Method of water purification using hydrophilic and compressible aerogel as draw agent in forward osmosis

Abstract

The present invention discloses a novel hydrophilic and compressible aerogel as draw agent for purification water in forward osmosis (FO), which belongs to environmental pollution control engineering technical field. The improved performances are obtained by optimizing regeneration process of drawing and producing water by using this aerogel as a draw agent in FO technology. Herein, the aerogel complete avoid the draw solution's reverse diffusion and maintain a higher water flux that compensates for its structure characteristics. Moreover, the regeneration of the draw agent and production water should be accomplished through human compression without a complicated physical and chemical method. Simultaneously, this draw agent presents other advantages of wide raw material sources, low cost, wild preparation process, low poison and good film compatibility. It is an innovation as FO technology in portable water purifying device, especially in areas of military and emergency.

Claims

1. A method of water purification using hydrophilic and compressible aerogels as draw agent in forward osmosis, comprising: step 1: obtaining a uniform mixed solution of sodium alginate SA and graphene oxide solid GO under sonication treatment after a period of time, wherein, the weight ratio of SA:GO is 100:18:1, GO concentration is 0.22.5 mg/mL; step 2: obtaining hydrogel by adding CaCl.sub.2 aqueous solution into the mixed solution in step 1 and standing for 2448 h at room temperature; the molar ratio of CaCl.sub.2: sugar units in SA is 3:11:1; putting the hydrogel into deionized water and standing at room temperature; replacing the deionized water every 3 h until the solution conductivity is no more increasing; step 3: pre-freezing the hydrogel in step 2 at 2515 C. for 24 h, and then freeze-drying it at 6090 C. for 2448 h; and step 4: purifying water from wastewater or brackish water in FO process using the obtained aerogel in step 3 as draw agent.

2. The method of water purification using hydrophilic and compressible aerogels as draw agent in forward osmosis according to claim 1, wherein the as-prepared aerogels as a portable forward osmosis device and draw agent replace saccharides in a hydration bag.

Description

DETAILED DESCRIPTION

(1) Specific embodiments of the present invention are described below in detail in combination with the technical solution and accompanying drawings.

Embodiment

(2) 1. Seawater Desalination

(3) The SA-GO aerogels are synthesized as followed: 2 wt % SA (200 mL) and 50 mg GO are mixed through sonication treatment for 2 h. Then 29 mL CaCl.sub.2 (0.24 mol/L) aqueous solution is added into the mixture. Then the uniform solution is poured into a mould and stand for 24 h to form a hydrogel. The as-synthesized hydrogel is impregnated into deionized water at room temperature and the deionized water is replaced every 3 h until the conductivity in solution is no more increasing. The hydrogel is pre-freezed at 25 C. for 2 h then is freezed at 90 C. for 48 h to form an aerogel.

(4) The as-formed aerogel (6 g) is used as draw agent in a hydration bag for seawater desalination. After saturated, the pure water can be obtained through compressing the hydration bag with a slight force.

(5) 2. Rainwater Regeneration

(6) The SA-GO aerogels are synthesized as followed: 2 wt % SA (400 mL) and 100 mg GO are mixed through sonication treatment for 4 h. Then 58 mL CaCl.sub.2, (0.24 mol/L) aqueous solution is added into the mixture. Then the uniform solution is poured into a mould and stand for 48 h to form a hydrogel. The as-synthesized hydrogel is impregnated into deionized water at room temperature and the deionized water is replaced every 3 h until the conductivity in solution is no more increasing. The hydrogel is pre-freezed at 25 C. for 4 h, then is freezed at 90 C. for 48 h to form an aerogel.

(7) The as-formed aerogel (12 g) is used as draw agent in hydration bag for rainwater regeneration. After saturated, the pure water can be obtained through compressing the hydration bag with a slight force. Repeat the above steps, the hydration bag should be multiple used.

(8) 3. Sewage Purification

(9) The SA-GO aerogels are synthesized as followed: 2 wt % SA (2000 mL) and 500 mg GO are mixed through sonication treatment for 4 h. Then 290 mL CaCl.sub.2 (0.24 mol/L) aqueous solution is added into the mixture. Then the uniform solution is poured into a mould and stand for 48 h to form a hydrogel. The as-synthesized hydrogel is impregnated into deionized water at room temperature and the deionized water is replaced every 3 h until the conductivity in solution is no more increasing. The hydrogel is pre-freezed at 25 C. for 4 h, then is freezed at 90 C. for 48 h to form an aerogel.

(10) The as-formed aerogel is used as draw agent in FO reactor for sewage purification. In a two-chamber FO reactor, one is feed solution chamber (sewage), and the other is draw solution chamber (aerogel draw agent). A piston plate is installed close to aerogel. The sewage accesses into the feed solution chamber. After adsorption saturated, the pure water is produced through repeated compressing the aerogel by the piston plate. An effective and stable drawing-releasing water process can maintain at high production water rate even repeated 1000 times.