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Hydrogels, as a new type of biomaterial with unique physical and chemical characteristics, have three-dimensional solid networks constructed by hydrophilic polymer chains. The superior swell-abilit...

Selective recovery of Pb2+ is always a high concern in the industrial application but challenging. Recycling Pb2+ as a sort of resource from contaminated water not only can significantly cut down the resource depletion but also reduce environmental pollution. Herein, a feasible electrochemistry-driven adsorption approach (ECDA) is employed to aid adsorbents for the selective removal of Pb2+ from metal-laden wastewaters. The distribution coefficient (Kd) of Pb2+ on the conductive tannic acid-graphene aerogel (TA@GO) is 370.53 mL g−1 at −0.2 V which is 3 times that of the corresponding adsorbent (118.80 mL g−1) without applying a weak electric field. Compared with pure adsorbent, TA@GO achieves an enhanced selectivity coefficient (α) from 1.39 to 4.18 for Pb2+/Cu2+ at −0.2 V. The weak electric field can drive Pb2+ ions migrates rapidly from the bulk solution to the surrounding binding sites (phenolic hydroxyl) of adsorbent forming pre-aggregation, increasing the accessibility and availability of the active sites with target pollutants. And then a strong coordination interaction occurs between Pb2+ and the binding sites on TA. By applying different potentials, the selective properties of TA@GO can be tuned. Moreover, TA@GO shows a high selectivity coefficient of 12.44 for Pb2+/Cu2+ after being improving the electrical conductivity using electro-reduction, which is up to 2.5 times higher than the original TA@GO. We elucidated a new Pb2+ removal mechanism that involves a synergic effect by anchoring additional electric fields on functional adsorbents to improve the selective performance. This study highlights a novel direction for selective Pb2+ recovery by introducing electric fields onto adsorbents in practical application.

In this work, N-tetradecyl-isopropanolamine (NTIA) is synthesized and used as a new collector on the flotation separation process of scheelite from calcite to further improve the efficiency of the selective flotation. The effects of NTIA on minerals are investigated through microflotation experiments. Flotation experimental results show that NTIA provides good flotation and separation effects on the scheelite in a wide range of pulp pH (6.0–10.0). At pH 7.0, the flotation recovery of scheelite reaches 96.89%, while calcite to only 10%. Moreover, it also reveals an efficient separation effect for artificial mixed minerals of scheelite and calcite under certain conditions. The adsorption behavior of NTIA on scheelite is further studied using wettability test, infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and zeta potential analysis. The results demonstrate that the surface of scheelite is preferentially modified, increasing its hydrophobicity after treatment with NTIA. Meanwhile, under the action of hydrogen bonding and strong electrostatic field in the hydrophilic N–H group of NTIA, the NTIA molecules are absorbed on the scheelite surface.

Selective extraction of target metal ions from contaminated water is always the concern in the absorbent application. Herein, a palladium ion-imprinted polymer (Pd-IIP-AHTB) absorbent was designed and fabricated through radical-induced polymerization of Schiff based functional monomer (3-Allyl-2-hydroxybenzaldehyde thiosemicarbazone, AHTB) to selectively recover Pd2+ from water. Pd-IIP-AHTB shows a high distribution coefficient Kd (850.46 mL g−1) which is up to 110 times higher than that of interference metal ion like Zn(II). pH 3.0 was chosen as an optimum pH in the adsorption operation. The maximum adsorption capacity on Pd-IIP-AHTB is 60 mg/g, which is 2 times that of the non-imprinted polymer (NIP) (30.33 mg/g) at 25 °C. Dubinin-Ashtakhov (DA) based site energy distribution model (F(E*)) confirms that more accessible sites are binding with Pd2+ on Pd-IIP-AHTB than NIP (Q0(F(E*)Pd-IIP-AHTB > Q0(F(E*)NIP, and E0*Pd-IIP-AHTB > E0*NIP). We elucidated a new Pd2+ adsorption mechanism that involves a strong coordination interaction between Pd2+ and binding site (X-> C N and Y-> C S) in a 3-D Pd-IIP-AHTB with memory effect cavity. Notably, the strong coordination enables the specific spatial transfer PdCl42− to [X-Pd-Y] in aqueous solution by fixed bed adsorption experiments verification, and no Cl− ions are retained on the absorbent. This finding provides new insight into the recovery of highly purified Pd on fixed bed packed Pd-IIP-AHTB absorbents and renewal hydrochloric acid solution in practical application.

Bioelectrochemical systems (BESs) exhibit great potential for simultaneous wastewater treatment and energy recovery. However, the efficiency of microbial electrocatalysis is fundamentally limited by the high resistance and poor biocompatibility of electrode materials. Herein, we construct a novel “binder-free” 3D biocompatible bioelectrode consists of 1D aminated carbon nanotubes (CNTs-NH2) and 2D conductive reduced graphene oxide (rGO) nanosheets through one-step electrodeposition. As expected, the maximum current density reached to 3.25 ± 0.03 mA cm−2 with the rGO@CNTs-NH2 electrode, which is 4.33-fold higher than that of a bare rGO (0.75 ± 0.01 mA cm−2), and is among the best performance reported for three-dimensional electrodes. The high microbial electrocatalytic activity is mainly attributed to the excellent performance of electron transfer and bacterial colonization, which originates from the 3D interconnecting scaffold, fast 1D CNTs “e-bridge” and positively charged surface.