On the Nature, Remediation, and Quantification of Radium in Hydraulic Fracturing Co-products
Open Access
- Author:
- Ajemigbitse, Moses Ayo
- Graduate Program:
- Environmental Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 14, 2019
- Committee Members:
- Fred Scott Cannon, Dissertation Advisor/Co-Advisor
Nathaniel Richard Warner, Committee Chair/Co-Chair
Li Li, Committee Member
Fred Scott Cannon, Committee Member
Sridhar Komarneni, Outside Member - Keywords:
- Hydraulic fracturing
Marcellus shale
Radium
Produced Water
Solids
Accuracy - Abstract:
- Since its discovery by Marie and Pierre Curie in 1898, radium enjoyed a notorious celebrity throughout the 19th and 20th century. In the natural environment, radium is confined to exist in Uranium and Thorium bearing ores, deep within the earth’s crust. The practice of hydraulic fracturing for natural gas production provides a pathway for surface release from subsurface geologic reservoirs via liquid and solid co-products. The extensive application of this technology has led to large volumes of radium-bearing fluids and solid material, requiring specialized handling and management. In this work, the nature, remediation, and quantification of radium in these co-products are considered. In the first part of this dissertation, I address the distribution of radium in the solid and liquid co-products and speculate on novel treatment techniques that address the management of these radium-bearing materials with the goal of environmental sustainability. For the solid material, I evaluate a novel hydroacoustic cavitation system for separating the particle sizes and its effect on radium distribution. This hydroacoustic cavitation system enables the reclamation of marketable sand from the residual solid wastes worth $50,000 - $70,000/year when sold at a fraction of the price of freshly mined silica sand. This reclaimed sand, along with re-claimable clay, could reduce waste volumes by 50%, which represents a yearly savings of $200,000 for facilities handling ~5,000 tons/year of residual solid waste. Additionally, treatment by hydroacoustic cavitation results in radium being concentrated in the finest particle sizes, presenting a new option for radioactivity management. Reclamation could result in the reduction of radioactivity disposed of in landfills, mitigating the risk of radioactive exposure and contamination. For the liquid material, I investigate the novel application of a synthetic clay with high Ra selectivity and high charge for radium removal. This synthetic clay, Na-4-mica, presents itself as an ideal candidate for radium removal as its interlayer can collapse upon complete substitution, hence sequestering radium and mitigating release and environmental exposure. Na-4-mica can remove radium at every pH, and at high salinities, however, Ba, presents a significant competition for absorption sites. Radium removal from real produced water samples by Na-4-mica re-quires pre-treatment to reduce the exchange competition of Ca, Mg, and Sr as their activities in the high total dissolved solids concentrations of produced waters over-whelm Ra’s. The second part of this dissertation addresses the quantification of radium in these co-products. More specifically, the nature of the radium-bearing media is considered. In the case of the solid materials, I probe the effect of sample density and volume on radium measurements; and with regard to the liquids, I probe the effect of the high salinity environment on radium measurements by gamma spectroscopy. I then suggest empirical methods to increase the accuracy of these measurements. Radium measurements of the solids can be inaccurate by up to ~50% when sample density and volume are ignored. The total dissolved solids concentrations of the liquids, as well as its composition, greatly influences radium measurements, and radium activities can be underestimated by up to 40% when they are not taken into account. Rapid and accurate measurements of radium in the solids and liquids can be achieved by performing direct analysis of radium at 186 keV following interference correction and by accounting for sample density and volume – in the case of the solids, or total dissolved solids concentration and composition – in the case of the liquids. Finally, I describe a novel approach to rapid measurement performed by liquid scintillation counting by applying alpha/beta discrimination and spectrum deconvolution. This method utilizes a simple evaporative and acid-dissolution sample preparation protocol that is effective at removing the spectra interference of radium's daughters when combined with alpha/beta discrimination. The radium recovery of this sample preparation protocol is >90%. This novel method produces radium measurements with an R2 of 0.92 when compared to high-accuracy gamma spectroscopy. The reduced sample preparation steps, low cost, and rapid analysis (four-hour evaporation and one hour counting time) present this as a method ideal for rapid field appraisal prior to comprehensive radiochemical analysis