Pressure Leaching of Chalcopyrite Concentrate: Ultra-Fine Milling as Process Acceleration Method

Ural enrichment plants processing copper-porphyry deposits are produced chalcopyrite concentrates of the following chemical composition, %: 21.5 Cu, 0.1 Zn, 26.59 S, 24.52 Fe, 0.05 Pb, 0.04 Ni, 16.28 SiO2 [1]. According to previous studies [2, 3, 21], such concentrates can be effectively treated using pressure oxidative leaching (POX). At temperature of 190–200 °C, partial oxygen pressure 4–6 bar and [H2SO4] = 15–30 g / L during 100-120 min about 98 % Cu was extracted. In this paper, an inluence of chalcopyrite concentrate preliminary grinding on efficiency of the POX stage was studied. It was found that even the finest grinding of the particle size class P80 = 13 μm does not lead to significant intensification of process kinetics.

Fine Comminution of Pine Bark: How Does Mechanical Loading Influence Particles Properties and Milling Efficiency?

The use of lignocellulosic plant biomass as an alternative to fossil feedstocks for chemistry, energy and materials often involves an intense dry comminution step, for which the energy consumed can vary significantly according to the process parameters, the particle size targeted, and the properties of the biomass. Here we studied the fine milling of maritime pine bark in an impact-mill configuration and in an attrition-mill configuration. The properties of the resulting powders (particle size distribution, particle shape, specific surface area, agglomeration level) obtained in each configuration were compared in relation to process energy consumption. Results evidenced that the agglomeration phenomena drive milling efficiency and limit the possibilities for reaching ultrafine particles. Interestingly, impact loading proved more effective at breaking down coarse particles but tended to generate high agglomeration levels, whereas attrition milling led to less agglomeration and thus to finer particles.

Novel Two-Stage Fine Milling Enables High-Throughput Determination of Glyphosate Residues in Raw Agricultural Commodities

Dramatic process-efficiency gains for residue analysis of glyphosate in raw agricultural commodities (RACs) were achieved by development and validation of a two-stage fine-milling process. This secondary milling produced a uniform and consistent product that could be reproducibly measured with 75 mg analytical test portions. The milligram scale sample size enabled the direct weighing of sample into a liquid-handler-compatible 96-well format. A high-throughput workflow based on this innovative comminution approach for the quantitation of glyphosate, a nonselective herbicide, and its main degradation product, aminomethylphosphonic acid, was validated in various RACs and used to demonstrate the applicability of the two-step milling process. The precision and reproducibility of 75 mg analytical portions taken through this assay was used to demonstrate the feasibility of using a two-stage fine-milling technique for pesticide residue applications. An RSD of less than 10% was achieved in endogenous glyphosate residues in multiple RACs. Comparable recoveries and superior precision were achieved with this new method as compared with a validated 10 g scale method.