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Langmuir adsorption model

About: Langmuir adsorption model is a(n) research topic. Over the lifetime, 24487 publication(s) have been published within this topic receiving 794076 citation(s). The topic is also known as: Langmuir isotherm. more


Journal ArticleDOI: 10.1016/J.JCIS.2005.01.007
V. Vadivelan1, K. Vasanth Kumar1Institutions (1)
Abstract: Batch experiments were carried out for the sorption of methylene blue onto rice husk particles. The operating variables studied were initial solution pH, initial dye concentration, adsorbent concentration, and contact time. Equilibrium data were fitted to the Freundlich and Langmuir isotherm equations and the equilibrium data were found to be well represented by the Langmuir isotherm equation. The monolayer sorption capacity of rice husks for methylene blue sorption was found to be 40.5833 mg/g at room temperature (32 degrees C). The sorption was analyzed using pseudo-first-order and pseudo-second-order kinetic models and the sorption kinetics was found to follow a pseudo-second-order kinetic model. Also the applicability of pseudo second order in modeling the kinetic data was also discussed. The sorption process was found to be controlled by both surface and pore diffusion with surface diffusion at the earlier stages followed by pore diffusion at the later stages. The average external mass transfer coefficient and intraparticle diffusion coefficient was found to be 0.01133 min(-1) and 0.695358 mg/g min0.5. Analysis of sorption data using a Boyd plot confirms that external mass transfer is the rate limiting step in the sorption process. The effective diffusion coefficient, Di was calculated using the Boyd constant and was found to be 5.05 x 10(-04) cm2/s for an initial dye concentration of 50 mg/L. A single-stage batch-adsorber design of the adsorption of methylene blue onto rice husk has been studied based on the Langmuir isotherm equation. more

Topics: Sorption (66%), Freundlich equation (57%), Langmuir adsorption model (53%) more

1,324 Citations

Journal ArticleDOI: 10.1016/S0143-7208(02)00025-6
Chinnaiya Namasivayam1, D. Kavitha1Institutions (1)
01 Jul 2002-Dyes and Pigments
Abstract: The adsorption of Congo Red by coir pith carbon was carried out by varying the parameters such as agitation time, dye concentration, adsorbent dose, pH and temperature. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. Adsorption followed second-order rate kinetics. The adsorption capacity was found to be 6.7 mg dye per g of the adsorbent. Acidic pH was favourable for the adsorption of Congo Red. Desorption studies suggest that chemisorption might be the major mode of adsorption. more

Topics: Freundlich equation (68%), Adsorption (63%), Langmuir adsorption model (59%) more

1,261 Citations

Open accessBook
08 Mar 1996-
Abstract: The Structure of Solid Surfaces and Adsorbate Overlayers. Adsorption I: The Binding of Molecules to Surfaces. Adsorption II: Adsorption Isotherms. Adsorption III: Kinetics of Adsorption. Introduction to Surface Reactions. Rate Laws for Reactions on Surfaces I: Kinetic Models. A Review of Reaction--Rate Theory. Models of Potential Energy Surfaces: Reactions as Curve Crossings and Electron Transfer Processes. Rates and Mechanisms of Surface Reactions. Index. more

Topics: Adsorption (65%), Reactions on surfaces (64%), Polymer adsorption (62%) more

1,234 Citations

Journal ArticleDOI: 10.1021/ES00050A007
Abstract: This study was undertaken to elucidate the interaction mechanism between NOM (natural organic matter) and iron oxide surfaces and to develop a predictive model for NOM adsorption and desorption. Results indicated that ligand exchange between carboxyl/hydroxyl functional groups of NOM and iron oxide surfaces was the dominant interaction mechanism, especially under acidic or slightly acidic pH conditions. This conclusion was supported by the measurements of heat of adsorption (microcalorimetry), FTIR and [sup 18]C NMR analysis, and competitive adsorption between NOM and some specifically adsorbed anions. A modified Langmuir model was proposed in which a surface excess-dependent affinity parameter was defined to account for a decreasing adsorption affinity with surface coverage due to the heterogeneity of NOM and adsorbent surfaces. With three adjustable parameters, the model is capable of describing a variety of adsorption isotherms. A hysteresis coefficient, h, was used to describe the hysteretic effect of adsorption reactions that, at h = 0, the reaction is completely reversible, whereas at h = 1, the reaction is completely irreversible. Fitted values of h for NOM desorption on iron oxide surfaces ranged from 0.72 to 0.92, suggesting that the adsorbed NOM was very difficult to be desorbed at a given pH andmore » ionic composition. 54 refs., 8 figs., 3 tabs.« less more

Topics: Adsorption (59%), Langmuir adsorption model (57%), Desorption (54%) more

1,232 Citations

Journal ArticleDOI: 10.1016/0021-9797(81)90063-1
Mark M. Benjamin1, James O. Leckie2Institutions (2)
Abstract: Adsorption of Cd, Zn, Cu, and Pb onto amorphous iron oxyhydroxide was measured as a function of pH, metal ion concentration, and adsorbent concentration. For each metal, there is a narrow pH band where fractional adsorption increases from near nil to near 100%. For fixed adsorbent concentration, the pH region of the pH-adsorption edge is independent of total adsorbate concentration when adsorption density is less than 10 −5.0 , 10 −3.7 , and 10 −2.3 moles adsorbate per mole Fe for adsorption of Cd, Cu, and Zn, respectively. At larger adsorption densities for these three metals and over the entire range of adsorption densities studied for Pb, the pH region of the adsorption edge becomes more alkaline as total adsorbate concentration increases. In no case did adsorption density attain a maximum, limiting value. The results suggest that the surface is composed of many groups of binding sites. The strength of binding between a given metal and the surface may vary by an order of magnitude or more from one site to another. At small adsorption densities all types of sites are available in excess, and adsorption can be described by the Langmuir isotherm. However, at higher adsorption densities, availability of the strongest binding sites decreases, leading to a decrease in the apparent adsorption equilibrium constant. This phenomenon occurs under conditions where only a few percent of all surface sites are occupied, and is inconsistent with available single-site models. more

Topics: Adsorption (65%), Langmuir adsorption model (64%)

959 Citations

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Guangming Zeng

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