Adsorption of Gallic Acid from Aqueous Solution Using Fixed Bed Activated Carbon Columns

Naturally occuring matter (NOM), a heterogeneous mixture of complex organic compounds, is invariably present in all surface and ground waters. These materials act as substrate for the growth of bacteria in the distribution system. The disinfection of such water by chlorination produces disinfection by products consisting of several halogenated compounds which are toxic and carcinogenic. As gallic acid is the building block of most NOM, its adsorptive removal from water has been studied using activated carbon columns. The operating variables studied are the hydraulic loading rate (HLR), bed depth (Z), and the feed concentration (C_o). The breakthrough curves are S-shaped and the breakthrough time increases with increasing Z and decreases with increasing HLR and C_o. The adsorption increases with increasing HLR and is maximum around HLR = 8 m³/hr/m². The column design parameters such as the critical bed depth and the depth of the mass transfer zone (MTZ) as calculated using the bed depth service time (BDST) approach are found to agree fairly closely with the experimental values. MTZ is smaller for the carbon cloth indicating its better adsorption characteristics. The adsorption column parameters such as the treated volume and the mass of the carbon required for a desired effluent concentration have been determined from the column data.     

Auto-cyclic reactor: Design and evaluation for the removal of unburned methane from emissions of natural gas engines

A non-adiabatic fixed bed auto-cyclic reactor (ACR) consisting of two counter-current concentric compartments was designed and built for removing low concentrations of methane from exhaust gases from natural gas engines. The length was based on simulations by a simple heterogeneous one dimensional model using literature parameters and kinetic data, while the diameter was selected to assure a linear fluid velocity between 0.5 and 2 m/s. Its innovative design consists of a judicious combination of 14 longitudinal fins welded to the outlet part of inner reactor compartment to maximize the heat transfer to the inlet section and highly active pellet type catalyst filling the space between fins to lower the ignition temperature.The experimental ACR pilot unit was loaded by a combination of highly active laboratory prepared catalysts: palladium/alumina pellets and palladium/alumina coated cordierite monoliths. The efficiency of methane removal from air and from synthetic exhaust gas containing 7 vol% CO₂ and 14 vol% H₂O was evaluated under a wide range of operating conditions: temperature from 290 to 500 °C, methane concentration between 500 and 3800 ppm. The reactor performance was monitored in terms of axial temperature profiles and methane conversion both in transient and steady state conditions.Reproducible performance of the ACR was observed even after 1200 h of cumulative operation and complete methane removal was obtained at relatively low temperatures.To simulate the obtained experimental data, a heterogeneous one-dimensional model was developed to suit the final reactor configuration using actual laboratory determined kinetic data. The model described adequately the experimental temperature profiles and methane conversion when heat transfer between the reactor compartments and heat loss were taken into account.     

Sorption dynamics in fixed‐beds of inert core spherical adsorbents including axial dispersion and Langmuir isotherm

The effects of axial dispersion and Langmuir isotherm on transient behavior of sorption and intraparticle diffusion in fixed‐beds packed with monodisperse shell‐type/inert core spherical sorbents are studied. The system of partial differential equations of the mathematical model is solved numerically using finite difference methods. Results are presented in the form of breakthrough curves for adsorption and desorption processes. Results reveal that the shape of the breakthrough curves is influenced by both hydrodynamic and kinetic factors. Hydrodynamic factor is governed by axial dispersion and is controlled by changes of Peclet number. Simulation results reveal that when linear adsorption isotherm is used, the effect of axial dispersion on breakthrough curves of the system is important for Peclet numbers smaller than 50, whereas, for Langmuir isotherm axial dispersion is considerable for Peclet numbers less than 80. In addition, effects of type of adsorption isotherms and size of adsorbents on breakthrough curves are investigated, and results are compared with existing reports in the pertinent literature. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Ammonia removal from real wastewater using a LEWATIT S 108 H resin: A batch process and fixed-bed column

ABSTRACT

The ammonia component represents a sizable portion of pollutants in mining wastewater (MW) and because of its high selectivity toward ammonia, a LEWATIT resin was tested in the batch adsorption using different masses with 22.7 mg/L NH₃ ? N and in the continuous adsorption using two fixed-bed columns. Also, resin regeneration was achieved using diluted HCl. The results show the adsorption follows Freundlich isotherm in the batch study and was characterized by both the Bohart–Adams and Thomas models in the fixed-bed column. HCl can be used to regenerate LEWATIT with efficiency 40% and 70% for the small and large column, respectively.     

Adsorption of Th(IV) and U(VI) on functionalized SBA-15 mesoporous silica materials using fixed bed column method; breakthrough curves prediction and modeling

Removal–separation of Th(IV)/U(VI) by Schiff base functionalized SBA-15 materials SBA/SA and SBA/EnSA using fixed bed column method was investigated. The effects of flow rate and bed height were studied and the experimental breakthrough curves were obtained. The analysis of experimental data showed that the breakthrough time and exhaustion time, metal uptake capacity and total metal removal increased with reducing the flow rate, and with increasing the bed height. Thomas and Yan models were applied to the experimental data for evaluating the dynamic behavior and the characteristic parameters of the column for the process design.     

Cross-Flow Drying of Wheat: A Simulation Program with A Diffusion-Based Deep-Bed Model and A Kinetic Equation for Viability Loss Estimation

ABSTRACT

A mathematical model of heat and mass transfer for fixed beds was developed according to the modern theory of process simulation and standard laws of thermodynamics and transportphenomena. The mass transfer grain–air was predicted with simplified diffusional expressions together with an equation for the static equilibrium moisture content. Four differential equations were obtained for a grain layer and they were integrated along the bed depth and time with second     

Cross-Flow Drying of Wheat. A Simulation Program with a Diffusion-Based Deep-Bed Model and a Kinetic Equation for Viability Loss Estimations.

ABSTRACT

A mathematical model of heat and mass transfer for fixed beds was developed according to the modern theory of process simulation and standard laws of thermodynamics and transport phenomena. The mass transfer grain-air was predicted with simplified diffusional expressions together with an equation for the static equilibrium moisture content. Four differential equations were obtained for a grain layer and they were integrated along the bed depth and time with second and a fourth-order methods, respectively. The model was validated by comparing drying time predictions with experimental values, being the average error of 6%. The model was extended into a program for continuous cross-flow drying-cooling     

低阻高效同心环碟片填料旋转床流阻和传质特性研究

采用新型旋转床填料———同心环波纹碟片填料 ,对三种填料间距结构 ,在干、湿床两种状态下的气相压降随碟片填料间距、转速、气液流量的变化关系进行了试验研究 ,与有关文献的多孔介质填料压降结果对比 ,在相近的操作条件下 ,同心环波纹碟片填料的阻力分别是其阻力的 2 0 % (干床 )与 40 % (湿床 ) ,同心环波纹碟片填料的体积传质系数是它们的 1 9～ 2 5倍。