Grantee Research Project Results
Final Report: A Novel 2D MoS2 Sponge Oil-Water Separator (MDSOS)
EPA Grant Number: SV839489Title: A Novel 2D MoS2 Sponge Oil-Water Separator (MDSOS)
Investigators: Lee, Woo Hyoung , Hwang, Jae-Hoon , Jung, Yeonwoong
Institution: University of Central Florida
EPA Project Officer: Page, Angela
Phase: II
Project Period: April 1, 2019 through April 11, 2020 (Extended to March 31, 2022)
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2019) Recipients Lists
Research Category: P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards
Objective:
This project aimed to separate oil from water using an oleophilic sponge enveloped with hydrophobic materials, polydimethylsiloxane and molybdenum disulfide. Using these sponges in combination with a pumping system, the purpose of this research was to rid oil from contaminated waters and into an oil recovery tank for further recyclability (CWA: Clean Water Act–Section 104; OPA: Oil Pollution Act, 101 H.R.1465, P.L. 101-380). This project established and advanced fundamentals associated with a vision of conserving our water resources using an innovative sponge technology that could help clean waterways after a crude oil spill. This technology proposes to curb water pollution by creating an oil-water separator that soaks up oil but repels water, leaving behind no toxic byproduct. The objectives of the Phase II project are to 1) improve oil-separation proficiency by optimizing sponge porosity; 2) develop the self-floating oil spill detecting sensor, which stems from the intrinsic oil-water separation capability of the MoS2-PDMS sponges as well as their excellent conductivity for electrical sensing; 3) employ the technology towards real world application such as by remediating crude oil and scaling up MDSOS for oil separation in the field; 4) investigate an environmental and economic life cycle assessment; and 5) establish an operator guideline for the oil-collection system.
Summary/Accomplishments (Outputs/Outcomes):
For the 2nd year of the Phase II project, the oil-separation proficiency was improved by optimizing sponge porosity and with the following specific objectives. In situ crude oil separation using a solar simulator demonstrates accelerated recovery of the crude oil utilizing the self-heating of MDSOS.
Specific Objective 1: Design and develop an MDSOS based solar heater for decreased oil’s viscosity
The novel superhydrophobic sponge was fabricated by combining 2D nanostructured MoS2 and auxetic patterned MoS2-PU (polyurethane) sponges with controlled geometries. The MoS2 coating and sponge morphology was confirmed using surface characterization methods (e.g., SEM and TEM).
Specific Objective 2: Evaluate the thermal performance of a 2D MoS2 layer-based solar heater
MDSOS with 10 wt% of MoS2 showed the max temperature reaching up to 73.4 °C within 15 min, while the PU sponge without MoS2 reached around 39.3 °C after ~15 min under natural sunlight at the outdoor temperature ~30 °C. Under the simulated solar simulator of 790 W/m2 (0.79 Sun), the MDSOS showed a max temperature of 70.8 °C within 10 min.
Specific Objective 3: Evaluate environmental and economic life cycle assessment (LCA)
Excluding the price of the utilized 3D printer for polyvinyl alcohol (PVA) scaffold fabrication, rough estimates of the PVA (2×2×2 cm3) scaffold cost around $0.50 – 0.60 per one sponge (~$0.10 per g), and the completed MoS2-PU sponges cost less the 20 cents ($0.09 – 0.22 per one 2×2×2 cm3 sponge = $0.03 – 0.07 per g).
Our results demonstrated that the superhydrophobic 2D MoS2 sponge technology with solar light is a feasible strategy for removing crude oil from water with effective oil separation capacity without the formation of hazardous byproducts. We continued several outreach activities, including NSF’s Innovation Corps (I-Corps) and the identification of potential partners. The activities related to I-Corps focused on obtaining relevant market data that indicates the requirements necessary for a technology to be successfully adapted in commercialization. This data was obtained by conducting over 100 interviews with employers relative to the field of oil spill management, such as oil spill response organization (OSROs) directors and marine technicians. From these interviews, key points included the need to improve oil-water separation such that the volume remediated does not reach the boat’s daily carrying capacity quickly and that increased processing costs due to difficulty in treatment of mixed oil and water solutions are minimized. Critical analyses of the qualitative data obtained via interviews were then applied to the focus of optimizing the MoS2 sponge technology for field applications. We also evaluated environmental and economic life cycle assessment, focusing on cost analysis. From the results, we also submitted one proposal to NSF Partnership for Innovation Technology Translation (PFI-TT) track with a title of “PFI-TT: Towards a Smart Oil Sponge for Industrial Application” (not selected) working with many potential collaborators (e.g., Greater Orlando Aviation Authority, Orange Country, and ASCE’s Environmental & Water Resources). A comparison of actual accomplishments with the anticipated objectives (outputs/outcomes) specified in the original proposal is shown in the table below.
Conclusions:
Specific Objective 1: Design and develop an MDSOS based solar heat for decreased oil’s viscosity
We developed 2D MDSOS (2D MoS2-embedded sponges) utilizing 3D printing technologies to create auxetic patterned MoS2-PU (polyurethane) sponges. For the effective water evaporation performance of MoS2-PU sponges, we fabricated precisely ordered porous structures that will exhibit "negative Poisson's ratios" [1] by utilizing the 3D printing process. The auxetic-patterned scaffold, which was made of a water-soluble polyvinyl alcohol (PVA) template (2×2×2 cm3) for the MoS2-PU sponges, was fabricated using a 3D printer (co-PI, Dr. Jung's lab) as shown in Figure 1. Figure 1(a) shows the schematic procedure of the MoS2-PU sponge fabrication process using the 3D printed PVA scaffold. Also, using the 3D printed PVA frame, MoS2-PU solution was poured into the 3D printed PVA scaffold with a PVA frame and cured (dried) for ~48 hours, as shown in Figure 1(b) and (c). The MoS2-PU solution was composed of ClearFlex 50 (Urethane Rubber (PU)) mixed with a controlled MoS2 concentration of around 10 wt%, which was the maximum concentration allowed for the enhanced solar-to-heat generation process. Figure 1(d) shows the completed MDSOS (left) after dissolving the water-soluble PVA scaffold in DI water for ~48 hours using the sonication process.
Fig. 1. (a) Fabrication process of MDSOS sponge (b-d) Photo images of (b) a 3D printed PVA scaffold and a PVA frame, (c) MoS2-PU solution poured onto the scaffold in the frame for the drying stage (~48 hrs), (d) fabricated MDSOS.
Specific Objective 2: Evaluate the thermal performance of a 2D MoS2 layer-based solar heater: “Self-heating” MDSOS development
We compared the "self-heating" of the MDSOS (2×2×2 cm3, PU sponges with MoS2, 10 wt%) to the PU sponge without MoS2, as shown in Figure 2(a). As anticipated, MDSOS with 10 wt% of MoS2 showed the max temperature reaching up to 73.4 °C within 15 min, which is more than two times the outside temperature, while the PU sponge without MoS2 reached around 39.3 °C after ~15 min under natural sunlight at the outdoor temperature ~30 °C, as shown in Figure 2(b). Also, when the solar simulator (~0.79 Sun = ~790 W/m2) was used for the indoor experiment, the temperature of MDSOS rose above 70.8 °C in ~10 mins, as shown in Figure 2(d). When the sponge was placed inside the crude oil for the experimental pumping apparatus, the temperature of the MDSOS still reached above 70 °C in 15 min and maintained the max temperature with a slight delay as the self-heating MDSOS transferred its heat to the surrounding crude oil, reducing the viscosity of the crude oil, as shown in Figure 2(c).
Fig. 2. (a) Fabricated MDSOS with MoS2-incorporated (left, black) and without MoS2 (right, white). (b) IR images of photo-induced heat generation under the sun (~1,343 W/m2) that shows max temperature reaching up to 73.4 °C (left) for MDSOS while the PU sponge without MoS2 (right) reaching around ~39.3 °C after ~15 min. (c) Time dependent max temperature change when the MDSOS was placed on the crude oil where Max temperature of above 70 °C reached in 15 min. (d) IR image of the MDSOS sample under the simulated sun (~790 W/m2) shows max temperature reaching up to 70.8 °C using a solar simulator.
Encouraged by the preliminary "self-heating" results of MDSOS, we performed a continuous collection of crude oil in situ from a water surface, as shown in Figures 3 and 4. Figure 3 shows a schematic illustration of the pump apparatus using a peristaltic pump connected to the self-heating MDSOS under sunlight (Solar simulator) for crude oil recovery from water. In the pumping process with the solar simulator (~0.79 Sun = ~790 W/m2), we initially applied the solar simulator for ~15 min to allow MDSOS to reach its maximized solar-to-heat conversion process. When the MDSOS effectively converted the simulated sunlight to heat, exhibiting its significant self-heating property, the converted heat was transferred to the surrounding and lowered the viscosity of the crude oil. A previous study reports that the diffusion of highly viscous crude oils through the pores of sorbent materials is very slow, resulting in an inefficient oil-sorption speed for remediation application [2]. Thus, a light crude oil of lower viscosity would facilitate treatment by increasing oil diffusion. According to Ge et al., the viscosity of model oils is below 500 mPa·s, and ranges from 1-100 mPa-s for light crude oils [2]. Therefore, by increasing the temperature, the oil's viscosity can be reduced, and the penetration efficiency through porosity within the adsorbent can be increased, thus significantly improving the oil absorption rate. Samples of crude oil from three different units (Point Arguello, Santa Ynez, and Navy Standard Bilge Mix (NSBM)) obtained from the U.S. Naval Research Laboratory (NRL), is measured to be 7,130 mPa·s (Point Arguello) at ambient temperature, while raising the temperature to 50 °C decreased the viscosity to <800 mPa·s, indicating a drastic (~10 times) reduction as shown in Figure 4 (a). The viscosity of each oil sample (Figure 4(c)) and the temperature were measured using the Viscometer (NDJ-8S Digital Rotary, Graigar Technology Co., Ltd, Shenzhen, China) (Figure 4(a)) and thermometer Figure 4b.
Fig. 3. Schematic illustration of the in-situ recovery of the crude oil from DI water using the peristaltic pumping apparatus under the sunlight using the MDSOS.
Fig. 4. (a) NDJ-8S Digital Rotary Viscometer used for viscosity measurements. (b) Plots of the collected crude oil visicisity under different temperatures of the MDSOS. (c) Crude oil (point Arguelio (left) and Santa Ynez (right)).
However, Santa Ynez oil achieved the lowest viscosity at 612 mPa-s. When heated to 50 ᵒC, the results show that the oils tested, particularly Santa Ynez oil, neared the viscosity of model oils used in previous reports showing high sorption capabilities [3,4]. It is expected that by efficiently increasing the temperature of spilled oil (e.g., over 40°C), the removal rate using a sorbent material can be significantly improved. Since the temperature range selected is similar to that observed in real sea environments, these results indicate that the oils selected for evaluation have sufficiently low heat capacity, suitable for decreasing viscosity as observed by the effects of natural sunlight.
When we started the MDSOS pumping system under the simulated sunlight, 0.786g of the crude oil was collected in 10 mins, and no water was observed in the collection beaker, as shown in timelapse images in Figure 5(a). While no collection of crude oil was observed when the oil was at room temperature (crude oil at 22 °C with a viscosity above 7130 mPa·s), 0.264g of the crude oil was collected when the temperature of the crude oil was raised to ~30 °C (lowering the viscosity to ~3559 mPa·S) using a hotplate setting at 60 °C, as shown in Figure 5(b). When the crude oil was at ~22 °C, we did not observe any oil collected for more than an hour, but when we lowered the viscosity by increasing the temperature, continuous recovery (collection) of the crude oil was observed. Figure 5(c) plots show the continuous collection of the crude oil in situ from the water surface for three different situations (without the solar simulator, with the solar simulator, and with the hotplate). When we compared the amount of collected crude oil for three different situations, MDSOS with the solar simulator effectively collected much more crude oil continuously than the cases with the hotplate or without the solar simulator. As it can be seen from the plot in Figure 5(c), the self-heating MDSOS effectively and continuously collected the crude oil and separated the crude oil from the water by enabling its self-eating capability. Some of the difficulties during the development of MDSOS were outdoor tests where the power of the sunlight was not consistent depending on the time, date, and area compared to the indoor test using the solar simulator. Also, finding the optimal 2D MoS2 powder concentration (wt%) for best performance and the porosity control of MDSOS for optimal crude oil recovery required multiple trials. Additionally, the power of the solar simulator was limited (up to ~790 W/m2 at ~1 cm away from the sample) to test the MDSOS for better performance under the stronger simulated solar illumination.
Fig. 5. (a) Timelapse images showing the accelerated recovery (pumping) of the crude oil (0.786 g in 10 min) from water using the pumping apparatus when MDSOS is illuminated using the solar simulator. (b) Timelapse images showing the recovery of the crude oil (0.264 g in 10 min) from water under the hotplate setting of ~60 °C (crude oil at ~30 °C). (c) Plots of the collected (recovered) crude oils by applying the solar simulator (red), the hotplate (blue, crude oil at ~30 °C), and normal room temperature condition (crude oil at 22 °C) setting (black).
Specific Objective 3: Evaluate environmental and economic life cycle assessment (LCA)
Excluding the price of the utilized 3D printer (~$700) for PVA scaffold fabrication, rough estimates of the PVA (2×2×2 cm3) cost around $0.50 – 0.60 per 2×2×2 cm3 sponge, and the completed MDSOS (2×2×2 cm3) cost less the 22 cents ($0.06 – 0.22) depending on the current price of the MoS2 powders. The LCA addresses the overall costs for oil-water separation and fabrication of the 2D nano MoS2-based oil separator. The estimated cost of use of the MDSOS system has an approximate cost of 13,000 $/tonne, whereas the current oil treatment systems cost anywhere between 15,000 and 16,000 $/tonne [5]. The solar oil-water separator system has so far proven to be more environmentally conscious, economically prosperous, and effectively productive compared to current methods. This is because the MoS2-based evaporator is simple and requires minimal economic or environmental costs.
References:
Quan, C.; Han, B.; Hou, Z.; Zhang, Q.; Tian, X.; Lu, T.J. 3d printed continuous fiber reinforced composite auxetic honeycomb structures. Compos. B. Eng. 2020, 187, 107858.
Ge, J.; Shi, L.-A.; Wang, Y.-C.; Zhao, H.-Y.; Yao, H.-B.; Zhu, Y.-B.; Zhang, Y.; Zhu, H.-W.; Wu, H.-A.; Yu, S.-H. Joule-heated graphene-wrapped sponge enables fast clean-up of viscous crude-oil spill. Nature nanotechnology 2017, 12, 434-440.
Bi, H.; Xie, X.; Yin, K.; Zhou, Y.; Wan, S.; He, L.; Xu, F.; Banhart, F.; Sun, L.; Ruoff, R.S. Spongy graphene as a highly efficient and recyclable sorbent for oils and organic solvents. Advanced Functional Materials 2012, 22, 4421-4425.
Nguyen, D.D.; Tai, N.-H.; Lee, S.-B.; Kuo, W.-S. Superhydrophobic and superoleophilic properties of graphene-based sponges fabricated using a facile dip coating method. Energy & environmental science 2012, 5, 7908-7912.
Etkin, D.S. Estimating cleanup costs for oil spills. In Proceedings of International oil spill conference; pp. 35-39.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 10 publications | 2 publications in selected types | All 2 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Yoo C, Ko TJ, Hwang JH, Mofid SA, Stoll S, Osorto B, Morillo L, Han SS, Rodriguez KL, Lundin JG, Lee WH. 2D MoS2-polyurethane sponge for solar-to-thermal energy conversion in environmental applications:Crude oil recovery and seawater desalination. Journal of Water Process Engineering 2022;47:102665. |
SV839489 (Final) SU840162 (Final) |
Exit |
Progress and Final Reports:
Original AbstractP3 Phase I:
A Novel 2D MoS2 Sponge Oil-Water Separator (MDSOS) | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.