Synthesis Of Montmorillonite-Sodium Polyacrylate Material And Its Water Adsorption Under Fresh/Salty Environment

Sea water intrusion was a global problem; the situation in our country was very serious. It should be of great urgency to prevent sea water intrusion. Building a selective cut-off wall can not only prevent sea water intruding fresh water, but also can intercept fresh water going to sea. The subject researched on material filled in the cut-off wall which was sensitive to salt, having a good capacity of swelling when it met fresh water, shrinked when it met salty solution. By taking the advantage of the property of filled agent, the water percolation rate of selective cut-off wall would change as it varied. Then we can make it applicable in preventing sea water intrusion. Inorganic-organic superabsorbent is the best choice of the salt-sensitive materials. First of all discuss the expansion properties of the inorganical montmorillonite in the brackish water environment, and then discuss the swelling properties of different synthetic conditions in preparing montmorillonite/polyacrylate sodium material in fresh/salty water environment, only to provide the basic data for the study of salt-sensitive materials.This experiment researched on how NaOH and HCl influenced on swelling of montmorillonite suspension,as well as the addition of NaCl and CaCl2; By using the ion Chromatography, stereomicroscope and the technique of laser particle size analysis, the research studied the relationship between particle size changes of montmorillonite and its swelling; A serials of Montmorillonite/Sodium polyacrylate super-absorbent materials were synthesised by solution polymerization reaction,water adsorption tests of these synthetic materials were carried on under fresh/salty environment; The impact of two different kinds of Montmorillonite(MMT) on water adsorption of the synthetic material were analyzed through single factor variables; the impact of five important parameters of polymerization on water adsorption were examined through orthogonal test; according to the optimization results of the orthogonal test,the amount of MMT used in polymerization influencing water adsorption was analyzed through single factor variables; A series of Montmorillonite/sodium polyacrylate super-absorbent materials were synthesized through solution polymerization by changing the amount of montmorillonite(MMT), in the case of monomer acrylic acid、initiator potassium persulfate, corsslinker N,N’-methylene-bisacrylamide, neutralization, temperature unchanged. Using a device to examine the amount of MMT influencing on water swelling of super-absorbent when swelled under a certain pressure, and also the pressure impacting on water swelling of the material; Using a connective device to observe the amount of MMT and water pressure affecting water absorbency of super absorbent; synthetic absorbent materials were characterized by using X-ray diffraction, infrared spectroscopy, and integrated thermal re-analyzer test tools.The result showed that pH which was adjusted by NaOH and HCl had no obvious effect on the suspension swelling; the NaCl and CaCl2solution inhibited the swelling,the more of the concentration the more it inhibited. Meanwhile CaCl2solution was much stronger than NaCl influencing on the swelling volume of Montmorillonite, CaCl2decreased the order of magnitude compared with NaCl which restrained the same volume. According to the ion chromatographic analysis, when mingled CaCl2solution with Montmorillonite, the calcium ion concentrations were more in supernatant suspension than in solution, while sodium were less, the course may be accompanied by ion exchanging process. The particle-size analyzer and the Stereo Microscope showed that the solutions effected on aggregation of the particles of montmorillonite significantly,changing the sizes of the particles,resulting in the decreasing overall volume of the montmorillonite; the natural sodium MMT synthetic material was batter than those synthetic with organic modification MMT when adsorbed under fresh/salty environment; the optimization result of the polymerization test was acrylic monomer36g, MMT20wt%(of acrylic monomer weight), initiator0.1wt%; crosslinker1.2wt%; neutralization70%; temperature70℃, it could adsorb water634.1g/g in fresh,38.6g/g in fresh; The material swelled quickly at the beginning of0-6hs, height X rate of expansion were nearly linear, after6hs expansion rate slowed down changing as curve growth; Under a certain pressure, the swelling ability and gel strength were increasing with increased amount of MMT, which the amount was between Owt%to20wt%,decreasing when content was more than20wt%; when the content was20wt%, the swelling ability was the best; Water-swelling capacity of the material gradually reduced with increasing external pressure, significantly reduced compared with the effect of non-pressure expansion; Under different hydrostatic pressure,the change of material water absorption capacity was not obvious, indicating the hydrostatic pressure had little effect on material swelling; X-ray diffraction,infrared spectroscopy results showed that MMT were chemically combined with sodium polyacrylate,thermal re-analyzer test showed that those synthetic with MMT were better than sodium polyacrylate in thermal stability.The Composite super-absorbent had better swelling capacity than the pure sodium acrylate resin and MMT minerals, which combined the advantages of good swelling capacity of acrylic resin and strength of MMT material.