The removal of pollutants and natural organic compounds from acid mine drainage using a combination of bentonite clay and MgSO4

Abstract 200 mL of synthetic acid mine drainage (AMD) sample was poured into five 500 mL glass beakers and treated in a jar test and a shaker in sets of experiments, respectively. The samples were treated in small-scale laboratory experiments using synthetic AMD sample dosed with bentonite clay and MgSO4 respectively, and a flocculant consisting of the same reagents. The pH, EC, turbidity and oxidation reduction potential were measured. The removal of turbid materials in the samples dosed with a flocculant is higher compared to those of the samples dosed with each reagent alone. The samples with flocculant dosage show high removal efficiency of natural organic compounds and toxic metals, slightly higher compared to those with a dosage of a combination of bentonite clay and MgSO4. The removal efficiency of the samples treated in a shaker is better than those with rapid mixing. The SEM micrographs show sorption is a physico-chemical phenomenon.

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The removal of turbid materials from AMD using bentonite clay, Fe or Al salt, MgCO3 and flocculent with varying agitations

Water Practice & Technology ◽

10.2166/wpt.2020.040 ◽

2020 ◽

Vol 15 (3) ◽

pp. 580-597

Author(s):

I. O. Ntwampe

Keyword(s):

Removal Efficiency ◽

Mine Drainage ◽

Bentonite Clay ◽

Jar Test ◽

Oxidation Reduction ◽

Treated Effluent ◽

Oxidation Reduction Potential ◽

Changing Trend ◽

Series Of Experiments ◽

Slow Mixing

Abstract A series of experiments was conducted using 200 mL of acid mine drainage (AMD) collected from Krugersdorp, South Africa, to determine turbid materials removal efficiency of a combination of bentonite clay, Fe or Al salt and MgCO3. The sample was poured into five 500 mL glass beakers using bentonite clay, FeCl3, AlCl3 and MgCO3 dosage respectively. The samples were treated in jar test at rapid and slow mixing, allowed to settle for 1 hour, then the pH, conductivity, total suspended solids (TSS), dissolved oxygen (DO) and oxidation reduction potential (ORP) were measured (exp A). A second and third similar sets of experiments were conducted with a combination of bentonite clay and MgCO3 (flocculent) dosage (exp B), and FeCl3 with slow mixing only (exp C). Experimental results revealed that the pH of treated effluent with bentonite clay does not exhibit significant increasing trend because of insignificant hydrolysis, whereas the pH of samples with FeCl3, AlCl3 and MgCO3 exhibit a slight decreasing trend, showing a low rate of hydrolysis. The DO and ORP of treated effluent does not show a significant changing trend compared to the untreated AMD sample. Residual TSS of the AMD samples treated with a flocculent is lower than the samples treated with bentonite clay, FeCl, AlCl3 and MgCO3. Residual turbidity of the samples with rapid mixing is identical to that of the corresponding samples with slow mixing. TSS removal efficiency of a flocculent is higher compared to other reagents. The results show that synthetic flocculent is an ideal replacement for inorganic coagulants. The scanning electron microscopy (SEM) micrographs exhibit slides with dense-sponge like flocs showing high adsorption capacity.

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Treatment of AMD using a combination of saw dust, bentonite clay and phosphate in the removal of turbid materials and toxic metals

Water Practice & Technology ◽

10.2166/wpt.2021.014 ◽

2021 ◽

Author(s):

I. O. Ntwampe

Keyword(s):

South Africa ◽

Particle Size ◽

Removal Efficiency ◽

Toxic Metals ◽

Laboratory Experiments ◽

Mine Drainage ◽

Bentonite Clay ◽

Small Scale ◽

Saw Dust ◽

Natural Organic Compounds

Abstract Acid mine drainage collected from the western decant in South Africa was treated in a series of small-scale laboratory experiments. 200 mL of the sample was poured into five 500 mL glass beakers using flocculants formed by mixing size-optimized 1.5 g of bentonite clay with 3.5 g saw dust and 1.0 g of Na3PO4 in triplicates (experiment A). Four similar sets of control experiments were conducted using the same amount of bentonite clay and saw dust with varying Na3PO4, contents in AMD treatment; the rationale being to determine the efficiency of Na3PO4 (experiments B, C and D). The results show that conductivity has an influence in the removal of the turbid materials. The removal efficiency of toxic metals using a flocculant containing 220 μm bentonite clay particle size and 0.012 or 0.25 M of Na3PO4 is higher than 96% when compared to that of the samples dosed with a flocculant containing 0.05 M Na3PO4, which is less than 91%. The flocculent also showed optimal removal efficiency of both turbid materials and toxic metals, i.e. removal efficiency within a range 96.5–99.3%. The flocculants containing 0.025 M Na3PO4 showed optimal removal efficiency of turbidity, colour, toxic metals and natural organic compounds.

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Performance of microbial community dominated by Bacillus spp. in acid mine drainage remediation systems: A focus on the high removal efficiency of SO42-, Al3+, Cd2+, Cu2+, Mn2+, Pb2+, and Sr2+

Heliyon ◽

10.1016/j.heliyon.2021.e07241 ◽

2021 ◽

pp. e07241

Author(s):

Enoch A. Akinpelu ◽

Seteno K.O. Ntwampe ◽

Elvis Fosso-Kankeu ◽

Felix Nchu ◽

Justine O. Angadam

Keyword(s):

Microbial Community ◽

Acid Mine Drainage ◽

Removal Efficiency ◽

Mine Drainage ◽

Acid Mine ◽

Bacillus Spp

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Enhanced Monovalent Cation Biomineralization Ability by Quartz Sand for Effective Removal of Soluble Iron in Simulated Acid Mine Drainage

Water ◽

10.3390/w12030732 ◽

2020 ◽

Vol 12 (3) ◽

pp. 732

Author(s):

Heru Wang ◽

Mengying Li ◽

Yongwei Song

Keyword(s):

Heavy Metals ◽

Acid Mine Drainage ◽

Removal Efficiency ◽

Quartz Sand ◽

Mine Drainage ◽

Monovalent Cation ◽

Iron Minerals ◽

Precipitation Efficiency ◽

Acid Mine ◽

Effective Removal

Acid mine drainage (AMD) is characterized by low pH, high soluble Fe, and heavy metal concentrations. Conventional lime neutralization produces large amounts of Fe(OH)2 and Fe(OH)3, which complicate subsequent disposal. Secondary iron minerals synthesized by biomineralization can reduce the concentration of soluble Fe in addition to adsorbing and removing heavy metals in AMD. Therefore, an appropriate method for improving the precipitation efficiency of Fe is urgently needed for AMD treatment. Using simulated AMD, this work analyzes the influence of quartz sand (40 g/L) on the Fe2+ oxidation and total Fe deposition efficiencies, as well as the phases of secondary iron minerals in an Acidithiobacillus ferrooxidans system including K+, Na+, or NH4+ (53.3 mmol/L). Quartz sand had no significant effect on Fe2+ oxidation and 160 mmol/L Fe2+ was completely oxidized by A. ferrooxidans in 168 h, but contributed to the oxidized product (Fe3+) mineralization, improving the total Fe removal efficiency in simulated AMD. Compared with treatments involving K+ or Na+ alone, quartz sand improved the total Fe precipitation efficiency by 26.6% or 30.2%, respectively. X-ray diffraction showed that quartz sand can promote the transformation of the biomineralization pathway from schwertmannite to jarosite with higher yields, which is important for improving the removal efficiency of heavy metals in AMD.

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Bioremediation of acid mine drainage and crude contaminated soils

10.51415/10321/3628 ◽

2020 ◽

Author(s):

◽

Yusuf Makarﬁ Isa

Keyword(s):

Acid Mine Drainage ◽

Crude Oil ◽

Removal Efficiency ◽

Contaminated Soils ◽

Mine Drainage ◽

Metal Removal ◽

Air Injection ◽

Treatment System ◽

Acid Mine ◽

Removal Efficiencies

Pollution is one of the greatest ills plaguing the existence of the ecosystem which could lead to the annihilation of terrestrial and aquatic habitat if not remedied. Acid mine drainage (AMD) and crude oil are among the major land and water pollutants cause by industrial and human activities. The constant exploration, mining, and processing of mineral resources and prevalent use of petroleum products for economic purposes have contributed to contamination of soil and proximate water bodies which results in environmental degradation; thus, remediation becomes necessary. The treatment of AMD contaminated soils using the conventional methods has some room for improvement to meet the remediation purpose. Bioremediation technology provides a sustainable and eco-friendly approach to the treatment of contaminants. This study aims to evaluate the performance of different potential bioremediation techniques and conduct a comparative analysis of these methods for the treatment of AMD and crude oil-contaminated soils. The treatment approach for both pollutants comprises of soils separately contaminated with AMD and crude oil before the application of bioremediation techniques. For the biostimulation study, contaminated soils were amended with varying ratios of the brewery or municipal wastewaters (BWW and MWW), while the bioventing (BVT) treatment involved wastewater amendment and supply of atmospheric air from the vadose zone at 3L/min at 30 minutes intervals every 48 hours. The bacteria strain Pseudomonas aeruginosa ATCC 15442 used for the study which was inoculated at 5%(w/w) was cultured in two different media for respective treatments and wastewater was amended as an extra energy source for bioaugmentation (BAU) study while Bioattenuation (BAT) which received no amendment was used as a control treatment for the study. The treatments were conducted in plastic bioreactors under mesophilic conditions for 28 days and samples were collected from each treatment system on weekly basis to analyse for sulfate, heavy metals, and total petroleum hydrocarbon (TPH) reduction. The result of the study showed that the amendment of contaminated soils with wastewater increased alkalinity in the system which enhanced microbial activities for effective remediation which recorded 52.43 and 51.23% average TPH and metal removal efficiency for the BSTc treatment. Also, the combined application of bioremediation techniques was more effective than single application as the introduction of oxygen into the treatment system with wastewater amendment increased the TPH and metal removal efficiency by an average of 12.98 and 13.17% respectively but efforts to enhance sulfate removal by air-injection (BVTa) proved abortive with 17.20 and 14.67% removal efficiencies less than BSTa and BAUa respectively as sulfate-reducing bacteria thrive in an anaerobic environment. However, P. aeruginosa ATCC 15442 adopts the sorption process in the reduction of hydrocarbon and metal toxicity with 42.02 and 41.81% average removal efficiencies respectively and the amendment extra nutrient (wastewater) increased the removal efficiency of these pollutants by 25.24 and 16.23% respectively. The results of the study inferred that wastewater (BWW and MWW), air-injection and P. aeruginosa ATCC 15442 showed great potentials in the degradation and removal of TPH, metals and sulfate contaminants, hence, can serve as a viable strategy for the remediation of AMD and crude oil polluted soils while improving waste management and amelioration of pollution aftermath faced by communities involved in mining and oil production and/or processing. There is a need for optimization to ensure effective remediation while further study is required to validate large scale application.

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The effect of saw dust in a flocculent with bentonite clay and FeSO4 in AMD treatment without addition of a neutralizer

Water Practice & Technology ◽

10.2166/wpt.2019.051 ◽

2019 ◽

Vol 14 (3) ◽

pp. 633-644 ◽

Cited By ~ 1

Author(s):

I. O. Ntwampe

Keyword(s):

Reduction Potential ◽

Mine Drainage ◽

Bentonite Clay ◽

Similar Treatment ◽

Saw Dust ◽

Jar Test ◽

Oxidation Reduction ◽

Oxidation Reduction Potential ◽

Removal Efficiencies ◽

Synthetic Acid

Abstract 200 mL of synthetic acid mine drainage (AMD) was poured into five 500 mL glass beakers and treated in a jar test. The samples were dosed with 1.0–2.5 g bentonite clay, 20–60 mL of 0.025 or 0.05 M FeSO4 and 1.0–2.5 g saw dust respectively. The samples were mixed at 250 rpm for 2 minutes and reduced to 100 rpm for 10 minutes. The samples were allowed to settle for 1 hour, after which the pH, oxidation-reduction potential (ORP) and turbidity were measured (exp. A). Two other similar sets of experiments were conducted by dosing the samples with a combination of bentonite clay and FeSO4 with and without saw dust, similar treatment and measurements (exp. B and exp. C), similar treatment and measurements were conducted. The pH and the efficiencies of the flocculants containing 0.025 and 0.05 M Fe3+ in FeSO4 are similarly identical. The removal of turbid materials from the samples with FeSO4 is the lowest, followed by a combination of bentonite clay and FeSO4, whereas a combination of bentonite clay, FeSO4 and saw dust the highest. Comparative removal efficiencies between the two flocculants show that the presence of FeSO4 is relatively insignificant. The removal efficiency of a combination of bentonite clay, FeSO4 and saw dust from AMD sample is low with for Cu2+, and optimal for both Ni2+ and Fe2+ ions.

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