Effect Of Mechanical Pretreatment Research Articles

Effect of mechanical pre-treatment on the recovery potential of rare-earth elements and gold from discarded hard disc drives

Effect of mechanical pre-treatment on the recovery potential of rare-earth elements and gold from discarded hard disc drives

Semi-Continuous Testing: The Effect of Mechanical Pre-treatment on Degradation of Complex Organic Matter

This study investigates the impact of pre-treatment intensity on biogas production in anaerobic digestion processes using three different substrates: BPWSB, TWSB, and PWSB. The experimental design includes semicontinuous tests with various pre-treatment levels (PTLs) to analyze specific methane yields and process stability indicators. Reactor performance comparisons reveal differences in methane production profiles among substrates, with GWSB generally outperforming BPWSB and PWSB. Additionally, PTL4 consistently yields higher specific methane yields than PTL3 and PTL2 across all substrates due to its greater surface area. The specific methane yields for BPWSB, TWSB, and PWSB are comparable but not identical. The highest specific methane yield was produced by BPWSB for PTL2 (M=225.6, SD=57.7), while the lowest was produced by GWSB (M=181.2, SD=51.9). The results suggest that the specific methane yields for BPWSB, TWSB, and PWSB are similar but not identical. Again, BPWSB PTL3 (M=255, SD=63.5) differed significantly from the others, whereas GWSB had the lowest specific methane yield (M=211.7, SD=56.6). Likewise, BPWSB PTL4 outperformed the other substrates (M=290.3, SD=69.3), while GWSB PTL4 had the least (M=218.3, SD=69.4). Intensive pre-treatment shows no detrimental effects on system stability, with reduced foaming tendency observed at higher pre-treatment intensities. These results indicate that carefully choosing pre-treatment methods can boost methane yields while addressing operational difficulties, emphasizing the significance of pre-treatment in sustainable waste management and renewable energy generation. Future studies could investigate further pre-treatment methods and their long-term impacts on biogas output and system stability, offering more comprehensive insights into process refinement.

Macrokinetics of thermal explosion in a 3Ni-Al system mechanically activated in a low-energy mill

Two-step mechanosynthesis in the 3Ni - Al system has been investigated by experimental and theoretical methods using the developed macrokinetic theory of mechanochemical synthesis (MS). The first step included the grinding and mechanical activation (MA) of the starting reaction mixture in the mill, and the second step included the explosive synthesis of the Ni3Al intermetallic compound outside the mill. The effect of mechanical pre-treatment on the temperature-time parameters of the synthesis of the Ni3Al intermetallic compound was found. The phase composition of the activated mixture of nickel, aluminum, and synthesized products was characterized by X-ray diffraction. Preliminary low-energy mechanical activation (LEMA) of the mixture in a laboratory mill eliminates the negative phenomena associated with the grinding and formation of intermediate phases. Kinetic and thermophysical constants characterizing the two-step MS were determined using the inverse problem. The contribution of mechanical activation factors to the acceleration of Ni3Al synthesis was quantitatively evaluated.

Effect of Mechanical Pretreatments on Damage Mechanisms and Fracture Toughness in CFRP/Epoxy Joints.

Adhesive bonding of carbon-fiber-reinforced polymers (CFRPs) is a key enabling technology for the assembly of lightweight structures. Surface pretreatment is necessary to remove contaminants related to material manufacturing and ensure bond reliability. The present experimental study focuses on the effect of mechanical abrasion on the damage mechanisms and fracture toughness of CFRP/epoxy joints. The analyzed CFRP plates were provided with a thin layer of surface epoxy matrix and featured enhanced sensitivity to surface preparation. Various degrees of morphological modification and fairly controllable carbon fiber exposure were obtained using sanding with emery paper and grit-blasting with glass particles. In the sanding process, different grit sizes of SiC paper were used, while the grit blasting treatment was carried by varying the sample-to-gun distance and the number of passes. Detailed surveys of surface topography and wettability were carried out using various methods, including scanning electron microscopy (SEM), contact profilometry, and wettability measurements. Mechanical tests were performed using double cantilever beam (DCB) adhesive joints. Two surface conditions were selected for the experiments: sanded interfaces mostly made of a polymer matrix and grit-blasted interfaces featuring a significant degree of exposed carbon fibers. Despite the different topographies, the selected surfaces displayed similar wettability. Besides, the adhesive joints with sanded interfaces had a smooth fracture response (steady-state crack growth). In contrast, the exposed fibers at grit-blasted interfaces enabled large-scale bridging and a significant R-curve behavior. While it is often predicated that quality composite joints require surfaces with a high percentage of the polymer matrix, our mechanical tests show that the exposure of carbon fibers can facilitate a remarkable toughening effect. These results open up for additional interesting prospects for future works concerning toughening of composite joints in automotive and aerospace applications.

Effect of mechanical pretreatment on nucleation and growth of HFCVD diamond films on cemented carbide tools with a complex shape

To enhance the mechanical pretreatment efficiency for WC-Co complex-shaped cutting tools, a self-made vibrating grinding equipment and mixed abrasives made up of walnut shell and diamond particles are proposed. The technique can abrade the dozens of tools simultaneously, modify surface properties of tools, and maintain sharpness of the cutting edges. Several experiments are performed to explore effects of the different types and proportions of walnut shell and diamond powders on the properties of nucleation, growth, and adhesion of diamond films deposited via a chemical vapor deposition method. Subsequently, Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM,), Laser scanning micro-gauge, Micro-Raman Spectroscopy, Stylus Profiler, and Rockwell hardness tester are adopted to characterize the as-pretreated substrates and as-deposited diamond films. According to the results, a low residual cobalt content around 0.2 wt% and a markedly increased surface defects are detected on the pretreated milling tools when the preferred types and proportions of mixed abrasives are applied, which can help to significantly enhance the nucleation density and growth rate of diamond films, and strengthen the adhesion between the films and substrates.

Effect of mechanical pretreatment on Nannochloropsis gaditana on the extraction of omega-3 by using accelerated solvent extraction technology

The omega-3 group includes substances as eicosapentaenoic acid and docosapentaenoic acid that can be partially synthesized by human body and substances as alpha-linolenic acid that have to be necessarily introduced into the body from dietary intake. Omega-3 are important nutrients thanks to their anti-inflammatory properties and healthy properties in the reduction of cardiovascular diseases. The growth forecasts of omega-3 market will lead to an increase in the demand for EPA and DHA and therefore finding new potential sources, such as microalgae which are the first EPA and DHA producers in the marine environment, is very important.The aim of this work is to evaluate the feasibility of mechanical pretreatment on Nannochloropsis gaditana as source of EPA and at the same time evaluating the effect on the extraction yield of two solvents: a mixture of chloroform/methanol/water (Bligh & Dyer methods) and hexane that is GRAS (generally recognized as safe solvent) by using accelerated solvent extraction technology.

The effect of mechanical pretreatment on the anaerobic digestion of Hybrid Pennisetum

This study investigated the effect of particle size on the performance of anaerobic digestion of Hybrid Pennisetum. Hybrid Pennisetum was ground and sieved to provide different particle sizes between 0.180 and 1.000 mm. Characterization of the different particle sizes suggested that the composition of ground Hybrid Pennisetum altered-carbohydrate content decreased and lignin content increased with a decrease in particle size. The highest specific methane yield was 291.9 ± 4.7 mL CH4·g−1 VS at a particle size of 0.250–0.380 mm and this value plateaued as the particle size was reduced to below 0.250 mm. Excessive size reduction did not improve the methane yield but did result in a reduction of digestion time by 28.6–35.7%. The net energy output from the process was calculated at 300 kWh/t VS. Therefore, grinding was proved to enhance the anaerobic fermentation efficiency and energy output of Hybrid Pennisetum.

Effects of mechanical pretreatments on enzymatic hydrolysis of mixed lignocellulosic substrates for biorefineries

The enzymatic hydrolysis of lignocellulosic biomass into fermentable sugars remains a critical challenge for producing bio-based products due to complexity and recalcitrance of the biomass. The effects of mechanical pretreatments (i.e., wet grinding for corncob residues and PFI refining for wood fibers) on the enzymatic hydrolysis of mixed substrates of corncob residues (CRs) and wood fibers (WFs) were investigated. The results showed that the applied combined mechanical pretreatments noticeably enhanced the enzymatic digestibility of the mixed substrates. A 99.8% conversion yield of cellulose to glucose and 19.2 g/L glucose concentration were obtained when the mixed substrates (composed of the refined WFs and the ground CRs) were enzymatically hydrolyzed for 46 h. The improvements, including swelling ability, specific surface area, and morphology, were mainly attributed to the combined mechanical pretreatments.

Supercritical Fluid Extraction of Lutein from Scenedesmus almeriensis.

Lutein has several benefits for human health, playing an important role in the prevention of age-related macular degeneration (AMD), cataracts, amelioration of the first stages of atherosclerosis, and some types of cancer. In this work, the Scenedesmus almeriensis microalga was used as a natural source for the supercritical fluid (SF) extraction of lutein. For this purpose, the optimization of the main parameters affecting the extraction, such as biomass pre-treatment, temperature, pressure, and carbon dioxide (CO2) flow rate, was performed. In the first stage, the effect of mechanical pre-treatment (diatomaceous earth (DE) and biomass mixing in the range 0.25–1 DE/biomass; grinding speed varying between 0 and 600 rpm, and pre-treatment time changing from 2.5 to 10 min), was evaluated on lutein extraction efficiency. In the second stage, the influence of SF-CO2 extraction parameters such as pressure (25–55 MPa), temperature (50 and 65 °C), and CO2 flow rate (7.24 and 14.48 g/min) on lutein recovery and purity was investigated. The results demonstrated that by increasing temperature, pressure, and CO2 flow rate lutein recovery and purity were improved. The maximum lutein recovery (~98%) with purity of ~34% was achieved operating at 65 °C and 55 MPa with a CO2 flow rate of 14.48 g/min. Therefore, optimum conditions could be useful in food industries for lutein supplementation in food products.

Eicosapentaenoic Acid Extraction from Nannochloropsis gaditana using Carbon Dioxide at Supercritical Conditions.

This research shows that carbon dioxide supercritical fluid (CO2-SF) is an emerging technology for the extraction of high interest compounds for applications in the manufacturing of pharmaceuticals, nutraceuticals, and cosmetics from microalgae. The purpose of this study is to recover fatty acids (FAs) and, more precisely, eicosapentaenoic acid (EPA) from Nannochloropsis gaditana biomass by CO2-SF extraction. In the paper, the effect of mechanical pre-treatment was evaluated with the aim of increasing FAs recovery. Extraction was performed at a pressure range of 250–550 bars and a CO2 flow rate of 7.24 and 14.48 g/min, while temperature was fixed at 50 or 65 °C. The effect of these parameters on the extraction yield was assessed at each extraction cycle, 20 min each, for a total extraction time of 100 min. Furthermore, the effect of biomass loading on EPA recovery was evaluated. The highest EPA extraction yield, i.e., 11.50 mg/g, corresponding to 27.4% EPA recovery, was obtained at 65 °C and 250 bars with a CO2 flow rate of 7.24 g/min and 1.0 g biomass loading. The increased CO2 flow rate from 7.24 to 14.48 g/min enhanced the cumulative EPA recovery at 250 bars. The purity of EPA could be improved by biomass loading of 2.01 g, even if recovery was reduced.

Extraction of Bioactive Compounds Using Supercritical Carbon Dioxide.

Microalgae Dunaliella salina contains useful molecules such as β-carotene and fatty acids (FAs), which are considered high value-added compounds. To extract these molecules, supercritical carbon dioxide was used at different operative conditions. The effects of mechanical pre-treatment (grinding speed at 0–600 rpm; pre-treatment time of 2.5–7.5 min) and operating parameters for extraction, such as biomass loading (2.45 and 7.53 g), pressure (100–550 bars), temperature (50–75 °C) and CO2 flow rate (7.24 and 14.48 g/min) by varying the extraction times (30–110 min) were evaluated. Results showed that the maximum cumulative recovery (25.48%) of β-carotene was achieved at 400 bars and 65 °C with a CO2 flow rate of 14.48 g/min, while the highest purity for stage (55.40%) was attained at 550 bars and 65 °C with a CO2 flow rate of 14.48 g/min. The maximum recovery of FAs, equal to 8.47 mg/g, was achieved at 550 bars and 75 °C with a CO2 flow rate of 14.48 g/min. Moreover, the lowest biomass loading (2.45 g) and the first extraction cycle (30 min) allowed the maximum extraction of β-carotene and FAs.

Production of Micro- and Nanofibrillated Cellulose through an Aqueous Counter Collision System Followed by Ultrasound: Effect of Mechanical Pretreatments

ABSTRACT The purpose of this work was the production of cellulose micro-nanofibrils from wood pulps through a combination of mechanical treatments, including a recently patented process, a so-called aqueous counter collision (ACC) method followed by ultrasound treatment. Previously to ACC process, the raw pulp materials had to be downscaled to micro-sized dimension, due to the limits of collision jets nozzle diameter. Therefore, the softwood and hardwood pulps were mechanically pre-treated with valley beater refining or dry ball milling. Optical microscopy, atomic force microscopy, X-ray diffraction, thermogravimetric analysis, and gravimetric yield were estimated, to evaluate the effect of mechanical pretreatments on the proposed integrated fibrillation process. The characterizations indicated that valley beater as mechanical pretreatment was found to be more efficient compared to ball milling, of producing cellulose micro-nanofibrils in compliance with the proposed experimental procedure.

Process performance and comparative metagenomic analysis during co-digestion of manure and lignocellulosic biomass for biogas production

Mechanical pretreatment is considered to be a fast and easily applicable method to prepare the biomass for anaerobic digestion. In the present study, the effect of mechanical pretreatment on lignocellulosic silages biodegradability was elucidated in batch reactors. Moreover, co-digestion of the silages with pig manure in continuously fed biogas reactors was examined. Metagenomic analysis for determining the microbial communities in the pig manure digestion system was performed by analysing unassembled shotgun genomic sequences. A comparative analysis allowed to identify the microbial species firmly attached to the digested grass particles and to distinguish them from the planktonic microbes floating in the liquid medium. It was shown that the methane yield of ensiled grass was significantly increased by 12.3% due to mechanical pretreatment in batch experiments. Similarly, the increment of the methane yield in the co-digestion system reached 6.4%. Regarding the metagenomic study, species similar to Coprothermobacter proteolyticus and to Clostridium thermocellum, known for high proteolytic and cellulolytic activity respectively, were found firmly attached to the solid fraction of digested feedstock. Results from liquid samples revealed clear differences in microbial community composition, mainly dominated by Proteobacteria. The archaeal community was found in higher relative abundance in the liquid fraction of co-digestion experiment compared to the solid fraction. Finally, an unclassified Alkaliphilus sp. was found in high relative abundance in all samples.

Effect of cavitational disintegration of surplus activated sludge on methane generation in the process of anaerobic conversion

The effect of mechanical pretreatment of surplus activated sludge from the wastewater treatment facilities of a plant producing chips (LLC “Frito Lay Manufacturing,” Kashira, Moscow oblast) in a cavitation disintegrator on methane generation in the process of anaerobic conversion is investigated. In laboratory conditions, cavitation disintegration pretreatment of the activated sludge results in a two- to sixfold increase in the transfer of various types of organic materials from the cell suspension into the aqueous phase. It is demonstrated that cavitation pretreatment of the activated sludge makes it possible to produce 31% extra methane as compared to the amount produced from the original sludge.

Biogas production from ensiled meadow grass; effect of mechanical pretreatments and rapid determination of substrate biodegradability via physicochemical methods

As the biogas sector is rapidly expanding, there is an increasing need in finding new alternative feedstock to biogas plants. Meadow grass can be a suitable co-substrate and if ensiled it can be supplied to biogas plants continuously throughout the year. Nevertheless, this substrate is quite recalcitrant and therefore efficient pretreatment is needed to permit easy access of microbes to the degradable components. In this study, different mechanical pretreatment methods were applied on ensiled meadow grass to investigate their effect on biomass biodegradability. All the tested pretreatments increased the methane productivity and the increase ranged from 8% to 25%. The best mechanical pretreatment was the usage of two coarse mesh grating plates. Additionally, simple analytical methods were conducted to investigate the possibility of rapidly determining the methane yield of meadow grass. Among the methods, electrical conductivity test showed the most promising calibration statistics (R2=0.68).

Effect of mechanical pre-treatments in the behaviour of nanostructured PVD-coated tools in turning

As a consequence of the lack of characterization of advanced physical vapour deposition (PVD) coatings in the scope of turning, a methodology is presented to evaluate the performance of nanostructured coated tools in the scope of difficult to machine materials turning in particular are austenitic stainless steels. A main aspect of this research is the evaluation of different mechanical pre-treatments before PVD coating in cutting tools. In a first stage, four advanced PVD coatings were analyzed prior to studying the effect of pre-treatments. This stage allowed to identify the nanostructured AlTiSiN coating, commercial denomination nACo, as the one with the best performance for turning austenitic stainless steel. Once the best coating is identified in a second stage, the influence of drag-grinding and microblasting mechanical substrate pre-treatments was analyzed with regard to the performance of coated tools. Several aspects were considered: geometric modification of cutting edge, coating adhesion, substrate roughness and machining performance. The performance of the mentioned coatings was evaluated through wear tests. The machined material was AISI 304L and machining operation was cylindrical turning. Each test started up using a new edge. Results showed that drag-grinding pre-treatment leads to improved coating adhesion and, therefore, in the performance of the tool. Therefore, combination of nACo coating with drag-grinding pre-treatment offers a good solution for difficult to machine metals.

Influence of the composite surface structure on the peel strength of metallized carbon fibre-reinforced epoxy

In this work, the effect of mechanical pre-treatment on the surface structure of carbon fibre-reinforced epoxy composites and on its peel strength of electroless/electroplated copper was investigated. Sandblasting with Al2O3 was used to pre-treat the composite surface. The parameters investigated were blasting time (3s, 6s and 9s) and nozzle distance to substrate (300mm and 500mm). A two-step metallization process was used for depositing copper coatings on the pre-treated composite surface. First, an eletroless plating process was used to deposit a thin layer on the surface. Second, an electroplating process was used to reinforce the thickness of the coating. Increased blasting intensity leads to a significant increase in surface roughness, which promotes mechanical anchoring effects of the coating. Scanning electron microscopy images and contact angle measurements confirm the results of the surface roughness. The adhesion of sandblasted composites, characterized by measuring the peel strength, is 10 times higher compared to untreated specimens. In addition to the mechanical anchoring mechanism the exposure of carbon fibres on the surface due to the blasting process promoted a stronger bonding to copper, due to the higher, electrical conductivity of the fibres in comparison to the matrix.

Effects of mechanical pre-treatment on the biogas yield from ley crop silage

Previous studies on substrates for biogas production have shown that different types of pre-treatments make the material more accessible for microbial degradation by breaking down the complex structure of the organic material, thereby increasing their potential for gas production. In this paper, two different mechanical pre-treatment apparatus, i.e. a Grubben deflaker (Gd) and a Krima disperser (Kd), were tested in a full scale setup to evaluate their effects on ley crop silage. The treatments were investigated with regard to their effects on particle size, methane potential, capacity and energy balance. The results after 115days of incubation in a batch assay show that methane production increased by 59% and 43% respectively after grinding with Gd and Kd. In both treatments, 90% of the ley crop was ground to particles of less than 2mm and more than 50% of the sample was reduced to particles smaller than 0.125mm. The energy balance was positive for Gd and around the break-even point for Kd. Analysis of the setup showed that Kd had almost twice the capacity of the Gd. If installed in the co-digestion biogas plant Växtkraft in Västerås, Sweden, the Gd and Kd could increase annual biogas yields by 790MWh and 585MWh respectively.

Effect of Mechanical Pretreatment on Gas Nitriding Behavior of Austenitic Stainless Steels

In order to develop a method of gas nitriding of austenitic stainless steels without chemical treatment such as pickling, three types of steels, SUS304, SUS316 and SUS310, were pretreated under various mechanical processes (as-cut with resinoid blade, polishing with emery papers, grinding with CBN wheel, and shot peening), followed by nitriding in NH3 gas with a flow rate of 2.8 m 3 /h at 843 K for 20 h. The influence of the mechanical pretreatment on nitriding behavior was examined in connection with two factors of surface roughness and strain-induced martensite. Nitriding reaction depends primarily on surface roughness in SUS310 and SUS316. This nitriding reaction is markedly enhanced with increasing surface roughness when its value exceeds 6 and 1 μm for SUS310 and SUS316, respectively, while no reaction is recognized for the surface roughness less than these values. In SUS304, martensitic transformation is readily induced by the mechanical pretreatment, and not only the surface roughness but also the strain-induced martensite contribute to nitriding behavior. It is confirmed from the present results that mechanical pretreatment enables the gas nitriding of austenitic stainless steels without pickling, when the surface roughness and the amount of strain-induced martensite are controlled properly.

Effects of mechanical pretreatment of precursor sols and gels on the formation of NiO/SiO2 composites with a controlled microstructure

Abstract The effects of ball-milling a sol, prepared from NiSi bidentate alkoxides, on the segregation of NiO from SiO 2 during subsequent heating are studied for the purpose of fabricating composites in which the nanosized microstructure is controlled. After dissolving a nylon substrate on which gel films were deposited, the films were heated to 500°C in air. Transmission electron micrographs of substrateless gel films showed that the agglomeration of NiO particles, formed in the films, decreased by ball-milling a sol. A similar phenomenon was also observed on ball-milling gel powders. The infrared absorption bands due to SiO asymmetric stretching vibration became broader by ball-milling. This broadening also occurred when NiO segregated from SiO 2 by heating a non-milled gel powder above 700°C. It is suggested that ball-milling produced a more homogeneously distributed nucleation of NiO particles through the breakage of bonds between O 2− and Ni 2+ incorporated into SiO 2 networks.