Removal of pollutants from acid mine wastewater using metallurgical by-product slags

doi:10.1016/j.seppur.2004.01.003

Separation and Purification Technology

Volume 40, Issue 1, 15 November 2004, Pages 61-67

https://doi.org/10.1016/j.seppur.2004.01.003 Get rights and content

Abstract

The removal of pollutants from acid mine drainage using metallurgical by-product slags was studied in laboratory scale. Metallurgical by-product furnace slags were used as sorbents for metal ions and dispersed air column flotation was employed for the solid/liquid separation of the loaded slags. Batch sorption/pH/kinetic studies were conducted using simulated Cu and Pb bearing wastewater. The calcium glass type of slags had high surface area and porosity. Promising result was succeeded from the combined process of slag sorption/flotation on the treatment of an acid mine drainage from a South African gold mine.

Introduction

Various methods exist for the removal of toxic metal ions from aqueous solution, viz. ion exchange, reverse osmosis, precipitation and adsorption, among others. Adsorption is by far the most versatile and widely used process. Activated carbon has been the standard adsorbent for the reclamation of municipal and industrial wastewaters. Owing to the high-cost of activated carbon, production of its low-cost alternatives has been the focus of research in this area for years. These sorbents for the heavy metals sorption ranged from natural materials to industrial and agricultural by-products, such as fly ash, carbonaceous material, metal oxides, zeolites, moss, hydroxides, lignin, clays, biomass, peanut hulls, pyrite fines, goethite and coral sand.

Furnace slags as metallurgical by-products are being used as fillers or in the production of slag cement. It has been reported that granulated furnace slag can be converted into an effective adsorbent and used for the removal of dyes [1], [2] and metal ions [3], [4]. Alkaline-based slags as non-conventional sorbents for various heavy metal ions combine ion-exchange and sorption properties with an acid-neutralising ability. Acid mine water is an unavoidable by-product of the mining and mineral industry, especially as far as the oxidation of sulphide minerals is concerned. Acid mine waters typically contain high concentrations of dissolved heavy metals and sulphate and can have a high turbidity and pH values as low as 2. These conditions may prohibit discharge of untreated acid mine waters into public streams, as they have a detrimental effect on aquatic plant and fish life. Similarly, ground water pollution caused by the drainage of acid mine water is an equally serious problem. Traditionally, acid mine water is neutralised by treatment with lime, resulting in concomitant precipitation of iron, aluminium and other metal hydroxides. However, since the minimum solubilities for the different metals usually found in the polluted water occur at different pH values and the hydroxide precipitates are amphoteric in nature, maximum removal efficiency of mixed metals cannot be achieved at a single precipitation pH level. Conventional sorbents are not acceptable in such a mal-condition as acidic high-turbidity mine drainage. Slags can be used as low-cost adsorbents and neutralising agents and viable alternatives to the combination of much more expensive activated carbon or ion exchange resins and lime.

Slags exist often in a powdered form and are mainly applied as dispersions. Downstream of the reaction tank, a suitable solid/liquid separation is generally necessary. Flotation offers various advantages for the scope of separation, compared with other processes such as filtration, sedimentation or centrifugation [5] and constitutes a known method in effluent and water treatment [6], [7]. Combination of adsorption and subsequent flotation has proven to be an effective method for the removal of heavy metals from wastewater streams [8], [9], [10].

The present study involves an examination of the sorption capacities of two different slags for Cu and Pb removal from wastewater streams. Batch sorption/pH/kinetic studies were conducted in laboratory scale using simulated Cu and Pb bearing wastewater. Flotation of slags following ion sorption offers an effective way for solid/liquid separation. Also reported is the successful use of the novel technique in the treatment of an acid drainage from a gold mine.

Section snippets

Experimental work

Two furnace slags, viz. iron making slag and steel making slag, were obtained from Saldanha Steel South Africa in the form of powder with a mean particle size of 24.5 and 24.1 μm, respectively. The size distribution was: 100% and100 μm; 90% and 45 μm; 22% and 10 μm; and 1.2% and 1 μm for the iron slag, compared to 100% and 100 μm; 90% and 45 μm; 23% and 10 μm; and 1.5% and 1 μm for the steel slag. The chemical composition of the slags expressed as oxides in mass percentage is shown in Table 1. The XRD

Sorption equilibria

Two important physico–chemical aspects for the evaluation of the sorption process as a unit operation are the equilibria of sorption and the kinetics. Sorption equilibrium is established when the concentration of metal in a bulk solution is in dynamic balance with that of the interface. Fig. 1 shows typical sorption isotherms of Cu²⁺ and Pb²⁺ on the two slags, respectively. The slurry pH was maintained at 5.5 and the slag doses were 2 g/l.

As can be seen from Fig. 1, the iron slag had a much

Conclusions

The iron and steel making slags were appropriate sorbents for heavy metal removal from aqueous solutions. The slags combined ion-exchange and sorption properties with an acid-neutralising ability. The iron slag had a much higher sorption capacity for metals than the steel slag owing to its higher surface area, higher porosity and higher ion-exchange ability. Flotation following the slag sorption could effectively separate the slags, yielding very low solution turbidities. Advantages when

References (12)

C. Aldrich et al.
Minerals Eng.
(2000)
J. Rubio et al.
Minerals Eng.
(1997)
A.I. Zouboulis et al.
Water Res.
(1995)
K.K. Panday et al.
Water Res.
(1985)
S.V. Dimitrova et al.
Water Res.
(1998)
V.K. Gupta et al.
Ind. Eng. Chem. Res.
(1997)

There are more references available in the full text version of this article.

Cited by (157)

Recent advances in the adsorptive removal of heavy metals from acid mine drainage by conventional and novel materials: A review
2024, Bioresource Technology Reports
Coal mining activities have widespread and detrimental effects on the environment and human health, primarily attributable to the generation of acid mine drainage (AMD). AMD is characterized by its low pH and high heavy metal content, posing significant risks to ecosystems and human populations alike. Extensive research has focused on the adsorption-based removal of heavy metals from AMD, involving the development of both conventional and innovative materials aimed at addressing this challenge. However, the practical application of these materials faces obstacles such as limited availability, complex preparation processes, and sensitivity to pH conditions. Effectively addressing this issue requires the identification of cost-effective and abundant materials that demonstrate consistent efficacy across diverse environmental conditions. Additionally, considering the potential for reusability and integration within a circular economy framework is crucial. This study offers a comprehensive overview of the current research landscape pertaining to heavy metal removal from AMD through adsorption. It includes a systematic categorization of heavy metals, an examination of their environmental and human health impacts, a comparative analysis of the performance of conventional and novel materials, an exploration of the influence of material preparation techniques and solution pH, and an assessment of the potential for reusability and circular economy integration. By consolidating and analyzing existing knowledge, this study provides valuable insights and serves as a valuable resource for researchers engaged in heavy metal removal from AMD. Moreover, it addresses significant knowledge gaps in this field, contributing to the advancement of sustainable solutions for AMD mitigation and environmental protection.
Spatiotemporal variations of river water turbidity in responding to rainstorm-streamflow processes and farming activities in a mountainous catchment, Lai Chi Wo, Hong Kong, China
2023, Science of the Total Environment
Citation Excerpt :
For example, Clark et al. (2017a, 2017b) used turbidity sensors paired with river suspended sediment collections during an intense rainfall event to determine continual suspended sediment fluxes, and then disclosed that the relationship between SSC and turbidity was better than the relationship between SSC and river discharge in the case of a river in Puerto Rico. Additionally, river turbidity is one of the main sources in causing poor water quality (Hounslow, 1995; Wanielista et al., 1997; Feng et al., 2004; Azrague et al., 2005; Michalak, 2016; Liu et al., 2017), and has significant impacts on farmland irrigation (Declerck et al., 2006; Eder et al., 2010) and river ecology (Cole et al., 1992; Johnson et al., 1995). Insufficient light for photosynthesis of river plants, which is reduced by high turbidity, can limit food production, and may harm aquatic organisms (Lunt and Smee, 2014).
River turbidity is an important factor in evaluating environmental water quality, and turbidity dynamics can reflect water sediment changes. During rainfall periods, specifically in mountainous areas, river turbidity varies dramatically, and knowledge of spatiotemporal turbidity variations in association with rainfall features and farming activities is valuable for soil erosion prevention and catchment management. However, due to the difficulties in collecting reliable field turbidity data during rainstorms at a fine temporal scale, our understanding of the features of turbidity variations in mountainous rivers is still vague. This study conducted field measurements of hydrological and environmental variables in a mountainous river, the Lai Chi Wo river, in Hong Kong, China. The study results revealed that variations of turbidity graphs during rainstorms closely match variations of streamflow hydrographs, and the occurrence of the turbidity peaks and water level peaks are almost at the same time. Moreover, the study disclosed that the increasing rates of the turbidity values are closely related to the rainfall intensity at temporal scales of 15 and 20 min, and the impact of farming activities on river turbidity changes is largely dependent on rainfall intensity. In the study area, when the rainfall intensity is larger than 35 mm/hr at a time interval of 15 min, the surface runoff over the farmland would result in higher river water turbidity downstream than that upstream. The study results would enrich our understanding of river water turbidity dynamics at minute scales and be valuable for further exploration of the river water environment in association with turbidity.
Biobased materials in removing heavy metals from water
2023, Advanced Applications of Biobased Materials: Food, Biomedical, and Environmental Applications
Heavy metal contamination is a severe threat and a growing concern for the global community. Inadequate wastewater treatment without proper management and growing industrialization leads further toxic heavy metal contamination to water sources. Standard techniques such as electrocoagulation and membrane filtration with commercial products are not feasible. As a result, numerous studies and research were carried out to identify green biomaterials to evaluate their potential to ameliorate toxic heavy metals and pollutants. This book chapter carried out a comprehensive study on biomaterial sources and their potential to remediate toxic heavy metals. In addition, the summary of various biomaterials utilized in heavy metal remediation also provides an insight into various influencing factors which affect the removal efficacy.
Occurrence of steel converter slag and its high value-added conversion for environmental restoration in China: A review
2022, Journal of Cleaner Production
As the main co-product during the iron and steelmaking process, steel converter slag has been mainly landfilled and/or utilized as concrete aggregates for road construction in China. However, such a vast amount of steel slag emission, no more than 30% efficient use of steel slag in China, would undoubtedly cause serious environmental problems. Moreover, large amounts of CO₂ could be emitted during the whole steelmaking process, accounting for approximately 15% of the total CO₂ emission in China. This review first summarizes the classification, production, and utilization of iron-and steel-making slag. Then, methods to the comprehensive utilizing are examined in aspects of main characteristics, pre-treatment methods, primary utilization and high value-added conversion of steel converter slag for environmental protection in China. The critical constraints that impede the exploitation of steel converter slag are objectively discussed in light of the reinforcement for the recycling of these by-products. Thus, a systematic database on the characteristics and uses of steel slags should be also established for better utilization. Moreover, aiming for China's 2060 carbon neutrality objective for tackling global climate change, the possible conversion of converter slags close to CO₂ generating source to photocatalyst (such as heteroatom doped hydroxyapatite) is proposed, up recycling a part of solid waste. Based on this, a proposal of comprehensive and circular system converting converter slag into photocatalyst for CO₂ reduction and H₂ production is crucial for realizing environmental and economic synergies and sustainability for future generations.
Evaluation of hydrazine, dimethylamine borane and glyoxylic acid as reducing agents in reductive precipitation.
2022, South African Journal of Chemical Engineering
The mechanisms of heavy metal removal (Fe, Al and Mn) from acidic mineral effluents (pH <3) by reductive precipitation using basic oxygen furnace slag (BOFS) as a seeding agent was studied. The mechanisms of removal were determined using spectroscopic techniques (FTIR, XRD and XRF) to study the microstructural and composition changes of the seeding material. It was established that the sorption process occurred predominantly by chemisorption for trivalent cations i.e. Al³⁺ and Fe³⁺, while for divalent cations i.e. Mn²⁺ removal occurred through ion exchange and chemisorption. Furthermore, the results showed that the incorporation of metal ions in the BOFS structure caused chemical changes in the FTIR spectra. The results showed that the removal of metal ions from effluents using hydrazine as a reducing agent was thermodynamically feasible with the following removals: 99.9% for Fe (III) and Mn (II), 99% Al (III) using synthetic solutions. The% removals of Fe (III) and Mn (II), Al (III) using DMAB as a reducing agent were not significantly different from those obtained using hydrazine. Metal removal using glyoxylic acid as a reducing agent was not thermodynamically feasible; hence the% metal removals were the lowest i.e. Al (85%), Fe (97.5%) and Mn (94%) compared to hydrazine and DMAB.
Steel slag as a cost-effective adsorbent for synergic removal of collectors, Cu(II) and Pb(II) ions from flotation wastewaters
2022, Minerals Engineering
Flotation reagents and heavy metal ions always coexist in mineral flotation wastewaters, arousing serious environmental issues or having deleterious effects on mineral flotation. In this work, the steel slag was adopted as a cost-effective adsorbent to synergically remove butyl xanthate (BX), diethyl dithiocarbamate (DDTC), Cu(II) and Pb(II) ions. At the steel slag dosage of 12.0 g/L, Cu(II) and Pb(II) concentrations decreased from 4.0 mg/L to below 10.0 μg/L, and the removal of COD reached 54.33%. The removal efficiency of COD increased from 11.36% to 57.49% as Cu(II) and Pb(II) concentrations rose from 0 to 8.0 mg/L, revealing the promotion effects of metallic ions on collector adsorption. The maximum uptake capacity of steel slag reached 110.45 and 160.48 mg/g for Cu(II) and Pb(II), respectively. The collector adsorption capacity of steel slag increased nearly two magnitudes after modifying with the uptake of Cu(II) or Pb(II) ions. The SEM/EDS, XPS and FTIR analysis indicated that steel slag could be in-situ modified to generate copper or lead hydroxides and oxides during the removal of Cu(II) and Pb(II) ions. Subsequently, these precipitates acted as reactive sites for chelating BX and DDTC to form indissolvable metal-collector chelates. Owing to in-situ modification of steel slag by uptaking metallic ions, the adsorption was potentially feasible for treating flotation wastewaters.

View all citing articles on Scopus

View full text

Removal of pollutants from acid mine wastewater using metallurgical by-product slags

Abstract

Introduction

Section snippets

Experimental work

Sorption equilibria

Conclusions

Minerals Eng.

Minerals Eng.

Water Res.

Water Res.

Water Res.

Ind. Eng. Chem. Res.