Effect Of Microwave Pretreatment Research Articles

Effect of microwave pretreatment on grinding and flotation kinetics of copper complex ore

Effect of microwave pretreatment on grinding and flotation kinetics of copper complex ore

Effect of Microwave Pretreatment on Leaching of Tetrahedrite

In mineral processing, the use of microwave radiation is important especially in pre-treatment processes. At present, there is an acceleration of processes as well as an increase in the efficiency of metal recovery. One of the main problems in copper recovery from complex sulphide ores is the removal of impurities such as antimony, arsenic, mercury. In the hydrometallurgical processing scheme, the key step is the leaching. The extraction process can be influenced by the selection of suitable leaching reagents or by suitable pre-treatment of the ore. The article describes the effect of microwave radiation on the leaching Sb, As and Hg of tetrahedrite and tetrahedrite concentrate. The samples were irradiated at the power 900 W for 30 seconds. The leaching of irradiated and non-irradiated samples was realized in an alkaline sodium sulphide. The positive effect of microwave radiation was confirmed by an increase in the recovery of Sb and As already after 15 min of extraction. After microwave leaching of irradiated tetrahedrite samples, the yield of Sb was 43.2 %, in irradiated tetrahedrite concentrate, the yield of Sb was 81.3 %.

Effect of Microwave Pretreatment on Grindability of Lead-Zinc Ore

The influence of microwave pretreatment on grindability of lead-zinc ore was studied through comparison analysis on the changes of particle size distribution, percentage of below 0.074 mm, energy consumption, and other indexes of grinding products before and after microwave pretreatment in the ball milling process. The results showed that the grindability of lead-zinc ore was improved obviously by microwave pretreatment. The particle size distribution curve of the grinding products was obviously higher than that of the samples without microwave irradiation. The yield of size fraction below 0.074 mm was also improved in a certain degree. Pulsed microwave irradiation was more effective than continuous microwave irradiation when other microwave parameters were consistent. The comprehensive energy consumption of lead-zinc ore pretreated by different microwave parameters was lower than that without microwave irradiation under the same grinding fineness. The total energy consumption was down by 30.1% when irradiated for 15 s at 7 kW power, and it was lower than that without microwave irradiated. The results showed that pulsed microwave pretreatment was more effective in reducing the comprehensive energy consumption of grinding process for lead-zinc ore. And water quenching after microwave irradiation can improve the grindability and reduce the energy consumption of grinding for lead-zinc ore.

Effect of microwave pre-treatment on physical quality, bioactive compounds, safety risk factor, and storage stability of peanut butter

Microwave, as a new heat treatment technology, has the characteristics of uniform and fast heating speed. It is an energy-saving technology known for improving oilseed product quality. Its efficiency mainly depends on the roasting power and time. However, the production of high-quality peanut butter using short-time roasting conditions are limited. Herein, we determined an appropriate microwave roasting power and time for peanuts and evaluated its impacts on the quality of peanut butter. Different roasting powers (400 ​W, 800 ​W and 1200 ​W) and times (4, 4.5, 5, and 5.5 ​min) were preliminarily tested. Among them, 800 ​W at 5 ​min was the most suitable. The roasting efficiency was further evaluated using color, sensory, bioactive compounds, storage stability, and safety risk factors of peanut butter produced from four peanut cultivars (Silihong, Baisha-1016, Yuanza-9102, and Yuhua-9414). The pre-treated butter obtained from three cultivars (Silihong, Yuanza-9102, and Yuhua-9414) with moisture content between 5% and 7.2% had a similar sensory score (6–7) as the commercial on a 9-point hedonic scale compare to the other. The color of the pre-treated peanut butter varies statistically with the commercial but remained in the recommended range of Hunter L∗ values of 51–52, respectively, for high initial moisture peanut cultivars. The total polyphenol (35.20-31.59 ​± ​0.59 ​μmol GAE/g) and tocopherol (19.05 ​± ​0.35 ​mg/100 ​g) content in the butter obtained from three cultivars (Yuahua-9102, Yuhua, and Baisha-1016) and Silihong respectively, were significantly (P ​< ​0.05) higher than those in the commercial butter. The induction times of all pre-treated butter (19.80 ​± ​0.99–7.84 ​± ​0.07 ​h) were significantly (P ​< ​0.05) longer during storage at accelerated temperature than commercial samples. In addition, no benzo[a]pyrene was found in the pre-treated samples. Collectively, the microwave pretreated peanut butter was superior to the commercial one. These findings provided data support and a reference basis to promote microwave use for peanut butter production.

Effect of microwave pretreatment on the exchange energy of forage barley

AbstractThe effect of microwave pretreatment on the exchange energy of forage barley was studied using the developed experimental setup. The novelty of the developed experimental setup in the summation of the power of microwave magnetrons in the waveguide, which provides an increase in productivity up to 50 kg/h while reducing energy consumption to 0.04 kW h/kg. The hypothesis of summation of the power of microwave magnetrons has been confirmed using a computer model in CST Studio. The average combined power of two magnetrons is 13 V A/m2. Using the method of planning the full factorial experiment, experimental studies of microwave pretreatment of forage barley of the second class with an exchange energy of 12 MJ/kg were carried out. Optimized significant factors affecting the pretreatment, such as grain moisture 16.5%, device power level 2, and the height of the waveguide end relative to the grain layer 41.7 mm. With these experimental parameters, the level of the exchange energy of forage barley will be 13.1 MJ/kg, which corresponds to forage barley of the first class. Microwave pretreatment of grain by increasing the exchange energy can increase the nutritional value of grain.Practical applicationsIncreasing the exchange energy and nutritional value of forage barley will increase its digestibility by animals. It is proposed to use the developed microwave setup in agricultural farms to reduce energy consumption for grain pretreatment before feeding animals.

Effect of microwave pre-treatment and frying conditions on acrylamide formation and oil uptake in fried carrot pieces

Effect of microwave pre-treatment and frying conditions on acrylamide formation and oil uptake in fried carrot pieces

Quantitative evaluation of microwave irradiation on short-rotation plantation wood species

The durability of imported timber is a matter of growing concern in the tropical Indian climate, with their refractory nature further adding to the woes with respect to further processing. In the present study, the effect of microwave pre-treatment, exposure time and initial wood moisture content on retention, treatability and cross-sectional anatomical properties of Tectona grandis and Southern yellow pine imported from Ghana and South America were evaluated. Water based preservative copper chrome borate (CCB) of 2 % concentration was used for the study. The experimental study in combination with dip-diffusion method returned with significant improvement in retention of about 5-6 folds more than the control sets in Southern yellow pine and Tectona grandis. Another set of Southern yellow pine and Tectona grandis samples were further treated using a full cell pressure method after microwave, without initial vacuum, which showed similar trends with 3-4 folds increase in retention over controls. Both experiments returned with significant improvement in the treatability class of Tectona grandis and Southern yellow pine. Anatomical analysis was performed using a light microscope with 5 and 10x magnifications on treated and untreated samples of both Tectona grandis and Southern yellow pine. The outcome of the anatomical study exhibited improvement in vessel diameters in the treated samples of Tectona grandis with reduction in the degree of occlusion by presence of tyloses. For Southern yellow pine, checks on micro level and cracks on macro level appeared along the ray cells and the diameter of the resin canals were substantially expanded which ascertains that microwave pre-treatment ameliorated the flow of fluids in the wood microstructure which improved permeability and resulted in better uptake and penetration

Effects of microwave pretreatment on drying of 50\xa0mm-thickness Chinese fir lumber

Low permeability of wood causes problems during drying of timber. This study evaluated the effects of microwave (MW) pretreatment on the conventional drying behavior and mechanical damages of Chinese fir lumber. MW pretreatment of lumber was performed at applied MW energy of 43 kWh/m3, and then, the samples were dried in a laboratory drying kiln. The results showed that the drying rate was effectively increased after MW pretreatment. The moisture content (MC) deviation in thickness and residual stress indexes of MW-pretreated samples were significantly decreased in comparison with the control samples, and the appearance quality of wood samples was not clearly affected by the MW pretreatment. Scanning electron microscope (SEM) micrographs demonstrated that pit membranes were damaged after MW pretreatment, and the micro-cracks in radial section as well as detachments between ray parenchyma cells and tracheids were also observed. Consequently, new pathways for moisture migration during drying process were formed after MW pretreatment, which contributed to the improved permeability of Chinese fir lumber and decreased drying time.

The effect of microwave pretreatment on impact crushing of lead-zinc ore

The relationship between energy input and particle size of ore samples after crushing and effect of microwave pretreatment on impact crushing of lead-zinc ore were studied by drop weight impact test. The results showed that the lead-zinc ore became softer and had higher degree of crushing after microwave pretreatment. Compared with continuous microwave pretreatment, pulsed microwave pretreatment could improve the drop weight impact crushing efficiency of lead-zinc ore. When the specific comminution energy were 5 kW h/t, 10 kW h/t respectively, the crushing characteristic parameters t10 were 60.42% and 67.46% respectively by continuous microwave. But the values of t10 were increased to 68.64% and 75.88% respectively after pulsed microwave radiation under same microwave power and time. In addition, water quenching could more promote the impact crushing efficiency of lead-zinc ore after microwave irradiation.

Effect of Microwave Pretreatment on Pyrolysis of Chili Straw: Thermodynamics, Activation Energy, and Solid Reaction Mechanism

Effect of Microwave Pretreatment on Pyrolysis of Chili Straw: Thermodynamics, Activation Energy, and Solid Reaction Mechanism

Effect of Microwave Pretreatment on Production of Reducing Sugar from Oil Palm Empty Fruit Bunches

ABSTRAK&#x0D; Perlakuan pendahulan biomassa merupakan tahapan terpenting dalam memproduksi produk-produk berbasis bio (bio-based products) secara biologis. Pada penelitian ini, energi gelombang mikro (microwave) digunakan selama perlakuan pendahuluan untuk meningkatkan kinerja proses sakarifikasi tandan kosong kelapa sawit (TKKS) menjadi gula-gula pereduksi. Faktor-faktor yang mempengaruhi perlakuan pendahuluan seperti daya (180-360 watt), waktu iradiasi (5-30 menit), dan solid loading (2,5%-7,5%) dievaluasi. Kinerja hidrolisis TKKS yang telah diberi perlakuan pendahuluan selanjutnya dianalisis dengan Cellic CTec2. Hasil penelitian menunjukkan bahwa cairan residu yang diperoleh setelah perlakuan pendahuluan menghasilkan gula pereduksi dalam jumlah yang rendah, yaitu antara 1,39 dan 3,92 mg/g-TKKS. Akan tetapi, setelah padatan residu dihidrolisis secara enzimatis, rendemen gula pereduksi meningkat secara signifikan. Menariknya, hanya pada level daya terendah (180 watt), gula pereduksi meningkat seiring dengan perpanjangan waktu iradiasi untuk semua solid loading. Sebaliknya, pada 360 watt, semakin lama waktu iradiasi diterapkan, semakin rendah gula pereduksi yang diperoleh untuk semua solid loading. Gula pereduksi tertinggi dihasilkan hingga 151 mg/g-TKKS, yaitu menggunakan 5% padatan pada 180 watt selama 25 menit. Berdasarkan hasil-hasil ini, perlakuan pendahuluan menggunakan gelombang mikro yang diikuti dengan hidrolisis enzimatis merupakan salah satu metode yang potensial untuk memproduksi gula dari TKKS.&#x0D; &#x0D; Pretreatment of biomass is the most crucial step in the biological production of bio-based products. In this study, microwave energy was used during the pretreatment process to enhance the saccharification performance of oil palm empty fruit bunches (OPEFB) into reducing sugar. The influential factors of pretreatment such as power level (180-360 watt), irradiation time (5-30 min), and solid loading (2.5%-7.5%) were evaluated. The performance of pretreated OPEFB hydrolysis was subsequently assessed by Cellic CTec2. The result showed that spent liquor produced after pretreatment only released a low amount of reducing sugar in the range between 1.39 and 3.92 mg/g-OPEFB. After residual solid was enzymatically hydrolyzed, a significant increase in the reducing sugar yield occurred. Interestingly, only at the lowest power level (180 watts), the reducing sugar rose along with the extension of irradiation time for all solid loadings. On the contrary, the longer irradiation time was applied, the lower reducing sugar was acquired at 360 watts for all solid loadings. The highest reducing sugar was produced up to 151 mg/g-OPEFB using 5% solid at 180 watts for 25 min. This indicated that microwave pretreatment followed by enzymatic hydrolysis was one of the potential methods to recover sugars in OPEFB.

The effect of microwave pretreatment on anaerobic co-digestion of sludge and food waste: Performance, kinetics and energy recovery

This paper studied the effect of microwave (MW) pretreatment on anaerobic co-digestion of sludge (SS) and food waste (FW). Using SS and FW as digestive substrates, the MW pretreatment method was used to determine the changes in the substrate matrix by means of batch anaerobic digestion at 37 °C. The kinetics of methane production were calculated, and the changes in organic matter during anaerobic co-digestion, the properties of the anaerobic-digested effluent, and the net energy output of the co-digestion system were determinated. The results showed that MW pretreatment was beneficial to the dissolution of organic matter, conversion of protein to NH4+-N, cumulative methane production, unit biomethane yield, and reaction rate of methane production in the SS and FW anaerobic co-digestion system. The highest cumulative methane production in the co-digestion system reached 3446.3 ± 172.3 mL (35 days), which was 19.93% higher than that of the control. Furthermore, MW pretreatment significantly increased the accumulation of VFAs and the content of butyric acid in the anaerobic-digested effluent, which was beneficial to the methanogenesis process. The MW pretreatment of all co-digested substrates produced a greater net energy output than the control, and the MW-SS + MW-FW group yielded the highest net energy output, which was 76.25 kJ/g Fed VS. The results indicated that MW pretreatment prior to SS and FW anaerobic co-digestion is an effective way to improve the anaerobic digestion efficiency and energy recovery rate.

Effects of microwave pre-treatment on the flotation of ilmenite and titanaugite

The selective separation of titanium-containing minerals is industrially important. Microwave irradiation pre-treatment can be used to modify the surface properties of minerals to promote selective flotation. However, the effects of MW treatment on titanium-containing minerals is not well understood. Therefore, in this study, we investigated the effects of microwave treatment on the flotation behaviour of ilmenite and titanaugite in a mixture of these minerals. The effects of this pre-treatment method were investigated by various techniques, including flotation tests, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), zeta potential measurements, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy. The flotation tests results reveal that, under the optimum microwave conditions (800 W, 450 s), microwave irradiation has a remarkable effect on the flotation of ilmenite but no significant effect on the floatability of titanaugite at pH 6.0. The results of the SEM and ICP-OES analyses indicate that microwave irradiation promotes the dissolution of Ca2+ and Mg2+ ions from the titanaugite surface, whereas the dissolution of these ions from ilmenite is limited. Further, the zeta potential of the microwave-irradiated ilmenite shifted toward negative values, and the isoelectric point shifted from pH 4.9 to pH ~1.9. In addition, the XPS results reveal that microwave irradiation facilitates the conversion of Fe2+ to Fe3+ on the mineral surfaces. The FTIR spectra and zeta potential values indicate that microwave irradiation can enhance the chemical adsorption of oleate ions on the surface of the ilmenite. After microwave irradiation, the effects of both the dissolution of Ca2+ and Mg2+ ions and the oxidation of Fe2+ to Fe3+, the floatability of ilmenite was significantly improved, whereas that of titanaugite was not changed significantly.

Microwave pretreated enzymatic retting of flax stems and comparison with the effect of radio frequency pretreatment

Microwave (MW) together with prior water presoaking was used as a pretreatment for enzymatic retting of flax stems in this work. Weight loss, pectin removal, the resulting fibers’ properties and the degree of water absorption of the stems after MW pretreatment were measured and analyzed. The effect of MW pretreatment on enzymatic retting was determined and compared with the radio frequency (RF) pretreatment which adopted the same processing parameters. It was found that the 8 h-30 min MW pretreatment improved the enzymatic retting efficiency most, increasing weight loss by 39 %, decreasing pectin content by 10.96 % compared to the control enzymatic retting and obtaining water sorption of 2.23, and produced fibers with reasonable tensile performance. Compared with RF pretreatment, MW pretreatment enabled flax to absorb more water and more energy then got more improvement in the retting efficiency. And the 30 min-MW treatment could improve pectin removal for the non-presoaked flax as compared to the control enzymatic retting, which was different from RF treatment. The enzyme-retted fibers with the same MW and RF pretreatments had close tensile properties, however, their values of the MW-pretreated fibers tended to be slightly lower. It was also found that the tensile performance of the pretreated, enzyme-retted fibers was linked to the amount of energy absorbed, the temperature-maintaining time proportion during MW or RF treatment, and whether the flax had been presoaked or not.

Enhancing laccase‐induced soybean protein isolates gel properties by microwave pretreatment

Soybean protein isolate (SPI) is an important food ingredient used to prepare for soy products. However, protein gel formed from individual SPI exhibits poor gelation properties. In this study, effects of microwave pretreatment at various power (0–600 W) on gel properties of laccase-induced gel were investigated. After microwave pretreating, gel strength of treated samples was over 2.2 times that of untreated. Microwave heating dramatically promoted water-holding capacity and storage modulus of laccase-induced SPI gel. Marked reducing happened in free SH group, since laccase catalyzed cross-linking between phenols and its derivatives, which facilitated the connection of disulfide bonds. In addition, microwave pretreatment changed the secondary structure of the gel samples as determined by Fourier transform infrared spectroscopic analysis. Intuitively, a more compact structure was observed by SEM. Hence, microwave pretreatment is effective in improving the gelation properties of laccase-induced SPI gel and may be used as an effective method in food industry. Practical applications As an indispensable ingredient, Soybean protein isolate (SPI) was wildly used in food industry to produce kinds of soy products. However, its poor gel properties impeded a further application of this low-cost ingredient. In this study, SPI was pretreated by microwave which destroyed its compact structure and exposed the reactive sites of enzyme. Then, microwave pretreatment SPI was induced by laccase to catalyze cross-linking between phenols and its derivatives since the groups were common exist in SPI. The laccase-induced SPI gel couple with microwave pretreatment possessed a more excellent gel property, which can be potentially used to produce high-quality soy products in food industry.

Development of several hybrid drying methods used to obtain red beetroot powder

Reduction of bioactive compounds sensitive to heat, light and oxygen could be attributed to drying. The effectiveness of microwave pretreatment at 525 or 420 W and the ohmic heating at 17.5 V/cm over the properties of beetroot powder were compared. This study aimed to develop novel hybrid drying methods. The effects of microwave and ohmic heating pre-treatment and subsequent microwave-convection drying were studied. Several investigations were performed, such as phenolic content, antioxidant activity, betalains content and color.The samples pretreated by microwave have registered higher polyphenols content and antioxidant capacity than those ohmically heated. The ohmic heating pretreated samples registered highest values for ΔL = 7.33–7.65 and ΔH = 8.18–10.02. Confocal microscopy reveals that the MW heating favors cellular lysis and cell content agglutinates. In conclusion, even if the MW preheating has certain disadvantages, in some cases it provides increased bioavailability generated by the vegetal cell disruption and the release of the bioactive compounds.

Effect of microwave pre-treatment on preservative retention and treatability of Melia composita wood

The species Melia composita has come to prominence only during the last decade and has been found suitable for several applications and end uses. However, being non-durable and difficult to treat some pre-treatment is required to improve preservative uptake. Hence the effect of microwave (MW) pre-treatment was studied on the samples of Melia composita wood in order to ameliorate its retention, depth of penetration and treatability class to ensure its sustainable use for a longer duration. The samples were exposed to MW radiation of different intensities and treated with 6% solutions of CCA, ZiBOC, CCB and Borax boric acid (BBA) preservatives by a dip diffusion method for 24 hours. Results showed a significant improvement in preservative uptake after dipping for 24 hours, in comparison with the controls. The highest retention was found in the samples treated with ZiBOC preservative after their MW exposure to 840 MJ·m–3. Wood anatomical analysis after MW modification was also performed in order to assess the changes taking place within the wood microstructure. The cross-sectional analyses of the controls and the treated specimens were briefed accordingly. Results of the anatomical study exhibited a significant improvement in the effective vessel diameters of the microwave irradiated specimens due to the clearance of the occlusions blocking the vessels with respect to the control samples, which aids in increasing wood permeability and results in higher retention and penetration.

Effects of microwave pretreatment on catalytic fast pyrolysis of pine sawdust

In this work, thermal behavior and pyrolysis products of pine sawdust after treated by different microwave pretreatment condition had been studied. Surface structure of samples getting collapsed after microwave pretreatment and the characteristics of thermal decomposition with CaO addition under four kinds heating rates was investigated by thermogravimetric analyzer. Pyrolysis process was carried and the products composition were detected both on Pyrolysis-Gas Chromatography/Mass Spectrometry. Under the condition of 567 W power treatments for 3 min, the yield of phenols rose from 3.64% to 18.21% and the ketones decreased from 55.80% to 40.27%. The activation energy was calculated by Flynn-Wall-Ozawa method. After microwave pretreatment, the activation energy of pine sawdust reach the maximum increase 7.26% at 329 W for 3 min, which meant that microwave pretreatment had little positive effect on promoting the pyrolysis reaction.

Effect of microwave pre-treatment on quality parameters in Indian mustard.

Demand for edible oil from crops like groundnut, mustard and soybean, is increasing and likely to increase further. In this regard, Indian mustard seeds were treated with microwaves (MW), to investigate the possibility of enhancing oil yield and nutritional content. MW pre-treatment was given to the seeds of two Indian mustard varieties i.e. PM21 (V1) and PDZ1 (V2) for 0, 2, 4 and 6min (H0, H2, H4 and H6 min respectively). MW treatment with increasing exposure time showed a linear reduction in the glucosinolate and erucic acid content with concomitant increase in oil yield and moisture loss in both the varieties, as evident from correlation and principal component analysis. Antioxidant capacity has increased with the reduction in phytic acid content (1.82) in V2 at 6min exposure time with respect to untreated control. Free radical scavenging activity was improved with increasing MW treatment in both the varieties. Therefore, from the obtained results, it is advisable to treat mustard seeds with MW before extraction of oil, because it gives a relatively good oil yield, with enhanced nutritional factors. Moreover, microwaving was effective in reducing glucosinolates and erucic acid also.

Effect of microwave pretreatment on centrifuged and floated sewage sludge derived from wastewater treatment plants

As a result of the growing number of wastewater treatment plants (WWTP), increasing quantities of sewage sludge are being produced. Biological treatments are usually the most frequent method used to treat this type of waste. However, due its poor biodegradability, a previous treatment is required to enhance this sludge. In this study, the application of a microwave pretreatment was evaluated at different power ratings (400 and 700W) for a specific applied energy ranging from 0 to 30,000J/g TS. The pretreatment was applied to floated sludge and centrifuged sludge from a WWTP. The effect of the variables power and specific energy differed depending on the type of sludge. Organic matter solubilization was evaluated in both sludges based on the CODs/TVS ratio (soluble chemical oxygen demand/total volatile solids). The results showed a 43% and 66% increase in solubility for the floated sludge at 400 and 700W, respectively, and a 162% and 187% increase for the centrifuged sludge at 700 and 400W, respectively. The increase in organic and nitrogenous matter during pretreatment had a positive effect on the aerobic biodegradability of the floated sludge and biodegradation kinetics, as the specific oxygen uptake rate (SOUR) increased up to 8.5 times for a specific energy of 15,000J/g TS. Independently of the moisture content, the floated sludge showed the best results above 10,000J/g TS. No significant differences were observed between the applied powers in terms of organic matter solubilization.