Environmentally sustainable cellulose fibers based aerogel photothermal material for solar driven clean water

|d-d VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN HOANG GIANG ENVIRONMENTALLY SUSTAINABLE CELLULOSE FIBERS-BASED AEROGEL PHOTOTHERMAL MATERIAL FOR SOLAR-DRIVEN CLEAN WATER MASTER’S THESIS VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN HOANG GIANG ENVIRONMENTALLY SUSTAINABLE CELLULOSE FIBERS-BASED AEROGEL PHOTOTHERMAL MATERIAL FOR SOLAR-DRIVEN CLEAN WATER MAJOR: NANOTECHNOLOGY CODE: 8440140.11QTD RESEARCH SUPERVISOR: Dr PHAM TIEN THANH Hanoi, 2022 COMMITMENT I have read and understood the plagiarism violations I pledge with personal honor that the research is my own and does not violate the Regulation on prevention of plagiarism in academic and scientific research activities at VNU Vietnam Japan University (Issued together with Decision No 700/QĐ-ĐHVN dated 30/9/2021 by the Reactor of Vietnam Japan University Author of the thesis Nguyễn Hoàng Giang ACKNOWLEDGEMENTS Firstly, I would like to express my sincere gratitude to Dr Pham Tien Thanh, my supervisors at Vietnam Japan University, for his enthusiasm, support, and patient guidance throughout the implementation of my research for master thesis I'd want to take this opportunity to thank Assoc Prof Dr Pham Xuan Nui from Hanoi University of Mining and Geology for his useful support and recommendation during my research His suggestions on the purification of cellulose from sugarcane bagasse had been very useful for my research I would like to express my gratitude to all lab-mates from both MNT Lab and MEE Lab for their necessary assistance I really enjoy my research works and the moments we had together Last but not least, I really want to thank to MNT’s professors, lecturers, staffs for their support me during the internship period Without them, I could not have enough knowledge and experience to research and study in here I want to express my gratitude to my mother, father, brother, and friends, who have always been there for me and have always supported and encouraged me throughout my life Nguyen Hoang Giang Hanoi, 2022 TABLE OF CONTENTS LIST OF TABLES i LIST OF FIGURES .ii LIST OF ABBREVIATIONS iv CHAPTER 1: INTRODUCTION OF SOLAR STEAM GENERATION 1.1 The importance of converting seawater into freshwater 1.2 Desalination of seawater 1.3 Solar steam generation (SSG) 1.4 Types of photothermal materials 1.4.1 Metallic nanoparticles 1.4.2 Metal Oxides \1.4.3 Biomass based photothermal materials 1.4.3 Aerogel based photothermal materials 1.5 Justify the selection of research material and method 1.6 Cellulose based aerogel fabrication procedure 1.7 Purpose of thesis 10 CHAPTER 2: EXPERIMENTS 11 2.1 Fabrication of photothermal materials 11 2.1.1 Chemicals 11 2.1.2 Preparation of natural porous materials 11 2.2 Characterization of photothermal materials 14 2.3 Investigate the photothermal material’s performance 15 2.3.1 Investigation of the material thermal behavior under laboratory condition 15 2.3.2 Investigation of the material’s performance under laboratory condition 16 2.3.3 Investigation of the material’s performance under real condition 17 CHAPTER 3: RESULTS AND DISCUSSIONS 18 3.1 Explanation on the fabrication of aerogels from ground sugarcane bagasse 18 3.1.1 Extraction of cellulose from ground sugarcane bagasse 19 3.1.2 Preparation of white cellulose-based aerogel from extracted cellulose 20 3.1.3 Preparation of black cellulose-based aerogel from extracted cellulose 21 3.2 The surface morphologies of photothermal materials 23 3.2.1 SEM images of the photothermal material 23 3.2.2 Brunauer-Emmett-Teller (BET) analysis results 24 3.2.3 X-ray diffraction and EDS analysis results 25 3.3 Surface structure of the photothermal material 26 3.2.1 EDS analysis results 26 3.2.2 FT-IR spectra 27 3.2.3 Wetting behavior measurement 28 3.3 Mechanical properties of the aerogels 29 3.4 Thermal conductivity of the aerogels 31 3.5 Evaporation performance of the aerogel 31 3.5.1 Thermal behavior and FT-IR of the aerogel 31 3.5.2 Evaporation performance of the aerogel in the experiment condition 32 3.5.3 Evaluation the solar energy evaporation efficiency of the black aerogel 34 3.5.4 Evaluation the structural stability of the black aerogel 36 3.5.5 Evaluation performance of the aerogel in real condition 38 CONCLUSION 40 REFERENCES 43 LIST OF TABLES Table 2.1 Composition of white and black aerogel samples 14 Table 2.2 List of equipment used for the material characterization .14 Table 3.1 EDS analysis results of White aerogel and Black aerogel 27 Table 3.2 Concentration of substances in the final suspension of the aerogel samples .29 Table 4.1 Comparison on the specifications and performance of the Cellulose based aerogel in this thesis and other type of photothermal materials .41 i LIST OF FIGURES Figure 1.1 Projected water stress in 2040 Figure 1.2 a) Severe drought in the Mekong delta, b) Map of saline invasion of the Mekong delta Figure 1.3 Technological status of renewable energy desalination technologies Figure 1.4 Working principle of Solar steam generator Figure 1.5 Tungsten oxides material in a stimulation experiment Figure 1.6 Photothermal material based on lotus seed pods Figure 1.7 Phase diagram of water, illustrate the freeze-drying process Figure 1.8 Image of sugarcane bagasse Figure 2.1 Fabrication process of cellulose – based aerogel (including white and black aerogel) 12 Figure 2.2 a) White cellulose-based aerogel, b) black cellulose-based aerogel 13 Figure 2.4 Setup of the experiment to measure thermal behavior of the aerogels 15 Figure 2.6 a) Working principle of the evaporation device, b) The evaporation device under natural sunlight, c) dimension of the inner sample container, d) dimension of the outer compartment 17 Figure 3.1 (a) Ground sugarcane bagasse, (b) Sugarcane bagasse during the treatment with Ethanol:H2O 1:1 solution, (c) Sugarcane bagasse during the treatment with NaOH solution (d) Sugarcane bagasse during the treatment with NaOH:NaClO solution, (e) Extracted cellulose in a vacuum filter, (f) Cellulose suspension, left overnight 19 Figure 3.2 (a) Cellulose suspension, (b) PVA solution, (c) Mixture of distilled water, cellulose, PVA in the ultrasonic device (d) Final suspension of cellulose in PVA solution, (e) A piece of white aerogel (f) A piece of white aerogel, placed on top of a leaf 20 Figure 3.3 Crosslinking between PVA and cellulose in the white aerogel 20 Figure 3.4 (a) Cellulose suspension in Tannic acid solution, (b) PVA + FeCl3 solution, (c) Mixture of distilled water, cellulose, PVA, Tannic acid, FeCl3 in the ultrasonic device, (d) Final suspension containing cellulose PVA, Tannic acid, FeCl3, (e) A piece of black aerogel, (f) Aggregation of cellulose microfibrils in the suspension when the concentration of tannic acid was 10 mg/ml 21 Figure 3.5 (a) Crosslinking between PVA, tannic acid and cellulose in black aerogel (b) Formation of complexes between tannic acid and Fe3+ 22 Figure 3.6 SEM images of (a) aerogel’s cross section (bar: 200µm), (b) aerogel’s cross section (bar: 100µm), (c) SEM images of aerogel’s cross section (bar: 50 µm), (d) aerogel’s surface (bar: 200µm), (e) aerogel’s surface (bar: 100µm), (f) SEM images of aerogel’s cross section (bar: 50µm) 23 Figure 3.7 BET Isotherm of the aerogels 24 ii Figure 3.8 (a) XRD spectra of ground sugarcane bagasse and extracted cellulose, (b) XRD spectra of extracted cellulose and white aerogel, (c) XRD spectra of white aerogel and black aerogel 25 Figure 3.9 a) EDS spectrum of White aerogel (CBA1), (b) EDS spectrum of black aerogel (CBA2) 26 Figure 3.10 FT-IR spectra of Ground sugarcane bagasse, extracted cellulose, White aerogel and Black aerogel in the wavenumber range of 500 – 4000 cm-1 27 Figure 3.11 Wetting behavior measurement of the aerogel 28 Figure 3.12 Tensile and compressive strength testing of the aerogels 29 Figure 3.13 Crosslinking between tannic acid, PVA and cellulose 30 Figure 3.14 (a) UV-VIS-IR spectra of the white and black aerogel samples and (b) the maximum temperature of white and black aerogel under sun illumination 31 Figure 3.15 Mass change of the seawater, white aerogel, black aerogel in the solar steam generator under sun illumination 32 Figure 3.16 (a) Surface temperature change of white aerogel and black aerogel in the evaporation experiment, (b) IR images, indicating the temperature change of black aerogel during the evaporation experiment (c) IR images, indicating the temperature change of white aerogel during the evaporation experiment 33 Figure 3.17 a) Temperature variation of black aerogel and the bulk water in the same Solar steam generator b) IR image indicate the material surface temperature and bulk water monitoring areas 34 Figure 3.18 Evaporation rates of the blank seawater, white aerogel and dark aerogel Error! Bookmark not defined Figure 3.19 a) Black aerogel (CBA3)’s rate of evaporation after 50 evaporation cycles, b) Physical appearance of the CBA3 samples after 11 days of exposure to seawater 36 Figure 3.20 a) Self-cleaning mechanism of the aerogel b) Self-cleaning performance of the Black aerogel (CBA3) 37 Figure 3.21 (a) Real water desalination device during the experiment, (b) Parameters: solar flux, temperature, humidity variation on Day from 08:00 – 18:00 (c) Parameters: solar flux, temperature, humidity variation on Day from 08:00 – 18:00, (d) Performance of the desalination device 38 iii LIST OF ABBREVIATIONS CBA: Cellulose-based aerogel EDS: Energy Disperse X-Ray Spectroscopy FT-IR: Fourier-Transform Infrared Spectroscopy PVA: Polyvinyl alcohol RO: Reverse Osmosis SEM: Scanning Electron Microscope SSG: Solar steam generation UV-Vis-nIR: Ultraviolet-Visible-Near Infrared iv 3.4 Thermal conductivity of the aerogels The thermal conductivity of the material were measured by THB-500 Linseis (Germany) equipment, using Transient Hot Bridge method The measured temperature of the aerogel in dry and wet state were 0.084 W.m-1.K-1 0.137 W.m-1.K-1 respectively Both of the values are much lower than that of water (0.6 W.m-1.K-1) [21] The aerogel’s low thermal conductivity could be attributed to its porosity of more than 90%, and the enclosed thermal insulating chambers in the aerogel that reduce the aerogel’s thermal conductivity The thermal conductivity of aerogels in wet state was higher than that in dry state because in the wet state, water with higher thermal conductivity occupied the interconnected pore structures of the aerogel To conclude, the aerogels have low thermal conductivity, ensuring good heat localization and heat loss minimization for the aerogel 3.5 Evaporation performance of the aerogel 3.5.1 Thermal behavior and FT-IR of the aerogel (a) (b) Figure 3.14 (a) UV-VIS-IR spectra of the white and black aerogel samples and (b) the maximum temperature of white and black aerogel under sun illumination UV-VIS-IR spectra were taken for the aerogel samples to determine the sample’s light absorption ability, an important factor governing the material’s solar energy conversion efficiency Fig 3.14(a) shows the absorption spectra of the CBA2 and CBA3 (black aerogel) samples and of CBA1 (white aerogel) The average absorption of the white aerogel was approximately 11 % in the wavelength range of 300 – 1300 nm and approximately 30% in the range of 1300 – 2500 nm Meanwhile, the average absorptions 31 of both black aerogel samples were about 96% in the wavelength range of 300 – 800 nm and 1400 – 2500 nm, and about 80% in the wavelength range of 800 – 1400 nm The increased in absorption of the black aerogel could be attributed to the following factors: (1) the formation of complexes between Tannic acid and Fe3+, (2) ligand to metal charge transfer phenomenon in the above-mentioned complexes and (3) the roughness and porosity of aerogel’s surface structure that capture sunlight via multiple reflection Thus, the UV-VIS-IR spectra confirmed that the aerogel have high light absorption ability Figure 3.14(b) show the increase of temperature of CBA1 and CBA2 under simulated illumination with a radiation power density of kW m-2 The surface temperature of CBA1 (black aerogel) stabilized at around 35 °C while that of the CBA2(white sample) stabilized at around 70 °C The temperature increase had proved the good photothermal conversion properties of the black aerogel From the above characterization results, it could be concluded that the black aerogel is suitable for application in Solar steam generator thanks to its good light absorption ability 3.5.2 Evaporation performance of the aerogel in the experiment condition The evaporation performance of the aerogels was conducted under Oriel® Sol1ATM solar stimulator in the experiment setup mentioned in Section 2.3.2 of the Thesis The experiment was conducted on all the aerogel samples (CBA1, CBA2 and CBA3) for hour During the experiment, the mass changes was recorded by an electrical balance Figure 3.15 Mass change of the seawater, white aerogel, black aerogel in the solar steam generator under sun illumination 32 Figure 3.15 shows the mass change of the solar steam generator during the evaporation experiment under solar stimulator The rate of evaporation of the white aerogel was 0.89 kgm-2h-1 while the highest rate of evaporation of black aerogel (CBA3) samples was 1.76 kgm-2h-1 All the rates were higher than the rate of evaporation of bulk-water under the same condition (0.42 kgm-2h-1) The increase of water evaporation rate compared to that of bulk water are because of photothermal material’s heat localization Due to the low thermal conductivity of photothermal material, light energy is usually retained as heat around the photothermal material’s surface As a result, heat is concentrated to evaporate a small amount of water instead of dispersing to heat the bulk water, increasing the rate of evaporation [22] In addition to heat localization, increase in light absorption ability is responsible for the increase in the rate of evaporation in the black aerogel samples (CBA2 and CBA3) (a) (b) (c) Figure 3.16 (a) Surface temperature change of white aerogel and black aerogel in the evaporation experiment, (b) IR images, indicating the temperature change of black aerogel during the evaporation experiment (c) IR images, indicating the temperature change of white aerogel during the evaporation experiment 33 (a) (b) Figure 3.17 a) Temperature variation of black aerogel and the bulk water in the same Solar steam generator b) IR image indicate the material surface temperature and bulk water monitoring areas The contribution of heat localization and light absorption were confirmed in the graph in Figure 3.16 and Figure 3.17 As shown in Figure 3.11, the surface temperature of black aerogel stabilized at around 45°C while that of the white aerogel only stabilized at about 34 °C, indicated that the black aerogel has higher light absorption ability Because of heat localization phenomenon, the surface temperature of photothermal material always higher than that of the bulk water in the same solar steam generator (Figure 3.17) 3.5.3 Evaluation the solar energy evaporation efficiency of the black aerogel Figure 3.18 Evaporation rates of the blank seawater, white aerogel and dark aerogel To determine the material’s solar energy evaporation efficiency, the water evaporation enthalpy in the photothermal material’s surface was determined Dark evaporation 34 experimented was conducted to determine the evaporation enthalpy of seawater in the black aerogel (CBA3)’s surface In the experiment, the photothermal materials were put in the same Solar steam generator, used in the evaporation experiment under experiment condition (Section 2.3.3) The aerogel samples (CBA1), black aerogel sample (CBA3) were put in three 100 ml beakers of the same size with a diameter of 42 mm The diameter and thickness of both black and white aerogel samples were 42 mm and 14 mm respectively The dark evaporation experiment was conducted three times for 60 minutes each at a temperature of 25◦C and pressure of atm Under the dark condition, the photothermal material still absorb heat from the surrounding environment for water evaporation, while the influence of light intensity to the evaporation rate is removed Under dark evaporation, water evaporation enthalpy – the amount of energy needed to transform a quantity of water to vapor, governs the rate of evaporation Figure 3.13(a) shows that the evaporation rates of black seawater, white aerogel (CBA1) and dark aerogel (CBA3) were 0.078 kg m-2 h-1, 0.13 kg m-2 h-1 and 0.15 kg m-2 h-1 respectively The dark evaporation rate of both the white and black aerogel were similar, the different between them could be attributed to measurement uncertainty The rate was about 1.75 times greater than that of blank seawater As the material’s light absorption ability does not influence the rate of evaporation, the rate of dark evaporation depends only on the material interior’s water evaporation enthalpy The water evaporation enthalpy of the SSG using the photothermal material lower than that of bulk water because its surface contains numerous hydrophilic -OH groups from cellulose, PVA, polyphenol in tannic acid Water could evaporate as single molecules or in clusters of a few to 10 molecules Evaporating as clusters, water could evaporate with a small enthalpy change [33] The 3D interconnected pore structure forming a molecular with numerous -OH groups on its surface could form hydrogen bonding with water molecules, allow water to evaporate in group of a few to 10 molecules [23] Therefore, the aerogel’s evaporation enthalpy is reduced The evaporation enthalpy of the CBA3 material was calculated by the formula [23]: 𝛥𝐻0 𝑚0 = 𝛥𝐻1 𝑚1 where: 𝛥𝐻0 is the evaporation enthalpy of the bulk water = 2450 J/g; 𝑚0 is the dark evaporation rate of bulk water = 0.078 kgm-2h-1; 𝑚1 is the dark evaporation rate of 35 CBA3 sample = 0.15 kgm-2h-2; and 𝛥𝐻1 is the evaporation enthalpy of the CBA3 sample Using the formula, we found that 𝛥𝐻1 = 1274𝐽/𝑔 From the calculated evaporation enthalpy, the Solar energy conversion efficiency of the black aerogel could be calculated using the formula [23]: 𝑒𝑒𝑞 = ∆𝑚 ℎ𝐿𝑉 𝐼 𝑒𝑒𝑞 : is the Solar energy conversion efficiency of the black aerogel; ∆𝑚 : is water evaporation rate of the black aerogel; ℎ𝐿𝑉 : is the evaporation enthalpy of water in the material and 𝐼: is the received optical power density Using the formula, we found that 𝑒𝑒𝑞 = 66.71% The Solar conversion was quite low as evaporation performance of the black aerogel was affected by heat loss in the SSG system including through conduction of heat from the black aerogel to the bulk water, heat loss through radiation to the surrounding environment, heat loss through reflection [24] The increase in the bulk water temperature during the experiment (Figure 3.11a) indicated parts of heat was loss through conduction to the bulk-water However, despite of the material’s low Solar energy conversion efficiency, the reduction of evaporation enthalpy helped to maintain a high evaporation rate for the material [23] 3.5.4 Evaluation the structural stability of the black aerogel a) Evaluation of the black aerogel evaporation over time (a) (b) Figure 3.19 a) Black aerogel (CBA3)’s rate of evaporation after 50 evaporation cycles, b) Physical appearance of the CBA3 samples after 11 days of exposure to seawater 36 Figure 3.19a shows the change in rate of evaporation of the CBA material after cycles of evaporation After 50 cycles of evaporation in the same Solar steam generator, the material retained a good rate of evaporation, only decreased slightly from 1.76 kgm -2h1 to about 1.68 kg m-2 h-1 The observation illustrated that the material has good structural stability Figure 3.14(b) indicated that the piece of black aerogel (CBA3 sample) retains its structural stability, thickness for more than 11 days of exposure to seawater with no sign of deterioration detected on the material’s surface In addition, its thickness and shape remain the same The structural stability of the aerogel will be tested for longer period in the same testing condition The structural stability of the material might be contributed by the crosslinking between tannic acid, PVA and cellulose b) Evaluation of the black aerogel’s self-cleaning properties (a) (b) Figure 3.20 a) Self-cleaning mechanism of the aerogel b) Self-cleaning performance of the Black aerogel (CBA3) Figure 3.20a illustrate the self-cleaning mechanism of the photothermal material in a Solar steam generator During daytime, tiny salt crystals might be formed inside the photothermal material, blocking the water transportation pathway thus reducing the material’s performance over time During nighttime, as the rate of evaporation slows down, seawater circulates through the material, dissolving the tiny salt crystals, formed during the daytime [1] To test the self-clean properties, about gram of salt was sprayed on top of the photothermal material piece, placed in a solar steam generator, similar to that used in the evaporation experiment The dissolution of salt on the material’s surface was monitored As shown in Figure 3.15 b, salt was gradually dissolved before completely dissolved in 75 minutes The experiment illustrated that the black aerogel material good self-cleaning properties The material could clean salt on its without 37 external interference Thanks to the self-cleaning ability, the material could maintain its evaporation performance over time 3.5.5 Evaluation performance of the aerogel in real condition (a) (b) (c) (d) Figure 3.21 (a) Real water desalination device during the experiment, (b) Parameters: solar flux, temperature, humidity variation on Day from 08:00 – 18:00 (c) Parameters: solar flux, temperature, humidity variation on Day from 08:00 – 18:00, (d) Performance of the desalination device To assess the evaporation performance of the black aerogel, The experiment setup and equipment design was presented in Section 2.3.3 of Chapter The experiment was conducted from 08:00 – 18:00 for four consecutive days The average temperature was from 30 – 35 °C The humidity was from 44 – 70% The amount of water collected in Day 1, 2, 3, were 4.91, 5.98, 3.14 and 4.86 kg/m2 respectively The water will be analyzed for ionic concentrations in near future The amount of water collected in Day is slightly greater than that of the two other days because the average Solar flux in the Day (0.86 k W m-2) was higher than that of Day 1(0.64 kW m-2) and Day (0.53 kW m-2) The rates of evaporation in the real condition of the black aerogel was lower than that in the experiment condition because of the following reasons: (1) sunlight intensity 38 attenuation, caused by the glass (2) not all the evaporated steam is condensed into water (3) outdoor conditions (e.g solar flux, humidity and temperature) vary constantly (as shown in Fig 3.21(b-c)) (4) The solar flux in real condition is always equal to or less than that in experiment condition However, the amount of water, generated by the SSG system in real condition is enough to meet the daily water need of a 3-member family The material possesses an enormous potential in desalination applications thanks to its low cost, good evaporation performance, and simplicity in the design 39 CONCLUSION Cellulose based aerogel (CBA) from sugarcane bagasse has been successfully fabricated, using other ingredients: Tannic acid, FeCl3 and PVA Thanks to the 3D porous structure and presence of numerous -OH hydrophilic groups, the material has a 3D porous structure which is good for water transportation ability Thanks to the high porosity and low density, the material has low thermal conductivity The material’s mechanical properties are comparable to other type of published aerogel, the mechanical properties could be improved by adding a sufficient amount of Tannic acid to the final suspension during the fabrication procedure Regarding evaporation performance, CBA material based SSG system exhibited a maximum evaporation rate of 1.75 kg m-2 h-1 under sun illumination equivalent to that of other published photothermal materials mentioned in the Table 4.1 of the Conclusion Although the Solar energy conversion efficiency of the material was low (66.71%) due to heat loss through conduction, convection and reflection, the lowering of water evaporation enthalpy in the material (to 1274 J/g) help to maintain a high rate of water evaporation The material has good structural stability, it could maintain a good rate of evaporation after 50 cycles of evaporation in the same Solar steam generation, used in the evaporation experiment Its good structural stability could be attributed to the self- cleaning properties and the crosslinking between Tannic acid, cellulose and PVA in the material To summary, the material is suitable for application in solar desalination thanks to properties: good structural stability, low thermal conductivity, good water transportation, helping to maintain good evaporation rate over time The material’s fabrication method could be scaled up to mass produce cellulose-based aerogel from various material for application in Solar desalination 40 Table 4.1 Comparison on the specifications and performance of the Cellulose based aerogel in this thesis and other type of photothermal materials Material Cellulose aerogel Evaporation rate, Evaporation efficiency based 1.76 kg m-2 h-1 66.71% under sun Fabrication method, scalability Simple fabrication, high scalability Carbonized biomass Carbonized 1.44 kg m−2 h−1 Simple bamboo 93.66% under fabrication, sun medium scalability Carbonized 1.51 kg m−2 h−1 Simple sunflower 100.4% under fabrication, sun medium scalability Carbonized corn 1.98 kg m−2 h−1 Simple straw 92.4% under sun fabrication, medium scalability Carbonized pomelo 1.39 kg m−2 h−1 Simple peel 87.5% under sun fabrication, medium scalability −2 −1 Carbonized loofah 1.57 kg m h Low price, fruit 85.9% under sun simple fabrication, medium scalability Metals-loaded biomass Pt/Au/TiO2@wood 90.4% under 10 Complicated carbon sun fabrication, Low evaporation low scalability efficiency Ag@PDA 2.08 kg m-2 h-1 Complicated NPs@wooden 88.8% under sun fabrication, medium scalability 3+ -2 -1 Fe 1.81 kg m h Simple complexes@Cocon 73.2% under sun fabrication, ut husk high scalability TiO2/ Corn straw 2.48 kg m−2 h−1 Simple 68.2% under sun fabrication, small scalability Pd@Bamboo 12.8 kg m−2 h−1 Simple 87% under 10 sun fabrication, small scalability Carbon materials@biomass Durability (hour)* 50 Estimated Reference cost/ m2 of material** Low cost This work 10 Low cost 10 Low cost ~2 USD 20 Low cost 20 Low Cost - High cost 12 High cost 33 ~3.4 USD - Low cost 150 High cost 10 41 Chinese ink enabled 1.6 kg m−2 h−1 wood 74% under sun Simple fabrication, medium scalability Aerogels@RGO@r 2.25 kg m−2 h−1 Complicated ice-straw 88.9% under sun fabrication, medium scalability Carbon 1.72 kg m−2 h−1 Complicated nanofibers@loofah 92.5% under sun fabrication, medium scalability −2 −1 Activated carbon 1.46 kg m h Simple treated wood (AC- 96% under sun fabrication, wood) medium scalability −2 −1 Carbon nanotube 1.76 kg m h Simple coated sunflower 87.5% under sun fabrication, stalks low scalability Biomass based composite Marine biomass 1.4 kg m−2 h−1 Complicated based composite 80% under sun fabrication, aerogel medium scalability Biomass-Derived 1.77 kg m−2 h−1 Simple Hydrogel with under sun fabrication, Tailored medium Topography scalability Zwitterionic 1.73 kg m−2 h−1 Simple Hydrogel@ 91.5% under fabrication, Sunflower stalk pith sun medium scalability Low cost 11 16 Low cost 12 20 Low cost 13 12 Low cost 14 High cost 15 Low cost 16 12 Low cost 17 50 Low cost 18 42 REFERENCES [1] Nguyen, M T (2020) Fabrication of photothermal nature-inspired materials application on highly solar steam generation Master’s thesis, Vietnam National University, Hanoi [2] UNEP, Goal Clean water and sanitation (2022) Retrieved: 15/06/2022 [3] Ahmeda, F, E., Hashaikehb, R & Hilal, H (2019) Solar powered desalination – Technology, energy and future outlook Desalination, 453 (2019) 54–76 https://doi.org/10.1016/j.desal.2018.12.002 [4] Subramani, A., Badruzzaman, M., Oppenheimer, J., & Jacangelo, J G (2011) Energy minimization strategies and renewable energy utilization for desalination: A review Water Research (Vol 45, Issue 5, pp 1907–1920) https://doi.org/10.1016/j.watres.2010.12.032 [5] Subramani, A., & Jacangelo, J G (2015) Emerging desalination technologies for water treatment: A critical review Water Research, (Vol 75, pp 164– 187) https://doi.org/10.1016/j.watres.2015.02.032 [6] Mandal, J., Wang, D., Overvig, A C, …Yang, Y (2017) Scalable, “Dip-and-Dry” Fabrication of a Wide-Angle Plasmonic Selective Absorber for High Efficiency SolarThermal Energy Conversion Advanced Materials, 29(41), 1702156 https://doi.org/10.1002/adma.201702156 [7] Lin, Y., Chen, Z., Fang, L., …Gan, Z (2018) Copper nanoparticles with near-unity, omnidirectional, and broadband optical absorption for highly efficient solar steam generation Nanotechnology, 30(1), 015402 https://doi.org/10.1088/1361-6528/aae678 [8] Beicker, C L L., Amjad, M., Bandarra F, E, P., & Wen, D (2018) Experimental study of photothermal conversion using gold/water and MWCNT/water nanofluids Solar Energy Materials and Solar Cells, 188, 51– 65 https://doi.org/10.1016/j.solmat.2018.08.013 [9] Campos, C., Vasco, D., Angulo, C., … Palza, H (2019) About the relevance of particle shape and graphene oxide on the behavior of direct absorption solar collectors using metal based nanofluids under different radiation intensities Energy Conversion and Management, 181, 247–257 https://doi.org/10.1016/j.enconman.2018.12.007 [10] Kiriarachchi, H D., Awad, F S., Hassan, A A., … ElShall, M S (2018) Plasmonic chemically modified cotton nanocomposite fibers for efficient solar water desalination and wastewater treatment Nanoscale, 10(39), 18531–18539 https://doi.org/10.1039/c8nr05916k [11] Sun, L., Li, Z., Su, R., … Yu, M (2018) Phase‐ Transition Induced Conversion into a Photothermal Material: Quasi‐ Metallic WO 2.9 Nanorods for Solar Water Evaporation and Anticancer Photothermal Therapy Angewandte Chemie International Edition, 57(33), 10666–10671 https://doi.org/10.1002/anie.201806611 [12] Tao, P., Shu, L., Zhang, J., … Deng, T (2018) Silicone oil-based solar-thermal 43 fluids dispersed with PDMS-modified Fe3O4@graphene hybrid nanoparticles Progress in Natural Science: Materials International, 28(5), 554–562 https://doi.org/10.1016/j.pnsc.2018.09.003 [13] Chen, J., Zhou, Y., Li, R., Wang, X., & Chen, G Z (2019) Highly dispersed nickel nanoparticles decorated titanium dioxide nanotube array for enhanced solar light absorption Applied Surface Science, 464, 716–724 https://doi.org/10.1016/j.apsusc.2018.09.091 [14] Vu, T, D (2020) Biometamaterials appication for solar steam generation devices Master’s thesis, Vietnam National University, Hanoi [15] Radotić, K & Mićić M (2016) Methods for Extraction and Purification of Lignin and Cellulose from Plant Tissues, Sample Preparation Techniques for Soil, Plant, and Animal Samples, Researchgate 365-376 DOI:10.1007/978-1- 4939-3185-9 [16] Nguyen, K T (2021) Scalable and flexible photothermal material based on bacterial cellulose for solar steam generation Master’s thesis, Vietnam National University, Hanoi [17] Wu, Z., Sun, H., Xu, Z., … Zhao, Y (2021) Underwater Mechanically Tough, Elastic, Superhydrophilic Cellulose Nanofiber-Based Aerogels for Water-in-Oil Emulsion Separation and Solar Steam Generation ACS Appl Nano Mater https://doi.org/10.1021/acsanm.1c01597 [18] Du, T, T., Son, T, S., Nam, D, D., … Anh, P, N (2020) Green aerogels from rice straw for thermal, acoustic insulation and oil spill cleaning applications Materials Chemistry and Physics, 253 (2020) 123363 https://doi.org/10.1016/j.matchemphys.2020.123363 [19] Nga D, H, N., Viet, T, T., Quang, T, B, M., … Phung, L, K (2020) Recycling of Pineapple Leaf and Cotton Waste Fibers into Heat‑insulating and Flexible Cellulose Aerogel Composites, Journal of Polymers and the Environment https://doi.org/10.1007/s10924-020-01955-w [20] Quoc, T, B., Son, N, T., Duong, H, K., … Hai, D, M (2021) Cellulose-based aerogels from sugarcane bagasse for oil spill-cleaning and heat insulation applications Carbohydrate Polymers, 228 (2021) 115365 https://doi.org/10.1016/j.carbpol.2019.115365 22 Liu, X., Mishra, D, D., Li, Y., Hu, C (2021) Biomass-Derived Carbonaceous Materials with Multichannel Waterways for Solar-Driven Clean Water and Thermoelectric Power Generation ACS Sustainable Chem Eng, (2021), 9, 4571−4582 https://dx.doi.org/10.1021/acssuschemeng.0c09177 [22] Fuzil, N, S., Othman, N, H., Alias, N, H., … Shirazi, M, M, A (2021) A review on photothermal material and its usage in the development of photothermal membrane for sustainable clean water production Desalination, 517 (2021) 115259 https://doi.org/10.1016/j.desal.2021.115259 [23] Thanh P, T., Tuan, N, M., Giang, N, H., … Duc, N, D (2022) Fe(III)-natural polyphenols bilayer coatings on fingered citron as a novel photothermal material for sustainable seawater desalination Desalination 537 (2022) 115873 44 https://doi.org/10.1016/j.desal.2022.115873 [24] Liu, F., Xia, L., Zhang, L., … Yang, R (2021) Sunflower-stalk-based solar-driven evaporator with a confined 2D Water Channel and an enclosed thermal-insulating cellular structure for stable and efficient steam generation ACS Appl Mater Interfaces 13 (46) (2021) 55299–55306 https://pubs.acs.org/doi/pdf/10.1021/acsami.1c20747 [25] WWF Overview of water scarcity (2022) Retreived: 22/06/2022 from https://www.worldwildlife.org/threats/water-scarcity [26] Hùng Võ, (2022) Đồng sông Cửu Long: Xâm nhập mặn mùa khô năm 2022 mức cao Translated: Mekong river delata: Saline invasion during the dry season of 2022 is at a new high Retreived: 22/06/2022 from: : https://www.vietnamplus.vn/dongbang-song-cuu-long-xam-nhap-man-mua-kho-nam-2022-o-muc-cao/773457.vnp [27] American Membrane Technology Association (2022) Water Desalination Processes Retreived: 22/06/2022 from http://www.amtaorg.com/Water_Desalination_Processes.html [28] Cao, S., Jiang, Q., Wu, X., … Singamaneni, S (2019) Advances in Solar Evaporator Materials for Freshwater Generation Journal of Materials Chemistry A doi:10.1039/C9TA06034K [29] Nguyen M T (2020) Fabrication of photothermal nature-inspired materials application on highly solar steam generation Master’s thesis, Vietnam National University, Hanoi [30] Fang, J., Liu, J., Gu, J., … Zhang, D., (2018) Hierarchical Porous Carbonized Lotus Seedpods for Highly Efficient Solar Steam Generation Chem Mater 2018, 30, 6217−6221 DOI: 10.1021/acs.chemmater.8b01702 [31] Sagar, G, S & Babasaheb, C, L., (2018) A Review on Aerogel An Introduction, International Research Journal of Engineering and Technology (IRJET), Volume: 05 Issue: 03 |, 4098 – 4101 [32] Zhao, F., Zhou, X., Shi, Y., … Yu, G (2018) Highly efficient solar vapour generation via hierarchically nanostructured gels Nature Nanotech 13 (2018) 489–495 https://doi.org/10.1038/s41565-018- 45