的碳，在酸性条件（pH 1.5）下苯酚的吸附均低于在中性pH下的吸附。通过应用准吸附性，准Freundlich模型和DA模型对相应的等温线进行了描述，以及焓的测量，得出了在两个pH值下都可以吸附苯酚的机理。通过一些经验相关性以及与最近获得的有关化学修饰碳的数据进行比较，进一步证实了这一机理。碳表面的性质与表征苯酚吸附过程的常数之间的一些新的相关性最近从最初对六个碳进行测量的数据得到了扩展。对吸附/解吸等温线的平均滞后的分析，以及在有氧和无氧条件下苯酚吸附的比较，导致了不可逆地吸附苯酚的机理。有人提出，这种不可逆性是由两个作用引起的：在酚分子与表面羰基和内酯基团之间形成强络合物，以及聚合反应。后者的影响是由于碳从溶液中吸收氧并形成超氧离子的能力。提出了这种聚合的机理。最后，考虑了该过程的动力学。扩散系数是通过应用Fick扩散定律的解析解来吸收圆柱状颗粒而计算出的。结果表明，苯酚扩散是通过涉及碳表面和孔的混合过程而发生的。获得的扩散能量与所研究碳的物理化学参数的值相关。可以得出结论，苯酚吸附的机理不仅取决于所谓的“π-π相互作用”和“供体-受体配合物”的形成，而且还取决于平衡上述两个因素影响的“溶剂效应”。 ，这种溶剂效应在很大程度上取决于温度。

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