Electrochemical reduction of different Ag(i)-containing solutions in bioelectrochemical systems for recovery of silver and simultaneous power generation

Self-reduced MXene-Metal interaction electrochemiluminescence support with synergistic electrocatalytic and photothermal effects for the bimodal detection of ovarian cancer biomarkers

Novel two-dimensional MXene with unique optical and electrical properties has become a new focus in the field of sensing. In particular, their metallic conductivity, good biocompatibility and high anchoring ability to biomaterials make them attractive candidates. Despite such remarkable properties, there are certain limitations, such as low oxidative stability. MXene-Metal interactions are an effective strategy to maintain the long-term stability of MXene, while also improving the electrochemical activity and optical properties. Herein, a series of MXene/Ag nanocomposites including Ti3C2/Ag, Nb2C/Ag and V2C/Ag were designed based on the surface chemistry characteristics of MXene, where MXene served as the substrate for in-situ growth of silver nanoparticles via self-reduction of Ag(NH3)2+. The results showed that V2C MXene has the strongest self-reducing ability due to its multiple variable valence states, larger interlayer space and more reactive groups. Moreover, V2C/Ag exhibited unexpected oxygen reduction reaction catalytic activity and photothermal performance. In view of which, an electrochemiluminescence-photothermal (ECL-photothermal) immunosensor was developed using V2C/Ag as ECL anchor and photothermal reagent for ultrasensitive detection of Lipolysis stimulated lipoprotein receptor. This work not only provides a simple and effective synthesis method of MXene supported metal nanocomposites, but also provides more inspirations for exploring the efficient biosensing strategies.

Bioelectrochemical technology for recovery of silver from contaminated aqueous solution: a review

A large amount of silver-rich wastewater is generated from different industrial processes. This wastewater is not considered a waste, but a valuable source for recovery due to the precious silver (Ag). Previous studies have used traditional methods such as membrane filtration, electrolysis, chemical precipitation, electrochemical, and cementation for Ag recovery. However, many drawbacks have been reported for these techniques such as high cost, hazardous waste generation, and the needed refinement of recovered products. In this study, a bioelectrochemical system (BES) for Ag recovery from aqueous solution is introduced as an effective and innovative method, as compared with other techniques. Different types of Ag(I)-containing solutions that have been investigated in recent BES studies (e.g., Ag⁺ solution, [Ag(NH₃)₂]⁺, [Ag(S₂O₃)]^-, [Ag(S₂O₃)₂]^3- complexes) are reported. A BES is an anaerobic system consisting of anode and cathode chambers, which are normally separated by an ion-exchange membrane. The electron flow obtained from the anodic biological oxidation of organic matter is used directly for the cathodic electrochemical reduction of Ag(I) ions. The recovered product is Ag electrodeposits, formed at the cathode surface. Several studies have reported high Ag recovery efficiency by using a BES (i.e., > 90%), with high purity of metallic silver, and simultaneous electricity production. Furthermore, a BES can be employed for a wide range of initial Ag(I) concentrations (e.g., 50-3000 mg/L). The advantages of BES technology for Ag recovery are highlighted in this study for further practical applications.

Flow-Through PolyHIPE Silver-Based Catalytic Reactor

Catalytic reactors performing continuously are an important step towards more efficient and controllable processes compared to the batch operation mode. For this purpose, homogenous high internal phase emulsion polymer materials with an immobilized silver catalyst were prepared and used as a continuous plug flow reactor. Porous material with epoxide groups was functionalized to bear aldehyde groups which were used to reduce silver ions using Tollens reagent. Investigation of various parameters revealed that the mass of deposited silver depends on the aldehyde concentration as well as the composition of Tollens reagent. Nanoparticles formed on the pore surface showed high crystallinity with a cuboctahedra crystal shape and highly uniform surface coverage. The example of the 4-nitrophenol catalytic reduction in a continuous process was studied and demonstrated to be dependent on the mass of deposited silver. Furthermore, productivity increased with the volumetric silver density and flow rate, and it was preserved during prolonged usage and storage.