Solid Products Research Articles

Effects of water washing and KOH activation for upgrading microalgal torrefied biochar

Torrefaction is an effective pathway for microalgal solid biofuel upgrading, and alkali metal activation is also an efficient method to enhance fuel properties. This study explores the comparison of torrefaction alone and KOH activation combined with torrefaction to determine a better operation for biochar production from the microalga Nannochloropsis Oceanica. The results indicate that the HHV ranges of KOH-activated biochar and unactivated biochar are 25.611–32.792 MJ·kg−1 and 25.024–26.389 MJ·kg−1, respectively. Furthermore, KOH-activated biochar is better than unactivated biochar, with less residue, broader pyrolysis and combustion temperature ranges, higher elemental carbon, and less combined carbon. Moreover, KOH-activated biochar is close to the unactivated one from the viewpoint of expense calculation and life cycle assessment and thus possesses a better comprehensive performance. Overall, KOH activation is an efficient method for upgrading microalgal solid biofuel. The results are conducive to exploring further modification of microalgal solid biofuel production with better properties, thus leading to a greener and more efficient approach for upgrading fuel performance.

Catalytic pyrolysis of brewer's spent grain in spouted bed reactor using calcium oxide for upgrading oil

This study investigates the potential of brewer's spent grain as a fuel source through fast pyrolysis in a spouted bed reactor, aiming to contribute to sustainable fuel alternatives and the mitigation of the environmental consequences of fossil fuel consumption. Both non-catalytic and catalytic tests evaluated the effects of temperature, biomass feed rate, and catalyst concentration on yields and hydrocarbon composition. The intermediate temperature (550 °C) and biomass feed rate (960 g/h) were optimal for non-catalytic tests, favoring oil production. Additionally, the oil yield was enhanced with the use of CaO as a catalyst during the pyrolysis process. An optimization study identified conditions maximizing both liquid yield and hydrocarbon content. While catalytic tests showed a modest increase in oil yield compared to non-catalytic tests, the addition of CaO significantly improved oil quality by increasing hydrocarbon concentration and facilitating deoxygenation. Under optimal conditions, non-catalytic pyrolysis achieved a 41% liquid yield with 15% hydrocarbon content. For catalytic pyrolysis, optimal conditions yielded 43% oil with a hydrocarbon content of 33% and low water content. Moreover, the resulting oil exhibited a higher heating value (HHV) of 25.7 MJ/kg compared to the spent grain's 19.8 MJ/kg. Utilizing the CaO catalyst further increased the HHV value to 28.2 MJ/kg, highlighting its efficiency in enhancing liquid product quality. The solid products resembled mineral coals with higher energy density compared to the feedstock. This study highlights the potential of brewer's spent grain for fuel production in a spouted bed reactor and the CaO catalyst's effectiveness in improving liquid product quality.

Milk production and nitrogen excretion of grazed dairy cows in response to plantain (Plantago lanceolata) content and lactation season.

The study aimed to quantify milk production and urinary nitrogen (UN) excretion of dairy cows grazing pastures containing varying contents of plantain (Plantago lanceolata) in different seasons, under a typical farm practice. Four pasture treatments: perennial ryegrass (Lolium perenne) - white clover (Trifolium repens) (RGWC), RGWC + low plantain rate, RGWC + medium plantain rate, and RGWC + high plantain rate, were established in four adaptation areas (1 ha each) and 20 experimental plots (800 m2 each), and rotationally grazed by dairy cows over 14 grazing events during two lactation years. In each grazing (8-9 days), 60 or 80 Jersey-Friesian lactation cows were assigned to their pasture treatments, adapted to their pastures over the first six days, then each group of 15 or 20 cows were randomly allocated for grazing in five treatment plots over a two or three-day measurement period. Milk, urine, and faecal samples were collected from individual cows during the measurement period. The pasture treatments did not affect milk production, the yield and composition of milk solids, protein, fat, and lactose. However, cows grazing pastures containing between 17-28% dietary plantain reduced UN concentration by 15-27%, decreased UN excretion by 4-9%, and increased urine volume by 22-40%, compared to grazing the RGWC pasture. The change in UN concentration, and urine volume were associated with plantain proportion in the diet and were greater during late summer and autumn than during early summer. Incorporating 17%-28% dietary plantain with RGWC pastures can reduce the risk of nitrogen losses from pastoral systems, while maintaining the milk production of dairy cows.

A sustainable process for electrochemical production of 2-Iodosylbenzoic acid

Herein, an environmentally friendly, scalable and highly efficient process for production of 2-iodosylbenzoic acid, a well-established hypervalent iodine oxidant is reported. It is based on anodic oxidation of 2-iodobenzoic acid in anhydrous AcONa-AcOH electrolyte followed by simple work-up of solid product. In particular, a benefit of the developed electrochemical process is absence of any chemical oxidant, application of environmentally benign solvent, high Faradaic efficiency and product yield. The process on the anode side combines anodic oxidation of reactant to the desired product with separation process, i.e. removal of Na+ cation from the anolyte through a cation-exchange membrane leading to drop of AcONa concentration. Consequently, the product of high purity can be obtained simply by filtering the anolyte solution followed by drying the filtration cake. Interestingly, no washing by organic solvents is required. Moreover, both anolyte filtrate and catholyte can be reused multiple times. Energy and material balance and cost and environmental footprint analysis showed benefits of the developed process and suggested clear strategy towards further reduction of the product cost and, in particular, significant decrease of a generated waste amount.

Chloranilic acid–Gabapentin proton transfer complexes: Synthesis, spectroscopic, antimicrobial, computational, and molecular docking studies

The behavior of Gabapentin (Gab) towards Chloranilic acid (CLA) in solution is checked using UV–visible spectroscopy in three different solvents: methanol, ethanol, and acetonitrile. Applying Job's continuous variation method, the reaction is proved to proceed as a 1:1 molar composition in solution. On the other hand, two nanocrystalline solid products are isolated from the reaction of Gabapentin (Gab) with chloranilic acid (CLA), depending on the initial mole ratio (G1CLA and G2CLA). The isolated solid products are characterized by physicochemical tools (UV–vis., FT-IR, 1HNMR), proving the existence of proton transfer interaction. The semi-crystalline G2CLA (1CLA: 2Gab) product was investigated using powder x-ray diffraction, whereas the crystallized G1CLA (1CLA: 1Gab) product was analyzed by SXRD. The determined crystallite sizes for G1CLA and G2CLA were 30.02 nm and 40.17 nm, respectively. G1CLA was optimized in ethanol and gas phase, using DFT computational study, with basis sets B3LYP/6–31+G(d,p). The calculations showed the occurrence of charge transfer and hydrogen bonding in gas phase whereas proton transfer took place in ethanol. NBO charge calculations, reactivity parameters, and MEP maps indicated that CLA exhibits e-accepting ability, while Gab demonstrates e-donating properties. The main electronic transition states were determined by TD-DFT method. Moreover, the isolated solids were subjected to biological activity study, against six pathogens: two fungi, two gram-positive, and two gram-negative bacteria. Molecular docking simulation of G1CLA was performed on the crystal structure of proteus vulgaris HigA antitoxin (6CF1), revealing a total binding energy of -74.8704 Kcal/mole.

Atomic-scale insight into arc plasma radiation-induced gassing materials ablation: photothermal decomposition behavior

In this study, we present a novel computational atomistic study of the photothermal decomposition behavior of arc plasma on radiation-induced gassing materials ablation, studying a polyamide 66 (PA66) system using reactive force field (ReaxFF) molecular dynamics (MD). We determine the infrared (IR) vibrational frequency of the PA66 permanent molecular dipole using MD and then computationally impose an electric field at the same frequency to simulate photothermal decomposition by IR, verifying our observations with gas chromatography-mass spectrometry (GCMS) of experimental decomposition. MD indicates that photothermal decomposition reaction is dominated by either cleavage at low temperature or cyclization at high temperature. At low temperature, initial chain scission takes place at the two amide C–N, and the remaining chains break down into a variety of molecular fragments and free radicals. Further increasing the temperature stabilizes a variety of branched chain structures via cyclization, debranching and polymerization, with further cleavage forming hydrocarbons and volatile small molecule gases. Overall, H2, CO, H2O, alkanes and alkenes are the main gaseous products and cyclic structures (especially nitrogen-containing three-membered ring) are the main solid products during the photothermal decomposition of PA66, and their formation results from a variety of complex chemical reactions. The results of MD cover the experimental observations of GCMS, demonstrating that this computational methodology helps us understand the molecular breakdown mechanisms of arc plasma radiation-induced gassing materials. We also discuss the physical mechanism by which the main gas can accelerate arc quenching, and the importance and necessity of using electric fields to simulate IR photothermal decomposition of arc-induced ablation.

Innovative Power Generation Technologies for Improved Household Energy Delivery and Sustainable Future: Classical Solutions from ENEA Research Centre, Trisaia Italy

The present communication is focused predominantly on important R&D solutions relevant to renewable energy technologies covering the following: (i) Innovative heat transfer fluid and thermal storage technology based on a molten salt mixture developed by ENEA for large-scale heat storage. The system uses a parabolic trough collector, compared with diathermic oil, which allows higher operating temperature, resulting in significant benefits to the plant’s operation, safety and the environment. (ii) The world’s first solar disk powered by air micro turbine developed by ENEA. (iii) An innovative steam-explosion prototype plant installed at ENEA for the pre-treatment of lignocellulosic biomass and the fractionation of bio components to generate ethanol from lignocellulosic material using hemicellulose and lignin. (iv) The production of hydrogen-enriched biogas using steam as the gasification agent, which helps in obtaining nearly nitrogen-free product gas and with a high calorific value of around 12 MJ/Nm3 dry gas and a high percentage of hydrogen (up to 55%) while using steam as the gasifying agent in the presence of a catalyst. (v) A rotary kiln plant, with the main purpose being to develop and optimize a thermo-chemical process to convert used rubber tyres so as to recover material and energy, as well as other solid products, with high value-added “Activated carbon” and synthesis gas.

Vacuum Pyrolysis of Brazilian coal, peat and biomass – Results on characterization of feedstock, solid residues, pyrolysis liquids and conversion rates

Pyrolysis of solid fuels such as coal, peat and biomass enables conversion into solid and liquid products, with noncondensable gas being a by-product. The present study evaluates conversion characteristics of Brazilian coal, peat and biomass samples using vacuum pyrolysis techniques. Feedstock and their respective solid residues (chars) and pyrolytic liquids obtained under vacuum pyrolysis conditions were characterized by proximate and ultimate analyses, gross calorific value, petrographic analyses, reactivity to CO2, Raman spectroscopy and organic geochemical methods (extraction, liquid chromatography). Chemical and physical properties in the feedstock samples and solid residues are highly variable. In the coals mean vitrinite reflectances ranged from 0.44% to 1.18% Rrandom indicating a rank range from subbituminous to high volatile/medium volatile bituminous coal. Reflectance measurements obtained from vitrinoid particles identified in solid residues from coal, peat and biomass varied from 2.10% to 10.64% Rrandom. Analyses of the liquid products indicate a tendency of the aliphatic fraction to increase in most of the samples during the pyrolysis process, as well as the predominant formation of polar compounds in the condensable liquids. The results of this study suggest that among the coal samples investigated major conversion to liquids and gases (29.7%–33.2%) occurs in the high volatile bituminous coals from Santa Catarina, whereas in the biomass samples Mamona (Castor Beans), wood chips (Eucalyptus), wooden bars (pinus) and signal grass have all conversion rates > 60%. The conversion rates for the peat samples varied between 32.5 and 46.6%. Reflectance values determined on vitrinoid biomass chars indicate a potential use in soil amendment.

Removal of sulfur hexafluoride in molten-tin bubble column reactors: Kinetics parameter identification and scale-up studies

This study presents the degradation of sulfur hexafluoride (SF6), which is a greenhouse gas emitted from semiconductor industry, in a molten metal bubble column reactor (MMBCR) using tin. Experiments were conducted in a bench-scale MMBCR ranging from 468 °C to 668 °C using a mixture of N2 and 1000 ppm SF6 to estimate reaction kinetic parameters, where high-value solid product (SnS and SnF2) used in solar-cell devices were produced. A one-dimensional MMBCR model integrating reaction kinetics, axial dispersion, and heat transfer was formulated to investigate hydrodynamics and the performance of three pilot-scale multitubular MMBCRs at a feed flow rate of 300 LPM. At 650 °C, the SF6 removal efficiencies (η) of the pilot-scale MMBCRs with 80, 60, and 40 tubes at the same height (=0.5 m) and diameter (=0.1 m) were 85 %, 83 %, and 82 %, respectively. The pilot-scale MMBCR featuring 80 tubes exhibited the highest η owing to a low axial dispersion coefficient and high residence time. This study provides useful insights and guidelines for the design and upscaling of SF6 degradation processes utilizing MMBCRs in the semiconductor industry.

The effects of stocking rate, residual sward height, and forage supplementation on forage production, feeding strategies, and productivity of milking dairy cows

The intensification process in Uruguayan dairies over the last 30 years has involved increases in stocking rate (SR) and individual milk production. This research aimed to compare biophysical indicators along with the associated feeding strategies for Holstein–Jersey crossbred dairy cow systems. The comparison was conducted in farmlets representing a typical Uruguayan pasture-based dairy system on a grazing area. The study spanned from 2017 to 2019, combining 1.5 or 2.0 milking cows per hectare (SR), with two different residual sward heights (RH)—low (LR) and high (HR). These combinations resulted in four treatments: 1.5 LR, 1.5 HR, 2.0 LR, and 2.0 HR. A total of 96 cows were randomly allocated to each treatment based on parity, body weight (BW), and body condition score (BCS) for the years 2017, 2018, and 2019. The response variables per hectare were analyzed using a linear mixed model, including SR, RH, their interaction effect, year, and paddock as a repeated measurement. Results show that forage production did not differ between treatments, and forage directly harvested by cows was affected by SR, as well as milk and solids productivity. An interaction effect was detected between SR and RH on milk and milk solids production where 2.0 HR was higher than 2.0 LR, but treatments on SR 1.5 were not different between them. The consumption of concentrate, forage, and conserved forage per hectare was influenced by the level of SR. However, individual milk production was not influenced by SR or RH. Dry matter intake were affected by SR where 2.0 HR had higher consumption than 1.5 LR and 1.5 HR but was not different from 2.0 LR. The concentrate DMI per cow was not different between treatments, while the conserved forage DMI per cow was affected by SR and higher for SR 2.0 than that for SR 1.5. These combinations of feed determined varying proportions of time allocated for grazing, which were influenced by the SR and RH. This research highlights different approaches to enhance the competitiveness of Uruguayan grazing systems through improvements in forage harvest.

Evaluation of Sb-Nd and Te-Nd phases within the U-Zr fuel matrix and their interactions with HT9 alloy

Antimony (Sb) and tellurium (Te) were investigated as potential additives for U-10Zr (wt.%) metallic fuel to limit the fuel-cladding chemical interaction (FCCI) with HT-9 alloy. Neodymium (Nd) was utilized to simulate the formation of lanthanide-based solid fission products which are known to play a detrimental role in FCCI. Fuel alloys of U-Zr-Sb-Nd and U-Zr-Te-Nd were evaluated in their annealed condition and compared against their as-cast conditions. Isothermal diffusion couple experiments were performed between U-Zr-Nd, U-Zr-Sb-Nd, and U-Zr-Te-Nd against the cladding alloy HT9 to evaluate the effectiveness of the additives to stabilize Nd within the fuel alloys, as well as investigate the interaction regions that form between the different fuel alloys and HT9. SbNd and Sb3Nd4, and TeNd are found to be the primary neodymium-based phases formed in the U-Zr-Sb-Nd and U-Zr-Te-Nd alloys, respectively. The zirconium-based phase, Zr2Sb, is also found to form within the former alloy. All phases were found to remain stable through the diffusion experiments and exhibited no interaction with HT9 constituent elements. Preferential interaction between Nd with additivities Te and Sb compared to constituting elements in HT9 was further verified based on density functional theory (DFT) calculated enthalpy of mixing.

Transcriptomic analysis and oxidative stress induced by sodium dichloroisocyanurate in the intestine of Phascolosoma esculenta

Sodium dichloroisocyanurate (NaDCC, C3Cl2N3NaO3) is a solid chlorine-containing product that is widely used as a disinfectant in living environments, which has potential toxic effects on human and rats. Phascolosoma esculenta is a species native to the southeast coast of China and can be used as an indicator organism. In the present study, 150 P. esculenta were used to determine the LC50 of NaDCC for P. esculenta, then 100 P. esculenta were used to analysis the change of histopathology, oxidative stress and transcriptome after NaDCC exposure. The results showed that the LC50 of NaDCC for 48 h was 50 mg/L. NaDCC stress induced pathological events in P. esculenta, including blisters, intestinal structural damage and epithelial cell ruptured or even loss. The highest and lowest intestinal activity of superoxide dismutase in individual survivors was detected at 12 h and 72 h, respectively. Malondialdehyde levels in the intestine declined gradually from 3 h and increased at 9 h, and peaked at 12 h. Total antioxidant capacity declined at 3 h and dropped below the levels of control group after 9 h. Transcriptome sequencing analysis yielded a total of 48.65 Gb of clean data. A total of 34,759 new genes were found including 957 differentially expressed genes (DEGs). The DEGs were significantly enriched in ferroptosis, response to chemicals, response to stress, immune system, ion transport, cell death, oxidation-reduction, cellular homeostasis, protein ubiquitination, and protein neddylation. Additionally, the levels of detoxification enzymes, such as glutathione-S-transferase, cytochrome P450, ABC, UDP-glycosyltransferase and SLC transporters of endogenous and exogenous solutes were significantly changed. Overall, the results provide reference for reasonable use of disinfectants during farming, and also provide insight into the mechanisms related to NaDCC toxicity in P. esculenta.

Solid waste products of EU DEMO – Focus on tungsten dust reprocessing

The operation of the future EU DEMO, a fusion power plant, will produce various kinds of radioactive waste through neutron activation and contamination with tritium.For the EU DEMO's nuclear fusion reactor, the preliminary construction designs of the main systems and components are known. These designs, as well as the operation of experimental fusion test facilities, are the basis for assessing which materials are likely to become waste. The continuously generated waste materials are solid dusts. They originate in different parts of the fusion reactor, move and usually settle elsewhere. These dusts also appear during intermediate periodic maintenance of a fusion device, most often from the armour surfaces. Another group of similar wastes is generated during the treatment of replaced parts.The waste comprises dust abraded during the overhaul of the equipment, and other small residues. Tungsten dust, which contains tritium, is produced in the largest quantity.An overview of the expected solid waste masses was reviewed, distinguishing what could come from operational process and what could come from decommissioning according to their activation classification levels and with regards to the storage potential capacities. Proposals for processing methods (for in or outside the DEMO site) that allow for reducing and minimizing the solid waste are included. Moreover, the lessons learnt from the ITER experiment are considered.Two methods using high-temperature technologies – induction heating or MSO (Molten Salt Oxidation) technology, are proposed for reprocessing the tungsten dust waste.

An efficient synthesis of 4,5-disubstituted 1,2,3-triazoles by three-component reaction between sodium azide, ethyl cyanoacetate or malonitrile and arylglyoxals

Three-component reaction between sodium azide, ethyl cyanoacetate or malonitrile and arylglyoxals afforded 4,5-disubstituted 1,2,3-triazole derivatives in high yields. All reactions were conducted in ethanol as an environmentally benign solvent at room temperature without using any catalyst or modifier. Stable solid products were easily isolated and purified by washing with water and diethyl ether. The structures of the compounds were proved by 1H and 13C NMR and IR spectral and elemental analysis data.

Development of sustainable masonry solid blocks by the incorporation of industrial and agro waste.

<p>Bricks have been extensively adopted for centuries and continue to play a vital role in the construction industry. Nevertheless of its dependable workability and accessibility, fired clay brick production has been recognized for its comparatively high energy and resource requirements. Traditional clay bricks, widely used in construction for centuries, pose significant environmental challenges. The extraction of clay for brick production can result in habitat destruction and landscape alteration. The firing process in brick kilns consumes substantial amounts of energy, often derived from non-renewable sources, contributing to greenhouse gas emissions. The development of sustainable masonry solid blocks signifies a revolutionary change in the construction sector, providing a sustainable substitute for conventional building materials. These blocks, typically made from reused or locally obtained materials, demonstrate a dedication to environmental stewardship and the efficient use of resources. This innovative idea of utilizing some industrial waste such as fly ash, bagasse ash, marble dust and stone dust in solid block manufacture significantly reduces the environmental pollution problem, offers an alternative construction material source, and makes the solid blocks economical. Different types of trail mixes have been developed, and the produced masonry solid blocks underwent a series of experimental investigations. The solid bricks are being compared to conventional cement blocks. The developed sustainable solid block (MB6) exhibits a strength that is 43.78% greater than that of conventional cement solid blocks. The present study attempts to determine the optimal material proportion for innovative solid block production. Key words: Carbon footprint, Eco-friendly building blocks, Bagasse ash, Marble dust and Industrial waste</p>

Distribution of gasification products and emission of heavy metals and dioxins from municipal solid waste at the low temperature pyrolysis stage.

Gasification is widely regarded as one of the most practical, economical, and environmentally friendly waste disposal technologies for municipal solid waste (MSW). The pyrolysis stage (300-500°C) is crucial for weight loss during MSW gasification, as a considerable amount of organic matter breaks down, producing high-value synthesis gas. This study investigated the product distribution and pollutant emission characteristics within this temperature range and its influencing factors during MSW gasification using a self-designed MSW gasification device. Results indicated that MSW underwent approximately 70% weight loss within this temperature range, yielding low amounts of inorganic and short-chain organic products, with mainly long-chain organic compounds of C16-C34. The atmosphere variation had minimal effect on the elemental composition and content of solid phase products. X-ray fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) analyses showed that Mn and Zn were the primary components of heavy metal leaching toxicity in solid phase products, with their contents increasing as temperature increased. Synthesis gas showed the highest content of heavy metal As element, reaching a peak at 400°C. Higher gasification temperature and lower oxygen flow rate significantly reduced the dioxin content and I-TEQ values, with highly chlorinated isomers being the predominant dioxin isomers. Nonetheless, low-chlorinated dioxins accounted for more than 50% of the I-TEQ. This study improves our understanding of the gasification process of MSW.

Evaluation on thermal pyrolysis of biomass straw waste: Focusing aspects of products yields, syngas emissions and solid products characterization

AbstractIn this study, a systematic and quantitative investigation of the pyrolysis characteristics of biomass was conducted in a fixed‐bed tubular reactor, and the influence of pyrolysis temperature on product yields, gas emission characteristics, and syngas compositions as well as physicochemical characterization of resulting solids (i.e., char/ash morphologies, mineral transformations, and elemental compositions) was explored in detail. The pyrolysis experiments were performed under N2, and the resulting solid characterization was detected by XRD, SEM, and EDX. The results indicated that with increasing the pyrolysis temperature from 400 to 800°C, the gaseous product yields increased from 54.9% to 66.7%, while the solid product yield showed a reverse trend, varying within 27.7%–40.5%. Meanwhile, the volume fraction of H2 in syngas increased from 7% to 33%, while the CO2 presented an opposite trend, suggesting that high temperature favored H2 formation and inhibited CO2 formation. On the whole, the CO and CO2 emissions were prior to CH4, H2, and CnHm in sequence. A large amount of sylvite (KCl), quartz (SiO2), dolomite (CaMg(CO3)2), and pyroxene (CaMgSi2O6) in the resulting solids were identified in crystal phases. Higher pyrolysis temperature had a significant influence on solid microstructures, resulting in a relatively higher slagging tendency due to low melting eutectics containing K‐rich and Ca‐rich minerals.

Smart Tissue Carriers for Innovative Cosmeceuticals and Nutraceuticals

The present review was conducted to investigate the possibilities in realizing novel nanostructured tissues containing functional molecules that can be commercialized as solid products (without using emulsifiers and preservatives) for cosmeceutical and nutraceutical applications. After considering the principal concepts regarding skin and mucous features and physiologies, the possibilities in using bio-based, biodegradable and biocompatible materials was explored by investigating the correlations between their structures and morphologies with respect to the characteristics of the skin extracellular matrix (ECM). Regarding the new smart type of biodegradable tissues, their possible composition was reviewed in relation to the skin aging process and to the current contest for novel, innovative cosmeceuticals and nutraceuticals that consider the “beauty from within” concept. The barriers to the development of these new tissues were mainly identified due the necessity in defining the claim regarding green products. Moreover, the market growth data regarding these novel products were highlighted to support the idea that the diffusion of smart tissue-based cosmeceuticals and nutraceuticals is an opportunity for new sustainable industrial chains in the development of bioeconomies.

Cotreatment strategy for hazardous arsenic-calcium residue and siderite tailings via arsenic fixation as scorodite

Siderite tailings is a potentially cost-free iron (Fe) source for arsenic (As) fixation in hazardous arsenic-calcium residues (ACR) as stable scorodite. In this study, a pure siderite reagent was employed to investigate the mechanism and optimal conditions for As fixation in ACR via scorodite formation, while the waste siderite tailings were used to further demonstrate the cotreatment method. The cotreatment method starts with an introduction of sulfuric acid to the ACR for As extraction and gypsum precipitation, and is followed by the addition of H2O2 to oxidize As(III) in the extraction solutions and finalized by adding siderite with continuous air injection for scorodite formation. The dissolution-oxidation of siderite can slowly produce Fe(III) to control aqueous As(V)-Fe(III) precipitation supersaturation for continuous scorodite crystallization. Chemical analyses show that the extraction efficiency of As from the ACR reaches 94.55%, while the precipitation yield of extracted As via scorodite formation arrives at 99.63% and 99.47%, leading to fixation efficiency of 94.20% and 94.04% in terms of the total As in the ACR by using siderite reagent and tailings, respectively. The final solid products show desirable TCLP stability and long-term stability, meeting the requirement for safe storage (GB 5085.3–2007). XRD, FTIR, and TEM results reveal that such high stability is attributable to the formation of scorodite and the surface adsorption of As on the raw siderite and secondary maghemite. This innovative and economical application of siderite tailings for the treatment of hazardous ACR can be extended to the management of hydrometallurgical wastes.

Solid Product Analysis on the Epoxy Resin Surface After Flashovers in C4F7N-Based Gas Mixtures Under Negative DC Voltage

Solid Product Analysis on the Epoxy Resin Surface After Flashovers in C₄F₇N-Based Gas Mixtures Under Negative DC Voltage