Membrane Distillation Technology Research Articles

A Janus membrane with silica nanoparticles interlayer for treating coal mine water via membrane distillation

The use of membrane distillation (MD) technology to treat coal mine water content has great potential, and the Janus membrane is very resistant to scaling and wetting during MD. In this work, SiO2 nanoparticles were electrostatically adsorbed onto the surface of a polyvinylidene fluoride (PVDF) membrane, followed by the construction of a polyamide (PA) layer through interfacial polymerization (IP). The intermediate layer of SiO2 nanoparticles can promote the enrichment of amine monomers during the subsequent IP process as well as slow its entry into the organic phase to regulate the PA layer. The addition of SiO2 nanoparticles was increased from 0 to 0.10 %, and the thickness of the polyamide layer was also reduced from 225.1 nm to 102.3 nm. Compared with the original membrane vapor flux of 40.9 ± 1.0LMH, the modified membrane vapor flux slightly increased to 46.2 ± 0.9LMH, but excessive SiO2 nanoparticles blocked the membrane pore, resulting in a decrease in flux. MD experiments show that the Janus membrane is wettability and scaling resistance when passing through the salt solution containing sodium dodecyl sulfate (SDS) surfactant or simulated wastewater as feed. At the same time, the interface thermodynamics of the simulated wastewater and the membrane are calculated to understand the anti-scaling mechanism of the membrane, offering a theoretical foundation for the application of real mine water.

Evaluating the feasibility of direct contact membrane distillation and nanofiltration in ground water treatment through a techno-economic analysis

This study delves into the realm of water treatment by conducting a comprehensive techno-economic evaluation of direct contact membrane distillation (DCMD) and nanofiltration (NF) processes. While previous research has explored the technical aspects of membrane distillation (MD) and nanofiltration, there remains a notable gap in economic analyses. Our research aims to bridge this gap by assessing the financial feasibility of employing MD and NF technologies for water desalination. Specifically, we scrutinize the performance of hydrophobic microporous flat sheet membranes crafted from polytetrafluoroethylene (PTFE) supported by non-woven polypropylene (PP) in desalinating brackish water through DCMD and NF processes. By varying operating conditions such as flow rate and feed temperature, we evaluate the membrane's efficacy. Employing an analytical model based on heat and mass transfer equations, we predict process performance across diverse scenarios. Our model demonstrates a high level of accuracy, with flux predictions deviating by less than 10% when utilizing the Knudsen-molecular mechanism model. Furthermore, through a detailed design and economic analysis of industrial-scale units for both processes, we reveal that the cost of permeated water is lower with NF compared to DCMD. Specifically, our calculations indicate a water cost of 1.34 USD/m3 for DCMD at a feed temperature of 65 °C with an 80% recovery rate, positioning it as a competitive option among conventional desalination methods. Notably, our financial assessment highlights that steam cost constitutes the primary expense in DCMD operations, contingent upon heating value and fuel prices. Noteworthy findings suggest that natural gas emerges as the most cost-effective fuel for steam production in a DCMD plant. This study underscores the economic viability and potential cost efficiencies associated with NF over DCMD in water treatment applications.

A cost-effective and high efficient Janus membrane for the treatment of oily brine using membrane distillation

Membrane distillation technology could utilize low-grade heat to desalinate brine, but the membrane material often suffers from disadvantages of low permeation flux and weak robustness to contaminants. To address these issues, the commercial polytetrafluoroethylene (PTFE) membrane was modified by cost-effective chemicals of tannic acid and (3-Aminopropyl)-triethoxysilane (APTES) to construct hydrophilic/underwater superoleophobic nano-rough structures on the surface to enhance its flux and oil-fouling resistance in direct contact membrane distillation. The results show that a high underwater oil contact angle of 180° is observed to the membrane surface due to the rough nanostructures functionalized by abundant hydroxyl groups. Despite the additional mass transfer resistance provided by the rough nanostructures, the flux was increased noticeably. This is mainly attributed to the strong interactions between the abundant hydroxyl groups of hydrophilic layer surface and water molecules, leading to a part of free water staying at intermediate transition state (IW). The mass transfer resistance of the hydrophilic layer itself is reduced as a consequence of decreased evaporation enthalpy of water, thereby increasing the flux. Moreover, while the flux of the pristine membrane is reduced by 84.18%, the flux of Janus membrane remains the same when treating mineral oil brine emulsions with oil concentration up to 1500 ppm in comparison with the result for 35 g l−1 brine solution, indicating that the Janus membrane is safe from the oil contamination. Our work provides a fine guidance for membrane distillation to treat high oily brine.

New insights into antifouling property and interfacial mechanism in photo-Fenton membrane distillation

Membrane distillation (MD), boasting high interception efficiency and low operational pressures, emerges as an innovative membrane technology. However, the occurrence of membrane fouling due to interaction between natural organic matter (NOM) and inorganic ions during the MD process curtails water purification efficiency, thereby constraining its potential applications. To address this quandary, this study integrates sulfate radical-based advanced oxidation processes (SR-AOPs) into MD technology to bolster membrane fouling control. A straightforward hydrothermal method coupled with vacuum filtration was employed to synthesize a Co3O4/Nitrogen-modified carbon quantum dots (NCDs)/PVDF (CN-PVDF) membrane for the first time, which was utilized in the MD treatment of simulated humic acid (HA) wastewater. Under visible light irradiation (1.9 kW/m2), CN-PVDF membrane activation of peroxymonosulfate (PMS) effectively altered the chemical attributes of the MD feed solution and reduced organic matter concentration. Moreover, it dismantled the carboxyl sites on HA that interact with Ca2+, consequently attenuating the formation of organic–inorganic complex pollutants. The XDLVO analysis showcased that photo-Fenton oxidation led to a diminishment in pollutant hydrophobicity, correlating with a 17.59 kT reduction in pollutant-membrane adsorption and a 7.47 kT amplification in adhesion barriers. This strategy transformed the initial two-stage fouling mode into a singular one, which significantly decreased the flux decline and the fouling layer thickness. Furthermore, the CN-PVDF membrane demonstrated self-cleaning capabilities via photo-Fenton. This study advances an innovative approach to bolster the fouling resistance of MD membranes and provides substantial theoretical support for the integration of SR-AOPs and MD technologies.

Freshwater and minerals recovery from synthetic produced water by membrane distillation/membrane crystallization processes

The purpose of this work is to study the influence of oil and surfactant present in produced water on the membrane distillation and membrane crystallization performance. The latter is evaluated in terms of permeate flux, quality of permeate and sodium chloride crystallization kinetics. Polypropylene and Hyflon AD40H/PVDF composite membranes with 0.2 μm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm{\\mu m}$$\\end{document} pore size were used in the investigation. The tests were carried out in direct contact configuration using two synthetic feed solutions: the first one without oil and surfactant, and the second one with oil and surfactant. The achieved results showed a permeate flux reduction of 20 and 40% for PP and AD40H, respectively, in membrane distillation and of 35% in membrane crystallization. These results may be attributed to the interaction between the salts and surfactant, which led to the deterioration of the membrane performance. Despite this, high salt rejection factors greater than 99.9% and total carbon rejections ranging between 80 and 90% indicated the good potential of membrane distillation technology for the treatment of produced water. Moreover, good quality crystals and high total water recovery factor (97%) were achieved using the membrane crystallization process. Nevertheless, the presence of oil and surfactant in the feed caused an increase in the induction time compared to the system without oil and surfactant. In addition, in the performed experiments, simple physical cleaning with distillate water was sufficient to recover the initial trans-membrane flux of the membranes.

High performance bimetallic ZIF-CoZn@PVDF-HFP composite nanofiber membrane for membrane distillation based on coaxial electrospinning technology

Membrane Distillation (MD) technology stands out for its cost-effectiveness and sustainability in diverse applications, such as high-salinity wastewater treatment and seawater desalination. However, conventional MD membranes frequently encounter challenges associated with inadequate permeate flux and insufficient anti-wetting performance. In the present study, we fabricated a series of ZIF-CoZn@PVDF-HFP composite nanofiber membranes with a core–shell structure via coaxial electrospinning. Here, PVDF-HFP functions as the core, while a blend of bimetallic Zeolitic imidazolate framework ZIF-CoZn nanoparticles and PVDF-HFP constitutes the shell. Through the utilization of the coaxial technology, functional nanoparticles achieve uniform and stably dispersed on the nanofiber surface, leading to the creation of a secondary rough structure in addition to the inherent roughness of single-nozzle electrospinning. This results in a surface with a 3D-hierarchical structure. The significantly amplifies the evaporation area on the surface of the composite nanofiber membrane, thereby bolstering the permeate flux in the MD process. Additionally, the incorporation of bimetallic ZIF-CoZn nanoparticles, recognized for their superior hydrophobicity and low thermal conductivity, improves the anti-wetting and heat-insulating properties of the composite nanofiber membrane, further advancing permeate flux performance. Using a 35 g L−1 NaCl as the feed solution, the optimal 1 % ZIF-CoZn@PVDF-HFP composite nanofiber membrane demonstrated a permeate flux of 21.8 L m−2 h−1, coupled with a salt rejection rate exceeding 99.9 %. Even during long-term MD testing, it maintained excellent insulation and anti-wetting capabilities. Our research offers a convenient and effective approach for fabricating anti-wetting composite nanofiber membranes.

Microelectronics firm harnesses environmental benefits of Memsift's MD technology

In Singapore, a microelectronics company is using membrane distillation (MD) technology developed by Memsift Innovations Pte Ltd for sustainable nickel recovery.

Molecular insights into the adsorption and penetration of oil droplets on hydrophobic membrane in membrane distillation

Membrane fouling induced by oily substances significantly constrains membrane distillation performance in treating hypersaline oily wastewater. Overcoming this challenge necessitates a heightened fundamental understanding of the oil fouling phenomenon. Herein, the adsorption and penetration mechanism of oil droplets on hydrophobic membranes in membrane distillation process was investigated at the molecular level. Our results demonstrated that the adsorption and penetration of oil droplets were divided into four stages, including the free stage, contact stage, spreading stage, and equilibrium stage. Due to the extensive non-polar surface distribution of the polytetrafluoroethylene (PTFE) membrane (comprising 95.41 %), the interaction between oil molecules and PTFE was primarily governed by van der Waals interaction. Continuous oil droplet membrane fouling model revealed that the new oil droplet molecules preferred to penetrate into membrane pores where oil droplets already existed. The penetration of resin (a component of medium-quality oil droplets) onto PTFE membrane pores required the “pre-paving” of light crude oil. Finally, the ΔE quantitative structure-activity relationships (QSAR) models were developed to evaluate the penetration mechanism of pollutant molecules on the PTFE membrane. This research provides new insights for improving sustainable membrane distillation technologies in treating saline oily wastewater.

Review of Hybrid Membrane Distillation Systems.

Membrane distillation (MD) is an attractive separation process that can work with heat sources with low temperature differences and is less sensitive to concentration polarization and membrane fouling than other pressure-driven membrane separation processes, thus allowing it to use low-grade thermal energy, which is helpful to decrease the consumption of energy, treat concentrated solutions, and improve water recovery rate. This paper provides a review of the integration of MD with waste heat and renewable energy, such as solar radiation, salt-gradient solar ponds, and geothermal energy, for desalination. In addition, MD hybrids with pressure-retarded osmosis (PRO), multi-effect distillation (MED), reverse osmosis (RO), crystallization, forward osmosis (FO), and bioreactors to dispose of concentrated solutions are also comprehensively summarized. A critical analysis of the hybrid MD systems will be helpful for the research and development of MD technology and will promote its application. Eventually, a possible research direction for MD is suggested.

Mathematical and computational modeling of membrane distillation technology: A data-driven review

Membrane distillation (MD) technology is increasingly gaining attention as an environmentally sustainable water treatment method of emerging interest. During last three decades there has been wide efforts to model and improve the performance of this technology. In this study we examine both the mathematical and computational modeling methods used in MD with a data-driven method. To gather the dataset, a broad range of terms related with theoretical modeling of MD were searched in the Scopus database. The collection consists of 526 documents including 116 journals, 14,291 references used by authors, 1252 involved authors and 29.47 % international co-authorship rate. The overall pattern of publications is found to increase over time indicating the enhancing interest on theoretical modeling of MD process. Journal of Membrane Science and Desalination are the top two journals publishing theoretical modeling of MD, with 105 and 100 articles, respectively. Dr. Ghaffour N. contributed with the highest number of articles, 24; and Dr. Khayet M. has the highest articles fractionalized value with 7.08. The dataset was categorized first into mathematical and computational modeling, then into the used mass transport approaches through membrane hydrophobic pores. Recently, in MD field computational modeling has been considered more than mathematical modeling. The combined Knudsen diffusion/ordinary molecular diffusion model is the dominant mass transport approach considered in MD mathematical modeling with 117 articles. On the other hand, computational fluid dynamics is the most used computational method with 114 articles.

Wetting-and scaling-resistant superhydrophobic hollow fiber membrane with hierarchical surface structure for membrane distillation

In this study, we address the challenge of wetting and scaling in membrane distillation (MD) by developing a robust superhydrophobic poly(vinylidene fluoride) (PVDF) hollow fiber membrane. To achieve this, we utilized co-extrusion technology and subsequent fluorination treatment to create micro-nanoscale surfaces. The fabrication process involved extruding a SiO2 suspension onto the outermost layer of a triple-orifice spinneret to create a hierarchical structure, followed by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FAS) modification to lower the membrane surface energy. This resulted in a highly water-repellant membrane, as evidenced by contact angle measurements of 153°, 147°, and 141° for water, sodium dodecyl sulfate (SDS) solution (0.4 mM), and saline SDS solution (0.4 Mm SDS and 35 wt% NaCl), respectively, indicating increased resistance to liquid penetration. Through direct contact membrane distillation (DCMD) experiments, we demonstrated that the PVDF/FAS membrane exhibited excellent wetting resistance to seawater (3.5 wt% of NaCl) with SDS at varying concentrations. Furthermore, the membrane effectively hindered the CaSO4 scaling by reducing both heterogeneous nucleation and the tendency of bulk crystal deposition on the membrane outer surface. Overall, the developed approach for fabrication of superhydrophobic PVDF hollow fiber membrane presents a promising solution for facile and scalable manufacturing of anti-wetting and anti-scaling MD membranes. This advancement has significant implications for enhancing the practical application of MD technology.

Scalable Carbon Black‐Enabled Membranes for Sustainable Solar Membrane Desalination

AbstractSolar energy is used worldwide for generating electricity or desalting seawater. Photothermal membrane distillation (PMD), an emerging thermal‐driven process for seawater desalination, combines interfacial heating with membrane distillation (MD) technology to address the energy consumption issues of conventional MD. However, it is still a great challenge to develop a cost‐effective and scalable membrane, which hampers the practical use of PMD. Herein, a dual‐layer carbon black (CB)/PVDF membrane is prepared via direct electrospraying on a commercial PVDF membrane. With the introduction of a functional layer, a photothermal effect is imparted to the bare membrane, thus significantly increasing the water production rate and solar utilization efficiency (SUE) during exposure to artificial sunlight (≈57% enhancement and 72% SUE under 1 sun). In addition to the outstanding photothermal properties, this functional layer also served as a passivation coating to synergistically reduce the crystallization rate and physical binding of inorganic salts on the modified membrane without adding hazardous chemicals or using laborious steps. This multifunctional coated membrane and fast‐growing solar desalination technology provides a promising solution to the water crisis, especially in off‐grid areas where energy and resources are both relatively insufficient.

Multifunctional photocatalytic membrane distillation for treatment of hypersaline produced water using hydrophobically modified tubular ceramic membranes

Produced water (PW) is the subsurface water brought to the surface during oil and gas production. PW is primarily disposed of by deep well injection, but it can be treated for beneficial use applications. However, efficient technologies for treating hypersaline PW with complex water chemistry are limited. This study developed an innovative, multifunctional photocatalytic membrane distillation (PMD) technology using hydrophobically modified tubular ceramic membranes coated with TiO2 nanoparticles as photocatalysts for treating unconventional PW. The effects of membrane modifications were characterized in terms of membrane morphology, pore size, chemical functionality, zeta potential, hydrophobicity, liquid entry pressure, water production, permeate water quality, and membrane fouling and scaling propensity. The desalination performance of the PMD technology was demonstrated using unconventional PW with total dissolved solids concentrations of 135,000 mg/L and 175,000 mg/L, and NH3-N concentrations of 1551 mg/L and 613 mg/L, respectively. The novel PMD concept provides a promising technology for hypersaline PW treatment, and TiO2 coating significantly reduced membrane fouling and scaling, improved distillate quality, and maintained stable permeate flux. The photocatalyst activation by ultraviolet-light emitting diodes (UV-LED) light further increased the permeate flux and enhanced the total organic carbon removal from 82.0% (without UV-LED) to 89.7% (with UV-LED). UV-LED irradiation did not affect ammonia and metals removal in PMD, reaching 99.4% and > 99.99% removal, respectively.

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.

A Comparative Analysis of Pervaporation and Membrane Distillation Techniques for Desalination Utilising the Sweeping Air Methodology with Novel and Economical Pervaporation Membranes.

This study used the sweeping air approach to conduct a comparative analysis of pervaporation (PV) and membrane distillation (MD) in the context of desalinating saline/hypersaline water. An experimental setup of the sweeping air arrangement was designed and built at a laboratory size to conduct the research. The desalination process using PV used innovatively designed cellulose acetate (CA) membranes specifically adapted for this purpose. Conversely, in the studies involving MD, hydrophobic polytetrafluoroethylene (PTFE) membranes were utilised. CA membranes were fabricated in our laboratory using the phase inversion approach. The physicochemical characteristics of the membranes were assessed using many methodologies, including FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle measurement, and water uptake analysis. This facilitated a more comprehensive comprehension of the impact of the alkaline treatment on these features. The variables that were examined included the kind of membrane, the pore size of the PTFE membrane, the composition of the casting solution of CA, the concentration of the feed solution, the temperature of the feed, and the temperature of the condenser cooling water. The morphologies of the membranes were examined using SEM. The study's findings indicated that the use of MD resulted in a greater flow and a remarkable percentage of salt rejection (% SR). Furthermore, it was observed that the flux was positively correlated with the feed temperature, while it exhibited an inverse relationship with the cooling water temperature. Moreover, it was observed that the impact of the pore size of the PTFE membrane on the desalination process was found to be minimal. The most optimal outcomes obtained were 13.35 kg/m2 h with a percentage salt rejection (% SR) of 99.86, and 17.96 kg/m2 h with a % SR of 99.83 at a temperature of 70 °C, while using MD and PV technologies, respectively. Furthermore, both methods demonstrated the capability to desalinate very salty solutions with a salinity level of up to 160 g/L, thereby yielding potable water in a single step.

Efficient purification of high-salt rural groundwater in the areas along the Yellow River in Henan Province, China, by hollow fiber membrane distillation process

The vast rural drinking water sources along the Yellow River basin in Henan Province mainly come from the local high-salinity groundwater, which cannot be directly drunk. Zeolitic imidazolate framework-71/polyvinylidene fluoride hollow fiber composite membrane was applied to treat rural groundwater through membrane distillation technology. The variations of water quality parameters from 12 different rural regions after membrane distillation treatment were well analyzed and compared. Membrane separation performance for water samples from different regions during the membrane distillation process was investigated, including water flux and salt rejection. During a continuous 24-h membrane distillation process for the treatment of these water samples, hollow fiber membrane exhibits high solute retention rates (&gt;99%) for salt ions, suspended solids and total dissolved solids, which are within the limits of national standards (GB 5749-2006), meanwhile membrane permeation water flux can remain stable. After the acid-cleaning for 180 min, all hollow fiber membranes can recover water flux well with a flux recovery rate above 98%. Even if the concentration ratio continued to increase, the water production rate of membrane distillation was basically maintained between 50% and 60%, which was obviously higher than the 30% of the reverse osmosis process. The economic analysis confirmed that the water production cost varied between US$0.45 and US$0.29/m3. With the extension of membrane service life, the specific membrane cost decreased rapidly in the first 6 years and then leveled off. The proposed vacuum membrane distillation process proved to be a promising water purification method for treating rural high-salinity groundwater.

Numerical Modelling and Performance Evaluation of Vacuum Membrane Distillation for Energy-Efficient Seawater Desalination: Towards Energy-Efficient Solutions

Vacuum membrane distillation (VMD) is a compelling technique for desalinating water because it exhibits superior pure water permeability at lower operating temperatures compared to other membrane distillation technologies. This leads to reduced energy consumption, lower heat loss via conduction across the membrane surface, and minimal heat transfer through conduction due to the low pressure on the permeate side. Detailed modelling of heat and mass transfer in VMD is essential for optimizing the process as it provides valuable insights that contribute to the advancement and successful implementation of seawater desalination using VMD technology. The aim of this study is to establish a comprehensive numerical model that describes the water vapor transfer across a hydrophobic micro-porous membrane in single-stage and multi-stage VMD processes for seawater desalination. The numerical predictions were compared to experimental data in addition to numerical computations based on an existing literature database, and good agreement has been found. The investigation also conducted a sensitivity analysis of process variables and membrane specifications on the VMD performance, as well as an assessment of the impact of temperature and concentration polarization. The obtained results showed that the permeation flux reached 18.42 kg/m2·h at 35 g/L feed concentration, 65 °C feed temperature, 50 L/h feed flow rate, and 3 kPa vacuum pressure. Moreover, the findings revealed that the feed temperature was the most significant factor, while the feed flow rate was the least important in determining the permeation flux. Additionally, the findings suggested that the effectiveness of the VMD process heavily relies on the composition and permeability of the support materials. Finally, the results confirmed that temperature polarization had a more significant effect on the reduction of the permeate flux than the concentration polarization.

Experimental and Simulation Study of Solar-Powered Air-Gap Membrane Distillation Technology for Water Desalination.

This work aimed to investigate temperature polarization (TP) and concentration polarization (CP), which affect solar-powered air-gap membrane distillation (SP-AGMD) system performance under various operating conditions. A mathematical model for the SP-AGMD system using the experimental results was performed to calculate the temperature polarization coefficient (τ), interface temperature (Tfm), and interface concentration (Cfm) at various salt concentrations (Cf), feed temperatures (Tf), and flow rates (Mf). The system of SP-AGMD was simulated using the TRNSYS program. An evacuated tube collector (ETC) with a 2.5 m2 surface area was utilized for solar water heating. Electrical powering of cooler and circulation water pumps in the SP-AGMD system was provided using a photovoltaic system. Data were subjected to one-way analysis of variance (ANOVA) and Spearman's correlation analysis to test the significant impact of operating conditions and polarization phenomena at p < 0.05. Statistical analysis showed that Mf induced a highly significant difference in the productivity (Pr) and heat-transfer (hf) coefficients (p < 0.001) and a significant difference in τ (p < 0.05). Great F-ratios showed that Mf is the most influential parameter. Pr was enhanced by 99% and 146%, with increasing Tf (60 °C) and Mf (12 L/h), respectively, at a stable salt concentration (Cf) of 0.5% and a cooling temperature (Tc) of 20 °C. Also, the temperature increased to 85 °C when solar radiation reached 1002 W/m2 during summer. The inlet heat temperature of AGMD increased to 73 °C, and the Pr reached 1.62 kg/(m2·h).

Experimental investigation of temperature polarisation by capturing the temperature profile development over DCMD membranes

Temperature polarisation (TP) is a major drawback limiting the global acceptance of membrane distillation (MD) technology. TP is typically quantified using a dimensionless index known as Temperature Polarisation Coefficient (TPC). TPC has significant limitations, whereby it cannot be used to compare different MD configurations or design conditions, nor to analyse the TP phenomenon along the membrane. In this research, the temperature profile over and along a lengthy DCMD membrane has been measured under various operational conditions, where its impact on TP has been explored for the first time. A specialised DCMD membrane cell was manufactured to capture temperature profiles, both along and over the membrane surfaces, using miniature thermocouples. The effects of flow rate and feed temperature were investigated on the temperature profiles. The results showed that the extent of TP was not constant along the membrane, and that the temperature profile was not symmetrical across the feed and permeate side, predominantly due to the effects of the inlet and outlet on the flow. The TPC value calculated using the conventional method was not able to accurately reflect the TP phenomenon along the membrane, indicating TPC to be an ineffective tool to study TP along the membrane.

Solar Thermal Technology Aided Membrane Distillation Process for Wastewater Treatment in Textile Industry—A Technoeconomic Feasibility Assessment

Because textile industries are intensely water-consuming and generate a huge quantity of wastewater, the present study examines the scope of using solar thermal technology to treat wastewater from textile industries. A hybrid technology, comprising a compound parabolic concentrator-based solar thermal system in conjunction with a Membrane Distillation (MD) system, is experimented with for wastewater treatment in textile industries. The MD system requires a water temperature of around 90 °C for efficient functioning. The advanced MD technology using waste heat combined with solar heat to meet the system’s thermal load is technologically evaluated for an experimental textile industry in India. Moreover, the present study critically analyses the techno economics of the proposed hybrid technology. A detailed financial analysis has revealed that, besides technological superiority, the recommended technology is also financially rewarding for wastewater treatment in the textile industry. To cope with the delayed payback period, financial incentives are recommended so that the system becomes a lucrative technological option.