Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH)

Mohammad Badruzzaman; Paul Westerhoff; Detlef R U Knappe

doi:10.1016/j.watres.2004.07.007

Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH)

Mohammad Badruzzaman, Paul Westerhoff, Detlef R U Knappe

Civil and Environmental Engineering

Research output: Contribution to journal › Article › peer-review

339 Scopus citations

Abstract

Porous iron oxides are being evaluated and selected for arsenic removal in potable water systems. Granular ferric hydroxide, a typical porous iron adsorbent, is commercially available and frequently considered in evaluation of arsenic removal methods. GFH is a highly porous (micropore volume ∼0.0394±0.0056 cm³ g^-1, mesopore volume ∼0.0995±0.0096 cm³g^-1) adsorbent with a BET surface area of 235±8 m²g^-1. The purpose of this paper is to quantify arsenate adsorption kinetics on GFH and to determine if intraparticle diffusion is a rate-limiting step for arsenic removal in packed-bed treatment systems. Data from bottle-point isotherm and differential column batch reactor (DCBR) experiments were used to estimate Freundlich isotherm parameters (K and 1/n) as well as kinetic parameters describing mass transfer resistances due to film diffusion (k_f) and intraparticle surface diffusion (D_s). The pseudo-equilibrium (18 days of contact time) arsenate adsorption density at pH 7 was 8 μg As/mg dry GFH at a liquid phase arsenate concentration of 10 μg As/L. The homogeneous surface diffusion model (HSDM) was used to describe the DCBR data. A non-linear relationship (D_S=3.0^-9 x R_p ^1.4) was observed between D_s and GFH particle radius (R_P) with D_s> values ranging from 2.98 x 10^-12 cm² s^-1 for the smallest GFH mesh size (100 x 140) to 64 x 10^-11 cm² s^-1 for the largest GFH mesh size (10 x 30). The rate-limiting process of intraparticle surface diffusion for arsenate adsorption by porous iron oxides appears analogous to organic compound adsorption by activated carbon despite differences in adsorption mechanisms (inner-sphere complexes for As versus hydrophobic interactions for organic contaminants). The findings are discussed in the context of intraparticle surface diffusion affecting packed-bed treatment system design and application of rapid small-scale column tests (RSSCTs) to simulate the performance of pilot- or full-scale systems at the bench-scale.

Original language	English (US)
Pages (from-to)	4002-4012
Number of pages	11
Journal	Water Research
Volume	38
Issue number	18
DOIs	https://doi.org/10.1016/j.watres.2004.07.007
State	Published - 2004

Keywords

Adsorption
Arsenic
Iron
Surface diffusion
Water treatment

ASJC Scopus subject areas

Water Science and Technology
Ecological Modeling
Pollution
Waste Management and Disposal
Environmental Engineering
Civil and Structural Engineering

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10.1016/j.watres.2004.07.007

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@article{44a885057d1143429d972eb5367da359,

title = "Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH)",

abstract = "Porous iron oxides are being evaluated and selected for arsenic removal in potable water systems. Granular ferric hydroxide, a typical porous iron adsorbent, is commercially available and frequently considered in evaluation of arsenic removal methods. GFH is a highly porous (micropore volume ∼0.0394±0.0056 cm3 g-1, mesopore volume ∼0.0995±0.0096 cm3g-1) adsorbent with a BET surface area of 235±8 m2g-1. The purpose of this paper is to quantify arsenate adsorption kinetics on GFH and to determine if intraparticle diffusion is a rate-limiting step for arsenic removal in packed-bed treatment systems. Data from bottle-point isotherm and differential column batch reactor (DCBR) experiments were used to estimate Freundlich isotherm parameters (K and 1/n) as well as kinetic parameters describing mass transfer resistances due to film diffusion (kf) and intraparticle surface diffusion (Ds). The pseudo-equilibrium (18 days of contact time) arsenate adsorption density at pH 7 was 8 μg As/mg dry GFH at a liquid phase arsenate concentration of 10 μg As/L. The homogeneous surface diffusion model (HSDM) was used to describe the DCBR data. A non-linear relationship (DS=3.0-9 x Rp 1.4) was observed between Ds and GFH particle radius (RP) with Ds> values ranging from 2.98 x 10-12 cm2 s-1 for the smallest GFH mesh size (100 x 140) to 64 x 10-11 cm2 s-1 for the largest GFH mesh size (10 x 30). The rate-limiting process of intraparticle surface diffusion for arsenate adsorption by porous iron oxides appears analogous to organic compound adsorption by activated carbon despite differences in adsorption mechanisms (inner-sphere complexes for As versus hydrophobic interactions for organic contaminants). The findings are discussed in the context of intraparticle surface diffusion affecting packed-bed treatment system design and application of rapid small-scale column tests (RSSCTs) to simulate the performance of pilot- or full-scale systems at the bench-scale.",

keywords = "Adsorption, Arsenic, Iron, Surface diffusion, Water treatment",

author = "Mohammad Badruzzaman and Paul Westerhoff and Knappe, {Detlef R U}",

note = "Funding Information: Financial support for this work was provided by the National Science Foundation Water Quality Center at Arizona State University. Help from Sanjay Reddy (DSWA Inc., USA) is acknowledged. Input was received from Prof. Dr.-Ing. Martin Jekel (Technical University Berlin, Germany) and Dr.-Ing. Wolfgang Driehaus (GEH Wasserchemie GmbH & Co. KG, Osnabrueck, Germany). Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of supporting organizations. ",

year = "2004",

doi = "10.1016/j.watres.2004.07.007",

language = "English (US)",

volume = "38",

pages = "4002--4012",

journal = "Water Research",

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T1 - Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH)

AU - Badruzzaman, Mohammad

AU - Westerhoff, Paul

AU - Knappe, Detlef R U

N1 - Funding Information: Financial support for this work was provided by the National Science Foundation Water Quality Center at Arizona State University. Help from Sanjay Reddy (DSWA Inc., USA) is acknowledged. Input was received from Prof. Dr.-Ing. Martin Jekel (Technical University Berlin, Germany) and Dr.-Ing. Wolfgang Driehaus (GEH Wasserchemie GmbH & Co. KG, Osnabrueck, Germany). Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of supporting organizations.

PY - 2004

Y1 - 2004

N2 - Porous iron oxides are being evaluated and selected for arsenic removal in potable water systems. Granular ferric hydroxide, a typical porous iron adsorbent, is commercially available and frequently considered in evaluation of arsenic removal methods. GFH is a highly porous (micropore volume ∼0.0394±0.0056 cm3 g-1, mesopore volume ∼0.0995±0.0096 cm3g-1) adsorbent with a BET surface area of 235±8 m2g-1. The purpose of this paper is to quantify arsenate adsorption kinetics on GFH and to determine if intraparticle diffusion is a rate-limiting step for arsenic removal in packed-bed treatment systems. Data from bottle-point isotherm and differential column batch reactor (DCBR) experiments were used to estimate Freundlich isotherm parameters (K and 1/n) as well as kinetic parameters describing mass transfer resistances due to film diffusion (kf) and intraparticle surface diffusion (Ds). The pseudo-equilibrium (18 days of contact time) arsenate adsorption density at pH 7 was 8 μg As/mg dry GFH at a liquid phase arsenate concentration of 10 μg As/L. The homogeneous surface diffusion model (HSDM) was used to describe the DCBR data. A non-linear relationship (DS=3.0-9 x Rp 1.4) was observed between Ds and GFH particle radius (RP) with Ds> values ranging from 2.98 x 10-12 cm2 s-1 for the smallest GFH mesh size (100 x 140) to 64 x 10-11 cm2 s-1 for the largest GFH mesh size (10 x 30). The rate-limiting process of intraparticle surface diffusion for arsenate adsorption by porous iron oxides appears analogous to organic compound adsorption by activated carbon despite differences in adsorption mechanisms (inner-sphere complexes for As versus hydrophobic interactions for organic contaminants). The findings are discussed in the context of intraparticle surface diffusion affecting packed-bed treatment system design and application of rapid small-scale column tests (RSSCTs) to simulate the performance of pilot- or full-scale systems at the bench-scale.

AB - Porous iron oxides are being evaluated and selected for arsenic removal in potable water systems. Granular ferric hydroxide, a typical porous iron adsorbent, is commercially available and frequently considered in evaluation of arsenic removal methods. GFH is a highly porous (micropore volume ∼0.0394±0.0056 cm3 g-1, mesopore volume ∼0.0995±0.0096 cm3g-1) adsorbent with a BET surface area of 235±8 m2g-1. The purpose of this paper is to quantify arsenate adsorption kinetics on GFH and to determine if intraparticle diffusion is a rate-limiting step for arsenic removal in packed-bed treatment systems. Data from bottle-point isotherm and differential column batch reactor (DCBR) experiments were used to estimate Freundlich isotherm parameters (K and 1/n) as well as kinetic parameters describing mass transfer resistances due to film diffusion (kf) and intraparticle surface diffusion (Ds). The pseudo-equilibrium (18 days of contact time) arsenate adsorption density at pH 7 was 8 μg As/mg dry GFH at a liquid phase arsenate concentration of 10 μg As/L. The homogeneous surface diffusion model (HSDM) was used to describe the DCBR data. A non-linear relationship (DS=3.0-9 x Rp 1.4) was observed between Ds and GFH particle radius (RP) with Ds> values ranging from 2.98 x 10-12 cm2 s-1 for the smallest GFH mesh size (100 x 140) to 64 x 10-11 cm2 s-1 for the largest GFH mesh size (10 x 30). The rate-limiting process of intraparticle surface diffusion for arsenate adsorption by porous iron oxides appears analogous to organic compound adsorption by activated carbon despite differences in adsorption mechanisms (inner-sphere complexes for As versus hydrophobic interactions for organic contaminants). The findings are discussed in the context of intraparticle surface diffusion affecting packed-bed treatment system design and application of rapid small-scale column tests (RSSCTs) to simulate the performance of pilot- or full-scale systems at the bench-scale.

KW - Adsorption

KW - Arsenic

KW - Iron

KW - Surface diffusion

KW - Water treatment

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Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH)

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