Date of Award
Chemistry and Biochemistry
Adsorbent, Hydrogel, Mitigation, Phosphorous, Remediation, Sawdust
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This dissertation outlines the creation of many phosphate sorbent materials with varying capacities and affinities towards phosphate. Some materials, such as plant roots, are highly effective in concentrated phosphate solutions while hydrogels are more effective at low concentrations. Each chapter focuses on a specific material, the method by which it is produced or prepared, and its effectiveness as a phosphate sorbent material.
Chapter 2 describes the use of unmodified tomato plant roots as phosphate sorbing materials. These roots were found to have a high phosphate binding capacity and higher affinity than materials studied previously in our lab. Application of the roots to a manure contaminated waste stream resulted in a 71 % reduction in effluent phosphate concentrations. Further, a method of phosphate desorption using dilute carboxymethyl cellulose is described that allows efficient recovery of phosphate and reuse of the roots as sorbent materials. The carboxymethyl cellulose enhances the precipitation of phosphate as calcium-phosphate.
Chapter 3 describes the chemical modification of sawdust to confer phosphate sorption capacity. Two approaches: direct and indirect were studied alongside many different ligands attached through epichlorohydrin linkages. These materials were cationized with iron and used to remove phosphate from water. The most successful synthetic approach was the direct modification of the sawdust surface. The most successful ligand studied was ethylenediamine added in an aqueous synthesis. The binding capacity, affinity, and resistance to competing anion-induced reductions in capacity are superior to previously studied materials.
Chapter 4 describes the direct modification of sawdust using a Williamson etherification. The reaction is optimized to produce solid carboxymethyl sawdust that readily chelates iron conferring phosphate sorption capacity. The optimized material was characterized and the phosphate-binding characteristics including capacity, affinity, and resistance to counter anions studied. Further studies measured the efficacy of the material in a variable flow rate system with increasing retention times yielding higher percentage removals.
Chapter 5 describe the creation of a carboxymethyl cellulose hydrogel crosslinked with iron used to remove phosphate from water. The hydrogel is studied for its capacity, affinity, and resistance to counter anions. Further, its stability in various media is studied. Chapter 6 describes the design, construction, and operation of a manufacturing system for the industrial-scale synthesis of the hydrogel described in chapter 5. It details the challenges encountered and successfully applied solutions.
Chapter 7 extends the hydrogel work detailed in chapter 5 in a comparative analysis of hydrogel composites. Hydrogel composites are created using alginate and carboxymethyl cellulose. These composites are crosslinked using aluminum, calcium, copper, iron, and lanthanum cations. This is followed by the creation of bimetallic composites. The most promising bimetallic composites are studied for their capacity, affinity, and resistance to counter anions. Analysis of the material stability, reusability, and performance in a continuously flowing system is performed.
Ure, David, "The Valorization of Agricultural by Products for the Removal of Inorganic Phosphate from Water" (2021). Electronic Theses and Dissertations. 8890.