Date of Award
Master of Science
Endocrine disrupting chemicals (EDCs) are compounds considered pollutants of emerging concern. The United States Environmental Protection Agency (USEPA) defines emerging pollutants as new chemicals without regulatory status and with an impact on the environment and human health that is poorly understood. Bisphenol A (BPA) has been considered an EDC and found to be ubiquitous in the environment because of its presence in a multitude of products including food and beverage packaging, flame retardants, adhesives, building materials, electronic components, and paper coatings Currently, BPA is not regulated by the federal government in the US and waste water treatment plants are not designed nor required to remove it. As wastewater effluent for drinking water use becomes a reality in our society, it warrants a need to develop methods to effectively remove BPA from wastewater. This project proposed a novel sorption application in which we incorporated bentonite and activated carbon with the gelling properties of alginate to develop alginate gel-based (hydrogel) and dry beads to remove BPA. This adsorbent material has the potential to be a low cost and non-toxic alternative for the real world applications. Two types of materials were made, Alginate-Bentonite (AlgB) and Alginate-Activated carbon (AlgC) in this study. The objectives were to (1) study the removal of BPA by AlgB and AlgC under different conditions: sorbent dose (1.50mg/mL- 5.00mg/mL), temperatures (18oC- 40 oC) and pH (2.28-11.87); and (2) to test the removal ability on wastewater to analyze the matrix effect and the feasibility of real world use. Analysis of BPA was performed by Stir Bar Sorptive Extraction (SBSE) coupled with Thermal Desorption (TD) followed by Gas-Chromatography and Mass Spectrometry (GC/MS).
The AlgB beads were not able to effectively remove BPA from aqueous solutions when compared with AlgC beads. The percent removal of hydrogel AlgB was 43.37%, hydrogel AlgC was able to remove >99% (6-log removal) BPA when adding 4.50 g of AlgC in 20 mL of 10 ppm (mg L-1) BPA solution within 40 minutes. Dry AlgC was able to remove >99% (6-log removal) BPA when adding 1g of dry AlgC into 4 mL of 10 ppm (mg L-1) BPA solution within the first 3 hours. The maximum sorption capacity (qm) for dry AlgC beads was found to be 303.03 mg/g.
The removal sorption by AlgC followed a pseudo-second order model, proposing valence forces or electron exchange mechanisms. The isotherms for BPA removal by AlgC were in line to the Freundlich model (R2=0.9556), which suggests multilayer adsorption to a heterogenous adsorbent surface. The thermodynamic plots showed that the adsorption was exothermic and spontaneous.
The AlgC beads showed a removal of (67%) at the higher dose (5.00 mg/mL) under unadjusted conditions (pH 7-8) and a slightly higher removal under acidic conditions using the smaller dose (1.50 mg/mL). The impact of pH on the sorption of BPA by the AlgC beads were minimum with a difference of less than 3%, and that presents an advantage of the potential use AlgC in water treatment since the raw wastewater pH is around 7.
AlgC dry beads (1.50 mg/mL) was then used in raw wastewater samples to test the BPA removal and to investigate the matrix effect. In this case, the higher BPA removal achieved was 36.9% from spiked wastewater and 54.5% in spiked deionized water in a time lapse of 24 hours. These preliminary results show the ability of the AlgC beads to successfully remove BPA from aqueous solution, and the possibility of future real-world use. Further studies will focus the use of AlgC in the removal of other EDCs in drinking water and wastewater.
Received from ProQuest
Alma Lili Loya Posada
Loya Posada, Alma Lili, "Removal Of Endocrine Disrupting Compounds From Water And Wastewater Using Ecofriendly Materials" (2016). Open Access Theses & Dissertations. 683.