Qingjian Zhang

Adsorption of aromatic acids on an aminated hypercrosslinked macroporous polymer

Abstract In the present study a hypercrosslinked macroporous polymer CHA-111 was chemically modified by amination with dimethylamine. Adsorption of five aromatic acids on the modified polymer MCH-111 was investigated and adsorption capacities of aromatic acids from aqueous solution increased significantly after amination. The Freundlich and Langmuir isotherm equations were employed to fit the adsorption processes to describe adsorption mechanism. Hydrogen-bonding interaction should be regarded as a fundamental contributor to increasing adsorption capacities of aromatic acids on MCH-111. Surface structure of MCH-111 caused by postcrosslinking reaction will enhance the NPM–matrix interaction and then lead to higher activity of amino group on MCH-111 than a macroporous weakly anion exchanger D301. The negative isosteric enthalpy changes for adsorption of benzenesulfonic acid and naphthalenesulfonic acid indicate an exothermic process on the aminated polymer.

ROLE OF AMINATION OF A POLYMERIC ADSORBENT ON PHENOL ADSORPTION FROM AQUEOUS SOLUTION

Adsorption of seven phenols, one aromatic carboxylic acid and one sulfonated aromatic acid from aqueous solution, by a hypercrosslinked polymeric adsorbent (CHA-111) and the derivative animated by dimethylamine was compared. The results of different adsorption isotherms indicated that amino group on the polymeric matrix played a significant role on adsorption of almost all the employed compounds. For most employed compounds adsorption capacities increase to different degree and significantly for those with lower value of pK(a). It may be attributed to the enhanced adsorbent-adsorbate interaction for amino group introduced on the polymeric matrix. The empirical Freundlich isotherm equation was employed to interpret the adsorbent-adsorbate interaction. The adsorption enthalpy change indicated the uptake of phenols on MCH-111 to be an enhanced physical adsorption because of the hydrogen-bonding interaction. Adsorption kinetic study of phenols on CHA-111 and MCH-111 was also conducted and amino group on the matrix will reduce the adsorption rate for change of pore size distribution and loss of macroprous volume as well as the hydration effect on the surface partly.

Equilibrium and heat of adsorption of diethyl phthalate on heterogeneous adsorbents

Removal of phthalate esters from water has been of considerable concern recently. In the present study, the adsorptive removal performance of diethyl phthalate (DEP) from water was investigated with the aminated polystyrene resin (NDA-101) and oxidized polystyrene resin (NDA-702). In addition, the commercial homogeneous polystyrene resin (XAD-4) and acrylic ester resin (Amberlite XAD-7) as well as coal-based granular activated carbon (AC-750) were chosen for comparison. The corresponding equilibrium isotherms are well described by the Freundlich equation and the adsorption capacities for DEP followed the order NDA-702 > NDA-101 > AC-750 > XAD-4 > XAD-7. Analysis of adsorption mechanisms suggested that these adsorbents spontaneously adsorb DEP molecules driven mainly by enthalpy change, and the adsorption process was derived by multiple adsorbent-adsorbate interactions such as hydrogen bonding, pi-pi stacking, and micropore filling. The information related to the adsorbent surface heterogeneity and the adsorbate-adsorbate interaction was obtained by Dos model. All the results indicate that heterogeneous resins NDA-702 and NDA-101 have excellent potential as an adsorption material for the removal of DEP from the contaminated water.

Sorption enhancement of 1-naphthol onto a hydrophilic hyper-cross-linked polymer resin

A hydrophilic hyper-cross-linked polymer resin NDA-150 was developed to remove 1-naphthol from the contaminated waters. The sorption performance of 1-naphthol on NDA-150 was explored and compared with that on the commercial hydrophobic resin XAD-4. The sorption rates of 1-naphthol onto both of the two resins obey the pseudo-second-order kinetics, and are limited by the successive steps of film diffusion and intraparticle diffusion. The greater sorption rate on XAD-4 than NDA-150 is probably due to the larger average pore diameter of XAD-4. All the adsorption isotherms can be represented by Langmuir equation. The larger capacity and stronger affinity of NDA-150 than XAD-4 probably result from the abundant microporous structure and polar groups of NDA-150. In aqueous phase hydrophobic XAD-4 adsorbs 1-naphthol driven principally by enthalpy change, while the adsorption onto hydrophilic NDA-150 driven mainly by entropy change. The breakthrough and the total sorption capacity of NDA-150 to 1-naphthol were obtained to be 1.10 and 1.58 mmol mL(-1) resin at 293 K, respectively. Nearly 100% regeneration efficiency for the resin was achieved by ethanol at 313 K.

Removal enhancement of 1-naphthol and 1-naphthylamine in single and binary aqueous phase by acid-basic interactions with polymer adsorbents

In the present study removal performance of 1-naphthol and 1-naphthylamine from wastewater by single and binary adsorption was compared. Synergistic effects were investigated in single-solute, binary-solute, and the preloading adsorption systems at 293 K. Two commercial polystyrene adsorbents Amberlite XAD-4, a macroporous adsorbent, and NDA-100, a hyper-cross-linked adsorbent, were employed here for their frequent use in organic pollutants removal from contaminated waters. All the adsorption isotherms of 1-naphthol and 1-naphthylamine on both adsorbents were found to be well represented by the Langmuir equation. Adsorption capacity of the primary solute was enhanced in the presence of the co-solute, arising presumably from the synergistic effect caused by the laterally acid-base interaction between the adsorbed 1-naphthol and 1-naphthylamine molecules. Due to the stronger adsorption affinity of 1-naphthylamine to nonpolar adsorbents, adsorption enhancement of 1-naphthylamine in the presence of 1-naphthol is greater than that of 1-naphthol in the presence of 1-naphthylamine. The greater synergistic effect of 1-naphthol/1-naphthylamine equimolar mixtures on XAD-4 than that on NDA-100 partly results from the larger average pore size of the former adsorbent. A modified extended Langmuir model is proved to well describe the synergistic adsorption of 1-naphthol/1-naphthylamine equimolar mixtures in the binary-solute system. The synergistic coefficient of one adsorbate is linearly correlated with the amount of the other adsorbed on the adsorbent.

Recent Patents on Polymeric Adsorbents and their Derivatives for Pollutants Removal from Aqueous Media : A Mini-Review

Water pollution by organic and/or inorganic pollutants has gained considerable attention all over the world. In the past decades, adsorption has been proposed as one of the most effective and simplest approaches to remove pollutants from contaminated waters, and polymer-based adsorbents have been widely used as efficient adsorbents except for activated carbon. Here, we reviewed recent patents on preparation of polymeric adsorbents and their derivatives as well as their application in pollutants removal from waters. Here, we classify the polymer-based adsorbents as four types for review: polymeric porous adsorbents; their chemically modified derivatives, polymer-coated inorganic hybrid adsorbents, and polymeric chelating adsorbents. Some of the features on their preparation, properties, and applications were illustrated by case studies. The forthcoming development in the given field was also discussed.