Synthesis and some sorptive properties of highly crosslinked cyanomethyl styrene/divinylbenzene copolymers

Synthesis and Porous Structure Characteristics of Allyl Methacrylate/Divinylbenzene Polymers

A set of six porous copolymers of allyl methacrylate (AllMeth) and divinylbenzene (DVB), containing 5 to 50 wt% of the latter crosslinker, are synthesized by suspension polymerization method in the presence of inert diluents. Obtained polymers have various specific surface areas-those with 20 to 50 wt% of DVB have a high surface area in the range of 410-480 m2/g, depending only slightly on the amount of the aromatic crosslinker. Specific surface area decreases strongly only when DVB content is 15 and 5 wt%. That is the feature that is unusual for crosslinked polymers and indicates the participation of allyl groups in making a novel polymeric network of high porosity. All polymers contain polar carbonyl groups, with an electron pair able to interact with polar sorbates. Polymers are characterized using elemental analysis, FTIR, and their porous structure is characterized by nitrogen adsorption at 77 K. All polymers contain residual allyl groups, which possibly can serve as convenient points for chemical modification, allowing for the future synthesis of specialty polymers (such as ion-exchangers and coordinating resins).

Effects of hydrophilic monomers on sorptive properties of divinylbenzene-based reversed phase sorbents

Solid phase extraction (SPE) has been extensively used as a pretreatment method. In SPE methods, commercially available reversed phase type sorbents, which consist of macroporus styrene-divinylbenzene or copolymers including divinylbenzene (DVB) and hydrophilic monomers, have been applied to a variety of samples. The later sorbents are called hydrophilic lipophilic balanced (HLB) type sorbents. Hydrophilic monomers in hydrophilic lipophilic balanced type sorbents contribute to the increase in retention of polar compounds, because hydrophilic monomers improve the wettability and increase the interaction with polar compounds as analytes. In this study, three different methacrylate monomers (ethylene glycol dimethacrylate (EGDMA), glycerol dimethacrylate (GDMA) and trimethylolpropane trimethacrylate (TMPTMA)), which are expected to improve the retention of polar compounds, were chosen, and DVB-based copolymetric sorbents including the three monomers were newly synthesized. Among them, the sorbents including GDMA or TMPTMA gave higher recoveries to polar compounds such as uridine and adenine than that including EGDMA. The optimization studies of hydrophilic lipophilic balance, inert diluent and the purity of DVB improved the sorptive abilities of the sorbents. The developed sorbents have higher recoveries for variety of polar compounds (cytosine, uracil, cytidine, uridine, 2'-deoxycytidine, 2'-deoxyguanosine, adenine, thymidine, adenosine and 2'-deoxyadenosine) than commercially available hydrophilic lipophilic balanced type sorbents, while the recoveries for theophylline were comparable between the proposed sorbents and the commercial sorbents.

Triazines removal by selective polymeric adsorbent

The objective of the study was to investigate sorption of simazine, atrazine, propazine and terbuthylazine on specific polymeric adsorbent and thereby evaluate the possibility of triazine-based herbicide removal from the aqueous solution. In order to obtain polymer adsorbent for triazines removal, the poly(divinylbenzene) was synthesized in radical polymerization using bead polymerization, and modified with maleic anhydride in Diels–Alder reaction with subsequent base hydrolysis. The porous material containing carboxyl groups was obtained. Experiments have been performed in single and multi-component mixtures of herbicide in the ppm concentration range. Introduction of carboxyl groups into polymer structure resulted in obtaining specific interactions, such as hydrogen bonds between modified poly(divinylbenzene) and triazines, therefore intensification of adsorption was observed. Calculated distribution coefficients of triazines (K = 2600–35 100) testify to their effective removal from aqueous solutions on the studied adsorbent. Selective sorption of triazines is observed and explained in relation to the binding mechanism which involve hydrophobic interactions and hydrogen bonding. The effect of the adsorbate structure on the ability to form specific interactions with the tested adsorbent was investigated. The kinetic of sorption and the parameters of Langmuir and Freundlich isotherms for the studied systems were determined.

Influence of the filler on thermal properties of porous VP-TRIM copolymers

In this paper, the synthesis and characterization of thermal properties of porous copolymers 1-vinyl-2-pyrrolidone with trimethylolpropane trimethacrylate are presented. They were obtained by suspension polymerization as a pure polymers or composite materials with different inorganic fillers. The influence of the type of filler on the textural and thermal properties was investigated in details. It was found that the value of the porous surface area of composites is much lower than in the case of pure copolymers. Thermal properties of the obtained materials were investigated by the means of thermogravimetry and differential scanning calorimetry.

PEI@SiO2: synthesis from diatomite and application for capturing phenolic compounds from aqueous solution

A PEI@SiO₂ hybrid composite was synthesized for sorption of phenolic compounds.

Preparation and characterization of polar polymeric adsorbents with high surface area for the removal of phenol from water

Preparation of methyl methacrylate (MMA)/divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA)/DVB copolymers via suspension polymerization yielded precursors which possess residual vinyl groups. Post-crosslinking of appropriate dichloroethane swollen precursors without external crosslinking agent in the presence of anhydrous ferric chloride (FeCl(3)) yielded post-crosslinked resins with high surface area and suitable polarity. FT-IR spectrum indicated that increasing the proportion of MMA or EGDMA in monomer mixtures notably reduces the amount of the pendant vinyl groups onto the matrix of the precursors. Furthermore, the pendant vinyl groups of precursors were almost absent when the content of MMA and EGDMA increased to 40 mol% and 20 mol% in the monomers, respectively. The specific surface areas and pore volumes of copolymers showed a remarkable increase after post-crosslinking. Experimental results showed that isotherms of phenol adsorption onto these polymeric adsorbents could be represented by Freundlich model and Langmuir model reasonably. PDE-5 pc exhibited higher adsorption capacity of phenol than other adsorbents, which resulted from synergistic effect of larger specific surface area and polar groups onto the network. Column adsorption/desorption dynamic curves suggested that PDE-5 pc is a potential candidate for treatment of chemical effluent containing phenol and phenolic pollutants.

Enhanced adsorption of phenol from water by a novel polar post-crosslinked polymeric adsorbent

A novel post-crosslinked polymeric adsorbent PDM-2 was prepared by Friedel-Crafts reaction of pendant vinyl groups without external crosslinking agent. Both the specific surface area and the pore volume of starting copolymer PDM-1 increased significantly after post-crosslinking. Batch adsorption runs of phenol from aqueous solution onto PDM-1 and PDM-2 were investigated. Commercial macroporous resins XAD-4 and AB-8 were chosen as the comparison. Experimental results showed that isotherms of phenol adsorption onto these four polymeric adsorbents could be represented by Freundlich model reasonably. PDM-2 exhibited higher adsorption capacity of phenol than other three adsorbents, which resulted from synergistic effect of larger specific surface area and polar groups on the network. The adsorption process for phenol was proved to be exothermic and spontaneous in nature. Thermodynamic parameters such as Gibb's free energy (DeltaG), change in enthalpy (DeltaH) and change in entropy (DeltaS) were calculated. Kinetics studies indicated that phenol uptake onto PDM-1 and PDM-2 followed the pseudo-second order model and the intraparticle diffusion process was a rate-controlling step. Column adsorption runs demonstrated that nearly 100% regeneration efficiency for PDM-2 by 3BV industrial alcohol and the adsorbate phenol can be easily recovered by further distilling. Continuous column adsorption-regeneration cycles indicated negligible capacity loss of PDM-2 during operation.

Synthesis of novel methacrylate based adsorbents and their sorptive properties towards p-nitrophenol from aqueous solutions

The polymeric adsorbents were synthesized from 2-dimethylaminoethyl methacrylate (DMA) and [2-(methacryloyloxy)ethyl]dimethylhexadecylammonium bromide (DMAC(16)) monomers in the presence of ethylene glycol dimethacrylate (EDMA) cross-linking monomer using suspension polymerization technique and their adsorption efficiencies in the removal of p-nitrophenol from aqueous solutions were investigated. DMAC(16) monomer was prepared by means of modification of DMA monomer with 1-bromohexadecane. Adsorption experiments were carried out in a batch system and the experimental parameters were evaluated with respect to pH, agitation time, temperature and initial p-nitrophenol concentration. It was observed that the adsorbent poly[2-(methacryloyloxy)ethyl]dimethylhexadecylammonium bromide (p-DMAC(16)) prepared from DMAC(16) monomer was more effective in the removal of p-nitrophenol than the adsorbent poly(2-dimethylaminoethyl methacrylate) (p-DMA) prepared from DMA monomer. The effective pH ranges for the adsorption of p-nitrophenol onto p-DMAC(16) and p-DMA were 2-12 and 3-9, respectively. Langmuir and Freundlich adsorption models were used to describe the isotherms and find isotherm constants. The Langmuir model was well agreed with experimental data for both adsorbents. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were used to understand the mechanism of the adsorption process and it fitted very well the pseudo-second-order kinetic model for each adsorbent. Thermodynamic parameters such as activation energy and changes of free energy, enthalpy, and entropy were also evaluated for the adsorption of p-nitrophenol onto each adsorbent. Additionally, reusability of the adsorbents was investigated and the results showed that both adsorbents can be employed many times without a significant loss in their adsorption capacities for the removal of p-nitrophenol from water.

Traditional Chinese medicine and separation science

Traditional Chinese medicines (TCMs) are getting more and more popular nowadays in the whole world for improving health condition of human beings as well as preventing and healing diseases. TCM is a multi-component system with components mostly unknown, and only a few compounds are responsible for the pharmaceutical and/or toxic effects. The large numbers of other components in the TCM make the screening and analysis of the bioactive components extremely difficult. So, separation and analysis of the desired chemical components in TCM are very important subjects for modernization research of TCM. Thus, many novel separation techniques with significant advantages over conventional methods were introduced and applied to separation and analysis of the chemical constituents in TCM. This review presents just a brief outline of the applications of different separation methods for the isolation and analysis of TCM constituents.

New materials in sorptive extraction techniques for polar compounds

This paper provides an overview of the new developments in material and format technology that improve the extraction of polar compounds in several extraction techniques. They mainly include solid-phase extraction, but there are also other sorptive extraction techniques, such as stir bar sorptive extraction and solid-phase microextraction that use either fibers or in-tube devices. We focus on new synthesised materials that are both commercially available and "in-house". Most novel materials that enhance the extraction of polar compounds are hydrophilic and have large specific surface area; however, we also cover other leading technologies, such as sol-gel or monolith. We describe the morphological and chemical properties of these new sorbents so that we can better understand them and relate them to their capability of retaining polar compounds. We discuss the extraction efficiency for polar compounds when these polymers are used as sorptive material and compare them to other materials. We also mention some representative examples of applications.