Water Desalination Performance Research Articles

Molecular dynamics study on water desalination performance and related mechanism of hydrophobic α-Al2O3 ceramic membrane

With LAMMPS software, the non-equilibrium molecular dynamics (NEMD) simulations study was conducted for the membrane distillation process with the hydrophobic α-Al2O3 ceramic membrane (HCM). It could further help to explain the macroscopic laws and phenomena that appeared in the membrane distillation tests with HCM. In this study, the average temperature (Tr) of raw water and the negative pressure (Pcon) on the cold side of HCM were taken as the investigation variables to research the microscopic water desalination performance of HCM, transport/diffusion properties of water molecules, and related mechanisms. The results showed that the root means square displacement (MSD) of water molecules on the cold side of HCM positively changed with time by the linear trend. The height of the transmembrane energy barrier mainly depends on the atomic structure of the HCM. The diffusion type of free-state water molecules in the membrane micropores of HCM was the main ballistic-transport-like accompanied by rebound-jump. The influence level of Tr on the number of water molecules in the cold side of HCM was much greater than that of Pcon under the dynamic equilibrium state. The essential reason Tr determined the HCM molecular flux was that it changed the hydrogen bond lifetime in the microporous membrane of HCM.

Inositol hexaphosphate assisted polyamide thin-film composite membrane with ultrahigh performance for water desalination and dye fraction

Developing membranes with highly permeable and selective separation remains a challenge. Here, inositol hexaphosphate (IP6) was first introduced into the active layer for preparing an IP6 integrated polyamide (IP6PA) thin-film composite (TFC) membrane. The IP6PA TFC membrane possessed a thinner PA layer with a smoother and better hydrophilic surface as well as strengthened electronegativity and enlarged pore size. The IP6PA membrane that was prepared with a low IP6 content presented a high pure water flux of 20.5 LMH/bar (1.6 times higher than that of the control membrane), and a high Na2SO4 rejection rate (98.5 %), which could be used to completely remove typical dyes and natural organic matters. Notably, the IP6PA membrane fabricated with a high weight ratio of IP6 exhibited an ultrahigh water flux (111.7 LMH/bar) while maintaining superior rejections for Congo red (98.5 %), Direct red 23 (98.6 %), and Brilliant blue R250 (99.5 %). The results show that the modified membrane presented excellent performance in separation of organic/salts, particularly with its outstanding permeability and superior rejection rate, compared with those of most reported polymeric membranes. This work provides a new scheme for the rational design and manufacture of natural acid regulated polyamide composite membranes with enhanced performance for water treatment.

Remediation of saline oily water using an algae-based membrane

Petrochemical industry generates large amounts of oily wastewater that requires effective treatment methods. Among all, membrane filtration techniques have been receiving more attention, due to easy operation and low energy consumption. One of the issues is that the oily wastewater also contains high level of salinity. Thus, preparation of dual function membrane to be used for purification of saline oily wastewater is an attractive option. Inspired from fish scales, we prepared an underwater superoleophobic membrane using microalgae coated on steel mesh which can also be used in water desalination. In order to fix microalgae biofilm on the surface of steel mesh, PVA polymer and glutaraldehyde as crosslinking reagent was used. The salts can also be removed using microalgae biomass coated on steel mesh by the adsorption process. The prepared membrane demonstrated high efficiency (above 98%) for oil-water separation with the highest water flux of 30225.0 L m−2 h−1. Under optimized conditions, algae-based mesh exhibited salt rejection of (98.6 ± 0.5) %. Due to its simplicity, low cost and great performance in both oil-water separation and water desalination, the as-prepared membrane could find broad applications for commercial purposes.

Construction of oxygen defects in V2O5 for improved performance in Zn-ion battery and sea water desalination

Zn-ion battery has received researcher's interests for nonflammable and clean aqueous electrolyte, cheap and harmless Zn anode. Cathode material plays a vital role in Zn-ion battery, which can influence its performance directly. Because of suitable layer spacing, V2O5 has been considered as a potential cathode material for Zn-ion battery. But its prospect in Zn-ion battery is hindered by low conductivity. To resolve this problem, oxygen defect rich V2O5 (Od-V2O5) is synthesized. It possesses perfect stability when served as cathode material in Zn-ion battery. The specific capacity achieves 425 mAh·g−1 at 0.1 ​A ​g−1. Oxygen defect also prompts the separation of electron-hole pairs and makes more electrons participate in photothermal conversion, which boosts photo energy transforms to thermal energy. For Od-V2O5, it shows high photothermal effect efficiency. With Od-V2O5, photothermal membrane is fabricated with electrospinning technique and applied for solar steam generation sea water desalination. Evaporation rate of the membrane reaches 1.29 ​kg ​m−2 ​h−1 with energy conversion efficiency 88.1% under 1 sun irradiation. The energy efficiency keeps stable after continuous evaporation. In evaporated water, the concentration of Na+, K+ Ca2+ and Mg2+ can satisfy the standard of human drinking water. We expect Od-V2O5 has a bright prospect in Zn-ion battery and sea water desalination.

(Excellent Student Presentation Award) Activated Biomass Converted Carbon in High-Efficient Water Desalination By Capacitive Deionization

Porous carbon materials, utilized as electrodes in capacitive deionization (CDI), play an important role in water desalination. Currently, benefiting from the abundance, cheap, environmental-friendly, biomass converted carbon was selected as the carbon electrode. We study the salt adsorption properties of carbon materials prepared by biomass precursor such as wood, eggplant, etc. The as obtained biomass converted carbon was further processed with activation. Potassium hydroxide, as a chemical activation agent, was selected and reacted with biomass converted carbon at high temperature. The influence of activating agent-carbon ratio and activating temperature was investigated. Due to the natural porous morphology, the biomass converted carbon materials usually exhibit a large surface area and high electrical specific capacitance after carbonization. Taking advantage of these properties, biomass converted carbon materials own a good water desalination performance. Additionally, the salt adsorption property of activated biomass converted carbon usually has an obvious enhancement, which benefit from the creation of extra porous structure. Based on our experiment, the activated biomass converted carbon materials are excellent candidates to be utilized in further industrial water purification.

Binder-Free Wood Converted Carbon in Water Desalination By Capacitive Deionization

In recent years, the clean water crisis has become a significant environmental challenge. Thus, water desalination has intensified over the past decades. As an energy-efficient, environmentally friendly, economical, and easy-operate technique, capacitive deionization (CDI) has attracted enthusiasm, in which carbon materials play an important role in salt ion removal. Benefiting from the abundance and easy preparation properties, biomass converted carbon has obtained attention in water desalination by CDI. Because of natural porous structure, wood is chosen as the biomass carbon precursor and to study the water desalination performance: Binder-free wood converted carbon sheets were successfully converted from several species of natural wood, and further chemical activation was processed to enlarge the porous structure. We found the pine and balsa converted carbon have a comparable salt adsorption capacity with commercial activated carbon, and activated balsa exhibits an extraordinary improved adsorption performance. The promising results indicate that activated balsa is an excellent material for water desalination.

Heat recovery capacity and water desalination performance of passive solar vacuum tube distiller

The direct thermal distillation utilized the solar vacuum tube was a seawater desalination technology with quite a development potentiality. Therefore, an efficient passive solar vacuum tube distiller (P-SVTD) with a heat recovery function was developed in this paper, which realized the integration operation of raw water vaporization and high-temperature steam self-pressurization. It also had the character of simultaneously carrying out boiling vaporization and interfacial vaporization. The mechanisms of photo-thermal conversion and heat-mass transfer in the whole operation process of P-SVTD were analyzed. The theoretical calculation models of water yield (msh) and heat recovery rate (HRR) were presented. The water desalination performance, temperature level of recovered heat, and HRR of P-SVTD were measured to obtain the comprehensive photo-thermal conversion efficiency (HE) of P-SVTD. The results showed that the optimal depth ratio of the vapor–liquid interface to the vaporized-pressurized cavity was 0.9718. The water yield of P-SVTD was positively correlated with the total solar irradiance on the inclined plane by the trend of an exponential function. The average temperature level of recovered heat, HRR, and HE of P-SVTD were 74.30 °C, 28.68 %, and 87.43 %, respectively. And the rejection capacity (REJ), the decreased degree of conductivity, and the pH of P-SVTD were close to 100.00 %, 100.00 %, and 7.00, respectively, which showed excellent desalination capacity. The research provided solid technical and theoretical support for promoting the large-scale application of passive solar distillation technology.

Tailoring nanocomposite membranes of cellulose acetate/silica nanoparticles for desalination

Herein, the fabrication of cellulose acetate (CA) silica-based nanocomposite membranes via the dry-wet phase inversion procedure for water desalination was investigated. The modified and unmodified silica nanoparticles (MSNPs and SNPs) were prepared by the sol-gel technique. The effect of the SNPs and MSNPs was investigated on the CA membrane's properties and their performance for water desalination. The CA nanocomposite membranes were characterized to study their structure, hydrophilicity, and morphology. The fabricated nanocomposite membranes showed hydrophilic surface properties. The performance of reverse osmosis (RO) membranes was measured using a crossflow RO unit at 10 bar (1 bar = 0.1 MPa). The membrane with 10 mg of SNPs enhanced permeate water flux compared to the pristine CA membrane by 1.6 L/(m2·h). The effect of MSNPs on the nanocomposites' performance was lower than their counterpart in the case of adding SNPs. The membrane with 30 mg of MSNPs showed the highest permeate water flux among other nanocomposite membranes with a value of 35.7 L/(m2·h) at 24 bar.

NH2-CuO-MCM-41 covalently cross-linked multipurpose membrane for applications in water treatment: Removal of hazardous pollutants from water, water desalination and anti-biofouling performance

The current study was planned to fabricate a new set of membranes to target multiple application areas such as desalting, removal of micropollutants and antibiofouling performance. In-situ incorporated copper oxide to MCM-41 (CuO-MCM-41) was synthesized and amine (-NH2) functionalized by reacting with N1-(3-trimethoxy silylpropyl) diethylenetriamine (NTSDETA) yielding NH2–CuO-MCM-41. Different concentrations of NH2–CuO-MCM-41 were covalently cross-linked in polyamide active layer during interfacial polymerization (IP) between N, N′-bis(3-aminopropyl)ethylenediamine and terephthaloyl chloride (TPC) on polysulfone/poly ester terephthalate (PS/PET) support. The membranes were extensively characterized by Water Contact Angle (WCA), Scanning Electron Microscopy (SEM), Fourier Transform Infra-red (FTIR) spectroscopy, Energy Dispersive X-ray (EDX) analysis, Elemental mapping and Powder X-ray Diffraction (PXRD). From among the different versions of X-CuO-MCM-41/PA@PS/PET membranes, the 0.05%-CuO-MCM-41/PA@PS/PET membrane showed best performance in terms of rejecting a variety of salts, micropollutants and antibiofouling. The 0.05%-CuO-MCM-41/PA@PS/PET showed >98% rejection of MgCl2 and 78% rejection of caffeine with a permeate flux of 16 LMH at 25 bar. The 0.1-NH2-CuO-MCM-41inhibited S. aureus growth by 51.7%. Hence, the current strategy of membrane fabrication proved to be highly efficient for multipurpose applications in water treatment.

Graphene-Coated PVDF Membranes: Effects of Multi-Scale Rough Structure on Membrane Distillation Performance.

Graphene-coated membranes for membrane distillation have been fabricated by using a wet-filtration approach. Graphene nanoplatelets have been deposited onto PVDF membrane surfaces. Morphology and physicochemical properties have been explored to evaluate the changes in the surface topography and related effects on the membrane performance in water desalination. The membranes have been tested in membrane distillation plants by using mixtures of sodium chloride and humic acid. The multi-scale rough structure of the surface has been envisaged to amplify the wetting and fouling resistance of the graphene-coated membranes so that a better flux and full salt rejection have been achieved in comparison with pristine PVDF. Total salt rejection and an increase of 77% in flux have been observed for coated membrane with optimized graphene content when worked with NaCl 0.6 M (DCMD, ΔT ≈ 24 °C) over a test period of 6 h. The experimental findings suggest these novel graphene-coated membranes as promising materials to develop functional membranes for high-performing water desalination.

A Novel BiOCl Based Nanocomposite Membrane for Water Desalination

In this study, BiOCl based nanocomposites were used as photocatalytic membranes for a simulated study on water desalination in reverse osmosis membrane systems. Through molecular dynamic simulation, the molecular structure of BiOCl, BiOCl/Ag2S and BiOCl/Bi2O3 heterojunctions were designed and their electronic properties, mechanical properties, and membrane performance for water desalination were evaluated for the first time. The molecular structure was created, and a geometry optimization task was used to optimize it. Material Studio 2019 CASTEP was used for simulation of the electronic and mechanical properties and water desalination was performed by ReaxFF software under pressures between 0 and 250 MPa. The novel BiOCl based nanocomposites showed improved electronic and mechanical properties and, most importantly, improvements in salt rejection and water permeability as compared to well-known materials such as graphene and MoS2. BiOCl and BiOCl/Ag2S had a bandgap around two, which is the ideal bandgap for semiconductor photocatalysts. A salt rejection of 98% was achieved under an applied pressure of 10 MPa. Salt rejection was higher for BiOCl/Bi2O3, while water permeability was higher for BiOCl/Ag2S. The monolayer BiOCl was unstable under pressures higher than 50 MPa, but the mechanical stability of BiOCl/Ag2S increased twofold and increased fourfold for BiOCl/Bi2O3, which is even higher than MoS2. However, between the three nanocomposites, BiOCl/Ag2S was found to be the most ideal photocatalytic nanocomposite membrane.

Revealing the effects of terminal groups of MXene on the water desalination performance

The hydrophilicity as well as the charge nature can be tuned by manipulating the surface termination of MXene, which significantly affects the desalination of MXene membrane. However, the effects of termination group of MXene membrane on its water desalination performance are poorly understood. In this work, we adopted classic molecular dynamics (MD) simulation to systematically explore the influences of termination group, including fluorine (F), oxygen (O), and hydroxyl groups (OH), on the desalination performance of Ti 3 C 2 T x membrane. The simulation results showed the surface charge features as well as the hydrogen bond interactions significantly influence the interactions between termination group and water. The water permeability through MXene channel with different surface terminations follows the order, F > O > OH. The charge nature of surface terminations also plays a vital role in their interactions with ions. The negative charge of surface terminations traps Na + ion both near the mouse and inside the channel of MXene membranes. As a result, MXene membranes possess distinctive Na + ion rejection performance. After comparison, we conclude the desalination performance of Ti 3 C 2 F 2 is much better than traditional desalination membranes. Our work revealed the mechanisms responsible for the effects of termination type of MXene on water desalination performance, which might provide useful suggestions for the optimization of MXene membranes for water desalination. • The increase of interlayer distance will promote water permeability but deteriorate ion rejection efficiency. • Water molecules travel fastest in MXene nanochannel with termination of F. • MXene membrane carrying negative charge is benefited for Na + rejection. • The desalination performance of Ti 3 C 2 F 2 is much better than traditional desalination membranes.

Organosilica Multichannel Membranes Prepared by Inner Coating Method Applied for Brackish Water Desalination

A sol-gel method has been widely utilized for membrane fabrication due to low temperatures requirement and high purity. In the application of potable water production, membrane technology also plays an important role applied for brackish water treatment. This study aims to develop a multichannel membrane through an inner coating method and then to demonstrate the membrane performance for brackish water desalination. Two type of organosilica multichannel membranes were fabricated by mixing TEOS as a silica precursor using citric acid catalyst via sol-gel method and pectin as carbon templated. The multichannel membranes were inner-coated up 4 layers and calcined at 175 °C for organosilica multichannel membrane and 300 °C for silica-pectin multichannel membranes in vacuum condition. From FTIR results indicated that organosilica and silica-pectin multichannel membranes show siloxane (Si-O-Si), silanol (Si-OH) and silica-carbon (Si-C) groups. In addition, the organosilica multichannel membrane performed the water flux of 15.74 kg.m-2.h-1and salt rejection of 99.77%, where the silica pectin multichannel membrane performed the lower performance compare to organosilica multichannel membrane (water flux: 11.44 kg.m-2.h-1 and salt rejection: 99.48%). In conclusion, the organosilica multichannel membrane derived from citric acid as catalyst has a better performance compare to organosilica multichannel membrane derived from pectin applied for brackish water treatment. Keywords: organosilica multichannel membrane, inner coating, brackish water treatment

Influence of the formed interface during preparation of poly(vinylidene fluoride) blend cation exchange membrane on the electro-chemical properties and performance

Cation exchange membrane containing low fraction of charge moiety is beneficial as it minimizes the water swelling and back diffusion of ions, increases the mechanical property and lowers the cost. However, moderate to high extent of ion conducting group in a membrane is necessary for the effective ion exchange and good electrodialysis performance. To address this issue, we report a non-solvent (water) induced phase separation process where solid-water interface is generated and helps to migrate the ionic moieties on the surface and transport of ions, while a solid-air interface is formed in the solvent evaporation process which partially hinders the migration of the ionic moieties (high surface energy) on the membrane surface and ion transport property. Cation exchange membranes of the blend of poly(vinylidene fluoride) and poly(methyl methacrylate)-co-poly(styrene sulfonic acid sodium salt) have been prepared by both non-solvent induced phase separation and solvent evaporation process. Membrane containing about 5% (w/w) anionic polymer and prepared by non-solvent induced phase separation process exhibits high transport number (t+ = 0.93), good water desalination performance with power consumption of 1.15 KWhKg−1 and current efficiency of 90% than that of the membrane prepared by solvent evaporation process (power consumption = 1.58 KWhKg−1 and current efficiency = 58%).

The electronic properties and water desalination performance of a photocatalytic TiO2/MoS2 nanocomposites bilayer membrane: a molecular dynamic simulation.

Due to the rapid depletion of water resources, more interest is paid for the efficient desalination process in recent years. MoS2 membrane aroused attention due to its high mechanical stability and electronic properties, which can sustain extra-large strains. In this study, the electronic properties and water desalination performance of TiO2/MoS2-hexagonal, and TiO2/MoS2-rhombohedral nanocomposites bilayer membranes were studied and simulated for the first time. The effect of TiO2 in the performance of MoS2 was observed in water desalination under the defined applied pressure ranging from 50 to 250MPa with a 6.4Å pore diameter. The membrane structure is created and optimized. The energy minimized for TiO2 from - 19,596.4282kcal/mol for the initial structure to - 19,605.1611kcal/mol for the final structure. For TiO2/MoS2-hexagonal, the energy minimized from - 4955.54271eV) to - 4955.62091eV and TiO2/MoS2-rhombohedral from - 6042.26925eV to - 6046.91835eV. A molecular dynamic (MD) simulation was performed using Material Studio 2019 to study the electronic properties under 0-1eV electric field using the CASTEP code. The results showed a better photocatalytic performance under the external electric field. The effect of external electric field significantly intensifies absorption in the visible range and achieved a high photocatalytic activity on TiO2/MoS2. TiO2, TiO2/MoS2-hexagonal and TiO2/MoS2-rhombohedral nanocomposites bilayer membranes are simulated and evaluated for the water desalination using ReaxFF software. Both MoS2 phases with TiO2 have achieved a high salt rejection up to 97% (P-value = 0.0036, R2 = 0.958), while TiO2/MoS2-rhombohedral achieved the highest permeability (6.0*10-8mmgcm-2s-1bar-1) (P-value = 0.000296, R2 = 0.972) under 250MPa applied pressure.

Improving water desalination performance of electrospun carbon nanofibers by supporting with binary metallic carbide nanoparticles

Capacitive deionization (CDI) technology is proposed as an environmentally friendly way to desalinate brackish water samples with outstanding efficiency. Since the nanomaterial composition is the controlling factor in the measured activity of fabricated CDI cells, much efforts are directed to explore highly effective nanocomposites with increased electrosorptive capacity and enhanced regeneration behavior during operation for longer periods. Here, the electrospinning process was devoted to synthesize mixed cobalt and titanium carbides nanoparticles onto carbon nanofibers [Co–TiC@CNFs] using cobalt acetate tetrahydrate (CoAc) and titanium (IV) isopropoxide (TIP) as precursor salts and polyvinylpyrrolidone (PVP) as a carbon source. Electrospun mats were then calcined at 950 °C for 6 h using a tube furnace with passing argon gas. This formed nanoporous material could provide numerous pathways for increased ions adsorption with extraordinary electrical conductivity. This could explain its enhanced electrochemical properties as evidenced by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS) methods. A specific capacitance value of 979.40 F g −1 was estimated for Co–TiC@CNFs as 7.42 times higher than that for bare CNFs. Furthermore, this nanohybrid material had a salt adsorption capacity of 33.10 mg g −1 in 1.0 M NaCl solution at 1.2 V that highly exceeded the obtained ones for TiC [2.20 mg g −1 ] and CNFs [8.20 mg g −1 ]. Accordingly, modifying carbon nanofibers with metallic carbides can create suitable nano-constituents for promising CDI cell output.

Comparison of water desalination performance of porous graphene and MoS2 nanosheets.

Following graphene and its derivatives, molybdenum disulfide (MoS2) has become a research hotspot in two-dimensional materials. Both graphene and MoS2 exhibit great potential in water treatment. A variety of nanoporous graphene or MoS2 membranes have been designed for water desalination. In this work, we compared the water flux and ion rejection of MoS2 and graphene nanopores, using molecular dynamics simulations. The simulation results demonstrate that monolayer nanopores have higher water fluxes than bilayer nanopores with lower ion rejection rates. MoS2 nanopores perform better than graphene in terms of water permeability. Exploration of the underlying mechanism indicates that the water molecules in the MoS2 pores have faster velocity and higher mass density than those in the graphene pores, due to the outer hydrophobic and inner hydrophilic edges of MoS2 pores. In addition, increasing the polarity of the pore edge causes a decrease in water flux while enhancement of ion rejection. Our findings may provide theoretical guidance for the design of MoS2 membranes in water purification.

Freestanding N-doped graphene membrane electrode with interconnected porous architecture for efficient capacitive deionization

Freestanding electrodes without the influences of additives have been considered as a kind of ideal electrode structure in the field of capacitive deionization (CDI). However, subjected to conductivity, available surface areas, hydrophilicity and etc., effectively construction of freestanding CDI electrodes with high water desalination performance still face great challenges. Herein, we will demonstrate a unique N-doped graphene freestanding porous membrane electrode with excellent water desalination performance. The preparation process mainly includes the assembly of core-shell composites with incomplete graphene oxide shells into bulk membranes using compression molding method and the heat-treatment under NH3 atmosphere. These reserved spherical shells with loopholes and N-doping make up the freestanding membrane electrodes with network porous architecture. The interconnected sphere shells efficiently improve the availability of surface and pores in the monolithic assembly, while the doping of nitrogen element further enhances the accessibility of graphene-based surface by the electrolyte. As a result, such graphene carbonaceous freestanding electrodes exhibit excellent water desalination performance with a high CDI capacity of about 21.8 mg/g in NaCl solution. Moreover, such freestanding membrane electrodes also possess good desalination abilities towards some other salts such as KCl, CaCl2 and MgCl2, suggesting their potential applications in complex brine solution.

Ozark Graphene Nanopore for Efficient Water Desalination.

A nanoporous graphene membrane is crucial to energy-efficient reverse osmosis water desalination given its high permeation rate and ion selectivity. However, the ion selectivity of the common circular graphene nanopore is dependent on the pore size and scales inversely with the water permeation rate. Larger, circular graphene nanopores give rise to the high water permeation rate but compromise the ability to reject ions. Therefore, the pursuit of a higher permeation rate while maintaining high ion selectivity can be challenging. In this work, we discover that the geometry of graphene nanopore can play a significant role in its water desalination performance. We demonstrate that the ozark graphene nanopore, which has an irregular slim shape, can reject over 12% more ions compared with a circular nanopore with the same water permeation rate. To reveal the physical reason behind the outstanding performance of the ozark nanopore, we compared it with circular, triangular, and rhombic pores from perspectives including interfacial water density, energy barrier, water/ion distribution in pores, the ion-water RDF in pores, and the hydraulic diameter. The ozark graphene nanopore further explores the potential of graphene for efficient water desalination.

Simulation of the impact of solar radiation intensity on the performance of economical solar water desalination still in Semnan province

Semnan province with a total area of 97000 km2 is the sixth biggest province in Iran. The evaporation rate in this province is high and can be. The index of the urban and rural water networks in this province is much higher than the global average, but according to the goals set for water supply to all people in all cities and villages, using new technologies is an effective way. High potential evaporation intensity in Semnan province, which reaches 1000-3000 (mm) per year, can be converted from a threat to an opportunity by using it as a new source of energy for a sustainable safe drinking water supply. In order to use of evaporation capacity, in this paper the impact of solar radiation intensity on the performance of single-slope solar still is investigated. The solar radiative flux depends on geographical location, season, and time. In this study, the dimension and temperature of the basin are constant and the effect of radiation intensity on water productivity of solar stills is investigated as a function of time, month (April) and location (Semnan province). The accuracy of the numerical method has been evaluated using different models and experimental data for the average Nusselt number on water surface and production rate of water. Results also indicate that the variation trends for radiation intensity are similar to the production rate. The maximum water production rate belongs to 12 o'clock with a 5.6% increase in comparison with 7:00 a.m., which has the lowest evaporation rate in the bell shaped curve.