In this study, magnetic chitosan (CS) beads of ∼200 nm in diameter were successfully prepared by a facile one-step method. The resultant composite Fe3O4–CS was characterized using transmission electron microscopy (TEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Its adsorption toward Cu(II) ions was investigated as a function of solution pH, CS dosage, Cu(II) concentration, and contact time. The maximum capacity of Fe3O4–CS was 129.6 mg of Cu(II)/g of beads (617.1 mg/g of CS). More attractively, the adsorption equilibrium could be achieved within 10 min, which showed superior properties among the available CS-based adsorbents. Continuous adsorption–desorption cyclic results demonstrated that Cu(II)-loaded Fe3O4–CS can be effectively regenerated by ethylenediaminetetraacetic acid (EDTA) solution, and the regenerated composite beads could be employed for repeated use without significant capacity loss. Additionally, Fe3O4–CS beads can be readily separated from water within 30 s under a low magnetic field (<0.035 T).Keywords: Cu(II); fast removal; Fe3O4; magnetic chitosan beads;

A new polymeric nanocomposite photocatalyst A15-CdS with large spherical beads (0.70–0.80 mm in diameter) was fabricated for efficient Rhodamine B (RhB) photodegradation with facile separation during cyclic runs, and photocorrosion, a congenital drawback of CdS, was successfully inhibited for A15-CdS. The nanocomposite catalyst was obtained by impregnating CdS nanoparticles within porous polymeric cation exchanger A15 through a facile inner-surface deposition. CdS nanoparticles (<20 nm) immobilized in A15 were deliberately distributed within an outside ring-like region of 40–50 μm in depth, which is dominant for photoreaction because visible light is not expected to permeate through the inner region of nontransparent A15. As expected, efficient RhB photodegradation by A15-CdS was achieved under visible light irradiation, and large-size A15-CdS beads are expected to result in their facile separation from solution for repeated use. More significantly, negligible photocorrosion for the hybrid catalyst A15-CdS was demonstrated by the constant photodegradation efficiency and negligible CdS loss during five-cycle runs. The results indicated that nano-CdS immobilization within A15 would greatly improve the applicability of CdS nanoparticles in practical environmental remediation.

A novel hybrid adsorbent HMO-001 was fabricated by impregnating nanosized hydrous manganese dioxide (HMO) onto a porous polystyrene cation exchanger resin (D-001) for enhanced removal of Cd(II) and Zn(II) ions from waters. The immobilized sulfonate anions covalently bound to the D-001 polymeric matrix are supposed to result in preconcentration and enhanced permeation of both target metal ions for favorable adsorption by HMO. Batch and column adsorption runs demonstrated that HMO-001 exhibited highly preferable Cd(II) and Zn(II) retention from waters in the presence of competing Ca(II) ions at much greater levels. The exhausted adsorbent particles are amenable to efficient regeneration by 2% HCl solution without any HMO loss during operation.

Titanium phosphate (TiP) exhibits preferable sorption toward lead ion in the presence of competing calcium ions at high levels, however, it is present as fine or ultrafine particles and cannot be directly employed in fixed-bed or any flow-through systems due to the excessive pressure drop and poor mechanical strength. In the present study a new hybrid sorbent TiP-001 was fabricated by impregnating titanium phosphate (TiP) nanoparticles onto a strongly acidic cation exchanger D-001 for enhanced lead removal from waters. D-001 was selected as a host material mainly because of the Donnan membrane effect resulting from the immobilized sulfonic acid groups bound on the exchanger matrix, which would enhance permeation of the target metal cation prior to effective sequestration. TiP-001 was characterized by transmission electron micrograph (TEM), X-ray diffraction (XRD), and pH-titration. Batch and column sorption onto TiP-001 was assayed to evaluate its performance as compared to the host exchanger D-001. Lead sorption onto TiP-001 is a pH-dependent process due to the ion-exchange nature, and its sorption kinetics follows the pseudo-second-order model well. Compared to D-001, TiP-001 displays highly selective lead sorption in the presence of competing calcium cations at concentration of several orders higher than the target metal. Fixed-bed sorption of a synthetic feeding solution indicates that lead retention by TiP-001 results in a conspicuous decrease of this toxic metal from 0.50 to below 0.010 mg/L (drinking water standard recommended by WHO). Moreover, its feasible regeneration by dilute HCl solution also favors TiP-001 to be a feasible sorbent for enhanced lead removal from water.A new hybrid sorbent TiP-001 was fabricated by impregnating titanium phosphate (TiP) nanoparticles onto a porous cation exchanger D-001 for enhanced lead removal from waters.

Aminated polystyrene resins (NDA-101 and NDA-103) were synthesized, and their adsorption performances for phenol in aqueous solution were investigated and compared with the commercial polystyrene resin (Amberlite XAD-4) and weakly basic polystyrene resin (Amberlite IRA-96). All the associated adsorption isotherms are well described by Freundlich and Langmuir equations. The results indicated that all the four resins spontaneously adsorb phenol driven mainly by enthalpy change, and their adsorption capacities, free energy changes, enthalpy changes, and entropy changes for phenol followed the same order as: NDA-101 > NDA-103 > XAD-4 > IRA-96. Surface energy heterogeneity analysis by Do's model also suggested that the surfaces of XAD-4 and IRA-96 were more homogeneous, and the better adsorption capacity and affinity of the aminated resins (NDA-101 and NDA-103) are probably due to their multiple hydrogen bonding and π–π stacking interactions with phenol molecule.