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Journal ArticleDOI

Acid mine drainage treatment by integrated submerged membrane distillation-sorption system.

01 Mar 2019-Chemosphere (Pergamon)-Vol. 218, pp 955-965

TL;DR: The results showed that modified (heat treated) zeolite achieved 26-30% higher removal of heavy metals compared to natural untreatedZeolite, and the integrated system produced high quality fresh water while concentrating sulfuric acid and valuable heavy metals (Cu, Zn and Ni).

AbstractAcid mine drainage (AMD), an acidic effluent characterized by high concentrations of sulfate and heavy metals, is an environmental and economic concern. The performance of an integrated submerged direct contact membrane distillation (DCMD) – zeolite sorption system for AMD treatment was evaluated. The results showed that modified (heat treated) zeolite achieved 26–30% higher removal of heavy metals compared to natural untreated zeolite. Heavy metal sorption by heat treated zeolite followed the order of Fe > Al > Zn > Cu > Ni and the data fitted well to Langmuir and pseudo second order kinetics model. Slight pH adjustment from 2 to 4 significantly increased Fe and Al removal rate (close to 100%) due to a combination of sorption and partial precipitation. An integrated system of submerged DCMD with zeolite for AMD treatment enabled to achieve 50% water recovery in 30 h. The integrated system provided a favourable condition for zeolite to be used in powder form with full contact time. Likewise, heavy metal removal from AMD by zeolite, specifically Fe and Al, mitigated membrane fouling on the surface of the hollow fiber submerged membrane. The integrated system produced high quality fresh water while concentrating sulfuric acid and valuable heavy metals (Cu, Zn and Ni).

Topics: Sorption (57%), Membrane fouling (53%), Membrane distillation (52%), Sulfuric acid (50%)

Summary (2 min read)

2.2.2 Heat treated zeolite

  • Heat treatment method was used to potentially enhance the performance of natural zeolite (Motsi et al., 2009; Turner et al., 2000) .
  • Heat treatment was chosen as it requires no additional chemicals and complex modification process.
  • Heat treatment was carried out by placing an appropriate amount of powder form natural zeolite in a ceramic dish.
  • The ceramic dish was then placed into preheated air atmosphere muffle furnace (Labec Laboratory Pty Ltd, NSW, Australia).

2.3.1 Surface area and pore width distribution

  • Nitrogen adsorption test was used to determine the Brunauer-Emmett-Teller (BET) specific surface area and the Barrett-Joyner-Halenda (BJH) pore width distribution of the natural and heat treated zeolite samples.
  • Nitrogen adsorption test was measured with a Micrometrics ASAP 2020 HD analyzer using low temperature, per the procedure of ISO 9277 and ISO 15901-2.

2.3.3 Surface morphology and element contents

  • A scanning electron microscopy (SEM) ((Zeiss Supra 55VP Field Emission) was used to analyse the zeolite surface characteristics (before and upon sorption).
  • The SEM was integrated with energy dispersive X-ray spectroscopy (EDX) (15kV accelerating voltage) in order to analyse the element contents in zeolite.

2.3.4 Influence of pH and surface charge

  • Zeolite surface charge was determined using zeta potential measurement.
  • For this purpose, zeolite (1 g/L) placed in beakers with 100ml AMD solution.
  • The pH of the initial solutions were varied from 1 -9.
  • Zetasizer (nano instrument ZS Zen3600, UK) was used to analyse the zeolite surface charge.

2.5.1 Membrane analysis

  • The morphology and element composition on the surface of the used and virgin membranes were analysed using SEM-EDX at a voltage of 15 kV as per the details mentioned in Section 2.3.3.
  • The hydrophobicity of the virgin and used membranes were evaluated by measuring the water contact angle of the membrane using a goniometer (Theta Lite, Biolin Scientific, Sweden).
  • Measurements were duplicated at different location of the membrane and the average value was used for this study.

3.1 Performance of natural and modified (heat treated) zeolite

  • The sorption capacity of natural and modified (heat treated) zeolite was tested for heavy metal removal from AMD.
  • Higher heavy metal removal was achieved with heat treated zeolite compared to natural untreated zeolite (Table 3 ).
  • Heating may have removed water on the surface as well as internal channels of the natural zeolite, resulting in vacant channels which enhances heavy metal sorption rate, as reported by previous studies (Ohgushi and Nagae, 2003; Turner et al., 2000) .
  • Heavy metal removal by zeolite minimally improved beyond 500 °C of heating.
  • This trend could be attributed to characteristics change of zeolite upon heat treatment.

3.2.1 Permeate flux and quality

  • Meanwhile, the concentration of permeate solution remained low (TDS less than 0.01 g/L).
  • The sulfate concentration in the permeate solution increased significantly from 0.13 mg/L to 50 mg/L.

3.2.2. Membrane analysis

  • Visible brown deposition (resembling iron oxides) was observed on the used membrane (Fig. 8b ) compared to the virgin membrane (Fig. 8a ).
  • SEM-EDX analysis revealed Fe, S and Al deposition on the membrane.
  • The precipitated metals predominantly deposited on the membrane surface and was loosely attached to the surface.
  • It is likely that the deposition only partially blocked the membrane pores, and therefore, a stable permeate flux was maintained throughout the operation duration.
  • Nevertheless, the contact angle of the used membrane (68.6 ± 0.8°) reduced by 38 -40% compared to the virgin membrane (109.5 ± 0.5°), suggesting that the Fe deposition resulted in the reduction of membrane hydrophobicity and partial wetting of sulfate ions.

3.3 Performance of integrated submerged DCMD-sorption

  • An integration of zeolite with submerged DCMD (Fig. 1 ) offers the potential for improving the performance of both processes in a single system.
  • The integrated system enable zeolite to be used in fine powder form with long contact time (more than 24 h) when kept suspended in a storage tank.
  • In return, the heavy metal removal by 500 °C heat treated zeolite (dose = 10.0 ± 0.2 g/L) at pH 4 will ensure minimal Fe and Al deposition onto the membrane during the submerged DCMD process.

3.3.1 Permeate flux and quality

  • The integrated submerged DCMD-sorption system showed similar flux pattern as the submerged DCMD (Fig. 7 ), indicating that the DCMD performance was not affected by the presence of sorbent in the storage tank.
  • The integrated system enabled to achieve high rejection of all ions, maintaining a permeate TDS of less than 0.01 g/L.
  • The sulfate concentration in the feed solution was increased from 4.2 g/L to around 8.2 g/L, while the sulfate concentration in the permeate solution remained low (less than 0.13-0.15 mg/L).

3.3.2. Membrane analysis

  •  A simple heat treatment was effective to increase the performance of natural zeolite for heavy metal removal from AMD solution.
  • Heat treatment of natural zeolite at 500 °C enhanced heavy metal removal by 26-30%.

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1
Acid mine drainage treatment by integrated submerged membrane 1
distillation sorption system 2
3
Seongchul Ryu
a
, Gayathri Naidu
a
, Md. Abu Hasan Johir
a
, Sanghyun Jeong
b
, Saravanamuthu 4
Vigneswaran
a,*
5
a
Faculty of Engineering, University of Technology Sydney (UTS), P.O. Box 123, Broadway NSW 2007, Australia
2
6
b
Graduate School of Water Resources, Sungkyunkwan University (SKKU), 2066, Seobu-ro, 7
Jangan-gu, Suwon-si, Gyeonggi-do 16419, Republic of Korea. 8
9
*Corresponding author: Tel +61-2-9514-2641; Fax +61-2-9514-2633; Email: Saravanamuth.Vigneswaran@uts.edu.au 10
11
12
Abstract 13
Acid mine drainage (AMD), an acidic effluent characterized by high concentrations of sulfate 14
and heavy metals, is an environmental and economic concern. The performance of an 15
integrated submerged direct contact membrane distillation (DCMD) zeolite sorption system 16
for AMD treatment was evaluated. The results showed that modified (heat treated) zeolite 17
achieved 26-30% higher removal of heavy metals compared to natural untreated zeolite. 18
Heavy metal sorption by heat treated zeolite followed the order of Fe>Al>Zn>Cu>Ni and the 19
data fitted well to Langmuir and pseudo second order kinetics model. Slight pH adjustment 20
from 2 to 4 significantly increased Fe and Al removal rate (close to 100%) due to a 21
combination of sorption and partial precipitation. An integrated system of submerged DCMD 22
with zeolite for AMD treatment enabled to achieve 50% water recovery in 30 h. The 23
integrated system provided a favourable condition for zeolite to be used in powder form with 24
full contact time in a storing tank. Likewise, heavy metal removal from AMD by zeolite, 25
specifically Fe and Al, mitigated membrane fouling on the surface of the hollow fiber 26
*Manuscript (double-spaced and continuously LINE and PAGE numbered)
Click here to view linked References

2
submerged membrane. The integrated system produced high quality fresh water while 27
concentrating sulfuric acid and valuable heavy metals (Cu, Zn and Ni). 28
29
Keywords 30
Acid mine drainage, Heavy metal, Integrated process, Submerged membrane distillation, 31
Sorption, Zeolite 32
33
1. Introduction 34
The formation of acid mine drainage (AMD) is a natural process attributed to the oxidation of 35
sulfide minerals such as pyrites (Kalin et al., 2006; Mosley et al., 2018). Active and 36
abandoned mines intensifies the formation of AMD due to open pits, mining waste rock, 37
structures and tailings that are exposed to water, air and bacterial activity (Kalin et al., 2006; 38
Mosley et al., 2018; Tolonen et al., 2014). AMD is characterized by low pH and high 39
concentration of sulfate, as well as high concentrations of heavy metals activity (Kalin et al., 40
2006; Mosley et al., 2018; Tolonen et al., 2014). Nearby water streams are susceptible to 41
AMD infiltration, resulting in discoloration of streams, decrease in pH and accumulation of 42
heavy metals. In Australia, there are a significantly high amount of abandoned mines (more 43
than 50,000 mines) compared to actively operating mines (around 380 mines) (Parbhakar-Fox 44
et al., 2014; Unger et al., 2012). An estimated total land area of 215,000 km
2
around 45
coastlines and inlands in Australia contain acid sulfate soils attributed to AMD (Fitzpatrick et 46
al., 2009). The long-term impact of AMD contaminant on aquatic organisms, plant growth 47
and human health is a significant concern, which necessitates AMD treatment (Mosley et al., 48
2018). 49
50

3
Conventionally, AMD is treated by using alkaline neutralizing chemicals such as caustic soda 51
or limestone, to elevate the pH and precipitate metals (Tolonen et al., 2014). Although 52
efficient, precipitation results in large volumes of sludge containing heavy metals that require 53
safe disposal (Marcello et al., 2008). Various other active and passive remediation 54
approaches such as bioremediation, wetlands, adsorption, phytoremediation are also used to 55
treat AMD (Zhang, 2011; Vasquez et al., 2016; Crane and Sapsford, 2018). In this regard, the 56
uptake of heavy metals by low-cost sorbents are especially promising as a cost effective 57
treatment method for AMD. 58
59
In Australia, naturally occurring zeolites are available in large quantities at relatively low cost 60
(Santiago et al., 2016). A significant advantage of zeolite is its tendency to adsorb cations. 61
The ion exchange affinity of natural and synthetic zeolites for metal extraction from 62
wastewater solution including acid mine drainage has been described by previous studies 63
(Motsi et al., 2009; Rios et al., 2008; Wingenfelder et al., 2005). Castle Mountain, Australia 64
produces a natural clinoptilolites (An et al., 2011). The uptake of heavy metals from AMD by 65
Australian natural clinoptilolites may offer a low cost treatment option for AMD. In this 66
regard, a number of approaches are used to enhance the sorption capacity of natural zeolite 67
such as heat treatment, surface and chemical modification (Motsi et al., 2009; Taffarel and 68
Rubio, 2010; Turner et al., 2000). Motsi et al. (2009) reported on the enhanced heavy metal 69
removal of natural zeolite upon microwave and furnace heat treatment. Heat treatment for 70
enhancing the performance of natural zeolite is especially attractive given that it requires no 71
additional chemicals and complex processes. 72
73
Compared to the conventional approach of treat and discharge, more focus is now being 74
placed on achieving water reuse for AMD treatment. Therefore, membrane technologies are 75

4
becoming favourable AMD treatment options. This is especially reflected by the increase in 76
the implementation of membrane treatment processes such as reverse osmosis (RO) and 77
nanofiltration (NF) at actual mining sites (Aguiar et al., 2016; Ambiado et al., 2017). 78
Although NF and RO do meet good water reuse standards, membrane fouling and low 79
recovery rate remain challenges. In view of this, recent studies are exploring the potential of 80
alternative membrane processes such as electrodialysis, and forward osmosis for AMD 81
treatment. For instance, Martí-Calatayud et al. (2014) reported on the promising capacity of 82
electrodialysis for treating AMD but inorganic membrane precipitation by metals such as iron 83
was a significant drawback. Similarly, Vital et al. (2018) explored the feasibility of using 84
forward osmosis with NaCl as a draw solution for treating AMD. Although FO was able to 85
achieve more than 98% rejection of ions, the phenomenon of reverse salt flux and dilution of 86
draw solution were major limitations. 87
88
Alternatively, membrane distillation (MD), a thermal based membrane process, has shown 89
promising potential for treating acid based wastewater from metal pickling industry 90
(Tomaszewska et al., 2001), and concentrating various types of acid including sulfuric acid 91
from AMD (Kesieme et al., 2012; Tomaszewska and Mientka, 2009). The suitability of MD 92
for concentrating acid is attributed to its capacity to achieve high rejection of non-volatile 93
compounds with up to 90% water recovery ratio, producing good quality fresh water by using 94
vapor pressure difference as its driving force. Additionally, MD requires minimal electrical 95
energy requirement compared to pressure operated systems such as RO and NF while the low 96
thermal requirement (40 80 °C) can be met by alternative thermal sources such as solar or 97
waste heat (Khayet, 2013). MD offers a promising potential for achieving near zero liquid 98
discharge for small scale treatment such as AMD (Naidu et al., 2014; Naidu et al., 2017). 99
100

Figures (15)
Citations
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TL;DR: Insight is provided in establishing reuse and resource recovery as the holistic approach towards sustainable AMD treatment and integrated technologies that deserve in depth future exploration are highlighted.
Abstract: Acid mine drainage (AMD) is a global environmental issue. Conventionally, a number of active and passive remediation approaches are applied to treat and manage AMD. Case studies on remediation approaches applied in actual mining sites such as lime neutralization, bioremediation, wetlands and permeable reactive barriers provide an outlook on actual long-term implications of AMD remediation. Hence, in spite of available remediation approaches, AMD treatment remains a challenge. The need for sustainable AMD treatment approaches has led to much focus on water reuse and resource recovery. This review underscores (i) characteristics and implication of AMD, (ii) remediation approaches in mining sites, (iii) alternative treatment technologies for water reuse, and (iv) resource recovery. Specifically, the role of membrane processes and alternative treatment technologies to produce water for reuse from AMD is highlighted. Although membrane processes are favorable for water reuse, they cannot achieve resource recovery, specifically selective valuable metal recovery. The approach of integrated membrane and conventional treatment processes are especially promising for attaining both water reuse and recovery of resources such as sulfuric acid, metals and rare earth elements. Overall, this review provides insights in establishing reuse and resource recovery as the holistic approach towards sustainable AMD treatment. Finally, integrated technologies that deserve in depth future exploration is highlighted.

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Abstract: Membrane distillation (MD) is a promising alternative thermal-based membrane process that can achieve high-quality freshwater across various impaired water sources. However, the performance of MD as a stand-alone system remains a challenge for attaining commercialization. Hybrid MD - the integration of MD with other processes - offers a practical approach for performance enhancement as well as the possibility to achieve valuable resource recovery. This review details the performance and related challenges of various hybrid MD systems with a focus on resource recovery. On the basis of recovering valuable salt/element from impaired water sources, hybrid MD-crystallizer is limited to the recovery of major salts. Comparatively, MD-adsorbent exhibits potential for selectively recovering valuable elements, which may offset treatment cost. Meanwhile, hybrid MD-bioreactor (MDBR) and MD-forward osmosis (MD-FO) are especially favorable combinations for attaining water reclamation from the wastewater industry and recovering nutrients and biogas that mitigates environmental pollution. Simultaneous recovery of water and energy can be attained with hybrid MD-pressure retarded osmosis (MD-PRO) and MD-reverse electrodialysis (MD-RED). Overall, this review highlights the favorable potential of hybrid MD for recovering resources in niche applications. Future suggestions for improving hybrid MD are discussed, specifically pilot-scale application, module configuration and membrane development.

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Abstract: Acid mine drainage induced by the mining industry causes environmental and economic issues. Acid mine drainage contains mainly metals such as Fe, Al, Cu, Ca, Mg, Mn and Zn. Preventing the formation of acid mine drainage has not been found feasible. As a consequence, remediation treatments have been developed during the last years to remove metals and obtain high-quality water, which may be reused. We review here several treatment options such as selective metal precipitation, adsorption, electrochemical processes and membrane processes. Adsorption is the most employed commercially since it can recover 99% of the metals. Membrane processes are promising according to lab-scale results, notably because high-quality water is obtained. Further research is necessary to implement combination of technologies, e.g., adsorption membrane, at larger scales, as well as to obtain more valuable products that can balance the overall economy for the mining industry.

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01 Dec 2006
TL;DR: The study was carried out on the sorption of heavy metals under static conditions from single- and multicomponent aqueous solutions by raw and pretreated clinoptilolite and results fit well to the Langmuir and the Freundlich models.
Abstract: The study was carried out on the sorption of heavy metals (Ni2+, Cu2+, Pb2+, and Cd2+) under static conditions from single- and multicomponent aqueous solutions by raw and pretreated clinoptilolite. The sorption has an ion-exchange nature and consists of three stages, i.e., the adsorption on the surface of microcrystals, the inversion stage, and the moderate adsorption in the interior of the microcrystal. The finer clinoptilolite fractions sorb higher amounts of the metals due to relative enriching by the zeolite proper and higher cleavage. The slight difference between adsorption capacity of the clinoptilolite toward lead, copper, and cadmium from single- and multicomponent solutions may testify to individual sorption centers of the zeolite for each metal. The decrease of nickel adsorption from multicomponent solutions is probably caused by the propinquity of its sorption forms to the other metals and by competition. The maximum sorption capacity toward Cd2+ is determined as 4.22 mg/g at an initial concentration of 80 mg/L and toward Pb2+, Cu2+, and Ni2+ as 27.7, 25.76, and 13.03 mg/g at 800 mg/L. The sorption results fit well to the Langmuir and the Freundlich models. The second one is better for adsorption modeling at high metal concentrations.

499 citations


Journal ArticleDOI
Abstract: The adsorption behaviour of natural zeolite (clinoptilolite) has been studied in order to determine its applicability in treating acid mine drainage (AMD) containing 400, 20, 20 and 120 mgl− 1 of Fe3+, Cu2+, Mn2+ and Zn2+ respectively. Tests to determine both the rate of adsorption and the uptake at equilibrium were performed under batch conditions from single and multi-component solutions. The optimum conditions for the treatment process were investigated by observing the influence of pH levels, the presence of competing ions, varying the mass of zeolite and thermal modification of the natural zeolite (calcination and microwaves). The adsorption studies showed rapid uptake in general for the first 40 mins, corresponding to ∼ 80% total removal. After this initial rapid period, the rate of adsorption decreases. According to the equilibrium studies, the selectivity sequence can be given as Fe3+ > Zn2+ > Cu2+ > Mn2+, with good fits being obtained using Langmuir and Freundlich adsorption isotherms. Preliminary tests using AMD samples from Wheal Jane Mine, UK, showed that natural zeolite has great potential as an alternative low cost material in the treatment of acid mine drainage.

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TL;DR: This mineral showed the same high sorption capacity values when used in the purification of metal electroplating waste waters, appearing, therefore, as most suitable to perform metal waste water purification processes.
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TL;DR: The immobilization of the metals during pH increase and the subsequent remobilization caused by re-acidification can be well described by a geochemical equilibrium speciation model that accounts for metal complexation at hydrous ferric oxides, for ion exchange on the zeolite surfaces, as well as for dissolution and precipitation processes.
Abstract: In this study, we investigated the removal of Fe, Pb, Cd, and Zn from synthetic mine waters by a natural zeolite. The emphasis was given to the zeolite's behavior toward a few cations in competition with each other. Pb was removed efficiently from neutral as well as from acidic solutions, whereas the uptake of Zn and Cd decreased with low pH and high iron concentrations. With increasing Ca concentrations in solution, elimination of Zn and Cd became poorer while removal of Pb remained virtually unchanged. The zeolite was stable in acidic solutions. Disintegration was only observed below pH 2.0. Forward- and back-titration of synthetic acidic mine water were carried out in the presence and absence of zeolite to simulate the effects of a pH increase by addition of neutralizing agents and a re-acidification which can be caused by subsequent mixing with acidic water. The pH increase during neutralization causes precipitation of hydrous ferric oxides and decreased dissolved metal concentrations. Zeolite addition further diminished Pb concentrations but did not have an effect on Zn and Cd concentrations in solution. During re-acidification of the solution, remobilization of Pb was weaker in the presence than in the absence of zeolite. No substantial differences were observed for Fe, Cd, and Zn immobilization. The immobilization of the metals during pH increase and the subsequent remobilization caused by re-acidification can be well described by a geochemical equilibrium speciation model that accounts for metal complexation at hydrous ferric oxides, for ion exchange on the zeolite surfaces, as well as for dissolution and precipitation processes.

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Abstract: As a low Si/Al ratio zeolite, cancrinite received very scant study in previous studies on the adsorption removal of heavy metals from water. In this study, a cancrinite-type zeolite (ZFA) was synthesized from Class C fly ash via the molten-salt method. Adsorption equilibriums of Pb2+, Cu2+, Ni2+, Co2+, and Zn2+ on ZFA were studied in aqueous solutions and were well represented by Langmuir isotherms. The increase of pH levels during the adsorption process suggests that the uptake of heavy metals on ZFA was subjected to an ion exchange mechanism. It is found that the maximum exchange level (MEL) follows the order: Pb2+ (2.530 mmol g−1) > Cu2+ (2.081 mmol g−1) > Zn2+ (1.532 mmol g−1) > Co2+ (1.242 mmol g−1) > Zn2+ (1.154 mmol g−1). Comparison with previous studies shows that the MEL of ZFA is higher than the commonly used natural zeolites; and it is also comparable to (or higher than) several synthetic zeolites and ion exchange resins. The high MEL of heavy metals on ZFA is attributed to the high cation exchange capacity (CEC) and proper pore size of cancrinite. The pseudo-first-order kinetics suggests that the ion exchange processes were diffusion-controlled.

241 citations