Dajian Huang

Chitosan-g-poly(acrylic acid) hydrogel with crosslinked polymeric networks for Ni2+ recovery

In this study, chitosan-g-poly(acrylic acid) (CTS-g-PAA) hydrogel with crosslinked polymeric networks was prepared from an aqueous dispersion polymerization and then used as the adsorbent to recover a valuable metal, Ni2+. The adsorption capacity of CTS-g-PAA for Ni2+ was evaluated and the adsorption kinetics was investigated using Voigt-based model and pseudo-second-order model. In addition, the effects of pH values and coexisting heavy metal ions such as Cu2+ and Pb2+ on the adsorption capacity were studied. The results indicate that the as-prepared adsorbent has faster adsorption rate and higher adsorption capacity for Ni2+ recovery, with the maximum adsorption capacity of 161.80 mg g(-1). In a wide pH range of 3-7, the adsorption capacity keeps almost the same, and even under competitive conditions, the adsorption capacity of CTS-g-PAA for Ni2+ is observed to be as high as 54.47 mg g(-1). Finally, the adsorption performance of CTS-g-PAA for Ni2+ in real water sample and the reusability of the as-prepared adsorbent were evaluated, and also the controlled adsorption mechanism was proposed.

Non-covalently functionalized multiwalled carbon nanotubes by chitosan and their synergistic reinforcing effects in PVA films

Multiwalled carbon nanotubes (MWCNTs) were regarded as ideal candidates for fillers in a polymer matrix due to their outstanding mechanical, electrical and thermal properties. A series of nanocomposite films were prepared by a solution casting method introducing chitosan (CS) treated MWCNTs into a poly (vinyl alcohol) (PVA) matrix. The nanocomposites were characterized by field emission scanning electron microscopy and Fourier Transform Infrared Spectroscopy. The results indicated that MWCNTs treated by chitosan dispersed well in the PVA matrix, and the tensile properties and water resistance of nanocomposites were improved greatly compared with neat PVA.

Efficient Adsorption and Recovery of Pb(II) from Aqueous Solution by a Granular pH-Sensitive Chitosan-based Semi-IPN Hydrogel

A series of granular pH-sensitive semi-interpenetrating polymer network (semi-IPN) hydrogels based on chitosan (CTS), acrylic acid (AA) and gelatine (GE) were utilized for the adsorption and recycle of Pb(II) from aqueous solutions. The composite hydrogels have been characterized by FT-IR and TGA. The effects of contact time, pH value and initial Pb(II) concentration on the adsorption were investigated. Results indicated that the adsorption capacity of the hydrogel increased with increasing pH value and initial Pb(II) concentration, and a pH-sensitive adsorption characteristic was presented. The adsorption rate of the semi-IPN hydrogels on Pb(II) is fast with an adsorption rate constant of 14.9790 mg/(g·s), and adsorption equilibrium could be reached within 10 min. The adsorption isotherms of the hydrogels for Pb(II) could be described well by the Langmuir equation, rather than the Freundlich equation. The as-prepared hydrogels showed good reusability with 0.05 mol/l HNO3 solutions as the desorbing agent and 0.1 mol/l NaOH solutions as the regeneration agent, respectively. After five consecutive adsorption-desorption processes, the semi-IPN hydrogel with 20 wt% GE may reach 85.26% of its initial adsorption capacity. In addition, the adsorbed Pb(II) can be quantitatively recovered by simply eluting the hydrogel with dilute HNO3 solution, and a recovery ratio of 89.27% was reached for the semi-IPN hydrogel. The satisfactory adsorption amount is mainly derived from the chelating of functional groups (i.e. –COO− and –NH2) with Pb(II) ions. The hydrogel adsorbents exhibited excellent affinity for Pb(II), and can be applied to treat wastewater containing heavy metal ion and simultaneously recover the valuable metal sources.

Removal of Cu2+ and Zn2+ Ions from Aqueous Solution Using Sodium Alginate and Attapulgite Composite Hydrogels

A series of sodium alginate-g-sodium acrylate/attapulgite (NaAlg-g-PNaA/APT) composite hydrogels were used as adsorbents to adsorb Cu2+ and Zn2+ from aqueous solutions. The effect of common variables including the content of APT, pH value, contact time and initial concentration of metal ions on the adsorption properties of the composite hydrogels for the adsorption of Cu2+ and Zn2+ ions was investigated using a batch adsorption technique. The results show that the composites evaluated have an excellent adsorption capacity and fast adsorption rate for both Cu2+ and Zn2+ ions. Repeated adsorption–desorption experimental results show that the composite hydrogels have a good reusability and stability, and 50% of the original adsorption capacity can be retained after being reused five times. The pseudo-second-order equation and the Langmuir equation best describe the adsorption kinetics and isotherms, respectively.

Adsorption of Congo Red by Poly(Dimethyl Diallyl Ammonium Chloride)/Polyacrylamide Hydrogels with Excellent Acid and Alkali Resistance

Cationic hydrogels, poly(dimethyl diallyl ammonium chloride)/polyacrylamide (PDMDAAC/PAM), were prepared for the removal of congo red (CR) from aqueous solution. Process parameters affecting the adsorption efficiency were systematically investigated. The results showed that the calculated monolayer adsorption capacity of the cationic hydrogels was found to be 200 to 465 mg/g. The hydrogels showed appreciable adsorption capacities within pH range investigated. The adsorption process well obeyed pseudo-second-order kinetics and the Langmuir isotherm. The ion exchange dominated the whole adsorption mechanism. All the information suggests that the as-prepared cationic hydrogels show potential applications in the fields of wastewater treatment for the removal of anionic dyes such as CR.