High-salinity Brine Research Articles

Water recovery from the high salinity brine: Effect of the interlayer structure in the polyamide nanofiltration membrane

Water recovery by nanofiltration (NF) from the high salinity brine is emerging as a promising technology to alleviate the water shortage. Thin film composite membranes with polyamide (PA) selective layer are the mainstream in the field of NF. Nevertheless, the trade-off between permeance and retention as well as the structural stability of the mainstream PA membrane still restrict their widespread application. Herein, a novel interlayered thin-film nanocomposite (TFNi) nanofiltration membrane was fabricated based on the interfacial polymerization. The PDA@MXene hybrid was employed as the interlayer to modulate the adsorption and diffusion process of amine monomers, giving rise to the formation of thin and rough PA selective layer, which could accelerate the transport of water molecules. Moreover, PM-TFNi membrane demonstrated higher crosslinking degree and more negatively charged surface, significantly benefiting the repulsion of inorganic salt ions. In this context, PM-TFNi membrane rendered a competitive permselectivity with the water flux of 18.3 L m−2 h−1 bar−1 and the Na2SO4 rejection of 98.0%. In addition, PM-TFNi membrane exhibited distinguished long-term stability and pH resistance. Overall, this work would provide a paradigm shift in designing high-performance and robust NF membrane for the water treatment.

Natural lignocellulosic kapok fiber/MXene constructed hydrogel evaporators for high efficiency solar steam generation

Solar-driven interfacial evaporation (SDIE) is a green and sustainable technique for desalination. Hydrogel composite evaporators have been widely used for SDIE, but it is still challenging for the hydrogel evaporators to achieve uniform distribution of the light absorbing nanomaterials and at the same time possess satisfactory evaporation rate, durability and environmental applicability. We developed a 3D hydrogel evaporator with an asymmetric structure for high-efficiency SDIE. Natural kapok fibers, an important lignocellulosic plant fiber with a hollow structure, are decorated with MXene nanosheets for construction of one-dimensional photothermal conversion network. The top composite hydrogel serves as the light-absorption layer where MXene-modified kapok fibers are evenly dispersed in PVA hydrogel, while the bottom PVA hydrogel with an oriented structure acts as water delivery path. The evaporator exhibits a high solar evaporation rate and efficiency (2.49 kg·m−2·h−1 and 91.5 %, respectively) under one sun irradiation (1 kW·m−2). Even in a high salinity brine, emulsion and corrosive solutions, the evaporator can work normally with a slightly decreased evaporation rate. The 3D hydrogel evaporator with long-term stability and durability shows promising applications in purification of seawater and different waste water.

Geochemical characteristics of shale gas hydraulic fracturing flowback/produced water in Zheng’an block, northern Guizhou Province, China

Guizhou Province of China is rich in shale gas resources. In recent years, important progress has been made in the exploration and development of shale gas in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in Zheng'an block in northern Guizhou, adjacent to Sichuan Basin. Due to the complex geological conditions and fragile ecological environment in the shale gas distribution area, serious environmental pollution risks may exist in shale gas exploitation. Therefore, this paper conducted element, hydrogen and oxygen isotope analyses for shale gas fracturing flowback/produced water of Well AY7-4 in Zheng'an block. The results showed that the contents of K, Na, Ca, Mg and NH4+ in the flowback/produced water of Well AY7-4 were very high, with an average of 118 mg/L, 7616 mg/L, 266 mg/L, 47 mg/L and 76 mg/L, respectively. The content of Na, Ca and Mg is similar to that of shale gas flowback/produced water in Weiyuan, but lower than that in Changning and Fuling. NH4+ content was similar to that in Changning, but much higher than that in Weiyuan. The average Cl content was 11605 mg/L, which was similar to that in Weiyuan, but lower than that in Changning and Fuling. The average Br content is 48 mg/L, slightly lower than that of Weiyuan, and about half of that of Changning and Fuling. Correspondingly, the Br/Cl value of Well AY7-4 is the lowest, reflecting its relatively low Br content. The average content of Li, B and Sr is 17 mg/L, 10 mg/L and 45 mg/L, respectively, which is similar to that of the Weiyuan, Changning and Fuling shale gas fields. The distribution model of Li and Sr is similar to that of Cl, Br and Na, but the B content and B/Cl value of Well AY7-4 are the lowest. The linear relationship between Br and Cl contents and between δD and δ18O of flowback/produced water of Well AY7-4, freshwater used for hydraulic fracturing and hydraulic fracturing injected fluid indicates that flowback/produced water of Well AY7-4 is mainly the mixed product between low salinity injected fracturing fluid and high salinity brine retained in shale formation. The hydrogen and oxygen isotopic compositions gradually become heavier over time, indicating that the proportion of high salt end formation brine in flowback/produced water is increasing. The contents of Cl, Br, Na and NH4+ in the flowback/produced water of Well AY7-4 are far higher than the allowable discharge value, which is a potential environmental pollution risk and cannot be discharged directly.

Scalable absorber with tuneable water supply fabricated via centrifugal spinning for highly efficient and stable solar-driven interfacial desalination

Although realising tuneable water supply in photothermal evaporation is an effective way to boost solar-driven interfacial evaporation for water desalination, simultaneously achieving continuous water transport and appropriate water content in evaporators remains a significant challenge. To address this challenge, centrifugal spinning technology is proposed herein to fabricate a scalable, flexible and stable photothermal evaporator from a hydrophilic (polyacrylonitrile, (PAN)) and hydrophobic polymer medium (polyurethane, (PU)). Efficient water management can be realised by tuning the parameters of polymer materials to permit vapour escape and achieve salt resistance. In addition, the arched design of the evaporator allows for omnidirectional evaporation, which enhances the photothermal conversion efficiency. The scalable centrifugal spinning nonwoven membrane-based arched evaporator prepared at the optimal hydrophilic–hydrophobic polymer ratio (21 wt% PAN and 2 wt% PU) after polypyrrole modification (PPy/21PAN/2PU CSMAE) offers a highly efficient evaporation rate of 1.82 kg m−2 h−1 with photothermal efficiency of 97.33 % under 1-sun illumination and excellent salt resistance against high-salinity brine (10 wt%). Thus, the unique properties of centrifugal spinning technology enable the large-scale preparation application of multicomponent polymeric materials for realising tuneable water supply in solar-driven interfacial evaporation and desalination.

The two salinity peaks mode of marine salt supply to coastal underground brine during a single tidal cycle

Seawater salt is constantly supplied from the marine environment to coastal underground brine deposits, meaning that brine has the potential for continuous extraction. There is currently a lack of information about the processes that drive the fluxes of seawater salt to underground brine deposits in tidal-driven brine mining areas. We chose the Yangkou salt field on the southern coast of Laizhou Bay, a brine mining area, as our study site. We monitored the spatial and temporal distribution of the underground brine reserve and the changes in water level and salinity in the mining area and adjacent tidal flats using electrical resistivity tomography and hydrogeological measurements. We monitored cross-sections along two survey lines and observed that the underground brine reserve receives a stable supply of seawater salt, and calculated that the rate of influx into the brine body in the mining area near the boundary of the precipitation funnel was 0.226−0.232 t/h. We calculated that a total salt flux of approximately 5.50 t enters the underground brine body every day through a 150 m long shoreline and a 1322.3 m2 window, which is sufficient to sustain the daily extraction of one brine well. During tidal cycles, there are two peaks in the salinity of the water supplied to the underground brine reserve, which means that the brine supply is from at least two high-salinity salt sources in different tidal stages. The first salinity peak occurs during the initial stage of the rising tide after seawater inundates the tidal flat. At this time, seawater, which is a solution and carries a large amount of evaporated salt, is transported into the brine layer through highly permeable areas or biological channels and replenishes the brine in the mining area. The second salinity peak occurs during the early stage of the falling tide. Influenced by hysteresis-driven tidal pumping, high-salinity brine from the lower intertidal zone is rapidly transported into the mining area, thereby increasing the salinity of the underground brine.

Comparison of simple and active solar stills for freshwater recovery during lithium brine mining

Lithium mining from brines raise environmental issues due to huge volumes of both saline and freshwater being constantly pumped in desertic environments. Data indicating the slow depletion of both underground water levels and lagoon surfaces in the regions where large lithium brine mining exploitations are located have recently being disclosed. Amongst different direct lithium extraction methodologies, DLE, for more sustainable lithium recovery, a few proposals aim at the recovery of freshwater from the high salinity brines. About 900 kg of freshwater could potentially be recovered per cubic meter of processed native brine. The water evaporation and freshwater production capabilities of a simple and an active solar still are compared in this work. These are two simple and relatively low-cost technologies that could be adapted to existing solar evaporation ponds. The two systems were thermodynamically modelled. Equations were derived which were fed with real meteorological data from the Olaroz salt lake location and brine properties derived from the Pitzer model for the said brine. Analysis of the heat fluxes show that the behavior of both systems is relatively similar with large heat losses that are responsible for neither of the systems reaching the evaporation rate of the evaporation ponds.

Performance investigation of poly(vinylidene fluoride-cohexafluoropropylene) membranes containing SiO2 nanoparticles in a newly designed single vacuum membrane distillation system.

The current study focuses on the development of a superhydrophobic poly(vinylidene fluoride-cohexafluoropropylene) nanocomposite membrane suitable for vacuum membrane distillation by incorporating SiO2 nanoparticles. At loading hydrophobic nano-SiO2 particle concentration (0.50-1.50 wt.%), the developed nanocomposite membranes are optimized in terms of vacuum membrane distillation performance. The influence of temperature, vacuum pressure, and feed water flow is studied for desalinating high-salinity brine. The results show that the developed vacuum distillation membrane is capable of 95% salt rejection during the treatment of a highly saline feed (65,000 ppm) at fixed flow rates of 120L/h saline feed and different operating conditions consisting of feed inlet temperatures ranging from 40°C to 70°C and distillate inlet temperatures of 7-15°C. The vacuum membrane distillation process achieves 0.38-1.66% water recovery with increasing concentration factor, meaning that recovery is increased, and shows a specific electrical energy consumption of 5.16-23.90 kWh/m3 for product water. Overall, the newly designed membrane demonstrates suitability for a vacuum membrane distillation system. PRACTITIONER POINTS: Desalinate high-salinity brine (TDS > 35,000 ppm) using a vacuum membrane distillation system. A hydrophobic PVDF-HFP/SiO2 nanocomposite membrane development for vacuum membrane distillation. A newly designed single vacuum membrane distillation system for RO brine treatment.

Biomass derived evaporator with highly interconnected structure for eliminating salt accumulation in high-salinity brine

Solar-driven evaporator is regarded as an energy-saving and eco-friendly desalination technology. However, available unfriendly synthetic materials and salt crystallization problems limit the evaporator's performance and development, especially in high-salinity condition. Hence, inspired by the highly interconnected microchannels, a carbonized white gourd (CWG) derived self-desalting evaporator was developed to evaporate and desalinate seawater. To evaluate the efficacy of the porous features, the effect of different porosity configurations on water evaporation and anti-salt abilities of CWG was discussed. High and stable evaporation rates of 1.76 and 1.44 kg·m−2·h−1 were reached for 3.5 wt% and 20 wt% NaCl solutions, respectively, which were attributed to the highly efficient water transport and self-desalting capabilities, and it further increased to 2.19 kg·m−2·h−1 by adding an extra convective air (2 m/s) located at the evaporation interface. Moderate airflow effectively enhanced the evaporation efficiency and delayed re-crystallization of salt, promoting a long-term stable desalination process. Conversely, excessive convective flow (4 m/s) may directly impair evaporative stability and salt resistance. This research is expected to provide a new insight into the design of high performance, low cost, eco-friendly and salt-resistant evaporator applied to solar desalination.

(Invited) Electrochemical Deionization for Water Desalination and Direct Lithium Extraction

Electrochemical deionization based on carbonaceous and intercalation electrodes has been proposed as a promising candidate for desalinating saline water and for selectively separating toxic or valuable ionic constituents from water. In this talk, I will first introduce our work on the performance evaluation and techno-economic assessment for electrochemical desalination of brackish water. Parametric models were established to estimate the unit cost of water desalination and energy efficiency in electrochemical desalination with different configurations, and results were compared against brackish water reverse osmosis. In the second part of the talk, I will present our work on the development of selective electrochemical separation systems, focusing on the recovery of lithium from water streams. We investigated the selectivity of lithium separation in electrolyte solutions with different cation concentration ratios as well as in simulated brines. Results show that lithium chloride with a purity of >95% can be extracted from high-salinity brines in the presence of competing monovalent and divalent cations.

Bioinspired Graphene Aerogels with Hybrid Wettability for Solar-Driven Purification of Complex Wastewater.

Salt deposition and pollutant enrichment greatly hamper efficient and sustainable water production for a solar evaporator. Inspired by the desert beetle, a dual-region hydrophobic graphene/hydrophilic titanium dioxide (TiO2) aerogel (GTA) with internal hydrophilic-hydrophobic hybrid wettability structure is prepared via a facile freeze-drying and thermal reduction method. The evaporator shows adjustable wettability, optimized water content, and a low energy loss in the evaporation process. Simultaneously, the hybrid wetting structure in aerogel subjects salt to a dynamic crystallization-dissolution process to prevent salt deposition. The GTA solar evaporator achieves an evaporation rate of 1.52 kg·m-2·h-1 with a 91.02% efficiency under 1 sun irradiation. Furthermore, GTAs achieve a stable evaporation rate in high salinity brine (25 wt % NaCl) under 1 sun irradiation for 100 h, which could compete well with other most advanced photothermal evaporation materials. Moreover, the synergistic effect of graphene and TiO2 endows GTAs with excellent photocatalytic degradation and self-cleaning properties, which can effectively reduce the enrichment of contaminants on the evaporator. Therefore, GTA evaporators can efficiently and stably obtain clean water from seawater and wastewater, which provides a feasible strategy for the purification of complex wastewater.

Salt transport dynamics across the sediment-underground brine interface driven by tidal hydrology and benthic crab burrowing in muddy tidal flats

Muddy coasts with burrows are widespread globally and most contain brine in underground aquifers. Salt evaporated on a tidal flat surface is an important source of shallow underground brine (phreatic brine and brine in the top layer). However, the salt accumulation/release process in shallow underground brine during tidal cycles remains unclear. To analyze the abovementioned process, sediment permeability and pore-water parameters are measured, and electrical resistivity tomography and ring electrode resistivity probe monitoring are conducted in a tidal flat on the south bank of Laizhou Bay, China, where underground brine occurs and biological activities are pronounced. The results show that evaporated salt on the surface of tidal flats and offshore high-salinity underground brine are the two salt sources of shallow underground brine in tidal flats. Dense burrows and large tidal ranges can accelerate the rate of salt cycling, and promoting the exchange of surface and deep salt through the top layer. During the flooding tide, shallow underground brine is primarily replenished by evaporated salt on the beach surface. In areas with dense burrows, some evaporated salt on the beach surface can pass through the top layer to recharge the phreatic brine. During the ebbing tide, the salt in layers U and B is released into seawater and phreatic brine, respectively. When seawater recedes from the beach surface, a trace amount of phreatic brine and salt in the top layer is released to the beach surface via an upward flow field. Layers U and B are the main areas of salt accumulation and release. The proportion of salt accumulation/release in layer M is the lowest; however, layer M is the most susceptible to salt accumulation and features the highest pore-water salinity among the top layers.

3D Cellular Solar Crystallizer for Stable and Ultra-Efficient High-Salinity Wastewater Treatment.

Recent developed interfacial solar brine crystallizers, which employ solar-driven water evaporation for salts crystallization from the near-saturation brine to achieve zero liquid discharge (ZLD) brine treatment, are promising due to their excellent energy efficiency and sustainability. However, most existing interfacial solar crystallizers are only tested using NaCl solution and failed to maintain high evaporation capability when treating real seawater due to the scaling problem caused by the crystallization of high-valent cations. Herein, an artificial tree solar crystallizer (ATSC) with a multi-branched and interconnected open-cell cellular structure that significantly increased evaporation surface is rationally designed, achieving an ultra-high evaporation rate (2.30kgm-2 h-1 during 2h exposure) and high energy efficiency (128%) in concentrated real seawater. The unit cell design of ATSC promoted salt crystallization on the outer frame rather than the inner voids, ensuring that salt crystallization does not affect the continuous transport of brine through the pores inside the unit cell, thus ATSC can maintain a stable evaporation rate of 1.94kgm-2 h-1 on average in concentrated seawater for 80h continuous exposure. The design concept of ATSC represents a major step forward toward ZLD treatment of high-salinity brine in many industrial processes is believed.

Study of calcium carbonate scaling on steel using a high salinity brine simulating a pre-salt produced water

In Brazilian pre-salt production, high carbon dioxide (CO2) levels in the associated gas, high salinity in the water, and high levels of calcium ions cause problems related to corrosion and scale. In practice, the scaling process already begins in the formation and near the wellbore region. However, this work has addressed this issue only on a steel surface, representing what can occur in oil production tubings and equipment since the build-up of these products in the internal walls can also impact the production flow guarantee. Parameters related to the substrate and the environment can influence calcium carbonate (CaCO3) precipitation mechanisms. In this study, the effect of steel surface roughness on calcium carbonate scaling experiments has been studied in a high salinity brine containing sodium bicarbonate (NaHCO3) and calcium chloride (CaCl2), simulating pre-salt produced water and under flow conditions. The scaling tests were carried out with a set-up composed of a peristaltic pump to recirculate the test solution through a flow cell. The scale build-up was analysed by using techniques such as Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersion X-ray Spectroscopy (EDS). For tests carried out in 3 h, the smoother surfaces had lower adhesion of calcium carbonate than surfaces with higher roughness. Lepidocrocite and rokuehnite, which are corrosion products, were formed in the substrates with higher roughness values, promoting aragonite formation. This work demonstrates that roughness influences calcium carbonate scale formation under flow conditions, besides affecting the calcium carbonate polymorphs associated with the corrosion process.

Pilot plant evaluation of membrane distillation for desalination of high-salinity brines

Membrane distillation (MD) is a hybrid thermal-membrane desalination process that can use either low-grade waste heat and/or solar energy with hydrophobic membranes to desalinate high-salinity brines and produce high quality distillate. A research consortium was launched to investigate the application of the MD process, at lab and pilot scale, for desalination of concentrated brines. Bench scale results showed the presence of antiscalants in the concentrated brines minimized the scale precipitation potential and offered stable membrane permeability performance. Various MD technologies were screened, and two suitable technologies were selected for field-testing. Pilot unit A was based on multi-effect vacuum showed a stable flux of 6.2 LMH with excellent salt rejection (> 99.9%) from the concentrated brine discharged from thermal desalination plant in Qatar. That pilot unit was also field tested on hypersaline groundwater in Texas (USA) to generate fresh water for reservoir fracking in unconventional oil production operations. The MD unit was coupled with humidification/dehumidification (HDH) unit to achieve zero liquid discharge (ZLD) for inland applications. The MD unit was operated at 40% recovery producing distillate of < 20 mg/L total dissolved solids (TDS) and observed a stable flux of 5 LMH. Key challenges that are critical for large-scale deployment of MD technology were identified at the end of the field-testing program. Finally, a review of active MD technologies was conducted to highlight recent promising developments for full-scale applications.

Ionization Engineering of Hydrogels Enables Highly Efficient Salt-Impeded Solar Evaporation and Night-Time Electricity Harvesting

HighlightsAn ionization-engineered hydrogel with electronegativity polymer chains to impede salt ions was designed.The hydrogel evaporator exhibited salt impedance in 20 wt% brine for 15 days with a high evaporation efficiency of 95.6%.An all-day high-salinity brine treatment with zero liquid discharge was proposed.

How does the presence of an oleic phase influence salt transport during polymer-enhanced low-salinity waterflooding?

Our preceding single-phase experiments demonstrated that polymer enhanced low-salinity waterflooding (PELS) can significantly reduce salt dispersion and improves low-salinity waterflooding (LSWF) performance. In this paper, we extended the research to two-phase fluid flow conditions in the presence of an oleic phase. To assess this quantitatively, a series of two-phase coreflooding experiments using artificial cores were conducted. To eliminate the impact of fluid–fluid and rock–fluid interactions associated with LSWF on salt dispersion, a model, non-polar oleic phase was chosen. The salinity breakthrough results of two-phase corefloods were interpreted using a non-Fickian model based on the Mobile-Immobile Model to infer salt dispersion coefficient. The impact of Partially-Hydrolyzed Polyacrylamide (HPAM) concentration, injection rate, salinity difference, and flooding mode (secondary or tertiary) on salt transport and dispersion through porous media were studied. The results revealed an increase in the salt dispersion coefficient under two-phase conditions by as much as sixfold; taking significantly larger times to displace the high salinity brine. Thus, the optimal HPAM concentration required to effectively suppress mixing was found to be twice (∼400 ppm) as much under the single-phase flow. Reduction of salinity difference also resulted in the reduction of the salt dispersion coefficient by 32%. Moreover, it was observed that in tertiary mode injection where the starting water saturation of the core is higher due to a prior high salinity flooding, the salt dispersion can be increased by more than 21%. These new two-phase results and insights support the possibility of mixing-control under two-phase condition by using PELS and provides a solution to facilitate field implementation.

Investigation of the Effect of Residual Oil and Wettability on Sulfonated Polymer Retention in Carbonate under High-Salinity Conditions

Summary Polymer flooding in carbonate reservoirs is greatly affected by polymer retention, which is mainly due to adsorption by polymer-rock surface interactions. Consequently, this leads to a delay in polymer front propagation and related oil recovery response. This work investigates the effects of residual oil (Sor) and wettability on sulfonated-based (ATBS) polymer retention under the conditions of high salinity and moderate temperature. Polymer single- and two-phase dynamic adsorption tests as well as bulk and in-situ rheological experiments were conducted on outcrop carbonate cores in the presence of a high-salinity brine of 243,000 ppm at a temperature of 50°C. A total of four corefloods were conducted on Indiana limestone core samples with similar petrophysical properties. Overall, polymer adsorption was found to be low and within the acceptable range for application in carbonate reservoirs in the absence and presence of Sor. Furthermore, the polymer adsorption and in-situ rheology tests highlighted the significance of oil presence in the core samples, where retention was found to be around 40–50 µg/g-rock and 25–30 µg/g-rock in the absence and at Sor, respectively. An additional 50% reduction in retention was observed on the aged core sample that is more oil-wet. Polymer retention/adsorption was measured by double slug and mass balance techniques, and the results from both methods were in agreement with less than 7% difference. Inaccessible pore volume (IPV) was also calculated based on the double slug method and was found to be in the range of 23% to 28%, which was qualitatively supported by in-situ saturation monitoring obtained from an X-ray computed tomography (CT) scanner. The ATBS-based polymer showed excellent results for applications in carbonate without considerable polymer loss or plugging. This paper provides valuable insights into the impacts of residual oil and wettability on polymer adsorption, supported by CT in-situ saturation monitoring, which is necessary to avoid unrepresentative and inflated polymer retentions in oil reservoirs.

Bioinspired multi-scale core-spun yarn-based solar evaporator for ultra-efficient and durable high-salinity brine desalination

Solar-driven interfacial desalination has been considered a promising and green technology for relieving worldwide water shortage because of its zero carbon emission. However, salt accumulation during evaporation results in a significant reduction in solar evaporation performance and sustained service life. High-performance and long-term salt-rejecting solar evaporators are urgently desirable. Inspired by the rapid water transfer driven by leaf transpiration and the capillary pressure in woody plants, we developed electrospun polyacrylonitrile (PAN) @carbon nanotubes (CNTs) nanofiber/cotton core-spun yarn (PCCS yarn) based solar evaporator enabled by the multi-branch microchannels and sub-microchannels for ultra-efficient and durable high-salinity brine desalination. The optimal PCCS yarn-based solar evaporator exhibits a record-high evaporation rate of 3.46 kg m−2h−1 under one sun illumination among 2D evaporators. Meanwhile, an excellent and stable brine desalination rate of ∼2.75 kg m−2h−1 for 100 h continuous solar irradiation is achieved even in 20wt% NaCl solution. The above results are attributed to the massive micro evaporation surfaces formed between nanofibers, rapid water replenishment in the radius direction, and orientational fast water transport by Laplace pressure along and across the PCCS yarn. In addition, the continuous preparation of the core-spun yarn by the conjugated electrospinning technology and the complete fabric production process in the textile industry make it possible for the practical application of the PCCS yarn-based solar evaporator. This work promotes the development of high-performance, long-term and scalable solar desalination devices.

Natural multiscale channeled salt resistant solar evaporator for efficient and long-term water desalination

Solar steam evaporation exhibits great potential in solving the global shortage of freshwater resources. However, salt accumulation at the top photothermal conversion surface has severely limited the desalination efficiency and stability of solar desalination systems. Herein, we demonstrated a nature-inspired salt resistant bilayered evaporator by using a slight delignificated tree root as bottom substrate and decorated graphene oxide layer as the top absorber surface. The naturally design of tree root inherently exists multilevel vertical channels interconnected porous microstructures. This distinctive structure of tree root allows ultra-high-speed water transport capability and rapid multi-directional salt exchange, enabling it to possess anti-salt-accumulation properties for solar steam generation. This designed tree root-based evaporator effectively prevented salt accumulation while maintaining a fast and stable evaporation rate, which exhibited an evaporation rate of 1.60 kg m−2 h−1 with excellent long-term stability in a high-salinity brine (21 wt%) under 1 sun irradiation. Taking the unparalleled advantages, our designed tree root-based evaporator obtained by a facile fabrication method represents a high-efficacy and stable fresh water production platform for practical applications in water purification.

Analysis of Economic Benefits of Using Deep Geological Storage Technology to Treat High-Salinity Brine in Coal Mines

Some provinces in China require zero discharge of coal mine wastewater, with a focus on the disposal of high-salt water, because evaporation ponds have been completely banned. Deep geological storage (DGS) technology is a novel geological environment solution that uses rock pores and microfissures within deep strata for safely storing liquid or gas to avoid its environmental impact on the biosphere. The author and his research team were the first to put forward the research idea of using DGS technology to dispose of high-salinity brine in coal mines in China and performed related research. Taking a coal mine in the south of Ordos Basin as an example, this study designed a conventional, mine-specific, zero-discharge water treatment process route based on a evaporation–crystallization process. This strategy was tailored to the unique water inflow conditions of the mine. Furthermore, the technical and economic efficiencies were assessed for the generation and treatment scenarios of a four-stage highly concentrated brine solution. In addition, the comparative analysis of the economic prospects of using DGS technology to treat high-salinity brine revealed that combining DGS with post-conventional treatment in secondary reverse osmosis, whose flow quality is 481 m3/h and TDS is 24,532.66 mg/L, can maximize the economic benefits. This integration heightened water resource utilization while maintaining a cost-effective, comprehensive water treatment approach. These results provide a valuable reference value for the future zero-discharge treatment of coal mine water.