(169a) Removing Naturally Occurring Radioactive Materials (NORMs) from Produced Waters of Oil & Natural Gas Industries: From Camd to Experimental Proof-of-Concept

CAMD is the reverse use of the group contribution method to generate molecules with desirable properties. The group contribution method (GCM) is a technique to estimate and predict thermodynamics and other properties from molecular structures. This approach dramatically reduces the amount of data needed. Instead of requiring information on thousands or millions of components' properties, data for only a few dozen or a few hundred groups are needed. A GCM uses the principle that some simple chemical components' structures are always the same in many different molecules. The smallest common constituents are the atoms and the bonds. For example, all-organic components are built of carbon, hydrogen, oxygen, nitrogen, halogens, and sometimes sulfur. Together with single, double, and triple bonds, only ten atom types and three bond types are necessary to build thousands of components. The next slightly more complex building blocks of components are functional groups, which are themselves built from a few atoms and bonds. The problem is a combinatorial optimization problem, which is a difficult optimization problem. We present a new optimization framework to solve real-world problems of CAMD for various separations encountered in chemical, pharmaceutical, and environmental industries. This talk will present the methodology and an important real-world case study.

The geologic formations that contain oil and gas deposits also contain naturally-occurring radionuclides, which are referred to as Naturally Occurring Radioactive Materials (NORM). Oil and gas fracking brings NORM to the surface in a concentrated form, which could pose a radiation safety hazard. Further, NORM levels have the potential to climb over time as the fluid being extracted begins to contain proportionally greater amounts of brine. Therefore, the majority of produced water contains significant levels of NORM. In 2011, GTI carried out a Techno-economic Assessment of Water Management Solutions project (2011) supported by a consortium of 23 companies. This consortium identified many priority industrial challenges for the pre- and post-crossover stages of a shale gas development area's water-based life cycle and identified NORM removal as one of the highest priority research areas. They also ascertained that there is currently no commercial product on the market to remove NORM from concentrated produced and flowback waters selectively. In this work, we have used CAMD to design novel clay-based adsorbents for removing 99.9% removal of NORM from produced water. With NSF funding, we then synthesized the adsorbents in the laboratory to show the effectiveness of CAMD. The new adsorbents perform an order of magnitude better than existing adsorbents for NORM removal. We carried out these experiments using produced water from Permian Basin. The concentration of NORM (Radium) in this water was more than 4000 pCi/g. According to regulations, the acceptable quantity of NORM for groundwater is 30 pCi/g. With our novel adsorbents, we could remove NORM from this water to the limit undetectable.

Keywords: Adsorbents, NORM, CAMD, Produced water.

References:

1. Benavides, P. and Diwekar, U., 2015. Optimal design of adsorbents for NORM removal from produced water in natural gas fracking. Part 1: Group contribution method for adsorption. Chemical Engineering Science, 137, pp.964-976.
2. Benavides, P. and Diwekar, U., 2015. Optimal design of adsorbents for NORM removal from produced water in natural gas fracking. Part 1: Group contribution method for adsorption. Chemical Engineering Science, 137, pp.964-976.
3. Doshi, R., Mukherjee, R. and Diwekar, U., 2018. Application of Adsorbate Solid Solution Theory To Design Novel Adsorbents for Arsenic Removal Using CAMD. ACS Sustainable Chemistry & Engineering, 6(2), pp.2603-2611.