Method for the desalination of seawater using solar energy

Abstract

A technique to desalinate seawater using melanin-concentrated solar energy wherein the melanin is extracted from a local isolate Aspergillus niger. A device consists of two fixed upper and lower containers with same volume of seawater in both, with or without melanin powder dissolved in the lower container at rate of 0.17 gm of melanin powder per 10 ml of water. The device is put outdoors under direct sunlight during daytime, circular water droplets free of salt starts to appear on the external bottom of upper container. Water droplets are collected by a sterile glass rod, pH of droplets water is about 7.1. Yield of fresh water is approximately 10 ml droplets water from 600 ml seawater per hour; after 24 hours day and night incubation, seawater in the upper container dries out leaving salt crystals. Yield of 1000 m3 seawater is 100 m3 freshwater (1000 L seawater yield 100 L freshwater).

Claims

1. A method for the desalination of seawater comprising the steps of: arranging two glass Petri dishes of equal diameter, as upper and lower dishes; placing seawater into each Petri dish; and extracting melanin from a culture of treated Aspergillus niger, washed and dried to form a melanin powder; adding 0.17 gm of the melanin powder per 10 ml of water to the lower dish and the set is exposed to light indoors.

2. The method for the desalination of seawater of claim 1, wherein the obtained droplets of fresh water is collected from the lower surface of the upper dish.

3. A method for the desalination of seawater comprising the steps of: utilizing plastic containers of the same size arranged as upper and lower compartments; placing a volume of 600 ml seawater into each plastic container; extracting melanin from a culture of treated Aspergillus niger, washed and dried to form a melanin powder; adding 0.17 gm of the melanin powder per 10 ml of water in the lower compartment; and exposing the plastic containers outdoors under direct sunlight.

4. The method of desalination of seawater of claim 3, wherein the obtained droplets fresh water is collected from the lower surface of the upper container.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates bench scale experiment of two glass Petri dishes fixed one over the other with melanin dissolved in the lower dish and the device is exposed to sunlight according to embodiment 3.

(2) FIG. 2 illustrates another bench scale experiment of two glass Petri dishes fixed one over the other and the device is exposed to sunlight according to embodiment 4.

(3) FIG. 3 illustrates bench scale experiment showing two glass Petri dishes fixed one over the other with salt crystals in the upper dish according to embodiment 4.

(4) FIG. 4 illustrates another bench scale experiment of three glass Petri dishes fixed one over the other and the device is exposed to sunlight according to embodiment 5.

(5) FIG. 5 illustrates an outdoor experiment of two rounded plastic containers fixed one over the other with melanin dissolved in the lower container and the device is placed outdoors to be exposed to direct sunlight according to embodiment 6.

(6) FIG. 6 illustrates an outdoor experiment of two rounded plastic containers fixed one over the other and the device is placed outdoors to be exposed to direct sunlight according to embodiment 7.

(7) FIG. 7 illustrates an outdoor experiment of two rounded plastic containers fixed one over the other showing formation of circular water droplets on the lower surface of the upper container according to embodiment 7.

DETAILED DESCRIPTION OF THE SEVERAL EMBODIMENTS

(8) To make the present disclosure clear, the following embodiments give detailed description.

Embodiment 1

(9) Prepare Sabouraud's agar (Oxoid, UK) on disposable plastic Petri dishes, make subcultures from A. niger stock and incubate at 30° C. for 14 days. Prepare wet mount smears by removing portions of the mycelia and stain with lacto-phenol cotton-blue. Examine microscopically to confirm pure growth of the mould.

Embodiment 2

(10) To extract melanin from the obtained culture, cut from agar surface disks of 15 mm diameter and heat in 1 M sodium hydroxide 3 ml volume until boiling. Then heat in autoclave, at temperature of 121° C., for 20 minutes. Treat the solution with hydrochloric acid to precipitate melanin, wash 3 times in DW and dry overnight at 20° C.

Embodiment 3

(11) In a bench scale experiment, put 30 ml seawater as such without any treatment in each of two glass Petri dishes and fix one over the second to make an upper petri dish 10 and a lower petri dish 12. Dissolve 0.17 gm of melanin powder per 10 ml water 14 in the lower plate. Place the device beside a window to be exposed to sunlight. On examination the lower surface of the upper plate after 30 minutes is cloudy and buildup of water droplets starts and is increased as time passes. Collect water droplets with sterile glass rod to measure its volume.

Embodiment 4

(12) In another bench scale experiment, put 30 ml seawater as such without any treatment in each of an upper petri dish 16 and a lower petri dish 18 and fix one over the second to make upper 16 and lower plates 18. Place the device beside a window to be exposed to sunlight. On examination the lower surface of the upper plate after 30 minutes is cloudy and buildup of water droplets starts and is increased as time passes. Collect water droplets with sterile glass rod to measure its volume. The buildup of water droplets starts immediately after collection; after 24 hours water dries out in the upper dish leaving salt crystals only 20.

Embodiment 5

(13) Further, in another bench scale experiment, put 30 ml seawater as such without any treatment in each of three glass Petri dishes and fix one over the other to make an upper petri dish 22, a middle petri dish 24 and a lower petri dish 26. Dissolve 0.17 gm of melanin powder per 10 ml water in the lower plate. Place the device beside a window to be exposed to sunlight. On examination the lower surface of the upper and middle plates after 30 minutes is cloudy and buildup of water droplets starts and is increased as time passes. Collect water droplets from the upper and middle plates with sterile glass rod to measure its volume. The water volume is double the volume obtained in embodiment 3.

Embodiment 6

(14) In an outdoor experiment, use rounded plastic containers of same size where volume of 600 ml seawater is put in each. Arrange as an upper plate 28 and a lower plate 30. Dissolve 0.17 gm of melanin powder 32 per 10 ml of water in the lower plate. Place the device outdoors to be exposed to direct sunlight. Collect water droplets with glass rod. After 24 hours, seawater in upper plate is dried out while in lower container seawater is about 500 ml at the end of experiment. Collected droplet water after 24 hours is 100 liter from 1000 liter seawater i.e. 100 m.sub.3 from 1000 m.sub.3 seawater (1 m.sub.3 seawater gives 16 L per hour).

Embodiment 7

(15) In another outdoor experiment, use rounded plastic containers of same size where volume of 600 ml seawater is put in each. Arrange as an upper plate 34 and a lower plate 36 without melanin. Place the device outdoors to be exposed to direct sunlight. Collect water droplets 38 with glass rod. After 24 hours, seawater in upper plate is dried out while in lower container seawater is about 450 ml at the end of experiment. Difference between collected droplet water after 24 hours in embodiment 5 (using melanin) and embodiment 6 (without melanin) is not significant.

REFERENCES

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