Subsequent Leaching Research Articles

Effects of soil redistribution by tillage on subsequent transport of pesticide to subsurface drains.

Tillage operations will change the distribution in soil for any pesticide residues still present from earlier applications. This redistributive effect of tillage has been neglected in the study of pesticide leaching behavior. This study reviews the literature to characterize this redistributive effect for different tillage operations and uses a pesticide leaching model to investigate the impact of redistribution on pesticide transport to subsurface drains which is a significant input route to surface water bodies. Inversion ploughing moves the majority of any residues of pesticide present at or near the soil surface into the bottom two-thirds of the plough layer, whereas non-inversion ploughing has only a limited redistributive effect. Incorporating this redistributive effect into model simulations resulted in large changes (typically 5-10-fold difference) in both the maximum concentration and total mass of pesticide transported to drains over the winter following cultivation. More intense cultivation decreased subsequent leaching for relatively mobile compounds (Koc ≤1000 mL g-1 ), but increased it for strongly sorbed pesticides (Koc ≥2000 mL g-1 ). The redistributive effect of soil tillage on pesticide residues can have a large effect on subsequent transport to subsurface drains. This effect has been neglected in the literature. Field research is required to validate the model simulations presented here, and consideration should be given as to whether the effect needs to be included within risk assessment procedures. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Flotation assessment and adsorption mechanism of wulfenite with three anionic collectors

ABSTRACT Wulfenite is a useful mineral containing both lead and molybdenum. Although the Mo theoretical content of wulfenite is too low to meet the sales requirement, how to pre-concentrate the wulfenite more efficiently and economically becomes increasingly important for subsequent leaching process. Using sodium oleate (NaOL), benzohydroxamic acid (BHA) and sodium dodecyl sulfonate (SDS) as collector, the flotation behavior of wulfenite has been investigated by micro-flotation tests, and the adsorption capacity of the three collectors on wulfenite has been measured and listed as below: NaOL (pH = 9.5) > SDS (pH = 6.5) > BHA (pH = 7.5). According to the frontier orbital theory analysis, when the collector ions act on the {112} surface of wulfenite, the effective mass of NaOL is the lowest, followed by SDS and BHA. Moreover, the molecular dynamics simulation of the three collector ions on wulfenite {112} surface reveals that the two adjacent outermost molybdenum atoms of wulfenite have strong adsorption due to the fracture of the original Mo-O bonds and could easily react with the single-bond oxygen atom outside the polar groups of the three collectors. Comparing the adsorption energy, NaOL has the best adsorption performance to wulfenite {112} surface, during which the O-Mo1 distance and O-Mo2 distance are both below 2.5 Å. By associations of the simulation results with flotation tests, when the feed contains 0.14% Mo, using NaOL as collector, a rough molybdenum concentrate with molybdenum grade of 17.25% and molybdenum recovery of 86.32% has been obtained by conventional flotation tests, which provide theoretical guidance and practical evidence to promote the wulfenite flotation performance.

Mechanochemically assisted persulfate activation for the facile recovery of metals from spent lithium ion batteries

A novel mechanochemically assisted persulfate activation method was proposed in this study to enhance the leaching of valuable metals from lithium-ion batteries by combining ball-milling, advanced oxidation processes and sucrose reduction. By optimizing leaching parameters including temperature, pH, milling time and solid-to-liquid ratio, high leaching efficiencies of 97.1%, 94.0%, 87.6% and 93.8% can be achieved for Li, Ni, Co and Mn respectively. In the mechanochemical process, the breakage of covalent bonds in cathode material is facilitated by free radicals generated from zero valent iron activated ammonia persulfate as well as mechanochemical activation. To further explore the role of free radicals, the mechanism of ammonia persulfate activation by zero valent iron was elucidated, and SO4•- was identified as the dominant reactive oxygen species in the mechanochemical process. Meanwhile, the synergistic effect of mechanochemically driven crystal dissolution and sulfate radical facilitated bond cleavage was revealed by ab initio molecular dynamics simulation. Moreover, the released metal was reduced by sucrose to a lower valent state of high solubility to promote transfer to the aqueous phase during the subsequent leaching process with dilute sulfuric acid. In this work, the insight on the mechanism of mechanochemical processes strengthened by free radicals may provide an inspiration for the recovery of valuable metals from LIBs.

(Invited) Recycling and Upcycling Electrode Materials from Spent Lithium-Ion and Alkaline Batteries

Lithium-ion batteries (LIBs) and alkaline batteries have been widely used in electric vehicles and portable electronics, dominating the energy storage market for decades,[1] but their recycling/upcycling has lagged far behind. Re/up-cycling batteries is urgently needed because it can not only preserve raw materials such as Li, Co, Ni, Mn, Al, and Cu for LIBs as well as Zn, Mn, Fe for alkaline batteries but also reduce hazardous wastes towards the environment.[2] Despite previous efforts made on re/up-cycling LIBs and alkaline batteries, there remains an urgent demand for simple, economic, environmentally benign, and energy-saving approaches.For LIB recycling, the dominated recycling methods including pyrometallurgy and hydrometallurgy are destructive and criticized of high energy consumption, undesirable economic outputs, and water contamination. By contrast, non-destructive methods such as solid-state sintering[3] and hydrothermal treatment coupled with short annealing (HT-SA) [4-5]are more promising. However, these emerged direct recycling approaches are deficient at regenerating outdated cathode materials to meet current market need. As such, upcycling (i.e., upgraded regeneration of cathodes) through surface engineering (coating[6] and doping[7-9]) or bulk reconstruction[10] has been developed. In our work, we demonstrate one upcycling approach to regenerate LiCoO2 cathode through an improved HT-SA approach in which a coating layer is prepared accompanied with the regeneration process. The upcycled cathode material shows improved electrochemical performance surpassing the pristine electrode materials.For alkaline battery recycling, the major recycling still focuses on hydrometallurgy and pyrometallurgy. Hydrometallurgical processes generally follow different steps of pre-treatment and subsequent leaching and separation of different metals by electrolysis, extraction or precipitation.[11] Another approach for treating spent alkaline battery materials is upcycling towards other applications such as supercapacitors,[12] catalysis[13], micronutrient fertilizer,[14] Mn alloy fabrication.[14] In our work, for the first time, we directly upcycle both zinc anode and Mn-based cathode for their use in rechargeable Zn-MnO2 batteries by a simple yet efficient annealing procedure. Zn was regenerated in a reductive atmosphere and the regenerated Zn shows high Coulombic efficiency and long life in symmetric cells while the regenerated Mn-based cathode shows superior performance than fresh MnO2 with regards to capacity, rate, and life. Under optimized N/P ratio, the regenerated Zn and MnO2 was paired to make rechargeable Zn-MnO2 batteries delivering excellent performance, comparable or even superior to state-of-the-art Zn-MnO2 batteries. Reference [1] Li, M.; Lu, J.; Chen, Z.; Amine, K.Advanced Materials 2018, 30, 1800561.[2] Rarotra, S.; Sahu, S.; Kumar, P.; Kim, K.-H.; Tsang, Y. F.; Kumar, V.; Kumar, P.; Srinivasan, M.; Veksha, A.; Lisak, G. ChemistrySelect 2020, 5, 6182.[3] Fan, M.; Chang, X.; Guo, Y.-J.; Chen, W.-P.; Yin, Y.-X.; Yang, X.; Meng, Q.; Wan, L.-J.; Guo, Y.-G., Energy Environ. Sci. 2021, 14 (3), 1461-1468.[4] Xu, P.; Dai, Q.; Gao, H.; Liu, H.; Zhang, M.; Li, M.; Chen, Y.; An, K.; Meng, Y. S.; Liu, P.; Li, Y.; Spangenberger, J. S.; Gaines, L.; Lu, J.; Chen, Z., Joule 2020, 4 (12), 2609-2626.[5] Shi, Y.; Chen, G.; Liu, F.; Yue, X.; Chen, Z., ACS Energy Lett. 2018, 3 (7), 1683-1692.[6] Meng, X.; Cao, H.; Hao, J.; Ning, P.; Xu, G.; Sun, Z., ACS Sustain. Chem. Eng. 2018, 6 (5), 5797-5805.[7] Wu, J.; Lin, J.; Fan, E.; Chen, R.; Wu, F.; Li, L., ACS Appl. Energy Mater. 2021, 4 (3), 2607-2615.[8] Fan, X.; Tan, C.; Li, Y.; Chen, Z.; Li, Y.; Huang, Y.; Pan, Q.; Zheng, F.; Wang, H.; Li, Q. J. Hazard. Mater. 2021, 410, 124610.[9] Xu, B.; Dong, P.; Duan, J.; Wang, D.; Huang, X.; Zhang, Y., Ceram. Int. 2019, 45 (9), 11792-11801.[10] Gaines, L.; Dai, Q.; Vaughey, J. T.; Gillard, S. Recycling 2021, 6 (2).[11] Ferella, F.; De Michelis, I.; Vegliò, F. Journal of Power Sources 2008, 183, 805.[12] Farzana, R.; Hassan, K.; Sahajwalla, V.Scientific Reports 2019, 9, 8982.[13] Gallegos, M. V.; Falco, L. R.; Peluso, M. A.; Sambeth, J. E.; Thomas, H. J.Waste Management 2013, 33, 1483.[14] Hu, X.; Robles, A.; Vikström, T.; Väänänen, P.; Zackrisson, M.; Ye, G., Journal of Hazardous Materials 2021, 411, 124928.

Leaching of yttrium and europium from fluorescent lamp phosphor powder using nitric acid: kinetics and optimization

ABSTRACT Rare earth elements (REEs) are recognized as one of the most critical elements and considered essential for the development of sustainable energy technologies, lasers, electronics, alloys, catalysts, and other applications. In order to meet the increasing demand to ensure those essential usages, the supply of REEs is however limited from the primary sources. Recovery of REEs from secondary resources, such as discarded electrical and electronic equipment, referred to as electronic waste (e-waste) is consequently crucial. Fluorescent lamps among such wastes are of special concern due to the high quantity of REEs present in them. This article discusses a potential hydrometallurgical method for recovering REEs (yttrium and europium) from fluorescent lamp waste via nitric acid leaching. The effects of leaching factors including acid concentration and temperature were examined. To assist the leaching yields of those metals, the effect of alkaline fusion was specifically examined. The kinetics of both processes, direct- and alkaline fusion-assisted leaching were investigated based on the shrinking core model. In the case of direct leaching, the metal dissolution was controlled by surface chemical reaction with apparent activation energies of 43.9 and 48.1 kJ/mol for yttrium and europium, respectively, in the temperature range 303–333 K. Pretreatment, viz., the alkaline fusion changed the subsequent leaching mechanism to diffusion control with apparent activation energies of 7.4 and 9.5 kJ/mol for the respective metal in the same temperature range. Optimization of the alkaline fusion-assisted acid leaching process was undertaken by applying response surface methodology (RSM) based on the central composite design (CCD). Under the alkaline fusion conditions such as soda/fluorescent powder mass ratio of 0.65 g/g, temperature of 1223 K and reaction time of 7200 s followed by acid leaching (nitric acid concentration – 3.5 M, temperature-323 K, pulp density – 30 g/L and leaching duration – 1200 s), the leaching efficiencies of 92.6% and 99.5% for yttrium and europium, respectively, could be achieved.

Study on optimization and mechanism of mechanical activation process of titanium-bearing blast furnace slag

In the present work, the specific surface area (BET), X-ray diffraction analyses (XRD), scanning electron microscopy (SEM) energy-dispersive X-ray analysis (EDS), and laser particle size analysis were employed in the investigation of mechanical activation mechanism of titanium-bearing blast furnace slag. The results indicated that the specific surface area of the activated slag was significantly larger than that of the unactivated slag. The reduced intensity of the (121), (202), (123) and (242) diffraction peaks, which belong to the perovskite (CaTiO3), stems mainly from the increase in the lattice distortion and the decrease in the unit-cell volume. Compared with the unactivated slag, the cumulative volume of medium particles (1 μm ≤ PS ≤ 100 μm) in the activated titanium-bearing blast furnace slag was significantly higher, which was suitable for the subsequent leaching process. With the increase of ball-to-material mass ratio, mechanical activation time, mechanical activation rotation rate, the activated titanium-bearing blast furnace slag were extensively bonded and agglomerated. According to the results obtained by XRD, BET, SEM and laser particle size analysis, we concluded that the optimum mechanical activation process parameters are ball-to-material mass ratio of 20:1, activation time of 170 min, and activation rotation rate of 400 min/r, respectively. We also concluded that mechanical activation mechanism of titanium-bearing blast furnace slag can be attributed to the increase of specific surface area, amorphization of mineral particles, enhanced strain, preferential dissolution of select crystal faces, structural disorder, change of microtopography, leading to more amenable to leaching process.

Selective dissolution of zinc and lead from electric arc furnace dust via oxidative thermolysis with polyvinyl chloride and water-leaching process

Electric arc furnace dust (EAFD) is a troublesome metallurgical waste accumulated worldwide in large quantities. In this work, EAFD mixed with polyvinyl chloride (EPVC) was thermally treated at 300 °C under air flow followed by leaching of solid residue in water at pH 5.6 and a temperature of 50 °C. Three sample geometries of EPVC mixtures were considered for thermal treatment stage (loose powder, pelleted thin disks and long cylinder shapes). Oxidative thermal treatment of EPVC mixture has resulted in oxidation of magnetite into hematite and prevented iron chloride formation while both zinc and lead were completely chlorinated. The degree of magnetite oxidation was more pronounced when loose powder was used. The subsequent leaching of the thermal treatment of the loose powder EPVC has resulted in 100% recovery of zinc into leaching solution, while iron recovery was close to 0% at optimal conditions. When the EPVC mixture was pelletized into thin disk or cylindrical shape, the access of oxygen was hindered resulting in incomplete oxidation of magnetite or iron chloride to a non-leachable Fe2O3, which did not completely inhibit iron leaching. Iron recoveries in the post water leaching stage of EPVC residue treated under oxidative environment were found to be 21.6, 8.6 and 0.26% for long cylinder, thin disks, and loose powder, respectively. However, 46% of iron content was leached when a cylindrical shape mixture was thermally treated under inert conditions. These important findings can be utilized for the co-thermal treatment of EAFD and PVC wastes towards sustainable recycling of these wastes.

A Comparative Study of Extracting Vanadium from Vanadium Titano-Magnetite Ores: Calcium Salt Roasting Vs Sodium Salt Roasting

ABSTRACT In this study, a new vanadium extraction process from vanadium titano-magnetite(VTM) featuring calcification roasting and (NH4)2C2O4 solution leaching has been proposed. Compared with the traditional sodium roasting, the calcification roasting can avoid the production of waste gas and the sodium free tailings can be used for iron recovering by steel-making. However, the leaching rate of (NH4)2C2O4 was lower than that in sodium salt roasting-waterleaching. The reaction kinetics and mechanism of these two process were studied and compared in detail. It was found thatCaV2O6was formed during calcification and the porous structure of calcine facilitated the mass transfer. In the subsequent (NH4)2C2O4 leaching, theCaC2O4was formed and it would precipitate at the calcine particle surface and pores, which hindered the vanadium leaching. The leaching kinetics study showed that the diffusion through the solid product layer was the rate-determiningstep. Mechanical activation method was proposed to improve the leaching reaction kinetics in this work. It has been evident to be an effective method to intensify the leaching process. Under the optimal roasting and leaching conditions, the vanadium leaching rate could reach 81%, which was similar to that of the sodium salt roasting process. This is a promising alternative process for vanadium extraction from high grade VTM.

Microwave-assisted preparation of nanocluster rutile TiO2 from titanium slag by NaOH-KOH mixture activation

Rutile titanium dioxide is widely used in coatings, cosmetics, paper products, and other industries as the source of white inorganic pigment. The common preparation methods of rutile from titanium slag include the molten salt method, hydrochloric acid method, oxidation–reduction method, etc. In this paper, the NaOH-KOH sub-molten salt method was used to activate titanium slag. After a series of subsequent leaching processes and an attached roasting process with the assistance of microwave technology, a nanocluster was formed by nanorods with a diameter below 100 nm and a length below 500 nm. It is found that titanate changes to the stable metantitanate at a temperature of 80 °C in the process of acid leaching. Moreover, the relationship between the concentration of sub-molten salt, calcination temperature, and titanium leaching rate was analysed by kinetics. The results show that the leaching rate of titanium reached the peak when the mixed alkali concentration was 15 mol/L, and the leaching rate of titanium reached the maximum value when the roasting temperature was 450 °C. According to the Arrhenius equation, the activation energy of titanium slag in the NaOH-KOH sub-molten salt system was 130.8 kJ/mol. The pre-exponential factor was 5.44 × 10-4 m2/s, and a chemical reaction process controlled the whole process.

Impact of initial states on the vapor hydration of iodine-bearing borosilicate glass

Under the context of long-term geological disposal of nuclear waste glass, the present work investigates the effect of initial states on the glass chemical durability in the vapor phase and during subsequent leaching. Glass with different finishing steps of polishing and thermal annealing were prepared, vapor-hydrated, and aqueous-altered. Multiple characterizations of mechanical properties and structural modifications were performed to understand the reduction of vapor hydration rates with annealed glasses. Discussions on the degradation of mechanical properties provide insights to understanding the variations of glass chemical durability, which shows a feasible approach to link mechanical and chemical studies together. By looking into the release of boron in the vapor phase, similarities between glass vapor hydration and glass aqueous alteration at residual rate are noticed, which allow the proposition of mechanisms of boron release. Characterizations of the hydrated-then-altered glass reveal the transport-limiting property of the vapor hydrated layer.

Upgrade of titanium content in a vanadiferous titanomagnetite waste: Design of a roast-leach route based on thermodynamics simulations

Vanadiferous titanomagnetite deposits are a major resource for processes dedicated to vanadium extraction. Depending on the mineralogical characteristics and the developed unit operations, a titanium bearing waste is produced in mineral processing. The present manuscript deals with the development of an alternative to beneficiate this material to increase the titanium levels and, as consequence, conferring the material an improved composition that might have better acceptance on the market. It seems that a broad thermodynamics simulation regarding the typical roasting methods (e.g., based on sulfates, carbonates, and hydroxides) is scarce, the major contribution is on the development of a systematic approach for process design. The manuscript also covers experiments and a detailed characterization of the involved materials by means of Scanning Electron Microscopy as well as X-Ray Diffraction and Fluorescence. With the selection of NaOH as the most promising roasting reagent, with two subsequent leaching extractions, one in water and the other in acid medium; it was possible to concentrate Ti from 15.69 to 39.22 wt%, with perovskite (CaTiO3) as the main carrier of the element of interest, corresponding to 65.23 wt% of the resulting material mineralogical analysis.

The Optimization of Sc Recovery from Red Mud Obtained by Water-Leaching of Bauxite-Sintering Product

This study continues and develops approaching of bauxite residue treatment and associated waste for extracting highly valuable metals and scandium recovery by optimizing a hydrometallurgy method for process intensification. Laboratory-scale experiments were conducted in a nitric acid medium on electrostatic precipitator dust (ESPD) received in bauxite sintering. The method includes prior water-leaching of ESPD and subsequent asid leaching experiments at different liquid-to-solid ratios, leaching times and temperatures. The maximum extraction of the scandium was around 76.5 % at pH=0.2. Experimental design based on response surface methodology was used for obtained values optimization. Researches have shown that the optimization of the conditions for the transfer of scandium from red mud to the leaching solution mainly depends on the pH that have to be adjusted in range 0.5-1.7. The pH should not be too low, since Sc does not have time to go into solution in the presence of iron and other elements, as well as too high, because high values lead to re-precipitation of Sc from the filtrate. Complete study for Sc recovery is under progress and is not elaborated here.

In situ reduction of cathode material by organics and anode graphite without additive to recycle spent electric vehicle LiMn2O4 batteries

In a conventional roasting-sorting process to obtain cathode powders, the phase structure of LiMn2O4 is not dissociated and the valence of manganese is not changed, resulting in low metal recovery efficiency and high reagent cost in the subsequent leaching process. In this context, a novel process is developed to realize the recovery of spent LiMn2O4 lithium-ion batteries (LIBs) via one-step pyrolysis and reductant-free acid leaching. The leaching efficiencies of lithium and manganese are respectively 99.9% and 99.4% under the optimal pyrolysis conditions: a temperature of 500 °C, a nitrogen flow rate of 50 mL/min, and a pyrolysis time of 60 min. The analysis of thermogravimetry-infrared spectroscopy indicates volatilization of electrolyte and decomposition of LiPF6 occur in the temperature range of 100–180 °C. When the temperature rises from 180 to 800 °C, high molecular weight polymers (binder and separator) are degraded into pyrolytic gas and oil. LiMn2O4 is deconstructed and reduced to MnO and Li2CO3 under the synergistic effect of pyrolytic gas and anode graphite. The harmful fluorine and phosphorus are absorbed by Ca(OH)2 solution to avoid environmental hazards. The results suggest that the process integrated pyrolysis and aicd leaching is efficient, environmental-friendly, and low-cost for recycling spent LiMn2O4 LIBs.

Novel process for deep removal of chlorine and recycling of chlorinated tailings from titanium-bearing blast-furnace slag

Given the high chloride ion content in chlorinated tailings that harm the surrounding environment cannot be directly utilized, a new process for the deep removal of chloride ions from chlorinated tailings with additives was proposed. The products obtained included tailing slag, which can be used as a building material, and salt, which can be used in industry. Theoretical calculations and experiments were performed to determine the feasibility of the new process. The results showed that the chloride ions from the chlorinated tailings and sodium ions from the additives formed NaCl, which could be removed during water leaching. NaOH served as a better additive than sodium sulfate. An increase in the molar ratio and the prolongation of ball-milling was beneficial for the dechlorination of the water leaching residue. An increase in the roasting temperature leads to an increase in particle size, which worsens the kinetics of subsequent leaching and reduces the leaching rate. The developed process can obtain tailings with chloride ion content of less than 0.1%, which meets the standard for building materials applications. Meanwhile, NaCl with a purity greater than 99% could be obtained, preventing chloride ion pollution of water resources and the comprehensive utilization of chlorinated tailing.

Hydrometallurgical process development to recycle valuable metals from spent SCR deNOX catalyst

Spent catalyst, containing vanadium and tungsten oxide in a TiO2 glass fiber matrix, pose a risk of environmental contamination due to the high toxicity of its metal oxides if leached into the soil when disposed in landfills. Due to the increasing demand of metals and the continuous depletion of primary resources there is an growing necessity for recycling and reprocessing of spent catalysts and other secondary metal sources for environmental and economical reasons. Study of spent SCR catalyst soda roasting process with dissolved NaOH compared with the usual NaOH dry roasting and its influence in the subsequent water leaching. After optimization, the ideal parameters are roasting using a 0.4 ratio of NaOH/spent SCR catalyst in solution for 2 h at 973 K and de-ionized water leaching for 30 min, at 298 K with a pulp density of 30%. The research results show an important reduction of the roasting temperature and leaching time during the processing of spent SCR catalyst obtaining a 95.4% W and 80.2% V leaching efficiency liquor. Silicon compounds are one of the main impurities leached alongside the valuable metals and in this work, the silicon compounds leached are reduced significantly with the aim of avoiding the de-silication post-processing of the leach liquor. The main advantage of the proposed process is the increase of the leaching efficiency of vanadium and tungsten with a minimization of silicon impurities in a shorter time regardless of the leaching temperature.

Impact of temperature on the leaching of sulphate, Co, Fe, Mn, Ni and Zn from the Ballangen tailings deposit, Norway: a laboratory column experiment

Abstract Temperature is an important factor affecting the leaching of contaminants from waste deposits, especially in the Nordic region where temperature change is more drastic than other areas. In this study, the impact of temperature variation in the leaching of sulphate, Co, Fe, Mn, Ni and Zn from the Ballangen tailings deposit, northern Norway, was investigated using a column leaching experiment. Unoxidized tailings were fed into four columns, which were subsequently put into four wine fridges set at 5, 10, 14 and 18 °C, respectively. The columns were filled with 600 mL of deionized water from the top every second week. Leachate was collected at the bottom and tested for pH, conductivity and concentrations of , Co, Fe, Mn, Ni and Zn. The saturation index for ferrihydrite and the activity of Fe2+ in the leachate were calculated with PHREEQC. The results showed that the conductivity and leachate concentrations of , Co, Fe, Mn and Ni were highest at 14 and 18 °C, and lowest at 5 °C, which showed high tailings oxidation and subsequent leaching of contaminants at higher temperatures. X-ray photoelectron spectroscopic (XPS) analysis of the residual material confirmed the oxidation of sulphides and leaching of many elements. Ferrihydrite was supersaturated in the leachate from the 14 and 18 °C columns, which showed the oxidation of pyrrhotite and olivine and the precipitation of ferrihydrite. The cumulative mass of Zn leached out was highest at 10 °C, which might be the threshold temperature for the leaching of Zn.

Salt Dynamics and Budgeting in the Root Zone of Wheat under Irrigated Saline Environment

Plant growth is adversely affected by salt deposition in the root zone and requires judicious irrigation water management for enhancing productivity in an irrigated saline environment. To study the salt deposition and subsequent leaching of salts below the root zone of wheat, an experiment with four wheat cultivars (viz. three salt-tolerant KRL-210 (V), KRL-1-4 (V), and 12one salt non-tolerant HD- 2894 (V) were taken for the experiment under artificially prepared 4-1-1-1irrigation water with salinity levels of 4 dS m(S), 8 dS m(S) and 12 dS m(S) besides the 234-1varying salinity of the groundwater from 1.45 to 1.7 dS m(S) during rabiseasons of 2009-10 and 12010-11 at the research farm of Indian Agricultural Research Institute (IARI), New Delhi, India. -1 The soil salinity (EC) was 0.2 dS mbefore the conduction of the experiment during rabi 2009-1:2-1 10 and varied from 0.26 to 0.95 dS mduring rabi2010-11. The total salt-induced in soil was 70.15 -1-1 t haand 55.6 t hafor rabi2009-10 and 2010-11 respectively by saline irrigation water. The salt -1deposition in the crop root zone was observed at maximum (i.e., 17.04 and 22.97 t ha during rabi2009-10 and 2010-11, respectively) for Streated plots and minimum in Streatment levels. 41The production functions for wheat varieties were developed and the coefficient of 2determination (R) was 0.98 to 0.99 and 0.94 for salt-tolerant and salt non-tolerant varieties, respectively. Moreover, it was also estimated that the maximum salt was deposited on the top soil layer (15cm) and the leaching of salts from S, S, Sand Streatments levels was 65%, 63%, 123,452%, and 48% salts, respectively from the root zone. However, this study would assist in the computation of leaching requirements for enhancing productivity in irrigated saline environments.

Electrically controlled transdermal delivery of naproxen and indomethacin from porous cis-1,4-polyisoprene matrix.

This study is focused on the inquiry of using a porous polymeric structure to absorb and release transdermally two drugs through a skin from deproteinized natural rubber latex (DPNR). The porous DPNR films were fabricated from the internal formation of surfactant micelles and their subsequent leaching out to generate porous structures. The pore size of DPNR films increased with increasing surfactant amount. The model drugs were naproxen and indomethacin; their releases and release-permeations were investigated under the effects of surfactant amount, electrical potential, and drug size. Without electric field, the drug release mechanism was mainly driven by concentration gradient. The higher amount of drug released was obtained from the matrix with a larger pore size. Under electric field, the higher amounts of drug release were obtained in the shorter drug release durations, via the electrorepulsive force between the negatively charged drugs and the cathode electrode. The molecular drug size was a factor for the drug absorption, release rate and amount. For the drug release-permeation experiment through the pig skin, there were two release-permeation periods as governed by the combination of concentration gradient and swelling in the first period, and the matrix erosion in the second period. The fabricated porous DPNR films have been shown here to be potential to be used as a transdermal patch with electrically controllable drug release rate, amount and duration along with the facile drug-matrix loading and absorption.

Effect of Initial Cell Concentration on Bio-Oxidation of Pyrite before Gold Cyanidation

Bio-oxidation of refractory sulfidic gold minerals has been applied at the commercial scale as a pre-treatment to improve gold yields and reduce chemical consumption during gold cyanidation. In this study, the effect of initial cell concentration on the oxidation of pyritic gold ore was evaluated with four aerated bioreactors at 30 °C with 10% pulp density and pH maintained at 1.4 with NaOH. Results of NaOH consumption and changes in soluble Fe and S concentrations indicated that increasing the initial cell concentration from 2.3 × 107 to 2.3 × 1010 cells mL−1 enhanced pyrite oxidation during the first week. However, by day 18 the reactor with the lowest initial cell concentration showed profound performance enhancement based on soluble Fe and S concentrations, sulfide-S and pyrite contents in the residues, and subsequent gold leaching of the bio-oxidation residues by cyanidation. Overall, the results showed that the cell concentration was clearly beneficial during the initial stages of oxidation (first 7–8 days).

Improvement of the ore mining and processing technology for the Tyrnyauz deposit

The article presents a new development option for the combined technology for the mining and processing of tungsten-molybdenum ores of the Tyrnyauz deposit, based on the differentiation of intrablock reserves by flows using the creative concept of lump sorting, which takes into account the structure of the deposit’s residual reserves. In this setup, lump sorting both solves the problem of preliminary concentration and stabilizes the flotation ore feed in terms of the strength properties and the predominant texture of the ore minerals. In addition, lump separation ensures that a second rock mass flow is formed and directed for the backfilling of mined-out areas and subsequent leaching. At the Tyrnyauz deposit of tungsten-molybdenum ores, a change in the concept of lump separation enabled new technology development options based on simpler and more reliable technical facilities and hardware systems. In particular, the use of a narrow spectrum of ultraviolet radiation instead of X-ray radiation to excite scheelite luminescence creates an easily registered interval of values for the luminescence signal of the valuable component. This eliminates the need for fine tuning of the systems and enables simpler and more reliable control of the separation process. The separation allows adjusting the quality of the process streams over a wide range and increasing the concentrate output without prejudice to the recovery rates through the use of pre-processed, higher-grade mineral raw materials. Streamlined flow ratios within the combined technology are regulated by the number of blocks at the stages of stoping and backfilling of the mined-out areas.