Innovative and eco-friendly techniques of waste rocks management

在过去几十年中，世界各地露天采矿的发展对困难的经济环境以及一些战略金属和贵金属的高价格作出了相应的反应。这导致对许多高吨位/低品位类型矿床的兴趣增加，特别是在加拿大。这种采矿作业产生了巨大的足迹和大量的废石，通常储存在矿区的地表。一些地下矿山也面临着类似的问题。由于这些材料通常含硫化物，颗粒尺寸分布粗而宽（微米到公制尺寸），对水和氧的渗透性高，它们可能是或多或少污染的矿井排水的来源，有时产生高度酸。这种现象在世界范围内被称为酸性岩石排水（ARD）。硫化物反应导致排水水中酸溶性金属/类金属、硫酸盐和酸性物质的释放。废石堆的材料特性有利于氧在废石堆内的扩散。控制ARD的现有技术都是在废物处理期间（封顶、与尾矿共同处理、引水等）和/或在矿场关闭和复垦后处理时实施的，因此需要安装复杂但昂贵的覆盖技术，然后进行适当的植被恢复。******目前的项目旨在通过研究一种新的、创新的、环保的方法的不同步骤来解决围绕废石管理的挑战。这种方法必须在废石提取后立即应用于上游，集成了优化的废石爆破、后处理和/或增值。该项目的主要假设是：(i)废石中的硫化物主要与粗颗粒有关，并且没有明显暴露于风化条件下；（ii）矿物风化主要发生在细粒（尺寸有待进一步定义）中，因为这些颗粒的可用暴露表面积很大。***了解对更具创新性和可持续性的废石管理技术研究的重要需求，为研究计划确定的主要目标如下：***1-对废物提取和管理的爆破模式和适应性进行评估；***2-建议采用最适合废石的严格取样技术；***3-精细表征（物理、化学和矿物学性质）和基于自动化矿物学、显微层析成像等的新预测工具的实施；***4-优化高效除砂工艺，并通过重选和/或粗/细黄铁矿浮选对砂质部分进行脱硫；***5-集体方法的技术/经济可行性，包括粗粒重估的可行性（用于混凝土、道路路面等）

During the last decades, the development of open pit mining worldwide has responded accordingly to a difficult economic context as well as high prices for some strategic and precious metals. This has led to increased interest in many high tonnage/low-grade type deposits, particularly in Canada. Such mining operations generate large footprint and significant amount of waste rocks to be stored generally at the surface of mine site. Some underground mine are also facing similar problems. Since these materials are often sulphide bearing and have coarse and wide particle-size distributions (micrometric to metric sizes) as well as high permeability to water and oxygen, they are likely to be a source of more or less contaminated mine drainages, sometimes highly acid generating. The phenomenon is worldwide known as acid rock drainage (ARD). Sulfide reaction lead to the releases of acid-soluble metals/metalloids, sulfates, and acidity within the drainage waters. The oxygen diffusion within waste rock piles is favoured by the material properties. The available techniques to control ARD are all implemented during waste disposal (roof sealing, co-disposal with tailings, water diversion, etc.), and/or after disposal upon mine site closure and reclamation, thus necessitating the installation of complex but costly cover techniques followed by appropriate revegetalisation.******The present project aims to tackle challenges surrounding waste rocks management through the investigation of different steps of a new, innovative, and eco-friendly approach. This approach, which has to be applied upstream immediately after waste rock extraction, integrates optimized waste blasting, reprocessing, and/or valorisation. The main hypotheses of the project are that: (i) sulphides within waste rocks are mainly associated with coarse particles and are not significantly exposed to weathering conditions, and (ii) mineral weathering occurs primarily in the fine fraction (size to be further defined), due to the high available exposed surface area of these particles. ***Knowing the important needs of research for more innovative and sustainable waste rock management techniques, the main objectives defined for the research program are the following:***1- Evaluation of blasting pattern and adaptation for waste extraction and management;***2- Suggestion of a rigorous sampling technique which is optimal for waste rocks;***3- Fine characterization (physical, chemical and mineralogical properties) and implementation of new predictive tools based on automated mineralogy, microtomography, etc;***4- Optimization of an efficient desanding process and desulphurization of the sandy fraction through gravity separation and/or coarse/fine pyrite flotation;***5- Technical/economical feasibility of the collective approach, including feasibility of revalorization of the coarse fraction (for use in concrete, road pavement, etc.)