Papers by Keyword: Desalination

Abstract: Considering the dearth and limited supply of potable water for daily consumption globally, developing a desalination technique to produce water sufficient for the need has become imperative. This study examines the improvement of freshwater productivity in a single-slope solar still by incorporating a solar preheating system. The proposed design utilizes solar still distillation to preheat the feed water before it enters the distillation basin. This approach aims to increase the temperature gradient between the water surface and the glass cover, thereby accelerating the evaporation and condensation process. Experimental evaluations were conducted under varying climatic conditions and flow rates, with and without the preheater. We note that the productivity has improved at each flow rate as follows: at a flow rate of 1 L/min, the improvement percentage reached 96% (CLISS:130 g/hr and CLIPSS:170 g/hr), at a flow rate of 2 L/min, the improvement percentage reached 73% (CLISS:180 g/hr and CLIPSS: 220 g/hr), while the improvement percentage at 3 L/min became 61% (CLISS:240 g/hr and CLIPSS:290 g/hr.), and at a flow rate of 4 L/min, it reached 64% (CLISS:280 g/hr. and CLIPSS: 320 g/hr.), and up to a flow rate of 8 liters/minute, the productivity improvement percentage between the two systems reached 31% (CLISS:310 g/hr. and CLIPSS:340 g/hr.). The results showed that the preheated system significantly improved solar thermal performance and daily production, especially during the early morning and late afternoon hours. Compared to a conventional design, the preheated system achieved an overall productivity increase of 25% to 35%.

Abstract: Water sources in coastal areas are highly susceptible to seawater intrusion, leading to significant environmental and economic losses. Therefore, advanced treatment methods are required to make seawater suitable for clean water production, particularly in addressing water scarcity in coastal regions. One promising approach is seawater desalination using calcium alginate/graphene oxide (GO) beads. In this study, waste coral skeletons were utilized as a calcium source due to their high calcium content. X-ray fluorescence (XRF) analysis revealed that the calcium content in the coral skeletons was 93.4% before calcination and increased to 94.9% after calcination. These findings suggest that coral skeleton waste has potential as an adsorbent for Na⁺ and Cl⁻ ion removal. The synthesis of calcium alginate/GO was conducted using a droplet method and characterized using Fourier-transform infrared spectroscopy (FTIR). The adsorption process for Na⁺ and Cl⁻ ions was investigated at varying CaCl₂ concentrations (0.5 M, 1 M, and 2 M) to determine the optimal conditions for ion removal. Na⁺ ion analysis was performed using atomic absorption spectroscopy (AAS), while Cl⁻ ion concentration was determined via argentometric titration. The optimal Cl⁻ adsorption was observed at a CaCl₂ concentration of 0.5 M with a contact time of 30 minutes, achieving an adsorption efficiency of 99.8% in a standard NaCl solution and 35.9% in seawater. For Na⁺ ion removal, the highest adsorption efficiency was achieved at a CaCl₂ concentration of 2 M with a 30-minute contact time, resulting in 97.3% adsorption in a standard NaCl solution and 61.9% in seawater. These results highlight the potential of calcium alginate/GO composites, derived from waste coral skeletons, as effective adsorbents for seawater desalination.

Abstract: Synthesis of calcium alginate silica gel based on coral skeleton and wedi awu beach sand has the potential to be used as a product to reduce NaCl levels in seawater. This research aims to maximize the potential of natural materials. The materials used in the manufacture of adsorbents are calcium from coral skeletons used as a constituent of CaCl2, silica extracted from Wedi Awu beach sand, and sodium alginate. The three materials were synthesized into a cross-linked calcium alginate silica gel. Silica extracted from beach sand was mixed with sodium alginate, and then the mixture was dripped into CaCl2 solution. The results obtained are white round-shaped adsorbent gel, which occurs because SiO2 reacts with-O-groups on sodium alginate to form a white mixture, and Ca2+ in CaCl2 will crosslink with sodium alginate when dripped, forming an adsorbent gel. In the FTIR analysis of silica calcium alginate adsorbent gel, there are-OH, C=O, C-O groups that can play an active role in NaCl adsorption. Calcium alginate silica adsorbent gel can produce the highest percent adsorption at a CaCl2 concentration of 0.5 M, with an optimum contact time of 60 minutes, namely for Na + obtained a percent adsorption of 95.24% and on Cl-of 99.19%. The results of concentration and time optimization were then tested with real seawater with a percent adsorption of Na + of 69.33% while on Cl-of 37.26%.

Abstract: This study investigates household-scale seawater desalination to address freshwater shortages, particularly in coastal areas or during emergencies. The process involves heating seawater to evaporate it and then condensing the vapor into freshwater. The research compares the efficiency of pure water and salt production from seawater desalination using two heating methods which is gas stoves and induction stoves. Gas stoves which use fossil fuel combustion and induction stoves which use electromagnetic fields to generate heat have different characteristics and efficiencies in the desalination process. After the heating, the seawater then cooling down by using 3 different speed of fan speed.This study evaluates the differences in the amount of pure water and salt produced by these two methods, considering factors such as energy consumption and operational costs. The results of this research are expected to provide useful insights for selecting more efficient and economical heating methods in the seawater desalination process.The results indicate that freshwater production is higher when using an induction stove compared to a gas stove. Freshwater production at low fan speeds yielded 157 g/hour on an induction stove with 600 W power and 147 g/hour on a gas stove with equivalent power of 658.75 W; 168 g/hour on an induction stove with 600 W power and 88 g/hour on a gas stove with equivalent power of 632.92 W; and 153 g/hour on an induction stove with 600 W power and 105 g/hour on a gas stove with equivalent power of 646.58 W. The heating with an induction stove produces more freshwater compared to heating with a gas stove due to its Energy Efficiency, Precise Temperature Control, Heating Speed, Reduced Heat Loss which is better than gas stove.In terms of salt production, both induction and gas stoves produced nearly identical amounts of salt: 34 g/liter on the induction stove and 36 g/liter on the gas stove at low fan speeds; 36 g/liter on the induction stove and 34 g/liter on the gas stove at medium fan speeds; and 34 g/liter on the induction stove and 36 g/liter on the gas stove at high fan speeds. The power required to produce 1 gram of freshwater at low fan speed was 3.57 watts for the induction stove and 7.18 watts for the gas stove; at high fan speed, it needs 3.92 watts for the induction stove and 6.15 watts for the gas stove. Therefore, it can be concluded that the power consumption for the induction stove is significantly lower than that for the gas stove to produce 1 gram of freshwater.

Abstract: Seawater desalination can be applied in Malaysia to overcome water supply issues which majorly due to water pollution. The desalination using membrane technology highly depends on the design of the membrane, operating conditions of the process, and the feed characteristics of the seawater. The aim of this research is to identify the effect of these factors on the performance of the reverse osmosis membrane in desalinating seawater in Malaysia. The simulation study is conducted by using the IMS Design program. The reverse osmosis (RO) membrane process that consists of three membrane stages arranged in series is designed accordingly. The effect of operating temperature, feed concentration, feed pH, and membrane stages on the salt rejection and permeate flux are evaluated. As a result, an increase in temperature and feed concentration reduces the salt rejection percentage, while increasing the permeate flux. However, there is no significant effect of feed pH on the salt rejection percentage and permeate flux since the type of membrane used is able to operate in a wide pH range. Lastly, the four stages membrane increases the permeate recovery and permeate flux but reduces the percentage of salt rejection.

Abstract: In the process of incorporating adsorption with thermal desalination, adsorbents are important because they increase the water vapour uptake rate, and this would yield more desalinated water over a short period. Therefore, they are important and the key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle are thermo-physical properties, surface characteristics and water vapor uptake capacity. The best adsorbent is used as the adsorbent-refrigerant pair and is driven at 50 oC to 85 oC by low-temperature heat sources. When the unsaturated adsorbent is exposed to vapour in the evaporator, the uptake of vapor is accelerated by the high affinity of the water molecules to the silica gel pores. Likewise, when the same adsorbent is heated thermally, the water vapor molecules are removed or desorbed from the adsorbent pores to the cooler surfaces of the condenser tubes, producing high-grade water during the phase. Key words: Desalination; Porosity; Adsorption isotherm; Geometric parameters. Sorption Phenomenon

Abstract: Membrane technology advancement has gained momentous consideration around the globe because of their appealing highlights, such as effectiveness, low expenses, and effective solutions for longstanding issues in alchemical industries. This study expected to incorporate graphene nanoparticles into Polyvinylidene difluoride (PVDF) to form nanofiltration (NF) layers using DMF (Dimethyl formamide) as solvent via DIPS (diffusion induced phase separation) technique. PVDF polymer membrane performances with varied percent (1 – 6% wt.) of graphene concentrations are studied Infrared spectral, water uptake, water contact angle, and ion rejection measurements. Scanning electron microscope (SEM) analysis showed that the pore size is often regulated by incorporating graphene nanoparticles (80-90 nm) as compared to PVDF membranes. The PVDF membranes exhibited a relative increase in the contact angle from PVDF to PVDF-G6% i.e. 50.3° to 63.46 ± .3, thus, showing a relative increase in hydrophobicity. The higher percent of graphene (> 6% by wt.) results in nanoparticle accumulation that showed the performances of PVDF/graphene rejection possessing relatively the same results. The results confirmed that the prepared membranes possess an excellent ability to treat wastewater.

Abstract: Current available methods for water desalination are energy intensive, expensive, and not feasible for small-scale applications. As an alternative, hydrogels may be utilized as a draw agent and semi-permeable membrane forward osmosis by acting as both to desalinate water. This study aims to synthesize and characterize hydrogels made from cellulose derivatives and reduced graphene oxide nanofillers in order to desalinate and remove microbes from seawater without requiring a large energy input. The hydrogels are formed by combining carboxymethyl cellulose, hydroxymethyl cellulose, reduced graphene oxide, and water to form a paste which is soaked in a crosslinking solution made of citric acid. Swelling, compression, antimicrobial efficiency and desalination efficiency tests were done. The hydrogel that obtained the highest values has a swelling ratio of 1,447%, compressive strength of 4 bar, desalination efficiency of 30%, and antimicrobial properties.

Abstract: Water scarcity is growing and in particularly in regions where population is high. It is estimated by world wild life organization that two thirds of human population may face water shortage by 2025. However, the amount of water available on earth covers approximately two thirds of the total surface area, but most of the water is seawater. Seawater cannot be used for any human use due to the high salinity levels. Desalination processes have been implemented on various scales whereby reverse osmosis is the most successful. However, such system is too complex and expensive. An alternative system utilizing humidification-dehumidification process for desalination is proposed in this paper. The process involves the use of a novel hydrophobic membrane allowing the humidification. Two configurations have been tested in a closed loop cycle, namely: static and moving membrane. The results from the experiments have shown that the efficiency of the moving membrane configuration is higher than the static by 46%. And based on 1 Litre brine feed, 50% of the volume has been successfully desalinated.

Abstract: This work is devoted to finding of a solution of the actual problem of modern solar power engineering that consists in incomplete conversion of the Planck spectrum of solar radiation using photoelectric conversion. Concentrated solar power being an alternative faces other limiting features such as high cost of building and maintenance, large areas occupied by these plants, the need of precise adjustment of mirrors-lenses systems and also its detrimental effect on nature, birds in particular. An intensification of vaporization from the surface of water can become a solution. In this work a thin layer made of graphene nanoflakes was used as an absorbing media for solar radiation that intensifies evaporation. Also it acts as a catalyst for transmission of water through porous substrate that was made of wood. Results for these experiments were compared with evaporation from free surface. The possibility of using of these porous substrates for the purpose of desalting and purifying water was also experimentally studied.