Synthesis of hyper-cross-linked resins with almost all micro/mesopores as well as controllable functional groups is still challenging. Herein we developed a kind of phenol-modified hyper-cross-linked resins with almost all micro/mesopores, and controlled the uploading amount of phenol on the surface. The results indicated that, due to producing rigid methylene cross-linking bridges, these resins were typical micro/mesoporous materials, and the micropore surface area and micropore volume were up to 70% of the total Brunauer-Emmett-Teller (BET) surface area and pore volume. Moreover, the functionalized polarity of these resins could be accurately controlled by adding different amount of phenol in the reaction. These as-prepared resins were employed as the adsorbents for adsorption using aniline as the adsorbate, and the adsorption experiments showed that these resins were efficient for adsorption of aniline, and the resin adding 5% (w/w) phenol in the reaction possessed the largest equilibrium capacity (qmax = 169.2 mg/g). The adsorption was very fast, 40 min was enough for the equilibrium, and the micropore diffusion model described the kinetic data very well.Phenol-modified hyper-cross-linked resins with almost all micro/mesopores possessed an enhanced adsorption to aniline.

Herein we synthesized three polar post-cross-linked resins by adjusting the initial cross-linking degree of the precursor copolymers, and found that the porosity and polarity of these resins could be effectively tuned. The polar post-cross-linked resin with the initial cross-linking degree of 10% (abbreviated as PVE_10%_pc) possessed a much greater BET surface area and almost all micro/mesopores, but lower content of ester groups, while that with the initial cross-linking degree of 60% (named as PVE_60%_pc) had a much less BET surface area, less micro/mesopores and considerable macropores, but higher content of ester groups. The different porosity and polarity of these resins endowed them with different selectivity for the adsorption of aromatic compounds. PVE_10%_pc owned the largest equilibrium capacity to phenol whilst PVE_40%_pc was the most efficient for adsorption of benzoic acid, and hydrogen bonding, hydrophobic interaction and π-π stacking were the main driving forces for the adsorption.The porosity and polarity of the polar post-cross-linked resins in this paper could be effectively tuned, which endowed them with different selectivity.

•Three N-vinylimidazole modified hyper-cross-linked resins were prepared.•The pore structure of the resins can be carefully tuned by the initial cross-linking degree.•The polarity of the resins can be tuned by the initial cross-linking degree.•The adsorption performance of the resins was selective.•The adsorption of Rhodamine B on the resins was effective.Three N-vinylimidazole modified hyper-cross-linked resins (HP2, HP5, and HP8) were prepared and they were employed to adsorb Rhodamine B from aqueous solution. As the initial cross-linking degree increased, the Brunauer–Emmett–Teller surface area of the resins was approximately identical, while the pore volume sharply increased. Particularly, the micropore and micropore volume greatly decreased with increasing the initial cross-linking degree, while the mesopore area, mesopore volume, and average pore size increased. On the other hand, as the initial cross-linking degree increased, the feeding amount of N-vinylimidazole decreased, and the nitrogen content, the total exchange capacity, and the static contact angle lowered. The adsorption experiments indicated that HP8 was the most efficient for adsorption of Rhodamine B among the three resins, and the equilibrium capacity was up to 420.7 mg/g. The adsorption reached equilibrium within 60 min, and the intra-particle diffusion model characterized the kinetic data very well.Download high-res image (140KB)Download full-size image

Three amino-modified hyper-cross-linked resins (HCP-M, HCP-E, and HCP-D) were synthesized, and they were evaluated for adsorption of p-chlorophenol from aqueous solution. The results indicated that the uploading amounts of the amino groups on the three resins followed an order of HCP-M < HCP-E < HCP-D, while their Brunauer-Emmett-Teller surface area had an opposite order. The three resins were efficient for adsorption of p-chlorophenol from aqueous solution and hydrogen bonding was the main driving force for the adsorption. The isosteric adsorption enthalpy at zero fractional loading had an order of HCP-M (−44.92 kJ/mol) < HCP-E (−57.12 kJ/mol) < HCP-D (−61.53 kJ/mol). At the initial concentration of 502.1 mg/L and the flow rate of 68 mL/h, the saturated dynamic capacities of HCP-M, HCP-E, and HCP-D were 388.1, 394.3, and 318.1 mg/g dry resin, respectively, and these resins could be completely regenerated and repeatedly used.Download high-res image (156KB)Download full-size image

The polar modified hyper-cross-linked resins were synthesized by the suspension polymerization and Friedel-Crafts alkylation reaction, and the effect of the feeding amount of the monomers (N-vinylimidazole and p-vinylbenzyl chloride) on the porosity and polarity were clarified. As the feeding amount of p-vinylbenzyl chloride decreased from 75% to 50% (w/w), the Brunauer-Emmett-Teller surface area of the resins lowered from 1306 to 436 m2/g, and the pore size distribution showed a large population of pores in micropores stretching to a higher percentage of mesopores. As the feeding amount of N-vinylimidazole increased from 5% to 30% (w/w), the nitrogen content of the resins rose from 0.005% to 3.06% (w/w), and the contact angle decreased from 97 ± 4.2° to 28 ± 2.0°. As a result, the porosity and polarity of the resins could be accurately tuned by adjusting the feeding amount of the monomers, and the different porosity and polarity of these resins endowed them with selective adsorption to benzoic acid and Rhodamine B.Download high-res image (61KB)Download full-size image

A series of N-vinylimidazole-modified hyper-cross-linked resins was prepared, and the porosity and polarity of these resins were effectively tuned by altering the feeding amount of N-vinylimidazole in the polymerization. The results indicated that the Brunauer-Emmett-Teller surface area sharply decreased from 1258 to 74 m2/g, the micropore area lowered from 494 to 0 m2/g, the total pore volume greatly decreased from 1.14 to 0.49 cm3/g, and the micropore volume rapidly reduced from 0.39 to 0 cm3/g with increasing the feeding amount of N-vinylimidazole from 10% to 50% (mol/mol), and the pore size distribution showed a large population of pores in the microporous region extending to a higher part of mesoporous region. Meanwhile, the polarity of the resins obviously improved with increasing the feeding amount of N-vinylimidazole. The nitrogen content increased from 0.579% to 7.68% (w/w), and the contact angle decreased from 89.0° to 31.0°. The adsorption experiments indicated that these resins had large equilibrium capacities to p-nitrophenol and o-nitrophenol from aqueous solution, and they could be completely regenerated by a mixed solvent containing 80% (v/v) of ethanol and 0.01 mol/L of NaOH aqueous solution.The N-vinylimidazole-modified hyper-cross-linked resins with tunable porosity and polarity and efficient adsorption of p-nitrophenol, and their mutual interaction were revealed.Download high-res image (200KB)Download full-size image

We employed two polar monomers, triallyl isocyanurate (TAIC) and butyl acrylate (BA), to copolymerize with divinylbenzene (DVB), and synthesized two starting copolymers labeled PDT and PDB. Then, the Friedel–Crafts alkylation reaction was performed for the two starting copolymers, and the residual pendent vinyl groups were consumed, and hence we obtained two novel polar-modified post-cross-linked resins PDTpc and PDBpc. The surface polarity greatly improved due to introduction of the polar monomers, and the Brunauer–Emmett–Teller (BET) surface area and pore volume significantly increased after the Friedel–Crafts alkylation reaction. Compared with the starting copolymers, the non-polar post-cross-linked resin PDVBpc and some other adsorbents in the references, PDTpc and PDBpc possessed a much enhanced adsorption to Rhodamine B, and the equilibrium capacity reached 578.2 mg/g and 328.7 mg/g, respectively, at an equilibrium concentration of 100 mg/L, and the Freundlich model characterized the equilibrium data very well. The adsorption was a fast process and the kinetic data obeyed the micropore diffusion model. These results confirmed that PDTpc and PDBpc had the potential superiority in adsorptive removal of Rhodamine B from aqueous solution.The two novel polar-modified post-cross-linked resins PDTpc and PDBpc possessed a high equilibrium capacity towards Rhodamine B from aqueous solution.

In this study, we developed an effective approach for increasing the equilibrium adsorption capacity of the interpenetrating polymer networks (IPNs) toward polar aromatic compounds. For this purpose, a novel post-cross-linked polystyrene/poly (methyl acryloyl diethylenetriamine) (CMPS_pc/PMADETA) IPNs was synthesized and its adsorption was evaluated from aqueous solution using p-hydroxybenzoic acid as the adsorbate. CMPS_pc/PMADETA IPNs possessed a relatively high Brunauer–Emmett–Teller (BET) surface area and hydrophobic networks as well as hydrophilic networks, inducing a much enhanced adsorption toward p-hydroxybenzoic acid. The equilibrium adsorption capacity of p-hydroxybenzoic acid on CMPS_pc/PMADETA IPNs was remarkably larger than that on its precursors and the equilibrium data were correlated better by Sips model than the Langmuir and Freundlich models. Furthermore, the adsorption was a fast process, and the micropore diffusion model characterized the kinetic data very well. At a feed concentration of 1060.8 mg/L and a flow rate of 10.8 BV/h, the dynamic adsorption capacity was calculated to be 200.8 mg/mL wet resin.The CMPS_pc/PMADETA IPNs had a relatively enhanced adsorption to p-hydroxybenzoic acid.

Novel hyper-cross-linked polystyrene/polyacryldiethylenetriamine (HCP/PADETA) interpenetrating polymer networks (IPNs) were prepared, characterized and evaluated for their adsorption and separation properties using hyper-cross-linked polystyrene (HCP) as the reference. In spite of its much lower Brunauer–Emmett–Teller surface area and less pore volume, HCP/PADETA IPNs possessed a preferable pore structure and appropriate polarity, resulting in a larger equilibrium capacity, faster adsorption rate, higher dynamic breakthrough and saturated capacity towards salicylic acid than HCP. In particular, HCP/PADETA IPNs had a higher enrichment factor for salicylic acid over phenol, leading to the high-efficiency separation of salicylic acid from phenol in their mixed solution.

•We reported an effective method for improving the adsorption of salicylic acid.•We synthesized hydrophobic-hydrophilic PST/PADETA IPNs with medium high BET surface area.•PST/PADETA IPNs had a very large equilibrium capacity to salicylic acid.•PST/PADETA IPNs had a large dynamic capacity to salicylic acid.•PST/PADETA IPNs could be completely regenerated and repeatedly used.Herein we synthesized a kind of novel hydrophobic-hydrophilic interpenetrating polymer networks (IPNs) composed of hydrophobic polystyrene (PST) and hydrophilic polyacryldiethylenetriamine (PADETA) networks, and the as-prepared PST/PADETA IPNs possessed both hydrophobic-hydrophilic property and medium high Brunauer-Emmett-Teller (BET) surface area, and hence bringing to much greater adsorption to the hydrophobic-hydrophilic adsorbate like salicylic acid. Particularly, PST/PADETA IPNs were much superior to some other adsorbents reported in the literatures.The synthesized PST/PADETA IPNs in this study are both hydrophobic and hydrophilic with a medium high BET surface area, and they possess an efficient adsorption to salicylic acid.

The synthesis of hyper-cross-linked resins with tunable porosity and polarity remains a challenge. Herein, we employed an interpenetration reaction, Friedel–Crafts reaction, and amination reaction, and we synthesized a series of polar hyper-cross-linked resins. We found that the porosity and polarity of these resins could be effectively tuned by the interpenetrating polymer networks (IPNs) technology and the Friedel–Crafts reaction. These resins possessed moderate Brunauer–Emmett–Teller (BET) surface area and pore volume, decent polarity, and excellent pore structure, endowing them with efficient adsorption toward phenol. Particularly, the adsorption was very fast: 38 min was sufficient to reach equilibrium, suggesting that these polar hyper-cross-linked resins were potential candidates for the adsorptive removal of phenol.

Hydrophilic–hydrophobic macroporous crosslinked poly(methyl acryloyl diethylenetriamine)/poly(divinylbenzene) (PMADETA/PDVB) interpenetrating polymer networks (IPNs) were prepared, characterized and evaluated for adsorption of salicylic acid from aqueous solution. PMADETA/PDVB IPNs were prepared by filling PDVB networks in the pores of PGMA networks according to IPNs technology and an amination reaction of PGMA/PDVB IPNs with diethylenetriamine (DETA). The structure of PMADETA/PDVB IPNs was characterized by Fourier transform infrared spectroscopy (FT-IR), N2 adsorption–desorption isotherms and chemical analysis. PMADETA/PDVB IPNs had a very large equilibrium adsorption capacity to salicylic acid and the equilibrium adsorption capacity was measured to be 196.4 mg g−1 at an equilibrium concentration of 100 mg L−1. The Freundlich model was more appropriate for fitting the equilibrium data than the Langmuir model and the adsorption was shown to be an exothermic and spontaneous process. The adsorption reached equilibrium within 200 min and the pseudo-second-order rate equation characterized the kinetic data better than the pseudo-first-order rate equation. At an initial concentration of 1035 mg L−1 and a flow rate of 84 mL h−1, the breakthrough and saturated capacities were 75.02 and 159.53 mg mL−1 wet resin, respectively, and the resin column could be completely regenerated and repeatedly by 0.01 mol L−1 of NaOH (w/v) and 20% of ethanol (v/v).

Friedel–Crafts reaction, amination reaction and acetylation reaction were performed with chloromethylated polystyrene (CMPS), and amide-modified hyper-cross-linked resin, HCP-EDA-AA, was prepared. The prepared HCP-EDA-AA owned predominant nanopores and medium polarity, making it possess superior adsorption performance to salicylic acid as compared with the raw material CMPS and the intermediate products, hyper-cross-linked polymer (HCP) and the ethylenediamine-modified hyper-cross-linked resin (HCP-EDA). The Langmuir model characterized the equilibrium data better than the Freundlich model. At a feed concentration of 800.5 mg L−1 and a flow rate of 67 mL h−1, the dynamic capacity of salicylic acid on HCP-EDA-AA was 267.8 mg g−1, very close to the extrapolated value by the Langmuir model (273.9 mg g−1). The salicylic acid adsorbed HCP-EDA-AA resin column was almost regenerated by a mixed desorption solvent including 0.01 mol L−1 of sodium hydroxide (w/v) and 20% of ethanol (v/v). HCP-EDA-AA was repeatedly used nine times and the equilibrium capacity for the ninth time reached 95.5% of the equilibrium capacity for the first time.

In this study, a series of bisphenol-A modified hyper-cross-linked polystyrene resins labeled as HJ-L00, HJ-L02, HJ-L04, HJ-L06 and HJ-L08 were synthesized, characterized and evaluated for adsorptive removal of salicylic acid from aqueous solutions. The structural characterization results indicated that the resins possessed predominant micropores/mesopores, moderate specific surface area and a few bisphenol-A groups on the surface. All the bisphenol-A modified hyper-cross-linked resins were effective for removing salicylic acid from aqueous solutions, and sample HJ-L02 had the largest adsorption capacity. The adsorption equilibrium data were correlated by the Freundlich isotherm model, and a positive adsorption enthalpy was obtained. The kinetic data were analyzed with two diffusion models and indicated that the intra-particle diffusion was the sole rate-controlling step in the first stage. The dynamic experimental results showed that the breakthrough point of the HJ-L02 adsorbent was at 90.2 BV (bed volume, 1 BV = 10 mL) for a feed concentration of 500.0 mg/L of salicylic acid, and 14.0 BV of 1% of sodium hydroxide could completely regenerate the HJ-L02 adsorbent column.Graphical abstractHighlights► Bisphenol-A modified hyper-cross-linked resin adsorbents. ► Shift of pore structures from mesopores to micropores. ► Improved efficiency for removing salicylic acid by adsorption. ► Report of micropore diffusion time constants. ► Adsorption and desorption column dynamics.