Mesh Particle Size Research Articles

Exploring the Adsorption Efficiency of Local Apricot Seed Shell as a Sustainable Sorbent for Nitrate Ion

Locally available apricot seed shell as agro-waste was used for the preparation of adsorbents. The biochar was prepared at 370°C via pyrolysis and 80 mesh particle sizes were modified by 1N HCl. Nitrate adsorption and effect of co-ions from aqueous solution were studied under batch model using apricot seed shell powder (ASSP), apricot seed shell biochar (ASSB), and activated apricot seed shell biochar (AASSB). FTIR and pHPZC measurements were used to characterize the adsorbents. Based on the experimental findings, the optimum conditions follow pH 2, 0.3g dosage, initial concentration of 50 mg.L-1, and contact time of 90 min. The three forms of adsorbent exhibited good adsorption for nitrate. However, the maximum percentage removal of nitrate ions from the aqueous solution followed the order AASSB>ASSB>ASSP. The adsorption kinetic of nitrate ion was best fitted by pseudo 2nd order, and the parameters of adsorption isotherms elucidated favorable and improved sorption. This agro-waste could be used to develop sustainable adsorbents in water and wastewater treatment methods and has great potential to replace commercially available sorbents.

Evaluation of adsorption isotherms and kinetics of anionic pollutant in water using biochar derived from locally available agro-waste

The uses of agricultural byproduct solid wastes to develop low cost sorbents are advantageous and promising for the removal of water contaminants. It serves the purposes of both environmental remediation and appropriate management of agricultural waste generated during agricultural processing. In this study, locally available apricot seed shell and Salix Alba leaves were utilized as agro-waste for the preparation of adsorbents. The biochar was prepared at 300-370oC via pyrolysis and 80 mesh particle sizes were modified by 1N HCl. The unmodified and acid modified local Salix Alba leaves and Apricot seed shell biochar were used to study the adsorption of chloride ion in water, which can damages appliances of industries and also poses health issues at elevated concentration. Adsorption kinetics and equilibrium studies were conducted at pH 7. The adsorption efficiency of modified biochar was much higher than the unmodified biochar due to induce surface positive charge. The Langmuir maximum adsorption of modified Salix Alba leaves sorbent was found to 22.98 mg/g, while modified Apricot seed shell biochar was found 25.83 mg/g. The experimental data were simulated and applied to fit Langmuir, Freundlich isotherm, pseudo 1st and 2nd order kinetics models and found a better compliance with Freundlich isotherm model and pseudo 2nd order kinetics model.

Effect of Varied Cure Temperature on the Cure Behavior, Mechanical Properties and Heat Build-Up of Solid Tire Tread Compound Containing Different Particles Sizes of Ground Tire Rubber

This work investigates the effect of variation in vulcanization temperature on the cure behavior, tensile properties, tear strength, hardness, Akron abrasion loss and heat build-up of vulcanized tire tread compound in which the total rubber was replaced with 10% and 20% ground tire rubber (GTR) of 40, 60 and 80 mesh sizes. The first step was the characterization of the GTR using optical microscopy and a thermogravimetric analyzer. The first step of mixing each rubber compound was carried out using an internal mixer (Brabender) at 60°C and 40 rev/min rotor speed and the second step was done on a two-roll mill. The mooney viscosity of each rubber compound was investigated. the cure behavior of the rubber compounds was studied at 140°C, 150°C, and 160°C respectively. Results show that the introduction of GTR reduced vulcanization time, while increased cure temperature resulted in a lower vulcanization time. No significant difference was observed in the vulcanization time at a particular temperature of the rubber sample with different particle sizes and varied amounts of GTR. The introduction of ground tire rubber in the rubber vulcanizate however resulted in decreased tensile strength, tear strength and elongation, and increased hardness, abrasion resistance, modulus and heat build-up. An increase in the vulcanization temperature from 140°C to 150°C and 160°C did not impart a significant reduction in the tensile strength of the vulcanizates containing GTR. Vulcanization at higher temperatures resulted in reduced hardness, and modulus, slightly increased abrasion loss and increased elongation of the vulcanizates containing GTR. The heat build-up increased as the cure temperature increased. Generally, the control sample with no content of ground tire rubber exhibited the best properties. If GTR is to be introduced in rubber matrix at an amount up to 20%, the results suggest that 60 mesh size particles will impart better properties. The optimal vulcanization temperature recommended based on the findings from the work is 150°C.

Optimization of Chlorophyll Extraction from Ulva Sp. with Ultrasound-Assisted Liquid Biphasic Systems Method

Ulva sp. is a type of green algae that is easily found in the shallow seas of Indonesia and contains various bioactive compounds. Chlorophyll is a bioactive compound that functions as a natural dye, free radical scavenger, and antioxidant in the body. Chlorophyll extraction with conventional methods requires a relatively long time and large amount of solvent. In this research, chlorophyll extraction from Ulva sp. with the Ultrasound-Assisted Liquid Biphasic System (UALBS) method. Ulva sp. as much as 2.5 grams mixed in acetone solvent, added K2HPO4 solution, and carried out the sonification process in a dark room. The extraction process performs at a parameter range of 5-15 minutes, ratio 0.05-0.1 g/mL, and 60-100 mesh particle size. The extracted filtrate was added with petroleum ether and distilled water to form a biphasic condition. The extracted chlorophyll was analyzed with chromatography and spectrophotometry method. Antioxidant activity was analyzed using the DPPH method. The optimum result of Ulva sp. chlorophyll extraction at an extraction time of 10 minutes, the ratio of solids to solvent was 0.1, the particle size of 60 mesh produced a yield of 1.88% with chlorophyll a 20.13664%, chlorophyll b 21.58672% and total chlorophyll 41.71012%, and the percentage inhibition 45.32%.

Preparation of expandable flake-graphites with different particle sizes and their flame-retardant application for polypropylene

Bisulfate intercalated graphites with different particle sizes were prepared by a chemically oxidative method using natural flaky graphites as raw materials. The morphology and structure of the expandable graphites were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction patterns, and scanning electron microscope. The effect of the particle size on the expanded volume was also investigated. Expandable graphite with +100 mesh particle size (EG100) showed the highest expanded volume of 225 mL/g. Moreover, a combination of expandable graphite, red phosphorus (RP), and melamine cyanurate (MC) into a polypropylene (PP) matrix exhibited a synergistic flame retardant effect. The composite loading EG100, RP, and MC with a mass ratio of 1:1:1 and a total filler content of 18 wt.% achieved a UL94 V-0 rating and a limiting oxygen index (LOI) of 28.9 %. The effect of particle size of expandable graphite on the mechanical properties was also evaluated.

The Utilization of Candlenut Shell-Based Activated Charcoal as the Electrode of Capacitive Deionization (CDI) for Seawater Desalination

Activated carbon or activated charcoal is one of the best materials that can be used as a constituent of CDI electrodes, not only because of its various advantageous properties but also because it can be sourced abundantly from plant waste. This research aims to determine the effect of the thickness of the candlenut shell activated charcoal electrode and the particle size of the activated carbon used on the capacitive deionization (CDI) performance in seawater desalination. Candlenut shell-based activated charcoal is obtained in three stages, namely preparation, carbonization, and activation. The carbonization stage was done by using a pyrolysis reactor at a temperature of 400°C for 8 hours. The activation was done with the activator of H3PO4 67%. The variation of thickness was 6 mm, 8 mm, 10 mm, and 15 mm while the variation of particle size was 60 mesh, 80 mesh, 100 mesh, and 200 mesh. The results showed that the higher capacitance was obtained with the thinner electrodes, where the best value was the thinnest electrode, 6 mm, which produced the highest capacitance, 122.96 nF. For the desalination of seawater, it is shown that the finest particle/smallest particle size will result in the best desalination performance, where 200 mesh particle size will result in the decrease of salinity from 34% to 4%. That is 88.23% decrease in salinity. Therefore, the using of candlenut shell-based activated carbon as the electrode in CDI is proven to be able to obtain good performance in seawater desalination.

Synthesis of calcium propionate from indigenous limestone from Swat area in Pakistan

In this study, native limestone from the Swat area of Pakistan was used for the synthesis of calcium propionate. The powdered limestone was allowed to react with propionic acid and the effect of the synthesis parameters, that is, the particle size (50, 100, 150, and 200 mesh), propionic acid (10, 15, and 30 %), solid-liquid ratio (0.1:10, 0.12:1, 0.14:1, and 0.16:1), reaction time (1, 1.5, 2, and 2.5 hours) and the temperature (60, 80, 90, and 100 °C) on the percentage yield and purity of calcium propionate was studied. The results showed that the optimum synthesis parameters were 200 mesh particle size, 15% propionic acid concentration, 0.14:1 solid-liquid ratio, 2.5 hours reaction time, and 80 °C temperature. The product obtained under optimal conditions was characterized by infrared spectroscopy, thermogravimetry, and scanning electron microscopy. The results revealed that a product having ≥ 99.8% purity with 85% yield can be obtained by this process.

Optimization of extrinsic parameters for beneficiation of coal with the help of Cronobacter sp

ABSTRACT Beneficiation increases the calorific value of low-grade coal and extracts environmentally sensitive elements. Bacteria may be used as eco-friendly coal cleaning tool, but the treatment is influenced by several extrinsic and intrinsic factors. This study examined five extrinsic factors, namely particle size of coal, pulp density, bacterial biomass concentration, number of bacterial beads (immobilized bacterial cells) and the duration of treatment. For optimization, the test runs were designed using Taguchi L16 orthogonal array, determining optimal values through S/N ratio analysis and individual parameter contribution using ANOVA. The optimal conditions obtained for sub-bituminous coal beneficiation using Cronobacter sp. are 80–120 mesh particle size, 30% pulp density, 750 mg bacterial biomass/g coal, 25 bacterial beads, and six days of treatment resulting in 13.36% ash yield reduction. Particle size had the highest impact (69.4%), followed by treatment duration (13.1%), pulp density (6.3%), bacterial biomass (6.3%), and bacterial bead number (4.8%). A regression model attributed only 42% influence of these extrinsic factors on inorganic removal from coal. Therefore, further research on other factors, particularly intrinsic ones, in inorganic matter liberation is imperative. These findings can be used for designing experiments that optimize the extraction of cleaner fuel from various types of low-grade coal.

Evaluation of tensile strength of fibreglass composites-hybrid due to differences in sand size

Hybrid composites are a combination of two or more types of fibers to create alternative materials. Therefore, this study aimed to investigate the potential of hybrid fiber-particle composites to acquire new tensile properties derived from both types of fibers and particles. In this study, CSM300 glass fiber reinforcement was combined with sand, incorporating varying particle sizes to create a hybrid fiber reinforcement system. The analysis was carried out using five variations of sand particle sizes at 12, 16, 20, 24, and 40 (mesh size). The layers were arranged as RS+FG-SP-FG+RS (resin + fiberglass - sand particle #12, #16, #20, #24, #40 - resin + fiberglass), each incorporated in polyester resin using the manual press molding method at room temperature. The results showed that the highest tensile strength of the hybrid system (RS+FG-SP#16-FG+RS: 49.49 MPa) was achieved by combining both types of glass fiber and sand with #16 (sand mesh size). Furthermore, the maximum yield stress of 44.84 MPa and percent elongation of 10.17% were obtained at #16 and #12 sand mesh size, respectively. Research limitations/implications: The tensile strain-to-failure showed a significant increase from 0.22% at the beginning of the mesh particle size variation and reached a maximum for the fiberglass hybrid composite at #16 sand mesh particle size. For practical implications, the utilization of this technology requires the critical adjustment of sand diameter for industrial hybrid composite applications to achieve desired product specifications. Generally, the tensile index showed an increase at the initial sand size, reaching its peak at 0.35 mm (#16), followed by a decrease as the sand diameter is refined, with increasing mesh size.

Effect of adhesive concentration and particle size on the quality of hazelnut shell briquettes with glutinous rice adhesive

One alternative energy that can be used as a substitute for fuel oil and gas is biomass energy such as briquettes. This study aims to determine the amount of heat, moisture content and ash content of briquettes made using hazelnut shells and glutinous rice adhesives that vary in adhesive concentration and particle size. This study used a complete randomised design (CRD) with variations in glutinous rice concentration of 20%, 30%, and 40% while the particle sizes used were 12 mesh and 24 mesh. The results showed that the adhesive concentration did not significantly affect the test parameters while the particle size affected the moisture content, ash content and calorific value of the briquettes. The highest calorific value was obtained by using 24 mesh particle size with 20% adhesive concentration with a calorific value of 5321 cal/g while the 12 mesh particle size produced the highest calorific value of 4704 cal/g at 20% adhesive concentration. The lowest moisture content value was obtained by using 24 mesh particle size with 20% adhesive concentration with a moisture content value of 6.9% while the 12 mesh particle size produced the lowest moisture content value at 20% adhesive concentration with a value of 7.4%. The lowest ash content value was obtained by using 24 mesh particle size with 30% adhesive concentration with an ash content value of 4.99% while the 12 mesh particle size produced an ash content value of 5.82%. The use of 12 mesh particle size is not in accordance with SNI standards because the heating value produced is still below 5000 cal/gr while the use of 24 mesh particle size is in accordance with SNI standards for all test parameters.

Microwave and enzyme co-assisted extraction of anthocyanins from Purple-heart Radish: Process optimization, composition analysis and antioxidant activity

Purple-heart Radish named “Xinlinmei” is rich in anthocyanins by specific cultivation. In this work, a novel method for synergistic extraction of anthocyanins from Purple-heart Radish was developed by combining microwave-assisted extraction (MAE) with enzyme-assisted extraction (EAE). Integration of MAE and EAE was optimized by screening various enzymes and combination approaches, followed by investigation of process parameters with single-factor experiments and response surface methodology (RSM). The optimized conditions by RSM were as follow: 25.0 g/100 g cellulase dosage, 60 mL/100 mL ethanol concentration, pH 4.0, 50 °C temperature, 7.15 min extraction time, 80 mesh particle size and 60:1 mL/g liquid-to-material ratio, yielding a maximum response predicted and experimental values of 6.292 and 6.125 ± 0.034 mg/g respectively. Based on the synergistic effect, MAE-EAE achieved higher extraction efficiency compared to the other extraction methods such as MAE, UAE and EAE etc. By means of HPLC-Q-Orbitrap/MS and HPLC, 11 anthocyanins extracted were identified and quantified as pelargonins with different glucosides, exhibiting quite homologous fragmentation pattern, biometabolic products and satisfactory yield. The antioxidation capacity of the extracted and purified products was evaluated by DPPH, ABTS and anti-lipid peroxidant assays, suggesting that the anthocyanins purified by the macroporous resin had stronger antioxidant activity. This study provided an efficient and promising approach to improve extraction of the anthocyanins from Purple-heart Radish, and a new source of pelargonins as a powerful antioxidant to be developed.

Feasibility of high-magnesium nickel slag-fly ash as precursor of magnesium phosphate cement and its hydration mechanism

The aim of this study was to investigate the process conditions, hydration reaction products and mechanism of high-magnesium nickel slag (HMNS)-fly ash (FA) as a precursor of magnesium phosphate cement (MPC). The relationships between properties, hydration products, hydration processes, and micromorphology were investigated by engineering properties, XRD, TG-DSC, FT-IR, Raman, and SEM/EDS. The results showed that the optimal process (HMNS/FA = 1.0/0, NH4H2PO4 dosing of 25 wt%, water-cement ratio of 0.26, the maintenance condition is air maintenance, and 200 mesh particle size of raw materials) prepared the cementitious material with 28 d compressive strength of 58.00 MPa and linear expansion rate of only 2.5 %. The hydration process was a multi-stage process, including the dissolution of NH4H2PO4 and pre-treated HMNS (WHMNS), the precipitation of intermediate hydration products and the formation of struvite, and the formation of gelling phases such as -Si-O-P-, -Al-O-P-, and -Si-O-Al-O-P-. Eventually, a high-strength gel-crystal phase structure consisting of gelling phases such as struvite wrapped around unreacted raw materials and struvite crystals was formed. FA was harmful for cementitious material, and impurities and high levels of Ca in FA reacted with phosphate to form hydration products with a loose porous structure (e.g., brushite). The optimal process sample complies with the 52.5R grade of ordinary Portland cement (GB175-2007); its embodied energy was reduced by more than 73.4 % compared to magnesium phosphate cement (MPC), and the corresponding CO2 emission was reduced by more than 74.2 %. Therefore, it has the potential to partially replace MPC from the environmental and feasibility point of view.

The effect of chicken eggshell (Gallus gallus domesticus) particle size as filler to polyester composite as motorcycle’s exhaust pipe cover material

This research was done to know the effect of chicken eggshell (Gallus gallus domesticus) powder particle size on unsaturated polyester resin mechanical properties. The eggshell was mashed and sifted to get the 50 mesh, 70 mesh, 90 mesh, 110 mesh, 130 mesh, 150 mesh, and 170 mesh particle size by using a ball mill. Then, the eggshell was mixed with an unsaturated polyester resin matrix with the ratio of 70:30 and methyl ethyl ketone peroxide (MEKP) catalyst as much as 1 % of the matrix mass. After that, it was pressed by using compression molding. The composite formed was characterized by Scanning Electron Microscopy Energy Dispersive X-ray (SEM EDX), Fourier Transform Infra-Red (FTIR), and X-Ray Diffraction (XRD). The physical properties of the composite were analyzed and the mechanical properties were tested. The SEM EDX result showed that the eggshell and composite were made up of Ca, C, and O, and the polyester was made up of C, O, and Si. The composite highest tensile strength and impact strength were at 150 mesh particle size of chicken eggshell powder which is 45.153 MPa and 9. 04 J/m2.

Pyrolysis of Mixed Date Stones and Pistachio Shells: Identification of Bio-Oil and Utilization of Bio-Char as Activated Carbon Precursor.

Thermal pyrolysis of mixed date stones and pistachio shells in a semi-batch reactor was addressed in this study. The highest yield of liquids (51.20 %) was produced at 500 °C, 90 min, 20 °C/min heating rate, and 50 mesh particle size. Under these conditions, yield of liquid from date stones and pistachio shells separately was 49.12 % and 47.67 %, respectively. The FT-IR results confirmed the presence of multiple oxygen-containing compounds in the bio-oil. Results from GC-MS declared that it was predominately composed of acids (57.57 %), esters (21.35 %), phenols (4.63 5), and alcohols (3.49 5). The obtained biochar was transformed into activated carbon (AC) by the optimized ZnCl2 activation method. The ideal AC was synthesized at 600 °C for 60 min using a 2 : 1 ZnCl2 : biochar impregnation ratio. FESEM and XRD measurements showed that the AC was amorphous. The prepared AC was effective in eliminating dibenzothiophene (DBT) from model fuel (200 ppm DBT/hexane) with a maximum performance 95.26 % at 40 °C for 1h using 0.35 g of the AC. The exhausted AC was regenerated and reutilized 4 times, and removal efficiency reached 88.23 % in the 4th cycle under ideal working conditions.

Effect of chemical structure on mechanical-seepage characteristics of briquette under different heating temperatures

Based on the low strength and high permeability of briquette coal (BC) used in physical simulations of coal mine disasters, we propose a new briquette production method that can improve the mechanical strength and reduce the permeability of BC. The reduction of physical simulation experiments of coal and gas outburst was improved, which is of significance for the prevention and control of coal mine gas disasters. Based on this method, we developed a set of briquette hot-pressing systems and optimized the proportion of coal powder used in the briquette formation process. Mechanical property and seepage tests of the briquettes were carried out under uniaxial and triaxial compression. The effects of different temperatures on the physical (size, density, ignition loss rate) and mechanical (Poisson's ratio, elastic modulus and compressive strength) coal parameters and the effect of the permeability were analyzed using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analyses. The morphology and pore, crystallite, and molecular structures were used to determine the cause of the increase in the mechanical strength of BC. Based on the packing density theory, the optimal ratio of the 40–60, 100–120, and 180–200 mesh particle sizes is 91.77:5.87:2.35. With the increase in the temperature from 150 to 450 °C, the microstructure changes from loose to compact, the number of pores and cracks increase, the degree of order of the microcrystalline structure gradually increases, the distance between the microcrystalline layers d002 continuously decreases, aliphatic chains shorten, and the aromaticity increases. The rate of the change of the loss rate and density of the hot-pressed briquette first increase, then decrease, and then increase again. The mechanical parameters (strength and elastic modulus) first increase and then decrease, whereas the Poisson's ratio first decreases and then increases, and the permeability increases. Considering the density, strength, and permeability of hot-pressed briquettes, the optimal heating temperature at which the similarity between the hot-pressed BC and raw coal is the highest at 300 °C.

Study on the Performance and Mechanism of Cement Solidified Desulfurization Manganese Residue.

Desulfurized manganese residue (DMR) is an industrial solid residue produced by high-temperature and high-pressure desulfurization calcination of electrolytic manganese residue (EMR). DMR not only occupies land resources but also easily causes heavy metal pollution in soil, surface water, and groundwater. Therefore, it is necessary to treat the DMR safely and effectively so that it can be used as a resource. In this paper, Ordinary Portland cement (P.O 42.5) was used as a curing agent to treat DMR harmlessly. The effects of cement content and DMR particle size on flexural strength, compressive strength, and leaching toxicity of a cement-DMR solidified body were studied. The phase composition and microscopic morphology of the solidified body were analyzed by XRD, SEM, and EDS, and the mechanism of cement-DMR solidification was discussed. The results show that the flexural strength and compressive strength of a cement-DMR solidified body can be significantly improved by increasing the cement content to 80 mesh particle size. When the cement content is 30%, the DMR particle size has a great influence on the strength of the solidified body. When the DMR particle size is 4 mesh, the DMR particles will form stress concentration points in the solidified body and reduce its strength. In the DMR leaching solution, the leaching concentration of Mn is 2.8 mg/L, and the solidification rate of Mn in the cement-DMR solidified body with 10% cement content can reach 99.8%. The results of XRD, SEM, and EDS showed that quartz (SiO2) and gypsum dihydrate (CaSO4·2H2O) were the main phases in the raw slag. Quartz and gypsum dihydrate could form ettringite (AFt) in the alkaline environment provided by cement. Mn was finally solidified by MnO2, and Mn could be solidified in C-S-H gel by isomorphic replacement.

Tribological behavior of sintered electrolytic iron‐zinc stearate added compacts

AbstractPowder metallurgy is an effective method to give near net shape to powder particles. In this paper, the influence of powder particle size, lubricant and compaction load on hardness and wear loss has been investigated as it influences the compact. Electrolytic iron powder (250 mesh to 300 mesh and 300 mesh to 350 mesh) with zinc stearate (0 weight % to 2 weight %) was used for preparing the samples. Green samples were prepared by cold compaction process at different loads (400 kN, 450 kN and 500 kN). Pre‐sintering was done at 550 °C. Taguchi′s (L18) mixed level model was used to develop the regression equation for hardness and wear loss. The maximum hardness of 79 HRB was achieved with 300 mesh to 350 mesh particle size and 500 kN compaction load. Minimum wear volume loss was observed with samples having composition of 250 mesh to 300 mesh size electrolytic iron powder at 500 kN compaction load and 1 weight % lubricant content.

Direct Recycling of WC-Co Grinding Chip.

Grinding is a finishing process for high precision, high surface quality parts, and hard materials, including tool fabrication and sharpening. The recycling of grinding scraps, which often contain rare and costly materials such as tungsten carbide (WC-Co), has been established for decades. However, there is a growing need for more energy-efficient and environmentally friendly recycling processes. Currently, grinding sludges, which are a mixture of abrasives, lubricants, and hard metal chips, are only treated through chemical recycling. Direct recycling ("reuse" of chips as raw material) is the most effective but not yet viable process due to the presence of contaminants. This paper presents an oil-free dry grinding process that produces high-quality chips (i.e., oil-free and with few contaminants, smaller than 60 mesh particle size) that can be directly recycled, as opposed to the oil-based wet grinding that generates sludges, which require indirect recycling. The proposed alternative recycling method is validated experimentally using WC-Co chips from a leading hard metals' processing specialized company. The contaminant level (oxygen 0.8 wt.%, others < 0.4 wt.%), granulometry (chip D50 = 10.4 µm with grain size < 3 µm) and morphology of the recycled chips' powder is comparable to commercial powders proving the research and industrial potential of direct recycling. The comparison of sintered products using recycled and commercial powder provided equivalent characteristics for hardness (HRA of 90.7, HV30 of 1430), porosity grade (A02-04) and grain size (<3 µm).

Mechanical Test and Meso-Model Numerical Study of Composite Rubber Concrete under Salt-Freezing Cycle

A composite rubber concrete (CRC) was designed by combining waste tire rubber particles with particle sizes of 3~5 mm, 1~3 mm and 20 mesh. Taking the rubber content of different particle sizes as the influencing factors, the range and variance analysis of the mechanical and impermeability properties of CRC was carried out by orthogonal test. Through analysis, it is concluded that the optimal proportion of 3~5 mm, 1~3 mm, and 20 mesh particle size composite rubber is 1:2.5:5. 5 kinds of CRC and 3 kinds of ordinary single-mixed rubber concrete (RC) with a total content of 10%~20% were designed under this ratio, and the salt-freezing cycle test was carried out with a concentration of 5% Na2SO4 solution. The physical and mechanical damage laws during 120 salt-freezing cycles are obtained, and the corresponding damage prediction model is established according to the experimental data. The results show that: on the one hand, the composite rubber in CRC produces a more uniform “graded” structure, forms a retractable particle group, and reduces the loss of mechanical properties of CRC. On the other hand, colloidal particles with different particle sizes are used as air entraining agent to improve the pore structure of concrete and introduce evenly dispersed bubbles, which fundamentally improves the durability of concrete. Under the experimental conditions, the CRC performance is the best when the overall content of composite rubber is 15%.

Effect of Time, pH, and Yeast Concentration on Bioethanol Levels in the Ulva sp. Fermentation Process

Bioethanol is a form of renewable energy that is used to reduce dependence on the use of fossil fuels which cause various negative impacts on the environment. Ulva sp. contains high carbohydrates so it has the potential as a raw material for bioethanol production. This study aims to determine the optimum conditions of the fermentation process with the variables used time, pH, and yeast concentration. This study used the results of hydrolysis of Ulva sp. with optimum operating conditions of 0.1 N HCl concentration, 80 mesh particle size, and 450 watt microwave power. Measurement of bioethanol levels was carried out using an alcoholmeter. The results showed that the optimal conditions for fermentation were 7 days of fermentation, pH 5.5, and yeast concentration of 1.5% which resulted in a bioethanol content of 7.55%.