110th Anniversary: Industrial Process Water Treatment and Reuse

Article Cite This: Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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110th Anniversary: Industrial Process Water Treatment and Reuse Enabled by Selective Ion Exchange Materials Brandon W. Heimer,*,† Scott M. Paap,† Koroush Sasan,‡ Patrick V. Brady,‡ and Tina M. Nenoff*,‡ †

Sandia National Laboratories, P.O. Box 969, Livermore, California 94551, United States Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185, United States

‡

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S Supporting Information *

ABSTRACT: Silica (SiO 2 ) is ubiquitous in petroleum produced waters; removal and recovery of silica reduces fouling when upcycling these waters for industrial applications. Herein, we report the relevant properties of a selective silica recovery material, calcined hydrotalcite (HTC), as well as the design and economic analysis for its use in an ion exchange process to remove silica from produced water. This process improves upon established technologies by minimizing sludge product, reducing process fouling, and lowering energy use. The ion exchange capacity of HTC (approximately 45 mg SiO2/g HTC) and optimized thermal reaction conditions (550 °C for 30 min) for calcination and regeneration were determined experimentally and used in the process modeling. Modeling outputs included raw material requirements, energy use, and the minimum water treatment price (MWTP). Monte Carlo simulations for process economics showed how R&D improving HTC reusability and silica binding capacity as well as separate reductions in raw material price can decrease MWTP by 40%, 13%, and 20%, respectively. (RO),19 and nanofiltration (NF)20 with treatment costs ranging from $4.00−5.50/1000 gal ($1.06−1.45/1000 L).8,21 The mature methods for silica removal have advantages including the coreduction of hardness and alkalinity (soda-lime softening), ease of operation and high-quality water (ion exchange), and removal of 95%+ total dissolved solids including both reactive and nonreactive silica (reverse osmosis); however, they suffer from several notable drawbacks. Soda-lime softening generates large amounts of sludge that incurs dewatering, transportation, and disposal costs.8,22 Many IX processes utilize resins that can be costly to regenerate and replace.23 RO and NF are energy intensive and rely on membranes that are susceptible to fouling.24,25 Inorganic IX separation media have the potential to remove silica directly from a variety of waters and lower the energy penalty for treatment. Our previous work described the synthesis and characterization of high capacity and selective hydrotalcite (HTC) materials.26−28 Hydrotalcite-like compounds are layered double hydroxides x+ − (II) (III) [M(II) = Mg2+, Ca2+, 1−xMx (OH)2] [A] ·mH2O where M 2+ 2+ 2+ 2+ 2+ (III) 3+ Mn , Fe , Co , Ni , and Zn ; M = Al , Cr3+, Mn3+, Fe3+, 2− Co3+, and Ga3+; and A = Cl−, Br−, I−, NO−3 , CO2− 3 , SO4 , silicate-, polyoxometalate, and/or organic ions. The layered double hydroxide (LDH) crystal structure of HTC consists of positively charged layers of [M(II)/M(III)/(OH)] octahedra with

1. INTRODUCTION Water and energy systems are deeply connected and, in many ways, interdependent.1 Growth in population centers and agriculture has increased the demand for fresh water2,3 while regions of the Western United States have suffered extended periods of drought leading to decreased supply.4,5 Correspondingly, U.S. petroleum energy consumption has grown and historically tracked with gross domestic product (GDP).6 Enhanced oil recovery (EOR) techniques are now being used to increase domestic crude oil production by 30−60% beyond primary and secondary recovery to satisfy U.S. demand.7 Thermal recovery is one method; it produces salty and sandy water.8,9 This produced water is typically disposed of as waste via underground injection, which can be quite costly in some geographic locations and induce earthquakes.10,11 Treating, or upcycling, produced water can solve two problems: (1) eliminating a waste stream and (2) supplanting fresh water in applications where degraded water may be acceptable and is consumed in large amounts.12 For example, the United States withdraws approximately 60−170 billion gal/day13 (227−644 billion L/day) of fresh water for thermoelectric power generation including 6.6 billion gal/day (25 billion L/day) in the state of California alone.14 However, dissolved silica and other scalants must be removed before produced water can be used in such applications.8 Treating these degraded waters at inland sites has been estimated to cost 1.5−2.5-fold more than freshwater due largely to the high cost of silica removal.8 Current methods used to remove reactive silica include soda-lime softening,15−17 ion exchange (IX),18 reverse osmosis © XXXX American Chemical Society

Received: Revised: Accepted: Published: A

April 22, 2019 July 15, 2019 July 16, 2019 July 16, 2019 DOI: 10.1021/acs.iecr.9b02200 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research

Figure 1. Process flow diagram for HTC calcination, silica removal, and post-treatment conditioning. Carbon dioxide liberated during HTC calcination is captured and bypassed to the aerator to decrease the pH of the effluent.

room temperature to equilibrate. Solids were separated by centrifugation, and the silica concentration of the supernatant was measured using Hack and ICP-MS. The amount of silica removed from CCTW was computed using a mass balance by subtracting the product of the remaining silica concentration and volume of water from the initial silica loading. The equilibrium HTC ion exchange capacity was determined by dividing the amount of silica removed from CCTW by the HTC loading. This process was repeated for initial HTC loadings of 25, 75, and 125 mg, and the results were averaged at each loading. 2.2. HTC Calcination Optimization. Silica removal was evaluated as a function of HTC thermal treatment (i.e., calcination) at 550 °C for durations of 10, 20, 30, 40, 50, and 60 min. A 25, 50, and 75 mg sample of HTC calcined for each amount of time was each dispersed into 50 mL of CCTW and placed on a shaker table for 12 h at room temperature. Silica removal was quantified using the methods described above. Plots of silica removed versus HTC loading mass for each calcination time were made to determine the minimum thermal treatment time that removed silica at the same, or nearly the same, level as the material treated for 3 h. HTC’s capacity to remove silica from water can be regenerated by repeating the calcination process. To determine the number of regeneration steps that can be performed before HTC’s silica binding capacity was diminished, HTC was calcined at 550 °C for 30 min, cooled, dispersed into 50 mL of CCTW and placed on a shaker table for 12 h at room temperature. Silica removal was quantified using the methods as described above, HTC was removed from the tube, dried, and recalcined. This process was repeated iteratively until the silica quantification assay showed significantly decreased silica removal capacity. 2.3. Degraded Water and Plant Size. The feedstock for the process presented here is degraded water produced during oil and gas recovery. The formulas shown in Table S1 are representative of waters produced from wells in California’s Central Valley.8 The silica removal process is designed to condition this water for use in thermoelectric power generation cooling operations where the “exceedingly high” silica

anions residing between layers. These anions (A) can be displaced with counterions (A′) such as silicates (H3SiO−4 or H2SiO2− 4 ) in the classical ion exchange process. Calcined HTC removes silica from water approximately 9-fold more effectively than does crystalline material. This is because collapsed HTC recrystallizes around the silicate ion when dispersed in aqueous solution in what is described as the “memory affect” process.26 Removing anionic silicates from solution shifts the equilibrium with silica toward the anionic species which can then be removed by HTC, resulting in a net depletion of silica. Herein, we applied materials science, process design, and technoeconomic analysis methods to enable and optimize a silica removal process for the use and recycle of produced oil waters. The resultant output details how to (1) elucidate the necessary material parameters for removing silica from water using HTC, (2) design a representative, commercial-scale process, (3) determine the economic performance of this process to remove silica from a produced water stream with chemistry representative of the California Central Valley given the current state of technology development, (4) quantify the impact of uncertainty and variability in critical process parameters to identify the relative contributions of each to total performance using a Monte Carlo analysis, and (5) inform future research and development efforts to maximize relative performance and economic competitiveness, as well as identify the conditions (e.g., produced water disposal cost, fresh water cost) that would provide the greatest value proposition for adopting this technology.

2. METHODS 2.1. Ion Exchange Capacity Measurement. Hydrotalcite (Mg6Al2(OH)16(CO3)·4H2O) was purchased from Sigma-Aldrich and aliquoted into 15 g batches which were calcined for 3 h each in an oven filled with air at 550 °C. Synthetic concentrated cooling tower water (CCTW) was prepared as 0.41 mM MgCl2, 0.05 mM Na2SO4, 0.62 mM NaHCO3, 1.0 mM CaCl2, 41.0 mM NaCl, and 0.83 mM SiO2 by completely dissolving the salts in deionized water. Calcined HTC, in amounts ranging from 25−125 mg, was dispersed into 50 mL of CCTW and placed on a shaker table for 12 h at B

DOI: 10.1021/acs.iecr.9b02200 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article


and (2) identify the cost drivers for operating the process to determine cost/benefit for future research and development (R&D) efforts. This TEA approach adopts “nth-plant” economics in which we assume that n other plants have been previously constructed at other sites and are operating using the same technology. Neglecting one-time R&D costs and the risk associated with starting-up a pioneer plant provides a fairer basis of comparison to mature technologies. The thermodynamic relations, equipment-level material and energy balance calculations, and capital and operating expenses were implemented in a deterministic model. The process was subdivided into the three unit operations described in sections 2.4.1 through 2.4.3, and calculations were performed separately for each and combined for the aggregate analyses. This analysis was conducted assuming a twenty-year plant economic life. The total cash flow, including both capital and operating costs, for each year of operation was discounted to the base analysis year to calculate the net present value (NPV) of the project. Setting the NPV equal to zero allowed us to determine the break-even point corresponding to the MWTP. The complete set of raw material/utility prices and financial parameters used in the analysis are shown in Tables S4 and S5, respectively. 2.5.1. Monte Carlo Analysis. Process and economic modeling were supported by laboratory experiments. We used Monte Carlo analysis methods to formally include uncertainty and variability in the water treatment cost estimate because pilot scale performance has not yet been determined.26 Maximum and minimum values for a subset of the model’s input parameters (see Table S6) were estimated from the literature, market data, experimental results, or, when none of these were available, best engineering judgment. The distribution of probable values within each range was chosen to best reflect the basis of the natural uncertainty in the associated input parameter. A triangular distribution was used when only the maximum, minimum, and the baseline (or “most likely”) values were known. The Crystal Ball (Oracle) application was used to execute 10 000 deterministic model trials each using a separate set of parameter values randomly sampled from the corresponding probability distribution.

concentration greatly limits the cycles of concentration achievable in the cooling tower. The plant was scaled to 2.8 million gallons per day (MGD) (4.4 × 105 kg/h) to meet the demand for makeup water in a cooling tower operating with side-stream softening at a 500 MW generating facility.8 2.4. Process Description. The process flow diagram in Figure 1 shows all major steps required to treat produced water including calcining/regenerating HTC, silica removal, and post-treatment conditioning. A carbon dioxide bypass stream was evaluated to reduce the plant’s greenhouse gas emissions and acid demand for pH adjustment during post-treatment conditioning. Each step is described in greater detail in the following subsections. The mass flow rate for each stream in Figure 1, and the major design parameters for each process area are shown in Tables S2 and S3, respectively. 2.4.1. HTC Calcination. The endothermic calcination reaction (ΔH°rxn = +250 J/g) is shown below:29 Mg6Al 2(OH )16 (CO3) ·4H2O → 5MgO·MgAl 2O4 + 12H2O + CO2

HTC is calcined using a rotary kiln in the process described here. The residence time for HTC in the kiln was determined experimentally by evaluating silica removal as a function of thermal treatment at 550 °C. Incorporating a recycle stream into Figure 1 also allows the HTC material to be recalcined and used multiple times before being discarded. The calcination process liberates water vapor and carbon dioxide, in an 83:17 mass ratio, which reduces the solid HTC mass exiting the kiln by approximately 43%. The capture and bypass of these gas phase products were evaluated and compared in an effort to establish the most favorable process to reduce carbon emissions and alleviate consumption of sulfuric acid (used in the pH neutralization of treated water). The option of capturing water vapor and CO2 would require using an indirectly fired rotary kiln to avoid carbon dioxide dilution from air flow in an open, directly fired rotary kiln. This concept as well as the alternative of using a directly fired rotary kiln with no CO2 capture were evaluated and compared for overall economics. 2.4.2. Silica Removal via Ion Exchange. Calcined HTC is fed into a vertical, cylindrical pressure vessel. Two such units are shown in Figure 1 because it is expected that one vessel will operate on-stream while the HTC from the other vessel is being regenerated. Produced water with high ionic silica concentration is pumped over the packed bed of HTC, and treated water is discharged as alkaline solution at approximately pH 11. The increase to pH 11 is a result of hydroxide anions generated during HTC recrystallization.26 2.4.3. pH Adjustment. Treated water is neutralized to pH 7.5 to meet cooling tower requirements for pH (7.5−8.5) and help remove the solution sulfides by shifting the equilibrium toward the volatile species.8 Sulfuric acid, bubbling CO2 (captured as a byproduct from HTC calcination), or a combination thereof are the preferred methods analyzed. If CO2 is used, the flue gases from the kiln are passed through a condenser to remove water; the CO2 is then subsequently compressed for delivery to the aerator vessel via a distribution manifold. 2.5. Techno-economic Analysis. The techno-economic analysis (TEA) here serves two purposes: (1) determine the minimum water treatment price (MWTP) to serve as a barometer of commercial viability for the HTC-based process

3. RESULTS AND DISCUSSION 3.1. Ion Exchange Capacity, Calcination, and Regeneration. The ion exchange capacity of calcined HTC for ionic silica was determined to be 45 mg SiO2/g HTC, approximately 9-fold greater than crystalline HTC. This is due to the significantly higher surface area of the calcinated material relative to crystalline HTC.26 Herein, thermal treatment of HTC at 550 °C was evaluated for time periods ranging from 10−60 min to determine the parameters for process-scale operation; see Figure 2. Thirty minutes was deemed sufficient because longer calcination durations produced only marginally greater silica removal and would adversely affect both process capital cost due to larger equipment requirements and operating costs due to greater natural gas fuel consumption. Thermally regenerating spent HTC by repeating the calcination process following silica removal was iteratively tested to determine the material’s reusability. The data in Figure 3 show that HTC can be regenerated three times before it is unable to remove >95% of silica from the influent. The removal efficiency decreased because accessible sites on HTC become occupied with Si species, and recalcination no longer compensates by opening HTC layers to access additional C


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Table 1. Cost Comparison of Silica Removal Technologies cost component inlet water utilities raw materials labor maintenance and overhead raw water/waste disposal depreciation (10-y) taxes and insurance avg return on investment MWTP (2015 USD/ 1000 gal) MWTP (2015 USD/ 1000 L)

Figure 2. Optimizing HTC calcination time: Impact of HTC mass and calcination time at 550 °C on silica removal from 50 mL water (pH 7.8, 25 °C, 122 mg/L SiO2).

a

ion exchange21

double-pass RO21

lime softening8

$0.14 $1.96 $0.49 $0.40

$0.56 $0.47 $0.37 $0.35

$0.11

$0.14

$0.61

$2.01 $0.43

$1.76 $0.38

$0.21

$0.33 $0.20 $1.47

$5.52

$4.03

$4.71

$22.86

$1.46

$1.07

$1.24

$6.04

HTCa

$0.21 $3.68

$0.10 $19.10 $0.99 $0.68

This work.

H2SO4 was modeled as an addition to the process for pH adjustment, thereby eliminating the need for CO2 bypass. The purpose of the Monte Carlo analysis was to formally include uncertainty and variability in the water treatment cost estimate as well as facilitate comparison of this process with the existing technologies described above. The Monte Carlo analysis produced a stochastic distribution of MWTP with median and mean values of 15 and 17 ± 9 2015 USD/1000 gal (3.96 and 4.49 ± 2.38 2015 USD/1000 L), respectively. Complete statistics from the Monte Carlo analysis are shown in Table S7. Note that these values are lower than the 23 2015 USD/1000 gal (6.04 2015 USD/1000 L) baseline MWTP (a deterministic output given the current state of technology) because the Monte Carlo analysis included values representing projected process improvements. Each parameter input range (shown in Table S6) was centered on the most likely value between plausible upper and lower bounds. Values for these ranges were based on the current state of technology. The wide range of MWTP values generated appears to follow a lognormal distribution. However, the variability captures only the economic and technological uncertainties and not all possible combinations among the variables or the dependencies among variables. Some values, including financial and project investment parameters (e.g., warehouse factor and working capital) were not varied. The break-even price for water treatment is shown on a component basis in Table 1 for membrane based ion exchange,21 double-pass reverse osmosis,21 lime softening,8 and the HTC based ion exchange method described here. These mature technologies are expected to incur only incremental changes over time; as such, we used the cost index for purchased equipment (Chemical Engineering), industrial chemicals producer price index (U.S. Bureau of Labor Statistics), and average hourly earnings, chemical manufacturing (U.S. Bureau of Labor Statistics) to adjust each cost component for these technologies from the basis year to the year of analysis to facilitate a more accurate comparison. Interestingly, the HTC process incurs the smallest energy utility cost. Both the HTC and lime softening processes also benefit from the lowest relative capital depreciation costs. However, the analysis shows that due to the high cost of the raw material, the HTC method is the most costly to operate. The median and mean values from the Monte Carlo analysis

Figure 3. HTC regeneration: silica removal from CCTW (pH 7.5, 25 °C, 50 mg/L SiO2) versus number of times HTC (125 mg loading) is calcined.

sites.26,30 Therefore, spent HTC needs to be replaced with fresh calcined HTC material. The details for this process operation are described in sections 2.4.1 and 2.4.2. 3.2. Near-Term HTC Process. The process shown in Figure 1 was the basis for both mass and energy calculations, as well as capital and operating expense calculations. The MWTP for the baseline case was $0.023/gal (23 2015 USD/1000 gal or 6.08 2015 USD/1000 L); the components contributing to the total are shown in Table 1. Variable operating costs (e.g., raw materials and utilities) comprise 84% of the total or $0.019 for every gallon ($0.005/L) of water treated and are driven principally by HTC consumption. Capital depreciation is a minor expense equivalent to only 1.6% of the annual operating cost. Capture of CO2 that was liberated during HTC calcination was anticipated as necessary for both the reduction of greenhouse gas emissions and sulfuric acid consumption for neutralizing the basic treated water. However, the modeling results indicated it was not economical due to the cost of additional required capital equipment. Details of the analysis are provided in the Supporting Information. For this reason, D


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Industrial & Engineering Chemistry Research represent a cost 2- to 4-fold greater than these existing methods. It is very important to note that the existing technologies are well-established and optimized from many years of use. For example, lime softening has been used for silica removal since the 1940s.15 Technology improvement and maturation over this time led to performance enhancements.16 3.3. Projected Improvements to the HTC Process. HTC was only recently demonstrated for specific silica sorption in the laboratory.26 The optimized performance of this material will improve with process and materials optimization toward its commercial deployment. Therefore, Monte Carlo was used to evaluate improvements in HTC material properties (ion exchange capacity and reusability) as well as HTC cost reductions. Furthermore, the modeling was used to account for the other remaining uncertainties in the scenarios described below. Justification for each parameter value and range are provided in the Supporting Information. 3.3.1. Baseline Produced Water Scenario. This represents the current state of technology for silica removal using HTC based on the produced water baseline described in section 2.3. 3.3.2. High Reusability Scenario. This follows the same parameter ranges as the baseline produced water scenario but assumes HTC can be recycled seven times possibly due to future material preparation method refinements. 3.3.3. High Binding Capacity Scenario. This scenario follows the same parameter ranges as the high reusability scenario but assumes that the HTC binding capacity is 120 mg/g. 3.3.4. Low HTC Price Scenario. This follows the same parameter ranges as the high binding capacity scenario but assumes that the HTC costs $2.50/kg. Potential HTC price reductions were determined in consultation with HTC suppliers based on the notion that increases in demand for the raw material (as more HTC-based water treatment processes are deployed) would allow them to achieve economies of scale in production thereby reducing costs toward the gross margin for producing HTC. The MWTPs for each of the stochastic scenarios are compared in Figure 4. Improving HTC reusability yields the greatest effect and causes the median cost to decrease 40% from 15 to 9 2015 USD/1000 gal (3.96 to 2.38 2015 USD/

1000 L). The reductions from improving silica binding capacity and reduced HTC cost are more modest but yield reductions of 13% and 20%, respectively. Together they bring the best-case cost down to 4 2015 USD/1000 gal (1.06 2015 USD/1000 L), or 27% of the baseline value. This MWTP would clearly be competitive with the technologies shown in Table 1. Silica removal technologies based on HTC ion exchange methods will be economical in certain key applications. Colocation or near-location of HTC facilities to produced water generation sites will dramatically decrease or eliminate produced water disposal transportation costs. Currently, disposal costs vary over an order of magnitude ($1.67/1000 gal−$38.10/1000 gal or $0.44/1000 L−$10.06/1000 L) based on where the water is generated.10 This cost is primarily determined by the distance produced water must be transported to an injection well for disposal. That costly transport is often performed by truck. Produced water generators with many nearby injection wells, therefore, pay dramatically lower disposal prices due to lower transportation costs.10 This dynamic exists because oil field operators are required to dispose of the produced water at the closest injection well. Furthermore, the injection wells’ locations are determined by both geography and geology, not proximity to oil fields. This scalable, HTC-based treatment process reported here can be colocated with produced water generators and water consumers to provide substantial water transportation cost savings. Additional external factors favoring HTC silica removal processes are at locations which are experiencing severe drought conditions. For example, in 2014, Kern County in California’s Central Valley had astronomically high freshwater prices due to an extended drought. At a maximum, the high open market for freshwater was priced at $3.99/1000 gal ($1.05/1000 L).31 The ability to reduce the need for this costly freshwater for use in local industrial and agricultural processes by using recycled HTC process water will dramatically reduce the county’s need to buy freshwater. Furthermore, the sum of revenue saved from disposing produced water and providing treated water will move processes into the economically sound arena.

4. CONCLUSIONS Described herein is the economic analysis and process design for using, recovering, and recycling the inorganic, ion exchanger hydrotalcite (HTC) for the purpose of removing ubiquitous silica from water produced during enhanced oil recovery. The modeled process shows how the HTC can be thermally treated using a rotary kiln for 30 min at 550 °C. Then produced water is pumped across a packed bed of calcined HTC and neutralized with sulfuric acid before discharge. Experimental measurements demonstrated that HTC has an ion exchange capacity of 45 mg SiO2/g HTC and can be regenerated by repeating the calcination heat treatment process. Techno-economic analysis showed that economic performance of the process is most strongly influenced by HTC material properties: silica binding capacity, number of HTC regeneration cycles, and raw material purchase cost. Monte Carlo based scenario analysis showed that, despite having a current treatment cost of approximately 17 ± 9 2015 USD/ 1000 gal (4.49 ± 2.38 2015 USD/1000 L), reasonable levels in improvement across these parameters could improve the

Figure 4. Stochastic minimum water treatment price distributions for four scenarios given potential improvements on HTC materials. Statistics for all four distributions are shown in Table S7. E


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(5) Borsa, A. A.; Agnew, D. C.; Cayan, D. R. Ongoing droughtinduced uplift in the western United States. Science 2014, 345 (6204), 1587. (6) Annual Energy Review 2009; U.S. Energy Information Administration: Washington, D.C., 2010. (7) U.S. Department of Energy Enhanced Oil Recovery. https:// energy.gov/fe/science-innovation/oil-gas-research/enhanced-oilrecovery. (8) Electric Power Research Institute. Use of Degraded Water Sources as Cooling Water in Power Plants, 1005359; Palo Alto, CA, 2003. (9) Veil, J. A.; Puder, M. G.; Elcock, D.; Redweik, J., Robert, J. A White Paper Describing Produced Water from Production of Crude Oil, Natural Gas, and Coal Bed Methane; Argonne National Laboratory: Lemont, IL, 2004. (10) Mittal, A. K.; Rusco, F. ENERGY-WATER NEXUS Information on the Quantity, Quality, and Management of Water Produced during Oil and Gas Production; United States Government Accountability Office: Washington, D.C., 2012. (11) Ellsworth, W. L. Injection-Induced Earthquakes. Science 2013, 341 (6142), 1225942. (12) Gupta, V. K.; Ali, I.; Saleh, T. A.; Nayak, A.; Agarwal, S. Chemical treatment technologies for waste-water recyclingan overview. RSC Adv. 2012, 2 (16), 6380−6388. (13) Averyt, K.; Fisher, J.; Huber-Lee, A.; Lewis, A.; Macknick, J.; Madden, N.; Rogers, J.; Tellinghuisen, S. Freshwater Use by U.S. Power Plants: Electricity’s Thirst for a Precious Resource; The Union of Concerned Scientists’ Energy and Water in a Warming World Initiative: Cambridge, MA, 2011. (14) Maupin, M. A.; Kenny, J. F.; Hutson, S. S.; Lovelace, J. K.; Barber, N. L.; Linsey, K. S. Estimated use of water in the United States in 2010, U.S. Geological Survey Circular 1405; U.S. Geological Survey, 2014; p 56. (15) Behrman, A.; Gustafson, H. Removal of silica from water. Ind. Eng. Chem. 1940, 32 (4), 468−472. (16) Sheikholeslami, R.; Al-Mutaz, I. S.; Koo, T.; Young, A. Pretreatment and the effect of cations and anions on prevention of silica fouling. Desalination 2001, 139 (1), 83−95. (17) Al-Mutaz, I. S.; Al-Anezi, I. A. Silica removal during lime softening in water treatment plant. International Conference on Water Resources & Arid Environment, 2004; King Saud University Riyadh, 2004. (18) Sik Ali, M. B.; Hamrouni, B.; Bouguecha, S.; Dhahbi, M. Silica removal using ion-exchange resins. Desalination 2004, 167, 273−279. (19) White, M. J.; Masbate, J. L., Jr.; Gare, S. G. Reverse Osmosis Pre Treatment of High Silica Waters; GE Water & Process Technologies, 2010. (20) Liu, Y.; Tourbin, M.; Lachaize, S.; Guiraud, P. Silica Nanoparticle Separation from Water by Aggregation with AlCl3. Ind. Eng. Chem. Res. 2012, 51 (4), 1853−1863. (21) Beardsley, S. S.; Coker, S. D.; Whipple, S. S. The Economics of Reverse Osmosis and Ion Exchange. In WATERTECH Expo 1994, Houston, TX, 1994. (22) Committee Report. Lime softening sludge treatment and disposal. J. - Am. Water Works Assoc. 1981, 73 (11), 600−608. (23) Xu, T. Ion exchange membranes: State of their development and perspective. J. Membr. Sci. 2005, 263 (1), 1−29. (24) Van der Bruggen, B.; Mänttäri, M.; Nyström, M. Drawbacks of applying nanofiltration and how to avoid them: A review. Sep. Purif. Technol. 2008, 63 (2), 251−263. (25) Salvador Cob, S.; Yeme, C.; Hofs, B.; Cornelissen, E. R.; Vries, D.; Genceli Güner, F. E.; Witkamp, G. J. Towards zero liquid discharge in the presence of silica: Stable 98% recovery in nanofiltration and reverse osmosis. Sep. Purif. Technol. 2015, 140, 23−31. (26) Sasan, K.; Brady, P. V.; Krumhansl, J. L.; Nenoff, T. M. Removal of dissolved silica from industrial waters using inorganic ion exchangers. Journal of Water Process Engineering 2017, 17, 117−123.

economics of the novel HTC materials. As they are still under development, optimization will make them cost competitive with current well-developed technologies. Given the criticality of both energy and water, materials such as these HTCs may satisfy a compelling need to upcycle wastewater into a value stream and further sustainable practices in these sectors. HTC offers both durability and stability over existing technologies as a result of being an inorganic ion exchanger. Additionally, the HTC process benefits from a low capital cost in which capital depreciation accounts for only 1% of the MWTP. The performance of the process is maximized where freshwater is costly and water treatment facilities are located large distances from disposal sites. The value would be maximized where injection wells are sparse/distant and freshwater is scarce. Such geographic factors will be crucial for assessing economic feasibility for constructing treatment processes.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.9b02200.

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Tables S1−S7 and Figures S1 and S2 of data referenced in the manuscript (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (T.M.N.). *E-mail [email protected] (B.W.H.). ORCID

Tina M. Nenoff: 0000-0002-7906-4810 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This research was supported by the Laboratory Directed Research and Development Program at Sandia National Laboratories. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE’s NNSA under contract DE-NA-0003525.

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ABBREVIATIONS HTC = hydrotalcite MWTP = minimum water treatment price NPV = net present value TEA = techno-economic analysis.

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REFERENCES

(1) Bauer, D.; Philbrick, M.; Vallario, B. The Water-Energy Nexus: Challenges and Opportunities; U.S. Department of Energy: Washington, D.C., 2014. (2) Wallace, J. S. Increasing agricultural water use efficiency to meet future food production. Agric., Ecosyst. Environ. 2000, 82 (1), 105− 119. (3) Rijsberman, F. R. Water scarcity: Fact or fiction? Agricultural Water Management 2006, 80 (1), 5−22. (4) Cook, E. R.; Woodhouse, C. A.; Eakin, C. M.; Meko, D. M.; Stahle, D. W. Long-Term Aridity Changes in the Western United States. Science 2004, 306 (5698), 1015. F


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Industrial & Engineering Chemistry Research (27) Sasan, K.; Brady, P. V.; Krumhansl, J. L.; Nenoff, T. M. Exceptional Selectivity for Dissolved Silicas in Industrial Waters using Mixed Oxides. Journal of Water Process Engineering 2017, 20, 187. (28) Bontchev, R. P.; Liu, S.; Krumhansl, J. L.; Voigt, J.; Nenoff, T. M. Synthesis, Characterization, and Ion Exchange Properties of Hydrotalcite Mg6Al2(OH)16(A)x(A′)2-x·4H2O (A, A′ = Cl-, Br-, I-, and NO3-, 2 ≥ x ≥ 0) Derivatives. Chem. Mater. 2003, 15 (19), 3669−3675. (29) Bankauskaite, A.; Baltakys, K. Thermal, texture and reconstruction properties of hydrotalcites substituted with Na or K ions. J. Therm. Anal. Calorim. 2015, 121 (1), 227. (30) Teodorescu, F.; Pălăduţa,̆ A. M.; Pavel, O. D. Memory effect of hydrotalcites and its impact on cyanoethylation reaction. Mater. Res. Bull. 2013, 48 (6), 2055−2059. (31) Onishi, N. A California Oil Field Yields Another Prized Commodity; The New York Times, July 8, 2014.

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110th Anniversary: Industrial Process Water Treatment and Reuse

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