Polyacrylic acid (PAA) hydrogel prepared by radical polymerization in a clean and extremely simple way was used to adsorb U(VI) ions from aqueous solutions. Fourier transform infrared spectroscopy (FTIR) characterization demonstrated that the PAA hydrogels were successfully synthesized, FTIR and transmission electron microscope (TEM) characterization illustrated the adsorption mechanism, and the adherence of the U(VI) ions on PAA was confirmed by X-ray photoelectron spectroscopy (XPS) energy dispersive X-ray (EDX). Batch experiments with various pH, initial concentration and contact time were conducted to evaluate the adsorption performance. The adsorption kinetics of the PAA hydrogels followed a pseudo-second-order model and exhibited a 3-stage intraparticle diffusion mode. Equilibrium data were best described by a Langmuir model, and the estimated maximum adsorption capacity for the adsorbent was 445.11 mg g⁻¹. Moreover, the U(VI) loaded adsorbent could be regenerated using 0.1 M HNO₃ acid solution, and the regenerated adsorbent after five cycles could retain 90.91% of the adsorption capacity of the fresh adsorbent. The results suggested that the PAA hydrogels could be considered to be very effective and promising materials for U(VI) removal from waste water.

An economical and stabilized immobilized-enzyme method was developed for the removal of phenol in wastewater. Tyrosinase was immobilized on the PAN-based beads with glutaraldehyde as was confirmed successfully by a series of characterizations involving Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The biodegradation of phenol was investigated by using the immobilized beads and compared to free tyrosinase. The optimum pH and temperature were determined to be 7.0 and 40 °C, respectively. Experiments showed that the immobilized tyrosinase was much more stable than the free tyrosinase in storage and that the immobilized tyrosinase could even retain about 78% of its original activity after repeated use 6 times in a batch system. Furthermore, the comparative in vitro cytotoxicity of phenol/treated solutions were evaluated in LO2 and HepG2 cells by using the CCK-8 assay for cell viability along with flow cytometry detection for apoptosis. The results showed that the toxicity of the phenol solutions only exerted toxicity on cells in a certain concentration range (>0.5 mM for LO2 and HepG2 cells) and that the toxicity of the phenol solutions was greatly decreased after treatment with the tyrosinase-immobilized beads. Thereby, the results confirm that we have established a suitable strategy with promising application to remove phenol economically and efficiently, which could even lower the toxicity of phenol at the cellular level.

A clean and simple method has been developed for preparation of interpenetrating polymer networks using polyacrylic acid (PAA) and chitosan (CS) for extraction of uranium from polluted water. The peak of Fourier transform infrared spectroscopy (FTIR) occurred at 928 cm⁻¹ indicating combination of uranium and PAA/CS. The energy dispersive X-ray (EDX) and the scanning electron microscope (SEM) studies illustrated the formation of a crosslinking structure and excellent binding ability of uranium on PAA/CS. The maximum adsorption capacity was 289.6 mg g⁻¹ calculated using the equation of the Langmuir model. The adsorption capacity reached a plateau at pH 4 and the sorption process fits the pseudo-second-order model well. The PAA/CS composite has stability of reuse, with the adsorbent capacity decreasing slowly with increasing usage frequency. The experimental results confirm that the PAA/CS hydrogel could be a novel alternative for highly efficient removal of uranium from wastewater.