Hypercrosslinked Polymeric Resin Research Articles

Insights into the role of VOCs properties on thermal desorption behaviors of two porous polymeric resins

Desorption is a critical process in the recovery or post-treatment of adsorbents saturated with volatile organic compounds (VOCs). In this study, the thermal desorption behaviors for eight VOCs on hypercrosslinked polymeric resin (HPR) and macroporous polymeric resin (MPR) were investigated through isothermal desorption and temperature programmed desorption (TPD). Compared with MPR, HPR with more micropores exhibited a lower desorption rate constant, lower desorption efficiency and higher desorption activation energy due to the strong binding energy generated between VOCs molecules and narrow micropores. As the polarizability of VOCs increased, the desorption rate constants on two porous polymeric resins decreased, while the desorption activation energy showed an incremental trend. Excellent linear correlations were observed between VOC polarizability and desorption rate constants (R2 = 0.957 for HPR and R2 = 0.940 for MPR) as well as between VOC polarizability and desorption activation energy (R2 = 0.981 for HPR and R2 = 0.969 for MPR). Furthermore, a polyparameter linear free energy relationship (PP-LFER) was developed to explore the influences of intermolecular interactions on desorption behaviors of VOCs on porous polymeric resins. The results indicated that the dispersive interaction, which is directly related to polarizability of VOCs, was the primary factor influencing the desorption activation energy of VOCs on porous polymeric resins. The find from this study helps evaluate fleetly and availably the desorption properties of VOCs based on their polarizability.

Gaseous toluene heterogeneous oxidative degradation by iron-based hypercrosslinked polymeric resin LXQ-10

Heterogeneous Fenton-like reaction for gaseous toluene removal was enhanced by loading an amount of iron elements onto the hypercrosslinked polymeric resin (LXQ-10) as a novel catalyst. Characterization and experiment results confirmed that Fe/LXQ-10 with great catalytic and stability performance were successfully synthesized. The effects of several key running parameters such as iron loading amount, initial toluene concentration, H2O2 concentration, and reaction temperature were investigated. Under the optimal conditions for a Fenton-like reaction (gaseous toluene concentration, 200 mg/m3; H2O2 concentration, 0.15 mol/L; reaction temperature, 303 K), 3-Fe/LXQ-10 was identified to produce OH radical and the toluene removal efficiency reached 93.56%. Gas chromatography-mass spectrometry (GC–MS) was employed to detect the byproducts in the toluene removal process, and the possible degradation pathway of toluene was explored. Radical quenching tests and EPR investigation were carried out to clarify the contribution of OH radical in the Fenton-like process. Physical adsorption and OH oxidation were the possible mechanisms of toluene removal. In addition, the catalyst maintained its activity after the six cycles. suggesting strong stability and reusability. All the results demonstrated that Fe/LXQ-10 showed high potential and economic feasibility to remove gaseous toluene through adsorption and Fenton-like oxidation. This research not only presents a promising alternative for the effective removal of gaseous VOCs but also provides a theoretical basis in the field of VOCs control.

Adsorption characteristics of dichloromethane-ethyl acetate/toluene vapor on a hypercrosslinked polystyrene adsorbent.

Dichloromethane (DCM), a typical representative of chlorinated volatile organic compounds (CVOCs), is usually exhausted along with other volatile organic compounds (VOCs), such as toluene and ethyl acetate, in industrial factories. To address the complexity of the components, the large variation in concentration of each component and the water content of the exhaust gases emitted from the pharmaceutical and chemical industries, the adsorption characteristics of DCM, toluene (MB), and ethyl acetate (EAC) vapors on hypercrosslinked polymeric resins (NDA-88) were studied by dynamic adsorption experiments. Furthermore, the adsorption characteristics of NDA-88 for binary vapor systems of DCM-MB and DCM-EAC at different concentration ratios and the nature of the interaction force with the three VOCs were explored. NDA-88 was found to be suitable for treating binary vapor systems of DCM mixed with low concentrations of MB/EAC, and a small quantity of adsorbed MB or EAC would promote the adsorption of DCM by NDA-88, which is attributed to the microporous filling phenomenon. Finally, the influence of humidity on the adsorption performance of binary vapor systems for NDA-88 and the regeneration adsorption performance of NDA-88 were investigated. The presence of water steam shortened the penetration times of DCM, EAC, and MB, regardless of whether it was in the DCM-EAC or DCM-MB two-component systems. This study has identified a commercially available hypercrosslinked polymeric resin NDA-88, which has excellent adsorption performance and regeneration capacity for both single-component DCM gas and a binary mixture of DCM-low-concentration MB/EAC, providing experimental guidance for the treatment of emissions from pharmaceutical and chemical industries by adsorption.

Processable amidoxime functionalized porous hyper-crosslinked polymer with highly efficient regeneration for uranium extraction

Uranium is not only toxic and radioactive, even more an important resource to ensure the nuclear energy development. This work reported an amidoxime-based hyper-crosslinked polymeric resin adsorbent (HWB-AO) to extract uranium from ocean. The monolithic matrix was prepared by suspension polymerization using styrene (St) and divinylbenzene (DVB), followed by post-polymerization modification to graft diaminomaleonitrile (DAMN) and conduct amidoximation to introduce amidoxime groups (AO) in its interior and surface. AO can enhance the affinity to uranium and hydrophilicity to accelerate the uranium adsorption. The monolithic structure overcome the problem that powder adsorbent is easy to drain in real seawater, so the monolithic is easier to apply. The batch adsorption experiments results showed that HWB-AO has an magnificent uranium removal rate (85%) and the maximum adsorption capacity (qe,max) is 256.4 mg g−1. In addition, HWB-AO still maintains a giant adsorption efficiency after eight times adsorption–desorption cycles and is environmentally friendly. Concurrently, HWB-AO exhibits excellent selectivity and removal rate (greater than88%) in modified seawater. Therefore, HWB-AO is considered as a potential adsorbent to perform uranium extraction from natural seawater.

Mechanistic insights into and modeling the effects of relative humidity on low-concentration VOCs adsorption on hyper-cross-linked polymeric resin by inverse gas chromatography

Water vapor is very common in contaminated streams, which has a great influence on the adsorption of low-concentration volatile organic compounds (VOCs) due to the competition between water and VOCs. Understanding adsorption mechanisms and predicting adsorption of VOCs under different relative humidity (RH) are of great importance to design effective adsorption unit. In this study, we comprehensively investigated the effects of RH on the surface properties of hyper-cross-linked polymeric resin (HPR) and adsorption of 18 VOCs at low concentration on HPR under five levels of RH using inverse gas chromatography (IGC). Further, a promising RH-dependent poly-parameter linear free energy relationships (PP-LFERs) model was developed. It was found that water vapor caused the decrease of surface free energy (γst) of HPR due to the occupation of active sites by water molecules, resulting in the decrease of adsorption partition coefficients (K). Moreover, the γst could accurately quantify the effects of RH on the surface properties of HPR. Therefore, the RH-dependent PP-LFERs model was established by correlating RH and γst. The developed model overcame the limited predictive ability of existing models only under a specific RH level, and excellently predicted the lnK values of VOCs (R2 = 0.944, RMSEt = 0.36 and RMSEv = 0.47) under various RH.

Adsorption materials for volatile organic compounds (VOCs) and the key factors for VOCs adsorption process: A review

Volatile organic compounds are harmful to the environment and human health. Adsorption technology has been used to VOCs abatement for over 30 years and has proven to be an effective technology. This work provides a critical review of the recent research developments of VOCs adsorption materials and the key factors controlling the VOCs adsorption process. The average specific surface area, pore volume and VOCs adsorption capacity of different adsorption materials are metal organic frameworks (MOFs) > activated carbons (ACs) > hypercrosslinked polymeric resin (HPR) > zeolites. The mechanism of VOCs adsorption in adsorbent mainly includes electrostatic attraction, interaction between polar VOCs and hydrophilic sites, interaction between non-polar VOCs and hydrophobic sites, and partition in non-carbonized portion. With the specific surface area, pore volume, and surface chemical functional groups increase and the pore size decreases, the adsorption capacity increases. The volume of narrow micropores (size < 0.7 nm) controls the adsorption of VOCs. In addition, methods of activation and surface modification for improving the adsorption capacity of VOCs are discussed. The development of targeted modified adsorption materials and new adsorption materials and reduction of production costs of adsorption materials are especially important in future research.

Adsorption/desorption of toluene on a hypercrosslinked polymeric resin in a highly humid gas stream

Abstract In many sources of volatile organic compounds (VOCs), large amounts of water vapor come from the air and the reactors. The relative humidity (RH) of exhaust gas is normally > 60% and is supersaturated. Maintaining the property of adsorbent on VOCs in a highly humid gas stream is a serious industrial problem. In this study, the adsorption/desorption behavior of toluene in a micro-mesoporous polymeric resin was investigated in a highly humid environment to explore the influence of abound water vapor on resin adsorption and regeneration. This resin could selectively adsorb toluene at an RH of 80%, and its adsorption property was unaffected by the presence of water vapor. In the case of humidity saturation, the resin displayed a high adsorption capacity at a moisture content of

Binary adsorption equilibrium and breakthrough of toluene and cyclohexane on macroporous and hypercrosslinked polymeric resins

Adsorption-based separation is one of the most widely used methods in treating gasoline vapor. For effective control of gasoline vapor emission, the total concentration of non-methane hydrocarbons (NMHC) and the specific component such as toluene must meet the emission limit values. In this study, hypercrosslinked polymeric resin (Hyper-resin) and macroporous polymeric resin (Macro-resin) were selected as adsorbents. Toluene and cyclohexane were chosen as the representative of alkanes and aromatic hydrocarbons components of gasoline vapor. Pure and binary component adsorption isotherms of toluene and cyclohexane on two resins were measured by head space analysis method. Breakthrough data for binary system were obtained at the different concentrations of toluene (12–46 mg/L) and cyclohexane (15 mg/L and 102 mg/L) using a fixed-bed reactor. The results indicate that adsorption equilibria of binary component can be predicted by ideal adsorbed solution theory (IAST) with the average relative error lower than 15% using the pure component adsorption isotherm data. Hyper-resin provides higher selectivity to toluene than Macro-resin in binary equilibrium and breakthrough system. Moreover, the breakthrough adsorption capacities of pure component (toluene and cyclohexane) and their mixture on Hyper-resin are higher than those on Macro-resin, suggesting Hyper-resin would be a promising adsorbent for treating gasoline vapor.

Prediction of Adsorption Equilibrium of VOCs onto Hyper-Cross-Linked Polymeric Resin at Environmentally Relevant Temperatures and Concentrations Using Inverse Gas Chromatography.

Hyper-cross-linked polymeric resin (HPR) represents a class of predominantly microporous adsorbents and has good adsorption performance toward VOCs. However, adsorption equilibrium of VOCs onto HPR are limited. In this research, a novel method for predicting adsorption capacities of VOCs on HPR at environmentally relevant temperatures and concentrations using inverse gas chromatography data was proposed. Adsorption equilibrium of six VOCs (n-pentane, n-hexane, dichloromethane, acetone, benzene, 1, 2-dichloroethane) onto HPR in the temperature range of 403-443 K were measured by inverse gas chromatography (IGC). Adsorption capacities at environmentally relevant temperatures (293-328 K) and concentrations (P/Ps = 0.1-0.7) were predicted using Dubinin-Radushkevich (DR) equation based on Polany's theory. Taking consideration of the swelling properties of HPR, the volume swelling ratio (r) was introduced and r·Vmicro was used instead of Vmicro determined by N2 adsorption data at 77 K as the parameter q0 (limiting micropore volume) of the DR equation. The results showed that the adsorption capacities of VOCs at environmentally relevant temperatures and concentrations can be predicted effectively using IGC data, the root-mean-square errors between the predicted and experimental data was below 9.63%. The results are meaningful because they allow accurate prediction of adsorption capacities of adsorbents more quickly and conveniently using IGC data.

Acetylaniline modified hypercrosslinked polystyrene resins and their equilibria and kinetics towards glabridin from Glycyrrhiza glabra L. extracts

As reported in our previous work, crosslinked polymeric adsorbents with high microporous surface areas are proper for glabridin adsorption. In addition, adsorption capacity of the microporous and mesoporous self-crosslinked polystyrene resin XT2-10 was superior to that of the optimal commercial adsorbent BMKB-1 under the same conditions. However, there is still room for further improvement. Based on this, in the following study, a series of novel hypercrosslinked polymeric adsorbents modified with acetylaniline as the cross-linked bridge (labeled as XT8-0, XT8-4, XT8-6, XT8-8 and XT8-10) were synthesized from macroporous crosslinked chloromethylated polystyrene by adding different quantity of acetylaniline in the Friedel–Crafts reaction. The microporous surface areas of hypercrosslinked polymeric resins XT8 occupied more than 55% of the total BET surface areas and these resins were evaluated for adsorption of glabridin. Among the synthesized five resins, XT8-8 possessed the largest adsorption capacity toward glabridin, and it was superior to the previous synthesized self-crosslinked polystyrene resin XT2-10 and much better than the optimal commercial resin BMKB-1. The isotherms could be fitted by Freundlich model and the adsorption was shown to be an exothermic process. The kinetic curves could be characterized by pseudo-second-order rate equation and the adsorption rate of glabridin on XT8-8 was controlled by both intraparticle diffusion and external diffusion. The enthalpy ΔH, Gibb’s free energy ΔG and entropy ΔS were calculated to be negative. The reusability of the modified resins was also assessed and the modified resins exhibited considerable reusability. The remarkable adsorption behaviors of XT8-8 were due to its suitable structural design and modification. The hypercrosslinked resins being developed were promising alternatives to commercial adsorbents for adsorbing glabridin and other flavones from herbal plants.

Different ionic liquid modified hypercrosslinked polystyrene resin for purification of catechins from aqueous solution

A series of different ionic liquid modified hypercrosslinked polystyrene resins were prepared and evaluated for their adsorption properties where benzimidazole modified hypercrosslinked polystyrene resins exhibited best selectivity against catechins comparison with others ionic liquid modified hypercrosslinked resins and commercial resins. The maximum adsorption capacity of Benzimidazole/Hyper are up to 75.3mg/g for (−)-epigallocatechin gallate and 101.7mg/g for (−)-epicatechin. The pseudo-second-order kinetic equation and intra-particle diffusion model could describe the entire adsorption process of (−)-epigallocatechin gallate and (−)-epicatechin onto ionic liquid modified hypercrosslinked resins. Isothermal equilibrium curves showed a good fitness with the Langmuir and Freundlich models. Evaluated thermodynamic parameters revealed that adsorption was spontaneous and endothermic. The results from the sequential adsorption-desorption cycles showed that Benzimidazole/Hyper resins held good desorption and reusability. The adsorption mechanism was indicated to be the synergistic effect of molecular sieving effect, multiple adsorption interactions and specific surface area. In addition, the steric hindrance of ionic liquid functional group in the hypercrosslinked polymeric resins was a crucial factor for the order of the adsorption capacity.

Integrated adsorptive technique for efficient recovery of m-cresol and m-toluidine from actual acidic and salty wastewater

An integrated adsorptive technique combining an m-cresol adsorption unit, an acid retardation unit and an m-toluidine adsorption unit in sequence was designed to recover m-cresol and m-toluidine from highly acidic and salty m-cresol manufacturing wastewater. In the first column packed with hypercrosslinked polymeric resin (NDA-99), most m-cresol was captured through π-π and hydrogen-bonding interactions as well as the salting-out effect, while m-toluidine was not absorbed due to protonation. To separate acid from salt, an acid retardation unit was introduced successively to adsorb sulfuric acid by strong base anion exchange resin (201×7). After the acid retardation unit and mild neutralization reaction, the last column filled with NDA-99 was applied to trap neutral m-toluidine from the salty effluent. Moreover, the eluent of the acid retardation unit was utilized as the regenerant to recover m-toluidine, and the recycled high-acidity and low-salinity solution of m-toluidine was directly used to produce m-cresol as the raw material. Therefore, the proposed method not only efficiently recycled m-cresol and m-toluidine, but also reduced the consumption of alkali dramatically (saving 0.1628t/t wastewater). These findings will inspire design of integrated adsorptive techniques for treating complex organic wastewater with high efficiency and low cost.

The prediction of adsorption isotherms of ester vapors on hypercrosslinked polymeric adsorbent

Adsorption isotherms of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate and ethyl propionate on hypercrosslinked polymeric resin (ND- 100) were measured at 303K, 318K and 333K,respectively, and well fitted by Dubinin–Astakhov (DA) equation. The plots of the adsorbed volume (qv) versus the adsorption potential (e) at three different temperatures all fell basically onto one single curve for every ester. A predicted model based on DA equation was obtained on the basis of adsorption equilibrium data of methyl acetate, ethyl acetate and ethyl propionate at 318K. The model equation successfully predicted the adsorption isotherms of methyl acetate, ethyl acetate and ethyl propionate on ND-100 at 303K, and 333K, and also gave accurate predictive results for adsorption isotherms of the other two ester compounds (propyl acetate and isopropyl acetate) on ND-100 at 303K, 318K and 333K. The results proved the effectiveness of DA model for predicting the adsorption isotherms of ester compounds onto ND-100. In addition, the relationship between physico-chemical properties of adsorbates and their adsorption properties was also investigated. The results showed that molecular weight, molar volume and molar polarizability had good linear correlations with the parameter E (which represents adsorption characteristic energy) of DA equation.

Organic solvent and temperature-enhanced ion chromatography-high resolution mass spectrometry for the determination of low molecular weight organic and inorganic anions

There has recently been increased interest in coupling ion chromatography (IC) to high resolution mass spectrometry (HRMS) to enable highly sensitive and selective analysis. Herein, the first comprehensive study focusing on the direct coupling of suppressed IC to HRMS without the need for post-suppressor organic solvent modification is presented. Chromatographic selectivity and added HRMS sensitivity offered by organic solvent-modified IC eluents on a modern hyper-crosslinked polymeric anion-exchange resin (IonPac AS18) are shown using isocratic eluents containing 5–50mM hydroxide with 0–80% methanol or acetonitrile for a range of low molecular weight anions (<165Da). Comprehensive experiments on IC thermodynamics over a temperature range between 20–45°C with the eluent containing up to 60% of acetonitrile or methanol revealed markedly different retention behaviour and selectivity for the selected analytes on the same polymer based ion-exchange resin. Optimised sensitivity with HRMS was achieved with as low as 30–40% organic eluent content. Analytical performance characteristics are presented and compared with other IC-MS based works. This study also presents the first application of IC-HRMS to forensic detection of trace low-order anionic explosive residues in latent human fingermarks.

Synthesis, characterization, and adsorption properties of ionic liquid-modified hypercrosslinked polystyrene resins

Ionic liquid modified hypercrosslinked polymeric resins were synthesized and their adsorptive characteristics for catechin were studied.

Neural networks and differential evolution algorithm applied for modelling the depollution process of some gaseous streams.

The depollution of some gaseous streams containing n-hexane is studied by adsorption in a fixed bed column, under dynamic conditions, using granular activated carbon and two types of non-functionalized hypercross-linked polymeric resins. In order to model the process, a new neuro-evolutionary approach is proposed. It is a combination of a modified differential evolution (DE) with neural networks (NNs) and two local search algorithms, the global and local optimizers, working together to determine the optimal NN model. The main elements that characterize the applied variant of DE consist in using an opposition-based learning initialization, a simple self-adaptive procedure for the control parameters, and a modified mutation principle based on the fitness function as a criterion for reorganization. The results obtained prove that the proposed algorithm is able to determine a good model of the considered process, its performance being better than those of an available phenomenological model.

Adsorption equilibrium and dynamics of gasoline vapors onto polymeric adsorbents

The emission of gasoline vapors is becoming a significant environmental problem especially for the population-dense area and also results in a significant economic loss. In this study, adsorption equilibrium and dynamics of gasoline vapors onto macroporous and hypercrosslinked polymeric resins at 308 K were investigated and compared with commercial activated carbon (NucharWV-A 1100). The results showed that the equilibrium and breakthrough adsorption capacities of virgin macroporous and hypercrosslinked polymeric resins were lower than virgin-activated carbon. Compared with origin adsorbents, however, the breakthrough adsorption capacities of the regenerated activated carbon for gasoline vapors decreased by 58.5 % and 61.3 % when the initial concentration of gasoline vapors were 700 and 1,400 mg/L, while those of macroporous and hypercrosslinked resins decreased by 17.4 % and 17.5 %, and 46.5 % and 45.5 %, respectively. Due to the specific bimodal property in the region of micropore (0.5-2.0 nm) and meso-macropore (30-70 nm), the regenerated hypercrosslinked polymeric resin exhibited the comparable breakthrough adsorption capacities with the regenerated activated carbon at the initial concentration of 700 mg/L, and even higher when the initial concentration of gasoline vapors was 1,400 mg/L. In addition, 90 % of relative humidity had ignorable effect on the adsorption of gasoline vapors on hypercrosslinked polymeric resin. Taken together, it is expected that hypercrosslinked polymeric adsorbent would be a promising adsorbent for the removal of gasoline vapors from gas streams.

Adsorption of n-hexane vapor by macroporous and hypercrosslinked polymeric resins: Equilibrium and breakthrough analysis

The adsorption behaviors of n-hexane vapor onto macroporous and hypercrosslinked polymeric resins were investigated. All adsorption isotherms were nonlinear and well fitted with Dubinin–Astakov equation. The equilibrium adsorption data showed that the adsorption capacities of hypercrosslinked polymeric resin (Hyper-resin) were superior to macroporous polymeric resin (Macro-resin) for lower concentration of n-hexane; however, Macro-resin had higher adsorption capacities than Hyper-resin for higher concentration of hexane. The isosteric enthalpies of adsorption for n-hexane were calculated. The Hyper-resin exhibited much higher values of △Hst for n-hexane than Macro-resin at the whole loading studied, indicating that the interaction force of n-hexane adsorption onto Hyper-resin was larger than Macro-resin. The consecutive column adsorption–desorption cycles were carried out to investigate the dynamic adsorption characteristics. The results revealed that the breakthrough adsorption capacities of n-hexane onto the virgin Hyper-resin were about 105% and 43% higher than those onto the virgin Macro-resin when the initial concentrations of n-hexane were 85mg/g and 510mg/g, respectively. Due to higher regeneration efficiency, however, the breakthrough capacities of the regenerated Macro-resin were higher than those of the regenerated Hyper-resin for the adsorption of higher concentration n-hexane.

Evaluating Adsorptive Separation of Aniline from Aqueous Solution by an Aminated Hypercrosslinked Polymer

In the present work, a modified hypercrosslinked polymeric resin (AH-1) with tertiary amino groups was adopted for adsorbing aniline from aqueous solution, and a traditional hypercrosslinked polymeric adsorbent NDA-100 was selected for comparison. Favorable aniline adsorption was observed at higher solution pH in the range of 5–11, and a further decrease of solution pH resulted in a marked decrease of adsorption capacity. The fact that AH-1 had higher adsorption capacity than NDA-100, would be attributed to the enhanced adsorbent-adsorbate interaction for tertiary amino group introduced on the polymeric matrix. The adsorption process was found to be exothermic and data conformed to the Freundlich equation. In addition, the adsorption kinetic study testified that a pseudo-second kinetic mechanism for the adsorption system, and the rate constant of AH-1 was larger than that of NDA-100. More favorable adsorption of aniline onto AH-1 than NDA-100 was further demonstrated by column adsorption runs which indicated that aniline could be effectively removed from aqueous solution by AH-1. Moreover, AH-1 exhibited a better desorption performance than NDA-100, nearly 100% regeneration efficiency for the spent AH-1 was achieved by 5% hydrochloric acid for its repeated use, implying its potential application in associated wastewater treatment.

Kinetic evaluation of phenol/aniline mixtures adsorption from aqueous solutions onto activated carbon and hypercrosslinked polymeric resin (MN200)

Abstract Kinetic adsorption of phenol and aniline from aqueous solution onto activated carbon and hypercrosslinked polymeric resin MN200 were evaluated in single and binary system. Larger phenol and aniline uptakes were observed for activated carbon in single as well as binary system, which can be attributed to the better physical properties of activated carbon, for instance larger surface area and micropore area. The kinetic experimental data was properly fitted by the pseudo-first and pseudo-second-order rate equations. A synergetic effect between solutes was observed since phenol and aniline sorption kinetic in binary system was faster than the individual sorption of each solute in single system, as well as a slight increase in the kinetic parameters obtained in binary system. The particle diffusion rate was defined as the rate limiting mechanism in the singles and binary system for phenol and aniline kinetic adsorption on both adsorbents. Two steps were markedly defined by the Weber and Morris intraparticle diffusion analysis for phenol and aniline onto both adsorbents. In binary systems, the intraparticle diffusion was influenced by the physical properties of adsorbents.