Surface chemistry design and characterization of anion exchange and activated carbon fibers for critical contaminants removal

Zheng, Weihua

Permalink

https://hdl.handle.net/2142/49807 Copy

Description

Title

Surface chemistry design and characterization of anion exchange and activated carbon fibers for critical contaminants removal

Author(s)

Zheng, Weihua

Issue Date

2014-05-30T17:18:43Z

Director of Research (if dissertation) or Advisor (if thesis)

Economy, James

Doctoral Committee Chair(s)

Economy, James

Committee Member(s)

• Braun, Paul V.
• Cheng, Jianjun
• Shang, Jian Ku

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Ammonia Removal
• Perchlorate Removal
• Hexavalent Chromium Removal
• anion exchangable activated carbon
• chemically activated carbon fiber
• ion exchange fiber
• activated carbon fiber composites
• Boehm titration

Abstract

This thesis is devoted to the design and characterization of surface chemistry of materials based on a novel fibrous platform for rapid and selective removal of trace contaminants. The first project is to study activated carbon fiber composites (ACFCs) for removal of NH3 from air. Three series of materials were synthesized and modified, namely Polyvinyl alcohol (PVA) based Chemically Activated Carbon Fibers (CAFs) with optimized activation temperatures, Kynol based Activated Carbon Fibers (ACFs) and Phenolic based (CAFs) with post-treatment by nitric acid. NH3 adsorption performance was measured in flowthrough configuration at both 0% and 50% relative humidity conditions. The surface of these materials was characterized using SEM, BET, elemental analysis, FTIR, XPS, and Boehm titration. High surface area >1000 m2/g of all ACFCs are essential to providing more accessible surface functional groups and thus adsorption efficiency. Surface chemistry analysis results showed that adsorption performance is correlated with surface acidic oxygen groups. As a result, combined with high adsorption capacity and good regenerative efficiency, PVA-CAFs provide as an effective solution for NH3 removal in air. The second project is to explore the path to design a porous carbon with anion-exchangeable functional groups, and apply such system towards Cr(VI) removal in drinking water. A novel hybrid anion exchangeable activated carbons (HACAX) is synthesized through chemical modification of porous carbon surface. Ion exchange capacity, kinetics and regeneration tests suggest that HACAX contains stable positive charged functional groups. The surface characterization results suggest HACAX not only contains stable positive charged functional groups, but also a broad spectrum of surface oxygen functional groups. In the study of adsorption of hexavalent chromium, HACAX shows excellent kinetics, selectivity and regeneration efficiency towards Cr (VI). Combined with rich surface oxygen functional groups, this material provides a pathway to adsorb and convert Cr(VI) into Cr(III) at natural pH. The results suggest HACAX could potentially provide an effective point-of-use (POU) solution for hexavalent chromium removal from drinking water. The third project is to study ion exchange fiber composites (IXFCs) for perchlorate removal from drinking water. In order to improve selectivity and kinetics, different trialkylamines and combinations of them have been employed to modify the surface chemistry of IXFCs, and roles of short chain and long chain trialkylamine on improving selectivity and kinetics have been studied and discussed. The optimized bi-functional system with trihexylamine + triethylamine (THA/TEA) showed one of the highest selectivity with improved kinetics. In a field test, addition of THA/TEA IXFCs proves to be an excellent solution which could process 200 L of 150 ppb ClO4- contaminated tap water before breaking through 1 ppb.

Graduation Semester

2014-05

Permalink

http://hdl.handle.net/2142/49807

Copyright and License Information

Copyright 2014 Weihua Zheng

Owning Collections