Evaluating and Enhancing Iron Removal via Filterable Iron Precipitates Formation during Coal-Waste Bioleaching

Iron removal via jarosite precipitate formation is a commonly used technique in various hydrometallurgical processes. Excess iron removal often becomes essential to an overall metal recovery circuit. This is particularly important to processes involving iron-bearing minerals. A technique, which involved the use of pyrite to generate acid for leaching, for iron removal is critical to enabling the process. Iron removal using CaO or similar reagents is expensive and often results in lost product. In the present study, various compounds that facilitate jarosite formation, namely Na2SO4, NH4OH, KCl, and KOH, were utilized and their effect in precipitation was observed. Visual Minteq assisted simulations were run in order to evaluate favorable conditions for iron removal. Morphology and elemental composition of precipitates were analyzed using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, and the phase purity was identified using X-ray diffraction analysis.

Effect of Chloride Concentration on the Cytotoxicity, Bioavailability, and Bio-Reactivity of Copper and Silver in the Rainbow Trout Gut Cell Line (RTgutGC)

Chloride (Cl-) influences the bioavailability and toxicity of metals in fish, but the mechanisms by which it influences these processes is poorly understood. Here, we investigated the effect of chloride on the cytotoxicity, bioavailability (i.e., accumulation) and bio-reactivity (i.e., induction of mRNA levels of metal responsive genes) of copper (Cu) and silver (Ag) in the rainbow trout gut cell line (RTgutGC). Cells were exposed to metals in media with varying Cl- concentrations (0, 1, 5 and 146 mM). Metal speciation in exposure medium was analyzed using Visual MINTEQ software. Cytotoxicity of AgNO3 and CuSO4 was measured based on two endpoints: metabolic activity and membrane integrity. Cells were exposed to 500 nM of AgNO3 and CuSO4 for 24 hours in respective media to determine metal bioavailability and bioreactivity. Ag speciation changes from free ionic (Ag+) to neutral (AgCl), to negatively charged chloride complexes (AgCl2-, AgCl3-) with increasing Cl- concentration in exposure media whereas Cu speciation remains in two forms (Cu2+ and CuHPO4) across all media. Chloride does not affect Ag bioavailability but decreases metal toxicity and bio-reactivity. Cells exposed to Ag expressed significantly higher metallothionein mRNA levels in low Cl- media (0, 1, and 5 mM) than in high Cl- medium (146 mM). This suggests that chloride complexation reduces silver bio-reactivity and toxicity. Conversely, Cu bioavailability and toxicity were higher in the high chloride medium (146 mM) than in the low Cl- (0, 1, and 5 mM) media, supporting the hypothesis that Cu uptake may occur via a chloride dependent mechanism.

Lead Solubility in the Kırklareli Stream, Turkey

The research was conducted in the Kırklareli stream, which flows southwest through the city of the same name toward the village of Kavaklı. The aim of the study is to evaluate water analysis results and assess the potential that the European Union drinking water standard for lead can be achieved in the Kırklareli stream by reliance on the low solubility of lead phosphate minerals. The present study used Visual MINTEQ 3.1 for all water chemistry simulations. The European Union drinking water standard for lead, which is 10 μg L−1, is exceeded at least once and as many as three times at seven of the ten sites during the 2018 sampling season. Although the database solubility of hydroxypyromorphite is exceeded in most samples, it appears this may be the result of major ion substitutions in the hydroxypromorphite that forms in the Kırklareli stream which increases the effective solubility of lead in the stream.

Nghiên cứu ứng dụng tổ hợp hóa chất xử lý ô nhiễm nước hồ đô thị Hà Nội quy mô phòng thí nghiệm

Nghiên cứu tập trung vào đánh giá ảnh hưởng của tổ hợp hóa chất khi bổ sung vào nước hồ đô thị ở Hà Nội. Cụ thể là tỷ lệ hóa chất Ca(NO3)2/FeCl3, nồng độ của tổ hợp hóa chất canxi nitrat (Ca(NO3)2), sắt (III) clorua (FeCl3) và đồng (II) sunphat (CuSO4) (4‰) và thời gian xử lý. Đối tượng nghiên cứu là nước hồ Triều Khúc và các thí nghiệm được tiến hành trong điều kiện phòng thí nghiệm. Phần mềm VISUAL MINTEQ 3.1 được sử dụng để xác định sự có mặt của các ion chính khi hòa tan tổ hợp hóa chất vào trong nước. Các chỉ tiêu được đánh giá gồm có tổng chất rắn lơ lửng (TSS), độ đục, nhu cầu oxy hóa học (COD). Kết quả nghiên cứu cho thấy, hiệu suất c ải thiện chất lượng nước hồ đạt giá trị tối ưu khi cho tổ hợp hóa chất Ca(NO3)2/FeCl3 = 1:1 (v/v) tại nồng độ 0,5 M trong khoảng thời gian xử lý là 3 giờ. Trong điều kiện này, hiệu quả xử lý TSS, độ đục, COD lần lượt là ~ 77%, ~ 82%, và ~ 85%. Kết quả từ nghiên cứu này khẳng định rằng việc sử dụng tổ hợp hóa chất bao gồm Ca(NO3)2 và FeCl3 khi bổ sung CuSO4 (4‰) sẽ là giải pháp hiệu quả kiểm soát chất lượng nước hồ đô thị Hà Nội.

Effect of chelating agents on phytoxicity and bioaccumulation of heavy metals in vascular plants

In this work the effect of chelating agents ethylenediaminetetraacetate (EDTA) and nitrilotriacetate (NTA) on phytotoxicity and bioaccumulation of Cd and Co in tobacco plants (Nicotiana tabacum L.) hydroponically grown in diluted Hoagland media (HM) spiked with 109Cd and 60Co was studied. Speciation analysis using a program Visual MINTEQ showed, that the portion of bioavailable ionic Me2+ forms significantly decreased in the presence of EDTA or NTA in 25% HM for account of [Me-EDTA]2- or [Me-NTA]- complexes. We found that the equimolar addition of EDTA or NTA to 50 μmol/dm3 CdCl2 or CoCl2 in HM positively diminished phytotoxicity of Cd or Co on tobacco plants. Bioaccumulation of Cd by tobacco roots during 8 d cultivation was minimally affected in the presence of equimolar concentrations of EDTA or NTA to 10 μmol/dm3 CdCl2 in media. On the contrary, equimolar concentration of EDTA or NTA added into HM caused considerable decrease of Co uptake by tobacco roots. Cadmium showed higher mobility in conductive tissues of tobacco plants than cobalt and the transport ratio in the presence of EDTA or NTA increased 2-times or 3-times in comparison with control experiments (without addition of chelates), respectively. In the case of cobalt this effect was observed in a less extent. Obtained data suggest the possibilities and constraints in the use of chelating agents in phytoextraction technologies in term of phytotoxicity, uptake and translocation of metals in plant tissues.

Bioaccumulation and distribution of 137Cs in tobacco cultivated under hydroponic conditions

Potential of plants to uptake metals from soil solution can be successfully applied for removal of long-lived radionuclides such as radiostrontium 90Sr or radiocaesium 137Cs. This work deals with bioaccumulation of Cs in tobacco plants (Nicotiana tabacum L.) hydroponically grown in diluted Hoagland media (HM) spiked with 137CsCl. Speciation analysis using a program Visual MINTEQ showed, that more than 97% of caesium in HM occurred in the form of Cs+ ions. We found that bioaccumulation of Cs significantly decreased from the value 100% to the value 20% removing of Cs from media after 8 days cultivation of plants with increasing HM concentration. However, the concentration ratio (CR) [Cs]shoot : [Cs]root increased with increasing HM concentration from the value 0.10 to the value 0.85. Bioaccumulation of Cs by tobacco plants significantly decreased with increasing CsCl concentration in media from the value 95% found at concentration of CsCl 10 μmol/dm3 to the value 44% at concentration of CsCl 1 000 μmol/dm3. We did not found visual symptoms of Cs toxicity on plants after 8 days cultivation or significant differences in growth rate or transpiration activity at CsCl concentration up to 0.2 mM. However, at > 0.2 mM CsCl concentration the decrease of growth rate and necrosis of young leaves or die-back of leaves (> 2 mM CsCl) were observed. The CR ([Cs]shoot : [Cs]root) increased with increasing concentration of CsCl (10 – 1 000 μmol/dm3) in media from the value 0.10 to the value 0.40. The obtained data suggest that fast growing plant species with high biomass production like tobacco might be a suitable in phytoextraction or rhizofiltration technologies used for 137Cs removing from environment.

Thermodynamics Analysis and Removal of P in a P-(M)-H2O System

In order to efficiently remove phosphorus, thermodynamic equilibrium diagrams of the P-H2O system and P-M-H2O system (M stands for Fe, Al, Ca, Mg) were analyzed by software from Visual MINTEQ to identify the existence of phosphorus ions and metal ions as pH ranged from 1 to 14. The results showed that the phosphorus ions existed in the form of H3PO4, H2PO4−, HPO42−, and PO43−. Among them, H2PO4− and HPO42− were the main species in the acidic medium (99% at pH = 5) and alkaline medium (97.9% at pH = 10). In the P-Fe-H2O system ((P) = 0.01 mol/L, (Fe3+) = 0.01 mol/L), H2PO4− was transformed to FeHPO4+ at pH = 0–7 due to the existence of Fe3+ and then transformed to HPO42− at pH > 6 as the Fe3+ was mostly precipitated. In the P-Ca-H2O system ((P) = 0.01 mol/L, (Ca2+) = 0.015 mol/L), the main species in the acidic medium was CaH2PO4+ and HPO42−, and then transformed to CaPO4− at pH > 7. In the P-Mg-H2O system ((P) = 0.01 mol/L, (Mg2+) = 0.015 mol/L), the main species in the acidic medium was H2PO4− and then transformed to MgHPO4 at pH = 5–10, and finally transformed to MgPO4− as pH increased. The verification experiments (precipitation experiments) with single metal ions confirmed that the theoretical analysis could be used to guide the actual experiments.

Recovery and Enhanced Upgrading of Rare Earth Elements from Coal-Based Resources: Bioleaching and Precipitation

Rare earth elements (REEs) are of great importance to modern society and their reliable supply is a major concern of many industries that utilize them in metal alloys, semiconductors, electrical equipment, and defense equipment. REEs in the coal waste have been revealed to be an alternative resource for REEs production. In this study, the extraction, recovery, and upgrading of the REEs from coal waste has been realized with the bioleaching and precipitation processes. Reliable and sustainable acid and oxidant production from the oxidation of the pyrite with Acidithiobacillus ferrooxidans to generate acid for leaching were realized in this research. The acidified bioleaching solution was used to extract REEs from coal waste, with 13–14% yields for most REE elements (~72 h of leaching). However, recovery for longer duration tests was significant higher (varies from 40–60% for individual REEs). After extraction, precipitation and separation processes were designed with the aid of Visual Minteq calculations and modeling to concentrate the REEs. With the procedures designed in this research, a final REEs precipitate product containing 36.7% REEs was produced.

ГИДРОГЕОЛОГИЯ И ГИДРОГЕОХИМИЯ МЕСТОРОЖДЕНИЯ РАДОНОВЫХ ВОД «КАМЕНСКОЕ» (Г. НОВОСИБИРСК)

Актуальность исследования состоит в получении новых сведений о гидрогеологии и гидрогеохимии слабоизученных месторождений радоновых вод города Новосибирска на юге Западной Сибири. Новосибирск относится к числу тех немногих городов России, которые были заложены на гранитах – источнике эманации радона (222Rn). В геологическом отношении изучаемая территория приурочена к внутренней области крупного Новосибирского гранитоидного массива. Научных обобщений имеющегося фактического материала не проводилось. Цель: выявление особенностей гидрогеологического строения и гидрогеохимии месторождения радоновых вод «Каменское», изучение форм миграции химических элементов в водах и оценка степени их насыщения относительно ряда карбонатных, сульфатных и силикатных минералов. Методы. Отбор проб выполнялся в соответствии с общепринятыми методиками. Обобщение и анализ гидрогеохимических данных проводилось с применением программных средств Microsoft Excel, STATISTICA, SURFER, Grid Master. В среде программных комплексов Visual Minteq и WATEQ4f выполнены физико-химические расчеты форм миграции химических элементов в радоновых водах и степени их насыщения к ряду породообразующих минералов. Результаты: В гидрогеологическом разрезе месторождения радоновых вод «Каменское» геологоразведочными работами установлено два водоносных комплекса (сверху вниз): поровых вод четвертичных отложений и трещинно-жильных вод верхнепалеозойских гранитов. В условиях Центрального района города Новосибирска, где почти вся площадь поверхности покрыта асфальтом и занята под сооружения и инфильтрация атмосферных осадков осложнена, естественный режим питания подземных вод нарушен. Порово-пластовые воды четвертичных отложений, воды зоны региональной трещиноватости и трещинно-жильные воды верхнепалеозойских гранитов находятся в единой области смешения, на которую оказывают влияние процессы подтопления и антропогенного загрязнения. В этой связи в водоносном комплексе верхнепалеозойских гранитов выделяется две гидрогеохимической зоны: верхняя – воды зоны региональной трещиноватости в зоне подтопления в условиях антропогенного воздействия, и нижняя – трещинно-жильные минеральные радоновые воды. Минеральные радоновые трещинно-жильные воды гранитов, не подверженные антропогенному влиянию установлены в скв. 4п (интервал 73–74 м) и в скв. 16 на глубинах от 73 до 128 м. Они холодные собственно пресные HCO3 Na-Ca и HCO3 Na-Mg-Ca состава с величиной общей минерализации от 613,4 до 689,9 мг/дм3 с содержанием кремния 10,3–13,6 мг/дм3. Они характеризуются рН от нейтральных до слабощелочных (6,9–7,8), кислородно-азотным составом водорастворенных газов. Установленная активность 222Rn варьирует в диапазоне 1101–1570 Бк/дм3 (сильно радоновые воды по классификации Н.И. Толстихина); содержания: 238U от 5,6∙10–3 до 6,5∙10–3 мг/дм3 и 226Ra от 2,7∙10–9 до 1,8∙10–8 мг/дм3. С ростом общей минерализации радоновых вод доля простых катионных форм Mg2+, Ca2+, Na+, Sr2+, Ba2+ в растворе уменьшается, это связано с образованием труднорастворимых карбонатных и сульфатных соединений. В радоновых водах формы Fe(II) представлены в виде Fe2+, FeHCO3+, FeCO30. Fe(III) мигрирует в форме положительно заряженных гидроксокомплексов Fe(OH)2+ и нейтральных Fe(OH)30. Среди форм миграции марганца доминирует простой катион Mn2+ (43,71–99,99 %), остальные формы представлены MnHCO3+ (9,89–28,27 %), MnCO30 (0,01–37,39), еще в меньшей степени MnSO40 (0,20–2,25 %), MnCl+ (0,04–1,12 %) и MnOH+ (0,01–0,05 %). Химические формы миграции тяжелых металлов (никеля и меди) представлены в виде свободных катионов (Ni2+, Cu2+), гидрокарбонатных (NiHCO3–, CuHCO3–) и карбонатных (NiCO30, CuCO30) комплексов. Медь также мигрирует в нейтральной форме Cu(OH)20. Бериллий (1 класс опасности) мигрирует в форме гидроксокомплекса Be(OH)2. Установленные особенности геохимических типов вод, долевого распределения форм и коэффициентов водной миграции химических элементов выявили усложнение состава равновесных минералов от сидерита, ферригидрита и гриналита в поверхностных водах до их насыщения кальцитом, доломитом, магнезитом, родохрозитом и тальком в трещинно-жильных водах верхнепалеозойских гранитов. Формы миграции химических элементов обуславливают механизмы растворения/осаждения минеральных соединений.