Sol-gel synthesis of organo-ceramic hybrids and characterization for metal ion separations from aqueous streams
Date of Award
Doctor of Philosophy (PhD)
Biomedical and Chemical Engineering
Lawrence L. Tavlarides
Sol-gel, Organoceramic, Metal ion separations, Aqueous streams
Chemical Engineering | Engineering | Materials Science and Engineering
Novel organo-ceramic composite materials prepared in our laboratory by sol-gel processing are proposed as adsorbents for metal separations in wastewater treatment processes and hydrometallurgical processes. Normally, organo-ceramic adsorbents are developed either by solvent deposition or by covalent ligand attachment techniques. These conventional ceramic-supported adsorbents have good mechanical, chemical, and thermal strengths and well-defined pore characteristics, but their applications are limited due to their low metal uptake capacities. This limitation is overcome in this study by the direct incorporation of the functionality into the composite matrix through the reaction of two silane compounds as the precursors of the ceramic skeleton and functionality carrier.
Three organo-ceramic composite materials functionalized with thiol (SOL-AD) imidazole (SOL-IPS), and pyrazole (SOL-PzPs) moieties are synthesized and characterized for their applications. Various synthesis parameters are considered and controlled to produce these adsorbents at optimal conditions. SOL-AD adsorbents are developed for the extraction of cadmium and mercury ions from wastewater streams. SOL-AD-IV, specifically, has maximum uptake capacities of 220 mg/gm of cadmium and 1280 mg/gm of mercury. This adsorbent is being further studied for removal of mercury from scrubber solutions generated from coal-fired power plants. SOL-IPS and SOL-PzPs adsorbents are developed to selectively extract palladium(II), platinum(IV), and gold(III) chlorides from other transition metal ions in hydrochloric acid solutions. SOL-IPS-F-22 synthesized at the optimal conditions has 1.54, 1.41, and 2.43 mmol/gm of maximum uptake capacities at 0.1 M HCl concentration for Pd(II), Pt(IV), and Au(III) chlorides, respectively. SOL-PzPs-BD-5 synthesized at the optimal conditions has 1.41, 0.55, and 1.76 mmol/gm of uptake capacities at 2.0 M HCl solutions for Pd(II), Pt(IV), and Au(III) chlorides, respectively. SOL-IPS-F-22 and SOL-PzPs-BD-5 have no reactivity for copper and iron ions, which primarily exist in noble metal leaching solutions. In addition, SOL-PzPs-BD-5 has strong selectivity for Pd(II), chloride over Pt(IV) and Au(III) chlorides. Hence, palladium can selectively be extracted from the mixture solutions of these metal ions by a column operation.
In addition to such desirable properties, these adsorbents maintain high physico-chemical stability during repeated uses. Hence, the potential of sol-gel processing for the synthesis of high performance organo-ceramic adsorbents is demonstrated in this study.
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Lee, Jun-Sig, "Sol-gel synthesis of organo-ceramic hybrids and characterization for metal ion separations from aqueous streams" (2001). Biomedical and Chemical Engineering - Dissertations. 26.