Hydroxyapatite is used extensively in hard tissue repair due to its biocompatibility and similarity to biological apatite, the mineral component of bone. It differs subtly in composition from biological apatite which contains other ions such as magnesium, zinc, carbonate and silicon (believed to play biological roles). Traditional methods of hydroxyapatite synthesis are time consuming and require strict reaction parameter control. This paper outlines synthesis of magnesium substituted hydroxyapatite using simple microwave irradiation of precipitated suspensions. Microwave irradiation resulted in a drastic decrease in ageing times of amorphous apatitic phases. Time taken to synthesize hydroxyapatite (which remained stable upon heat treatment at 900°C for 1h) reduced twelve folds (to 2h) as compared to traditionally required times. The effects of increasing magnesium concentration in the precursors on particle size, surface area, phase-purity, agglomeration and thermal stability, were observed using scanning electron microscopy, BET surface area analysis, X-ray diffraction and photo acoustic Fourier transform infra-red spectroscopy. Porous agglomerates were obtained after a brief heat-treatment (1h) at 900°C.
The present study addressed the synthesis of a bi-layered nanostructured fluorine-doped hydroxyapatite (nFHA)/polycaprolactone (PCL) coating on Mg-2Zn-3Ce alloy via a combination of electrodeposition (ED) and dip-coating methods. The nFHA/PCL composite coating is composed of a thick (70-80 μm) and porous layer of PCL that uniformly covered the thin nFHA film (8-10 μm) with nanoneedle-like microstructure and crystallite size of around 70-90 nm. Electrochemical measurements showed that the nFHA/PCL composite coating presented a high corrosion resistance (R(p)=2.9×10(3) kΩ cm(2)) and provided sufficient protection for a Mg substrate against galvanic corrosion. The mechanical integrity of the nFHA/PCL composite coatings immersed in SBF for 10 days showed higher compressive strength (34% higher) compared with the uncoated samples, indicating that composite coatings can delay the loss of compressive strength of the Mg alloy. The nFHA/PCL coating indicted better bonding strength (6.9 MPa) compared to PCL coating (2.2 MPa). Immersion tests showed that nFHA/PCL composite-coated alloy experienced much milder corrosion attack and more nucleation sites for apatite compared with the PCL coated and uncoated samples. The bi-layered nFHA/PCL coating can be a good alternative method for the control of corrosion degradation of biodegradable Mg alloy for implant applications.
Polyhydroxybutyrate (PHB)/polycaprolactone (PCL)/stearate Mg-Al layered double hydroxide (LDH) nanocomposites were prepared via solution casting intercalation method. Coprecipitation method was used to prepare the anionic clay Mg-Al LDH from nitrate salt solution. Modification of nitrate anions by stearate anions between the LDH layers via ion exchange reaction. FTIR spectra showed the presence of carboxylic acid (COOH) group which indicates that stearate anions were successfully intercalated into the Mg-Al LDH. The formation of nanocomposites only involves physical interaction as there are no new functional groups or new bonding formed. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the mixtures of nanocomposites are intercalated and exfoliated types. XRD results showed increasing of basal spacing from 8.66 to 32.97 Å in modified stearate Mg-Al LDH, and TEM results revealed that the stearate Mg-Al LDH layers are homogeneously distributed in the PHB/PCL polymer blends matrix. Enhancement in 300% elongation at break and 66% tensile strength in the presence of 1.0 wt % of the stearate Mg-Al LDH as compare with PHB/PCL blends. Scanning electron microscopy (SEM) proved that clay improves compatibility between polymer matrix and the best ratio 80PHB/20PCL/1stearate Mg-Al LDH surface is well dispersed and stretched before it breaks.
A new effective RF tar thermocatalytic treatment process with low energy intensive has been proposed to remove tar from biomass gasification. Toluene and naphthalene as biomass tar model compounds were removed via both thermal and catalytic treatment over a wide temperature range from 850 °C to 1200 °C and 450 °C to 900 °C, respectively at residence time of 0-0.7 s. Thermal characteristics of the new technique are also described in this paper. This study clearly clarified that toluene was much easier to be removed than naphthalene. Soot was found as the final product of thermal treatment of the tar model and completely removed during catalytic treatment. Radical reactions generated by RF non-thermal effect improve the tar removal. The study showed that Y-zeolite has better catalytic activity compared to dolomite on toluene and naphthalene removal due to its acidic nature and large surface area, even at lower reaction temperature of about 550 °C.
Published data on oxalate poisoning in domestic animals are reviewed, with a focus on tolerance and performance. Oxalic acid is one of a number of anti-nutrients found in forage. It can bind with dietary calcium (Ca) or magnesium (Mg) to form insoluble Ca or Mg oxalate, which then may lead to low serum Ca or Mg levels as well as to renal failure because of precipitation of these salts in the kidneys. Dietary oxalate plays an important role in the formation of Ca oxalate, and a high dietary intake of Ca may decrease oxalate absorption and its subsequent urinary excretion. Oxalate-rich plants can be supplemented with other plants as forage for domestic animals, which may help to reduce the overall intake of oxalate-rich plants. Non-ruminants appear to be more sensitive to oxalate than ruminants because in the latter, rumen bacteria help to degrade oxalate. If ruminants are slowly exposed to a diet high in oxalate, the population of oxalate-degrading bacteria in the rumen increases sufficiently to prevent oxalate poisoning. However, if large quantities of oxalate-rich plants are eaten, the rumen is overwhelmed and unable to metabolize the oxalate and oxalate-poisoning results. Based on published data, we consider that <2.0% soluble oxalate would be an appropriate level to avoid oxalate poisoning in ruminants, although blood Ca level may decrease. In the case of non-ruminants, <0.5% soluble oxalate may be acceptable. However, these proposed safe levels of soluble oxalate should be regarded as preliminary. Further studies, especially long-term studies, are needed to validate and improve the recommended safe levels in animals. This review will encourage further research on the relationships between dietary oxalate, other dietary factors and renal failure in domestic animals.
In the current study, a sol-gel-synthesized tricalcium magnesium silicate powder was coated on Ti-6Al-4V alloys using plasma spray method. Composition of feed powder was evaluated by X-ray diffraction technique before and after the coating process. Scanning electron microscopy and atomic force microscopy were used to study the morphology of coated substrates. The corrosion behaviors of bare and coated Ti-6Al-4V alloys were examined using potentiodynamic polarization test and electrochemical impedance spectroscopy in stimulated body fluids. Moreover, bare and coated Ti-6Al-4V alloys were characterized in vitro by culturing osteoblast and mesenchymal stem cells for several days. Results demonstrated a meaningful improvement in the corrosion resistance of Ti-6Al-4V alloys coated with tricalcium magnesium silicate compared with the bare counterparts, by showing a decrease in corrosion current density from 1.84 μA/cm2 to 0.31 μA/cm2. Furthermore, the coating substantially improved the bioactivity of Ti-6Al-4Valloys. Our study on corrosion behavior and biological response of Ti-6Al-4V alloy coated by tricalcium magnesium silicate proved that the coating has considerably enhanced safety and applicability of Ti-6Al-4V alloys, suggesting its potential use in permanent implants and artificial joints.
This study employs a computational approach to analyse the impact of morphological changes on the structural properties of biodegradable porous Mg subjected to a dynamic immersion test for its application as a bone scaffold. Porous Mg was immersed in a dynamic immersion test for 24, 48, and 72 h. Twelve specimens were prepared and scanned using micro-CT and then reconstructed into a 3D model for finite element analysis. The structural properties from the numerical simulation were then compared to the experimental values. Correlations between morphological parameters, structural properties, and fracture type were then made. The relative losses were observed to be in agreement with relative mass loss done experimentally. The degradation rates determined using exact (degraded) surface area at particular immersion times were on average 20% higher than the degradation rates obtained using original surface area. The dynamic degradation has significantly impacted the morphological changes of porous Mg in volume fraction, surface area, and trabecular separation, which in turn affects its structural properties and increases the immersion time.
A study was conducted in an oil palm plantation in Peninsular Malaysia to elucidate the effects of applying Magnesium Rich Synthetic Gypsum (MRSG), a by-product of chemical plant, on the chemical properties of soil, the uptake of heavy metals by the palm trees, the oil quality and its impact on the surrounding environment. The results showed that MRSG application onto soil cropped to oil palm could bring positive impact in terms of soil chemical properties and oil palm production. The quality of the oil was not significantly affected by the continuous MRSG application as shown by the low heavy metals and trace elements of concern content (Cu: 0.062 mg/kg; Fe: 2.10 mg/kg; Mn: 1.93 mg/kg; Pb: 0.006 mg/kg; Zn: 0.103 mg/kg; Cr: 0.354 mg/kg; Ni: 0.037 mg/kg). From the I-geochem index, the soil was found to have values ranging from -3.81 to -1.03 which is considered as uncontaminated. Further, its application did not result in negative impact on the surrounding environment; hence, the quality of the soil and surface water in the plantation and/or the surrounding area remained intact. Phytotoxic elements in the oil palm tissue (As: 0.12 mg/kg; Se: 0.05 mg/kg; Zn: 1.48 mg/kg; Ce: 0.47 mg/kg; La: 0.26 mg/kg; Sr: 3.03 mg/kg) and cytotoxic elements in the oil were below the acceptable limit. Based on the results of the Environmental Monitoring out during the period of the study, it was concluded that application of the by-product of the chemical plant as a source of Mg to enhance soil fertility in the oil palm plantation was considered safe and sustainable. The effects of applying MRSG and Chinese kieserite was almost similar. So, MRSG can be used as a possible source of Mg to replace Chinese kieserite for oil palm production on the Ultisols in Peninsular Malaysia.
In this work, analysis of ion transport parameters of polymer blend electrolytes incorporated with magnesium trifluoromethanesulfonate (Mg(CF3SO3)2) was carried out by employing the Trukhan model. A solution cast technique was used to obtain the polymer blend electrolytes composed of chitosan (CS) and poly (2-ethyl-2-oxazoline) (POZ). From X-ray diffraction (XRD) patterns, improvement in amorphous phase for the blend samples has been observed in comparison to the pure state of CS. From impedance plot, bulk resistance (Rb) was found to decrease with increasing temperature. Based on direct current (DC) conductivity (σdc) patterns, considerations on the ion transport models of Arrhenius and Vogel-Tammann-Fulcher (VTF) were given. Analysis of the dielectric properties was carried out at different temperatures and the obtained results were linked to the ion transport mechanism. It is demonstrated in the real part of electrical modulus that chitosan-salt systems are extremely capacitive. The asymmetric peak of the imaginary part (Mi) of electric modulus indicated that there is non-Debye type of relaxation for ions. From frequency dependence of dielectric loss (ε″) and the imaginary part (Mi) of electric modulus, suitable coupling among polymer segmental and ionic motions was identified. Two techniques were used to analyze the viscoelastic relaxation dynamic of ions. The Trukhan model was used to determine the diffusion coefficient (D) by using the frequency related to peak frequencies and loss tangent maximum heights (tanδmax). The Einstein-Nernst equation was applied to determine the carrier number density (n) and mobility. The ion transport parameters, such as D, n and mobility (μ), at room temperature, were found to be 4 × 10-5 cm2/s, 3.4 × 1015 cm-3, and 1.2 × 10-4 cm2/Vs, respectively. Finally, it was shown that an increase in temperature can also cause these parameters to increase.
This study focused on improving the producer gas quality using radio frequency (RF) tar thermocatalytic treatment reactor. The producer gas containing tar, particles and water was directly passed at a particular flow rate into the RF reactor at various temperatures for catalytic and thermal treatments. Thermal treatment generates higher heating value of 5.76 MJ Nm(-3) at 1200°C. Catalytic treatments using both dolomite and Y-zeolite provide high tar and particles conversion efficiencies of about 97% on average. The result also showed that light poly-aromatic hydrocarbons especially naphthalene and aromatic compounds particularly benzene and toluene were still found even at higher reaction temperatures. Low energy intensive RF tar thermocatalytic treatment was found to be effective for upgrading the producer gas quality to meet the end user requirements and increasing its energy content.
The synthesis of fatty acid methyl esters (FAME) as a substitute to petroleum diesel was investigated in this study from crude jatropha oil (CJO), a non-edible, low-cost alternative feedstock, using aluminium modified heterogeneous basic oxide (Mg-Zn) catalyst. The transesterification reaction with methanol to methyl esters yielded 94% in 6h with methanol-oil ratio of 11:1, catalyst loading of 8.68 wt.% at 182°C and the properties of CJO fuel produced were determine and found to be comparable to the standards according to ASTM. In the range of experimental parameters investigated, it showed that the catalyst is selective to production of methyl esters from oil with high free fatty acid (FFA) and water content of 7.23% and 3.28%, respectively in a single stage process. Thus, jatropha oil is a promising feedstock for methyl ester production and large scale cultivation will help to reduce the product cost.
Fatty acid methyl ester was produced from used vegetable cooking oil using Mg(1-)(x) Zn(1+)(x)O(2) solid catalyst and the performance monitored in terms of ester content obtained. Used vegetable cooking oil was employed to reduce operation cost of biodiesel. The significant operating parameters which affect the overall yield of the process were studied. The highest ester content, 80%, was achieved with the catalyst during 4h 15 min reaction at 188°C with methanol to oil ratio of 9:1 and catalyst loading of 2.55 wt% oil. Also, transesterification of virgin oil gave higher yield with the heterogeneous catalyst and showed high selectivity towards ester production. The used vegetable cooking oil did not require any rigorous pretreatment. Catalyst stability was examined and there was no leaching of the active components, and its performance was as good at the fourth as at the first cycle.
An organic solvent-tolerant S5 lipase was purified by affinity chromatography and anion exchange chromatography. The molecular mass of the lipase was estimated to be 60 kDa with 387 purification fold. The optimal temperature and pH were 45 degrees C and 9.0, respectively. The purified lipase was stable at 45 degrees C and pH 6-9. It exhibited the highest stability in the presence of various organic solvents such as n-dodecane, 1-pentanol, and toluene. Ca2+ and Mg2+ stimulated lipase activity, whereas EDTA had no effect on its activity. The S5 lipase exhibited the highest activity in the presence of palm oil as a natural oil and triolein as a synthetic triglyceride. It showed random positional specificity on the thin-layer chromatography.
This article reports the in vitro degradation and cytotoxicity assessment of Zn-3Mg alloy developed for biodegradable bone implants. The alloy was prepared using casting, and its microstructure was composed of Mg2Zn11 intermetallic phase distributed within a Zn-rich matrix. The degradation assessment was done using potentiodynamic polarization and electrochemical impedance spectrometry. The cell viability and the function of normal human osteoblast cells were assessed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and alkaline phosphatase extracellular enzyme activity assays. The results showed that the degradation rate of the alloy was slower than those of pure Zn and pure Mg due to the formation of a high polarization resistance oxide film. The alloy was cytocompatible with the normal human osteoblast cells at low concentrations (<0.5 mg/mL), and its alkaline phosphatase activity was superior to pure Mg. This assessment suggests that Zn-3Mg alloy has the potential to be developed as a material for biodegradable bone implants, but the toxicity limit must be carefully observed.
Layered double hydroxide of Mg-Al-carbonate system (MACH) was prepared and its heat-treated product (MACHT) was obtained by calcination at 500 degrees C. The resulting materials were used as an adsorbent for removal of color from synthetic textile wastewater (STW) and textile wastewater (TWW). Batch kinetic study showed that these materials are an efficient adsorbent for textile dye. The maximum adsorption capacities between 16 to 32 mg of dyes per g of adsorbent was obtained by fitting the adsorption data to the Langmuir adsorption Isotherm. It was found that the adsorption capacity of MACHT is higher than MACH.
Plasticized magnesium ion conducting polymer blend electrolytes based on chitosan (CS): polyvinyl alcohol (PVA) was synthesized with a casting technique. The source of ions is magnesium triflate Mg(CF3SO3)2, and glycerol was used as a plasticizer. The electrical and electrochemical characteristics were examined. The outcome from X-ray diffraction (XRD) examination illustrates that the electrolyte with highest conductivity exhibits the minimum degree of crystallinity. The study of the dielectric relaxation has shown that the peak appearance obeys the non-Debye type of relaxation process. An enhancement in conductivity of ions of the electrolyte system was achieved by insertion of glycerol. The total conductivity is essentially ascribed to ions instead of electrons. The maximum DC ionic conductivity was measured to be 1.016 × 10-5 S cm-1 when 42 wt.% of plasticizer was added. Potential stability of the highest conducting electrolyte was found to be 2.4 V. The cyclic voltammetry (CV) response shows the behavior of the capacitor is non-Faradaic where no redox peaks appear. The shape of the CV response and EDLC specific capacitance are influenced by the scan rate. The specific capacitance values were 7.41 F/g and 32.69 F/g at 100 mV/s and 10 mV/s, respectively. Finally, the electrolyte with maximum conductivity value is obtained and used as electrodes separator in the electrochemical double-layer capacitor (EDLC) applications. The role of lattice energy of magnesium salts in energy storage performance is discussed in detail.
A study was conducted to determine the impact of applying different sources of Mg, namely kieserite, ground magnesium limestone (GML) and Mg-rich synthetic gypsum (MRSG) on an acid tropical soil, oil palm growth and production. Besides high amount of Mg and Ca, MRSG contains S. Exchangeable Ca in the untreated soil of the plantation was 0.64 cmolc kg-1, but its critical level to sustain oil palm growth was 0.9 cmolc kg-1. MRSG was applied in the plantation as Mg-fertilizer; however, since Ca is also a limiting nutrient, oil palm growth was correlated (r = 0.69) with Ca supplied by the MRSG. Mg needed to sustain oil palm production is normally supplied by kieserite. Its requirement can be met at a lower cost compared to that of the kieserite by using MRSG. Due to MRSG treatment, exchangeable Ca in the soil increased steadily to satisfy the requirement of oil palm for fruit bunches production. From the glasshouse and field study, it was observed that MRSG applied at 1.5 times the recommended rate gave results comparable to that of the kieserite. MRSG treatment resulted in the increase of soil pH to >5 that precipitated Al3+ as inert Al-hydroxides, which eventually enhanced oil palm seedlings growth. Thus, MRSG can also replace GML to increase soil pH and satisfy the Ca and Mg requirement of oil palm. It can be concluded that MRSG has the potential to be used as a source of Mg as well as Ca for oil palm grown on acidic soil.
The primary role of bone tissue engineering is to reconcile the damaged bones and facilitate the speedy recovery of the injured bones. However, some of the investigated metallic implants suffer from stress-shielding, palpability, biocompatibility, etc. Consequently, the biodegradable scaffolds fabricated from polymers have gathered much attention from researchers and thus helped the tissue engineering sector by providing many alternative materials whose functionality is similar to that of natural bones. Herein, we present the fabrication and testing of a novel composite, magnesium (Mg)-doped hydroxyapatite (HAp) glazed onto polylactic acid (PLA) scaffolds where polyvinyl alcohol (PVA) used as a binder. For the composite formation, Creality Ender-3 pro High Precision 3D Printer with Shape tool 3D Technology on an FSD machine operated by Catia design software was employed. The composite has been characterized for the crystallinity (XRD), surface functionality (FTIR), morphology (FESEM), biocompatibility (hemolytic and protein absorption), and mechanical properties (stress-strain and maximum compressive strength). The powder XRD analysis confirmed the semicrystalline nature and intact structure of HAp even after doping with Mg, while FTIR studies for the successful formation of Mg-HAp/PVA@PLA composite. The FESEM provided analysis indicated for the 3D porous architecture and well-defined morphology to efficiently transport the nutrients, and the biocompatibility studies are supporting that the composite for blood compatible with the surface being suitable enough for the protein absorption. Finally, the composite's antibacterial activity (against Staphylococcus aureus and Escherichia coli) and the test of mechanical properties supported for the enhanced inhibition of active growth of microorganisms and maximum compressive strength, respectively. Based on the research outcomes of biocompatibility, antibacterial activity, and mechanical resistance, the fabricated Mg-HAp/PVA@PLA composite suits well as a promising biomaterial platform for orthopedic applications by functioning towards the open reduction internal fixation of bone fractures and internal repairs.
To develop a novel granular adsorbent to remove arsenic and antimony from water, calcined Mg/Al-layered double-hydroxide (CLDH)-incorporated polyethersulfone (PES) granular adsorbents (PES-LDH) were prepared using a core-shell method having 25% PES in an N,N-dimethylformamide solution. The PES-LDH displayed a spherical hollow shape having a rough surface and the average particle size of 1-2 mm. On the PES-LDH surface, nanosized CLDH (100-150 nm) was successfully immobilized by consolidation between PES and CLDH. The adsorption of Sb(V) by PES-LDH was found to be more favorable than for As(V), with the maximum adsorption capacity of As(V) and Sb(V) being 7.44 and 22.8 mg/g, respectively. The regeneration results indicated that a 0.5 M NaOH and 5 M NaCl mixed solution achieved an 80% regeneration efficiency in As(V) adsorption and desorption. However, the regeneration efficiency of Sb(V) gradually decreased due to its strong binding affinity, even though the PES-LDH showed much higher Sb(V) adsorption efficiency than As(V). This study suggested that PES-LDH could be a promising granular adsorbent for the remediation of As(V) and Sb(V) contained in wastewater.
The intercalation of cetirizine into two types of layered double hydroxides, Zn/Al and Mg/Al, has been investigated by the ion exchange method to form CTZAN and CTMAN nanocomposites, respectively. The basal spacing of the nanocomposites were expanded to 31.9 Å for CTZAN and 31.2 Å for CTMAN, suggesting that cetirizine anion was intercalated into Layered double hydroxides (LDHs) and arranged in a tilted bilayer fashion. A Fourier transform infrared spectroscopy (FTIR) study supported the formation of both the nanocomposites, and the intercalated cetirizine is thermally more stable than its counterpart in free state. The loading of cetirizine in the nanocomposite was estimated to be about 57.2% for CTZAN and 60.7% CTMAN. The cetirizine release from the nanocomposites show sustained release manner and the release rate of cetirizine from CTZAN and CTMAN nanocomposites at pH 7.4 is remarkably lower than that at pH 4.8, presumably due to the different release mechanism. The inhibition of histamine release from RBL2H3 cells by the free cetirizine is higher than the intercalated cetirizine both in CTZAN and CTMAN nanocomposites. The viability in human Chang liver cells at 1000 μg/mL for CTZAN and CTMAN nanocomposites are 74.5 and 91.9%, respectively.