Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto the silanized silica followed by a protonation process. The FTIR spectra and XPS analysis proved thatDMAEMAwas grafted successfully onto the silica surface. The resultant adsorbent manifested a high ion exchange capacity (IEC) of ca. 1.30 mmol/g and the Cr (Ⅳ) adsorption behavior of the adsorbent was further investigated, revealing the recovery of Cr (Ⅳ) increased with the adsorbent feed and the equilibrium adsorption could be achieved within 40 min. The adsorption capacity, strongly depended on the pH of the solution, reached a maximum Cr(Ⅵ) uptake (ca. 68 mg/g) as the pH was in the range of 2.5-5.0. Furthermore, even in strong acidic (4.0 mol/L HNO3) or alkaline media (pH 11.0), the adsorbent had a sound Cr(Ⅵ) uptake capacity (ca. 22 and 30 mg/g, respectively), and the adsorption followed Langmuir mode. The results indicated that this adsorbent, prepared via a convenient approach, is applicable for removing heavy-metal-ion pollutants (e.g. Cr(Ⅵ)) from waste waters.

Most of the hydrogels deswell more remarkably in Fcontaining solutions than in other monovalent anion containing solutions. However, significant deswelling followed by abnormal reswelling of polymer gel in KF solutions with increasing F concentration was observed in a series of polymer gels consisted of phenyl rings, for instance, poly(styrene sulfonic acid) (PSSA), hydroxypropyl methylcellulose phthalate (HPMCP) and poly (4-vinyl phenol) (P4VPh) gel. Driving force of this phenomenon was studied to reveal the specific interactions involved in the aqueous systems of aromatic polymers. Elemental analysis and XPS results suggest that F is embedded to the gel by the physical adsorption of KF, as well as the interactions between phenyl ring and F. Further theoretical calculations revealed that the interaction may be (phenyl)CH F (H2O)n interaction, which is stronger than (phenyl) CH (H2O)n hydrogen bond. This kind of interaction decreases with the increasing water number and it is invalid when the surrounding water number ismore than 5 for the phenol-F (H2O)n system. Therefore, we conclude that F could bind to phenyl ring via such (phenyl) CH F (H2O)n interaction in solutions with low hydrophilicity. The strong polarization effect of F and (phenyl)CH…F(H2O)n interaction are two important driving forces for the reswelling of gels.

Adsorption behavior of Sr(Ⅱ) ions was investigated using gel adsorbents based on three types of polysaccharide derivates: carboxymethylated cellulose (CMC), carboxymethylated chitosan (CMCts) and hydroxypropyl methylcellulose phthalate (HPMCP). Maximum adsorption capacities were reached in about 0.5 h for CMCts, 1 h for CMC, and 2 h for HPMCP. The adsorption capacity increased with increasing pH, and decreasing ionic strength. The maximum adsorption capacity of Sr(Ⅱ) ions into CMC, CMCts and HPMCP gels at 25 ◦C were 108.7, 99.0, and 83.3 mg/g gel, respectively, based on the Langmuir isotherms. XPS analysis indicates that Sr(Ⅱ) ions are adsorbed into the three adsorbents according to the ion-exchange mechanism. Desorption of Sr(Ⅱ) ions could be carried on by immersing the adsorbents in the solutions with low pH or high ionic strength, or heating the adsorbents in the moist hot environment.

Hydroxypropyl methylcellulose phthalate (HPMCP) gel was synthesized from the sodium form of HPMCP by radiation-induced crosslinking, followed by converting the phthalate groups on HPMCP to non-ionic forms via ion exchange. The non-ionic H-type gels showed different phase transition behaviors from Na-type gels. Significant antipolyelectrolyte swelling behavior of this amphiphilic gel was observed in various aqueous salt solutions, comparing with the polyelectrolyte swelling behavior of ionic HPMCP gels. After immersed in aqueous salt solution, the morphology of H-type HPMCP gels changed from heterogeneous structure to homogeneous structure. The swelling behavior of the gels in several circumstances with potential applications, for instance, solutions with different temperature and pH, surfactants, and typical drug models, were investigated. H-type HPMCP gels showed similar temperature and pHstimuli responses to that of Na-type HPMCP gels. Furthermore, H-type HPMCP gels showed different swelling behaviors in cationic surfactant (C12TAB) and anionic surfactant (SDS) solutions. The investigations regarding drug embedment and release of this amphiphilic gel in inorganic salt and BSA solutions revealed that the embedment amount and release ratio were both high due to the improved swelling ability in saline condition of H-type HPMCP gels.