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Title: Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse

Abstract

Arsenic (As) and Selenium (Se) are found in water in the form of oxyanions. Relatively high concentrations of As and Se have been reported both in power plant discharges, as well as, in fresh water supplies. The International Agency for Research on Cancer currently classifies As as a group 1 chemical, that is considered to be carcinogenic to humans. In Phase I of this project we studied the adsorption of As and Se by uncalcined and calcined layered double hydroxide (LDH). The focus of the present work is a systematic study of the adsorption of As and Se by conditioned LDH adsorbents. Conditioning the adsorbent significantly reduced the Mg and Al dissolution observed with uncalcined and calcined LDH. The adsorption rates and isotherms have been investigated in batch experiments using particles of four different particle size ranges. As(V) adsorption is shown to follow a Sips-type adsorption isotherm. The As(V) adsorption rate on conditioned LDH increases with decreasing adsorbent particle size; the adsorption capacity, on the other hand, is independent of the particle size. A homogeneous surface diffusion model (HSDM) and a bi-disperse pore model (BPM) - the latter viewing the LDH particles as assemblages of microparticles and taking into accountmore » bulk diffusion in the intraparticle pore space, and surface diffusion within the microparticles themselves - were used to fit the experimental kinetic data. The HSDM estimated diffusivity values dependent on the particle size, whereas the BPM predicted an intracrystalline diffusivity, which is fairly invariant with particle size. The removal of As(V) on conditioned LDH adsorbents was also investigated in flow columns, where the impact of important solution and operational parameters such as influent As concentration, pH, sorbent particle size and flow rate were studied. An early breakthrough and saturation was observed at higher flow rates and at higher influent concentrations, whereas a decrease in the sorbent particle size and a decrease in influent pH resulted in an increase in the bed volumes treated at breakthrough. Both the HSDM and BPM were shown capable of predicting the column behavior.« less

Authors:
;
Publication Date:
Research Org.:
University Of Southern California Incorporated
Sponsoring Org.:
USDOE
OSTI Identifier:
982996
DOE Contract Number:  
FG26-06NT42711
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
20 FOSSIL-FUELED POWER PLANTS; 54 ENVIRONMENTAL SCIENCES; ADSORBENTS; CLAYS; ADSORPTION; ADSORPTION ISOTHERMS; ARSENIC; KINETICS; PARTICLE SIZE; POWER PLANTS; REMOVAL; SELENIUM; WASTE WATER; WATER TREATMENT

Citation Formats

Sahimi, Muhammad, and Tsotsis, Theodore. Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse. United States: N. p., 2010. Web. doi:10.2172/982996.
Sahimi, Muhammad, & Tsotsis, Theodore. Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse. United States. https://doi.org/10.2172/982996
Sahimi, Muhammad, and Tsotsis, Theodore. 2010. "Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse". United States. https://doi.org/10.2172/982996. https://www.osti.gov/servlets/purl/982996.
@article{osti_982996,
title = {Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse},
author = {Sahimi, Muhammad and Tsotsis, Theodore},
abstractNote = {Arsenic (As) and Selenium (Se) are found in water in the form of oxyanions. Relatively high concentrations of As and Se have been reported both in power plant discharges, as well as, in fresh water supplies. The International Agency for Research on Cancer currently classifies As as a group 1 chemical, that is considered to be carcinogenic to humans. In Phase I of this project we studied the adsorption of As and Se by uncalcined and calcined layered double hydroxide (LDH). The focus of the present work is a systematic study of the adsorption of As and Se by conditioned LDH adsorbents. Conditioning the adsorbent significantly reduced the Mg and Al dissolution observed with uncalcined and calcined LDH. The adsorption rates and isotherms have been investigated in batch experiments using particles of four different particle size ranges. As(V) adsorption is shown to follow a Sips-type adsorption isotherm. The As(V) adsorption rate on conditioned LDH increases with decreasing adsorbent particle size; the adsorption capacity, on the other hand, is independent of the particle size. A homogeneous surface diffusion model (HSDM) and a bi-disperse pore model (BPM) - the latter viewing the LDH particles as assemblages of microparticles and taking into account bulk diffusion in the intraparticle pore space, and surface diffusion within the microparticles themselves - were used to fit the experimental kinetic data. The HSDM estimated diffusivity values dependent on the particle size, whereas the BPM predicted an intracrystalline diffusivity, which is fairly invariant with particle size. The removal of As(V) on conditioned LDH adsorbents was also investigated in flow columns, where the impact of important solution and operational parameters such as influent As concentration, pH, sorbent particle size and flow rate were studied. An early breakthrough and saturation was observed at higher flow rates and at higher influent concentrations, whereas a decrease in the sorbent particle size and a decrease in influent pH resulted in an increase in the bed volumes treated at breakthrough. Both the HSDM and BPM were shown capable of predicting the column behavior.},
doi = {10.2172/982996},
url = {https://www.osti.gov/biblio/982996}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 08 00:00:00 EST 2010},
month = {Fri Jan 08 00:00:00 EST 2010}
}