M. I. Martín

Removal of copper ions from aqueous solutions by a steel-making by-product

A study is made of the use of a steel-making by-product (rolling mill scale) as a material for removing Cu(2+) ions from aqueous solutions. The influence of contact time, initial copper ion concentration and temperature on removal capability is considered. The removal of Cu(2+) ions from an aqueous solution involves two processes: on the one hand, the adsorption of Cu(2+) ions on the surface of mill scale due to the iron oxides present in the latter; and on the other hand, the cementation of Cu(2+) onto metallic iron contained in the mill scale. Rolling mill scale is seen to be an effective material for the removal of copper ions from aqueous solutions.

Synergism in gold–cyanide extraction with Primene JMT–Cyanex 925 mixed extractant system

Abstract The synergic extraction of gold (I) from cyanide solutions has been studied using a mixture of Primene JMT (primary amine=RNH 2 ) and Cyanex 925 (bis(2,4,4,trimethylpentylactyPhosphine oxide=R 3 PO) in xylene. The variables that could affect the extraction system were investigated: equilibration time, temperature, aqueous pH, extractant mixture concentration, metal concentration and organic phase diluent. The selectivity of the system with respect to the extraction of different metal–cyano complexes was also evaluated. The gold (I) extraction reaction is discussed on the basis of the experimental results and numerical treatment of the experimental data. The species formed in the organic phase have the probable stoichiometry H + Au(CN) 2 − RNH 2 (R 3 PO) n , n being 1 (log K ext =10.27 max 10.55) or 3 (log K ext =12.80±0.13). Stripping of gold from loaded organic solutions was also studied using low ionic strength alkaline solutions at different experimental conditions.

Facilitated Transport of Gold from Cyanide or Chloride Media by Cyanex 923

The commercially available extractant Cyanex 923 (phosphine oxides mixture) was studied to be applied in the carrier-facilitated transport of gold, from either cyanide or chloride aqueous media, across a polymer-immobilized liquid membrane (PILM). is transported from alkaline pH values. The presence of lithium salts (and the respective counter anion) in the media improves the transport, whereas the organic diluent seems not to influence the metal permeability. Water can be used effectively, as receiving phase, for the present system. In chloride media, the carrier is able to transport gold(III), increasing the permeability as the initial HCl concentration is increased (up to 5×10−1 M HCl). This permeability is dependent on the respective organic diluent, being the metal flux independent at higher initial gold concentrations but metal dependent at lower gold concentrations in the feed phase. Sodium thiocyanate solutions can be used effectively as receiving phase in this media. From the experimental data, the mass-transfer coefficient in the aqueous feed phase and the thickness of the aqueous boundary layer were calculated for both, cyanide and chloride, aqueous media.

Manufacture of Ceramic Bodies by Using a Mud Waste from the TiO2 Pigment Industry

The main objective of this paper is focused in the use of waste generated by the TiO2 pigment industry, ilmenite mud (MUD), on the production of ceramic bodies. These ceramic bodies were produced from mixtures of a commercial red stoneware mixture (RSM) with different concentrations of mud (3, 5, 7, 10, 30 and 50 wt%). The samples were sintered to simulate a fast-firing process. The sintering behaviour of the fired samples was evaluated according to ISO rules by linear shrinkage, water absorption and porosity measurements. Both green powder and fired samples were characterised by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC/TG), field emission scanning electron microscopy (FESEM) and bending strength measurements. Moreover, the activity concentrations of radionuclides were measured by high-resolution low-background gamma spectrometry, because this mud is a NORM (Naturally Occurring Radioactive Material) waste. Finally, the TCLP leaching test (Toxicity Characteristic Leaching Procedure, USEPA) was performed to assess the risks of use tiles from an environmental perspective. The results demonstrated that MUD can be successfully valorisated in the manufacture of red stoneware ceramic bodies with similar, or even better technological properties than commercial materials used currently.