Adsorption thermodynamics and kinetic investigation of aromatic amphoteric compounds onto different polymeric adsorbents.

The adsorption behavior of p-aminobenzoic acid and o-aminobenzoic acid onto the different polymeric adsorbents was systematically investigated as a function of the solution concentration and temperature. Experimental results indicated that the equilibrium adsorption data of the four polymeric adsorbents fitted well in the Freundlich isotherm. The adsorption capacity of multi-functional polymeric adsorbent NJ-99 was the highest, which might be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of aminobenzoic acid. The adsorption capacity of o-aminobenzoic acid onto any adsorbent was higher than p-aminobenzoic acid. Thermodynamic studies suggested the exothermic, spontaneous physical adsorption process. Adsorption kinetics results showed that the adsorption followed the pseudo-second-order kinetics model and the intraparticle mass transfer process was the rate-controlling step.

Microwave-assisted regeneration of hypercrosslinked polymeric adsorbent saturated with nitrophenols.

Thermal regeneration of hypercrosslinked polymeric adsorbent (HPA) was performed at 67 degrees C. Experiments were carried out using a multimode microwave oven operating at 2450 MHz and a thermostatic water bath so as to compare the effect of the different heating mechanisms on the regeneration efficiency of the HPA saturated with nitrophenols. The temperature rise action of the heterogeneous regeneration system under microwave irradiation was described. Additionally, a complete structure and chemical characterization of the regenerated HPA was also carried out in order to study the influence of the subsequent regeneration cycles on the structure and the adsorption capacities of the adsorbents. Structure characterization of the regenerated HPA was accomplished by means of the analysis of FTIR spectra.

[Cooperative adsorption of 1-naphthol and 1-naphthylamine onto hyper-crosslinked polymeric adsorbents].

Cooperative simultaneous adsorptions of 1-naphthol and 1-naphthylamine from aqueous solutions on hyper-cross-linked polymeric adsorbents (NDA103 and NDA100) were investigated. The results indicate that at the higher equilibrium concentrations, the total uptake amounts of 1-naphthol and 1-naphthylamine in binary systems (1-naphthol: 1-naphthylamine = 3:1, 1:1, 1:3) are obvious larger than the pure uptake amounts in single systems, and a large excess was noted on the particle surface at saturation, which is presumably due to the cooperative effect primarily arisen from the hydrogen bonding or weak acid-base interaction between 1-naphthol and 1-naphthylamine. The adsorption isotherms for them in both single and binary systems can be well fitted by Langmuir equation. The increasing temperature from 293 K to 313 K puts much more effect on the cooperative coefficient of simultaneous adsorption of 1-naphthylamine and 1-naphthol on NDA103 than on NDA100. The amino groups on NDA103 enhance the adsorption affinity as well as the cooperative coefficient of 1-naphthol.

Effects of the surface chemistry of macroreticular adsorbents on the adsorption of 1-naphthol/1-naphthylamine mixtures from water.

The adsorption behaviors of 1-naphthol, 1-naphthylamine and 1-naphthol/1-naphthylamine mixtures in water over two macroreticular adsorbents were investigated in single or binary batch systems at 293 K, 303 K and 313 K respectively. All the adsorption isotherms in the studied systems can be adequately fitted by Langmuir model. In the case of aminated macroreticular adsorbent NDA103, 1-naphthol is adsorbed to a larger extent than 1-naphthylamine; while, the opposite trend is found for nonpolar macroreticular adsorbent NDA100. It is noteworthy that at higher temperature (303 K and 313 K), the total uptake amounts of 1-naphthol and 1-naphthylamine in all binary-component systems are obvious larger than the pure uptake amounts in single-component systems, which is presumably due to the cooperative effect primarily arisen from the hydrogen-bonding interaction between the loaded 1-naphthol and 1-naphthylamine molecules. The simultaneous adsorption systems were confirmed to be helpful to the selective adsorption towards 1-naphthol according to the larger selective index.

Competitive and cooperative adsorption behaviors of phenol and aniline onto nonpolar macroreticular adsorbents.

The adsorption behaviors of phenol and aniline on nonpolar macroreticular adsorbents (NDA100 and Amberlite XAD4) were investigated in single or binary batch system at 293K and 313K respectively in this study. The results indicated that the adsorption isotherms of phenol and aniline on both adsorbents in both systems fitted well Langmuir equation, which indicated a favourable and exothermic process. At the lower equilibrium concentrations, the individual amount adsorbed of phenol or aniline on macroreticular adsorbents in single-component systems was higher than those in binary-component systems because of the competition between phenol and aniline towards the adsorption sites. It is noteworthy, on the contrast, that at higher concentrations, the total uptake amounts of phenol and aniline in binary-component systems were obviously larger than that in single-component systems, and a large excess was noted on the adsorbent surface at saturation, which is presumably due to the cooperative effect primarily arisen from the hydrogen bonding or weak acid-base interaction between phenol and aniline.

Adsorption of catechol from aqueous solution by aminated hypercrosslinked polymers.

Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.

Binary competitive adsorption of naphthalene compounds onto an aminated hypercrosslinked macroporous polymeric adsorbent.

An aminated hypercrosslinked macroporous polymeric adsorbent was synthesized and characterized. Adsorption isotherms for 1-amino-2-naphthol-4-sulfonic acid (1,2,4-acid) and 2-naphthol obtained from various binary adsorption environments can be well fitted by Freundlich equation, which indicated a favorable adsorption process in the studied range. Adsorption for 1,2,4-acid was an endothermic process in comparison with that for 2-naphthol of an exothermic process. 2-naphthol molecules put a little influence on the adsorption capacity for 1,2,4-acid. However, the adsorption to 1,2,4-acid depressed that to 2-naphthol in a large extent for the stronger electrostatic interaction between 1,2,4-acid and adsorbent. The predominant mechanism can be contributed to the competition for adsorption sites. And the simultaneous environment was confirmed to be helpful to the selective adsorption towards 1,2,4-acid based on the larger selectivity index.

Thermodynamic study of adsorption of phenolic compounds onto Amberlite XAD-4 polymeric adsorbents and its acetylized derivative MX-4.

Adsorption equilibrium isotherms of phenolic compounds, phenol, p-cresol, p-chlorophenol and p-nitrophenol, from aqueous solutions by Amberlite XAD-4 polymeric adsorbent and its acetylized derivative MX-4 within temperature range of 283-323K were obtained and fitted to the Freundlich isotherms. The capacities of equilibrium adsorption for all four phenolic compounds from their aqueous solutions increased around 20% on the acetylized resin, which may be contributed to the specific surface area and the partial polarity on the network. Estimations of the isosteric enthalpy, free energy, and entropy for the adsorption process were reported.