Rubens Müller Kautzmann

Kinetics of goldcyanide extraction using ion-exchange resins containing piperazine functionality

Abstract The search for suitable resins for goldcyanide recovery from cyanide solutions prompted the synthesis of resins incorporating new functionalities that solve many of the existing problems. A new type of ion-exchange resin (PS-PIP) incorporating a piperazine group, linked onto a styrene–divinylbenzene macroporous network, was developed for goldcyanide solutions. Kinetics measurements were made on the extraction of goldcyanide (Au(CN) 2 − ) with the ion-exchange resin (PS-PIP). The extraction process is accompanied by fast ion-exchange reaction and is characterised by a sharp moving boundary between the reacted shell and the shrinking unreacted core within the resin. Analyses of the respective rate data in accordance with two theoretical models used to explain the metal extraction kinetics showed that the process is controlled by the rate of diffusion of the ions penetrating the reacted layer at goldcyanide concentrations in the range 10–40 mg l −1 and controlled by the rate of diffusion of the ions across the liquid film surrounding the resin particle at goldcyanide concentrations lower than −1 . Particle diffusion coefficients and mass transfer constants across the liquid film were determined from the graphical representation of the proposed models.

Ion exchange resins for gold cyanide extraction containing a piperazine functionality, 1. Synthesis and physico-chemical properties

The synthesis of two types of metal-chelating resins incorporating gold-specific piperazine groups is described. PS-PIP is a styrene-divinylbenzene macroporous network. MC-PIP is a (glycidyl methacrylate)-co-(ethylene dimethacrylate) network. The nominal functional group concentrations are 1.84 mmol/g for PS-PIP and 1.14 mmol/g for MC-PIP. The proton exchange capacity is 1.95 mmol/g for PS-PIP and 0.91 mmol/g for MC-PIP. Acuurate titration curves were used to determine pK, values (PK H = 7.05 ± 0.12). XPS analyses of PS-PIP resin were followed as a function of pH (cf. Fig. 8) demonstrating that the protonation of the amine is observable by a shift in binding energy of the N(1s) peak (±1.6 eV) moving from tertiary amine form (N(1s) 399.7 eV) to the protonated tertiary amine form (N(1s) 401.3 eV). Additionnally, the presence of quaternary ammonium groups was detected at a N(1s) peak at 402.3 eV (cf. Fig.9). Metal extraction from cyanide solutions, including Brazilian mine leach solution, showed considerable preference for gold (cf. Fig. 11-12). The piperazine resins extract gold via two mechanisms: (a) ligand substitution reactions at pH>7.05 (pK H(a) ) or (b) anion exchange reactions via the quaternary ammonium groups at high pH values. Extraction profiles were S-shaped (cf. Fig. 10) with 50% extraction ability at pH values. Extraction profiles were S-shaped (cf. Fig. 10) with 50% extraction ability at pH 8.0. Cyclic experiments involving extraction, elution, regeneration and recomplexation (cf. Tab. 6 and 7) showed the ability of MC-PIP to perform consistently at high extraction efficiencies from pH 8.6.

Ion Exchange Resins for Gold Cyanide Extraction Containing a Piperazine Functionality, 2. Study of the Gold Extraction Reaction

Ion exchange technology is offered as an alternative to activated carbon for gold cyanide recovery. A new type of ion-exchange resin (PS-PIP) incorporating a piperazine group, linked to a styrene-divinylbenzene macroporous network, is described. The extraction of Au(CN) - 2 and other metal cynadines with the PS-PIP resin involves three modes of metal extraction: the protonated secondary amine groups of the resin (at acidic pH conditions), the free amine groups of the resin (at neutral and basic pH values) and the small portion of the quatenary ammonium groups participate in the gold extraction mechanism. The gold cynadine extraction reaction on the polymeric piperazine was studied by a combination of metal extraction data, from batch experiments, and IR and XPS spectroscopic analysis of the metal loaded polymers. Extraction isotherms of gold cynadine show that gold binding is possible from 40-60 mg Au/g of resin in alkaline solutions, up to 150 mg Au/g of resin in acidic solutions. Efficient stripping of gold from the resin was achived using ethanol/water solutions of sodium hydroxide, or 0.5 mol/l thiourea in sulfuric acid solutions.

The use of fibrous ion exchangers in gold hydrometallurgy

This article examines a family of ion-exchange fibers, FIBAN, containing primary and secondary amine groups. These ion exchangers have a fiber diameter of 20–40 Μm, high osmotic and mechanic stability, a high rate of adsorption and regeneration, and excellent dynamic characteristics as filtering media. Inparticular, this article discusses the use of FIBAN fibrous ion exchangers in the recovery of gold cyanide andbase-metal cyanides (copper and mercury) from mineral-leaching solutions. The influence of polymer structure and water content on their extraction ability is described, along with key parameters of gold hydrometallurgy such as extraction efficiency, selectivity, pH dependence, gold cyanide loading, kinetics, and stripping.

Propagação de compostos da gasolina em solos: 1. zona não saturada

This work describes the study of the propagation of toluene in the unsaturated zone of the ground. It is shown the experimental procedure in laboratory columns. The gotten experimental results and their analysis with a mathematical modeling are shown. Also is shown an analysis statistics applied to the called the puffs models of the dispersion simulation and a quarrel of the continuation of this work.