New Effective Technique to Eliminate Toxic Cadmium(II) from Wastewater

In a paper published in NANO, a group of researchers from Hebei University of Technology, Tianjin, China have discovered an effective way to remove heavy metal Cadmium(II) from wastewater. This utilizes the surface-initiated atom-transfer radical polymerization (SI-ATRP) method to graft poly (tert-butyl acrylate) PtBA from the ultrathin pore wall of inverse opal (IO) SiO₂.

Currently, harmful heavy metal pollution in water bodies is an extremely severe environmental issue and causes various serious diseases and even cancer due to carcinogenicity and damage of liver, kidney, and skin. Cadmium (Cd), a dangerous heavy metal, mainly originates from metal production, photography, electroplating, and the manufacturing of batteries.

Therefore, it is quite necessary and urgent to develop a series of ways to remove Cd(II) from wastewater. The research group led by Professor Zhang Xu of Hebei University of Technology used the prepared inverse opal hybrid SiO₂ for the removal of Cd (II) in aqueous solution.

The SI-ATRP method was utilized to graft polymer segments from the ultrathin pore wall of IO SiO₂. First, IO SiO₂ was prepared through a templating method. Then, bromine groups are anchored into the materials by sol-gel method. Afterward, the SI-ATRP method was utilized to graft poly (tert-butyl acrylate) (PtBA) from the pore wall of IO SiO₂ (IO SiO₂-g-PtBA). Subsequently, PtBA was hydrolyzed to polyacrylic acid (PAA) and the IO SiO₂-g-PAA was obtained.

Finally, an amidation reaction with superfluous diethylenetriamine (DETA) was performed to obtain IO hybrid adsorbent (IO SiO₂-g-PAA-DETA). Batch adsorption of removing Cd(II) onto IO SiO₂-g-PAA-DETA was studied as the effect of solution pH, adsorbent doses, contact time, ionic concentration, and temperature.

The IO hybrid adsorbent with the grafted amount of 73% showed the optimum adsorption capacity. The adsorption performance towards Cd(II) ions exhibited the best adsorption ability when the pH value is 5 and the adsorbent feed was 0.5 g/L.

In addition, Na+ at low concentration had little effect on adsorption capacity. The experimental data was best described using the Freundlich and the pseudo-first-order model. After regeneration by 0.025M EDTA solution, the adsorption efficiency was kept above 80% of the original Cd(II) adsorption ability in 6 adsorption-desorption experiments.

On the basis of the above summary, it can be summarized that the IO hybrid adsorbent is a well potential candidate for removing Cd(II) ions.

This work was supported by the National Natural Science Foundation of China (No. 51573038, 51403049, and 50903027) and the Natural Science Foundation of Hebei Province (No. E2016202261 and E2017202036).

Additional co-authors of the paper are Yanhong Wang, Xiuli Wang, Cuihong Wu. Corresponding author for this study are Xiaomei Wang, [email protected], Xu Zhang, [email protected].