Kirsi Yliniemi

The formation and characterisation of ultra-thin films containing Ag nanoparticles

A simple three step method for creating ultra-thin films, which contain Ag nanoparticles, on both glass and stainless steel surfaces, is presented. First, during the immersion into N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (DIAMO) a monolayer of DIAMO is attached on the sample surface after which immersion in silver nitrate is performed and a complex between the two amino groups of DIAMO and silver ions forms, leading to large clusters on the surface. During the annealing step these silver containing clusters are converted into silver nanoparticles which are homogeneously distributed and bound to the surface. The formation of the film was characterised using UV/Vis, FE-SEM and FE-AES. Additionally, SERS activity of the surface and the effect of the attachment of the nanoparticles on their antibacterial nature were also investigated.

Transpassive dissolution of Ni-Cr alloys in sulphate solutions: comparison between a model alloy and two industrial alloys

Abstract The application of a general model for the transpassive dissolution mechanism of binary Ni-based alloys to industrial alloys, Alloy 600 and Alloy C276, containing Ni, Cr, Fe and Mo, in 1 M sulphate solutions at pH 0 and 5 is described. A comparison of the electrochemical behaviour of these two alloys to a binary Ni–15%Cr alloy is also included. The techniques used were ring-disc voltammetry, impedance spectroscopy and resistance measurements. Soluble high-valency products were found to be released in a considerable amount from all the materials. The presence of Mo in Alloy C276 was found to increase the transpassive oxidation rate in comparison to alloys 600 and Ni–15%Cr at pH 0, but the same effect of Mo is not so well pronounced at pH 5. The mechanism of transpassive dissolution was found to be similar on every material at pH 0. At pH 5 the mechanism of the transpassive dissolution on Alloy C276 at high overpotentials is different from that at low overpotentials or from that at pH 0. This change is concluded to be due to the increased effect of adsorbed intermediates at the film/solution interface. The model was found to reproduce the steady state current and the impedance spectra satisfactorily.

Protein-assisted 2D assembly of gold nanoparticles on a polysaccharide surface

Site-specific assembly of gold nanoparticles on a polysaccharide surface was accomplished via a straightforward method exploiting interfacial polymer blends, selective protein adsorption and electrostatic interaction. The method could be useful in further applications due to the universal nature of the utilized phenomena.

QCM study of the adsorption of polyelectrolyte covered mesoporous TiO2 nanocontainers on SAM modified Au surfaces.

Mesoporous TiO(2) nanocontainers (NCs) covered with polyelectrolyte multilayers were adsorbed on self-assembled monolayer (SAM) modified gold substrates at different values of pH and ionic strength. The adsorption process was followed in situ by means of a quartz crystal microbalance (QCM) and the morphology of the adsorbate was investigated by means of FE-SEM images taken of the substrates after each adsorption process. Deposition could be achieved if either the particles and the surface had opposite charge, or if the salt concentration was sufficiently high, reducing the repulsion between the spheres and the surface. In the latter case the adsorption kinetics could be explained in the context of the DLVO-theory. Using conditions of like charges, one has a means to control the speed of deposition by means of ionic strength. However, interparticle aggregation and cluster deposition on the surface were observed at high ionic strength. Such conditions have to be avoided to obtain a uniform deposition of separated nanocontainers on the surface.

Dissolution Control of Mg by Cellulose Acetate−Polyelectrolyte Membranes

Cellulose acetate (CA)-based membranes are used for Mg dissolution control: the permeability of the membrane is adjusted by additions of the polyelectrolyte, poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). Spin-coated films were characterized with FT-IR, and once exposed to an aqueous solution the film distends and starts acting as a membrane which controls the flow of ions and H2 gas. Electrochemical measurements (linear sweep voltammograms, open-circuit potential, and polarization) show that by altering the CA:PDMAEMA ratio the dissolution rate of Mg can be controlled. Such a control over Mg dissolution is crucial if Mg is to be considered as a viable, temporary biomedical implant material. Furthermore, the accumulation of corrosion products between the membrane and the sample diminishes the undesirable effects of high local pH and H2 formation which takes place during the corrosion process.

Structural distinction due to deposition method in ultrathin films of cellulose nanofibres

This research explores fundamental, structural differences of ultrathin films, prepared with three distinct deposition methods using 2,2,6,6-tetramethyl-piperidin-1-oxyl radical oxidized cellulose nanofibres (TEMPO-CNFs) derived from never dried bleached birch pulp. There is standard characterization by atomic force microscopy (morphology, roughness) and ellipsometry (thickness) and important structural data is gained by exposing the films to water vapor and monitoring the vapor uptake with quartz crystal microbalance (QCM). Significant distinctions were found from QCM data that could be linked to the structure of the films, originating from the three deposition methods: adsorption, spin coating and electrophoretic deposition. Moreover, the results shown here have potential implications for various types of films that comprise of amphiphilic nanomaterials that have a distinct response to moisture or aqueous based solutions.

From metal-containing industrial waste towards circular economy of metals: European Training Network SOCRATES

It is becoming ever more clear that the natural resources – especially metals – are gradually being depleted from the Earth’s crust. Therefore, secondary sources such as industrial residues, waste and side-streams could potentially act as a more sustainable critical metal supply. This approach is at the very heart of the circular economy principles and, actually, fromthatpointofview, European countries have ‘inherited’ a large quantity of industrial waste (e.g. tailings, sludges, slags and ashes), i.e. a potential raw material ‘mines’ for metals, since the early days of industrialisation. With this motivation, the European Training Network for the sustainable, zero-waste valorisation of critical metal-containing industrial process residues ‘SOCRATES’ has been launched in January 2017 in the framework of the Marie SkłodowskaCurie Action (MSCA-ETN). The objective of the project is twofold: (1) to provide new scientific insights into recycling and sustainable processing of materials and (2) to train new experts of metal recycling and processing when 15 early-stage researchers (ESRs) pursue their doctoral degrees within the scope of the project (Figure 1). The outcomes of the SOCRATES project will offer comprehension to the process residues valorisation, with a focus on critical metals recovery, production of catalysts and inorganic polymers and integrated assessment of process sustainability. Whether we discuss catalyst production or metal recovery from sludges, it is obvious that electrochemistry, surface science and process engineering play critical roles and it can be seen also in the training of ESRs. SOCRATES brings together organisations from academia, industry and the research sector (Table 1) and, actually, the unique combination of SOCRATES partners spans through the entire metal supply chain. The universities within the SOCRATES consortium are among Europe’s leaders in extractive metallurgy research and transfer of knowledge to new generations of scientists is the main goal of this programme. Each of the four scientific work packages (WPs, Figure 2) of SOCRATES is dedicated to one step in the value chain – namely, metal extraction from industrial residues (WP1), metal recovery from process solutions (WP2), residual matrix valorisation into high value-added products (WP3) and integrated assessment of newly developed technologies (WP4). WP1 focuses on advanced metal extraction technology combinations, ranging from plasma-, hydroto solvometallurgical unit operations. The development of plasma-driven metal extraction methods has great potential to effectively separate metals that will lead to minimising costs, emissions mitigation, safer and cleaner byproducts. Solvo-metallurgy is based on organic solvents instead of aqueous solvents; here the surface chemistry and physics play a critical role in the organic– aqueous interface. With the development of new biocompatible solvo-metallurgical leaching methods, efficient recovery of targeted elements is envisaged. The development of deep eutectic solvents is a novel approach in extractive metallurgy, still industrially not widely applied. Searching for novel methods of metals removal from aqueous solutions is one of the priorities for WP2. Emerging interest for extraction of minor quantities of valuable metals from complex impure hydrometallurgical solutions is drawn to electrochemical methods as no additional chemical reagents are required and the recovery can be precisely controlled by applying favourable process conditions. The fundamental electrochemistry knowledge of very

A future application of pulse plating – silver recovery from hydrometallurgical bottom ash leachant

ABSTRACT In the current study, electrodeposition-redox replacement was applied to a hydrometallurgical solution with the main elements of Ca (13.8 g L−1), Al (4.7 g L−1), Cu (2.5 g L−1), Zn (1.2 g L−1), Fe (1.2 g L−1), S (1 g L−1), Mg (0.8 g L−1), P (0.5 g L−1) and Ag (3.5 ppm). The solution originated from the leaching experiment of incinerator plant bottom ash, which was dissolved into 2 M HCl media at T = 30 °C. The resulting deposit on the electrode surface was analysed with SEM-EDS and the observed Ag/(Cu + Zn) ratio (0.3) indicated remarkable enrichment of silver on the surface, when compared to the ratio of these elements (Ag/(Cu + Zn)) in the solution (6.8 × 10−5). The enrichment of Ag vs. (Cu + Zn) could be demonstrated to increase ca. 4500 fold compared to the ratio of the elements in solution.

Platinum recovery from Industrial Process Solutions by Electrodepo-sition-Redox Replacement

In the current study, platinum—present as a negligible component (below 1 ppb, the detection limit of the HR-ICP-MS at the dilutions used) in real industrial hydrometallurgical process solutions—was recovered by an electrodeposition–redox replacement (EDRR) method on pyrolyzed carbon (PyC) electrode, a method not earlier applied to metal recovery. The recovery parameters of the EDRR process were initially investigated using a synthetic nickel electrolyte solution ([Ni] = 60 g/L, [Ag] = 10 ppm, [Pt] = 20 ppm, [H2SO4] = 10 g/L), and the results demonstrated an extraordinary increase of 3 × 105 in the [Pt]/[Ni] on the electrode surface cf. synthetic solution. EDRR recovery of platinum on PyC was also tested with two real industrial process solutions that contained a complex multimetal solution matrix: Ni as the major component (>140 g/L) and very low contents of Pt, Pd, and Ag (i.e., <1 ppb, 117 and 4 ppb, respectively). The selectivity of Pt recovery by EDRR on the PyC electrode was found to be significant—nanoparticles deposited on the electrode surface comprised on average of 90 wt % platinum and a [Pt]/[Ni] enrichment ratio of 1011 compared to the industrial hydrometallurgical solution. Furthermore, other precious metallic elements like Pd and Ag could also be enriched on the PyC electrode surface using the same methodology. This paper demonstrates a remarkable advancement in the recovery of trace amounts of platinum from real industrial solutions that are not currently considered as a source of Pt metal.