Recovery of Silver from Wastewater Using a New Magnetic Photocatalytic Ion-Imprinted Polymer

A novel magnetic, photocatalytic, and Ag­(I)-imprinted thiol-functionalized polymer (Fe₃O₄@SiO₂@TiO₂-IIP) was prepared as functionalized IIP for selective removal and recycling of Ag⁺ ions from actual wastewater. The material used in this study exhibited a promising silver saturation adsorption capacity of 35.475 mg/g under the optimum pH of 6 within 80 min. The specific Ag⁺ ion adsorption property of the material was excellently offered by the Ag­(I)-imprinted thiol-functionalized polymer. The selectivity separation factors for Ag⁺ with respect to Li⁺, Co²⁺, Cu²⁺, and Ni²⁺ are 10.626, 27.829, 13.276, and 68.109, respectively. In the presence of TiO₂ and methanol used as the sacrificial agent (methanol/water 15:40), the adsorbed Ag­(I) can be reduced to Ag(0) and then separated from the imprinted polymers after the ultrasound. The reduction rate is 0.00566 min^–1 based on a pseudo-first-order kinetic model. The retained adsorption capacity of the Ag-IIP was 68.51% after one round of photocatalysis and ultrasound, which was closed to three rounds of acid elution. We also conducted an experiment with real wastewater and validated the great potential of Fe₃O₄@SiO₂@TiO₂-IIP in advanced wastewater treatment. The results showed that 1.3 mg of silver was recovered from 100 mL of 50 mg/L AgNO₃ solution with 0.1 g of the IIP. Accordingly, the functionalized IIP constructed and applied in this study demonstrated (a) the promising selective adsorption capacity of Ag, (b) the efficient photoreduction potential of Ag, (c) gentle and ecofriendly regeneration conditions, and (d) excellent magnetic separation ability, and it has great potential in future practical wastewater treatment

Molecular model combining the –POO^–– group of DNA with Ca²⁺ linked by an electrovalent bond.

<p>R₁, R₂, R₃, and R₄ represent the different bases in DNA, and the blue dashed line represents the electrovalent bond between Ca²⁺ and the –POO^–– group.</p

Relationships between Pb in corn grain and soil properties.

<p>Relationships between Pb in corn grain and soil properties.</p

Soil properties and BCF values for Cd in non-model wheat grain [61].

<p>Soil properties and BCF values for Cd in non-model wheat grain <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080855#pone.0080855-Jamali1" target="_blank">[61]</a>.</p

The Ca²⁺-influenced transformation efficiency of plasmid DNA exposed to phenanthrene (left) and pyrene (right).

<p>The transformation efficiency was calculated according to Equation I. Error bars represent 1 standard deviation (n = 3).</p

Soil Environmental Quality Standards of China (GB15618-1995) and the added contents of exogenous Pb (mg.kg⁻¹).

<p>Soil Environmental Quality Standards of China (GB15618-1995) and the added contents of exogenous Pb (mg.kg⁻¹).</p

Intra-species variability of BCF for Cd.

<p>The data from all non-model wheat species were normalized with the models listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080855#pone-0080855-t003" target="_blank">Table 3</a>.</p

Intra-species variability of Pb BCF.

<p>The data from all non-model corn species were normalized with the models listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085688#pone-0085688-t003" target="_blank">Table 3</a>.</p

Soil Environmental Quality Standards of China (GB15618–1995) and the content of exogenous Cd (mg.kg⁻¹).

<p>Soil Environmental Quality Standards of China (GB15618–1995) and the content of exogenous Cd (mg.kg⁻¹).</p

Intrinsic sensitivity (<i>k</i>) for non-model species fitted by models from Zhengdan 958.

<p>Intrinsic sensitivity (<i>k</i>) for non-model species fitted by models from Zhengdan 958.</p