Extraction of curcuminoids from deflavored turmeric (Curcuma longa L.) using pressurized liquids: Process integration and economic evaluation

Pressurized liquid extraction (PLE) of curcuminoids from deflavored turmeric rhizomes was optimized. The rhizomes were initially deflavored by extraction with supercritical CO₂. Immediately after SFE, PLE process was performed using ethanol as the solvent and a static extraction time of 20 min, and the independent variables were the temperature (333–353 K) and pressure (10–35 MPa). The results indicate that the optimum extraction temperature and pressure were 333 K and 10 MPa, respectively. PLE required three and six times less extraction time than low-pressure solvent extraction and Soxhlet extraction, respectively, to produce similar extraction yields. The cost of manufacturing (COM) decreased from US$ 94.92 kg⁻¹ to US$ 88.26 kg⁻¹ when the capacity of the two-extractor system increased from 0.05 m³ to 0.5 m³ and from US$ 94.92 kg⁻¹ to US$ 17.86 kg⁻¹ when the cost of the raw materials decreased from US$ 7.91 kg⁻¹ to US$ 0.85 kg⁻¹ for a two 0.05 m³ extractor system.     

Intensification of metal extraction with high-shear mixing

A laboratory flow reactor (V_r = 9.5 mL) with a high shear mixer was used to study the intensification of extraction and stripping. The stirring rate was 15,000 rpm and the reactor space-time was varied from 1.3 to 13 s in extraction experiments. The phases were separated with an in-line centrifuge. Results were compared to those made in batch reactor (V_r = 7.7 L) equipped with conventional pitched-blade turbine impeller. The residence time and drop size distributions of flow reactor were measured. Copper extraction was made from sulfate solution using a hydroxyoxime reagent (LIX 984). Both extraction and stripping reached equilibrium in a few seconds in the flow reactor, while the same required about 250 s in the batch reactor. Residence time distribution was utilized in the model of extraction kinetics. Calculated pseudohomogeneous extraction kinetic constants of the flow reactor and the batch reactor were 5.9 and 0.034 L mol⁻¹ s⁻¹, respectively. Difference was over 150-fold. Measured drop size distributions indicate that differences in generated interfacial area can explain only a part of rate increase. Such dramatic intensification of extraction in flow reactor is interpreted here to be due to both increased interfacial area and decreased diffusion path length.     

Lovastatin production by Aspergillus terreus using lignocellulose biomass in large scale packed bed reactor

The effect of superficial air velocity on lovastatin production by Aspergillus terreus PL10 using wheat bran and wheat straw was investigated in a 7 L and a 1200 L packed bed reactor. Mass transfer and reaction limitations on bioconversion in the 1200 L reactor was studied based on a central composite design of experiments constructed using the superficial air velocity and solid substrate composition as variables and lovastatin production as response. The surface response prediction showed a maximum lovastatin production of 1.86 mg g⁻¹ dry substrate on day 5 of the bioconversion process when the reactor was operated using 0.19 vvm airflow rate (23.37 cm min⁻¹ superficial air velocity) and 54% substrate composition (w_C). Lovastatin production did not increase significantly with superficial air velocity in the 7 L reactor. Variation in temperature and exit CO₂ composition was recorded, and the Damköhler number was calculated for lovastatin production at these two scales. The results showed that in larger reactors mass transfer limitation controlled bioconversion while in smaller reactors bioconversion was controlled by reaction rate limitations. In addition, mass transfer limitations in larger reactors reduced the rate of metabolic heat removal, resulting in hot spots within the substrate bed.     

Solute recovery from ionic liquids: A conceptual design study for recovery of styrene monomer from [4-mebupy][BF4]

Extractive distillation using ionic liquids (ILs) is a promising technology to separate the close-boiling mixture ethylbenzene/styrene. A proper solvent regeneration is crucial to obtain a technical and economic feasible process. In this work, several regeneration technologies were studied to recover styrene from the IL [4-mebupy][BF₄] using Aspen Plus. Stripping with a hot gas (N₂ or ethylbenzene), supercritical CO₂ extraction, distillation by adding a co-solvent, and evaporation were investigated. It was found that the IL that was fed as solvent to the extractive distillation column should have a purity of at least 99.6 wt% to maintain the purities of the top and bottom products from the extractive distillation column. This purity could not be obtained with an evaporator using mild conditions (T = 130 °C, T_condenser ≥ 20 °C). From the process models and the economic evaluation for a typical production capacity of 500,000 mta, the conclusion can be drawn that evaporation using very low pressures (P < 10 mbar) and stripping with ethylbenzene are the most promising technologies to recover styrene monomer from the IL [4-mebupy][BF₄].     

Bulk preparation of (−)-epigallocatechin gallate-rich extract from green tea

(−)-Epigallocatechin gallate (EGCg)-rich extract (EGCg > 700 mg g⁻¹) was prepared from green tea leaves through a three-stage process consisting of liquid–liquid extraction and silica column purification. Crude tea extract was dissolved in ethyl acetate. After filtration, the solution was extracted by 10 g L⁻¹ citric acid solution twice, and then passed through silica column. The catechins compounds in the ethyl acetate eluate were back extracted to the aqueous phase, then extracted with a mixed solution of n-hexane/ethyl acetate (2/5, v/v) 3 times, concentrated, and freeze dried. 12.8 g EGCg-rich extract containing 709 mg g⁻¹ EGCg and 965 mg g⁻¹ total catechins was obtained from 300 g green tea leaves, with an EGCg recovery of 26.1% and a yield of 4.3%. This method was suitable for bulk preparation of EGCg-rich catechins from green tea leaves.     

Flexible free-standing graphene–TiO2 hybrid paper for use as lithium ion battery anode materials

Flexible and binder-free graphene–TiO₂ paper was prepared by a simple route. A unique 3-D nano-structure was achieved with nano-sized TiO₂ intercalated between graphene layers as pillars, significantly increasing the Li-ion insertion/extraction rate. At a current rate of 2 Ag⁻¹, the specific capacity can reach 122 mAhg⁻¹ after 100 charge/discharge cycles. More remarkably, the flexible graphene/TiO₂ hybrid paper shows an excellent stability when the rates decrease from 4 Ag⁻¹ back to 200 mAg⁻¹ with the retained capacity of 175 mAhg⁻¹.     

Supercritical extraction of carob kibbles (Ceratonia siliqua L.)

Carob pulp kibbles, a by-product of carob been gum production, was studied as a source of bioactive agents. Firstly, the carob kibbles were submitted to an aqueous extraction to extract sugars, and supercritical fluid extraction (SFE) was applied to the solid residue of that aqueous extraction, by using compressed carbon dioxide (SC-CO₂) as the solvent and a mixture of ethanol and water (80:20, v/v) as a co-solvent. Pressure and temperature were studied in the ranges 15–22 MPa, and 40–70 °C. Particle diameter, and co-solvent percentage in ranges of 0.27–1.07 mm, and 0–12.4%, respectively, were also studied, as well as the flow rate of SC-CO₂ between 0.28 and 0.85 kg h⁻¹, corresponding, respectively, to 0.0062 and 0.0210 cm s⁻¹ of superficial velocity. The extracts were characterised in terms of antioxidant capacity by DPPH method, and total phenolics content by the Folin–Ciocalteu method. The central composite non-factorial design was used to optimise the extraction conditions, using the Statistica, version 6 software (Statsoft). The best results, in terms of yield and antioxidant capacity, were found at 22 MPa, 40 °C, 0.27 mm particle size, about 12.4% of co-solvent and a flow rate of 0.29 kg h⁻¹ of SC-CO₂. The phenolics profile of the extracts obtained at these conditions was qualitatively evaluated by HPLC-DAD. The solid residue of the supercritical extraction was also studied showing to be a dietary fiber, which can be compared to Caromax™, a carob fiber commercialised by Nutrinova Inc.     

Synergistic effect of various neutral donors in D2EHPA for selective neodymium separation from lanthanide series via HFSLM

The separation of Nd(III) from lanthanide series via hollow fiber supported liquid membrane (HFSLM) using synergistic extractant was investigated. Optimum extraction and stripping obtained were 94.5% and 85.1% using D2EHPA and TOPO mixtures (0.5:0.5 M/M) as the synergistic extractant. Reaction order for both extraction and stripping were first-order with rate constants of 1.444 and 1.338 min⁻¹, respectively. The experimental results were used to correlate with the models. Results showed that the concentration of Nd(III) from the experiment fitted in well with the model results. The average deviation was 1.95% and 2.18% for predictions in both feed and stripping sides, respectively.     

Selectively combusting CO in the presence of propylene

Acrylic acid plant capacity can be increased by 30% by substituting propane for nitrogen (in air) thereby increasing the overall gas heat capacity. To minimize propane purge rates, the effluent is recycled but the CO in the recycle stream must be oxidized to avoid poisoning the catalyst. We studied the kinetics of CO combustion in a micro-fluidized bed with a catalyst inventory of 1 g and a 4 cm ID reactor charged with 5 g of catalyst – Pd/zeolite – and 145 g of inert. Experiments were run at temperatures between 90 and 240 °C and at 1 and 3.2 bara. At temperatures below 140 °C propylene conversion was less than 30% while CO conversion approached 90% at gas hourly space velocities near 10,000 h⁻¹. A first order kinetic model characterized the data over the whole range of conditions in which conversion was varied between 2% and 99+%. The rate constant for CO conversion was equal to 0.75 s⁻¹ whereas it equaled 0.04 s⁻¹ for propylene oxidation; the activation energy for CO oxidation was 95 kJ mol⁻¹ K⁻¹ whereas it was 140 kJ mol⁻¹ K⁻¹ for propylene.     

Sulfur-doped mesoporous carbon from surfactant-intercalated layered double hydroxide precursor as high-performance anode nanomaterials for both Li-ion and Na-ion batteries

We describe a preparation of sulfur-doped mesoporous amorphous carbon (SMAC) from a commercially available alkyl surfactant sulfonate anion-intercalated NiAl-layered double hydroxide precursor via thermal decomposition and subsequent acid leaching. The resultant amorphous carbon is endowed with the integrated advantage of featuring high reversible capacity and long cycling stability: intrinsic doping of sulfur, large specific area, and broad mesopore size distribution. Electrochemical evaluation shows that the SMAC electrode exhibits highly enhanced electrochemical performances, compared with the electrode of non-doped mesoporous and amorphous carbon prepared by using a different surfactant (sodium laurate). A high reversible capacity of 958 mA h g⁻¹ is achieved for the SMAC electrode after 110 cycles at 200 mA g⁻¹, and especially a superlong cycle life with a reversible capacity of 579 mA h g⁻¹ after 970 cycles at 500 mA g⁻¹. Moreover, the SMAC electrode can facilitate the reversible insertion/extraction of Na ion, owing to the proper specific area and mesopore size distribution, as well as the improved electronic conductivity resulted from doping of sulfur.     

Extraction of jojoba seed oil using supercritical CO2+ethanol mixture in green and high-tech separation process

In this study, the extraction of jojoba seed oil obtained from jojoba seed using both supercritical CO₂ and supercritical CO₂+ethanol mixtures was investigated. The recovery of jojoba seed oil was performed in a green and high-tech separation process. The extraction operating was carried out at operating pressures of 25, 35 and 45 MPa, operating temperatures of 343 and 363 K, supercritical fluid flow rates of 3.33 × 10⁻⁸, 6.67 × 10⁻⁸ and 13.33 × 10⁻⁸ m³ s⁻¹, entrainer concentrations of 2, 4 and 8 vol.%, and average particle diameters of 4.1 × 10⁻⁴, 6.1 × 10⁻⁴, 8.6 × 10⁻⁴ and 1.2 × 10⁻³ m. It was found that a green chemical modifier such as ethanol could enhance the solubilities, initial extraction rate and extraction yield of jojoba seed oil from the seed matrix as compared to supercritical CO₂. In addition, it was found that the solubility, the initial extraction rate and the extraction yield depended on operating pressure and operating temperature, entrainer concentration, average particle size and supercritical solvent flow rate. The solubility of jojoba seed oil and initial extraction rate increased with temperature at the operating pressures of 35 and 45 MPa and decreased with increasing temperature at the operating pressure of 25 MPa. Furthermore, supercritical fluid extraction involved short extraction time and minimal usage of small amounts entrainer to the CO₂. About 80% of the total jojoba seed oil was extracted during the constant rate period at the pressure of 35 and 45 MPa.     

NiO/C nanocapsules with onion-like carbon shell as anode material for lithium ion batteries

The synthesis of NiO/C nanocapsules with NiO nanoparticles as the core and onion-like carbon layers as the shell is reported. The NiO/C nanocapsules deliver an initial discharge capacity of 1689.4 mAh g⁻¹ at 0.5 C and maintain a high reversible capacity of 1157.7 mAh g⁻¹ after 50 cycles compared to the NiO nanoparticles of 383.5 mAh g⁻¹. As an anode material for lithium ion batteries, the NiO/C nanocapsules exhibit a remarkable discharge capacity, a high rate charge–discharge capability and an excellent cycling stability. The improvements are ascribed to the fact that the onion-like carbon shells not only can provide enough voids to accommodate the volume change of NiO nanoparticles but also can prevent the formation of solid electrolyte interface (SEI) films on the surface of the NiO nanoparticles and hence the direct contact of Ni and SEI films upon lithium extraction.     

Synthesis of electrically conducting composite adsorbents for wastewater treatment using adsorption & electrochemical regeneration

Electrically conducting adsorbent materials called Nyex™ 1000 & 2000 have already been reported with comparatively low adsorption capacity for various organic, biologically non-degradable and toxic compounds. Two composite adsorbents called CA₁ & CA₂ were synthesized using synthetic graphite-carbon black and expanded graphite-carbon black respectively. The aim of developing the new adsorbents was to increase the adsorption capacity along with good electrical properties. The developed adsorbents were characterized using N₂ adsorption for specific surface area, Boehm surface titration for surface chemistry, bed electrical conductivity, laser size analyzer for average particle size, and scanning electron microscope (SEM) for particle morphology and shape. Then both the composite adsorbents were tested for the adsorption of acid violet 17 followed by an electrochemical regeneration. The adsorption study revealed that both the adsorbents had almost similar kinetic behavior with a significant increase in adsorption capacity for acid violet 17 (300 & 26 mg g⁻¹ respectively) when compared with the adsorption capacity of previously developed electrically conducting materials called Nyex™ 1000 & 2000 (3.5 and 9 mg g⁻¹ respectively). The composite adsorbent CA₂ was successfully electrochemically regenerated by passing an electric charge of 138 C g⁻¹ at a current density of 14 mA cm⁻² for a treatment time of 60 min, whereas, the composite adsorbent CA₁ could not be regenerated successfully. The regeneration efficiencies of CA₂ were obtained at around 120% during five adsorption–regeneration cycles. The amount of actual charge passed of 138 C g⁻¹ for achieving 100% regeneration efficiency was found to be similar with stoichiometrically calculated amount of charge. The amount of electrical energy required to oxidize each mg of adsorbed acid violet onto CA₂ (24 J mg⁻¹) was found to be significantly lower to that of Nyex™ 1000 & 2000 adsorbents (52 J mg⁻¹ & 32 J mg⁻¹ respectively).     

Resin screening for the removal of pyridine-derivatives from waste-water by solvent impregnated resin technology

The selective removal of pyridine derivatives by solvent impregnated resins has been studied. A solvent impregnated resin consists of a macro-porous particle that is impregnated with a solvent. This technology allows the use liquid–liquid extraction in fixed-bed operation, and prevents problems like entrainment and irreversible emulsification. 4-Cyanopyridine was chosen as model pyridine derivative, and 4-nonylphenol was used as solvent. The aim of this study was to select the most suitable resin for this application. While in the literature there are mainly two types of resins used, MPP and Amberlite XAD type, a comparative study has not yet been conducted. In this study, a series of resins were impregnated with the solvent and applied in sorption experiments to study on the effect of the resin properties on the capacity, selectivity and mass-transfer rates of the solvent impregnated resins. It was found that the capacity could be estimated accurately with the previously developed liquid–liquid extraction equilibrium model. Additionally, the selectivity was determined by the solvent properties, and hardly affected by the resin matrix. The mass-transfer rates were primarily determined the by particle diameter, whereas the effect of the porosity is small. On the basis of the results it was established that Amberlite XAD4 had the best combination of capacity, mass-transfer rate, mechanical strength, selectivity and pressure drop over a fixed-bed column and was therefore chosen for a more detailed study. The results showed that the breakthrough curve is broad due to mass-transfer limitations. The loading cycle of the column could be described with great accuracy using the mathematical model developed in this study. Regeneration of the column could be performed efficiently with a pH-swing using hydrochloric acid at a pH of 1. The fixed bed column was percolated with 7000 bed volumes of aqueous solutions varying in composition. No reduction in the capacity was observed which demonstrated that the SIR consisting of Amberlite XAD4 and 4-nonylphenol is highly stable.     

Synthesis and characterization of porous maghemite as an anode for Li-ion batteries

The synthesis of porous maghemite via a simple glycerol-mediated solution method was successfully accomplished. Thermal analysis, X-ray diffraction and Mössbauer spectroscopy results disclosed the formation of maghemite. The morphological and structural features of maghemite were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and nitrogen adsorption–desorption. The powder showed Brunauer–Emmett–Teller surface area of 285 m² g⁻¹ with micro-, meso- and macropores.The anode body was doctor bladed using primary powder with a binder and a conductive agent. Galvanostatic charge–discharge cycling of the porous maghemite exhibited a specific reversible capacity of approximately 1180 mAh g⁻¹ at 100 mA g⁻¹ current density, which was two times higher than that of common nanomaghemite with average particle size of 19 nm. The cell showed stability even at the high current charge–discharge rates of 3000 mA g⁻¹ and more than 94% retention. After multiple high current cycling regimes, the cell recovered to nearly full reversible capacity of ~1120 mAh g⁻¹ at 100 mA g⁻¹. The reason for this remarkable performance of the present anode was thought to be dependent upon the role of pores in increasing the surface area and resistance against volume changes during lithium insertion/extraction.     

Separation and determination of cadmium in water by foam column prior to inductively coupled plasma optical emission spectrometry

The sorption profile of cadmium (II) ions from aqueous iodide media onto procaine hydrochloride (PQ⁺·Cl⁻) treated polyurethane foams (PUFs) solid sorbent was studied. PQ⁺·Cl⁻ treated PUFs solid sorbent was found suitable and fast for Cd²⁺ uptake as [CdI4]_aq²⁻. Thus, removal of Cd²⁺ at trace levels by the sorbent packed columns was achieved. The sorbed Cd²⁺ species onto packed column were recovered with HNO₃ (10.0 mL, 1.0 mol L⁻¹) prior determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). Plot of Cd²⁺ ions concentration was linear in the range 0.05–15 μg L⁻¹. The limits of detection and quantification of Cd²⁺ were found 0.01 μg L⁻¹ and 0.033 μg L⁻¹, respectively. Such limits could be improved to lower values by retention of Cd²⁺ species from large sample volumes of the aqueous phase at the optimized conditions. The relative standard deviation of the packed column for the extraction and recovery of standard aqueous solutions (0.1 L) containing 1.0 and 5.0 μg L⁻¹ (n = 3) of Cd²⁺ ions at flow rate of 5.0 mL min⁻¹ were 1.98 and 2.9%, respectively. The method was validated by analysis of Cd in certified reference materials (CRMs) IAEA-Soil-7 and TMDW water and wastewater samples.     

Dopamine derived nitrogen-doped carbon sheets as anode materials for high-performance sodium ion batteries

Designed as an anode material for sodium ion batteries, nitrogen-doped carbon sheets (NCSs) were successfully synthesized using graphene and dopamine as template and carbon precursor, respectively. The NCSs demonstrate high reversible capacity and excellent rate performance, delivering a high reversible capacity of 382 mAh g⁻¹ at 50 mA g⁻¹ after 55 cycles. Even up to 10 A g⁻¹, a rate capacity of 75 mAh g⁻¹ can be obtained. Furthermore, NCSs also have remarkable cycling stability with specific capacity of 165 mAh g⁻¹ after 600 cycles (under 200 mA g⁻¹). The excellent performance of NCSs can be ascribed to the nitrogen-doped two-dimension sheet structure.     

Supercritical CO2 oilseed extraction in multi-vessel plants. 1. Minimization of operational cost

This work uses a fully predictive mass transfer model to simulate the supercritical CO₂ extraction of vegetable oils from prepressed oilseeds in the 1-m³ vessel of an industrial multi-vessel plant operating at 40 °C and 30 MPa with the purpose of minimizing the operational cost. The work analyses the effect of particle diameter (0.5, 1, 2, 3, and 4 mm), superficial CO₂ velocity (2.76, 5.52, or 11.0 mm/s), and number of extraction vessels (2, 3, or 4) on optimal extraction time and minimal operational cost. Keeping other variables constants, cost diminishes as particle diameter decreases. Although the optimal superficial CO₂ velocity increases as particle diameter decreases, in the case of small (≤1 mm) particles, substrate fluidization may place an upper limit to the superficial velocity. Within the studied region, best superficial CO₂ velocities are 11.0 mm/s for particles smaller than 1–2 mm, 2.76 mm/s for particles larger than 3–4 mm, and 5.52 mm/s for particles in between. Keeping other variables constant, the cost of extraction of medium-to-large (≥2 mm) particles decreases as the number of extraction vessels increases, at the expense of an increase in extraction time. However, because of a sharp transition wave that develops when extracting small (≤1 mm) particles that separates fully extracted (downstream) from virtually unextracted (upstream) substrate within extraction vessels, two-vessel plants are best for small particles. The lowest operational cost observed in this work was USD 4.08 kg⁻¹ oil for the extraction of 2-mm particles using 3.30 m³/h of CO₂ (U = 2.76 mm/s) in a four-vessel plant.     

Polymer microsphere-assisted synthesis of lithium-rich cathode with improved electrochemical performance

The Li-rich layered cathode material Li_1.165Mn_0.501Ni_0.167Co_0.167O₂ with porous structure has been successfully synthesized through a facile co-precipitation approach followed with a high-temperature calcination treatment, adopting polymer microsphere (PSA) as a template and conductive agent. The PSA-assisted Li_1.165Mn_0.501Ni_0.167Co_0.167O₂ composite exhibits remarkably improved cycling stability and rate capability compared with the bare composite. It delivers a high initial discharge capacity of 267.0 mA h g⁻¹ at 0.1 C (1 C=250 mA g⁻¹) between 2.0 V and 4.65 V. A discharge capacity of 214.9 mA h g ⁻¹ is still obtained after 100 cycles. Furthermore, the diffusion coefficients of Li⁺ investigated by the cyclic voltammetry technique are approximately 10⁻¹⁵–10⁻¹⁴ cm² s⁻¹. Such outstanding performance is mainly ascribed to: on one hand, the carbon residue of PSA after being calcined at high temperature contributes to enhance the electronic conductivity of the electrode and alleviates the volume changes during the Li⁺-insertion/extraction, leading to an improved rate capability; on the other hand, the unique porous structure and small particle size are conductive to increase the exposed electrochemical active surface, shorten Li⁺ diffusion distance and thus enhance the lithium storage capacity.     

Reduced graphene oxide with superior cycling stability and rate capability for sodium storage

Sodium ion battery is a promising electrical energy storage system for sustainable energy storage applications due to the abundance of sodium resources and their low cost. In this communication, the electrochemical properties of sodium ion storage in reduced graphene oxide (RGO) were studied in an electrolyte consisting of 1 M NaClO₄ in propylene carbonate (PC). The experimental results show that the RGO anode allowed significant sodium ion insertion, leading to higher capacity at high current density compared to the previously reported results for carbon materials. This is due to the fact that RGO possesses higher electrical conductivity and is a more active host, with large interlayer distances and a disordered structure, enabling it to store a higher amount of Na ions. RGO anode exhibits high capacity combined with long-term cycling stability at high current densities, leading to reversible capacity as high as 174.3 mAh g⁻¹ at 0.2 C (40 mA g⁻¹), and even 93.3 mAh g⁻¹ at 1 C (200 mA g⁻¹) after 250 cycles. Furthermore, RGO could yield a high capacity of 141 mAh g⁻¹ at 0.2 C (40 mA g⁻¹) over 1000 cycles.