Thermodynamic-guided ammonium-magnesium precipitation for simultaneous removal of phosphorus and silicon from vanadium slag leachate

The aim of this work is to summarize the results of using various reagents for the comprehensive removal of impurities from molten cast iron. A comparative analysis of the effectiveness of different reagents for cast iron refining was conducted. The use of soda slag as a reagent was tested at the industrial level in a 140-ton hot metal ladle, and the results of experimental treatments were presented. A technology for comprehensive cast iron refining using the CaO-FeO-Na2CO3 reagent system was considered, which is based on the interaction of these components with molten cast iron. Possible chemical transformations occurring during the introduction of these reagents were described, including desulfurization reactions, oxidation, and the removal of harmful impurities. Based on laboratory studies using a "hot" model, an analysis of impurity behavior was conducted, and influence maps of the reagents' components on phosphorus, sulfur, and silicon removal were constructed. Additionally, ternary phase diagrams for the CaO-FeO-Na2CO3 system were developed, which helped to determine optimal conditions for comprehensive cast iron refining. The results of an industrial test of soda ash as a reagent for complex cast iron refining confirmed that this material is effective for the simultaneous removal of sulfur, silicon and phosphorus under certain conditions. Laboratory and industrial studies have shown that a multi-stage impurity removal process during the out-of-furnace cast iron treatment — oxygen converter shop process link is an effective approach for comprehensive cast iron refining. In particular, at the out-of-furnace treatment stage, effective sulfur removal is achieved by using desulphurization reagents, followed by additional silicon and phosphorus removal at the BOF stage. The use of sodium carbonate (Na2CO3) in combination with other reagents such as CaO and FeO has shown significant potential for complex cast iron refining. The combinations of these components have demonstrated high efficiency in removing both sulfur and phosphorus, which allows optimizing the technological process of cast iron refining. Other reagents or technological solutions may be required to achieve a higher degree of silicon removal at the out-of-furnace iron treatment stage. The analysis of the behavior of impurities and chemical reactions during the treatment process shows that the introduction of additional reducing agents, such as aluminum, can help reduce the negative impact of CO2 and increase the efficiency of impurity removal. The constructed mapping and state diagrams demonstrated that changing the proportions of the components of the CaO-FeO-Na2CO3 system allows achieving different degrees of sulfur, silicon, and phosphorus removal, which makes it possible to select the optimal composition of the refining mixture for each specific case. The research results show that the CaO-FeO-Na2CO3-Al mixture is suitable for complex cast iron refining under laboratory test conditions and can be effectively used for the simultaneous removal of several harmful impurities. Increasing the amount of aluminum leads to a deterioration in refining performance from silicon and phosphorus.

Simultaneous phosphorus removal and sludge reduction in continuous-flow reactor with granules under long sludge retention time

Simultaneous removal of phosphorus, zinc, and lead from oligotrophic ecosystem by iron-driven denitrification: Performance and mechanisms

The feasibility of using magnetic ion exchange (MIEX) treatment, in-line alum coagulation, and low-pressure membrane filtration was investigated for the simultaneous removal of total phosphorus (TP) and effluent organic matter (EfOM) from biologically treated wastewater. The focus was also placed on minimizing fouling of polyvinylidene fluoride and polyethersulfone membranes, which are the most commonly used low-pressure membranes in new and retrofit wastewater treatment plants. MIEX alone was effective for the removal of EfOM, and MIEX plus a small alum dose was very effective in removing both EfOM and TP. MIEX removed phosphorus, but organic acids in EfOM were preferentially removed, and the effects of competing anions on the removal of EfOM were insignificant. All the pretreatment strategies decreased the resistance to filtration. The greatest decrease in fouling was achieved by using MIEX (15 mL L−1) plus a very low dose of alum (∼0.5 mg Al L−1). Sweep floc coagulation using alum and without MIEX also significantly decreased fouling but did not effectively remove EfOM and produced high floc volume that could be problematic for inside-out hollow-fibre modules. The addition of these reagents into rapid mix followed by membrane filtration would provide operational simplicity and could be easily retrofitted at existing membrane filtration facilities.

The aim of the research is to find ways to improve the technology of the iron preparing for the oxygen-converter smelting. This development will help to increase the competitiveness of Ukrainian plants’ metal products.Methodology. During the research, the analysis of iron refining technologies, which are used at metallurgical plants of Japan, the USA, Western Europe and Ukraine, was provided. The main factors, which largely determine the low competitiveness of metal products in Ukraine, have been established. It is shown that in order to increase the steel production’s efficiency, it is necessary to develop an energy-efficient one-stage technology for preparation of iron for converter smelting. It could be done by the preliminary refining of iron with the removal of silicon and sulfur from it in a casting ladle.Results. The research of one-stage preliminary complex processing of iron made it possible to determine that in this variant of iron processing, desiliconization of the melt is ensured in the reaction zone of the oxygen-fuel stream action. The stream carries powdered dolomitized lime in suspension. The process is accompanied by the emission of heat and intense slagging of CaO particles. It ensures the formation of floating drops of synthetic slag, which is close to the CaO – SiO2 – Al2O3 – MgO system with a reduced oxidation potential. At the same time, the desulfurization of iron is proceeded in the bubbling zone through the interaction of sulfur with floating drops of synthetic slag, which have a high absorption capacity for sulfides. The formation of the main cover slag is also ensured in order to intensify the desulfurization process. The formation of the main cover slag reduces the losses of iron in the form of beads during slag downloading and increases the temperature of iron during its processing.Scientific novelty. The scientific substantiation of research is provided. The subject of the final research is the mechanism and kinetics of the process of simultaneous desiliconization and desulfurization of iron . A new energy-saving technology for iron refining in a casting ladle with simultaneous removal of silicon and sulfur in the combined reaction zone is proposed. This reaction zone is formed by the blowing powdered lime dolomite into the melt through a submersible lance in oxygen-fuel streams. One of the features of such technology is preliminary feeding of pig or rod aluminum into the metal.Practical use. An improved technology of one-stage preliminary complex processing of iron in casting ladles with simultaneous removal of silicon and sulfur is proposed. This technology will significantly reduce the loss of iron and heat with the loaded slag during processing. As a result of this technology’s implementation, the percentage of silicon and sulfur in iron will be reduced to the level of 0.15 – 0.30 % and 0.005 – 0.010 %, respectively, without heat loss. The use of such iron in the production of oxygen-converter steel will reduce the consumption of lime for smelting. It also will reduce the loss of metal with a smaller amount of slag. The use of such iron will aslo reduce the specific consumption of iron.

Simultaneous aerobic removal of phosphorus and nitrogen by a novel salt-tolerant phosphate-accumulating organism and the application potential in treatment of domestic sewage and aquaculture sewage

At the end of 2014, a Major Baltic Inflow (MBI) brought oxygenated, salty water into the Baltic proper and reached the long-term anoxic Eastern Gotland Basin (EGB) by March 2015. In July 2015, we measured benthic fluxes of phosphorus (P), nitrogen (N) and silicon (Si) nutrients and dissolved inorganic carbon (DIC) in situ using an autonomous benthic lander at deep sites (170-210 m) in the EGB, where the bottom water oxygen concentration was 30-45 μM. The same in situ methodology was used to measure benthic fluxes at the same sites in 2008-2010, but then under anoxic conditions. The high efflux of phosphate under anoxic conditions became lower upon oxygenation, and turned into an influx in about 50% of the flux measurements. The C:P and N:P ratios of the benthic solute flux changed from clearly below the Redfield ratio (on average about 70 and 3-4, respectively) under anoxia to approaching or being well above the Redfield ratio upon oxygenation. These observations demonstrate retention of P in newly oxygenated sediments. We found no significant effect of oxygenation on the benthic ammonium, silicate and DIC flux. We also measured benthic denitrification, anammox, and dissimilatory nitrate reduction to ammonium (DNRA) rates at the same sites using isotope-pairing techniques. The bottom water of the long-term anoxic EGB contained less than 0.5 μM nitrate in 2008-2010, but the oxygenation event created bottom water nitrate concentrations of about 10 μM in July 2015 and the benthic flux of nitrate was consistently directed into the sediment. Nitrate reduction to both dinitrogen gas (denitrification) and ammonium (DNRA) was initiated in the newly oxygenated sediments, while anammox activity was negligible. We estimated the influence of this oxygenation event on the magnitudes of the integrated benthic P flux (the internal P load) and the fixed N removal through benthic and pelagic denitrification by comparing with a hypothetical scenario without the MBI. Our calculations suggest that the oxygenation triggered by the MBI in July 2015, extrapolated to the basin-wide scale of the Baltic proper, decreased the internal P load by 23% and increased the total (benthic plus pelagic) denitrification by 18%.

This study builds on our prior research to refine the methodology for estimating marine primary production (PP) in the Barents Sea. It examines how abiotic factors—vertical mixing and horizontal advection—affect nutrient concentrations in the euphotic zone and subsequently influence PP. The analysis utilized salinity and nutrient data from the World Ocean Atlas (NCEI WOA). The δ18O parameter, used in conjunction with salinity, helped quantify the proportion of water from different origins. The results revealed a spatial heterogeneity in nutrient transport, identifying zones of both synchronous and asynchronous nutrient flows. Asynchronous flow was characterized by the removal of phosphorus and silicon alongside the influx of nitrogen. A significant correlation between these physical fluxes and PP was observed in the eastern part of the sea, where asynchronous flow prevails. Our calculations indicate that nitrogen influx increases PP by an average of 38% as high as 68%. The simultaneous fluxes of silicon and phosphorus showed no statistically significant effect. The study concludes that nitrogen is the primary limiting factor for PP in this region.

The technological development for efficient nutrient removal from liquid dairy manure is critical to a sustainable dairy industry. A nutrient removal process using a two-step fed sequencing batch reactor (SBR) system was developed in this study to achieve the applicability of simultaneous removal of phosphorus, nitrogen, and chemical oxygen demand from anaerobically digested liquid dairy manure (ADLDM). Three operating parameters, namely anaerobic time:aerobic time (min), anaerobic DO:aerobic DO (mg L-1), and hydraulic retention time (days), were systematically investigated and optimized using the Taguchi method and grey relational analysis for maximum removal efficiencies of total phosphorus (TP), ortho-phosphate (OP), ammonia-nitrogen (NH3-N), total nitrogen (TN), and chemical oxygen demand (COD) simultaneously. The results demonstrated that the optimal mean removal efficiencies of 91.21%, 92.63%, 91.82%, 88.61%, and 90.21% were achieved for TP, OP, NH3-N, TN, and COD at operating conditions, i.e., anaerobic:aerobic time of 90:90 min, anaerobic DO:aerobic DO of 0.4:2.4 mg L-1, and HRT of 3 days. Based on analysis of variance, the percentage contributions of these operating parameters towards the mean removal efficiencies of TP and COD were ranked in the order of anaerobic DO:aerobic DO > HRT > anaerobic time:aerobic time, while HRT was the most influential parameter for the mean removal efficiencies of OP, NH3-N, and TN followed by anaerobic time:aerobic time and anaerobic DO:aerobic DO. The optimal conditions obtained in this study are beneficial to the development of pilot and full-scale systems for simultaneous biological removal of phosphorus, nitrogen, and COD from ADLDM.

Simultaneous phosphorus removal and adsorbents recovery with Ca-PAC assisted adsorption dynamic membrane system: Removal performance and influencing factors

The aim of the work is the development of a new technology of combined purging of the converter bath with oxygen and neutral gas, which allows to achieve a significant resource and energy saving effect. The proposed technological scheme of combined purging is based on the use of a new design of a three-tiered tuyere and a system for supplying two regulated oxygen flows to it. It is possible to completely replace oxygen with nitrogen at certain periods of melting, which allows us to significantly expand the technological capabilities of the combined purge of the converter bath. The design of a three-tiered tuyere, which eliminates the disadvantages of two-tier blowing devices, was carried out using high-temperature modeling. Processing of the materials obtained in the course of the conducted melts allowed us to obtain new information about the features of the physicochemical processes developing during the flushing of the converter bath with the afterburning of the exhaust gases. The features of the effect of oxygen jets on the removal of carbon, manganese, silicon and phosphorus from the melt are established. Based on the data of high-temperature modeling of the purge of the converter bath, the established methodology for calculating the main design parameters and experience in developing industrial structures of multi-tiered tuyeres, a three-tiered tuyere of the new design and a combined bath of oxygen and neutral gas for the 160-ton converters have been developed and proposed for industrial development . The practical implementation of the presented solutions will provide an increase in the technological and technical-economic indicators of smelting in comparison with the use of well-known developments in this field.

It is widely accepted that understanding the kinetics of steelmaking is a complex task, and reliable and validated kinetics models are required for developing successful steelmaking process models. Therefore, as an initial attempt, this paper analyses the applicability of first order kinetics to explain the steelmaking reaction kinetics using the published data in the IMproving Phosphorus Refining research report. The process data for 20 heats in a 6 tonne pilot plant were analysed for the removal of carbon, silicon, manganese and phosphorus using first order kinetics with static and dynamic equilibrium conditions. It was observed that the removal behaviour of silicon closely followed a first order kinetics relationship, while that of carbon only approximately followed a first order kinetics relationship. The removal of manganese did not show a good degree of fit with first order kinetics using static equilibrium condition, but a clear improvement was observed when calculated using dynamic equilibrium condition. In contrast, the kinetics of phosphorus oxidation did not follow any first order relationship.

An optimized CaO2-functionalized alginate bead for simultaneous and efficient removal of phosphorous and harmful cyanobacteria

In this study, the effectiveness of a novel adsorbent/precipitant containing powdered activated carbon (PAC) and poly aluminum chloride (PACl) was evaluated for the simultaneous removal of organic micropollutants (OMP) and phosphorus. Results showed better performance with the prototype suspension at similar PAC/DOC doses, possibly due to changes in surface chemistry caused by PAC's suspension in the acid precipitant. Further lab tests with wastewater treatment plant (WWTP) effluent samples confirmed the prototype's effectiveness for different matrices. They highlighted the need for optimizing PAC content based on the total phosphorus and DOC content of the wastewater to use both PAC and PACl most efficiently. Full-scale testing at a specific PAC/DOC ratio of 2 over one month demonstrated the prototype's suitability for simultaneous phosphorus and OMP removal under real WWTP conditions. OMP removal increased by > 90 % for carbamazepine, > 50 % for diclofenac and metoprolol, and 30 % for benzotriazole; overall, > 80 % elimination was achieved for all investigated proxy substances. The full-scale experience confirmed that the prototype is easier to store and to apply. It can be immediately used in existing P-dosing systems without additional investment costs, making it advantageous over other OMP removal technologies.

The developed Anaerobic/Intermittent aerobic-Magnetic Activated Sludge (AI-MAS) process was found suitable for the continuous removal of phosphorus, nitrogen and organic compounds simultaneously from wastewater. This AI-MAS process reactor consisted of a small anaerobic compartment (first stage) placed at the corner of the intermittent aeration tank (second stage) with a magnetic separator in the middle. Better sludge separation was observed at 1-6 rpm of the magnetic drum. Using AI-MAS process, continuous removal of about 90% T-P, 96% T-N and 94% soluble CODCr were achieved with the loading rate of 3.5 mg/l T-P, 16 mg/l T-N and 250 mg/l CODCr, for the period of 160 d at the rate of 6 hrs hydraulic retention time (HRT). Simultaneous removal of phosphorus and nitrogen from the wastewater was possible due to coexistence of both phosphorus and nitrogen removal bacteria within the same sludge biomass. Phosphorus removal was performed through phosphate accumulation in aerobic condition and released again in anaerobic condition with the concomitant uptake of organic substances. Nitrification and denitrification occurred simultaneously in non-aeration/aeration (NA/A) cycle of the intermittent aeration. Plant Tissue Cult. & Biotech. 32(1): 21-29, 2022 (June)