Solid Loading Research Articles

Characterization and structural analysis of alcohol-fractionated lignin biofuels processed at ambient temperature

This study introduces Cold-processed Lignin in (M)ethanol Oil (CLEO/CLiMO), a novel biofuel technology derived from the alcohol-fractionation of lignin at ambient temperatures, offering a sustainable alternative to conventional marine fuels. The production process achieved solid loadings of up to 60 wt% lignin and a volumetric energy density 39 % higher than pure alcohols. Lignin concentrations above 30 wt% promoted colloidal stability through the proposed formation of a spanning network of lignin aggregates, associated with a 100-fold increase of viscosity. Additionally, we observed a decrease in the radius of gyration of lignin particles from 2.5 to 2.7 nm at 30 wt% to 1.1–1.3 nm at 60 wt% following a transition from globular to elongated random coil shaped particles. This was accompanied by a twofold increase in the partial specific volume of lignin, suggesting a reduction in packing efficiency. The study highlights CLEO's potential as a sustainable shipping fuel alternative, combining favorable fuel properties with a simple and scalable production method.

High-solids saccharification of non-pretreated citrus peels through tailored cellulase

Citrus peels, characterized by their low lignin and high sugar content, have been drawing increasing attention as a valuable lignocellulosic biomass with significant potential in biorefinery. Notably, in this study, the citrus waste was found to be enzymatically accessible without any pretreatment. Moreover, to promote the high-solids saccharification of the citrus peels, a tailored cellulase cocktail was formulated by response surface methodology (RSM), along with a fed-batch strategy aiming to obtain a high substrate loading. The study resulted in an optimized cellulase cocktail (7.08 U/g DM of β-glucosidase, 164.17 U/g DM of hemicellulase, 47.38 mg/g DM of sophorolipid, and 64.68 mg/g DM of Tween 80) and achieved solids loading of 22 % with a total sugar concentration of 123.84 g/L, corresponding to a yield of 93.12 % (65.28 % in batch operation). These findings provided essential validation for the efficient utilization of citrus waste, ensuring them promising potential as feedstock for sugar platforms.

Moulding of SS316L surgical component using palm-stearin feedstock: Rheological analysis, process window and parametric optimisation

Metal injection moulding of a thin surgical component using a palm-stearin based SS316L feedstock was investigated. The study first determined the optimal solids loading of the feedstock, followed by examining its sensitivity to the shear rate and temperature, to ensure its pseudo-plastic behaviour. After developing the Mouldability index, a process window was established based on the experiments to present appropriate injection parameters. Using the analysis of variance, the significance and mutual coupling of each parameter was evaluated. The study found that the impact of injection speed was greater than other parameters, while holding pressure showed little effect. The verified optimised injection parameters to maximise the green density were found to be an injection temperature of 155 °C, an injection speed of 80 mm/s, a holding pressure of 83 bar, a holding time of 9 s, and an injection pressure of 132 bar, resulting in a green part density of 4.892 g/cm3.

Digital light processing of yttria-stabilized zirconia: Modeling photoinitiator decay

A digital process was developed to facilitate additive manufacturing for ceramic materials using digital light processing (DLP). A numerical model that predicts DLP sample properties can be generated from manufacturing inputs to forecast the effect of resin age on mechanical strength of the printed part based on data collected from experiments. Key parameters for printing the green bodies included determining the depth of cure, layer thickness, material composition, and solids loading. Thermogravimetric analyses were used to develop debinding and sintering curves. Debinding is used to remove the volatile organics comprising the photopolymer resin. Sintering is performed after debinding to increase density and mechanical strength of the printed parts. The sintered parts were then subjected to characterization and mechanical testing. The ensemble of data for various DLP-printed ceramic materials were added to a database. A design of experiments can be generated from the manufacturing process defined in the database with selected changeable parameters randomized over a range. Because the database is defined with an architecture to capture manufacturing processes, it can persist as a more generic platform for manufacturing digital twins. This can ease the development of future digital twins and can grow as a common repository for the insights gained from manufacturing research. Creating a digital twin of a DLP system for 3D printing parts enables manufacturers to simulate and assess the impact of resin age on printing parameters and part quality, facilitating optimization, predictive maintenance, and cost reduction.

Leaching Efficacy of Ethylenediaminetetraacetic Acid (EDTA) to Extract Rare-Earth Elements from Monazite Concentrate

Alkaline EDTA solution has been previously identified as an effective leaching agent for solubilising rare-earth oxalates. These oxalates are the product of an oxalic acid conversion leach dissolving monazite and redepositing the salt. Pervious work suggested a significant increase in recovery was observed between pH 8 and 10; we have demonstrated that, in an excess of EDTA, this is not the case, and the dissolution is similar. While demonstrating that, at a nominal solid loading of 100 g/L, 0.2 M EDTA solution produced the highest dissolution, elevated solids require an equivalent increase in lixiviant concentration driven by consumption. Very-high-solution concentrations (>50 g/L dissolved TREEs) were achieved at a high solid loading, indicating both that a solution equilibrium is yet to be reached and that a build-up of oxalate in the system (estimated at ~1 M) does not impact the leach efficiency. We have also demonstrated the recycling of EDTA to use in multiple stages as well as the ability to recover oxalate from this solution.

Enhanced enzymatic hydrolysis of corn stover by γ-valerolactone pretreatment and the characteristics of enzymatic residues

Efficient pretreatment methods are crucial for the generation of fermentable sugars from the renewable lignocellulose. In this study, γ-valerolactone (GVL), a biomass-derived green solvent, was used to fractionate corn stover (CS). The impact of different additives on the enzymatic hydrolysis and pretreatment of CS within the GVL/water system was carefully investigated. The results demonstrate that the use of H2SO4-assisted GVL/H2O (80:20, w/w) pretreatment at mild conditions successfully facilitates the depolymerization of CS, thereby improving the cellulase accessibility. Furthermore, by increasing the GVL pretreatment temperature to 160 °C with 100 mM H2SO4 addition, the pretreated CS led to nearly 100 % of hydrolysis yield at 2 % (w/v) solid load. Finally, the thermogravimetric analysis (TGA) was performed to evaluate the thermal decomposition characteristics of untreated CS and enzymatic residues based on the H2SO4-assisted GVL/H2O pretreatment. The results indicate that the enzymatic residues had two depolymerization stages from 200 °C to 500 °C with a final residual mass of 22.73 %, which was higher than that of untreated CS (20.56 %). Overall, this study provides an efficient lignocellulose pretreatment for fermentable sugars production and valorization of enzymatic residues.

Pretreatment of Vine Shoot Biomass by Choline Chloride-Based Deep Eutectic Solvents to Promote Biomass Fractionation and Enhance Sugar Production.

Vine shoots hold promise as a biomass source for fermentable sugars with efficient fractionation and conversion processes. The study explores vine shoots as a biomass source for fermentable sugars through pretreatment with two deep eutectic solvents mixtures: choline chloride:lactic acid 1:5 (ChCl:LA) and choline chloride:ethylene glycol 1:2 (ChCl:EG). Pretreatment conditions, such as temperature/time, solid/liquid ratio, and biomass particle size, were studied. Chemical composition, recovery yields, delignification extent, and carbohydrate conversion were evaluated, including the influence of washing solvents. Temperature and particle size notably affected hemicellulose and lignin dissolution, especially with ChCl:LA. Pretreatment yielded enriched cellulose substrates, with high carbohydrate conversion rates up to 75.2% for cellulose and 99.9% for xylan with ChCl:LA, and 54.6% for cellulose and 60.2% for xylan with ChCl:EG. A 50% acetone/water mixture increased the delignification ratios to 31.5%. The results underscore the potential of this pretreatment for vine shoot fractionation, particularly at 30% solid load, while acknowledging the need for further process enhancement.

Microstructural evolution and strengthening mechanism of TC4/ZTA composites fabricated by laser-directed energy deposition

In this study, zirconia-toughened alumina (ZTA) ceramics were prepared and used to fabricate crack-free, high-performance titanium alloy (TC4)/ZTA ceramic composites with a gradient material design through laser-directed energy deposition. The ZTA content gradients ranged from 0 wt% (0ZTA layer) to 20 wt% (20ZTA layer). During laser deposition, Ti reacted with Al2O3 in the ZTA ceramics to form TiAl2O5. Under rapid cooling in the non-preheated sample, the TiAl2O5 and ZrO2 in the 20ZTA layer underwent a phase transformation, resulting in the formation of TiAl2O5, Al2O3, and t-ZrO2. The cooling rate was lower in the preheated sample, which promoted the reaction between Ti and ZrO2, producing Ti2O. The stability of the β-Ti crystal structure was significantly affected by the presence of Al and Zr in the ZTA. First-principles calculations revealed that preheating caused a larger proportion of Al2O3 to melt, primarily destabilizing the β-phase through the action of Al. The reduction in the cooling rate also promoted the β → α phase transformation; making the α-phase dominant in the 20ZTA layer of the preheated sample. In the preheated sample, the hardness of the 20ZTA layer was 1.95 times greater than that of the 0ZTA layer, and the wear volume was reduced by 91.42 %. The strengthening mechanisms in the 20ZTA layer, in descending order, were solid solution strengthening, dislocation strengthening, load transfer, and grain refinement.

AC electric field-induced changes in viscosity of aqueous ceramic suspensions and tuning of freeze-cast microstructure and compressive strength

A systematic parametric study was conducted on alternating current (AC) electric field-assisted freeze-casting to enable a comprehensive understanding of tuning freeze-cast microstructure and compressive strength and provide insights into the role of AC field. A novel finding was that the AC field increased the viscosity of aqueous ceramic suspensions, where the viscosity increase was dependent on the ceramic loading of suspensions, dispersant concentration, and field duration. Viscosity increased with field duration for a fixed solid loading and dispersant concentration. It was suggested that AC field-induced dielectrophoretic (DEP) forces decreased interparticle distances and increased interparticle interactions in ceramic suspensions, hence viscosity. It was revealed that the increase in viscosity of ceramic suspensions due to the AC field could be reversed. It was demonstrated that simple magnetic stirring of the suspensions previously subjected to an AC field (which increased viscosity) reduced viscosity to the level of the as-prepared suspensions. For materials fabrication, an AC electric field was applied to aqueous ceramic suspensions for the desired duration, then turned OFF, followed by freeze-casting, which remarkably influenced freeze-cast sintered microstructure. The impact of the field on microstructure increased with solid loading, dispersant concentration, and field duration, and microstructure changes were associated with viscosity of suspensions prior to freeze-casting. With increasing viscosity, freeze-cast microstructure became increasingly dendritic, i.e., bridge density increased. A positive correlation was observed between bridge density and compressive strength for all the materials. Depending on the solid loading, dispersant concentration, and field duration, about 5- to 8-fold increase in strength was achieved.

A novel microwave-assisted γ-valerolactone and glycolic acid pretreatment for green and sustainable production of hemp fibres

Hemp, a sustainable crop, offers superior material properties suitable for diverse applications. This study aims to produce hemp fibre using a green and sustainable pretreatment method, thus exploring a novel microwave-assisted pretreatment method using a γ-valerolactone (GVL) and glycolic acid (GA) solution system, referred to as the GVL/GA pretreatment method. By optimising solid loading and reaction time, we significantly reduced water usage (50 %) and energy consumption (61.5 %) while maintaining fibre quality. The pretreatment method effectively removed lignin (88.7 %) and hemicellulose (39.3 %) without damaging the cellulose structure. The pretreated samples demonstrated a 45.7 % increase in glucose yield. Additionally, the characterisation of pretreated fibres revealed impressive fineness (4.4 dtex) and tenacity (4.0 cN/dtex), and the crystal structure remained intact with increased crystallinity (86 %). The HSQC NMR analysis unveiled that lignin undergoes structural modifications, enabling efficient lignin removal. GVL/GA pretreatment promotes green chemistry by minimising environmental impact and waste, using renewable resources. It provides a sustainable alternative to traditional methods, contributing to a greener industry.

Enhancing bioethanol yield from food waste: Integrating decontamination strategies and enzyme dosage optimization for sustainable biofuel production

Amidst the global surge in energy demand, the public’s focus has shifted from fossil fuels to more sustainable and eco-friendly fuels like bioethanol. Thus, the prospect of producing bioethanol from food waste (FW) is gaining traction, offering a sustainable solution to both waste management and energy needs. However, increasing bioethanol yields during food waste fermentation requires an approach that addresses the variability of these heterogeneous feedstocks in terms of chemical composition, microbial contamination, enzyme dosage requirements, and high moisture content. Hence, this study evaluated thermal and chemical decontamination strategies for pre- and post-consumer food waste and minimised the exogenous enzyme dosage by applying an engineered, amylase-producing strain (Saccharomyces cerevisiae ERT12). Results show that thermal sterilisation at an elevated liquefaction temperature significantly improved ethanol yields (from pre-and post-consumer food waste) more than chemical decontamination methods. Also, key findings show that applying the amylase-secreting yeast reduced enzyme dosages by up to 33 %. During fed-batch fermentation with strain ER T12, the highest possible solids loading increased the final ethanol concentrations by 96 % (for pre-consumer FW) and 85 % (for post-consumer FW) compared to batch fermentation. Also, the pre-consumer to post-consumer FW fed-batch fermentation maintained acceptable volumetric production rates of 2.35 to 1.57 g/l.h and yielded 87.6 to 61.2 % of the theoretical maximum. Although the maximum solids loadings, ethanol titres and yields achievable in food waste fermentations were still limited by the inherent moisture contents of the feed, they demonstrated performances that may be appropriate for industrial implementation, considering the negative feedstock costs.

Enhancing thermal conductivity of AlN ceramics via vat photopolymerization through refractive index coupling and oxygen fixation

Despite the growing development of ceramic fabrication by vat photopolymerization (VP), major gaps remain in application. Particularly in the case of VP-printed aluminum nitride (AlN) ceramic, the thermal conductivity is still below 170 W·m−1·K−1, a critical benchmark for efficient heat dissipation. To address this challenge, here we prepared an AlN slurry with high curing thickness through RI coupling between liquid-solid phase, and took into account of the rheological property under high solid loading. Full dense AlN green bodies with solid loading up to 50 vol% were successfully printed. Aiming to to tackle the degradation of thermal conductivity issue caused by oxygen increment of AlN via VP, we systemically studied the form of oxygen in AlN preparation processes. Through the sintering optimization, the oxygen element from the hydrolysis of AlN surface was fixated in the sintering aid Y2O3. Eventually, without any special process control or additional treatment, the final sintered AlN ceramics prepared by the developed slurry present a full densification and the highest thermal conductivity (up to 187.9 W∙m−1∙K−1) of any known additive manufactured ceramics.

Direct ink writing of WC-Co composite with flexible green bodies

Direct ink writing of 3D WC-Co with conformable green bodies was achieved benefiting from the highly flexible WC-Co paste with high solid loading. Rheology properties of the paste, microstructure of the 3D structure was investigated. Organic-based paste of WC-8Co with a high solid content of 91 wt% were prepared, which exhibited shear thinning behavior and had a high storage modulus, two key parameters for ensuring the smooth printing. After secondary molding, 3D WC-Co green bodies with overhanging structure and no cracks were confirmed through secondary treatment of twisting or bending. Sound 3D structures with uniform and dense microstructure were obtained after debinding and sintering in vacuum. This work showed a facile route for the fabrication of 3D bone cemented carbides by direct ink writing with flexible green bodies.

Adjusting the surface quality of printed components via controlling dispersant content to improve the electrical performance of DLP-printed PZT ceramics and devices

This paper aims to enhance the surface quality of digital light processing (DLP) printed lead zirconate titanate (PZT) components by controlling the content of BYK-111 dispersant, thereby improving the electrical properties of the resulting printed piezoelectric ceramics and devices. 55 vol% high solid loading PZT slurries with different dispersant contents were prepared and assessed for their dispersion stability, rheological behavior and curing characteristics. The slurry containing 1 wt% BYK-111 demonstrated ideal rheological properties, notably achieving a low viscosity of 1.37 Pa·s at 100 s−1. The surface roughness of the printed ceramic component was reduced to 69.3 nm, representing a 57.1 % improvement in surface quality compared to other dispersant levels. The printed PZT ceramic exhibited superior piezoelectric performance, with a piezoelectric constant d33 reaching 445 pC/N, surpassing most existing 3D-printed macro-sized piezoelectric ceramics. Furthermore, a DLP-printed 1–3 piezoelectric array was encapsulated to fabricate an acoustic emission (AE) sensor, which achieved a low substrate noise level of 31 dB and a high signal-to-noise ratio of 62 dB, outperforming commercial sensors. The optimal BYK-111 content not only ensures favorable dispersion stability and rheological properties in the slurry, but also significantly enhances the surface quality and density of the printed ceramic components, ultimately leading to the production of high-performance piezoelectric ceramics and devices.

Synergistic effect of Cerium and Niobium enhances the low-temperature NH3-SCR activity of Fe-containing solid waste

To develop environment-friendly low temperature NH3-SCR catalyst and realize the resource utilization of industrial solid waste, this research prepared a series NH3-SCR catalysts by using Fe-containing solid waste loading CeO2 and Nb2O5. It was found that the Ce2Nb1/Fe-Si catalyst exhibited the highest NH3-SCR activity, reaching about 93 % NOx conversion and 99 % N2 selectivity at 300 °C due to the synergistic effect between Ce and Nb species. The characterization results showed that the interaction between Ce and Nb was stronger than that between Nb and Fe species, promoting the NH3 adsorption and redox cycle of Ce4+ + Nb4+ ↔ Ce3+ + Nb5+, Ce3+ + Fe3+ ↔ Fe2+ + Ce4+, which increased the contents of Fe2+ and surface adsorbed oxygen. Moreover, the co-existence of Ce and Nb species would increase the NOx adsorption ability and promote the oxidation of NO to NO2, which was beneficial for “Fast SCR” reaction. Finally, the introduction of CeO2 and Nb2O5 did not changed the reaction mechanism, followed by a Langmuir-Hinshelwood mechanism.

Investigating the effect of polymer additives on the rheology of SiC/clay paste for use in Direct Ink Writing method

AbstractIn this study, we investigated the impact of polyethylene glycol, sodium carboxymethyl cellulose, and polyvinyl alcohol on the rheological behavior, printability, and mechanical/physical properties of 3D‐printed scaffolds for high‐temperature applications using SiC/clay ceramic paste. Employing the Direct Ink Writing method, varying concentrations of each polymer (PEG: 2.5%–10% weight, CMC: .6%–1.8% weight, PVA: .25%–1% weight) were incorporated into the composition. The resulting SiC/clay paste, with adjusted additive content, was used to 3D‐print scaffold structures through Direct Ink Writing. Sintering of clay‐bonded SiC samples were carried out at 1300°C for 1 h in an ambient atmosphere. The research revealed that altering the additive amounts significantly influenced the rheological behavior, mechanical properties, and physical characteristics of the printed specimens. Notably, the ideal properties with additive concentrations (10% wt PEG, 1% wt PVA, and .6% CMC) were identified, providing the best outcomes in terms of printability and firing results. High density samples with 2.09, 1.93, and 1.79 g/cm3, high compression strength of 20.82, 14.5 and 12.53 MPa with 32.26%, 42.5%, and 52.63% open porosity for samples containing PVA, CMC, and PEG modifiers were obtained, respectively. Additionally, the study led to the development of a high solid loading printable paste with an 80% weight.

Computer aided flow investigation of liquid agricultural wastes

Liquid agricultural wastes serve as important fertilizers in modern agriculture but pose environmental and health risks due to high nitrogen compound content. To prevent soil and groundwater contamination, ammonia separation is required before waste application on fields. Conventional separation by stripping is difficult because of column clogging by solid waste loads. This work investigates, both experimentally and numerically, the flow behaviour of liquid agricultural waste to support the development of innovative separators based on inclined plates. The measurements were carried out in a newly developed experimental setup consisting of a liquid distributor over a plate with variable inclination angles. The influence of volumetric flow rate and inclination angles on the flow topology and liquid detachment from the edge of the plate was studied. While the impact of the flow rate was significant, no influence of the plate inclination angle could be observed. A CFD model was developed to support experimental work. Its validation with experimental data was successful, yet with some systematic deviation due to the model simplifications. The developed experimental setup and CFD model offer optimization potential for separation column internals designed for liquid agricultural wastes, with experiments providing higher accuracy and simulations offering flexibility.

Using Extracted Sugars from Spoiled Date Fruits as a Sustainable Feedstock for Ethanol Production by New Yeast Isolates.

This study focuses on investigating sugar recovery from spoiled date fruits (SDF) for sustainable ethanol production using newly isolated yeasts. Upon their isolation from different food products, yeast strains were identified through PCR amplification of the D1/D2 region and subsequent comparison with the GenBank database, confirming isolates KKU30, KKU32, and KKU33 as Saccharomyces cerevisiae; KKU21 as Zygosaccharomyces rouxii; and KKU35m as Meyerozyma guilliermondii. Optimization of sugar extraction from SDF pulp employed response surface methodology (RSM), varying solid loading (20-40%), temperature (20-40 °C), and extraction time (10-30 min). Linear models for sugar concentration (R1) and extraction efficiency (R2) showed relatively high R2 values, indicating a good model fit. Statistical analysis revealed significant effects of temperature and extraction time on extraction efficiency. The results of batch ethanol production from SDF extracts using mono-cultures indicated varying consumption rates of sugars, biomass production, and ethanol yields among strains. Notably, S. cerevisiae strains exhibited rapid sugar consumption and high ethanol productivity, outperforming Z. rouxii and M. guilliermondii, and they were selected for scaling up the process at fed-batch mode in a co-culture. Co-cultivation resulted in complete sugar consumption and higher ethanol yields compared to mono-cultures, whereas the ethanol titer reached 46.8 ± 0.2 g/L.

Effect of high solids loading on gas–liquid mass transfer in an oscillatory flow reactor for process intensification

A wide range of chemical processes involves three phases, where common systems have inefficient mixing and mass transfer is limited. This study uses the oscillatory flow reactor with smooth periodic constrictions (OFR-SPC) according to the patent EP3057694 (B1) to evaluate its potential on O2 mass transfer at high solids loading (10–50 % (v/v)). For that, the effect of solids (EPS, PVC) properties (concentration, density, and size) on the performance of the volumetric liquid-side mass transfer coefficient (kLa), gas holdup (εG) and Sauter mean bubble diameter (d32) using several operational conditions (oscillation amplitude and frequency, superficial gas velocity) was assessed. Results show that oscillatory conditions can influence the solids effect on kLa. At solid load (≥ 30 % (v/v)) under low oscillations, kLa decreased, εG and d32 increased, slug flow regime emerged and the OFR-SPC behaved as fixed bed reactor. Contrary, no significant influence of solid properties on kLa, and εG was observed at higher oscillations, where the reactor behaved as fluidized bed in a homogeneous flow regime. Notably, solids’ concentration (<30 % (v/v)), size and density revealed a negligible influence on mass transfer for all range of oscillations, contrary to the widespread consensus where kLa tends to decrease in conventional reactors at lower solid’s load (<15 % (v/v)), making the OFR-SPC a valuable resource for catalytic processes. The OFR-SPC demonstrated higher mass transfer rates (∼3 − fold) than conventional multiphase devices with reasonable power consumption (∼100 W/m−3(−|-)). These are remarkable results, which indicate the OFR-SPC for three-phase industrial processes intensification.

(Invited) Streamlined Production of Protonic Ceramic Electrochemical Cells Via Ultrasonic Spray Coating

Thin solid oxide films are crucial for developing high-performance solid oxide-based electrochemical devices aimed at decarbonizing the global energy system. This presentation introduces ultrasonic spray coating technique (USC) for producing <10 µm thin electrolyte films, as well as uniform 4×4 cm2 oxygen electrode films, with a systematic process optimization considering solid loading rates, spray passes, and annealing temperature etc. Notably, the integrated approach highlights the versatility of USC in addressing both oxygen electrode and electrolyte fabrication challenges. The resulting protonic ceramic electrochemical cells, fabricated with these optimized parameters, exhibit remarkable electrochemical performance, structural integrity, and stability in both fuel cell and electrolysis modes. This presentation provides a holistic perspective on scalable production techniques, showcasing the potential of ultrasonic spray coating for advancing large-sized solid oxide electrochemical cells.