Mining Effluents Research Articles

Research Investigates and Simulation Behavior of the Failure Characteristics of Red Mud–Loess Type Permeable Reactive Barriers PRB in Fixed‐Bed Column Experiments

Controlling and remediating water and soil pollution while efficiently utilizing solid waste is essential for comprehensive environmental protection and sustainable development, particularly in establishing green, low‐carbon economic systems in China. We evaluate the impact of initial concentration, flow rate, and bed height on breakthrough performance and adsorption capacity using the Tessier method under dynamic water flow conditions. Additionally, we analyze micromorphological changes in the red mud–loess mixture before and after breakthrough by acid mine drainage containing Pb and Cd in mining areas, employing soil column experiments and numerical simulations with COMSOL Multiphysics. Our findings suggest that reducing initial concentration and flow rate while increasing bed height leads to higher breakthrough time, saturation time, and adsorption capacity for Pb and Cd in the red mud–loess mixture (7 : 3). Furthermore, the red mud–loess blend (7 : 3) demonstrates sustained and efficient acid‐buffering capability in the presence of acid mine drainage containing Pb and Cd. Notably, under specific conditions (initial Pb content at 100 mg/L, a height of 7 cm, and flow rate set at 1 mL/min), the adsorption capacity of red mud–loess (7 : 3) reaches 17.30 mg/g. The prescribed minimum length for PRBs is 11.40 cm. Under specified conditions (Cd concentrations at 100 mg/L, a height of 5 cm, and a flow rate of 1 mL/min), the material exhibits a notable adsorption capacity of 29.91 mg/g, with a theoretical minimum length for PRBs at 8.95 cm. Increasing bed heights successfully remove Pb and Cd ions through chemical precipitation. The BDST model accurately describes the breakthrough curves of Pb and Cd and develops a correlation formula for the breakthrough time of red mud–loess PRB medium. As the saturation of Pb increases from 0.05 to 0.85, the maximum volume adsorption capacity of Pb increases from 1.78 to 2.98 mg/L, while for Cd, it increases from 4.15 to 7.87 mg/L. Elevating the bed height first triggers chemical precipitation, hence improving Pb and Cd removal. Consequently, the longevity of red mud–loess PRB in acidic mine effluent containing Pb and Cd surpasses predicted theoretical outcomes. These observations reveal correlations between the breakthrough length for red mud–loess permeable reactive barriers and the bed height. Furthermore, the distribution of Pb speciation within the red mud–loess mixture (7 : 3) is primarily governed by the presence of iron–manganese oxide, while the composition of Cd speciation is chiefly influenced by the carbonate form and iron–manganese oxide. After treating acidic mine wastewater with Pb and Cd, the red mud–loess mixed material (7 : 3) undergoes surface changes, shifting from smooth to rough due to H+ corrosion. Pores between particles enlarge, yet heavy metal ions, adsorbates, and precipitates reoccupy and cover the surface, transforming the particle morphology from dense lamellar to clustered spherical. Our innovative approach to combining waste materials for environmental remediation presents a cost‐effective and impactful solution for heavy metal pollution.

Capacitive deionization of uranium mediated by dioxygen functionalities in the C = O = C = O segment of polyacrylic acid-functionalized graphene aerogel

The extraction of uranium is crucial for sustaining a consistent nuclear fuel cycle, yet the task of isolating uranyl ions from aqueous solutions presents formidable challenges. Herein, a PAA/GO aerogel was developed using polyacrylic acid-functionalized graphene, wherein the C = O = C = O segment's dual oxygen served both as electrodes for capacitive deionization and as sites for charge transfer and uranyl capture, effectively purifying uranium mine wastewater. Furthermore, under the stringent experimental conditions set at 298 K and a pH of 5.5, the PAA/GO composite demonstrated an impressive adsorption capacity of 898.7 mg g−1. When this composite was further amalgamated into the CDI architecture, it exhibited an impressive 92 % uranium extraction from genuine mine effluent at an unwavering potential of 0.9 V. Through density functional theory (DFT) analyses, the adsorption energies of [UO2(H2O)5]2+ with the PAA/GO composite involving C = O = C = O ligands displayed the highest value compared with PAA and PAA/GO composite (involving monodentate and bidentate ligands). The Bader charge analysis further indicating the greatest charge loss in the uranium ion. In conclusion, the novel PAA/GO aerogel 3D framework with its specific C = O = C = O regional chain sets a pioneering standard in uranium extraction techniques, showcasing unprecedented efficiency in UO22+ removal from aqueous solutions.

Copper nanoparticles production by a novel non-dispersive membrane nanoprecipitation process

This study presents, for the first time, a novel route for producing elemental copper nanoparticles using a non-dispersive membrane nanoprecipitation process based on membrane contactors. Copper sulfate solutions ranging between 0.005 and 0.01 M Cu concentration were circulating through a hydrophobic polypropylene flat-sheet membrane, where hydrazine solutions with 1.84–3.64 M were fed by the other side of the membrane. The gradient of hydrazine concentration between both phases was the driving force that promoted the volatilization and transfer of hydrazine through the membrane pores, then reacting with cupric ions to precipitate elemental copper. The effects of copper concentration, hydrazine concentration, and temperature (20–40 °C) in the particle size distribution were assessed. Smaller nanoparticle sizes were obtained at the lowest copper concentration and the highest hydrazine concentration. Thus, the smallest copper nanoparticles were produced under the highest hydrazine/copper molar ratio, reaching values of around 200 nm. Besides, the precipitates showed a surface plasmon resonance, confirming the presence of elemental copper nanoparticles. Therefore, this study opens a new approach to producing metal nanoparticles with perspectives of application in industrial manufacturing, recovering valuable metals from mining effluent treatment, or even hydrometallurgical processes.

Hydrogeochemical characteristics and quality assessment of surface and groundwater around Adudu-Abuni lead-zinc minefields, Northcentral Nigeria

ABSTRACTThis study aims to evaluate the effects of contaminants on the surface and groundwater resources in the mining communities of Adudu-Abuni, Central-Nigeria. Thirty-one (31) water samples including 21 surface (streams) and 10 groundwater were analyzed for physicochemical parameters (major cations, anions, and heavy metals) using the APHA (2011) and (ICP-MS) standard methods. Physicochemical analysis showed that the concentration of heavy metal for both surface and groundwater of the area in the following order of abundance Fe>Pb>Zn>Cu>Cr>Cd>As and Fe>Zn>Pb>Cu>Cr>Cd>As, respectively. High concentrations of the heavy metals in the surface and groundwater are attributed to anthropogenic activities; improper channeling of mine effluents into the environments, these effluents reacted via oxidation and dissolution process, making solutions (contaminants) infiltrate into the aquifer system. Results showed for both surface (67%) and groundwater (70%) waterfall within the rock weathering dominance for both anions and cations, with few exceptions who fall into the precipitation dominance, suggesting that rock–water interface is the primary influencer for both surface and groundwater chemistry. This deduced that rock weathering and precipitations are the principal factors controlling the water chemistry in the study areas. WQI analysis for groundwater shows that the northern axis of the area depicts poor water quality while the southern regions are good for drinking. Whereas surface water source from the southern zones is unsuitable for drinking, while those in the northern region are good. This is attributed to the proximity of Pb-Zn mines to the southern region because streams within this zone serve as repositories for mine effluents.

Assessing environmental health impacts of coal mining exploitation in Iran: A Rapid Impact Assessment Matrix (RIAM) approach for environmental protection

Environmental Impact Assessment is the process of evaluating the effects caused by a project on the environment. The outcomes generated by this assessment can lead to a reduction of the negative effects and an increase in the positive effects caused by mine projects. The present study was conducted to evaluate the environmental impact assessment of the Goliran Coal Mine in northern Iran. In the descriptive-analytical study, to achieve the objectives, observatory surveys were conducted around the coal mine using a checklist, which was about the positive and negative effects of a coal mine. Then the data were entered into the RIAM and the positive and negative effects were ranked and the most important effects were determined. In RIAM, one point is assigned to each component. 17 important activities for environmental impacts were identified using a checklist. Among the activities carried out at the coal mine site, the major ones included tunnel excavation, construction of the rail line collection and disposal of coal mine effluent, coal transportation, collection and disposal of mine tailings, and technical defects and leakage. The scores of each environmental factor were based on the four environmental components: physical/chemical, biological/ecological, social/cultural, and economic/operational. The results of the present study showed that the most negatively affected environmental components are the physical/chemical components derived from three activities; the construction of the underground tunnel; the construction of a coal transport rail line; and the actual transportation of coal extracts. The scores of each environmental factor based on the four components at the Goliran coal mine in northern Iran indicate that the highest negative score was -64, corresponding to the physical/chemical component, and was assigned to air pollution. On the other hand, the highest positive score corresponds to the economic/operational component with +54, assigned to the income that employees earn from the mine. Overall results showed that the coal mine in northern Iran had negative effects on the environment but the effects were not severe. It is suggested that for future research, corrective measures should be taken in the form of an environmental management plan to reduce the negative effects caused by coal mining, and then prospective research should be done to check the extent of reducing the negative effects.

Lakes in the Anthropocene: Reflections on Tracking Ecosystem Change in the Arctic

This book - requested by S.J. Hawkins, the Editor of Excellence in Ecology, when John Smol was recognized with the International Ecology Institute Prize - is certainly one of the most modern and complete texts on the Canadian Arctic. The polar area like many other extreme environments that I studied during my scientific activity (e.g., Greenland, Antarctica, Svalbard archipelago, Finland Lapland and mountain ecosystems), has for years been subject to great alterations due to climate changes (“the big threat multiplier”), mine effluents, local and long-distance pollution. The book provides an excellent overview of how the arctic environment has developed during the last ca. 200 years and even before. The Arctic environment is transforming rapidly....

Vanadium removal and floc characteristics of tannin biocoagulants and iron sulphate in the treatment of mine effluent

This study compared the performance of tannin (quebracho and spruce) and iron sulphate (FS) coagulants for the removal of vanadium from effluent derived from an abandoned vanadium mine. The efficacy of the materials was studied at the natural pH of the mine effluent (7.4), and at adjusted pH levels of 4 and 9. The quebracho tannin coagulant (QT) recorded impressive turbidity and vanadium removals of above 88% over a wide pH range. However, the spruce tannin coagulant (ST) was not as effective at pH 9 (39%) although it showed an improved vanadium removal of 46% and 70% at pH 7.4 and 4, respectively. This was attributed to the lower charge density of ST than that of QT, and to a loss of cationic properties at pH 9. FS performed better in terms of vanadium removal (pH 4: 86%, pH 7: 98%, pH 9: 100%) with lower coagulant doses, although effective turbidity removal required precise pH control. QT produced the largest flocs and the highest floc regrowth at pH 4 and 7. Under alkaline conditions, tannin coagulants exhibit no regrowth, which implies that a careful flocculation and floc separation step is needed. The natural organic matter fractionation results revealed that FS effectively removed hydrophilic carbon (76%) in a pH-controlled mine effluent better than tannin coagulants (QT: 12% and ST: 22%) from the pH 4 effluent; however, ST removed hydrophobic carbon entirely. All coagulants adequately removed humic substances, with FS being the most efficient (88%), followed by ST (53%) and QT (47%). X-ray photoelectron spectroscopy (XPS) analysis of jar test residues showed that some of the vanadium removed existed in the V(IV) oxidation state.

Evaluation of biosorbents as an alternative for mercury cyanide removal from aqueous solution

Worldwide, artisanal gold miners currently use and lose over 2000 t/year of mercury, which causes massive social and environmental problems. The combined use of mercury and cyanide by artisanal processing centers have exacerbated the bioavailability of the pollutant. Biosorbents have the capability to adsorb mercuric species in solution, and due their low cost and extensive availability close to mines, they can be used to detoxify effluents. In this study, four biosorbents were evaluated for mercury cyanide removal from simulated gold mining effluents: banana peel, passion fruit peel, eggshells, and chicken feathers. For each treatment, the adsorption capacity, equilibrium isotherms, and kinetic modeling were studied. Only banana peel showed favorable adsorption of Hg(CN)2, with a 94 % removal percentage within 90 min. The pseudo-first order model resulted in the same adsorption capacity as the experimental data (0.47 mg/g). The Sips isotherm model fitted the experimental data, indicating that the adsorption was monolayer-based. Banana peel was found to be more selective for mercury than for gold cyanide. Conversely, the excess of free cyanide had a negative effect on the adsorption efficiency.

Effect of chemical species and temperature on the stability of air nanobubbles

The colloidal stability of air nanobubbles (NBs) was studied at different temperatures (0–30 °C) and in the presence of sulfates, typically found in mining effluents, in a wide range of Na2SO4 concentrations (0.001 to 1 M), along with the effect of surfactants (sodium dodecyl sulfate), chloride salts (NaCl), and acid/base reagents at a pH range from 4 to 9. Using a nanobubble generator based on hydrodynamic cavitation, 1.2 × 108 bubbles/mL with a typical radius of 84.66 ± 7.88 nm were generated in deionized water. Multiple evidence is provided to prove their presence in suspension, including the Tyndall effect, dynamic light scattering, and nanoparticle size analysis. Zeta potential measurements revealed that NBs are negatively charged even after two months (from − 19.48 ± 1.89 to − 10.13 ± 1.71 mV), suggesting that their stability is due to the negative charge on their surface. NBs were found to be more stable in alkaline solutions compared to acidic ones. Further, low amounts of both chloride and sulfate dissolved salts led to a reduction of the size of NBs. However, when high amounts of dissolved salts are present, NBs are more likely to coalesce, and their size to be increased. Finally, the investigation of the stability of air NBs at low temperatures revealed a non-monotonic relationship between temperature and NBs upon considering water self-ionization and ion mobility. This research aims to open a new frontier towards the application of the highly innovative NBs technology on the treatment of mining, mineral, and metal processing effluents, which are challenging aqueous solutions containing chloride and sulfate species.

Shielding process for the effect of anions on uranium selective recovery and heavy metal removal from simulated mine effluents

The selective separation of uranium from uranium tailing wastewater is of great importance for environmental protection and nuclear energy development. The complexation of Cl−, SO42−, NO3–, and PO43− with UO22+ seriously hindered the achievement of this goal. Herein, a process for achieving it with the coexistence of anions and cations by shielding the influence of anions was designed. Thermodynamic calculations indicated that CO32– could enhance the retention of uranium in the solution by complexing with UO22+ and capturing UO22+ in UO2SO4 and UO2HPO4 to form water-soluble uranyl-carbonate. The capturing ability of CO32– was not diminished by the increase in anion concentration. And the electrochemical experiments revealed the high efficiency of uranium electrochemical extraction in the above system. In addition, the results showed that uranium could be separated from Co2+, Cd2+, and Ni2+ ions under the coexistence of Cl−, SO42−, NO3–, and PO43−, thus achieving the selective separation of uranium in the wastewater. And the retention ratio of impurity cations in the liquid phase after separation was less than 0.003. Overall, this method provides new insights into the selective separation of uranium and heavy metal removal in real uranium tailings wastewater.

(General Student Award Winner - 3rd Place) Electropolymerized Poly(3,4-ethylenedioxythiophene) Coatings on Porous Carbon Electrodes for Electrochemical Separation of Metals

Advances in decarbonization technologies such as batteries, photovoltaics, and wind turbines are accelerating the energy transition from fossil fuels to renewables. However, these technologies drive the demand for so called “critical metals” (e.g., Co, Ni, Li) that are unequally distributed over the planet and their mining has a significant environmental impact1. Electroplating and mining effluents can be utilized as a secondary source for these metals, but the low concentration of metals in their ionic form is a challenging medium for conventional separation methods2. Electrode-assisted separation methods where ions are immobilized on the electrode surface are well-suited for ionic separations as they can offer selectivity for the target metal ion with low energy consumption, minimal chemical input, and direct integration with the electrical grid3. These technologies can greatly benefit from the infrastructure of flow electrochemical platforms, including the use of porous carbonaceous electrodes to boost convective transport and minimize reactor resistances4. Imparting ion-selectivity on carbon electrodes is possible by immobilizing redox-active layers on their surface3. However, traditional coating techniques used to deposit functional materials (i.e., dip coating, spraying, doctor blading) cannot be realized on macroporous supports without compromising their microstructure. The use of conductive polymers can overcome this challenge as they can be coated on complex morphologies with controllable thickness through electropolymerization reactions, and they can provide a conductive and switchable matrix for ion-exchange. We hypothesize that the electrochemically switchable ion exchange (ESIX) property of conductive polymers, combined with the utility of macroporous carbon scaffolds can unlock convection enhanced and zero-gap reactor architectures for ionic separations.In this work, we investigate the electropolymerization of an industrially relevant polymer poly(3,4-ethylenedioxythiophene) (PEDOT) on commercial carbon fiber-based paper electrodes in terms of its synthetic parameters, morphology and ESIX-activity5. When coordinated to poly(4-styrenesulfonate) anions, PEDOT/PSS blend forms smooth and conformal layers on the carbon fibers with a controllable thickness down to 0.1 µm. We show that the PEDOT/PSS system acts as potential-controlled cation exchange material that can ingress Ni2+ at a low potential of -0.25 V (vs Ag/AgCl) and demonstrates higher affinity towards Ni2+ than Zn2+. The advantage of ESIX is that both adsorption and desorption are potential controlled. To verify this, we performed a complete ESIX-swing on PEDOT/PSS coatings with increasing coating weights and analyzed the desorbate for ion content (Figure 1). We find that by increasing the PEDOT/PSS coating weight, more Ni2+ can be separated from binary Ni2+:Na+ solutions, but the adsorption capacity decreases. The highest adsorption capacity of 227 mg g-1 is reached for the lowest coating weight, which suggests that thicker coatings are not well utilized within the time frame of the ESIX experiments. Although this work focuses on conductive polymers for electrochemical separation of metals, it can inform researchers on electropolymerization-based coatings for various electrochemical technologies (e.g., fuel cells, electrolyzers, redox flow batteries) that utilize porous electrodes. References T. Watari, K. Nansai, and K. Nakajima, Resources, Conservation and Recycling, 155, 104669 (2020).K. Kim et al., iScience, 24, 102374 (2021).X. Su, Current Opinion in Colloid & Interface Science, 46, 77–93 (2020).W. Tang et al., Water Research, 150, 225–251 (2019).E. B. Boz, M. Fritz, and A. Forner-Cuenca, submitted (2022). Figure 1

Biochars from modified sugarcane bagasse for manganese removal from mining effluents

Biochars from sugarcane bagasse (non-treated or pretreated with NaOH or H3PO4) were obtained at different pyrolysis temperatures (400 or 500 °C) and applied as adsorbents for removal of Mn(II) from aqueous solution. A detailed adsorption study of Mn(II) on the biochars was performed and mechanisms of Mn(II) removal were elucidated. The biochar with better adsorption performance was applied for Mn(II) removal from mining effluents. The pretreatment of biomass with NaOH and the lower pyrolysis temperature (400 °C) increased the number of basic oxygenated groups on the surface of adsorbent, favoring the Mn(II) adsorption. The biochar pretreated with base (up to 98% removal) was nearly twice more efficient for Mn(II) removal than that pretreated with acid. FTIR and XPS results showed that complexation between oxygenated groups and the metal is an important mechanism of adsorption. XRD and XPS results indicated the formation of MnO and cation exchange as other mechanisms for Mn removal. DFT calculations suggested that CO and C-OH groups on the biochar can favor a direct interaction between active carbons on BC surface and Mn(II). The biochar with best adsorption performance reached up to 65.8% of Mn(II) uptake from real mining effluent, showing the feasibility of using BC from sugarcane treated with NaOH to remove Mn from complex effluents. Practicality of employing the material was evaluated by reusability assays and cost estimations. Our findings point advance in the field of biochar application for Mn removal and reveal the importance of application of these materials in real conditions.

PHYTOREMEDIATION AND EXTRACTION OF COLLOIDAL CONTAMINANTS FROM MINE EFFLUENTS THROUGH LEGUME PLANTS

The bioaccumulation and environmental toxicity of colloidal contaminants have always been the focus of extensive research. Here we report efficient extraction of iron oxide colloidal contaminants from mine drainage effluents by phytoremediation with legume plants. The smallest fine particles with size less than 10 nm exhibit two wide absorption peaks at 350 and 495 nm, respectively. They have good dispersibility in aqueous environment and are highly resistant to removing or purification by any gravitational settings. The ultra-small nanosized particles (with average diameter 2-3 nm) can be bioaccumulated into the roots of soybean sprouts and might cause physiological stress and inhibition of the germination process. All experimental data found delayed growth, as well as decreased biomass production, which was observed in both the stem and root system of treated sprouts. Nevertheless, the immersed in mine effluent plants showed some resistance to the colloid toxicity. The light microscopic analysis also revealed the occurrence of more intensive symbiosis between the root tubers and the rhizosphere microbial communities in the case of phytorenmediation. The absorbance spectroscopic measurement demonstrated about 90 % efficient colloidal removement from the suspension within 10 days treatment. The atomic absorption spectroscopy analysis of mineralised sprouts cultured in synthetic mine effluents found that the highest concentration of accumulated iron in the legume plants was 258,02 ± 23,48 mg/100 g, which was achieved in suspension of 25 mM FeSO4. The presented report enables potential practical application of legume plants in the circumneutral passive treatment systems for remediation of mine effluents.

PVDF-co-HFP based anion exchange membrane for acid recovery from bentonite mine effluent via diffusion dialysis

PVDF-co-HFP based anion exchange membrane for acid recovery from bentonite mine effluent via diffusion dialysis

Минимизация опасности металлизированных шахтных стоков

Increase in ore production volumes and the use of large-sized equipment contribute to the loss of ores during mining, which gives rise to the phenomenon of natural leaching. On the example of deposits of the Sadon ore cluster, the hazard of metallized mine effluents for living matter and humans is shown. Of the relatively young methods of mine water purification, the most promising is the combination of electrochemical softening of mine effluents with electrodialysis desalination and concentration. The improvement of environmental protection technologies is developing on the basis of the managed disposal of mining and processing waste as a generator of natural leaching. The results are presented related to the experimental study of the parameters of metals extraction from the mine effluents by electrodialysis desalination with simultaneous concentration. The mechanism is formulated related to the development of oxidative processes of sulfide minerals in the presence of carbon dioxide of the mine atmosphere with the occurrence of electrochemical bonds between the crystals and mineral grains. The process of electromembrane treatment of metal-containing wastes is detailed. It is shown that during the electrochemical decomposition of salt systems, associated commercial products are formed. The dynamics of pollution of the Ardon river washing the Sadon deposit is given. The chemical processes of leaching of lost ores are described. An installation for electrochemical wastewater treatment is recommended, and a quantitative assessment of its efficiency is given. It is noted that the processes of electrochemical wastewater treatment are adequate, described by linear graphs and subject to correction. It is shown that the drains of mines are hazardous for living matter. It is indicated that the improvement of environmental protection technologies will be developed in the direction of waste disposal of mining and processing. The general principle of mine water hazard reduction is a combination of electrochemical softening with electrodialysis desalination and concentration.

Geogenic, Anthropogenic, and Authigenic Minerals Hosting Arsenic and Antimony in Yellowknife Bay Sediments

Abstract Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada) is a water body valued by surrounding communities for its subsistence, recreational, and cultural use. Located directly downstream of the former Giant Mine and Con Mine, Yellowknife Bay has received inputs from mine waste streams enriched in arsenic (As), antimony (Sb), and metals since the late 1930s. Lake sediments in Yellowknife Bay provide a record of metal(loid) contamination from aerially deposited roaster stack emissions, mine effluent, and Giant Mine tailings. A sediment sampling program was conducted in Yellowknife Bay to characterize As and Sb mineralogy using scanning electron microscopy-mineral liberation analysis. Mineralogical analysis of As- and Sb-hosted minerals in nine sediment cores suggests that arsenic trioxide (As2O3), originally deposited during the period of peak-mining emissions, has since been transformed into authigenic sulfides (interpreted to be realgar) down core from peak-mining emissions. Arsenic has also been attenuated by iron (Fe)-oxyhydroxides and roaster-generated iron oxides up-core from peak-mining emissions, near the sediment–water interface. The Sb-bearing minerals appear to be stable in Yellowknife Bay sediments, with no conclusive evidence of post-depositional mobility having been identified. The observed prevalence of arsenic trioxide in surface sediments proximal to Giant Mine suggests that As and Sb contamination is ongoing, likely from terrestrial weathering of contaminated soils and shoreline outcrops. Arsenic-bearing oxide minerals prevalent in surface sediments may become unstable should redox conditions in the hypolimnion change; prolonged anoxia could destabilize the As hosting minerals and release As to bottom waters. Therefore, long-term monitoring of the water column, including hypolimnion conditions, in Yellowknife Bay is recommended.

Changes of inorganic nitrogen compounds concentration in a mining enterprise wastewater by the microalgae Chlorella vulgaris

Wastewater contamination by nitrogen compounds is a serious problem for the mining, industrial and utility companies. Nitrogen can enter quarry effluent when explosives containing ammonium nitrate are used in blasting operations. This nitrogen pollution of water leads to environmental damage and human disease, companies that exceed the legal limits for nitrogen pollution are subject to fines. Nitrogen is removed from wastewater by biological methods, but their efficiency is low in the Northern regions of Russia due to climatic factors that hinder the vital activity of organisms. Therefore, it is essential to develop wastewater treatment technologies for the removal of nitrogen compounds. This study focuses on the ability of the microalgae Chlorella vulgaris to absorb and utilize various inorganic nitrogen compounds in mining effluents using the example of effluents from the "Karelsky Okatysh" mine and tailings dam (Kostomuksha, Republic of Karelia). Concentrations of ammonium, nitrate and nitrite in water and microalgal biomass in water samples have been investigated. A novelty of the study is the evaluation of pollutant concentrations in parallel experiments with different cultivation conditions. It has been found that when Chlorella vulgaris is cultivated at 26 °C, aeration and artificial light, the concentration of ammonium decreases. These results show the promising application of bioreactor technologies for the treatment of ammonium polluted wastewater.

Performance of ferrates for simultaneous removal of As and Mn from circumneutral contaminated mine water

Despite being efficient in removing (in)organic contaminants from effluents, ferrate (Fe(VI)) has scarcely been used for the removal of metal(loid)s from mine effluents. The present study evaluated the performance of wet vs. solid Fe(VI) to remove As(III) and Mn(II) from synthetic and surrogate neutral mine effluents. The experiments were done using single (SAs or SMn containing 3.5 mg As/L or 4.5 mg Mn/L, respectively) and binary (SAs+Mn containing 3.5 mg As/L and 4.5 mg Mn/L) synthetic effluents as well as surrogate mine effluents (Elow and Ehigh). Firstly, Fe(VI) type, optimal dose, adjusted pH (pHa), and retention time were assessed to evaluate their effect on the treatment of SAs and SMn. Then, the performance of Fe(VI)s, alone or combined with Fe(III), was tested for the removal of As and Mn from SAs+Mn. Lastly, the most performant conditions were applied to Elow and Ehigh; the toxicity to D. magna was evaluated before and after treatment. The results showed that at pHa of 5.5, Fe(VI)s efficiently removed As (> 98%) and Mn (> 97%) from SAs, SMn, and SAs+Mn within the first minute. The Fe(VI)s dose required had to be adjusted depending on the contaminant to be removed (SAs or SMn vs. SAs+Mn). The use of Fe(VI)s +Fe(III) showed improved removal efficiencies for As (99%) and Mn (> 99%), while requiring a lower Fe(VI) dose. Moreover, the Fe(VI) treatment of Ehigh, initially acutely toxic, entailed the elimination of D. magna toxicity. These findings provide new insights for the potential application of Fe(VI) in the removal of metal(loid)s from mine water.

Functionalization of thiosemicarbazide/gellan gum for the enhancement of cadmium removal from aqueous solutions – Grafting of tributyl phosphate derivative

Two sorbents are successfully synthesized based on the chemical modification of gellan gum (GG). First, thiosemicarbazide is grafted onto GG to produce GEG-C. In a second step, GEG-C is functionalized with a derivative of tributyl phosphate (dTBP, giving GEG-P sorbent). The sorption properties are compared for recovery of Cd(II) from aqueous solutions. GEG-C is expected to bind Cd(II) through carboxylic, amine, and thiocarbonyl groups, while phosphate groups in GEG-P contribute to increase metal sorption. The chemical modification improves not only the uptake kinetics (equilibrium time ≈30 min, vs. 45 min) but also the sorption capacities (≈2.79 vs. 1.60 mmol Cd g−1), at optimum pH (i.e., pH 5). The functionalization also improves (a) the sorbent stability (weaker reduction of the loss in sorption efficiency after five cycles of reuse compared with GEG-C) and (b) the sorption selectivity in the presence of competitor ions (from equimolar multicomponent solutions), especially at pH 4. Different sorption mechanisms may be involved depending on the pH (deprotonation of reactive groups) including chelation (onto deprotonated amine and phosphonate groups) and ion exchange (protonated groups with metal cations). Cadmium sorption is reversed by contact with 0.3 M HCl solution. The functionalization (GEG-P) strongly increases the selectivity coefficient for Cd(II) against major elements in mining effluent, especially at pH higher than 5. These results confirm the interest of multifunctionality in the development of new sorbents based on renewable resources (such as gellan gum).

Valorization potential of N-rich zeolite and moving bed biofilm reactor (MBBR) biomass in the revegetation of non-acid generating gold mine tailings

Treatment of ammonia nitrogen (NH3−N) in mine effluents generates N-rich residual materials, such as moving bed biofilm reactor (MBBR) biomass and spent zeolite. Using them as substitutes for mineral fertilizers in revegetation of mine tailings avoids disposal and contributes to a circular economy. The study evaluated the effect of MBBR biomass and N-rich zeolite amendments on above- and below-ground growth and foliar nutrient and trace element concentrations of a legume and several graminoid species grown on non-acid generating gold mine tailings. N-rich zeolite (clinoptilolite) was produced by treating saline (up to 60 mS/cm) synthetic and real mine effluents (250 vs 280 mg/L NH3-N). A three-month pot experiment was conducted with a dose of tested amendments equivalent to 100 kg/ha N and compared to unamended tailings (as negative control), tailings with a mineral NPK fertilizer, and a topsoil (as positive controls). Higher foliar N concentrations were found in amended and fertilized tailings vs negative control, but N was less available in the zeolite treatments than in other tailings treatments. For all plant species, the mean leaf area and above-ground, root, and total biomasses were similar in the zeolite-amended tailings to the unamended tailings, while the MBBR biomass amendment resulted in similar above- and below-ground growth to the NPK fertilized tailings and the commercial topsoil. Trace metal concentrations in water leaching from the amended tailings remained low, but tailings amended with zeolite exported NO3-N concentrations up to 10 times greater (>200 mg/L) after 28 days compared to all other treatments. Foliar Na concentrations in zeolite mixtures were six to nine times higher than in other treatments. The MBBR biomass is a promising potential amendment for revegetation of mine tailings. However, Se concentrations in plants after MBBR biomass amendment should not be underestimated, while Cr transfer from tailings to plants was observed.