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Title: Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry

Abstract

To understand the nature of H{sub 2}S adsorption onto carbon surfaces under dry and anoxic conditions, the effects of carbon pore structure and surface chemistry were studied using activated carbon fibers (ACFs) with different pore structures and surface areas. Surface pretreatments, including oxidation and heat treatment, were conducted before adsorption/desorption tests in a fixed-bed reactor. Raw ACFs with higher surface area showed greater adsorption and retention of sulfur, and heat treatment further enhanced adsorption and retention of sulfur. The retained amount of hydrogen sulfide correlated well with the amount of basic functional groups on the carbon surface, while the desorbed amount reflected the effect of pore structure. Temperature-programmed desorption (TPD) and thermal gravimetric analysis (TGA) showed that the retained sulfurous compounds were strongly bonded to the carbon surface. In addition, surface chemistry of the sorbent might determine the predominant form of adsorbate on the surface. 38 refs., 7 figs., 3 tabs.

Authors:
; ; ;  [1]
  1. University of Pittsburgh, Pittsburgh, PA (United States). Department of Civil and Environmental Engineering
Publication Date:
OSTI Identifier:
20700939
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 39; Journal Issue: 24; Other Information: vidic@pitt.edu
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; HYDROGEN SULFIDES; ACTIVATED CARBON; CARBON FIBERS; PORE STRUCTURE; SURFACE PROPERTIES; SURFACE AREA; OXIDATION; SORPTIVE PROPERTIES; ADSORPTION; RETENTION; HEAT TREATMENTS

Citation Formats

Wenguo Feng, Seokjoon Kwon, Eric Borguet, and Radisav Vidic. Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry. United States: N. p., 2005. Web. doi:10.1021/es0507158.
Wenguo Feng, Seokjoon Kwon, Eric Borguet, & Radisav Vidic. Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry. United States. doi:10.1021/es0507158.
Wenguo Feng, Seokjoon Kwon, Eric Borguet, and Radisav Vidic. Thu . "Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry". United States. doi:10.1021/es0507158.
@article{osti_20700939,
title = {Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry},
author = {Wenguo Feng and Seokjoon Kwon and Eric Borguet and Radisav Vidic},
abstractNote = {To understand the nature of H{sub 2}S adsorption onto carbon surfaces under dry and anoxic conditions, the effects of carbon pore structure and surface chemistry were studied using activated carbon fibers (ACFs) with different pore structures and surface areas. Surface pretreatments, including oxidation and heat treatment, were conducted before adsorption/desorption tests in a fixed-bed reactor. Raw ACFs with higher surface area showed greater adsorption and retention of sulfur, and heat treatment further enhanced adsorption and retention of sulfur. The retained amount of hydrogen sulfide correlated well with the amount of basic functional groups on the carbon surface, while the desorbed amount reflected the effect of pore structure. Temperature-programmed desorption (TPD) and thermal gravimetric analysis (TGA) showed that the retained sulfurous compounds were strongly bonded to the carbon surface. In addition, surface chemistry of the sorbent might determine the predominant form of adsorbate on the surface. 38 refs., 7 figs., 3 tabs.},
doi = {10.1021/es0507158},
journal = {Environmental Science and Technology},
number = 24,
volume = 39,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}
  • Activated carbon fibers (ACFs) were oxidized using both aqueous and nonaqueous treatments. As much as 29 wt% oxygen can be incorporated onto the pore surface in the form of phenolic hydroxyl, quinine, and carboxylic acid groups. The effect of oxidation on the pore size, pore volume, and the pore surface chemistry was thoroughly examined. The average micropore size is typically affected very little by aqueous oxidation while the micropore volume and surface area decreases with such a treatment. In contrast, the micropore size and micropore volume both increase with oxidation in air. Oxidation of the fibers produces surface chemistries inmore » the pore that provide for enhanced adsorption of basic (ammonia) and polar (acetone) molecules at ambient and nonambient temperatures. The adsorption capacity of the oxidized fibers for acetone is modestly better than the untreated ACFs while the adsorption capacity for ammonia can increase up to 30 times compared to untreated ACFs. The pore surface chemical makeup was analyzed using elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS).« less
  • Three wood-based commercial activated carbons supplied by Westvaco were studied as adsorbents of hydrogen sulfide. The initial materials were characterized using sorption of nitrogen, Boehm titration, potentiometric titration, water sorption, thermal analysis, and temperature-programmed desorption. The breakthrough tests were done at low concentrations of H{sub 2}S in the input gas to simulate conditions in water pollution control plants where carbon beds are used as odor adsorbents. In spite of apparent general similarities in the origin of the materials, method of activation, surface chemistry, and porosity, significant differences in their performance as hydrogen sulfide adsorbents were observed. Results show that themore » combined effect of the presence of pores large enough to accommodate surface functional groups and small enough to have the film of water at relatively low pressure contributes to oxidation of hydrogen sulfide. Moreover, there are features of activated carbon surfaces such as local environment of acidic/basic groups along with the presence of alkali metals which are important to the oxidation process.« less
  • Activated carbon fibers (ACF) were used to adsorb ppmv concentrations of volatile organic compounds (VOCs) from laboratory generated gas streams. VOCs considered were benzene and acetone because the VOCs are commonly found in indoor air and have potential to increase health risks to humans. ACF were used as the adsorbent because they typically exhibit higher adsorption capacities and faster adsorption kinetics than commercially available granular activated carbons (GAC) and show potential as an adsorbent to effectively remove VOCs from indoor air. Adsorption models by Dubinin and coworkers (Dubinin, 1975), based on the theory of volume filling of micropores, and anmore » empirical model by Freudlich were used to fit the measured adsorption isotherms. Agreement between the modeled and experimental results for acetone and benzene using the Dubinin-Radushkevich equation generally improved with increasing BET surface area and produced reasonable fits of the adsorption isotherms for both acetone and benzene. The Freundlich equation produced values for correlation coefficients (R) between modeled and experimental data from -.980 to 0.997, indicating the validity of using the Freundlich equation to model the adsorption isotherms over the concentration range of interest. These results indicate that ACF show potential as an adsorbent for removing low concentrations of VOCs from indoor air. 14 refs., 5 figs., 4 tabs.« less
  • Phenolic compounds exist widely in the industrial effluents such as those from oil refineries and the coal tar, plastics, leather, paint, pharmaceutical, and steel industries. Since they are highly toxic and are, in general, not amenable to biological degradation, methods of treatment are continuously being modified and developed. Liquid-phase adsorption equilibria of eight phenolic compounds onto activated carbon fibers were measured in the concentration range 40--500 g/m{sup 3} at 303 K. High adsorption capacities were observed for the chlorinated phenols compared to the methyl-substituted phenols. Several two- and three-parameter isotherm equations were tested. Among the equations tried, the three-parameter equationmore » of Jossens et al. based on a heterogeneous surface adsorption theory was found to be the most satisfactory over the entire range of concentration. The widely used two-parameter equations of Langmuir and Freundlich were not applicable to the present adsorption systems.« less
  • The tailoring of the pore surface chemistry of activated carbon fibers is shown to be an effective method for increasing the removal efficiencies of various contaminants under a fixed bed configuration. An oxidation treatment with nitric and sulfuric acids results in a significant increase in the adsorption capacities and breakthrough times. The adsorption kinetics were described by a homogeneous surface diffusion model. Although the effective diffusion coefficients were actually reduced by the oxidation process, the improvement in equilibrium adsorption capacities more than compensated, to result in the overall improved breakthrough times.