Here we report that the Deep Eutectic Solvent (DES), (Ethylene glycol) 2 (Choline chloride), (2Eg:ChCl)is an effective medium in electrolytic removal of the Fe rich layer from Ni based Hot Isostatic Press (HIP) consolidation and that it is capable of sustaining etching at higher rates and at higher current efficiencies than a comparable aqueous electrolyte formulated from methane sulphonic acid / glycolic acid (MSA/GA). At high etch rates the surface finish is not as good using 2Eg:ChCl but high etch rates, current efficiency and excellent surface finish can be obtained from a 90%/10% hybrid mixture of 2Eg:ChCl MSA/GA electrolytes. In this study we have set out to compare the electropolishing and bulk electrolytic etching of HIP formed bodies fabricated from RR1000 Ni based superalloys in aqueous methane sulphonic acid / glycolic acid (MSA/GA) electrolyte and in Deep Eutectic Solvent (DES) type ionic liquids. Samples consisting of HIP formed test coupons were electropolished under a range of conditions of current density and applied potential in either the DES (2Eg:ChCl) or MSA/GA electrolytes. The samples were then characterised using a combination of methods including scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical microscopy. Surface roughness and etch characteristics of the samples were determined after treatment in each of the electrolytes in order to establish the comparative efficacy of the DES. Here we present details of some of the challenges and methodologies as well as characterisation of model test pieces and forms using the scale-up facilities at the Ionic Liquids Demonstrator (ILD) facility at the University of Leicester.We show that the HIP alloy can be effectively removed under mild conditions using DES electrolytes that are of low toxicity, environmentally sustainable, relatively low cost and without the use of strong acids or chemical etchants.
The chemical fate of wastes put into disposal wells can be determined using standard chemical engineering techniques. The concentration of hazardous constituents is typically reduced by reactions within the waste itself or by reactions with the injection zone material, thus reducing any potential impact on the environment. Such reactions include neutralization, hydrolysis, ion exchange, adsorption, precipitation, co‐precipitation and microbial degradation.
Extensive research was done to quantify these phenomena, so they could be used in a predictive model.
Neutralization, hydrolysis and precipitation were modeled using data from the open literature: reaction rates and equilibrium constants for the dominant reactions were incorporated into a sophisticated computer simulation that calculates solid‐liquid equilibria of aqueous electrolyte solutions.
The model predicted the fate of two waste streams: (1) high‐pH, cyanide‐containing waste injected into sandstone is made less hazardous by hydrolysis and sand dissolution, and (2) FeCl3‐FeCl2 HCl‐H2 O waste is made non‐hazardous by reaction with dolomite. Experiments are planned to confirm certain model predictions. Further development and public access of the model are planned.
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