CTAB-assisted fabrication of hierarchical flower-like magnesium oxide adsorbent for enhanced removal performance towards phosphate

In this work, a series of hierarchical flower-like magnesium oxide(MgO) adsorbents were successfully fabricated in a cetyltrimethylammonium bromide(CTAB) assisted solvothermal route using hexamethylenetetramine(HMTA) as a precipitating agent. Effects of CTAB feeding amount on the structure, morphology, pore structure, and corresponding adsorption behavior were investigated. The hierarchical gardenias flower-like MgO demonstrated a surface area of 336.54 m^(2)·g^(-1) at a minimum ratio of the CTAB/Mg^(2+)was 0.02 in the reaction system. The hierarchical MgO phosphate removal capacity was 348.32 mg·g^(-1), which followed the pseudo-second-order and Freundlich isotherm model obtained from the large surface area and appropriate pore size. The value of n also suggests the feasible nature of phosphate adsorption under the examined conditions. Indeed, this CTAB assisted solvothermal method can provide a new understanding to tune the desired properties of a material by merely adjusting the reaction parameters of MgO.

Preparation and property of self-sealed plasma electrolytic oxide coating on magnesium alloy

Plasma electrochemical oxidation (PEO) is a surface modification technology to form ceramic coatings on magnesium alloys However,its application is limited due to its defects.This work reports a novel preparation of in-situ sealing of PEO coatings by four-layer voltage and sol addition.The morphology and structure were characterized by scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDS),and X-ray diffractometer (XRD).Image-Pro Plus 6.0 was used to determine the porosity of the coating,which was decreased from 8.53%to 0.51%.Simultaneously,the coating thickness was increased by a factor of four.The anti-corrosion performance of each sample was evaluated using electrochemical tests,and the findings revealed that the corrosion current density of coatings (i_(corr)) of the samples were lowered from 9.152×10^(-2) to 6.152×10^(-4) mA·cm^(-2),and the total resistance (R_(T)) of the samples were enhanced from 2.19×10^(4) to 2.33×10^(5)Ω·cm^(2).The salt spray test used to simulate the actual environment showed that corrosion points appeared on the surface of the coating only at the 336 h.In addition,the mechanism of PEO self-sealing behavior was described in this article.

Green synthesis of three-dimensional magnesium ferrite/titanium dioxide/reduced graphene from Garcinia mangostana extract for crystal violet photodegradation and antibacterial activity

In this study,three-dimensional porous magnesium ferrite/titanium dioxide/reduced graphene oxide(Mg Fe_2O_(4)-GM/TiO_(2)/rGO(MGTG))was successfully synthesized via green and hydrothermal-supported co-precipitation methods using the extract of Garcinia mangostana(G.mangostana)as a reducing agent.The characterization results indicate the successful formation of the nano/micro Mg Fe_(2)O_(4)(MFO)and TiO_(2) on the structure of the reduced graphene oxide(rGO),which can also act as efficient support,alleviating the agglomeration of the nano/micro MFO and TiO_(2).The synergic effects of the adsorption and photodegradation activity of the material were investigated according to the removal of crystal violet(CV)under ultraviolet light.The effects of catalyst dosage,CV concentration,and p H on the CV removal efficiency of the MGTG were also investigated.According to the results,the CV photodegradation of the MGTG-200 corresponded to the pseudo-first-order kinetic model.The reusability of the material after 10 cycles also showed a removal efficiency of 92%.This happened because the materials can easily be recollected using external magnets.In addition,according to the effects of different free radicals·O_(2)^(-),h^(+),and·OH on the photodegradation process,the photocatalysis mechanism of the MGTG was also thoroughly suggested.The antibacterial efficiency of the MGTG was also evaluated according to the inhibition of the Gram-positive bacteria strain Staphylococcus aureus(S.aureus).Concurrently,the antibacterial mechanism of the fabricated material was also proposed.These results confirm that the prepared material can be potentially employed in a wide range of applications,including wastewater treatment and antibacterial activity.

Mg/MgO interfaces as efficient hydrogen evolution cathodes causing accelerated corrosion of additive manufactured Mg alloys:A DFT analysis

The corrosion rates of additive-manufactured Mg alloys are higher than their as-cast counterparts,possibly due to increased kinetics for the hydrogen evolution reaction on secondary phases,which may include oxide inclusions.Scanning Kelvin Probe Force Microscopy demonstrated that MgO inclusions could act as cathodes for Mg corrosion,but their low conductivity likely precludes this.However,the density of state calculations through density functional theory using hybrid HSE06 functional revealed overlapping electronic states at the Mg/MgO interface,which facilitates electron transfers and participates in redox reactions.Subsequent determination of the hydrogen absorption energy at the Mg/MgO interface reveals it to be an excellent catalytic site,with HER being found to be a factor of 23x more efficient at the interface than on metallic Mg.The results not only support the plausibility of the Mg/MgO interface being an effective cathode to the adjacent anodic Mg matrix during corrosion but also contribute to the understanding of the enhanced cathodic activities observed during the anodic dissolution of magnesium.

Effect of low concentration electrolytes on the formation and corrosion resistance of PEO coatings on AM50 magnesium alloy

In this paper,the formation process,morphology,and electrochemical performance of PEO coatings on AM50 magnesium alloy prepared in low concentration phosphate,aluminate,and phosphate-aluminate electrolytes were systematically studied.The results show that the coatings prepared from the phosphate electrolytes have a higher thickness and better corrosion resistance properties compared to the other electrolytes.The coatings prepared from low concentration phosphate-aluminate mixed electrolytes have slightly thinner thickness,a similar coating structure and an order of magnitude lower value of electrochemical impedance compared with phosphate electrolyte coatings.The Coatings prepared from low concentration aluminate electrolytes have the lowest thickness and the worst corrosion resistance properties which gets close to corrosion behavior of the bare AM50 under the same test conditions.Considering application,coatings prepared from single low concentration phosphate electrolytes and low concentration phosphate-aluminate electrolytes have greater potential than single low concentration aluminate coatings.However,reducing the electrolyte concentrations of coating forming ions too much has negative influence on the coating growth rate.

Improving corrosion resistance of additively manufactured WE43 magnesium alloy by high temperature oxidation for biodegradable applications

Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.

NiO-Doped Fe_(2)O_(3)/MgO Properties for the Chemical Looping Oxidative Dehydrogenation of Ethane

Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for ethylene preparation.Fe_(2)O_(3)/MgO oxygen carrier was prepared using the co-precipitation method.The influence of added NiO and its different loadings on Fe_(2)O_(3)/MgO were investigated.Then,a series of oxygen carriers were applied in the CL-ODH of the ethane cycle system.Brunauer-Emmett-Teller(BET),X-ray diffractometry(XRD),X-ray photoelection spectroscopy(XPS),and H2-temperature programmed reduction(TPR)were used to characterize the physicochemical properties of these oxygen carriers.It was confirmed that an interaction between NiO and Fe_(2)O_(3) occurred based on the XPS and H2-TPR results.Based on the CL-ODH activity performance tests conducted in a fixed-bed reactor,it was revealed that ethylene selectivity was significantly improved after NiO addition.Fe_(2)O_(3)-10%NiO/MgO showed the best activity performance with 93%ethane conversion and 50%ethylene selectivity at a reaction temperature of 650℃,atmospheric pressure,and space velocity of 7500 mL/(g·h).

掺杂氧化钇和富镧钐渣对连铸水口MgO-C耐火材料性能的影响

本研究分别考察了氧化钇(Y_(2)O_(3) )和富镧钐渣掺杂量对MgO-C耐火材料微观结构、烧结性能、力学性能和抗稀土钢侵蚀性能的影响。结果表明,Y_(2)O_(3) 和富镧钐渣通过与SiO_(2)和Al_(2)O_(3)反应而生成稀土硅酸盐和稀土铝酸盐,促进材料烧结,提高材料致密性。随着Y_(2)O_(3) 和富镧钐渣掺杂量增大,MgO-C耐火材料的体积密度、抗折强度和耐压强度均先增大后减小,而显气孔率的变化趋势相反。当Y_(2)O_(3) 和富镧钐渣的掺杂量分别为0.5%时,MgO-C耐火材料的体积密度分别为2.87 g/cm^(3)和2.85 g/cm^(3),显气孔率分别为9.6%和10.2%,抗折强度分别为7.6 MPa和6.8 MPa,抗压强度分别为46.4 MPa和41.2 MPa,致密性和常温力学性能提高的幅度最大,抗Ce基稀土钢侵蚀性能相比未掺杂稀土氧化物的试样分别提高了7.6%和10.2%。

含BAG-nMgO的新型牙科复合树脂的抗菌及再矿化性能研究

目的:联合应用生物活性玻璃(BAG)和纳米氧化镁(nMgO)改性牙科光固化复合树脂,以获得兼备优良的抗菌性及再矿化性能的新型牙科复合树脂。方法:将不同含量的BAG(2.5 wt%、7.5 wt%、12.5 wt%)和2.5 wt%nMgO引入牙科光固化复合树脂中,制备成含BAG-nMgO的实验树脂,并以卡瑞斯玛复合树脂作为对照。通过菌落计数、代谢活性分析(MTT)和活/死细菌染色,评价实验树脂的抗变形链球菌(S.mutans)能力;将脱矿人牙牙本质片及实验树脂在模拟体液(SBF)中浸泡21 d后,通过扫描电子显微镜(SEM)和X射线能谱仪(EDS)观察分析脱矿牙本质表面形貌和元素组成,评估实验树脂再矿化特性;通过万能试验机、维氏硬度仪等测试树脂的固化深度、压缩强度及维氏硬度。结果:实验组树脂的抗S.mutans活性显著高于卡瑞斯玛对照组,且与BAG的含量相关;当BAG添加量为7.5 wt%时,脱矿牙本质开始矿化;BAG添加比例为12.5 wt%时,可见厚的矿化层,牙本质小管几乎被完全封闭;实验组的固化深度均显著高于卡瑞斯玛,维氏硬度优于或与其相近,随着BAG比例的增加,各实验组的固化深度、压缩强度间无显著性差异。结论:BAG和nMgO的联合应用提高了实验树脂的抗菌性,并赋予其再矿化性能。新型复合树脂预期可减少细菌入侵和促进早期龋损的再矿化。本研究为新型多功能复合树脂的研究开发提供了理论依据和研究基础。

Screening of MgO- and CeO_2-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C_(2+) Hydrocarbons

The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.

Nickel catalysts supported on MgO with different specific surface area for carbon dioxide reforming of methane

In this paper, three kinds of MgO with different specific surface area were prepared, and their effects on the catalytic performance of nickel catalysts for the carbon dioxide reforming of methane were investigated. The results showed that MgO support with the higher specific surface area led to the higher dispersion of the active metal, which resulted in the higher initial activity. On the other hand, the specific surface area of MgO materials might not be the dominant factor for the basicity of support to chemisorb and activate CO2, which was another important factor for the performance of catalysts. Herein, Ni/MgO(CA) catalyst with proper specific surface area and strong ability to activate CO2exhibited stable catalytic property and the carbon species deposited on the Ni/MgO(CA) catalyst after 10 h of reaction at 650 ?C were mainly activated carbon species.

Influence of MgO contents on silica supported nano-size gold catalyst for carbon monoxide total oxidation

A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, O2 temperature-programmed desorption （O2-TPD）, and inductively coupled with plasma atomic emission spectroscopy （ICP-AES） techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO （Mg/SiO2 weight ratio） shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.

Effects of Calcination Temperature of Boron-Containing Magnesium Oxide Raw Materials on Properties of Magnesium Phosphate Cement as a Biomaterial

A new magnesium phosphate bone cement （MPBC） was prepared as a byproduct of boroncontaining magnesium oxide （B-MgO） after extracting Li2CO3 from salt lakes. We analyzed the elementary composition of the B-MgO raw materials and the effects of calcination temperature on the performance of MPBC. The phase composition and microstructure of the B-MgO raw materials and the hydration products （KMgPO4.6H2O） of MPBC were analyzed by X-ray diffraction and scanning electron microscopy. The results showed that ionic impurities and the levels of toxic elements were sufficiently low in B-MgO raw materials to meet the medical requirements for MgO （Chinese Pharmacopeia, 2O10 Edition） and for hydroxyapatite surgical implants （GB23101.1-2O08）. The temperature of B-MgO calcination had a marked influence on the hydration and hardening of MPBC pastes. Increasing calcination temperature prolonged the time required for the MPBC slurry to set, significantly decreased the hydration temperature, and prolonged the time required to reach the highest hydration temperature. However, the compressive strength of hardened MPBC did not increase with higher calcination temperatures. In the 900-1 000 ~C temperature range, the hardened MPBC had a higher compressive strength. Imaging analysis suggested that the setting time and the highest hydration temperature of MPBC pastes were dependent on the size and crystal morphology of the B-MgO materials. The production and microstructure compactness of KMgPOa＇6H2O, the main hydration product, determined the compressive strength.

Effect of Magnesium on Nitric Oxide Synthase of Neurons in Cortex during Early Period of Cerebral Ischemia

Summary: To investigate the effect of magnesium on nitric oxide synthase (NOS) of neurons in cortex during early cerebral ischemic period, a rat model of middle cerebral artery occlusion (MCAO) was established. The results showed that the NOS activity of neurons in cortex was in- creased significantly at 15 min after MCAO, reached its peak at 30 min after MCAO and returned to normal levels at 60 min after MCAO. The NOS activity of neurons in the magnesium-treated group was decreased significantly as compared with that in the ischemic group at 15 min and 30 ruin after MCAO respectively. The results suggested that magnesium could inhibit the elevated NOS activity of neurons in cortex induced by cerebral ischemia.

Synthesis of cation exchange resin-supported iron and magnesium oxides/hydroxides composite for nitrate removal in water

In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.

Effect of current density on corrosion resistance of micro-arc oxide coatings on magnesium alloy

Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.

Characterization of oxide films formed on magnesium alloys using bipolar pulse microarc oxidation in phosphate solutions

The surface morphology and chemical composition of the oxide films formed on pure magnesium and AZ91D alloy in aqueous electrolytes which contained sodium hexafluorinealuminate（Na3AlF6）, potassium hydroxide （KOH）, sodium hexametahposphate（（NaPO3）6）, and triethanolamine were investigated by X-ray diffraction（XRD）, scanning electron microscope（SEM） and energy dispersive spectroscopy（EDX）. The results show that the input of the negative pulse has great influences on the quantity and the appearance of the microdischarges. Three types of pores can be distinguished on the surface of the oxide film and their size ranges are 0.5-1μm, 1-2μm and 4-7μm, respectively. A few microcracks are seen around the large pores. There exists a remarkable fluoride- enriched zone of about 4-6μm for pure magnesium and 3-5μm for AZ91D alloy at the coating/substrate interface.

Serum magnesium concentration in children with functional constipation treated with magnesium oxide

AIM:To determine whether hypermagnesemia recently reported in adult patients possibly develops in children with functional constipation taking daily magnesium oxide.METHODS:We enrolled 120 patients (57 male and 63 female) aged 1-14 years old (median:4.7 years) with functional constipation from 13 hospitals and two private clinics.All patients fulfilled the Rome Ⅲ criteria for functional constipation and were treated with daily oral magnesium oxide for at least 1 mo.The median treatment dose was 600 (500-800) mg/d.Patients were assessed by an interview and laboratory examination to determine possible hypermagnesemia.Serum magnesium concentration was also measured in sex-and agematched control subjects (n=38).RESULTS:In the constipation group,serum magnesium concentration [2.4 (2.3-2.5) mg/dL,median and interquartile range] was significantly greater than that of the control group [2.2 (2.0-2.2) mg/dL] (P < 0.001).The highest value was 3.2 mg/dL.Renal magnesium clearance was significantly increased in the constipation group.Serum magnesium concentration in the constipation group decreased significantly with age (P < 0.01).There was no significant correlation between the serum level of magnesium and the duration of treatment with magnesium oxide or the daily dose.None of the patients had side effects associated with hypermagnesemia.CONCLUSION:Serum magnesium concentration increased significantly,but not critically,after daily treatment with magnesium oxide in constipated children with normal renal function.