Co-precipitation of Cd with struvite during phosphorus recovery.

During the struvite recovery process, Cd, a hazardous metal commonly found in waste streams, can be sequestered by struvite. This study investigated the influence of Cd2+ on the precipitation of struvite. Quantitative X-ray diffraction (QXRD) results showed that the purity of struvite decreased from 99.1% to 73.6% as Cd concentration increased from 1 to 500 µM. Scanning electron microscopy (SEM) revealed a roughened surface of struvite, and X-ray photoelectron spectroscopy (XPS) analysis indicated that the peak area ratio of Cd-OH increased from 19.4% to 51.3%, while the area ratio of Cd-PO4 decreased from 86.6% to 48.7% as Cd concentrations increased from 10 to 500 µM. The findings suggested that Cd2+ disrupted the crystal growth of struvite, and mainly combined with -OH and -PO4 to form amorphous Cd-bearing compounds co-precipitated with struvite. Additionally, Mg-containing amorphous phases were formed by incorporating Mg2+ with -OH and -PO4 during struvite formation.

Recovering struvite from livestock wastewater by fluidized-bed homogeneous crystallization as a pre-treatment process to sludge co-digestion.

Livestock wastewater can contain high levels of phosphates and trace amounts of various ionic species harming the environment and human health. These ions can be successfully removed from livestock effluent and recovered in a non-toxic crystal form via crystallization. The fluidized bed homogeneous crystallization (FBHC) technology is a cutting-edge pretreatment method that removes phosphate and ammonium by crystallizing struvite. The findings demonstrated a 37% removal for ammonium solutions alone, 38% with copper, 35% with zinc, and 33% when copper and zinc were present, while the crystallization efficiency was achieved at 35%, 33% with copper, 28% with zinc, and 26% with copper and zinc. For phosphate-containing solutions, 95% was removed, 81% with copper, 96% with zinc, and 88% with copper and zinc. Similarly, crystallization efficiency was attained at 87%, 60% with copper, 94% with zinc, and 81% when copper and zinc were combined with phosphates. For ammonium solutions, copper and zinc reduced the removal and crystallization efficiency at constant pH and increased at increasing pH. For phosphate solutions, the removal and crystallization efficiencies increased at increasing pH. However, zinc ions resulted in the highest removal, and crystallization efficiency for phosphate solutions was attained. Based on SEM, EDS, XRD, and XPS analyses, the peaks revealed the presence of struvite in the form of magnesium ammonium phosphate.

A modelling approach to prepare synthetic urine for struvite precipitation studies.

Nutrient recovery from wastewater is an effective strategy to prevent eutrophication and provide value for the treatment process. Human urine is a small but highly nutrient-rich stream in the total flux of domestic wastewater from which struvite (MgNH4PO4.6H2O) could be recovered and used as a fertiliser. Consequently, synthetic urine was used in most struvite precipitation studies, due to biohazard issues in real human urine. A modelling approach was developed to formulate synthetic urine recipes based on elemental urine composition, using matrix solving strategy to select and quantify chemical salts for synthetic urine preparation. The model also included mass balance, chemical speciation, and equilibrium dissociation expression for solution thermodynamics predictions in the formulated urine. In this study, synthetic solutions of fresh and stored urine were assessed with this model using Engineering Equation Solver (EES) software to calculate the quantity of salts, pH, ionic strength, and struvite saturation index. Simulation results in EES were successfully verified using PHREEQC simulations, while model validation comprised the examination of urine composition with their reported recipes.

Struvite precipitation in wastewater treatment plants anaerobic digestion supernatants using a magnesium oxide by-product.

Struvite precipitation is a well-known technology to recover and upcycle phosphorus from municipal wastewater as a slow-release fertiliser. However, the economic and environmental costs of struvite precipitation are constrained by using technical-grade reagents as a magnesium source. This research evaluates the feasibility of using a low-grade magnesium oxide (LG-MgO) by-product from the calcination of magnesite as a magnesium source to precipitate struvite from anaerobic digestion supernatants in wastewater treatment plants. Three distinct LG-MgOs were used in this research to capture the inherent variability of this by-product. The MgO content of the LG-MgOs varied from 42 % to 56 %, which governed the reactivity of the by-product. Experimental results showed that dosing LG-MgO at P:Mg molar ratio close to stoichiometry (i.e. 1:1 and 1:2) favoured struvite precipitation, whereas higher molar ratios (i.e. 1:4, 1:6 and 1:8) favoured calcium phosphate precipitation due to the higher calcium concentration and pH. At a P:Mg molar ratio of 1:1 and 1:2, the percentage of phosphate precipitated was 53-72 % and 89-97 %, respectively, depending on the LG-MgO reactivity. A final experiment was performed to examine the composition and morphology of the precipitate obtained under the most favourable conditions, which showed that (i) struvite was the mineral phase with the highest peaks intensity and (ii) struvite was present in two different shapes: hopper and polyhedral. Overall, this research has demonstrated that LG-MgO is an efficient source of magnesium for struvite precipitation, which fits the circular economy principles by valorising an industrial by-product, reducing the pressure on natural resources, and developing a more sustainable technology for phosphorus recovery.

Optimization of phosphorus recovery using electrochemical struvite precipitation and comparison with iron electrocoagulation system.

A batch monopolar reactor was developed for total phosphorus (TP) recovery using electrochemical struvite precipitation. This study involves the optimization of factors using response surface methodology to maximize the TP recovery. The optimal parameters for this study were found to be a pH of 8.40, a retention time of 35 min, a current density of 300 A/m2 , and an interelectrode distance of 0.5 cm, resulting in 97.3% of TP recovery and energy consumption of 2.35 kWh/m3 . A kinetic study for TP removal revealed that at optimum operating conditions, TP removal follows second-order kinetics (removal rate constant(K) = 0.0117 mg/(m2 ·min)). The system performance was compared to the performance of an iron electrocoagulation system. The composition of the precipitate obtained during the optimal runs were analyzed using X-ray diffraction and EDS analysis. X-ray diffraction analysis of the magnesium precipitate revealed the presence of struvite as the only crystalline compound. PRACTITIONER POINTS: Electrochemical struvite precipitation has the potential to recover total phosphorus from anaerobic bioreactor effluent. Optimum conditions for phosphorus recovery was found at a pH of 8.4, retention time of 35 min, current density of 300 A/m2, and interelectrode distance of 0.5 cm. The quadratic model predicted complete (100 %) TP recovery under optimized conditions, whereas 97.3 % recovery was observed under experimental conditions. TP removal under optimum conditions followed second-order rate equation (removal rate constant(K) = 0.0117 mg/(m2 ·min)). XRD analysis of the precipitate revealed struvite as the only crystalline compound.

Dissolution rate and growth performance reveal struvite as a sustainable nutrient source to produce a diverse set of microbial protein.

To provide for the globally increasing demand for proteinaceous food, microbial protein (MP) has the potential to become an alternative food or feed source. Phosphorus (P), on the other hand, is a critical raw material whose global reserves are declining. Growing MP on recovered phosphorus, for instance, struvite obtained from wastewater treatment, is a promising MP production route that could supply protein-rich products while handling P scarcity. The aim of this study was to explore struvite dissolution kinetics in different MP media and characterize MP production with struvite as sole P-source. Different operational parameters, including pH, temperature, contact surface area, and ion concentrations were tested, and struvite dissolution rates were observed between 0.32 and 4.7 g P/L/d and a solubility between 0.23 and 2.22 g P-based struvite/L. Growth rates and protein production of the microalgae Chlorella vulgaris and Limnospira sp. (previously known as Arthrospira sp.), and the purple non­sulfur bacterium Rhodopseudomonas palustris on struvite were equal to or higher than growth on conventional potassium phosphate. For aerobic heterotrophic bacteria, two slow-growing communities showed decreased growth on struvite, while the growth was increased for a third fast-growing one. Furthermore, MP protein content on struvite was always comparable to the one obtained when grown on standard media. Together with the low content in metals and micropollutants, these results demonstrate that struvite can be directly applied as an effective nutrient source to produce fast-growing MP, without any previous dissolution step. Combining a high purity recovered product with an efficient way of producing protein results in a strong environmental win-win.

Production of struvite by magnesium anode constant voltage electrolytic crystallisation from anaerobically digested chicken manure slurry.

Nitrogen and phosphorus levels in livestock manure and digestive fluid are high, posing a threat to soil and water quality and necessitating nutrient removal and recovery. Phosphorus recovery has the potential to alleviate the global phosphorus resource crisis. This study proposed a magnesium anode constant voltage electrolysis method to crystallise struvite (magnesium ammonium phosphate hexahydrate, MgNH4PO4·6H2O) from anaerobically digested chicken manure slurry using reaction kinetics at variable constant voltages ranging from 2 V to 12 V. The recovery of nitrogen and phosphorus was shown to be effective over a wide initial pH range (3.00 ± 0.03-7.90 ± 0.10) using synthetic digestion fluids. Moreover, the pH gradually increased during the reaction without any external chemical adjustments. The phosphorus recovery rates conformed to the first-order kinetic model, with a maximum rate constant of 2.13 h-1. When the best voltage of 2 V was used at 25 ± 1 °C, the recovery rate reached 5.24 mg P h-1cm-2 in the synthetic digestion fluids during 90 min and 4.60 mg P h-1cm-2 in the anaerobically digested chicken manure slurry. The crystalline products recovered were identified as high-purity struvite by XRD and XPS. The purity of recovered struvite with an initial pH of 3.00 and 7.90 was 96.5% and 98.9%, respectively. These results demonstrated that the magnesium electrode could rapidly react with nitrogen and phosphorus to generate high-purity struvite.

Screening plant growth effects of sheep slaughterhouse waste-derived soil amendments in greenhouse trials.

Ameliorative effects of sheep slaughterhouse waste-derived soil amendments (struvite, blood meal, bone meal) were explored and quantified by a series of comparative greenhouse trials. A scoring matrix system was developed for 25 different test plants using 300 agricultural measurements obtained for three basic growth parameters (fresh-dry plant weights and plant heights) and four different fertilizer sources including solid vermicompost. More than 70% of NH4+-N recovery from sheep slaughterhouse wastewater was achieved using a chemical combination of MgCl2.6H2O + NaH2PO4.2H2O, a molar ratio of Mg2+:NH4+-N:PO43-P = 1.2:1:1, a reaction pH of 9.0, an initial NH4+-N concentration of 240 mg/L, and a reaction time of 15 min. According to SEM micrographs, surface morphology of struvite exhibited a highly porous structure composed of irregularly shaped crystals of various sizes (11.34-79.38 µm). FTIR spectroscopy verified the active functional groups on the proximity of all fertilizer sources within the spectral range of 500-3900 cm-1. TGA-DTG-DSC thermograms of struvite revealed that the mass loss occurred in two temperature regions and reached a maximum mass loss rate of 1.63%/min at 317 °C. The average percentages of increase (57.55-100.62%) and performance points (69-79) corroborated that the fertility value of struvite ranked first on average in cultivation of the analyzed plant species. Findings of this agro-valorization study confirmed that sheep slaughterhouse waste-derived fertilizers could be a beneficial way to promote bio-waste management and environmentally friendly agriculture.

Struvite crystallization by using active serpentine: An innovative application for the economical and efficient recovery of phosphorus from black water.

Recovery of phosphorus from wastewater through struvite crystallization is one of the most attractive methods. However, the cost of chemical consumption makes this technology is unattractive to some extent. In this work, highly active serpentine was prepared by one-step mechanical activation and then used to recover phosphate as struvite from the black water containing 132.8 mg/L phosphorus and 3144 mg/L ammonia nitrogen. The results indicated that the prepared active serpentine can release magnesium ions and hydroxide ions simultaneously into an aqueous solution and is an ideal raw material for struvite crystallization. The factors for phosphorus recovery in this process mainly include mechanical activation intensity, serpentine dosage, and contact time. For the actual black water, a high recovery rate of phosphorus (>98%) is achieved by using active serpentine as the magnesium and alkali source for struvite precipitation. The recovery product was identified as struvite with a median particle size of 32.96 µm. It was confirmed that the mechanical activation damaged the crystal structure of the raw serpentine, improving the activity of Mg2+ and OH-. The undissolved Si-containing particles act as crystal seeds, accelerating the struvite crystallization process. Furthermore, a pilot-scale test was conducted with a rural public toilet in Xiong'an New District, Hebei Province. The results showed that an acceptable phosphorus recovery (98%) could be achieved using active serpentine. Additionally, it was demonstrated that the serpentine process to recover phosphate as struvite reduced the cost by 54.4% in compared with an ordinary chemical process. The active serpentine is a promising dual source of magnesium and alkali for the phosphorus recovery by the struvite method. It has a potential prospect for the large-scale application in phosphorus recovery and struvite fertilizer production.

Quantitative, morphological, and structural analysis of Ni incorporated with struvite during precipitation.

Struvite precipitation is a promising strategy for the simultaneous recovery of nitrogen and phosphorus from waste streams. However, waste streams typically contain high amounts of metal contaminants, including Ni, which can be easily sequestered by struvite, but the behavior of Ni during struvite precipitation remains unclear. Thus, this study investigates the influence of Ni concentrations on struvite precipitation. The quantitative X-ray diffraction (QXRD) results revealed that the purity of struvite decreased from 96.6 to 41.1% with the Ni concentrations increased from 0.1-100 mg·L-1. At lower Ni concentrations of 0.1-1 mg·L-1, scanning electron microscopy (SEM) showed a roughened surface of struvite crystal, and this was combined with X-ray absorption near edge structure (XANES) data that indicated a stack of Ni-OH and Ni-PO4 on struvite surface. At Ni concentrations of 10-25 mg·L-1, Ni primarily crystalized as Ni-struvite (NiNH4PO4·6H2O), as detected by QXRD. At higher Ni concentrations of 25-100 mg·L-1, the co-precipitation of amorphous Ni phosphate(s) (e.g., Ni3(PO4)2) and Ni hydroxide (e.g., Ni(OH)2) was identified by XANES. Specifically, the X-ray photoelectron spectroscopy (XPS) analysis detected the formation of amorphous Mg hydroxide(s) and phosphate(s) at Ni of 25-100 mg·L-1. The overall results revealed that Ni formed Ni-OH and Ni-PO4 on struvite surface at 0.1-1 mg·L-1, whereas Ni precipitated as separated phases (e.g. Ni-struvite, Ni hydroxide and phosphate) at 10-100 mg·L-1. The existence of Ni disturbed the crystal growth of struvite and promoted the formation of Ni-struvite, amorphous products during struvite formation.

Effect of pectin and attapulgite filler on swelling, network parameters and controlled release of diltiazem hydrochloride from polyacrylic copolymer gel.

Pectin grafted polyacrylic copolymer hydrogels were made by free radical crosslink copolymerization of acrylic acid (AA) and acrylamide (AM) in an aqueous solution of pectin. N'N-methylene bis acrylamide (MBA) was used as a crosslinker. During the polymerization reaction the attapulgite (APG) filler was also incorporated in situ into the network of the copolymer gel. Several filled hydrogels were prepared by varying the amount of pectin and APG filler. These hydrogels were characterized by FTIR, 13C NMR, XRD, TGA, SEM, mechanical properties, DMA, swelling, diffusion characteristics and network parameters. The release kinetics of a model drug diltiazem hydrochloride (DT) was studied with these hydrogels. The wt% of pectin, APG and MBA was optimized with a central composite design (CCD) model of response surface methodology (RSM) with equilibrium swelling ratio (ESR), drug adsorption (mg/100 mg gel) and drug release% in 16 h as response. Accordingly, the hydrogel prepared with 5:1 AA:AM molar ratio, 25 wt% monomer concentration, 1% each of initiator and MBA concentration, 18 wt% pectin and 2 wt% APG showed an optimized ESR of 17.75, drug loading of 27.58 and a drug release % of 92.5 in 16 h at a solution pH of 7.4.

Removal of aflatoxin B1 from contaminated peanut oils using magnetic attapulgite.

The efficient magnetic adsorbent (Fe3O4@ATP) was prepared by precipitation through the dispersion of Fe3O4 nanoparticles on the natural attapulgite (ATP) and then tested as an adsorbent for aflatoxin B1 (AFB1) removal from contaminated oils. The adsorbent characterization results revealed that the Fe3O4 were incorporated into the ATP, affording the Fe3O4@ATP composite. This magnetic composite displayed a good ability to eliminate AFB1 from contaminated oils with a removal efficiency of 86.82% using a 0.3% dosage. The Fe3O4@ATP possessed paramagnetic character with a saturation magnetization of 50.86 emu/g, enabling its easy separation from the medium using an external magnet. The adsorption process followed the pseudo-second-order model and fitted the Freundlich isotherm well. Moreover, the thermodynamic studies showed that AFB1 adsorption onto Fe3O4@ATP was exothermic and spontaneous. The novelty of this study lies in the fabrication of magnetic composite adsorbents for AFB1 elimination from oils.

Crystallization kinetics and growth of struvite crystals by seawater versus magnesium chloride as magnesium source: towards enhancing sustainability and economics of struvite crystallization.

The recycling of nutrients from wastewater and their recovery in the form of valuable products is an effective strategy to accelerate the circular economy concept. Phosphorus recovery from wastewater by struvite crystallization (MgNH4PO4·6H2O) is one of the most applied techniques to compensate for the increasing demand and to slow down the depletion rate of phosphate rocks. Using low-cost magnesium sources, such as seawater, improves the financial sustainability of struvite production. In this study, the potential of seawater for struvite crystallization versus the commonly used magnesium source, MgCl2, was tested by crystal growth and kinetic experiments. The impact of ammonium concentration, magnesium concentration and pH on the growth kinetics of struvite in synthetic and real reject water were studied. The results showed that simultaneous precipitation of calcium phosphate was insignificant when using seawater, while presence of struvite seeds diminished it further. Among the supersaturation regulators, pH had the most significant effect on the struvite growth with both MgCl2 and seawater, while high N:P molar ratios further improved the struvite crystal growth by seawater. The N:P molar ratios higher than 6 and Mg:P molar ratios higher than 0.2 are recommended to improve the crystal growth kinetics. It was concluded that seawater is a promising alternative magnesium source and the control of supersaturation regulators (i.e., Mg:P, N:P and pH) is an effective strategy to control the reaction kinetics and product properties.

Attapulgite modified magnetic metal-organic frameworks for magnetic solid phase extraction and determinations of benzoylurea insecticides in tea infusions.

Herein, we developed a novel magnetic solid phase extraction method based on attapulgite-modified magnetic metal-organic frameworks (ATP@Fe3O4@ZIF-8), and this method could be used for the determination of benzoylureas when it was coupled with high-performance liquid chromatography. The established method was validated in terms of linearity (2.5-500 µg L-1, with correlation coefficient (R2) > 0.9994), accuracy (with satisfactory recovery of 88.29-95.99%) and precision (with relative standard deviation (RSD) of less than 8%). In addition, the enrichment factors (EF) ranged from 63.6 to 72.2. Limit of detection (LOD) and limit of quantitation (LOQ) were 0.7-3.2 µg L-1 and 2.3-10.7 µg L-1, respectively. Moreover, there was hardly any noticeable loss of the extraction efficiency when this extraction method undergoes five cycles. Finally, this method was successfully used for the determination of six benzoylureas in different tea infusions and the determined relative recoveries ranged from 78.8 to 114.3%.

A Non-innocent Magnesium Organoclay-Based Drug Vehicle for Improving the Cancer Therapy Effect of Methotrexate.

A synthetic, dispersible magnesium aminoclay (MgAC) was synthesized in the present study. Besides, structural and spectroscopic detections were conducted to investigate the MgAC nanoclay. With a poor aqueous solubility, methotrexate (MTX) has been applied as a valid antitumor agent in recent years. In our research, an unobtrusive sol-gel process was carried out to manufacture the MgAC-MTX nanohybrids through entrapment of MTX over MgAC in situ. The final product was capable of desquamating and thus dispersed in water, equably. In comparison with rough MTX, the MgAC-MTX nanocomposite with a preferable treatment efficacy against MCF-7 cells was mainly attributed to the preeminent enhanced aqueous solubility, controlled release and the increased cellular uptake capacity. Moreover, with excellent anticancer function and hypotoxicity as vindicated in vivo, the MgAC-MTX nanohybrid was supposed to own the potency in the application of malignant tumors cure as a valid nanomedicine. It turned out that, by virtue of its high bioavailability, the MgAC-MTX nanohybrids with high bioavailability is deserving of further study for the treatment of cancers.

Mechanochemical Synthesis of CuO/MgAl2O4 and MgFe2O4 Spinels for Vanillin Production from Isoeugenol and Vanillyl Alcohol.

CuO/MgAl2O4 and CuO/MgFe2O4 catalysts were successfully synthesized with the use of spinel supports by a very simple and low-cost mechanochemical method. High-speed ball-milling was used to synthesize these catalyst supports for the first time. Materials were subsequently characterized by using XRD, FESEM, TEM, EDS-Dot mapping, XPS, BET-BJH, and Magnetic Susceptibility to investigate the physical-chemical characteristics of the catalysts. Acidity evaluation results indicated that the catalyst with the Mg-Al spinel support had more acid sites. XRD results showed a successful synthesis of the catalysts with large crystal sizes. Both catalysts were used in isoeugenol oxidation and vanillyl alcohol to vanillin reactions, with the CuO/MgAl2O4 showing optimum results. This catalyst provided 67% conversion (74% selectivity) after 2 h and this value improved to 81% (selectivity 100%) with the second reaction after 8 h. The CuO/MgFe2O4 catalyst in the first reaction after five hours revealed 53% conversion (47% selectivity) and after eight hours with the second reaction, the conversion value improved to 64% (100% selectivity). In terms of reusability, CuO/MgAl2O4 showed better results than the CuO/MgFe2O4 catalyst, for both reactions.

Nanostructured clay particles supplement orlistat action in inhibiting lipid digestion: An in vitro evaluation for the treatment of obesity.

Obesity is a rapidly growing epidemic, with over one-third of the global population classified as overweight or obese. Consequently, an urgent need exists to develop innovative approaches and technologies that regulate energy uptake, to curb the rising trend in obesity statistics. In this study, nanostructured clay (NSC) particles, fabricated by spray drying delaminated dispersions technologies that regulate energy uptake, to curb the rising trend in obesity statistics. In this study, nanostructured clay (NSC) particles, fabricated by spray drying delaminated dispersions of commercial clay platelets (Veegum® HS and LAPONITE® XLG), were delivered as complimentary, bioactive excipients with the potent lipase inhibitor, orlistat, for the inhibition of fat (lipid) hydrolysis. Simulated intestinal lipolysis studies were performed by observing changes in free fatty acid concentration and revealed that a combinatorial effect existed when NSC particles were co-administered with orlistat, as evidenced by a 1.2- to 1.6-fold greater inhibitory response over 60 min, compared to dosing orlistat alone. Subsequently, it was determined that a multifaceted approach to lipolysis inhibition was presented, whereby NSC particles adsorbed high degrees of lipid (up to 80% of all lipid species present in lipolysis media) and thus physically shielded the lipid-in-water interface from lipase access, while orlistat covalently attached and blocked the lipase enzyme active site. Thus, the ability for NSC particles to enhance the biopharmaceutical performance and potency of orlistat is hypothesised to translate into promising in vivo pharmacodynamics, where this novel approach is predicted to lead to considerably greater weight reductions for obese patients, compared to dosing orlistat alone.

Mineralogy, Structure, and Habitability of Carbon-Enriched Rocky Exoplanets: A Laboratory Approach.

Carbon-enriched rocky exoplanets have been proposed to occur around dwarf stars as well as binary stars, white dwarfs, and pulsars. However, the mineralogical make up of such planets is poorly constrained. We performed high-pressure high-temperature laboratory experiments (P = 1-2 GPa, T = 1523-1823 K) on chemical mixtures representative of C-enriched rocky exoplanets based on calculations of protoplanetary disk compositions. These P-T conditions correspond to the deep interiors of Pluto- to Mars-sized planets and the upper mantles of larger planets. Our results show that these exoplanets, when fully differentiated, comprise a metallic core, a silicate mantle, and a graphite layer on top of the silicate mantle. Graphite is the dominant carbon-bearing phase at the conditions of our experiments with no traces of silicon carbide or carbonates. The silicate mineralogy comprises olivine, orthopyroxene, clinopyroxene, and spinel, which is similar to the mineralogy of the mantles of carbon-poor planets such as the Earth and largely unaffected by the amount of carbon. Metals are either two immiscible iron-rich alloys (S-rich and S-poor) or a single iron-rich alloy in the Fe-C-S system with immiscibility depending on the S/Fe ratio and core pressure. We show that, for our C-enriched compositions, the minimum carbon abundance needed for C-saturation is 0.05-0.7 wt% (molar C/O ∼0.002-0.03). Fully differentiated rocky exoplanets with C/O ratios more than that needed for C-saturation would contain graphite as an additional layer on top of the silicate mantle. For a thick enough graphite layer, diamonds would form at the bottom of this layer due to high pressures. We model the interior structure of Kepler-37b and show that a mere 10 wt% graphite layer would decrease its derived mass by 7%, which suggests that future space missions that determine both radius and mass of rocky exoplanets with insignificant gaseous envelopes could provide quantitative limits on their carbon content. Future observations of rocky exoplanets with graphite-rich surfaces would show low albedos due to the low reflectance of graphite. The absence of life-bearing elements other than carbon on the surface likely makes them uninhabitable.

Production of an upgraded lignin-derived bio-oil using the clay catalysts of bentonite and olivine and the spent FCC in a bench-scale fixed bed pyrolyzer.

Lignocellulosic biomass is an abundant renewable energy source that can be converted into various liquid fuels via thermochemical processes such as pyrolysis. Pyrolysis is a thermal decomposition method, in which solid biomass are thermally depolymerized to liquid fuel called bio-oil or pyrolysis oil. However, the low quality of pyrolysis oil caused by its high oxygen content necessitates further catalytic upgrading to increase the content of oxygen-free compounds, such as aromatic hydrocarbons. Among the three different types of lignocellulosic biomass components (hemicellulose, lignin, and cellulose), lignin is the most difficult fraction to be pyrolyzed because of its highly recalcitrant structure for depolymerization, forming a char as a main product. The catalytic conversion of lignin-derived pyrolyzates is also more difficult than that of furans and levoglucosan which are the main pyrolysis products of hemicellulose and cellulose. Hence, the main purpose of this study was to develop a bench-scale catalytic pyrolysis process using a tandem catalyst (both in-situ and ex-situ catalysis mode) for an efficient pyrolysis and subsequent upgrading of lignin components. While HZSM-5 was employed as an ex-situ catalyst for its excellent aromatization efficiency, the potential of the low-cost additives of bentonite, olivine, and spent FCC as in-situ catalysts in the Kraft lignin pyrolysis at 500 °C was investigated. The effects of these in-situ catalysts on the product selectivity were studied; bentonite resulted in higher selectivity to aromatic hydrocarbons compared to olivine and spent FCC. The reusability of HZSM-5 (with and without regeneration) was examined in the pyrolysis of lignin mixed with the in-situ catalysts of bentonite, olivine, and spent FCC. In the case of using bentonite and spent FCC as in-situ catalysts, there were no obvious changes in the activity of HZSM-5 after regeneration, whereas using olivine as in-situ catalyst resulted in a remarkable decrease in the activity of HZSM-5 after regeneration.

Study on MgxSr3-x(PO4)2 bioceramics as potential bone grafts.

Magnesium (Mg) and strontium (Sr), which are essential nutrient elements in the natural bone, positively affect the osteogenic activity even in wide ranges of ion concentrations. However, it remains unknown whether magnesium-strontium phosphates [MgxSr3-x(PO4)2] are potential bone grafts for accelerating bone regeneration. Herein, a serial of MgxSr3-x(PO4)2, including Mg3(PO4)2, Mg2Sr(PO4)2, Mg1.5Sr1.5(PO4)2, MgSr2(PO4)2 and Sr3(PO4)2, were synthesized using a solid-state reaction approach. The physicochemical properties and cell behaviors of MgxSr3-x(PO4)2 bioceramics were characterized and compared with the common bone graft ß-tricalcium phosphate (ß-TCP). The results indicated that various MgxSr3-x(PO4)2 bioceramics differed in compressive strength and in vitro degradation rate. All the MgxSr3-x(PO4)2 bioceramics had excellent biocompatibility. In contrast to ß-TCP, the MgxSr3-x(PO4)2 enhanced alkaline phosphatase activity of mouse bone mesenchymal stem cells (mBMSCs), and inhibited osteoclastogenesis-related gene expression of RAW264.7 cells, but did not enhance osteogenesis-related gene expression of mBMSCs which were treated with osteogenesis induction supplements. However, Mg3(PO4)2 stimulated osteogenesis-related gene expression of mBMSCs without the treatment of osteogenesis induction supplements. This work contributes to the design of bone graft and may open a new avenue for the bone regeneration field.