Solar-driven membrane separation for direct lithium extraction from artificial salt-lake brine

The demand for lithium extraction from salt-lake brines is increasing to address the lithium supply shortage. Nanofiltration separation technology with high Mg2+/Li+ separation efficiency has shown great potential for lithium extraction. However, it usually requires diluting the brine with a large quantity of freshwater and only yields Li+-enriched solution. Inspired by the process of selective ion uptake and salt secretion in mangroves, we report here the direct extraction of lithium from salt-lake brines by utilizing the synergistic effect of ion separation membrane and solar-driven evaporator. The ion separation membrane-based solar evaporator is a multilayer structure consisting of an upper photothermal layer to evaporate water, a hydrophilic porous membrane in the middle to generate capillary pressure as the driving force for water transport, and an ultrathin ion separation membrane at the bottom to allow Li+ to pass through and block other multivalent ions. This process exhibits excellent lithium extraction capability. When treating artificial salt-lake brine with salt concentration as high as 348.4 g L−1, the Mg2+/Li+ ratio is reduced by 66 times (from 19.8 to 0.3). This research combines ion separation with solar-driven evaporation to directly obtain LiCl powder, providing an efficient and sustainable approach for lithium extraction.

even an NF system would be helpful.The study claims that it has the ability to produce Li2CO3 with baftery-grade purity.However, according to the crystallizafion rate of LiCl, nearly all LiCl and NaCl can pass through the system and form a crystal mixture of NaCl and LiCl.Based on the concentrafion of LiCl and NaCl in the simulated lake brine, the amount of NaCl salt is much higher than LiCl.How is it claimed that the study can produce Li2CO3 with a purity of 99%?It is noteworthy to menfion the study has not conducted any experiment regarding the precipitafion process to purify LiCl and extract it from NaCl salts.2. Crystal formafion can occur within the photothermal layers, leading to the clogging of membrane pores and blocking the photothermal layer.The study lacks a fouling/scaling control strategy and does not employ scaling predicfion methods.3. The diffusion rate of lithium ions hasn't been compared with the LiCl crystallizafion rate.From Fig. 4c, the transmembrane rate of lithium (0.9 mol m-2 h-1) is calculated as around 6.2 g m-2 h-1, which is much lower than the LiCl crystallizafion rate (approximately 40 g m-2 h-1, Fig. 5a).The diffusion rate and the crystallizafion rate don't align with each other in this study.A mass balance needs to be considered.4. The selecfivity of Li over other ions has not been evaluated.Please find below the general comments: 1.The abstract exceeds the recommended words outlined in the guide for authors (approximately 220 words).2. Line 95, Fig. 1 a doesn't match with the context.It should be Figure 2. (Same for Fig. 1 b-i from line 103 to line 135) 3. Use consistent terminology for nanofiber.In line 99, change nano-fibers to nanofibers. 4. It hasn't been noted why PANI and PES are chosen.5.The introducfion requires revision in some parts as it doesn't adequately introduce the main quesfion that the study aims to address.Also, it lacks a literature review and does not showcase the novelty of this research, which is crucial to highlight the significance of the study.6.It's not common to indicate the results in the introducfion, i.e., line 88: with a purity as high as 94.5%.7. What is the reference for the method of Fabricafion of PANI nanoarrays evaporator?For example, why are 93 mg aniline and 114 mg ammonium persulfate chosen to fabricate the nanoarrays?8. Refer to the previous comment for the fabricafion of the PA membrane.9.In line 328, what do you mean by the concentrafion of LiCl, MgCl2 feed solufion were 2000 mg L-1, respecfively?Is the concentrafion of both LiCl and MgCl2 equivalent to 2000 mg L-1?In the results, their concentrafion has been reported as 1 mg L-1 for rejecfion tests.10.It's not apparent in the method that the membrane performance has been tested in the mixed solufion.All the procedures (which are explained in the results in the current format) must be moved to their related secfions in the method.11.It had to be menfioned how the required energy for stripping water from the hydrafion shell of Mg and Li is calculated.(Lines 195-197)  12. Use relevant references on Donnan equilibrium to support the discussion made on the increase in LiCl crystallizafion rate from 37.3 to 61.8 g m-2 h-1.13.There is no discussion in the context of paper for Fig. 5a.14.How did you find the concentrafions in the Uyuni salar brine?Why didn't you add KCl to the simulated brine?It doesn't have any reference.
2-7 g L −1 depending on the process design and original brine concentration (Miner.Eng.2016, 89, 119; Adv.Sci.2022, 9, 2201380).However, Mg 2+ is enriched at the same time, close to saturation in some cases.Thus, solar evaporation itself cannot achieve efficient Li + /Mg 2+ separation especially for high Mg/Li ratio brines.Nanofiltration (NF) is the most widely adopted Li + /Mg 2+ separation approach in the salt-lake lithium extraction industry.Because of the high osmotic pressure of highly concentrated brines, an NF membrane requires a high applied pressure that may exceed the mechanical strength of the membrane module.Therefore, the conventional NF process typically involves the 10-20 times dilution of high-concentration brine with a large quantity of freshwater in the pre-treatment stage.Moreover, NF membrane separation processes solely yield Li + -enriched solutions, necessitating further concentration to obtain solid lithium products, which requires energy-intensive processes like thermal distillation or high-pressure RO to obtain the Li + -enriched solution with the required concentration.Despite its higher efficiency, the NF process requires at least 4000 kWh of electricity to generate one ton of Li2CO3 (J.Membr.Sci.

2021, 635, 119441).
In this work, we designed a new method utilizing the synergistic effect of an ion separation membrane and a solar-driven evaporator to realize Li + /Mg 2+ separation and Li + concentration in one step.The ion separation membrane under the photothermal layer allows Li + to pass through and block Mg 2+ .During the water evaporation process, Li + was selectively enriched in the photothermal layer and crystallized in the form of LiCl.Our designed ion separation membrane-based solar evaporator has a water evaporation rate of around 1.0 kg m -2 h -1 under 1 sun irradiation.We would like to clarify that the efficiency of solar-powered evaporation can not compete with energyintensive industrial processes.The advantage of our designed membrane-based solar evaporator is that it can realize Li + /Mg 2+ separation and Li + concentration in one step only utilizing the abundant solar energy resources in the salt-lake area, which offers a low-barrier-of-entry option for lithium extraction.
(3) Regarding the PANI layer on PES membrane, how fast is the reaction?
Response: According to the reviewer's comment, we monitored the polymerization process of aniline in solution.There was no color change for the first 3 hours, then the solution gradually turned light blue and darkened to a black-blue color over the next 60 minutes (Figure R1).These results suggest that aniline polymerization consists of two stages: nucleation and growth (Angew.Chem.Int.Ed. 2004, 43, 5817; Adv.Mater.2005,   17, 1679).The first three hours involve nucleation, followed by a rapid growth stage once nuclear sites have formed.To clarify this point, the sentence "The polymerization process formed nano-fibers by rapidly polymerizing aniline monomers via ammonium persulfate." in the original manuscript has been revised to "Nanofibers were formed through a polymerization process of aniline monomers using ammonium persulfate."(4) Figure 2: There is no description on Figure 2.

Response:
We are sorry for this mistake.The part "Fabrication and characterization of PANI nanoarrays solar evaporator (Page 5-7)" is the description of Figure 2. We have revised them in the revised manuscript.
Reviewer #2 (Remarks to the Author): General comment: This study has reported the direct extraction of LiCl powder from simulated salt-lake brine by combining an ion separation membrane and a solar-driven evaporator system, inspired by the selective water/ion uptake and salt secretion in mangroves.The process involves an upper polyaniline (PANI) nanofiber array as a photothermal layer to evaporate water, a middle hydrophilic PES macroporous membrane generating capillary pressure as the driving force for water transport, and a bottom ultrathin polyamide ion separation membrane allowing passage of lithium ions while rejecting other multivalent ions, like calcium and magnesium.The system can collect LiCl powder with a purity of 94.2% from a LiCl/MgCl2 mixed solution.In treating with the simulated salt-lake brine with a TDS of 348.4 g L −1 , the process has the ability to reduce the Mg 2+ /Li + ratio from 19.8 to 0.3.The idea of lithium extraction by bioinspiring from mangroves is interesting.However, the paper doesn't meet the standards that make it improper to publish in Nature Communications.

Response:
We are very grateful to the reviewer's comments and suggestions, which are beneficial to improve the quality of our manuscript.Meanwhile, we appreciate the reviewer for pointing out some problems, which are all very important for revising our manuscript.We have tried our best to conduct additional experiments and provide further discussions to address the comments of the reviewer.All changes have been highlighted in red color in the revised manuscript.We hope that the revised manuscript is suitable for publication in Nature Communications.
(1) Although the concept seems new, the commercial potential of this study is under question.It seems the system has not demonstrated monovalent selectivity Na/Li.The Mg can be easily separated from Li, on a large scale, using more conventional unit operations that have much less complexity than this work, even an NF system would be helpful.The study claims that it has the ability to produce Li2CO3 with battery-grade purity.However, according to the crystallization rate of LiCl, nearly all LiCl and NaCl can pass through the system and form a crystal mixture of NaCl and LiCl.Based on the concentration of LiCl and NaCl in the simulated lake brine, the amount of NaCl salt is much higher than LiCl.How is it claimed that the study can produce Li2CO3 with a purity of 99%?It is noteworthy to mention the study has not conducted any experiment regarding the precipitation process to purify LiCl and extract it from NaCl salts.

Response:
We would like to clarify that lithium extraction from salt-lake brine mainly involves three stages.In the first stage, brine will be concentrated in solar evaporation ponds, resulting in the precipitation of NaCl and KCl salts.After the precipitation of NaCl and KCl salts, Li + concentration in raw brine is enriched to 0.3-0.5 g L −1 or even 2.0-7.0 g L −1 depending on the process design and original brine concentration (J.In some cases, the concentrations of Na + and K + ions are similar to that of lithium ions in raw brine.Meanwhile, Mg 2+ ions are enriched and can reach saturation in certain cases.Therefore, reducing the Mg 2+ at the second stage is critical for lithium carbonate production.There is no doubt that NF membrane separation technology is one of the effective ion separation methods, particularly for Li + /Mg 2+ separation.Althrough, all of the monovalent ions can pass through the NF membrane, the separation of monovalent ions will be realized in the last stage of lithium extraction from brine by adding Na2CO3 to form Li2CO3 precipitation.The solubility of Li2CO3, Na2CO3, and K2CO3 are quite different, where the solubility of Li2CO3 is very low (0.82 at 80 °C) and the solubility of Na2CO3 and K2CO3 are high (45.1 at 80 °C and 140 at 80 °C, respectively).Therefore, Li + can be easily precipitated in the form of carbonates after adding Na2CO3.
In our original manuscript, we have mentioned that "At a low Mg 2+ /Li + ratio, after adding NaOH and sodium oxalate to remove residual small amounts of Mg 2+ and Ca 2+ , lithium can be readily precipitated out in the form of Li2CO3 by adding Na2CO3."To clarify this point, the detailed method of carbonate precipitation was added in Method section in the revised manuscript (page 16, line 21-25 and page 17, line 1-9).We copied here for reviewer's convenience: "5 g of collected salt powders were added in 5 mL water to create a saturated solution.
The pH value was adjusted to 11 using a saturated NaOH solution to remove any remaining Mg 2+ .The white precipitate was removed by centrifuge at 5000 rpm for 10 mins.Next, a saturated sodium oxalate solution was slowly added to the upper clear solution in order to remove any remaining small amount of Ca 2+ .The mixture was centrifuged again at 5000 rpm for 10 mins, and the upper clear solution was collected.
Finally, a saturated Na2CO3 solution was added to the collected solution at 80 °C .The white precipitates were collected after centrifuge and dried in an air-forced oven at 60 °C for 12 hours." (2) Crystal formation can occur within the photothermal layers, leading to the clogging of membrane pores and blocking the photothermal layer.The study lacks a fouling/scaling control strategy and does not employ scaling prediction methods.

Response:
We understand the reviewer's concern.A 6-hour continuous experiment was conducted to evaporate simulated salt-lake brine with a TDS of 348.4 g L -1 under 1 sun irradiation.The experiment recorded the water evaporation rate, surface temperature of PANI photothermal layer, and salt crystal formation process (Figure R2).
At the beginning, the water evaporation rate is 1.08 L m -2 h -1 , the surface temperature of PANI photothermal layer is 41 °C.At the 3 rd hour, tiny salt crystals can be observed on the surface of PANI photothermal layer.The water evaporation rate slightly declines to 0.95 L m -2 h -1 .With the increasing evaporation time, more and more salt crystals can be observed on the surface.It is worth noting that the surface temperature was maintained at 41-42 °C even though the surface was fully covered by salt crystals.After 6 hours, the rate of water evaporation decreases to 0.90 L m -2 h -1 , which suggests that the salt crystals formed on the surface of the photothermal layer are affecting the water evaporation.However, in this structure, the salt crystals are unable to completely block the membrane pores or the photothermal layer.
The target of our membrane-based solar evaporator is obtaining Li-enriched salt powder.We propose a fouling control strategy to regenerate the PANI photothermal layer by recovering salt crystals during weak sun irradiation or at night.The photothermal layer and the ion separation layer are separate from each other (Figure R2b).This means that when the photothermal layer is fully covered by salt powder, it can be removed from the evaporator.Large salt crystals can be removed using a scraper, while any remaining small salt crystals can be washed away with a small amount of water.We will utilize the collected crystals and solution for the precipitation of lithium carbonate.After regenerating the PANI photothermal layer, the water evaporation rate can recover to the initial value of around 1.0 L m -2 h -1 .

Figure R2. (a)
Water evaporation rate and surface temperature of PANI photothermal layer during the 6-hour continuous experiment for evaporating simulated salt-lake brine with a TDS of 348.4 g L -1 under 1 sun irradiation.(b) Photography of salt crystal formation process on the surface of PANI photothermal layer.After the 6-hour continuous experiment, large salt crystals can be removed using a scraper, while any remaining small salt crystals can be washed away with a small amount of water to regenerate the PANI photothermal layer.
To evaluate the potential for application, we carried out an outdoor experiment from 9:00 to 16:00 under natural sunlight with an average intensity of ~700 W m −2 .The membrane-based solar evaporator was employed to treat the simulated salt-lake brine.
As shown in Figure R3a, the rate of water evaporation is influenced by the intensity of solar irradiation.The maximum water evaporation rate of 0.95 L m -2 h -1 was observed at noon, which is consistent with the result obtained in the laboratory under 1 sun irradiation.At 16:00, the salt crystals were collected, and the PANI was regenerated for tomorrow's experiment.During the following 5-day test, the amount of evaporated water and collected salt crystals were maintained stable (Figure R3b), showing its great potential for practical lithium extraction.In addition, the scalability of the membrane-based solar evaporator is also a critically important consideration.The system can be scaled up easily by increasing its size and multiplying the brine treatment capacity using an array of solar evaporators.Under the field conditions, the solar incident angle, temperature, relative humidity, and natural wind will affect the performance of the solar evaporator.A comprehensive evaluation of such effects is necessary for the practical application of the solar crystallizer toward practical lithium extraction.
Figure R3 has been added to the revised Supplementary Materials as Supplementary Figure 6, and the corresponding discussion has been added in the revised manuscript (page 13, line 2-15).We copied here for reviewer's convenience: "To evaluate the potential for application, we carried out an outdoor experiment which carried out from 9:00 to 16:00 under natural sunlight with an average solar heat flux of ~0.7 kw m −2 .The membrane-based solar evaporator was employed to treat the simulated salt-lake brine.As shown in Supplementary Fig. 6, the rate of water evaporation is influenced by the intensity of solar irradiation.The maximum water evaporation rate of 0.95 L m -2 h -1 was observed at noon, which is consistent with the result obtained in the laboratory under 1 sun irradiation.At 16:00, the salt crystals were collected, and the PANI was regenerated for tomorrow's experiment.During the following 5-day test, the amount of evaporated water and collected salt crystals were maintained stable, showing its great potential for practical lithium extraction.In addition, the scalability of the membrane-based solar evaporator is also a critically important consideration.The system can be scaled up easily by increasing its size and multiplying the brine treatment capacity using an array of solar evaporators." (3) The diffusion rate of lithium ions hasn't been compared with the LiCl crystallization rate.From Fig. 4c, the transmembrane rate of lithium (0.9 mol m -2 h -1 ) is calculated as around 6.2 g m -2 h -1 , which is much lower than the LiCl crystallization rate (approximately 40 g m -2 h -1 , Fig. 5a).The diffusion rate and the crystallization rate don't align with each other in this study.A mass balance needs to be considered.
Response: In Fig. 4c, we measured the transmembrane rate of lithium at 0.9 mol m -2 h - 1 when evaporating a mixed solution containing 0.45 g L -1 of LiCl.The relative molecular mass of LiCl is 42.39 g mol -1 .The LiCl crystallization is calculated to be 38.2 g m -2 h -1 (0.9*42.39).Therefore, the diffusion rate is consistent with the crystallization.
(4) The selectivity of Li over other ions has not been evaluated.

Response:
The selectivity of Li + over K + , Na + , Ca 2+ and Mg 2+ were evaluated by comparing their transmembrane rate.We measured the transmembrane ion rate for chloride salt solutions at 10 mmol L -1 under 3 sun irradiation.The rates for Li + , K + , Na + , Ca 2+ , and Mg 2+ were 0.91, 0.86, 0.84, 0.15, and 0.07 mol m -2 h -1 , respectively (Figure R4a).The selectivity of Li + /K + , Li + / Na + , Li + /Ca 2+ , Li + /Mg 2+ are 1.06, 1.08, 6.07 and 13.00, respectively (Figure R4b).Here, we would like to clarify that although the selectivity of Li + /K + and Li + / Na + are close to 1, it is not an issue to be solved by NF Therefore, Li + can be easily precipitated in the form of carbonates after adding Na2CO3.

General comments:
(1) The abstract exceeds the recommended words outlined in the guide for authors (approximately 220 words).

Response:
The abstract has been shortened to 200 words in the revised manuscript.We copied here for reviewer's convenience: "The demand for lithium extraction from salt-lake brines is increasing to address the separation efficiency has shown great potential for lithium extraction.However, it usually requires diluting the brine with a large quantity of freshwater and only yields Li + -enriched solution.Inspired by the process of selective ion uptake and salt secretion in mangroves, we report here the direct extraction of lithium chloride (LiCl) powder from salt-lake brines by utilizing the synergistic effect of ion separation membrane and solar-driven evaporator.The ion separation membrane-based solar evaporator is a sandwich structure consisting of an upper photothermal layer to evaporate water, a hydrophilic macroporous membrane in the middle to generate capillary pressure as the driving force for water transport, and an ultrathin ion separation membrane at the bottom to allow Li + to pass through and block other multivalent ions.This process exhibits outstanding lithium extraction capability.When treating simulated salt-lake brine with salt concentration as high as 348.4 g L −1 , the Mg 2+ /Li + ratio is reduced by 66 times 19.8 to 0.3).This research combines ion separation with solar-driven evaporation to directly obtain LiCl powder, providing an efficient and sustainable approach for lithium extraction." (2) Line 95, (3) Use consistent terminology for nanofiber.In line 99, change nano-fibers to nanofibers.
Response: "Nano-fibers" has been revised to "nanofibers" in the revised manuscript.
4. It hasn't been noted why PANI and PES are chosen.
Response: Thanks for your suggestion.To clarify this point, the corresponding description has been added to the revised manuscript (page 5, line 1-6).We copied here for your convenience: "To realize a high photothermal conversion efficiency, vertically-aligned polyaniline (PANI) nanofiber array was selected as the upper photothermal layer owing to its excellent sunlight absorption capacity.In the middle, a hydrophilic poly(ether sulfone) (PES) macroporous membrane with continuous water-conducting channels generates capillary pressures serving as the driving force for water transport." 5. The introduction requires revision in some parts as it doesn't adequately introduce the main question that the study aims to address.Also, it lacks a literature review and does not showcase the novelty of this research, which is crucial to highlight the significance of the study.
Response: Thanks for the constructive suggestions, we have revised the Introduction and added a corresponding review to showcase the novelty of this research.
We copied here for your convenience: "Compared to conventional ion separation technologies such as ion exchange 12 , electrodialysis 13 , and solvent extraction 14 , nanofiltration (NF) membrane separation 15- 17 is considered one of the most efficient methods for extracting lithium from brine." (page 3, line 10-13) "Despite significant advancements in the separation of Mg 2+ and Li + using NF membrane processes, highly concentrated brines generate a high osmotic pressure difference across the NF membrane, requiring high applied pressure that may exceed the mechanical strength of the membrane module."(page 3, line 18-21) "Moreover, NF membrane separation processes solely yield Li + -enriched solutions, necessitating further concentration to obtain solid lithium products, which requires energy-intensive processes like thermal distillation or high-pressure RO to obtain the Li + -enriched solution with the required concentration.Hence, innovative material and separation process design is required to achieve more efficient and cost-effective Mg/Li separation."(page 3, line 25 and page 4, line 1-4)  11, 2015).These references have been cited in the original manuscript.To clarify this point, the sentence "The polyamide membrane was prepared at 25.0 ± 0.5 °C and 60 ± 5 % relative humidity" has been revised to "The polyamide membrane was prepared at 25.0 ± 0.5 °C and 60 ± 5 % relative humidity following previous study 22,53 ." in the revised manuscript (page 14, line 17).9.In line 328, what do you mean by the concentration of LiCl, MgCl2 feed solution were 2000 mg L -1 , respectively?Is the concentration of both LiCl and MgCl2 equivalent to 2000 mg L -1 ?In the results, their concentration has been reported as 1 mg L -1 for rejection tests.
Response: Sorry for the confusion, we have revised the sentence to "Either 1.0 g/L LiCl solution or 1.0 g/L MgCl2 solution was used as feed solution." in the revised manuscript (page 15, line 16-17).The salt concentration, 1.0 g/L, is consistent with the result in the original manuscript.
10. It's not apparent in the method that the membrane performance has been tested in the mixed solution.All the procedures (which are explained in the results in the current format) must be moved to their related sections in the method.
Response: The membrane performances were tested in the mixed solution under solar irradiation.To clarify this point, the sentence "A mixed solution containing a certain amount of LiCl and MgCl2 was added in a container."in the original manuscript has been revised to "A LiCl and MgCl2 mixed solution was added in a container.When evaluating the effect of the Mg 2+ /Li + ratio on solar-driven lithium extraction, the LiCl concentration was kept constant at 0.45 g L -1 in the mixed salt solution while the MgCl2 concentration was gradually increased from 0.45 to 4.50 g L -1 .When investigating the impact of salt concentrations, the overall salt concentration was increased from 10 to 80 g/L while keeping a MgCl2/LiCl mass ratio of 1.0." in the revised manuscript (page 16, line 1-6).
The method for Lithium extraction from simulated salt-lake brine was added to the revised manuscript (page 16, line 21-25 and page 17, line 1-9).We copied here for your convenience: "Lithium extraction from simulated salt-lake brine.The bine was prepared based on the typical geothermal brine composition at Uyuni salar brine 58,59 , in Bolivia, containing 268.0 g L −1 NaCl, 5.1 g L −1 LiCl, 66.1 g L −1 MgCl2, and 9.2 g L −1 CaCl2.
The simulated salt-lake brine was used as the feed solution for the solar evaporator.
Under continuous irradiation, salt crystals formed on the PANI layer surface and were collected once the surface was fully covered.5 g of collected salt powders were added in 5 mL water to create a saturated solution.The pH value was adjusted to 11 using a saturated NaOH solution to remove any remaining Mg 2+ .The white precipitate was removed by centrifuge at 5000 rpm for 10 mins.Next, a saturated sodium oxalate solution was slowly added to the upper clear solution in order to remove any remaining small amount of Ca 2+ .The mixture was centrifuged again at 5000 rpm for 10 mins, and the upper clear solution was collected.Finally, a saturated Na2CO3 solution was added to the collected solution at 80 °C.The white precipitates were collected after centrifuge and dried in an air-forced oven at 60 °C for 12 hours."

Figure R1 .
Figure R1.Photographs of the polymerization process of aniline in solution.

Figure R3 .
Figure R3.(a) Sunlight intensity and water evaporation rate during the outdoor experiment from 9:00 to 16:00 at Soochow University campus during 25-29 th October.Inset in Figure R4a is the setup for the evaporation.(b) The amount of evaporated water and collected salt crystals on the unit area during the 5-day test.
membrane process or membrane-based solar evaporation process, because the separation of monovalent ions will be realized in the last stage of lithium extraction from brine by adding Na2CO3 to form Li2CO3 precipitation as we have explained in response to reviewer2's comment #1.The solubility of Li2CO3, Na2CO3, and K2CO3 are quite different, where the solubility of Li2CO3 is very low (0.82 at 80 °C) and the solubility of Na2CO3 and K2CO3 are high (45.1 at 80 °C and 140 at 80 °C, respectively).
lithium supply shortage.Nanofiltration separation technology with high Mg 2+ /Li + K + Li + /Na + Li + /Ca 2+ a b Fig. 1 b-i from line 103 to line 135) Response: We are sorry for this mistake.The part of "Fabrication and characterization of PANI nanoarrays solar evaporator (Page 5-6)" is the description of Figure 2. We have revised them in the revised manuscript.
: The sentence "As water continually evaporates, solid LiCl powders can be collected directly on the surface of the evaporator, with a purity as high as 94.5%." in the original manuscript has been revised to "As water continually evaporates, solid LiCl powders can be collected directly on the surface of the evaporator."(page 5, line 9-11) 7. What is the reference for the method of Fabrication of PANI nanoarrays evaporator?The fabrication of PANI nanoarrays refers to previous studies (Angew.Chem.Int.Ed. 2004, 43, 5817 and Adv.Mater.2005, 17, 1679), which demonstrated the polymerization of aniline in a dilute solution is a homogeneous nucleation process rather than a heterogeneous one and the polyaniline tends to grow in the form of nanofibers.The concentrations of aniline and ammonium persulfate are the optimized results referring to previous studies.The corresponding references have been cited as Ref. 51 and 52 in the revised manuscript.