Ultrasonic Quality Assurance at Magnesia Shotcrete Sealing Structures.

Engineered barriers are a key element to enable safe nuclear waste disposal. One method currently under research for their construction is magnesia concrete applied in a shotcrete procedure. In this study, the ultrasonic echo method is evaluated as a means for quality assurance. Imaging of internal structures (backwall, boreholes) and defects, such as delamination, has successfully been achieved in the shotcrete. Additionally, detailed information about the potential cause of selected reflectors are obtained by phase analysis. In several test blocks of various sizes, no consistent concrete section boundaries have been found by ultrasonic imaging, which was verified by subsequent drilling and complementary tests. An experiment with artificial defects imitating cracks, air-filled voids, and material with lower density has been challenging and shows the limitations of the current methods. Although significant defects, such as a large delamination, are reliably identified, several smaller defects are not identified. Generally, ultrasonic imaging provides a suitable base as a mean for quality assurance during and after the construction of sealing structures. However, further developments are required to enhance the reliability of the method and a full validation is still pending. Still, the method has potential to increase the safety of nuclear waste repositories.

Bioelectrochemical acidolysis of magnesia to induce struvite crystallization for recovering phosphorus from aqueous solution.

A novel struvite crystallization method induced by bioelectrochemical acidolysis of magnesia (MgO) was investigated to recover phosphorus (P) from aqueous solution using a dual-chamber microbial electrolysis cell (DMEC). Magnesium ion (Mg2+) in the anolyte was firstly confirmed to automatically migrate from the anode chamber to the cathode chamber, and then react with ammonium (NH4+) and phosphate (PO43-) in the catholyte to form struvite. Recovery efficiency of 17.8%-60.2% was obtained with the various N/P ratios in the catholyte. When MgO (low solubility under alkali conditions) was added into the anolyte, the bioelectrochemical acidolysis of MgO naturally took place and the released Mg2+ induced struvite crystallization in the cathode chamber for P recovery likewise. Besides, there was a strong linear positive correlation between the recovery efficiency and the MgO dosage (R2 = 0.935), applied voltage (R2 = 0.969) and N/P ratio (R2 = 0.905). Increasing the applied voltage was found to enhance the P recovery via promoting the MgO acidolysis and the released Mg2+ migration, while increasing the N/P ratio in the catholyte enhanced the P recovery via promoting the struvite crystallization. Moreover, the electrochemical performance of the system was promoted due to more stable anolyte pH and lower pH gradient between the two chambers. Current density was promoted by 10%, while the COD removal efficiency was improved from 78.2% to 91.8% in the anode chamber.

[Prevention of cognitive dysfunction in elderly cancer patients operated on the pelvic organs in conditions of multimodal anesthesia]. / Profilaktika kognitivnoi disfunktsii u pozhilykh onkologicheskikh bol'nykh, operirovannykh na organakh malogo taza v usloviiakh mul'timodal'noi anestezii.

The aim of the study was to evaluate the impact of various variants of multimodal anesthesia on the cognitive functions of elderly patients after surgical interventions on pelvic organs, the development of preventive measures for POCD. MATERIAL AND METHODS: A study was conducted in 76 elderly patients aged 62 to 84 years with an increased risk of developing POCD. Of these, 46 women and 30 men. Patients were divided into two groups, depending on the type of anesthesia. The 1st group consisted of 37 patients who had low-flow anesthesia with sevoflurane combined with epidural analgesia. 2nd - 39 patients who had anticipated multimodal analgesia on the basis of systemic administration of lidocaine, sulphate magnesia, verapamil. In each group, patients are divided into subgroups - the main (O) and control (K). In the main subgroups anesthetics were supplemented with 20 ml. Cytoflavin, administered 20-25 minutes before the end of surgery and on the 1-3 days of the perioperative period. Cognitive functions were assessed by standardized scales: Mini Mental State Examination (MMSE), Montreal Cognitive Evaluation Scale (MoCA), Frontal Assessment Batteries (FAB). The level of anxiety and depression was determined by the hospital scale of anxiety and depression (HADS). RESULTS: At oncological patients of advanced age in 52.5% of cases there is a moderate degree of cognitive impairment. In the perioperative period, in the study groups, when using different variants of multimodal anesthesia, there is an equivalent transient decrease in cognitive functions by 12.5 and 12.8%. The use of cytoflavin can reduce the manifestation of POCD from 1-day perioperative period, improve the cognitive status of patients. CONCLUSION: In cancer patients of advanced age, cognitive impairment is observed, aggravated after surgical treatment, regardless of the variant of multimodal anesthesia. Protection by Cytoflavin allows to restore the cognitive functions of elderly cancer patients, reduce the manifestations of POCD.

Preparation and Properties of Lightweight Aggregates from Discarded Al2O3-ZrO2-C Refractories.

Refractory materials are an important pillar for the stable development of the high-temperature industry. A large amount of waste refractories needs to be further disposed of every year, so it is of great significance to carry out research on the recycling of used refractories. In this work, lightweight composite aggregate was prepared by using discarded Al2O3-ZrO2-C refractories as the main raw material, and the performance of the prepared lightweight aggregate was improved by adjusting the calcination temperature and introducing light calcined magnesia additives. The results showed that the cold compressive strength and thermal shock resistance of the lightweight aggregates were significantly improved with increasing calcination temperature. Moreover, the introduction of light calcined magnesia can effectively improve the apparent porosity, cold compressive strength, and thermal shock resistance of the prepared lightweight aggregates at the calcination temperature of 1400 °C. Consequently, this work provides a useful reference for the resource utilization of used refractories, while the prepared lightweight aggregates are expected to be applied in the field of high-temperature insulation.

Biochar-enhanced three-dimensional conductive network thick electrodes for efficient lithium extraction from salt lake brines with high Magnesia-lithium ratios.

Enhancing the kinetic performance of thick electrodes is essential for improving the efficiency of lithium extraction processes. Biochar, known for its affordability and unique three-dimensional (3D) structure, is utilized across various applications. In this study, we developed a biochar-based, 3D-conductive network thick electrode (∼20 mg cm-2) by in-situ deposition of LiFePO4 (LFP) onto watermelon peel biomass (WB). Utilizing Density Functional Theory (DFT) calculations complemented by experimental data, we confirmed that this The thick electrode exhibits outstanding kinetic properties and a high capacity for lithium intercalation in brines, even in environments where the Magnesia-lithium ratios are significantly high. The electrode showed an impressive intercalation capacity of 30.67 mg g-1 within 10 min in a pure lithium solution. It also maintained high intercalation performance (31.17 mg g-1) in simulated brines with high Magnesia-lithium ratios. Moreover, in actual brine, it demonstrated a significant extraction capacity (23.87 mg g-1), effectively lowering the Magnesia-lithium ratio from 65 to 0.50. This breakthrough in high-conductivity thick electrode design offers new perspectives for lithium extraction technologies.

An experimental investigation on the effects of magnesia and alumina nano additives on the exhaust emissions and performance of CI engine using spirulina microalgae biodiesel.

The need for non-renewable fuels is steadily decreasing with their ever-increasing cost and air pollution. As a result, renewable fuel such as biofuel is used as a fuel substitute for diesel engines. The effects of magnesia and alumina nanoparticles on the exhaust pollutants and performance of a naturally aspirated, 17.5 compression ratio, 4-stroke CI engine operating on spirulina microalgae biodiesel, and its amalgams were explored. Oxides of nitrogen, thermal efficiency, carbon dioxide, fuel consumption, and hydrocarbons were among the attributes studied. Test outcomes revealed that the doping of magnesia and alumina nano additives in spirulina biodiesel resulted in increased thermal efficiency and oxides of nitrogen, succeeded by a decrease in fuel consumption and hydrocarbons, at all loads, compared to amalgams without nano additives. At maximum load, the increase in thermal efficiency and oxides of nitrogen was found to be 1.15 and 1.46% with nano magnesia-doped blends when compared to corresponding spirulina blends. On the other, hand when nano alumina is doped in spirulina amalgams, the increase in thermal efficiency and oxides of nitrogen was observed to be 0.82 and 0.97%, respectively. Similarly, fuel consumption and hydrocarbons were reduced by 1.02 and 9.52%, 1.014, and 7.66%%, respectively, for magnesia and alumina-enriched biodiesel, contrasted to that of biodiesel blends.

Does milk of magnesia impact length of hospital stay after major colorectal resection.

BACKGROUNDS: Milk of magnesia (MoM) has been reported to accelerate return of bowel function following surgery. However, there is insufficient evidence regarding the impact of MoM on postoperative recovery after colorectal surgery. We aimed to determine the impact of MoM on postoperative length of stay in patients undergoing colorectal surgery. METHODS: All patients who underwent colorectal resection without an ileostomy between 2015 and 2018 were included. Patients were divided into two groups based on whether postoperative MoM (MoM) was administered or not, according to surgeons' prescribing preferences. Consecutive patients of surgeons who prescribe MoM were included in the MoM group, while consecutive patients of surgeons who prefer not to prescribe MoM served as the control group. Age, gender, preoperative comorbidities, surgical approach, length of stay, readmission, postoperative complications and mortality were evaluated and compared between the groups. RESULTS: A total of 3292 patients were included; 523 (15.9%) patients were prescribed MoM. Patients in the MoM group were found to be significantly older, with higher BMI and ASA class, and more often undergoing operations for cancer resection or colostomy creations, than the control group. Postoperative complications were comparable between the groups. On multivariable linear regression, MoM use was associated with a 14.1% reduction in length of stay (MoM group 4 (2; 8), control group 5 (3; 8 P = 0.006)). CONCLUSION: MoM as adjunct medication in the postoperative period following colorectal surgery is associated with reduced length of stay, without an increase in postoperative complications.

In Vitro Degradation of Mg-Doped ZrO2 Bioceramics at the Interface with Xerostom® Saliva Substitute Gel.

Zirconia-based bioceramics, one of the most important materials used for dental applications, have been intensively studied in recent years due to their excellent mechanical resistance and chemical inertness in the mouth. In this work, the structural, morphological and dissolution properties of the Zr1-xMgxO2 (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) system, prepared by the conventional ceramic method, were evaluated before and after immersion in saliva substitute gel (Xerostom®, Biocosmetics Laboratories, Madrid, Spain), one of the most common topical dry mouth products used in dentistry. The X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) techniques were employed to investigate the phase transformations and morphology of the ceramics during the degradation process in Xerostom®. In vitro analyses showed overall good stability in the Xerostom® environment, except for the x = 0.05 composition, where significant t- to m-ZrO2 transformation occurred. In addition, the strong interconnection of the grains was maintained after immersion, which could allow a high mechanical strength of the ceramics to be obtained.

Effect of Low Nesquehonite Addition on the Hydration Product and Pore Structure of Reactive Magnesia Paste.

Reactive magnesia cement is considered an eco-efficient binder due to its low synthesis temperature and CO2 absorption properties. However, the hydration of pure MgO-H2O mixtures cannot produce strong Mg(OH)2 pastes. In this study, nesquehonite (Nes, MgCO3·3H2O) was added to the MgO-H2O system to improve its strength properties, and its hydration products and pore structure were analyzed. The experimental results showed that the hydration product changed from small plate-like Mg(OH)2 crystals to interlaced sheet-like crystals after the addition of a small amount of Nes. The porosity increased from 36.3% to 64.6%, and the total pore surface area increased from 4.6 to 118.5 m2/g. At the same time, most of the pores decreased in size from the micron scale to the nanometer scale, which indicated that Nes had a positive effect on improving the pore structure and enhancing the compressive strength. Combined with an X-ray diffractometer (XRD), a Fourier transform infrared spectrometer (FTIR), and a simultaneous thermal analyzer (TG/DSC), the hydration product of the sample after Nes addition could be described as xMgCO3·Mg(OH)2·yH2O. When Nes was added at 7.87 and 14.35 wt%, the x-values in the chemical formula of the hydration products were 0.025 and 0.048, respectively. These small x-values resulted in lattice and property parameters of the hydration products that were similar to those of Mg(OH)2.

Efficacy, safety, and acceptability of polyethylene glycol 3350 without electrolytes vs magnesium hydroxide in functional constipation in children from six months to eighteen years of age: A controlled clinical trial.

INTRODUCTION AND AIMS: There are few studies that compare polyethylene glycol (PEG) 3350 and magnesium hydroxide (MH), as long-term treatment of functional constipation (FC) in children, and they do not include infants as young as 6 months of age. Our aim was to determine the efficacy, safety, and acceptability of PEG vs MH in FC, in the long term, in pediatric patients. METHODS: An open-label, parallel, controlled clinical trial was conducted on patients from 6 months to 18 years of age, diagnosed with FC, that were randomly assigned to receive PEG 3350 or MH for 12 months. Success was defined as: ≥ 3 bowel movements/week, with no fecal incontinence, fecal impaction, abdominal pain, or the need for another laxative. We compared adverse events and acceptability, measured as rejected doses of the laxative during the study, in each group and subgroup. RESULTS: Eighty-three patients with FC were included. There were no differences in success between groups (40/41 PEG vs 40/42 MH, p = 0.616). There were no differences in acceptability between groups, but a statistically significant higher number of patients rejected MH in the subgroups > 4 to 12 years and > 12 to 18 years of age (P = .037 and P = .020, respectively). There were no differences regarding adverse events between the two groups and no severe clinical or biochemical adverse events were registered. CONCLUSIONS: The two laxatives were equally effective and safe for treating FC in children from 0.5 to 18 years of age. Acceptance was better for PEG 3350 than for MH in patients above 4 years of age. MH can be considered first-line treatment for FC in children under 4 years of age.

Solidification/Stabilization Technology for Radioactive Wastes Using Cement: An Appraisal.

Across the world, any activity associated with the nuclear fuel cycle such as nuclear facility operation and decommissioning that produces radioactive materials generates ultramodern civilian radioactive waste, which is quite hazardous to human health and the ecosystem. Therefore, the development of effectual and commanding management is the need of the hour to make certain the sustainability of the nuclear industries. During the management process of waste, its immobilization is one of the key activities conducted with a view to producing a durable waste form which can perform with sustainability for longer time frames. The cementation of radioactive waste is a widespread move towards its encapsulation, solidification, and finally disposal. Conventionally, Portland cement (PC) is expansively employed as an encapsulant material for storage, transportation and, more significantly, as a radiation safeguard to vigorous several radioactive waste streams. Cement solidification/stabilization (S/S) is the most widely employed treatment technique for radioactive wastes due to its superb structural strength and shielding effects. On the other hand, the eye-catching pros of cement such as the higher mechanical strength of the resulting solidified waste form, trouble-free operation and cost-effectiveness have attracted researchers to employ it most commonly for the immobilization of radionuclides. In the interest to boost the solidified waste performances, such as their mechanical properties, durability, and reduction in the leaching of radionuclides, vast attempts have been made in the past to enhance the cementation technology. Additionally, special types of cement were developed based on Portland cement to solidify these perilous radioactive wastes. The present paper reviews not only the solidification/stabilization technology of radioactive wastes using cement but also addresses the challenges that stand in the path of the design of durable cementitious waste forms for these problematical functioning wastes. In addition, the manuscript presents a review of modern cement technologies for the S/S of radioactive waste, taking into consideration the engineering attributes and chemistry of pure cement, cement incorporated with SCM, calcium sulpho-aluminate-based cement, magnesium-based cement, along with their applications in the S/S of hazardous radioactive wastes.

Comparison between CaO- and MgO-activated ground granulated blast-furnace slag (GGBS) for stabilization/solidification of Zn-contaminated clay slurry.

Stabilization/solidification (S/S) is a low-cost and effective remedial technique for dredged contaminated sediments. Quick lime (CaO)-activated and reactive magnesia (MgO)-activated ground granulated blast furnace slag (GGBS) are effective and low-carbon S/S binders. However, the existence of metals, especially Zn, in contaminated sediments, may hinder the hydration of GGBS. This study compared the performance and mechanisms of CaO-GGBS, MgO-GGBS and ordinary Portland cement (OPC) for the treatment of Zn-contaminated clay slurry using unconfined compressive strength (UCS) test, one-stage batch leaching test, and mineralogical and thermal analyses. The results showed that the application of the MgO-GGBS (GGBS dosage of 10 % and MgO of 0 %-3 % (of dry clay by mass)) had positive effects on the mechanical strength and Zn immobilization of the contaminated clay slurry while the CaO-GGBS affected negatively and the situation became even worse at a higher CaO dosage (0 %-1.5 % of dry clay by mass). In comparison with OPC, the application of MgO-GGBS produced higher mechanical strength and that for CaO-GGBS was the lowest. The Zn leaching difference depends on initial Zn concentrations. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results showed that a retarder, calcium zinc hydroxide, formed in the immobilization process when adding the CaO-GGBS binder, hindering the GGBS hydration and further leading to inferior strength and higher Zn leachability. The clay slurry treated by the MgO-GGBS binder was found to have a higher calcium silicate hydrate content which explained its high strength and low leachability.

Molecular dynamics investigation of the thermal behaviors of magnesium oxide ceramics at different pressures and temperatures.

Today, magnesia ceramics have attracted considerable attention due to their essential properties. Therefore, this paper investigates the impact of temperature (T) and pressure (P) on the thermal manner of magnesia ceramics using molecular dynamics simulations (MDS). As the T increases, the mobility of the structures increases. Therefore, the heat flux (HF) in the structures increments slightly due to the greater movement and the larger oscillation amplitude of the atomic samples. On the other hand, with increasing P, the oscillation amplitude and displacement of atomic samples are limited. Therefore, the thermal properties of the structure are expected to decrease. Studies show that increasing T from 250 to 350 K increases the average HF from 0.73 to 0.89 W/m2. Also, the average thermal conductivity (TC) increases from 30.58 to 38.27 W/mK. So, increasing the T means a certain amount of energy is fluxed in a shorter time. On the other hand, increasing the P from 0 to 5 bar decreases the average HF from 0.82 to 0.65 W/m2. Also, this issue leads to a decrease in the average TC from 33.49 to 30.96 W/mK.

Effective immobilization of geogenic As and Pb in excavated marine sedimentary material by magnesia under wet-dry cycle, freeze-thaw cycle, and anaerobic exposure scenarios.

Massive amounts of marine sedimentary materials with geogenic heavy metal(loids) are excavated by the subsurface construction projects and then exposed to weathering conditions, which pose potential threats to the environment. In the present study, 2 % magnesia (MgO) was applied to immobilize geogenic arsenic (As) and lead (Pb) in excavated marine sedimentary material. To better evaluate the immobilization efficiency under different environmental scenarios, the untreated and amended solids were subjected to wet-dry cycles, freeze-thaw cycles, and anaerobic incubation until 49 days. The leaching behaviors of As and Pb were investigated and their size fractionations in the leachates were compared. The results indicate that most Pb exists in particulate and agglomerated colloidal fractions (0.1-5 µm) in the leaching suspensions, while most As is found in dissolved forms (<0.1 µm). It is therefore necessary to consider the element type and exposure scenarios during environmental risk evaluation, particularly using the batch test as a routine compliance testing procedure. In the control test without MgO addition, the wet-dry cycle resulted in the "self-induced" immobilization of As and Pb. The pH decreases to the neutral range and the formation of amorphous Fe-(oxyhydr)oxides following pyrite oxidation largely explained the decreased As and Pb leaching. In comparison, the freeze-thaw cycle and anaerobic incubation tended to enhance As and Pb leaching. Overall, MgO addition significantly reduced the leachability of As and Pb and displayed sustained immobilization performance under all studied scenarios. These findings could be largely attributed to solid particle aggregation induced by MgO addition, including the adsorption of As and Pb onto newly formed Fe-(oxyhydr)oxides and/or MgSi precipitates. This study offers a simple and effective strategy for the sustainable management of excavated marine sedimentary materials contaminated by geogenic As and Pb.

XPS Study on Calcining Mixtures of Brucite with Titania.

In this work, we studied the phases in a Mg-Ti-O system using a 1:1 formulation of MgO:TiO2, mixing synthetic brucite of Mexican origin with TiO2 microparticles of high purity, with a heat treatment at 1100 °C for 1 h. Due to its valence electrons, TiO2 can contribute to the sintering process to improve density in MgO products. The raw materials and formulation by XPS and X-RD techniques were characterized. The results demonstrate the presence of different oxidation states in titania and the formation of different oxides in the Mg-Ti-O system when mixed and calcined at 1100 °C; additionally, we estimated the formation of vacancies in the crystal lattice during the transformation from hexagonal brucite to magnesia with a cubic structure centered on the faces. Its thermal behavior is indicated by the MgO-TiO2 phase diagram.

Optimization of nutrient removal performance of magnesia-containing constructed wetlands: a microcosm study.

Recently, magnesia has drawn much attention for enhancing phosphorus (P) removal of constructed wetlands. However, the poor nitrogen (N) removal efficiency of magnesia-containing constructed wetlands (Mg-CWs) inherently caused by magnesia impedes its application. In this study, peat and intermittent aeration were applied to enhance N removal in a Mg-CW, identified as P-CW and A-CW, respectively. A high TP removal rate (around 90%) was achieved in all CW, and the TN removal rate in the P-CW was 91.05% higher than that in the Mg-CW, which was mainly because the carbon source provided by the peat directly promoted the growth and metabolism of microorganisms and plants. Higher fresh weight of plants was obtained in P-CW (64.94 ± 5.78 g), compared with A-CW (35.88 ± 15.25 g) and Mg-CW (46.25 ± 18.88 g), accomplished by stronger tolerance to high pH (>10). The microbial abundance (16S rRNA) in the P-CW was 15.6 and 8.12 times higher than that of Mg-CW and A-CW, respectively, resulting in lower global warming potential. Tanking all factors into consideration, addition of peat could be an effective method to optimize the nutrient removal performance of Mg-CW.

Study on Adsorption Properties of Calcined Mg-Al Hydrotalcite for Sulfate Ion and Chloride Ion in Cement Paste.

In the marine environment, sulfate ions and chloride ions are abundant. Therefore, sulfate attack and chloride ion attack are common failure forms of marine concrete. Mg-Al hydrotalcite is a layered bimetallic hydroxide, which can be used as guest molecular adsorbent. In this experiment, we synthesized Mg-Al hydrotalcite, and the crystal state, surface morphology, and composition of this adsorbent were investigated by modern micro-analysis technology. Mg-Al hydrotalcite was added into the prepared target ion solution, to explore the influence of various factors on the adsorption performance of Mg-Al hydrotalcite, and then calcined Mg-Al hydrotalcite was added into cement paste, to study the mechanical properties and durability of the paste samples. The experimental results show that the optimum conditions for adsorption of chloride ions by calcined Mg-Al hydrotalcite are an adsorption time of 4 h, temperature of 35 °C, LDO (calcined Mg-Al hydrotalcite) dosage of 3.5 g/L, and a pH of 8. The adsorption effect of sulfate ion is best when the adsorption time is 6 h, the temperature is 35 °C, the dosage of LDO is 4 g/L, and the pH = 8. The optimal adsorption conditions of calcined Mg-Al hydrotalcite for chloride ion and sulfate ion are not completely the same, and the adsorption of these two ions in mixed solution shows competitive adsorption. Compared with the common paste specimens without Mg-Al hydrotalcite, the mechanical properties and deformation properties of cement specimens can be significantly improved by adding Mg-Al hydrotalcite.

Heterogeneous Hybrid Nanocomposite Based on Chitosan/Magnesia Hybrid Films: Ecofriendly and Recyclable Solid Catalysts for Organic Reactions.

Chitosan/magnesia hybrid films (CS-Mg) have been prepared via sol-gel process and employed as heterogeneous catalysts. An in situ generation of a magnesia network in the chitosan matrix was performed through hydrolysis/condensation reactions of magnesium ethoxide. The synthesized hybrid films were characterized using various analytical techniques, such as X-ray photo-electron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The hybrid films display excellent catalytic activities in Michael and Knoevenagel reactions via one pot or solvent-free approaches under microwave irradiation conditions. Chitosan/magnesia hybrid films, catalysed pyrimidine, benzochromene, coumarin and arylidene-malononitriles derivatives formation reactions occurred with highly efficient yields of 97%, 92%, 86% and 95% respectively. Due to the fact that the films are durable and insoluble in common organic solvents, they were easily separated and can be recycled up to five times without a considerable loss of their catalytic activity.

The Importance of Thermal Treatment on Wet-Kneaded Silica-Magnesia Catalyst and Lebedev Ethanol-to-Butadiene Process.

The Lebedev process, in which ethanol is catalytically converted into 1,3-butadiene, is an alternative process for the production of this commodity chemical. Silica-magnesia (SiO2-MgO) is a benchmark catalyst for the Lebedev process. Among the different preparation methods, the SiO2-MgO catalysts prepared by wet-kneading typically perform best owing to the surface magnesium silicates formed during wet-kneading. Although the thermal treatment is of pivotal importance as a last step in the catalyst preparation, the effect of the calcination temperature of the wet-kneaded SiO2-MgO on the Lebedev process has not been clarified yet. Here, we prepared and characterized in detail a series of wet-kneaded SiO2-MgO catalysts using varying calcination temperatures. We find that the thermal treatment largely influences the type of magnesium silicates, which have different catalytic properties. Our results suggest that the structurally ill-defined amorphous magnesium silicates and lizardite are responsible for the production of ethylene. Further, we argue that forsterite, which has been conventionally considered detrimental for the formation of ethylene, favors the formation of butadiene, especially when combined with stevensite.

Inhibition effects of long-term calcium-magnesia phosphate fertilizer application on Cd uptake in rice: Regulation of the iron-nitrogen coupling cycle driven by the soil microbial community.

Cadmium (Cd) pollution in paddy soil seriously endangers food safety production. To investigate the effects and microbiological mechanisms of calcium-magnesium-phosphate (CMP) fertilizer application on Cd reduction in rice, field experiments were conducted in Cd-contaminated paddy soil. Compared with conventional compound fertilizer, CMP fertilizer treatments inhibited Cd uptake through plant roots, significantly decreasing Cd content in rice grains from 0.340 to 0.062 mg/kg. Soil pH and total Ca, Mg and P contents increased after CMP fertilizer application, resulting in a further decrease in soil available Cd content from 0.246 to 0.181 mg/kg. Specific extraction analysis recorded a decrease in both available Fe content and the ratio of nitrate to ammonium nitrogen, indicating that the soil Fe-N cycle was affected by the addition of CMP fertilizer. This finding was also recorded using soil bacterial community sequencing, with CMP fertilizer promoting the progress of nitrate-dependent Fe-oxidation driven by Thiobacillus (1.60-2.83%) and subsequent dissimilatory nitrate reduction to ammonium (DNRA) driven by Ignavibacteriae (1.01-1.92%); Fe-reduction driven by Anaeromyxobacter (3.09-2.23%) was also inhibited. Our results indicate that CMP fertilizer application regulates the Fe-N coupling cycle driven by the soil microbial community to benefit remediation of Cd contaminated paddy soil.