Bigger Particle Size Research Articles

Upgrading pyrolysis carbon black by recyclable ferrate/alkaline treatment with the assistance of ultrasound

The recycling of pyrolysis carbon black (CBp) from waste tires is crucial in consideration of the conservation of secondary resources and the alleviation of potential hazardous effects on the environment. However, the high ash content, low surface activity and big particle size limit its high-value utilization, such as the reinforcing of tires. In this work, a novel approach of upgrading CBp derived from waste tires has been developed by a combination of recyclable ferrate/alkaline treatment and ultrasound. In this approach, the ferrate/alkaline is used to remove impurities of CBp and introduce oxygen groups with high activities, and the ultrasound can break the agglutinated CBp particles and accelerate the impurities reduction effectively. Upgrading conditions including temperature, reaction time, and reagent ratio were explored and optimized. Compared with non-upgraded CBp (n-CBp), the upgraded CBp (u-CBp) had a much lower content of impurities (1.74%) and a comprehensive promotion in physicochemical properties. The u-CBp exhibited superior in-rubber performance to the commercial carbon black (N550/N660). Furthermore, the ferrate can be recycled to upgrade CBp several times. This method offered a promising solution of CBp upgrading and waste tire recycling and contribute to the closed-loop recycling of waste tires and environmental sustainability.

A comparative study on the production of Ni1/3Co1/3Mn1/3C2O4 cathode precursor material for lithium-ion batteries using batch and slug-flow reactors

The intermittent nature of the renewable energy sources drifts research interest towards various electrochemical energy storage devices, such as the lithium ion battery, which offers consistent power supply. The manufacturing cost and electrochemical performance of a battery pack largely depends on the quality of the cathode material, which further depends on the production method and its parameters. However, the traditional stirred tank-based co-precipitation manufacturing process for precursors of lithium nickel manganese cobalt oxide (NCM111) cathode suffers from inhomogeneity in the reaction environment, which leads to non-uniform morphology and particle size distribution (PSD). In this work, slug-flow-based manufacturing platform, which offers a homogeneous reaction environment, is used for the continuous production of NCM111 oxalate precursors. One of the novel features of this work is the comparative study between the quality of batch and slug-flow-derived products. The slug-flow-derived product is found to be better in terms of having bigger particle size, narrower PSD and higher tap density. The study on the single and dual-element precipitation in similar conditions to understand the co-precipitation behavior in the slug-flow manufacturing platform is also a unique feature of this work. Furthermore, the effect of NH4OH concentration and residence time (RT) on the electrochemical performance of cathode were also studied and it is found that the cathode precursors synthesized at a NH4OH concentration of 0.08 M and a RT of 2 minutes followed by lithiation shows a better electrochemical performance of 128 mAh g−1 at 0.1 C with cycling stability of more than 80% both at 0.5 C and 1 C.

Effect of influent C/N ratios on high-concentration powder carrier bio-fluidized bed (HPB) process: Performance, sludge characteristics, and microbial community

High concentration powder carrier bio-fluidized bed (HPB) process has demonstrated significant advantages in municipal wastewater treatment. However, the influent C/N ratio as an important factor has not yet been explored in HPB system. In this study, eight parallel sequential batch reactors (SBR) were established to investigate the effect of influent C/N ratio on HPB process, using diatomite powder and FeC powder as carriers, respectively. Process performance, sludge characteristics, and functional microbes under different C/N ratio (2–8) were explored. Results showed that TN removal efficiency reached 48.2 %, 64.3 %, 76.8 %, and 83.3 %, respectively, in diatomite group, and it was stable at 64.0 %, 73.6 %, 80.2 %, and 83.1 %, respectively, in FeC group. The increase in influent C/N ratio improved the denitrification in anoxic period while also enhancing the simultaneous nitrification and denitrification in aerobic period. A higher sludge concentration and a bigger particle size were observed under a higher C/N ratio. EPS content also showed an upward tread with increase in C/N ratio, and EPS content in biofilm was always higher than that in floc sludge in both diatomite and FeC groups. Microbial analysis suggested the activity rate and abundance of denitrifying bacteria was enhanced with increase in C/N ratio, while it declined in nitrifying and anammox bacteria. The rich pore and groups of diatomite promoted the enrichment of nitrifying bacteria. And denitrification process was enhanced by FeC carrier as electron donors and its micro-electrode functions. These results will provide a theoretical basis for operation optimization and engineering practice of the HPB process.

A multi-scale approach to arabinoxylan-based emulsions: From molecular features, interfacial properties to emulsion behaviors

Arabinoxylan (AX) is well-known for its emulsification and beneficial biological activity, but the roles of AX's molecular features and interfacial properties in AX-based emulsion behaviors were unknown. We first used a multi-scale approach to correlate molecular, interfacial, droplet characteristics, and bulk emulsion of AXs from corn and wheat bran (CAXs and WAXs). Our results showed that among CAXs and WAXs solution (1 %, 2 % and 3 %, w/v), 0.25 M NaOH-treated CAX and WAX showed smaller particle sizes (493 nm and 8621 nm), lower interfacial tension and stronger interfacial layer, whose emulsion exhibited smaller initial droplets (541 nm and 660 nm) and better stability. Moreover, WAXs had bigger particle sizes, lower interfacial tension and stronger interfacial layer than CAXs, but CAXs exhibited better emulsifying and emulsion-stabilizing properties than WAXs. There is a satisfactory correlation among CAXs' or WAXs' molecular features, interfacial properties and emulsion behaviors. However, a good correlation from different grains AXs cannot be established.

3D modeling of the airflow and aerosol deposition in the existence of dust

Annually, more than two million deaths are caused due to the exposure of air pollution which cause damage to the lungs and the respiratory system. Topography, light-textured topsoil, drought, and desert climate make Saudi Arabia vulnerable to sand storms and dust. The study aims to examine the deposition of dust particles in the human airway and its relationship to asthma and investigate the possibility that the dust deposition would be changed with different particle size diameters. An idealized upper respiratory tract 3D model was constructed with computer-aided design software. Later a computational simulation was performed using computational fluid dynamics with 3 different sizes (0.03, 2, and 9 microns) of the dust particles to find out the change in airflow velocity and pressure. Our findings revealed that small size particles will travel more with less inertia, whereas bigger size particles will travel less but with higher inertia at airflow rates of 30 L/min. It was found that dust deposition in the respiratory system determines the probability of inhalation and total deposition in the alveoli greatly varies with particle diameter size. An idealized URT model replicate patient-specific URT geometry which helped in finding real-time airflow velocity and pressure of dust particles. Particles with smaller diameter are capable of 100% deposition and inhalation rate at the alveoli, whereas particles with bigger diameter tend to deposit less and with lower inhalation rates at the alveoli.

Response Surface Methodology: A Versatile Tool for the Optimization of Particle Sizes of Cellulose Beads

Synthesis parameters are of utmost importance for controlling the particle sizes of cellulose beads. This study aims to investigate the effects of synthesis parameters e.g., stirring speed (250–1250 rpm), surfactant concentrations (0.5–6.0% w/v), cellulose concentrations (1–5% w/v), and reaction temperature (30-100°C) on the particle sizes for micron-sized cellulose beads (µCBs) as well as other parameters e.g. the volume (1.0 mL) and concentration (0.1–1.0% w/v) of cellulose for nanosized (nCBs) cellulose beads using the response surface methodology (RSM). A total of 27 runs were conducted applying RSM based on the central composite design approach with Minitab-19. Cellulose concentrations were shown to have the most significant effect on both µCBs and nCBs. Under optimized conditions, the minimum and maximum mean particle size of µCBs that could be achieved were 15.3 µm and 91 µm, respectively. The predicted mean particle size for nCBs was obtained at 0.01 nm as the smallest and 200 nm as the biggest particle size under the optimum conditions. This study envisages that RSM and experiments for targeted applications such as biomedicine and agriculture could optimize the particle sizes of cellulose beads.

Impact of the Processing-Induced Orientation of Hexagonal Boron Nitride and Graphite on the Thermal Conductivity of Polyethylene Composites.

Emergent heat transfer and thermal management applications require polymer composites with enhanced thermal conductivity (κ). Composites filled with non-spherical fillers, such as hexagonal boron nitride (hBN) and Graphite (Gr), suffer from processing-induced filler orientations, resulting in anisotropic κ, commonly low in the through-plane direction. Here, the effects of extrusion and compression molding-induced orientations on κ of hBN- and Gr-filled polyethylene composites were investigated. The effect of extrusion on the hBN orientation was studied using dies of various shapes. The shaped extrudates exhibited hBN orientations parallel to the extrusion flow direction, which prompted additional hBN orientation during compression molding. κ of the composites produced with shaped extrudates varied from 0.95 to 1.67 W m-1 K-1. Pelletizing and crushing the extrudates improved κ, by exploiting and eliminating the effect of extrusion-induced hBN orientations. Gr-filled composites showed better κ than hBN composites due to the higher intrinsic conductivity and bigger particle sizes. A maximum κ of 5.1 and 11.8 W m-1 K-1 was achieved in composites with oriented hBN and Gr through a thin rectangular die and stacking the sheets to fabricate composites with highly oriented fillers.

Ni-Cr Layered Double Hydroxide/Microcrystalline Cellulose Composite as Adsorbents for Malachite Green Dye

Malachite green dye in industrial wastewater can be removed by the adsorption method. The adsorbents used in the adsorption method were Ni-Cr LDH, microcrystalline cellulose, and Ni Cr LDH/microcrystalline cellulose composite. Regeneration process of malachite green dye with the Ni-Cr/microcrystalline cellulose adsorbent resulted in the adsorbent having the highest percent adsorbed when compared to Ni-Cr LDH and microcrystalline cellulose adsorbents. This is proof that Ni-Cr/microcrystalline cellulose LDH composite adsorbent can be used repeatedly as much as five cycles. Ni-Cr LDH material and Ni-Cr/microcrystalline cellulose LDH composite were synthesized by the coprecipitation method and were successfully carried out by XRD characterization to see the stability of the structure. The results of XRD characterization of Ni-Cr/microcrystalline cellulose composite showed peaks at diffraction angles of 11°(003), and 60°(110) which are typical regions of LDH and at diffraction angle of 22°(020) which is a typical area of microcrystalline cellulose material. Ni-Cr LDH, microcrystalline cellulose and Ni-Cr/microcrystalline cellulose get optimum pH at 7 with wavelength malachite green at 618.8 nm, kinetic equation following PSO and isotherm following Freundlich with capacity maximum until 129.870 mg.g−1. FT-IR spectra display groups found in LDH and composites including O-H, NO3−, M-O also microcrystalline cellulose have groups C-O and C-H. SEM characterization found out the biggest particle size is 1,954 µm as much as 72 and EDX composite material contains elements of O, C, Ni, Cr, Na, and N.

English

Starch fillers were extracted from three plant sources namely amora tuber, Tacca lentopeteloides; sweet potato, Ipomoea batatas; yam starch, Dioscorea rotundata and their particle size, pH, amylose, and amylopectin percentage decomposition determined accordingly. The starch was introduced into natural rubber in liquid phase (through gelatinization) by the latex compounding method and compounded according to standard method. The prepared starch/natural rubber composites was characterized by Instron Universal testing machine (UTM) for tensile mechanical properties. The composites was further characterized by x-ray diffraction and crosslink density analysis. The particle size determination showed that amora starch granules has the smallest particle size (156 × 47 μm) followed by yam starch (155 × 40 μm) and then sweet potato starch (153 × 46 μm) with the biggest particle size. The pH test also revealed that amora starch has a near neutral pH of 6.9, yam 6.8, and sweet potato 5.2 respectively. Amylose and amylopectin determination showed that yam starch has a higher percentage of amylose (29.68), followed by potato (22.34) and then amora starch with the lowest value (14.86) respectively. The tensile mechanical properties testing revealed that yam starch produced the best tensile mechanical properties followed by amora starch and then sweet potato starch. The structure, crystallinity/amorphous nature of the product composite was confirmed by x-ray diffraction, while the nature of crosslinking was confirmed by swelling test in toluene solvent using the Flory-Rehner approach. The increasing values of crosslink density in the starch/rubber composite is a clear evidence of good interfacial adhesion between the starch fillers and the rubber, hence good dispersion of starch fillers in the rubber. This research has rendered a workable strategy for enhancing interfacial interaction between a hydrophilic filler (Starch) and hydrophobic polymeric matrix (natural rubber) yielding moderately good tensile mechanical properties with prospects for the rubber processing industry. The studied fillers can partially replace carbon black as natural rubber fillers with reduced cost, no risk to human health and also an environment friendly approach. Key words: Natural rubber, fillers, starch, amylose, amylopectin, crosslink density, mechanical properties.

Pebax mixed matrix membrane with bimetallic CeZr-MOFs to enhance CO2 separation

Amine-functionalized and metal doped metal–organic frameworks (MOFs) will enable further enhancement of CO2 adsorption, which holds great promise in mixed matrix membranes (MMMs) for CO2/N2 separation. Four kinds of UiO66 with different sizes have been successfully fabricated by introduction of Ce and/or amino groups in UiO66. The influence of Ce doping on the UiO66 is greatly related to the ligand. Compared with ZrUiO66, the CeZrUiO66 has bigger particle size, lower BET specific surface area and pore volume and a worse CO2 adsorption capacity. Interestingly, the tendency of Ce-doped ZrUiO66-NH2 is contrary to the aforementioned. In particular, bimetallic CeZrUiO66-NH2 has an ultramicroporous structure, small particle size, rich crystal defect, superb CO2 capture capacity and high CO2/N2 adsorption selectivity, suggesting that the simultaneous introduction of Ce and amino groups is conducive to the enhancement of CO2 separation. The intrinsic ultramicroporous structure of CeZrUiO66-NH2 not only offers fast and low resistance transport channels for CO2, but also supplies more sites for CO2 adsorption owning to the doping of Ce and the amino groups. As a result, Pebax/CeZrUiO66-NH2 (3 wt%) MMMs show the CO2 permeability of 100.7 Barrer and the CO2/N2 ideal selectivity of 76.4, which is close to Robeson upper bound from 2008. Meanwhile, the Pebax/CeZrUiO66-NH2 (3 wt%) MMMs present relatively good pressure resistance, which would be advantageous in terms of industrial application.

Physical, Mechanical and Thermal Insulation Properties of Foam Made from Natural Rubber Compounded with Ground Rice Husk

This research attempted to prepare thermal insulation material made of naturally occurring products. Natural rubber (NR) foam comprised of ground rice husk as a filler was practically investigated. STR 5L played as a solid commercial NR was mixed with various chemicals on a two-roll mill. Dicumyl peroxide (DCP) and di-nitroso pentamethylene tetramine (Supercell DPT) were employed as curing and blowing agents, respectively. Physical, mechanical and thermal insulation properties of NR composite foams were studied with various particle sizes (mesh 40 and 60) and quantities (0-80 phr) of the ground rice husk. Cure characterization and preparation of all NR compounds were performed at 160 °C. As a result of tensile properties, the bigger particle size (mesh 40) and the highest amount of the ground rice husk at 80 phr resulted in the maximum tensile strength and elongation at break (%) of the NR composite foams. The thermal insulation property of the NR composite foams carried out by ASTM C177 revealed that the lowest thermal conductivity among three representative NR formulations was found to be 0.0862 W/m.K for the NR foam reinforced with the ground rice husk mesh 40 at 20 phr. Closed cell NR composite foam with a smaller amount of ground rice husk particles provides good compressive strength and heat insulation properties but not good tensile properties.

Non-toxic, high selectivity process for the extraction of precious metals from waste printed circuit boards

The work presented here focused on the extraction of gold (Au), silver (Ag) and palladium (Pd) from electronic waste using a solution of ammonium thiosulfate. Thiosulfate was used as a valid alternative to cyanide for precious metal extractions, due to its non-toxicity and high selectivity. The interactions between sodium thiosulfate, total ammonia/ammonium, precious metal concentrations and the particle size of the waste printed circuit boards (WPCBs) were studied by the response surface methodology (RSM) and the principal component analysis (PCA) to maximize precious metal mobilization. Au extraction reached a high efficiency with a granulometry of less than 0.25 mm, but the consumption of reagents was high. On the other hand, Ag extraction depended neither on thiosulfate/ammonia concentration nor granulometry of WPCBs and it showed efficiency of 90% also with the biggest particle size (0.50 < Ø < 1.00 mm). Pd extraction, similarly to Au, showed the best efficiency with the smallest and the medium WPCB sizes, but required less reagents compared to Au. The results showed that precious metal leaching is a complex process (mainly for Au, which requires more severe conditions in order to achieve high extraction efficiencies) correlated with reagent concentrations, precious metal concentrations and WPCB particle sizes. These results have great potentiality, suggesting the possibility of a more selective recovery of precious metals based on the different granulometry of the WPCBs. Furthermore, the high extraction efficiencies obtained for all the metals bode well in the perspective of large-scale applications.

Effects of nanoparticle types and internal phase content on the properties of W/O emulsions based on dual stabilization mechanism

In this study, water-in-oil (W/O) Pickering emulsions stabilized by different interfacial nanoparticles (ethyl cellulose-EC, whey protein isolate-WPI, Zein) and oleogel networks (glycerin monostearate) were constructed. The influence mechanism of different nanoparticles and oleogel networks under different internal phase fractions on the properties of emulsions was explored. Among different nanoparticles, EC nanoparticle had the smallest particle size (187.03 ± 2.23 nm) and highest contact angle (64.63 ± 2.94°), while Zein and WPI nanoparticles had bigger particle size (287.00 ± 5.54 nm and 213.77 ± 12.90 nm) and lower contact angle (59.71 ± 3.22° and 62.76 ± 1.47°). Microstructural observation revealed that the nanoparticles were located at the interface and in the water droplets, and the nanoparticles could aggregate into network structures. The oil phase had compact gel structures, which surrounded the water droplets. FTIR further proved that the interaction between interfacial particles and oleogel network was dominated by hydrogen bonding and hydrophobic interaction. Both nanoparticle type and water volume affected the rheological properties of the emulsions. Comparatively, EC-based emulsions had the highest shearing viscosity, creep recovery rate and storage modulus. The increase in water phase volume led to higher viscoelasticity, higher centrifugal stability and oil holding capacity of the emulsions. Upon heating, Zein-based emulsions presented the most significant phase separation and decrease in storage modulus. These findings suggested a dual stabilization mechanism for W/O emulsions, and both the nanoparticles and oleogel networks assisted in stabilizing the emulsions. The knowledge obtained in this study would be helpful in developing functional low-fat food and hydrophilic ingredient delivery systems.

Waste Plastic Nanomagnetite Pour Point Depressants for Heavy and Light Egyptian Crude Oil.

One of the most widely used plastics in the world's rapidly urbanizing population is polyethylene (PE). Globally, there is a growing demand for plastics. Polyethylene plastics do pollute and harm the environment. Although polyethylene is said to be nonbiodegradable, any chemical deterioration can take hundreds of years. This study intends to improve the crude oil property, precisely its pour point, by using polyethylene derived from waste products with magnetic nanoparticles (MNPs) and applying it to heavy and light crude oils. Forty crude oil samples were prepared by changing the PE additive concentration from 0.25 to 2% with 0-2.0% MNP concentration. Dynamic light scattering (DLS), gas chromatography, and photomicrographic techniques were employed during the study. DLS results revealed that nanoparticles of heavy (B) crude oil have bigger particle sizes than light (A) crude oil samples, and the overall distribution of the added nanoparticles was much better in light crude oil than in heavy crude oil. The photomicrographic results revealed that the treated samples using additives provided a significant wax crystal reduction compatible with the provided pour point results. The prepared sample of the treated light (A) crude oil provided a more extraordinary rheology performance than the heavy (B) crude oil. Moreover, prepared crude oil samples with PE additives and MNPs are effective as pour point depressants.

Experimental investigation of single wood particle combustion in air and different O2/CO2/H2O atmospheres

This work aims to obtain experimental data of the combustion behavior of single wood particles under oxyfuel conditions relevant for grate incineration facilities. The objectives are to derive insights on how the application of the oxyfuel technology affects the conditions in the fuel bed in grate firing systems and to generate an experimental data basis for simulation activities. Therefore, combustion experiments of single spherical particles with 4 mm, 6 mm and 8 mm diameter have been performed with varying O2 concentrations (10–50 vol-%) in O2/CO2, O2/CO2/H2O and O2/H2O atmospheres at 900 °C. The duration of the characteristic stages of the thermal conversion process, volatile and char combustion, has been investigated by means of recording videos with distinct frame rate. Additionally, the temperature of the flame as well as the particle has been measured throughout the combustion process. It has been found that the total combustion times of the particles under oxyfuel conditions at 21 vol-% oxygen in dry and wet atmospheres are generally shorter compared to the respective air cases throughout all particle sizes. Increasing the oxygen concentration further reduces the combustion durations. At the same oxygen concentration, the temperature of the volatile flame is increased during oxyfuel combustion compared to air conditions. Comparable particle temperatures during char combustion under air conditions have been measured at 30 vol-% oxygen under oxyfuel conditions. In general, both temperatures increased with rising oxygen concentration and the smallest particles did show the highest values. However, the smallest particles were more strongly affected by the changes in the atmosphere causing higher differences in the measured temperatures. Addition of 40 vol-% steam had a decreasing effect on the temperatures with higher extent at the bigger particle sizes. However, increasing the steam concentration to 70 vol-% at the same oxygen concentration caused higher temperatures.

EFFECT OF PARTICLE SIZE ON SIMULTANEOUS CALCINATION AND SULFATION OF LIMESTONE

The simultaneous calcination and sulfation characteristics of limestone in simulative CFB flue gas atmosphere is examined using a slidable tube furnace system combined with X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) with a focus on the effect of particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is further analyzed based on the effect of temperature and CO&lt;sub&gt;2&lt;/sub&gt; concentration. The qualitative and quantitative results show that calcination reaction dominates in the early simultaneous calcination and sulfation reaction of limestone and the predominant effect transforms from calcination to sulfation reaction in the late simultaneous reaction of limestone. Compared with small particle size limestone, the big particle size limestone slows the weight loss rate and weight gain rate and needs more time to achieve the lowest weight point. This is related to lower mole fraction loss rate of CaCO&lt;sub&gt;3&lt;/sub&gt; and mole fraction gain rate of CaSO&lt;sub&gt;4&lt;/sub&gt; during simultaneous calcination and sulfation of limestone with big particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is mainly due to the change of reaction specific surface area, heat transfer, and mass transfer from the surface to the inside of limestone with different particle sizes.

Sodium Alginate-Quaternary Polymethacrylate Composites: Characterization of Dispersions and Calcium Ion Cross-Linked Gel Beads.

The objective of this work was to examine the effect of quaternary polymethacrylate (QPM), a water-insoluble polymer with a positive charge, on the characteristics of the sodium alginate (SA) dispersions and the calcium alginate (CA) gel beads containing propranolol HCl (PPN). The SA-QPM composite dispersions presented the formation of flocculates with a negative charge due to the electrostatic interaction of both substances. The QPM addition did not affect the SA dispersions' Newtonian flow, but the composite dispersions' viscosity enhancement was found. The PPN-loaded CA-QPM gel beads had more spherical than the PPN-loaded CA gel beads. The incorporation of QPM caused a bigger particle size, higher drug entrapment efficiency, and greater particle strength of the gel beads. Despite the similar water uptake property, the PPN-loaded CA-QPM gel beads displayed lower burst release and slower drug release rate than the PPN-loaded CA gel beads. However, the drug release from the PPN-loaded CA-QPM gel beads involved drug diffusion and matrix swelling mechanisms. This study demonstrated that adding QPM into the SA dispersions leads to a viscosity synergism. The CA-QPM gel beads display a good potential for use as a bioactive compound delivery system.

Rheological behavior, mechanical properties, fire resistance, and gamma ray attenuation capability for eco-friendly cementitious mixes incorporating thermally treated lead sludge

The main objective of this study is to develop eco-friendly innovative binding materials based on lead sludge (sludge generated during glass polishing) for various advanced applications. The challenge with using lead sludge (LS) in cementitious blends is the presence of a considerable quantity of organic matter, which has a detrimental impact on the workability and mechanical characteristics of such blends. As a result, this study focused on comparing the influence of untreated and thermally-treated LS (ULS and TLS, respectively) on rheological behavior, mechanical characteristics, fire resistance, and harmful gamma-radiation shielding for various cementitious mixes. When compared to ULS, the results demonstrate that TLS has a greater pozzalnicity (as evaluated by modified Chapelle and Abo-El-Enein et al. methods), a bigger particle size (as established by particle size distribution and SEM analysis), and no organic matter content (as determined by FTIR technique). TLS incorporation in cement composite enhanced rheological parameters (lowest yield stress and plastic viscosity values) through eliminating organic matter that may adsorb a large amount of water. The specimen containing up to 20 % TLS achieved significant compressive strength value because it improved by 45.3 % when compared to ULS. This may be attributed to improved workability followed by a decrease in the water/solid ratio (as determined by the water consistency test), decomposition of organic matter that impedes the hydration process, and high pozzolanicity, which resulted in the creation of additional hydration products as confirmed by TGA/DTG and SEM/EDX analyses, as well as pore structure redistribution from macro to meso-pores validated by textural characteristics study(N2 adsorption/desorption isotherm) and total porosity measurement. The composite containing 10 wt% TLS had the best fire-resistant behavior up to 900 °C; it has a compressive strength that is 15.8 and 57.1 wt% greater than OPC and a specimen containing 10 % ULS, respectively. Although TLS-containing composites displayed excellent mechanical characteristics, ULS-containing composites exhibited exceptional radiation shielding properties because the organic matter, when exposed to gamma-rays, may be transformed into a cross-linked structure that reduces radiation intensity. The immobilization test was developed to guarantee the safety of produced composites. It was discovered that both ULS and TLS specimens had a Pb-concentration in leachate solution that was lesser than the toxicity limit (5 ppm). The immobilization process in TLS-containing specimens is more effective than in ULS; rather than narrow pores identified in TLS-containing specimens, the PbO2 was transformed to stable Pb3SiO5, as shown by XRD.

A green dual-phase carbon-silica nanohybrid derived from black liquor lignin for reinforcing styrene-butadiene rubber

In rubber industry, lignin has been investigated as a potential alternative of fossil-derived carbon black (CB) for several decades. However, due to poor dispersity, big particle size and incompatibility with rubber, lignin cannot achieve the same reinforcing effect as CB by direct dry mixing. Here, a new and green dual-phase carbon-silica nanohybrid (LDPCS) was successfully prepared from black liquor lignin (BLL) and sodium silicate through a simple co-gelation/self-assembly and carbonization process. The preparation mechanism and process as well as the morphology and properties of LDPCS were investigated and discussed in detail. The results indicated that the hydroxymethylation and silane modification of BLL could improve its affinity with SiO2 sols, thus facilitating the co-gelation of BLL and SiO2 sols to inhibit the growth of SiO2 particles. During subsequent acid precipitation, silane modified hydroxymethylated BLL (SiHM-BLL) was self-assembled around SiO2 particles to form nanosized SiHM-BLL-SiO2 hybrids. After carbonization, SiHM-BLL-SiO2 nanohybrids were converted into LDPCS with small primary particle size of 60–90 nm, high specific surface area of 82.19 m2/g, relatively loose secondary aggregation structure and graphitic microcrystals in the carbon framework. With incorporating LDPCS into styrene-butadiene rubber (SBR) by direct dry mixing, LDPCS showed a superior reinforcing capability for SBR as compared with CB, which was ascribed to the nanoscale dispersion of LDPCS, robust C/SiO2 interfaces and high affinity with SBR matrix. This work provided a new insight into the fabrication of novel hybrid nanofiller from lignin and broadened the potential applications of lignin in rubber compounds and beyond.

Effect of micro-magnesium oxide admixture on rheological and compressive strength properties of class G well cement

Rheological property tuning is one key aspect of oil-well cement, not only affecting the cement slurry placement but also indirectly impacting other cementing properties such as the bonding strength and compressive strength. However, the research is scant on the rheological properties of blending magnesium oxide with class G oil-well cement, despite some studies having been conducted on its impacts on shrinkage compensation, compressive strength, bonding strength, and permeability properties of oil-well cement. This work studies the effects of micro-sized magnesium oxide on the rheological properties and compressive strength of the formulated API Class G oil-well cement slurries. Two types of micro-sized magnesium oxide (50 μm and 100 μm) were used as the mineral admixture at different dosages (3%, 9%). The base formulated slurry sample was incorporated with the silica flour and several commercialized additives such as retarder, fluid loss control agent, and defoamer. A batch of flow tests have been conducted by the use of a digital viscometer at two different temperatures, 25 and 88°C. The compressive strength has also been measured after curing the samples with the same formulation and conditions for 7 days. The variations of the rheological properties (plastic viscosity, yield stress, and gel strength), shear stress–shear rate correlations, and shear-thinning/thickening behavior are impacted by the temperature, the type, and dosage of magnesium oxide. The plastic viscosity of the tested slurries decreased by 27.0% (type II, 9%, 25°C) and 15.1% (type II, 3%, 88°C), respectively, and the yield stress increased by 258.5% (type II, 3%, 88°C) and 53.9% (type II, 9%, 25°C). The gel strength generally increases as the magnesium oxide dosage increases. However, all tested slurry samples show shear-thinning behavior and non-Newtonian characteristics. Among the tested slurry samples, it is found that better rheological performance is achieved when incorporating magnesium oxide with a smaller particle size. On the other side, the specimens of mixed magnesium oxide with a bigger particle size and medium dosage outperform their rival with a smaller particle size in compressive strength.