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* Microbes enhance denitrification under varying DO concentrations and SIF dosages. * Abiotic nitrate reduction rates are proportional to SIF age and dosage. * Over 80% of the simultaneously loaded NO 3 −-N and PO 4 3 − is removed biologically. This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings (SIF) are used as electron donors and adsorbents in low C/N ratio waters. Batch studies were conducted in abiotic and biotic reactors containing fresh and aged SIF under different dissolved oxygen concentrations with NO 3 −-N and/or PO 4 3 - influent(s) and their nitrate/phosphate removal and by-product formations were studied. Batch reactors were seeded with a homogenized mixed microbial inoculum procured from natural sludges which were enriched over 6 months under denitrifying conditions in the presence of SIF. Results indicated that when influent containing 40 mg/L of NO 3 −-N was treated with 5 g SIF, 79.9% nitrate reduction was observed in 8 days abiotically and 100% removal was accomplished in 20 days when the reactor was seeded. Both abiotic and seeded reactors removed more than 92% PO 4 3 − under high DO conditions in 12 days. Abiotic and biochemical removal of NO 3 −-N and abiotic removal of PO 4 3 − were higher under independent NO 3 −-N/PO 4 3 − loading, while 99% PO 4 3 - was removed biochemically under combined NO 3 −-N and PO 4 3 − loading. This study furthers the understandings of nitrate and phosphate removal in Zero Valent Iron (ZVI) assisted mixed microbial systems to encourage the application of SIF-supported bio-chemical processes in the simultaneous removals of these pollutants.

Concerning water resources, several ordinances and legislation determine standards and conditions for the discharge of effluents into water bodies. However, several contaminants are not covered by these guidelines due to little knowledge of their long-term effects and because they are found in low concentrations. These contaminants are called emergent and this category includes drugs, such as anti-inflammatory drugs. The electrocoagulation process associated with advanced oxidation comes up as an alternative to conventional effluent treatment processes, and the objective of this study was to evaluate this process using scrap iron as sacrificial electrodes in the treatment of synthetic effluents containing ibuprofen. High-performance liquid chromatography was used to quantify the drug in synthetic effluents. The Central Rotational Composite Design 2 4 was used in an experimental design, considering independent variables the concentration of contaminants, applied current, the concentration of the primary oxidizing agent H 2 O 2 , and the reaction time. The optimized conditions determined by statistical analysis were drug concentration of 5 mg L −1 , H 2 O 2 concentration of 200 mg L −1 , current of 5 A, and 150 min. The removals obtained under these conditions were higher than 92% in the aqueous phase, showing that electrocoagulation peroxidation technique has the potential to treat contaminants such as drugs present in effluents and waters.

Floating treatment wetland (FTW) in restoration of low C/N ratio wastewater was deemed to a frequently used method. However, the nitrate removal performance in floating beds was limited due to insufficient organic carbon sources. Iron scraps as a potential electron donor was beneficial to the NO 3 - -N reduction. To research the removal performance and mechanism of denitrification in FTW with iron scraps, FTW with Iris pseudacorus was built, and iron scraps were added as an electron donor to improve nitrogen removal efficiency. The batch experimental results demonstrated that the proper mass ratio of iron scraps to NO 3 - -N was 500:1. With iron scraps, the NO 3 - -N removal efficiency of FTW and control system increased significantly to 98.04% and 44.42% respectively in 2 weeks, while there was no obvious influence on the removal of NH 4 + -N. After adding iron scraps, the proportion of bacteria in the systems related to iron cycle and the relative abundance of nitrifying and denitrifying bacteria have increased obviously. By calculating the nitrogen balance, nitrogen reduction via plant uptake accounted for 8.79%, and the microbial denitrification was the main nitrogen removal pathway in FTW. Graphical abstract

Constructed wetland (CW), an ecological wastewater treatment technology, is low cost and easily to operate. Vertical flow constructed wetland (VF-CW) systems have been used to treat various wastewaters across the world. The present work exhibits the detail study of five type’s multi-layered vertically constructed wetlands operated at 24 h hydraulic retention time under semi-continuous vertical flow mode. Except N-NO 3 − , all the pollutants were sufficient removal in iron scraps constructed wetland (ISs-CW). The highest average pollutant removal efficiency achieved in ISs-CW was 85.04%, 77.57%, 85.99%, 62.01% and 88.91% for N-NH 4 + , N-NO 2 + , total nitrogen, total phosphate and sulphate respectively. The present CWs planted with Eichhornia crassipes is a promising system for municipal wastewater treatment. The first-order kinetic modelling was best suited for the removal rate since it presents higher R 2 , rate constant ( k ) and B values.

The study is aimed at the problem of high content of Cr6+, Cr 3+ and SO42- is high and low pH value in acid mine drainage (AMD). Moreover, treatment of AMD by sulfate reducing bacteria (SRB) requires the addition of carbon source, while the treating effectiveness is not good enough on its own. The sugarcane slag, the corn cob and the sunflower straw were selected as the SRB carbon source cooperating with iron scrap to construct the dynamic columns 1, 2 and 3. The mechanism of removing Cr6+, Cr3+, SO42- and H+ and the regularity of sustained release of carbon source and TFe release was studied in AMD. The removal efficiency of heavy metal ions, the ability of sustained release of carbon source, and the ability of adjusting acid by the three dynamic columns were compared. The result shows that the average removal rates of Cr6+, Cr3+ and SO42- in effluent of dynamic column 1, filled by sugarcane slag, iron scrap and SRB, were 96.9%, 67.1% and 54.3%. The average release of TFe and chemical oxygen demand (COD) were 4.4 and 287.3 mg/L. Its average pH was 6.98. Compared with the performance of dynamic columns 1, 2 and 3, dynamic column 1 performed best in removing Cr6+, Cr3+ and SO42- from AMD and controlling the release of COD and TFe, adjusting the pH of the solution. The study is of significance in treatment of AMD by taking for biomass materials as SRB carbon source in cooperation with iron scrap.

China's crude steel output has grown rapidly since 1990, accounting for more than half of worldwide production in 2019. Iron and steel industry (ISI) in China's energy consumption and carbon emissions accounted for a higher proportion. In the context of China's \"carbon peak, carbon neutrality\", the ISI attaches great importance to energy conservation and emission reduction. The BF-BOF long process is far from meeting the China’s policy needs in terms of energy-saving and emission-reducing targets. Therefore, the short process of EAF based on scrap steel’s recycling and direct reduced iron (DRI)’s production has attracted great attention. The e-p approach and scenarios analysis method were used to research the impact of scrap steel's recycling and DRI's production on energy demand and carbon emissions of China's ISI. By 2050, scenario 4 (30% DRI based on coal gasification–gas plus 70% scrap steel for EAF) will have the lowest energy consumption (1.79 × 1011 kgce) and scenario 3 (30% DRI based on hydrogen plus 70% scrap steel for EAF) will have the lowest carbon emissions (3.42 × 1011 kg). The results show that the short process of EAF based on scrap steel recycling and DRI is an extremely important approach for the sustainable development of China's ISI in the future.

Hydrogen metallurgy is a technology that applies hydrogen instead of carbon as a reduction agent to reduce CO 2 emission, and the use of hydrogen is beneficial to promoting the sustainable development of the steel industry. Hydrogen metallurgy has numerous applications, such as H 2 reduction ironmaking in Japan, ULCORED and hydrogen-based steelmaking in Europe; hydrogen flash ironmaking technology in the US; HYBRIT in the Nordics; Midrex H 2 ™ by Midrex Technologies, Inc. (United States); H 2 FUTURE by Voestalpine (Austria); and SAL-COS by Salzgitter AG (Germany). Hydrogen-rich blast furnaces (BFs) with COG injection are common in China. Running BFs have been industrially tested by AnSteel, XuSteel, and BenSteel. In a currently under construction pilot plant of a coal gasification-gas-based shaft furnace with an annual output of 10000 t direct reduction iron (DRI), a reducing gas composed of 57vol% H 2 and 38vol% CO is prepared via the Ende method. The life cycle of the coal gasification—gas-based shaft furnace—electric furnace short process (30wt% DRI + 70wt% scrap) is assessed with 1 t of molten steel as a functional unit. This plant has a total energy consumption per ton of steel of 263.67 kg standard coal and a CO 2 emission per ton of steel of 829.89 kg, which are superior to those of a traditional BF converter process. Considering domestic materials and fuels, hydrogen production and storage, and hydrogen reduction characteristics, we believe that a hydrogen-rich shaft furnace will be suitable in China. Hydrogen production and storage with an economic and large-scale industrialization will promote the further development of a full hydrogen shaft furnace.

In the last decade, government policies promoting foreign investments in the industrial sector particularly for small and medium scale enterprises in Nigeria have led to increased establishment of scrap-iron recycling factories in many states of the federation. Albeit the economic benefits in terms of waste material sourcing and job creation, these scrap-iron recycling factories have attracted significant public criticism due to the characteristic uncontrolled pollution (toxic gases) plume released from their operations into the atmospheric environment of host communities and thus aggravating existing and unresolved rural and urban air pollution problems in Nigeria. This study therefore provides model-based estimates of atmospheric dispersion for gaseous pollutants (SO2 and NOx) released from a scrap-iron recycling factory located in Ile-Ife, southwest Nigeria as a case study for investigating emission signature from such sources. Meteorological parameters measured at the factory location in 2012 and 2013 were used to execute U.S recommended short range (<50 km) Gaussian-based regulatory air pollution dispersion model (AERMOD: American Meteorological Society/Environmental Protection Agency Regulatory Model, v12060). Isopleths of maximum concentration values for 1 h averaging period were projected to occur within 1.5 km radius from the factory in SW and NW directions during early morning hours (02:00–06:00 h (GMT + 1)). Prevailing meteorological conditions during periods of maximum concentration were characterized by stable atmosphere dT/dz (>0.01°C/m), very weak winds (<1.5 ms−1), low mixing height (<200 m) and high relative humidity (>90%).

Steelmaking in the electric arc furnace (EAF), either scrap-based or based on hydrogen direct reduced iron, will in future contribute substantially to the reduction of CO2 emissions in the iron and steel industry. However, there still will be the need to introduce carbon into the EAF process either to carburize the steel or to create foaming slag to improve the energy efficiency of the melting process. So, to reach the emission reduction goals set around the world, it will be necessary to substitute fossil charge and injection carbon used in EAF steelmaking with alternative carbon sources. This review presents the recent research on carbon-neutral biomass-based and circular rubber or plastics-based carbon sources and their potential to substitute fossil charge or injection carbon in the EAF process. It also discusses the current state-of-the art and suggests further opportunities and needs for research and development to use alternative carbon sources to produce a really green and carbon neutral and/or fully circular steel.

The purpose of the foundry is to provide the consumer with blanks for general machine-building (special) purposes which are as close as possible to the size of the future part in full compliance with the requirements. The competitiveness of these products is primarily dependent on the use of efficient and reliable smelting equipment which meets the necessary cost. The replacement of high-value ironworks and ironworks iron with steel scrap using induction melting furnaces (ICFs) reduces the cost of producing synthetic cast iron. However, this results in temperatures greater than 1500 °C, reduced lining stability and increased downtime of the smelter. As a result of the research carried out, a technology for the use of quartzite is proposed. Thereby, the purpose of this work is to establish temperature regimes for the smelting of synthetic pig iron, allowing the use in metal filling up to 70–90% of steel scrap; this leads to a reduction in the cost of purchasing bulk materials (depending on the brand of cast iron) up to 50% and, thus, increases the efficiency of synthetic cast iron smelting and castings production in general. After removal of the original moisture and the subsequent sintering of the manufactured lining, it provides the possibility of melting using the melting temperatures 1550–1600 °C. It increases the efficiency of the operation of the melting furnaces and eliminates the consumption of the ironworks and the melting of the cast iron in the blast furnace, as well as the cost of the lost alloy. As a result, metallurgical production will be able to reduce the volume of production and supply of cast iron for ironworks, which will improve their environmental situation during the production and processing of necessary raw materials.