Weiben Yang

Adsorption Characteristics of Fumaric Acid onto Weakly Basic Hypercrosslinked Polystyrene Ion-exchangers

A new weakly basic ion-exchanger (called XC-11), with a hypercrosslinked macroporous polystyrene matrix and a high specific surface area, was synthesized. When traditional weakly basic ion-exchange resins were employed in adsorption experiments, it was found that their sphericity after attrition decreased drastically when they were used ten times cyclically to adsorb and desorb fumaric acid from actual manufacturing effluent. This indicated that a traditional weakly basic exchange resin could not be applied in practice for the recovery of fumaric acid from industrial wastewater. However, the mechanical strengths of the self-synthesized new weakly basic ion-exchanger XC-11 and the hypercrosslinked polymeric adsorbent NDA-150 remained virtually unchanged under the same conditions, indicating their feasibility for practical applications. Thus, the adsorption of fumaric acid from aqueous solutions onto XC-11 and the commercially available hypercrosslinked polymeric adsorbent (NDA-150) taken as a reference was investigated from both a dynamic and thermodynamic standpoint. Favourable adsorption behaviour towards fumaric acid was observed with both adsorbents, the equilibrium adsorption data obtained being very well fitted by the Freundlich model. The corresponding Freundlich constants, KF, and free energy changes, ΔG, indicated that the adsorption capacity of XC-11 towards fumaric acid was greater than that of NDA-150. The pseudo-first-order and pseudo-second-order kinetic models were applied to describe the kinetic data, with the pseudo-second-order model providing a perfect fit. It was also found that the adsorption of fumaric acid onto XC-11 proceeded faster than the corresponding process onto NDA-150.

The Adsorption of the Water-soluble Dye X-BR onto Three Types of Resin: Behaviour and Mechanism

The adsorption of the water-soluble Reactive dye Brilliant Blue X-BR onto three different types of resins was investigated. The study focused on the static equilibrium adsorption behaviours and other factors influencing the adsorption process. The three resins exhibited different adsorption behaviours and mechanisms for the adsorption of X-BR from aqueous solution. The adsorption isotherms associated with the acrylic ester resin YWB-50 could be well fitted by the Langmuir equation, while those of the resins NDA-150 and D-301 could be well fitted by the Freundlich equation. The adsorption dynamics and desorption process were also investigated as a means of further exploring the difference between the adsorption behaviours and mechanisms on the three resin types.

Recovery of the Dye Intermediate DNDS from Aqueous Solution by Adsorption onto Resins

Four kinds of resins were investigated for the recovery of 4,4‘-dinitrostilbene-2,2’-disulphonic acid (DNDS), which is present as a pollutant in wastewater, and their adsorption behaviour and mechanisms assessed. One of the resins, YWB-38, exhibited much better adsorption properties towards DNDS than the other two commercial acrylic ester resins XAD-7 and HP2MG. The Langmuir and Freundlich adsorption models were fitted to the experimental equilibrium data when the Langmuir model was found to provide a better fit for all resins over the temperature range studied. The investigation indicates that hydrophobic interaction provides the main mechanism in the adsorption of DNDS onto XAD-4 resin and that such interaction decreases significantly when additional methanol (10%) is added to the DNDS solutions. While the main interaction between the acrylic ester resin and adsorbate is hydrogen bonding, this can be enhanced to some extent by increasing acid concentration. Adsorption dynamics, column adsorption and desorption processes were also investigated to explore the differences in adsorption behaviour and mechanism on the polystyrene resin XAD-4 and acrylic ester resins.