Coagulation treatment to remove denatonium benzoate from water

Date of Award

2017

Degree Name

M.S. in Chemical Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Kenya Crosson

Abstract

The bittering agent denatonium benzoate, DB, was mandated by the U.S. House of Representatives (H.R. 615) to be added to antifreeze containing more than 10% ethylene glycol at 30-50ppm in order to prevent accidental poisoning. 30-ppm DB concentration in water makes it unpalatable. This research addressed the optimal doses of alum and ferric chloride, and impact of water quality conditions such as pH, ionic strength, turbidity, and alkalinity on DB removal from water. Coagulation aids such as kaolin and bentonite were studied for their impact on DB removal. After conducting several coagulation experiments on water sources at their initial ionic strength (0.01-M river and groundwater; 0.00005-M ultrapure water), it was found that 20-ppm alum was the optimal dose that removed 90% DB from ultrapure water. Higher alum dosages (60-mg/l) were needed to achieve 76% DB removal from groundwater. A 50-ppm dose of alum or FeCl3 achieved 72% DB removal from river water. In comparison to alum coagulation in ultrapure water, a lower FeCl3 dose (5-ppm) achieved a similar DB removal (83%). However, in groundwater, FeCl3 treatment did not achieve better DB removal (49%) than alum. Both coagulants consumed part of water alkalinity. Higher doses (50-ppm of alum or FeCl3) were required to remove DB from river water than ultrapure water (5-ppm ferric chloride or 20-ppm alum) because river water had higher turbidity, which indicates that higher coagulant doses tended to remove DB as well as the particles causing turbidity in river water. Coagulants lowered river water turbidity to 0.1 NTU; FeCl3 (20-ppm) was more effective than alum to lower turbidity to 0.1 NTU in groundwater. Optimal pH conditions for alum or FeCl3 were 5.8, 6, and 7.45 in ultrapure water, river water, and groundwater, respectively. In ultrapure water, pH conditions higher than 5.8 resulted in lower DB removal, and below pH 5.8, DB removal also decreased. An ionic strength of 0.00005 M and 0.01 M in ultrapure water and river water, respectively, achieved the best DB removal with alum. Ionic strength of 0.00005 M and 0.03 M in ultrapure water and river water, respectively, achieved the best DB removal by FeCl3. Addition of kaolin and bentonite did not achieve higher DB removal. Coagulant aid and river water results suggest that the presence of specific clay minerals and turbidity in the water limit DB removal. Lower DB removal was obtained when the water turbidity was higher, and only increased ionic strength conditions that would reduce the electric double layer thickness and facilitates the destabilization of clay minerals and turbidity slightly enhanced DB removal. The coagulant aid experiments support this premise that DB likely does not adsorb to these clay minerals to be removed via coagulation.

Keywords

Water Purification Coagulation, Ferric chloride, Aluminum sulfate, Chemical Engineering, Chemistry, Engineering, Environmental Engineering, Coagulation, Denatonium Benzoate, Aluminum Sulfate, Ferric Chloride

Rights Statement

Copyright © 2017, author

Link to Full Text

Share

COinS