Jianhan Huang

Adsorption of CO2, CH4, and N2 on Ordered Mesoporous Carbon: Approach for Greenhouse Gases Capture and Biogas Upgrading

Separation of CO₂ and N₂ from CH₄ is significantly important in natural gas upgrading, and capture/removal of CO₂, CH₄ from air (N₂) is essential to greenhouse gas emission control. Adsorption equilibrium and kinetics of CO₂, CH₄, and N₂ on an ordered mesoporous carbon (OMC) sample were systematically investigated to evaluate its capability in the above two applications. The OMC was synthesized and characterized with TEM, TGA, small-angle XRD, and nitrogen adsorption/desorption measurements. Pure component adsorption isotherms of CO₂, CH₄, and N₂ were measured at 278, 298, and 318 K and pressures up to 100 kPa, and correlated with the Langmuir model. These data were used to estimate the separation selectivities for CO₂/CH₄, CH₄/N₂, and CO₂/N₂ binary mixtures at different compositions and pressures according to the ideal adsorbed solution theory (IAST) model. At 278 K and 100 kPa, the predicted selectivities for equimolar CO₂/CH₄, CH4/N₂, and CO₂/N₂ are 3.4, 3.7, and 12.8, respectively; and the adsorption capacities for CH₄ and CO₂ are 1.3 and 3.0 mmol/g, respectively. This is the first report of a versatile mesoporous material that displays both high selectivities and large adsorption capacities for separating CO₂/CH₄, CH₄/N₂, and CO₂/N₂ mixtures.

Removal of p-nitrophenol by a water-compatible hypercrosslinked resin functionalized with formaldehyde carbonyl groups and XAD-4 in aqueous solution : A comparative study

Chloromethylated styrene-divinylbenzene copolymers were post-crosslinked through Fredel-Crafts alkylation reaction and a water-compatible hypercrosslinked resin HJ-1 was developed successfully. It can be wetted directly by water and can be used without any wetting process. It was applied to remove p-nitrophenol in aqueous solution in comparison with the commercial Amberlite XAD-4 resin. Their adsorption behaviors for p-nitrophenol were conducted and it was found the adsorption dynamics obeyed the pseudo-second-order rate equation and the intra-particle diffusion was the rate-limiting step. The adsorption isotherms can be correlated to Freundlich isotherm and the adsorption capacity onto HJ-1 resin was much larger than XAD-4. The maximum adsorption capacity of p-nitrophenol for HJ-1 resin was measured to be 179.4 mg/g with the equilibrium concentration at 178.9 mg/l and the maximum removal percentage was predicted to be 98.3%. The adsorption thermodynamic parameters were calculated and the adsorption was mainly driven by enthalpy change. The micropore structure, the size matching between the pore diameter of HJ-1 resin and the molecular size of p-nitrophenol, and polarity matching between the formaldehyde carbonyl groups of HJ-1 resin and p-nitrophenol bring the larger adsorption capacity and higher adsorption affinity.

Synthesis, characterization and adsorption properties of diethylenetriamine-modified hypercrosslinked resins for efficient removal of salicylic acid from aqueous solution.

We report an effective approach for tailoring the pore textural properties and surface polarity of a hypercrosslinked resin to enhance its adsorption capacity and selectivity for removing salicylic acid from aqueous solution. Four hypercrosslinked resins were synthesized by controlling the reaction time of the self Friedel-Crafts reaction of chloromethylated polystyrene-co-divinylbenzene, and then modified with diethylenetriamine to adjust their surface polarity. The resins were characterized with N(2) adsorption for pore textural properties, Fourier transform infrared spectroscopy (FT-IR) for surface functional groups, chemical analysis for residual chlorine content and weak basic exchange capacity. Adsorption equilibrium, kinetics and breakthrough performance were determined for the removal of salicylic acid from aqueous solution on a selected resin HJ-M01. The equilibrium adsorption capacity of salicylic acid on HJ-M01 is significantly higher than that on its precursor HJ-11 and a few commercial adsorbents including AB-8, XAD-4 and XAD-7. The dynamic adsorption capacity of salicylic acid on HJ-M01 was found to be 456.4 mg/L at a feed concentration of 1000 mg/L and 294 K. The used resin could be fully regenerated with 1% sodium hydroxide solution. The hypercrosslinked resins being developed were promising alternatives to commercial adsorbents for removing salicylic acid and other volatile organic compounds (VOCs) from aqueous solution.

Adsorption of Rhodamine B on two novel polar-modified post-cross-linked resins: Equilibrium and kinetics.

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 578.2mg/g and 328.7mg/g, respectively, at an equilibrium concentration of 100mg/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.

Adsorption behaviors of three polymeric adsorbents with amide groups for phenol in aqueous solution.

Efficient removal of phenol and its derivatives from wastewater is of significant environmental concern. In the present study, the adsorption behaviors of three polymeric adsorbents with amide groups, PMVBA, PMVBC, and PMVBU, for phenol were investigated in aqueous solution. The adsorption in relation to the solution pH value was discussed and the neutral pH was optimum. The adsorption dynamic cure was determined and it was shown that the pseudo-second-order rate equation characterized the adsorption better and the intraparticle diffusion was the rate-limiting step. The adsorption isotherms were measured and correlated to Freundlich isotherms, and it was shown that PMVBU held the largest adsorption capacity. The adsorption thermodynamic parameters were calculated and it was seen that the adsorption enthalpy of phenol onto the three adsorbents follows the order PMVBU>PMVBA>PMVBC. Analysis of the adsorption mechanism suggested that hydrogen bonding played a predominant role and multiple hydrogen bonding was involved for phenol and PMVBU.

Adsorption behaviors of a novel carbonyl and hydroxyl groups modified hyper-cross-linked poly(styrene-co-divinylbenzene) resin for β-naphthol from aqueous solution

A series of novel hyper-cross-linked resins were synthesized from macroporous cross-linked chloromethylated poly(styrene-co-divinylbenzene) by adding different dosage of hydroquinone in Friedel-Crafts reaction. The results of the pore structures revealed that the prepared resins possessed micropores, mesopores and macropores, and the chloromethyl groups and the uploaded hydroquinone were partly oxidized according to the results of Fourier-transformed infrared ray spectra. Among these hydroquinone modified resins, HJ-Y06 resin held the largest adsorption capacity for beta-naphthol, and its adsorption capacity was comparable with XAD-4 while much larger than X-5. The adsorption kinetics could be characterized by pseudo-second-order rate equation and intra-particle diffusion model was the rate-limiting step at the initial process. The adsorption was favorable at solution pH lower than 6.5. The adsorption isotherms could be fitted by Langmuir model and the adsorption was an endothermic process. Hydrogen bonding between formaldehyde carbonyl and quinone carbonyl groups on HJ-Y06 and phenolic hydroxyl groups of beta-naphthol was the main driving force for the adsorption.

Application of an easily water-compatible hypercrosslinked polymeric adsorbent for efficient removal of catechol and resorcinol in aqueous solution

An easily water-compatible hypercrosslinked resin HJ-1 was developed for adsorbing catechol and resorcinol in aqueous solution in this study. Its adsorption performances for catechol and resorcinol were investigated in aqueous solution by using the commercial Amberlite XAD-4 as a reference. The adsorption dynamic curves were measured and the adsorption obeyed the pseudo-second-order rate equation of Boyer and Hsu. The adsorption isotherms were scaled and Freundlich isotherm model characterized the adsorption better. The adsorption thermodynamic parameters were calculated and the adsorption was an exothermic, favorable, and more ordered process. The fact that the adsorption capacity of catechol was larger than resorcinol and the adsorption enthalpy of catechol was more negative than resorcinol can be explained in terms of the solubility and the polarity of two adsorbates.

Phenol-modified hyper-cross-linked resins with almost all micro/mesopores and their adsorption to aniline

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=169.2mg/g). The adsorption was very fast, 40min was enough for the equilibrium, and the micropore diffusion model described the kinetic data very well.

Adsorptive separation studies of ethane-methane and methane-nitrogen systems using mesoporous carbon.

Adsorptive separations of C(2)H(6)/CH(4) and CH(4)/N(2) binary mixtures are of paramount importance from the energy and environmental points of view. A mesoporous carbon adsorbent was synthesized using a soft template method and characterized with TEM, TGA, and nitrogen adsorption/desorption. Adsorption equilibrium and kinetics of C(2)H(6), CH(4), and N(2) on the mesoporous carbon adsorbent were determined at 278, 298, and 318 K and pressures up to 100 kPa. The adsorption capacities of C(2)H(6) and CH(4) on the mesoporous carbon adsorbent at 298 K and 100 kPa are 2.20 mmol/g and 1.05 mmol/g, respectively. Both are significantly higher than those of many adsorbents including pillared clays and ETS-10 at a similar condition. The equilibrium selectivities of C(2)H(6)/CH(4) and CH(4)/N(2) at 298 K are 19.6 and 5.8, respectively. It was observed that the adsorption of C(2)H(6), CH(4), and N(2) gases on the carbon adsorbent was reversible with modest isosteric heats of adsorption, which implies that this carbon adsorbent can be easily regenerated in a cyclic adsorption process. These results suggest that the mesoporous carbon studied in this work is a promising alternative adsorbent for the separations of C(2)H(6)/CH(4) and CH(4)/N(2) gas mixtures.

Surface modification on a hyper-cross-linked polymeric adsorbent by multiple phenolic hydroxyl groups to be used as a specific adsorbent for adsorptive removal of p-nitroaniline from aqueous solution

A hyper-cross-linked polymeric adsorbent functionalized with multiple phenolic hydroxyl groups HJ-03 was prepared in this study and its adsorptive characteristics for p-nitroaniline from aqueous solution were studied as compared with Amberlite XAD-4. The adsorption of p-nitroaniline was sensitive to the solution pH and the maximum adsorption capacity was observed at pH of 3.5. The adsorption kinetics obeyed the pseudo-second-order rate equation and the adsorption isotherms could be correlated to Langmuir isotherm model. The adsorption enthalpy, adsorption free energy, and adsorption entropy were calculated to be negative and the adsorption was mainly driven by enthalpy change. The polarity matching between HJ-03 resin and p-nitroaniline, the pore structure of HJ-03, and the size matching between the pore diameter of HJ-03 and the molecular size of p-nitroaniline brought the larger adsorption capacity and higher adsorption affinity.