Development of Reusable Adsorbent for Environmental Hazardous Materials by Novel Synthesis Method

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The thermosensitive gel turns into hydrophobic above transition temperature and adsorbs the endocrine disrupters, most of which are hydrophobic, by hydrophobic interactions. The adsorbent for phosphoric acid was synthesized from thermosensitive polymer (N-isopropylacrylamide) and the polymer tertiary with amino group. The effects of the gel structure and the copolymerization of hydrophobic or hydrophilic polymer with the gel on the adsorption and desorption properties of thermosensitive gel are investigated. It was found that the endocrine disrupters (Bisphenol-A) were successfully adsorbed onto the porous thermosensitive gel.Adsorption rate of Bisphenol-A on the gel is improved by the porous structure of the gel and the copolymerization of hydrophobic polymer with the gel increase the adsorption amount of Bisphenol-A, whereas the copolymerization of hydrophilic polymer decrease the adsorption amount of Bisphenol-A at the same temperature. Nobel pH-thermosensitive gel adsorbent for phosphoric acid has been developed and its adsorption/desorption property was also investigated in this research. The adsorption/desorption mechanism is considered as follows: Univalent phosphoric acid is adsorbed to ionized tertiary amino groups of the adsorbent at low pH. When the pH is raised, the valence of the phosphoric acid then changes to divalent from univalent. The divalent phosphoric acid is desorbed because the degree of ionization of the tertiary amino groups of the gel is decreased at high pH. In addition, when this gel is heated above the lower critical solution temperature (LCST), phosphoric acid is desorbed by shrinkage of the gel. It was found that the amount of adsorption of phosphoric acid increased with decreasing initial pH value because the tertiary amino groups were not completely ionized at high pH. Therefore, more phosphoric acid was adsorbed at a low pH than at a high pH. The amount of desorption increased with an increase in the initial pH.