Using non-hazardous industrial residues in mine waste remediation is beneficial not only for the mining industry where substantial amounts of the waste generated have potential to produce acid rock drainage and pollute the environment, but also the providing industry, minimizing the waste landfilled. In this study green liquor dregs (GLD), residue from 15 different paper mills were characterized to valorize it as a potential product as a cover material. In another part of the study, one of the GLDs and a local till were characterized to determine the optimal mixture of GLD amended till to be used in a field application at the closed Näsliden Mine in northern Sweden. The study concluded 10% GLD-amended till to be the optimal recipe and was successfully applied at the Näsliden mine waste dump. However, the great variability in the characteristics of GLD creates challenges if it is to be valorized as a product.

In Sweden, a dry cover solution is commonly used to stop sulfide oxidation and the production of acid rock drainage from unattended sulfidic mine waste. Recycling a non-hazardous industrial residue, such as green liquor dregs (GLD) generated during pulp production, in this cover solution is beneficial for both the mining industry where there is a great need for cover materials and the pulp production industry. The objectives of this field study were to install and evaluate the instrumentation of sealing layers made of GLD- and bentonite-amended till, and to evaluate the practical aspects of two different methods of installation: monitoring wells and pits. This practical field study demonstrated that it is difficult to properly seal the drill holes after installing the probes in observation wells and suggests that a better (easier and less costly) alternative for future instrument installation in a sealing layer might be to excavate a pit in the protective layer after installation of the soil cover and then drill the probes into the sealing layer from that pit.

The oxidation of sulfide minerals in mine wastes is a possible threat to the environment as it might have potential to generate acid rock drainage (ARD). A common method to reduce ARD is to apply a dry cover on the mine waste deposit. Considering the massive amounts of mine waste produced in Sweden (104-million-ton in year 2018) there is a great need for suitable dry cover materials. Using non-hazardous industrial residues in the dry cover would be beneficial for both the mining industry and the providing industry as stricter waste management legislation incentivizes them to develop their waste management strategies. The objective of this study was to investigate if an addition of Green Liquor Dregs (GLD), a residue from pulp production, can decrease the hydraulic conductivity and increase the water retention capacity (WRC) of three different tills, with the purpose of improving the performance of a dry cover material on a mine waste deposit. Another objective was to investigate how the hydraulic conductivity and WRC are affected by the contents of fines and clays in the tills. The study concludes that the water retention capacity of the tills improves with GLD addition, however, the hydraulic conductivity did not decrease enough to reach the in Sweden required < 10−8 m/s. Even though, GLD could still successfully be used in the reclamation of mine sites as the high WRC can be seen as the most important factor in deterring acid rock drainage by keeping the sealing layer close to saturation. This study further indicates that there are other factors than the particle size distribution of the materials that controls the hydraulic conductivity of the mixtures, such as initial water content, dry density, and compaction effort.

The mining industry produces massive amounts of waste that in contact with oxygen can result in leaching of metals. Access to a suitable cover-material for the mine waste is sometimes limited, creating a driving force for recycling industrial residues for these purposes. Green liquor dregs (GLD), an industrial residue from paper and pulp production, has the potential to be used in a sealing layer as an amendment to till. Though hydraulic conductivity is commonly used to evaluate the quality of the sealing layer, field application from laboratory investigations is challenging as many factors, apart from vast variations in the physical properties of both the till and the GLD, control hydraulic conductivity. In this study, 5–20 wt.% of GLD from two different paper mills, with different total solid contents and particle size distributions, were mixed with a silty till with varying total solid contents to investigate how the materials’ dry density, initial water content, and compaction affects the hydraulic conductivity. We found that the initial water content of the materials was the most important factor. With a drier till and GLD, more GLD should be added to attain the lowest hydraulic conductivity possible. The compaction was not found to notably affect the mixtures’ hydraulic conductivity.

La industria minera produce cantidades ingentes de residuos que, en contacto con el oxígeno, pueden dar lugar a la lixiviación de metales. El acceso a un material de recubrimiento adecuado para los residuos mineros es a veces limitado, lo que impulsa el reciclado de residuos industriales para estos fines. Los residuos de licor verde (GLD), un residuo industrial procedente de la producción de papel y pasta de papel, tiene el potencial de utilizarse en una capa de sellado como enmienda al laboreo. Aunque la conductividad hidráulica se utiliza habitualmente para evaluar la calidad de la capa de sellado, la aplicación sobre el terreno a partir de investigaciones de laboratorio es un desafío, ya que muchos factores incluyendo las grandes variaciones en las propiedades físicas tanto del suelo como del GLD, controlan la conductividad hidráulica. En este estudio, 5-20 % en peso de GLD de dos fábricas de papel diferentes, con diferentes contenidos totales de sólidos y distribuciones de tamaño de partículas, se mezclaron con un sedimento limoso con diferentes contenidos totales de sólidos para investigar cómo la densidad seca de los materiales, el contenido inicial de agua y la compactación afectan a la conductividad hidráulica. El contenido inicial de agua de los materiales resultó el factor más importante. Para un sedimento y un GLD más secos, debería añadirse más GLD para alcanzar la menor conductividad hidráulica posible. No se observó que la compactación afectara notablemente a la conductividad hidráulica de las mezclas.

采矿业产生的大量废弃物与氧气接触会导致金属的浸出, 很难获取合适的材料来对采矿废料进行覆盖密封处理, 进而促进了工业废料回收利用工作的进行. 绿液渣 (Green Liquor Dregs, GLD) 是纸浆生产过程中产生的工业废渣, 具有作为冰碛土改良剂来应用到密封层中的潜力. 渗透系数常用来评价密封层的密封程度, 但由于受许多因素控制影响, 要将实验室有关冰碛土和GLD研究的成果在现场应用并不容易, 其中就包含了两者物理性质在实验室和现场会产生巨大的差异. 本研究将来自两个不同造纸厂, 质量百分比在5~20%, 总固体含量和粒径分布不同的GLD, 与不同总固体含量的粉砂状的冰碛土混合, 研究材料的干密度, 初始含水量和压实度对渗透系数的影响. 研究发现渗透系数最重要的影响因素是初始含水量. 冰碛土和GLD混合物越干燥, 要达到尽可能低的渗透系数添加的GLD越多, 而压实度对混合物渗透系数影响并不明显.