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Journal ArticleDOI

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

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).
About: This article is published in Chemosphere.The article was published on 2019-03-01 and is currently open access. It has received 48 citations till now. The article focuses on the topics: Sorption & Membrane fouling.

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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Citations
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Journal ArticleDOI
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.

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TL;DR: In this article, the performance and related challenges of various hybrid Membrane Distillation (MD) systems with a focus on resource recovery are discussed. And future suggestions for improving hybrid MD are discussed, specifically pilot-scale application, module configuration and membrane development.

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Journal ArticleDOI
TL;DR: In this article, the authors review several treatment options such as selective metal precipitation, adsorption, electrochemical processes and membrane processes for acid mine drainage, and conclude that membrane processes are the most promising according to lab-scale results, notably because high quality water is obtained.
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.

71 citations

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TL;DR: This study proposes three more sustainable solutions for reducing and eventually eliminating the impact of AMD with less capital investment while also resolving the landfill problem as well.

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TL;DR: Excellent stability of P-60S-EDTA membrane in continuous operation of 36 h in both ideal and practical water environment suggests its promising application in real field heavy metal contaminated waste water treatment.

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References
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Journal ArticleDOI
TL;DR: In this paper, the authors used DMC for the removal of heavy metals from simulated acid mine drainage and found that the adsorption affinity order of the three heavy metals was Pb>Cu>Zn, while negligible effect for Pb.

125 citations

Journal ArticleDOI
TL;DR: In this paper, a direct contact membrane distillation (DCMD) was evaluated as a treatment option of wastewater reverse osmosis concentrate (WWROC) discharged from wastewater reclamation plants (WRPs).

124 citations

Journal ArticleDOI
TL;DR: In this article, the authors evaluated the application of forward osmosis (FO) for the treatment of acid mine drainage (AMD) using a thin-film composite FO membrane, and two types of draw solutions: NaCl and NH4HCO3.

117 citations

Journal ArticleDOI
TL;DR: In this article, Membrane distillation (MD) was applied for the concentration of solutions containing hydrochloric acid and salts, and it was found that under MD conditions through pores of a hydrophobic membrane both water vapor and hydrogen chloride are transported.

109 citations

Journal ArticleDOI
TL;DR: In this article, three HEU-type zeolites from Armenia, Georgia and Greece formed from alteration of volcanic glass were treated with dilute KOH and subsequently either reacted with 6N HCl or heated at 700 °C.

106 citations