Fei Zhenghao

Equilibrium adsorption of single component and binary mixtures of aromatic compounds onto a polyfunctional hypercrosslinked polymeric adsorbent

A polyfunctional hypercrosslinked polymeric adsorbent, LA-8, was synthesized and characterized. It was first used to investigate the adsorption properties of 1-amino-2-naphthol-4-sulphonic acid (1,2,4-acid), including the corresponding adsorption isotherms, thermodynamics and binary competitive adsorption with 2-naphthol. The Freundlich model gave good fits to both the single and binary adsorption isotherms, indicating an endothermic and favourable adsorption process. The positive value of ΔH0 for the single solute system was in the range of 30–60 kJ/mol showing the existence of integrated processes involving chemical interaction. The values of ΔG0 demonstrated the spontaneous nature of the adsorption process while the value of ΔS0 showed increased randomness at the solid–solution interface, thereby indicating the presence of stoichiometric displacement. Both ΔH0 and ΔS0 appeared to vary linearly with increased solid loading, qe. Pre-adsorbed 2-naphthol molecules supplied another adsorption site for 1,2,4-acid, despite the existence of an antagonistic interaction with 2-naphthol. In simultaneous processes, the mechanism for 1,2,4-acid adsorption probably mainly involved van der Waals forces and hydrogen-bonding interaction. Furthermore, the adsorption of a greater amount of 2-naphthol onto the solid phase demonstrated the occurrence of interaction between the tested binary solutes. It was concluded that direct competition for adsorption sites was the dominant competitive mechanism.

Adsorption Characteristics of Phenolic Compounds onto a New Hypercrosslinked Polymeric Resin Containing the 2-Carbonylbenzoyl Group (ZH-01)

A new hypercrosslinked polymeric adsorbent (ZH-01) for the adsorption and removal of phenolic compounds from their aqueous solutions was prepared. Batch kinetic studies and comparisons in adsorption capacities between XAD-4, AM-1 and ZH-01 for 800 mg/l phenol were performed, indicating the advantages of ZH-01 for adsorbing phenol, p-cresol and p-nitrophenol. Both the dynamic and thermodynamic studies concluded that the adsorption of phenol and p-cresol onto ZH-01 involved chemisorption while p-nitrophenol was adsorbed physically onto ZH-01. The latter process demonstrated the homogeneous nature of the surface of ZH-01 adsorbent. Mini-column adsorption studies for phenol on ZH-01 showed that its breakthrough capacity and total capacity were 2.38 mmol/g and 3.05 mmol/g, respectively. Methanol exhibited an excellent performance in desorbing phenol from ZH-01.

Study of the Adsorption Thermodynamics and Kinetics of Lipoic Acid onto Three Types of Resin

The adsorption of lipoic acid on three different types of resin was compared. Studies of the adsorption thermodynamics and kinetics of lipoic acid onto XAD-4, NDA-100 and ND-90 resins were carried out via static experiments. The results showed that the polar groups and micropore ranges associated with the resins played a significant role in the adsorption of lipoic acid. Such processes were exothermic and involved physical adsorption. The adsorption of lipoic acid onto XAD-4 resin corresponded to the formation of a Langmuir monolayer, with the adsorption velocity appearing to follow first-order kinetics. The adsorption data of lipoic acid onto NDA-100 and ND-90 resins were also well fitted by the Langmuir isotherm, which was associated with capillary condensation and volume filling of micropores besides monolayer adsorption. In contrast, the adsorption of lipoic acid onto NDA-100 and ND-90 resins involved two pore ranges: macropore + mesopore and micropore. The adsorption velocities for the two ranges followed first-order kinetics.

Chemisorption Characteristics of 2,4-Dichlorophenol in Aqueous Solution onto Different Adsorbents

The adsorption properties towards 2,4-dichlorophenol of several adsorption resins, viz. ZH-01, ZH-02 and ZH-03 respectively modified with different functional groups, and of granular activated carbon (GAC) have been compared experimentally with those of Amberlite XAD-4. This paper focuses on the static equilibrium adsorption behaviours and the confirmation of chemisorption characteristics. An equation relating the amount chemisorbed and the assumed chemisorption equilibrium concentration of adsorbate in the aqueous solution was established. This shows that the data may be fitted perfectly by the Langmuir equation. The adsorption capacities measured at different temperatures and the static desorption efficiency reveal that the adsorption of 2,4-dichlorophenol from water onto ZH-01, ZH-02, ZH-03 or GAC occurs via a simultaneous process involving physical adsorption and chemical reaction.