Strategy for instant neutralisation and metal immobilisation in ARD

Abstract For ARD filters, reactive barriers are often the methods of choice. Some problems are recognised though; iron precipitation cause hydraulic changes and inhibition of neutralising phases. Instead of filter/barrier installation alkalinity is suggested to be added in an aqueous phase (leach beds). Addition of a highly alkaline solution to different ARD results in a rapid, almost instant neutralisation, precipitation of metals (Fe, Al) as well as almost quantitative coprecipitation and sorption of trace metals at near neutral pH. Generation of alkalinity on-site, added to ARD as an aqueous phase, would be a fast and simple ARD treatment method

Permanent under water storing of weathered mine waste after removal of fine fraction and addition of ash

Weathered sulphidic mine waste is a major environmental problem. An experiment was performed in order to study water covers for oxidized mine waste. In two experiments oxidized mine waste were covered with water, in one experiment the fine fraction was removed and in one experiment alkaline ash was also added prior to water covering. It was found that removal of the fine fraction decreased pH and increased trace element concentrations. Water covering of the mine waste with and without ash decreased trace element concentrations indicating that co disposing oxidized sulphidic mine waste and ash under water might be a promising remediation method

Fly ash injection into weathered mine waste

By adding alkaline ashes through injection to weathered mine waste pH increased approximately 3 units, trace element was immobilized and flow rate decreased due to formation of hard pans. Reduction in trace element concentrations was around 96.9-99.6 % for copper, 94.7-99.7 % for zinc and 22.9-99.8 % for cadmium. For lead the best reduction was 97.3 % and the worst -393 % (increase). MSWI ashes performed worst with low buffering capacity and increase in vanadium and molybdenum concentrations

Development of a low-tech treatment for neutral mine water : a case study

Lovisagruvan is a Pb-Zn-Ag mine in mid-south Sweden, with a yearly production of some 40 000 tons. There are four main levels in the mine: 55, 105, 145 and 190 m below ground. Water is continously pumped at a rate of 5 m3/h, passing sedimentation pools at each of the four main levels in the mine and finally one above ground. A modified backfill mining is used and in order to visually separate the ore from the waste rock limestone is used as a separating layer. Limestone addition in combination with non-acid producing mineralisation generates a pH-neutral mine water. For many years the mine has had problems with high levels of zinc and lead in the mine water released to recipient. The primary contaminants, lead and zinc, were mainly found as particles or associated to particles. With a combination of several measures including a sandfilter and FeSO4 addition suspended matter was reduced 93 %, lead 91 % and zinc 71 %

Impact of temperature on weathering rates : a long term kinetic study on waste rock from Bergslagen, Sweden

To assess the impact of different climatic conditions four weathering systems with waste rock from Bergslagen, Sweden, were followed. Secondary weathering products (ferrous and ferric sulphates and (oxy)hydroxides) on pyrite surfaces can slow down oxidation rates. It was investigated if repeated freezing/thawing could have an effect on the stability of the secondary product layer. After 90 weeks of weathering, freezing/thawing had not enhanced weathering rates, not even in combination with warm, humid air. Highest weathering rates were unexpectedly found in a reference system constantly kept at room temperature, and not in the more forceful humidity cell system

Remediation of Historic Waste Rock by Injection of Green Liquor Dregs : Results From a Field Scale Trial, Gladhammar, Southern Sweden

Mining in Gladhammar, southern Sweden started in the 15th century, generating waste rock containing copper, cobalt, and arsenic. During remediation (2011) some waste rock was preserved, due to its geoscienti- c value, and placed on a geomembrane surface. Eventually, it became apparent that it had a substantial environmental impact (pH 3.8, Cu 96 mg/L, Co 21 mg/L). In 2017, green liquor dregs was injected in order to increase pH and decrease trace element mobility. Ten months a er injection pH was 8.3 and concentrations of copper and cobalt 1.3 mg/L and 1.1 mg/L, respectively. Evaluation will continue for at least five years

Treatment of Historical Mining Waste using different Incineration Ashes

ARD from historical mining sites in Sweden is a major source for trace elements to surface waters. In order to be able to treat a large portion of these sites cost effective reclamation methods is necessary. Incineration ashes were used in leaching tests to study their effect on a highly weathered mining waste in order to neutralize acidity and immobilize trace elements. This study shows that ashes can be used to increase pH and decrease trace element mobility from oxidized mining waste. Increased leaching of Cl, Mo and Sb, however, needs to be considered for waste fuel ashes before use

Alkaline by-products as amendments for stabilization and neutralization of oxidized sulphidic mine waste deposits

Stabilization of oxidized sulphidic mine waste deposits with alkaline by-products could be a way of controlling ARD. Mixtures of alkaline by-products (10% by volume) and oxidized waste rock have been studied during six months in 30 L experimental drums. Alkaline by-products are: lime mud (LM), green liquor dreg (GLD), lime kiln dust (LKD), LD slag (LD), water work granules (WWG), carbonized fly ash (FAE) and fresh fly ash (FAF). The experiments are fed with water once a week to imitate natural precipitation. pH of the reference (no alkaline amendment) is below 3 and trace metal concentrations are 2000 mg/l, 4 mg/l and 1 mg/l for Zn, Cd and Pb respectively. LKD, LM and LD amended systems (pH 6.7-7.5) are the most efficient for Cd- and Zn-removal (reduction at least 99 % compared to the reference), while GLD (tap pH 6.5) is the most efficient for Pb-removal (99 % reduction compared to the reference). FAE amended system only reaches pH around 5 and accordingly trace metal reduction is rather low. Geochemical simulations using PHREEQC indicate equilibrium with otavite and smithsonite in the WWG and GLD systems, whereas cerrusite is at equilibrium in the LKD, WWG and GLD systems.Non UBCUnreviewedUnknow

Mining Waste as an Exploration Tool and Secondary Resource

There is today no overall information about how much mining waste there is in Sweden and what it contains. This project focused on samples from waste rock, tailings and slag from the historical mining region Bergslagen, Sweden. Modern dissolution and analytical methods were used in order to determine approximately 50 elements in the samples. Modern analytical data for the historical mining waste is useful as an exploration tool and can provide information about remaining or new resources underground. Results show that there is a potential for recovery of critical elements from mining waste as well as dealing with environmental problems