VOL. 2, NO. 3, December 2022, PP. 31~36
Print ISSN 2777-0168| Online ISSN 2777-0141| DOI prefix: 10.53893 https://journal.gpp.or.id/index.php/ijrvocas/index
31
Utilizing an Oxyhydrogen Reactor to Produce Hydrogen Gas as a New Source of Energy from Textile Effluent
Rusdianasari
1, 2*, Isdaryanto Iskandar
1, 3, Prita Dewi Basuki
1, 31Engineer Profession Program, Atma Jaya Catholic University of Indonesia, Indonesia
2Chemical Engineering Department, Politeknik Negeri Sriwijaya, Indonesia
3Faculty of Engineering, Atma Jaya Catholic University of Indonesia, Indonesia
Email address:
*Corresponding author
To cite this article:
Rusdianasari, Iskandar, I. ., & Basuki, P. D. . (2022). Utilizing an Oxyhydrogen Reactor to Produce Hydrogen Gas as a New Source of Energy from Textile Effluent. International Journal of Research in Vocational Studies (IJRVOCAS), 2(3), 31–36.
https://doi.org/10.53893/ijrvocas.v2i3.149
Received: November 29, 2022; Accepted: December 12, 2022; Published: December 26, 2022
Abstract:
Textile waste can disrupt the environmental equilibrium. One type of textile waste processing is the production of hydrogen gas as a new and sustainable energy source. The water electrolysis method may be used to convert textile waste into hydrogen gas. In this study, hydrogen gas was produced from textile waste in two stages: electroplating waste treatment with an electrocoagulator and then processing textile waste into hydrogen gas using an oxyhydrogen reactor. Various catalysts, including NaOH, KOH, NaCl, and NaHCO3, were used in the process of converting textile waste into hydrogen gas, with a concentration of 0.5 M and an electrolysis period of 5 minutes. The addition of a catalyst is intended to identify the optimal concentration in the conversion of textile waste to hydrogen gas. The optimal KOH catalyst concentration for obtaining hydrogen gas was determined through study and analysis.Keywords:
energy,hydrogen, oxyhydrogen, textile effluent1. Introduction
Energy is inextricably linked to human life. Until now, difficulties in the energy sector have remained a severe concern in a number of nations, particularly in Indonesia, due to the country's continued reliance on fossil energy, specifically 96% (48% petroleum, 18% gas, and 30% coal) [1], [2]. The depletion in fossil energy reserves is inversely related to the high usage of fossil energy. According to data from the Ministry of Energy and Mineral Resources (ESDM), Indonesian fuel oil output was less than 1 million barrels per day in 2010 and 779 thousand barrels per day in 2015.
Continuous use of petroleum will result in a decrease in petroleum production and an increase in pace, eventually leading to an energy crisis [3],[4],[5]. To overcome the problem in these circumstances, a new solution is required.
One of these is the development of Renewable Energy (RE) as an alternative energy source.
An alkaline or acidic electrolyte is utilized as the catalyst [6],[7],[8]. Catalysts included sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium chloride (NaCl) [9][10]. The hydrogen gas rate in this investigation was 2.103 mL/s for the NaOH catalyst, 1.24 mL/s for the KOH catalyst, and 1.859 mL/s for the NaCl catalyst, with each catalyst accounting for 4.76% wt. Sodium bicarbonate (NaHCO3) was utilized as a catalyst in the previous work [11],[12]. The hydrogen gas (H2) rate in this investigation was 1.153 mL/s with a catalyst quantity of 12% wt. In order to create hydrogen gas, clean water is normally utilized as the raw material in the water electrolysis process (H2).
Hydrogen gas is an ecologically friendly energy that is of major significance to many governments, particularly wealthy countries. Many countries expect hydrogen gas to be a more ecologically benign and efficient future fuel. Hydrogen gas may be produced by a variety of techniques, one of which is
simple to implement: electrolysis of water using metal electrodes. Because water can be broken down using electricity, it may be utilized as an energy source to make hydrogen gas. Because the electrolysis process of breaking down water molecules (H2O) is slow, a catalyst is required to speed up the reaction and increase the amount of hydrogen gas generated. Catalyst ions are able to change the stability of water molecules into H+ and OH- ions, which are more easily electrolyzed owing to a drop in activation energy, the catalyst itself works to expedite the process of decomposing water into hydrogen gas and oxygen gas.
Textile effluent, which can be treated into clean water, can be utilized as a supply of water for the electrolysis process. Textile wastewater is produced as a byproduct of industrial operations such as traditional handicraft industries, one of which is the woven fabric business, which includes the songket and jumputan cloth industries. According to previous study, various colors containing metals, such as Pb (Lead) and Cd (Cadmium), are utilized in the textile craft business [13]. If wastewater from the textile sector is not adequately handled, it can upset the environmental equilibrium. To address this, one of them may be utilized to generate New, Renewable Energy (RE). The use of textile wastewater as a source of New and Renewable Energy (RE) begins with the treatment of textile wastewater with an electrocoagulator into clean water. An oxyhydrogen reactor will convert the clean water into hydrogen gas.
In this study, hydrogen gas was produced from textile wastewater in two stages; first, textile wastewater was processed with an electrocoagulator, and subsequently hydrogen gas was produced using an oxyhydrogen reactor.
According to the study [14], the scientists created hydrogen gas from textile wastewater by using catalysts with set concentrations of 0.5 M of sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium chloride (NaCl), and sodium bicarbonate (NaHCO3). The goal of varying the catalysts is to determine which catalyst produces the most hydrogen gas from textile effluent.
2. Research Methods
2.1. Processing of Textile Wastewater into Clean Water Figure 1 depicts how textile effluent is converted into clean water using an electrocoagulator. A 20-liter textile wastewater feed is poured into the reservoir. The electrocoagulator device is switched on to activate the smart sensor and pump. Pump 1 is started to transport the textile waste to the silica sand, activated carbon, and electrocoagulation tanks. Pump 1 is turned off when the electrocoagulation tank is full. The electrode is switched on and the required voltage, 7.5 volts, is established.
Figure 2. Electrocoagulator
The electrocoagulation procedure lasted 30 minutes. After 30 minutes, the electrodes were switched off and the tap on the electrocoagulation tank was opened to collect the electrocoagulation process's effluent. The electrocoagulation wastewater is left to stand until the coagulant settles, after which the clean water and coagulant generated are separated.
The acquired clean water is placed in the first product tank.
Following that, pump 2 is activated to deliver clean water to the Filter Cartridge and Reverse Osmosis (RO), which are subsequently housed in the final product tank.
2.2. Hydrogen Gas Production
The process of producing hydrogen gas is carried out using an oxyhydrogen reactor as shown in Figure 2.
Figure 2. Oxyhydrogen Reactor
Prepared 30 liters of treated wastewater as reactor feed for the five types of catalysts to be utilized. Weigh 0.5 M NaOH, KOH, NaCl, and NaHCO3 catalyst for addition to feed water in 6 liters. Add the weighed catalyst to each of the 6 liters of feed water. A voltage of 12.2 volts is used in the oxyhydrogen reactor. The H2 and O2 gases generated are stored separately, and the gas pressure is monitored during the process of H2 and O2 gas generation. Repeat the procedure stages with the addition of 0.5 M catalysts NaOH, KOH, NaCl, and NaHCO3. A waterproof multimeter PCD 605 was used to assess clean
water products, an ICP-OES was used to examine metals in textile effluent, and an ECOM gas meter was used to measure the quantity of hydrogen and oxygen gas generated.
3. Result and Discussion
3.1. Preliminary Analysis of Textile Wastewater and Processing Products
The textile wastewater utilized in the clean water treatment process is waste from the jumputan cloth business originating from the jumputan cloth craft facility located in Tuan Kentang sub-district, Seberang Ulu District 1 Kertapati Palembang.
The electrocoagulation procedure is used to treat this effluent.
According to the findings of the research, the results are shown in Tables 1 and 2. The table shows that the wastewater treated by electrocoagulation has reduced in terms of color and degree of acidity, but conductivity and TDS have increased. The metal composition of Cd (Cadmium) and Pb (Lead) is rather stable.
Table 1. Textile Wastewater Analysis Results No Parameter Units Results Methods
1 Smell - Odorless Organoleptic
2 Color TCU 32 Spectrophotometry
3 pH - 6,30 SNI 6989.11:2019
4 TDS mg/L 650 Direct Reading
5 Conductivity µS 114,9 Waterproof PCD 605
6 Cd mg/L < 0,0031 ICP-OES
7 Pb mg/L < 0,0045 ICP-OES
Table 2. Results of Analysis of Textile Wastewater After Processing No Parameter Units Results Methods
1 Smell - Odorless Organoleptic
2 Color TCU 7 Spectrophotometry
3 pH - 3,98 SNI 6989.11:2019
4 TDS mg/L 1471 Direct Reading
5 Conductivity µS 272,5 Waterproof PCD 605 6 Cd mg/L < 0,0031 < 0,0031
7 Pb mg/L < 0,0045 ICP-OES
The dye dropped from 32 TCU to 7 TCU in Tables 1 and 2, according to the adsorption process by the hydroxo cationic complex generated due to anode solubility in the electrocoagulation process [15]. The formation of hydroxocationic complex compounds increases with increasing voltage and current, causing existing dyes to form bigger clumps [16]. Following the equation, the dye pollutants will form ligands that bind to the Al2(OH)3 precipitate [17],[18].
Dye-H + Al(OH)3 ↔ Dye-OAl + H2O (1) According to Tables 1 and 2, the degree of acidity (pH) has dropped from 6.38 to 3.84, due to acid reduction at the cathode electrode, which produces H2 gas. Because of the presence of H2 gas, hydroxide ions (H+) bond contaminants in trash to form insoluble and floating compounds [19].
Because the quantity of hydroside ions (H+) grows, the value of the degree of acidity (pH) after electrocoagulation decreases.
The conductivity and TDS values have increased, with conductivity increasing from 114.9 S/cm to 272.5 S/cm and TDS increasing from 650 mg/L to 1471 mg/L due to electrocoagulation. Al3+ ions formed at the anode electrode will bind to OH- ions formed at the cathode electrode, resulting in the formation of a coagulant [20]. Because the Al3+ ions that are generated are still dissolved, the rise in Al3+
ion value will raise the TDS value of the wastewater following the electrocoagulation process. Because the Al3+
ions that are generated are still dissolved, the rise in the Al3+
ion value will raise the TDS value of the wastewater following the electrocoagulation process. The results of research show that increasing the TDS value induces an increase in the conductivity value of the solution following electrocoagulation [21].
The metal content of Cd (Cadmium) and Pb (Lead) did not change since the electrocoagulation method employed just two plates, which was insufficient for metal removal, as well as a short period, i.e. only 30 minutes and a low electric voltage of 7.5 Volts. According to the research, at least three electrodes, a voltage of 12 volts, and a contact period of one hour are required to reduce lead metal levels. The concentration of Pb and Cd metals in waste and after processing is claimed to be relatively low, with Cd metals containing 0.0031 mg/L and Pb metals containing 0.0045 mg/L [22].
Based on the findings of wastewater treatment using the electrocoagulation method, it can be stated that the treated water is acceptable for use as feed in the hydrogen production process since it has reduced in color and increased conductivity values that promote the creation of hydrogen gas.
3.2. Hydrogen Gas Flow Rate Analysis of the Catalyst Used Figure 3 shows the link between the rate of hydrogen gas generation and the kind of catalyst employed, with a catalyst concentration of 0.5 M visible from the flow rate of each catalyst utilized. Figure 3 shows that wastewater may be converted into hydrogen gas without the need of a catalyst since wastewater includes metals that are still transported away after the electrocoagulation treatment process and have a low degree of acidity (pH).
Another study found that the electrolysis process is highly reliant on the pH of the solution; the more acidic or moist a solution is, the faster the electrolysis process happens since the fluid is more electrolyte and has a high conductivity value [23].
The flow rate of hydrogen gas obtained without the use of a catalyst is relatively low, precisely 0.1185 mL/s, therefore collecting it takes a long time. A catalyst is required to obtain a large number of outcomes in a short period of time. Figure 3 shows that of the four catalysts, the KOH catalyst produces the most hydrogen gas at a gas flow rate of 5.8355 mL/s, followed by the NaOH catalyst at 4.2052 mL/s, the NaCl catalyst at 3.5928 mL/s, and the NaHCO3 catalyst at 1.5062 mL/s.
Figure 3. Use of a Catalyst for the Rate of Hydrogen Gas Produced
The KOH catalyst has a higher flow rate of hydrogen gas than the NaOH catalyst, which is also a strong base, because the amount of catalyst used at the time of research was the same solution concentration unit, namely 0.5 M, so to get a KOH concentration of 0.5 M required as much as 168.3168 gr while the NaOH catalyst required as much as 119.991 gr. This difference in catalyst quantity is what causes the KOH catalyst to have a faster rate of hydrogen gas generation than the NaOH catalyst because the more wet catalyst added, the more ions are generated in the solution, making the solution more electrolyte.
The KOH catalyst is a strong base catalyst, whereas the NaHCO3 catalyst is a weak base. When NaHCO3 catalyst is dissolved in water, CO2 gas is produced, which dissolves combined to generate Na+ and OH- ions. Because the NaHCO3
solution is a weak electrolyte because it is not entirely ionized in water, the generation of CO2 gas slows down the electrolysis process, causing the NaHCO3 catalyst to have a lower hydrogen gas rate compared to other catalysts.
NaCl catalyst is a strong electrolyte salt that totally ionizes into Na+ and Cl- when dissolved in water, it has a greater flow rate of hydrogen gas than the NaHCO3 catalyst, which is a base catalyst. The NaCl catalyst has a drawback in its application since the solution will generate a green precipitate during the electrolysis process due to the presence of Na precipitate and Cl2 gas formed during the electrolysis process. The reaction [24] results in the production of Cl2 gas.
2H2O + 3Na++ 3Pb2+ + Fe + Mg + Cr + 2Cl- → 2H2 + O2 + 3Na + 3Pb + Fe2+ +Mg2+ + Cr+3 + Cl2 (2) This creation event does not occur in alkaline catalysts, where the water utilized after electrolysis remains clear. Based on the results, the optimum catalyst for creating hydrogen gas from wastewater with a catalyst concentration of 0.5 M is KOH catalyst with a gas production flow rate of 5.8355 mL/s.
3.3. Analysis of the Amount of Hydrogen Gas for the Catalyst Used
Analysis of hydrogen gas produced by production was carried out using a gas meter (ECOM). A gas meter is a tool used to measure exhaust emissions and analyze soot from stationary sources. The gas parameters tested were O2, CO, NO, NOx, NO2, SO2, H2 and CO2.
In this study, the gas parameters measured and taken were hydrogen gas and oxygen. The H2 parameter is used to determine the amount of hydrogen gas produced while O2 is used to determine the purity of the gas, because the less amount of oxygen gas that is formed in the H2 tube, the purer the hydrogen gas obtained. Graph of the relationship between the formed H2 gas and the catalyst used can be made as shown in Figure 4.
Based on Figure 4, it can be seen that hydrogen gas produced with a catalyst has a higher H2 content than without using a catalyst. From Figure 4 it can be seen that the amount of H2 gas produced without a catalyst is 122 mg/m3 while using a catalyst, which is for NaOH 537 mg/m3; KOH 558 mg/m3; NaCl 472 mg/m3; and NaHCO3 462 mg/m3. Based on these results, it can be seen that the KOH catalyst produced higher H2 of 558 mg/m3. The results obtained show that the use of a catalyst also affects the amount of H2 produced in addition to affecting the rate of production.
Figure 4. Use of a Catalyst for the Amount of H2 Gas Produced
Graph of the relationship between the O2 gas content and the catalyst used can also be made as shown in Figure 5. From Figure 5 it can be seen that hydrogen gas produced with a catalyst has a lower O2 content than without using a catalyst.
From Figure 5 it can be seen that the O2 gas content formed for each catalyst is for NaOH 14.49%; KOH 13.49%; NaCl 16.8%; and NaHCO3 17.68%. Based on these results it can be seen that the KOH catalyst has a fairly high purity of hydrogen gas (H2) because it only contains a small amount of oxygen, namely 13.49% compared to other catalysts.
H2 Gas (mg/m3)
H2O
H2O
Figure 5. Use of a Catalyst for the Amount of O2 Gas Produced
The results obtained also show that the catalyst affects the purity of the hydrogen gas formed. Based on the gas analysis results, it can be seen that emission gases were detected such as CO, NO, NOx, NO2, SO2, and CO2. These gases are detected due to outside air entering the gas measuring device during the gas analysis. The entry of air is caused by a lack of vacuum in the connecting hose between the sample and the sampling pump on the device.
4. Conclusion
Based on the study and analysis done on the production of hydrogen gas from textile wastewater, it can be determined that the clean water obtained from the electrocoagulation technique of processing textile wastewater can be claimed to be practical to be utilized as feed in the process of manufacturing hydrogen gas. KOH catalyst with a gas production flow rate of 5.8355 mL/s and a quantity of H2 of 558 mg/m3 and O2 of 13.49% by volume is the best catalyst for creating hydrogen gas (H2) from wastewater with a catalyst concentration of 0.5 M.
References
[1] Rusdianasari, Meidinariasty, A., & Purnamasari, I. (2015).
Level Decreasing Kinetic Model of Heavy Metal Contents in the Coal Stockpile Wastewater with Electrocoagulation.
International Journal on Advanced Science Engineering Information Technology, 5(6), 387-391.
doi:10.18517/ijaseit.5.6.593
[2] Meidinariasty, A., Rusdianasari, Bow, Y., Rusnadi, I., & Fuady, A.L. (2019). Treatment of Leachate from Garbage using Electrocoagulation Type MP-P (MonoPolar-Paralel) Methode.
Journal of Physic: Conference Series 1167(012054), doi:10.1088/1742-6596/1167/1/012054
[3] Rusdianasari, Taqwa, A., Syakdani, A., & Jaksen. (2017).
Treatment of Landfill Leachate by Electrocoagulation using Aluminum Electrode. Matec Web of Conference 101 (EDP Science. doi: 10.1051/ matecconf/201 710102010
[4] Irtas, D., Bow, Y., & Rusdianasari. (2021). The Effect of Electric Current on the Production of Brown’s using Hydrogen Fuel Generator with Seawater Electrolyte, IOP Conference Series: Earth and Environmental Science, Volume 709, 7th International Conference on Sustainable. doi: 10.1088/1755- 1315/709/1/012001
[5] Rusdianasari, Bow, Y., & Dewi, T. (2019). HHO Gas Generation in Hydrogen Generator using Electrolysis. IOP Conference Series: Earth and Environmental Science 258(012007). doi:10.1088/1755-1315/258/1/012007
[6] Iswandari, D., Mahenri, I., Bow, Y., Syakdani, Adi., & Junaidi, R. (2022). Effect of Concentration of NaOH and H2SO4 Catalysts on Hydrogen Gas Production Efficiency.
International Journal of Research in Vocational Studies, 1(4), 22-25. doi: prefix: 10.53893
[7] Rusdianasari, Taqwa, A., Jaksen, & Syakdani, A. (2017).
Treatment Optimization of Electrocoagulation in Purifying Palm Oil Mill Effluents (POMEs). Journal of Engineering and Technological Science 49(5). 604-616 doi:
https://doi.org/10.5614/j.eng.technol.sci.2017.49.5.4
[8] Chantaraporn, P., Pisut, S., & Chinnaot, M. (2010). Hydrogen Recovery from the Electrocoagulation Treatment of Dye- containing Wastewater. International Journal of Hydrogen Energy, 35, 10934-10943. doi:10.1016/j.ijhydene.2010.06.100.
[9] Rusdianasari, Taqwa, A., Jaksen, & Wijarnako, Y. (2019).
Effectiveness of Electrocoagulation Method in Processing Integrated Wastewater using Aluminum and StainlessSteel Electrodes. Journal of Physic: Conference Series 1167(012040).
doi:10.1088/1742-6596/1167/1/012040
[10] Budiman, A., Yerizam, M., &Bow, Y. (2022). Design ofDyr Cell HHO Generator using NaCl Solution for Hydrogen Production. Indonesian Journal of Fundamental and Applied Chemistry, 7(1), 8-15. doi: 10.24845/ijfac.v7.i1.8
[11] Weger, L., A. Abánades, A., & T. Butler, T. (2017). Methane cracking as a bridge technology to the hydrogen economy. Int.
J. Hydrogen Energy, 42(1), 720–731. doi:
10.1016/j.ijhydene.2016.11.029.
[12] Rusdianasari, Taqwa, A., Jaksen, & Wijarnako. (2019). Smart Sensor for Monitoring Integrated Wastewater. IOP Conference Series: Earth and Environmental Science 347(012061). DOI 10.1088/1755-1315/347/1/012061
[13] Bow, Y., Rusdianasari, Meidinariasty, A. (2023). Production of Hydrogen from Seawater as Green Energy using Hydrogen Fuel Generator. Asian Journal of Applied Research for Community Development and Empowerment doi:
https://doi.org/10.29165/ajarcde.v7i1.214
[14] Rusdianasari, Syakdani, A., Bow, Y., Dewi, T., Shodiq, A.J., &
Arita, S. (2020). Combination of Electrocoagulation and Aeration Process by Addition NaCl for Leachate Treatment.
International Journal on Advanced Science Engineering Information Technology, 10(1), 400-406.
DOI:10.18517/ijaseit.10.1.11012
[15] Geln, D.O.N., Corey, D.C., David, E.B., & Daniel, V.E. (2016).
Hydrogen Production with a Simple and Scalable Membraneless Electrolyzer. Journal of the Electrochemical Society, 163(11), F3012-F3019. 10.1149/2.0021611jes.
[16] Rusdianasari, Taufik, M., Bow, Y., & Fitria, M.S. (2020).
Application of Nanosilica from Rice Husk Ash as Iron Metal (Fe) Adsorbent in Textile Wastewater. Indonesian Journal of Fundamental and Applied Chemistry, 5(1), 7-12 doi:
10.24845/ijfac.v5.i1.7.
[17] Konrad, M. (2014). Hydrogen Production with Seawater Electrolysis using Nowergian Offshore Wind Energy Potentials.
Int J Energy Environ Eng, 5(104). doi: 10.1007/s40095-014- 0104-6
[18] Bow, Y., Sari, A.P., Harliyani, A.D., Saputra, B., & Budiman, R.
(2020). Produksi Gas Hidrogen Ditinjau dari pengaruh Duplex Stainless Steel terhadap variasi Konsnetrasi Katalis dan Jenis Air yang Dilengkapi Arestor. Kinetika, 11(3), 46-52.
[19] Tuller, H.L. (2017). Solar to fuels conversion technologies: A perspective. Mater. Renew. Sustain. Energy, 6(1), 1–16. doi:
10.1007/s40243-017-0088-2.
[20] Jannah, Z. & Susilo, S.H. (2021). Design of HHO Generators as Producer of Water Fuel (HHO Product Analysis Based on Electric Current and Catalyst. IOP Conf. Series: Materials Science and Engineering, 1073(012034). doi:10.1088/1757- 899X/1073/1/012034
[21] Susilo, S.H., Jannah, Z., Kasijanto. & Gumono. (2020). Effect of Electrodes, Electric Currents, and NaHCO3Concentration against HHO Pressure Generator. International Journal of Engineering and Science, 10(4), 4-9.
[22] Rusdianasari, Bow, Y., Dewi, Tresna., & Risma, Pola. (2019).
Hydrogen Gas Production using Water lectrolyzer as Hydrogen Power, 2019 International Conference on Electrical Engineering and Computer Science (ICECOS), IEEE. doi:
10.1109/ICECOS47637.2019.8984438
[23] Sapountzi, J. M., Gracia, K. J., Weststrate, Fredriksson, & Hans.
N. (2017). Electrocatalysts for the generation of hydrogen, oxygen and synthesis gas. Prog. Energy Combust. Sci., 58, 1–
35, 2017. doi: 10.1016/j.pecs.2016.09.001.
[24] Shiva, S.K., & Himabindu, V. (2019). Hydrogen production by PEM water electrolysis – A Review. Mater. Sci. Energy Technol., 2(3), 442–454. doi: 10.1016/j.mset.2019.03.002.
[25] Rusdianasari, Bow, Y., Dewi, T., Taqwa, T., & Prasetyani, L.
(2019). Effect of Sodium Chloride Solution Concentration on Hydrogen Gas Production in Water Electrolyzer Prototype.
2019 International Conference on Technologies and Policies in Electric Power & Energy, IEEE, doi:
10.1109/IEEECONF48524.2019.9102508
[26] Yee, C. H. Raymond, L. P., Tan, M. M, & Tang, N.T. (2019).
Large-scale structure formation in ionic solution and its role in electrolysis and conductivity. PLoS One, 14(3)3, 1–17. doi:
10.1371/journal.pone.0213697.
