Sonication Pretreatment Research Articles

Natural bioink of interpenetrating network hydrogels mimicking extracellular polymeric substances for microbial immobilization in water pollution control

Artificial biomanufacturing has been developed as a promising biotechnology for water pollution control. Effective bioimmobilization techniques are limited in application because of low productivity and the difficulty in achieving both mechanical strength and biocompatibility. Bioprinting technology, using biomaterials as bioink to enable the rapid on-demand production of bioactive structures, opens a new path for bioimmobilization. In this study, mimicking extracellular polysaccharide and protein of aerobic granular sludge (AGS), sodium alginate (SA) and silk fibroin methacryloyl (SilMA) were developed as the dual-component bioink with a suitable viscosity for bioprinting hydrogel. Interpenetrating network (IPN) hydrogel beads were manufactured using 1.5% (w/v) SA combined with 20% (w/v) SilMA through physical and covalent crosslinking, which exhibited excellent structural stability and bioactivity. The addition of SilMA provided a solution to the poor mechanical stability of SA-Ca hydrogels limited by Ca2+-Na+ ionic exchange. The unique structure of SilMA contributed to the reduction of hydrogel swelling as well as the prevention of SA loss. IPN hydrogels showed a swelling rate of less than 20% compared to the high swelling rate of more than 60% for SA hydrogels. On the other hand, SA controlled the hardening induced by excessive self-assembly of SilMA and improved mass transport in SilMA hydrogels. Compared to IPN hydrogels, SilMA hydrogels experienced a 15% volumetric shrinkage and exhibited a low water content of 92%. Sonication pretreatment of the dual-component bioink not only increased the intermolecular chain entanglement to form IPN, but also led to β-sheet content in SiMA reaching 46%–48%, which resulted in the formation of stable IPN hydrogels dominated entirely by physical crosslinking. Satisfactory proliferation and viability were achieved for the encapsulated bacteria in IPN hydrogels (μmax 1.49–2.18 d−1). Further, the IPN biohydrogels could maintain structural stability as well as achieve pollutant removal for treating synthetic wastewater with high Na+ concentration of 300 mg/L. The novel SA/SilMA hydrogel bioprinting strategy established in this study offers a new direction for bioimmobilization in water pollution control and other environmental applications.

Biomethanisation of sewage sludge: Sonication pretreatment and monitoring of microbial communities

The improvement of mesophilic biomethanisation of recalcitrant sewage sludge derived from urban wastewater treatment through the application of a sonication pretreatment was evaluated in parallel in two pilot-scale anaerobic digesters (two biological replicates: reactors RA and RB). The valorisation process was monitored through a novel and holistic approach that related the biomethanisation yield, and its main batch operational parameters, with the abundance of archaeal and bacterial communities in the anaerobic inocula. Sonication allowed achieving a methane yield coefficient derived from sewage sludge of 240 ± 20 mLSTPCH4/g VS (volatile solids) at the load range of 0.8–4.0 g VS/L in both reactors. The process was more stable in reactor B, with a wider range of loads being allowed (up to 5.29 g VS/L). Monitoring the presence of Archaea in the mixing liquor revealed a variation in their abundance throughout the process which was directly related to the availability of organic matter and pH. Advanced metagenomic analysis showed the phylogenetic and functional diversity of the complex microbiome involved. While Bacteria were widely distributed in 35 phyla, Archaea fitted in only two. Euryarchaeota was the majoritarian archaeal phylum (99.5 %) and its more abundant families are linked to methanogenic metabolism. Functional analysis revealed several relevant metabolic pathways that followed similar trends in both reactors. “Methane metabolism” clearly diminished at the end of the process in concordance with the exhaust of methane generation, while “ABC transporters” or “two-component systems”, involved in bacterial survival to changing environments, followed the opposite pattern. This integrated approach could help to increase the methanogenic valorisation of sewage sludge.

Separation of oil–water emulsions by electrocoagulation and electro-persulfate with sonication pretreatment: Determination of economical electrode configuration, optimization, and comparison

This study aimed to separate oil–water emulsions by electrocoagulation (EC), which is considered an effective and promising method for sustainable water management, and the electro-persulfate method (EPS) as an advanced EC process. Firstly, oil–water emulsions were treated with EC using three different electrode configurations and the most economical electrode pair (perforated and plate electrodes) was determined. Secondly, the Box-Behnken design (BBD) was applied to explore the influence of operational variables (pH, current density, and electrolysis time for EC; pH, current density, PS/COD, and electrolysis time for EPS) on the removal of COD (5800 mg/L) as a response with the identified electrodes. As a result, at neutral pH, the optimal operating conditions determined for maximum COD removal were 27 mA/cm2 and 37 min for EC and 27 mA/cm2, 25 min, and PS/COD = 0.5 for EPS. At the predicted optimal conditions, the predicted and tested COD removal was respectively 100 % and 97.15 % for EC, 88.18 % and 87.94 % for EPS. Moreover, the total cost was 2.39 $/m3 and 1.27 $/m3 for EC and EPS, respectively. Consequently, it was determined that perforated electrodes were more economical, and EC achieved higher wastewater treatment performance than EPS, however, from an economic point of view, the EPS process enabled the more efficient treatment of oil–water emulsions.

Influence of sonication pretreatment on antiradical and anti-ACE activity of protein hydrolysates from fermented pork loins

The aim of this study was to assess whether ultrasound treatment (sonification time: 5, 15, and 30 min; constants: ∼40 kHz, ∼2.5 W cm2) can be applied prior to hydrolysis to enhance the anti-radical and angiotensin converting enzyme inhibiting (anti-ACE) effect of the hydrolysates from fermented pork loins. Enzymatic hydrolysis was performed using pepsin, followed by pancreatin. The influence of meat matrix on the course of hydrolysis, shaped using a lactic acid bacteria (LAB)-based starter culture, was also analyzed. It was found that proteases caused a systematic increase in the content of peptides, while pancreatin limited the peptide content in the protein hydrolysate from the loins subjected to spontaneous fermentation. Moreover, for these tests, sonication time had a negligible effect on the peptides content of the hydrolysates. On the other hand, for the sample of LAB-fermented products, both sonication time and stage of hydrolysis promoted the biological activity of the hydrolysates. Samples from the LAB-fermented meat had more peptides at the stage of digestion with pepsin and pancreatin, exhibiting much faster antiradical and anti-ACE activity compared to the control sample. The obtained results suggest that the use of LAB promotes the release of antiradical peptides during the two-step enzymatic hydrolysis, the duration of which can be shortened to achieve satisfactory biofunctionalities. Additional application of sonication pretreatment allows controlling the course of the hydrolysis, as the pro-health, biological effect of some protein-derived sequences is associated with the content of peptides.

Robust pretreatment in combination with ultrasound-assisted surfactant to improve the enzymatic hydrolysis of Eucalyptus pellita

Alkaline pretreatment stands out as a valuable strategy in biomass conversion to overcome the recalcitrance of biomass by removing lignin and a part of hemicellulose. This enhances enzyme accessibility and promotes saccharification. However, increasing the alkaline concentration to enhance the delignification and improve glucose yield together presents inherent limitations. In this experiment the amount of delignification and glucose yield resulting from surfactant associated with sonication during mild alkaline pretreatment of Eucalyptus pellita was investigated. Also, the effect of various factors (sonication temperature and surfactant immersion time) on delignification and glucose yield were examined. The results demonstrated that surfactant associated with sonication pretreatment could overcome the limitation of alkaline pretreatment and could increase the amount of delignification alongside enzymatic hydrolysis glucose yield of Eucalyptus pellita wood by around 90%. The findings indicated that surfactant-assisted with sonication during mild alkaline pretreatment of Eucalyptus pellita (i.e., hardwood) could be recommended as a supporting pretreatment method for the production of monomeric sugars.

Innovative ultrasound sonication pretreatment sparger-based microwave assisted extraction method for enhanced essential oil extraction from lemon grass

This study introduces an innovative approach, Ultrasonic Sonication Pretreatment Sparger-based Microwave Assisted Extraction (U Sp-MAE), designed to enhance lemongrass essential oil extraction. Addressing the challenge of maximizing yield and quality, our work systematically optimized key extraction parameters. Results demonstrated a significant improvement over conventional methods, with the highest yield of 1.89% achieved under specific conditions: a Sparger Flow rate of 4 L/min, Ultrasound Power of 700 W, Sonication Time of 5 min, and Liquid-to-Solid Ratio of 5 mL/g. This method not only advances essential oil extraction but holds promise for broader applications in society, showcasing its potential impact on sustainable and efficient resource utilization.

Plant based surfactant combined sonication pretreatment on food waste for biomethane generation: Cost and energy procurement

Food waste (FW) can be used as an appropriate feedstock for bioenergy generation. However, the rate limiting hydrolysis step during Anaerobic Digestion (AD) limits the biodegradation of substrate. Hence, pretreatment of food waste is essential prior to AD to circumvent the rate limiting step. Ultrasonic pretreatment of FW has been restricted owing to its greater energy requirement, aggregation of FW particles and lignin binding to methanogenic enzymes during biomethanation process. These limitations could reduce the efficiency of the whole treatment. In this study an effort has been made to enhance the hydrolysis and to improve the methanogenesis by pretreating the FW with plant-based surfactant (saponin) coupled ultrasonic pretreatment. The ultrasonic alone (US alone) pretreatment experimental run was done by varying the ultrasonic power from 80 to 180 Watt and pretreatment time from 0 to 20 min. The ultrasonic combined saponin (US-saponin) pretreatment experimental run was done by varying the time from 0 to 10 min and saponin dosage from 0.0005 to 0.008 g/g TS. The outcome reveals that the specific energy input of 5052 kJ/kg TS, saponin concentration of 0.002 g/g SS, and 2 min pretreatment time was optimum to achieve the maximum solubilization of 37 % in US- saponin sample. The US alone demands a specific energy input of 25263 kJ/kg TS and a pretreatment time 10 min to achieve the maximum solubilization of 30.5 %. The US-saponin pretreatment shows 269 mL/gCOD of methane production, higher than the US alone (148 mL/gCOD) and control (53 mL/gCOD). Regarding energy and cost assessment, the US- saponin pretreatment shows 12.07 USD/ton of net profit, greater than the US alone pretreatment (−260.8 USD/ton).

Advances in the Separation of Graphite from Lithium Iron Phosphate from End-of-Life Batteries Shredded Fine Fraction Using Simple Froth Flotation

Olivine-type lithium iron phosphate (LiFePO4, LFP) lithium-ion batteries (LIBs) have become a popular choice for electric vehicles (EVs) and stationary energy storage systems. In the context of recycling, this study addresses the complex challenge of separating black mass of spent LFP batteries from its main composing materials to allow for direct recycling. In this study, 71% copper and 81% aluminium foil impurities were removed by sieving black mass to <250 µm. Next, the application of froth flotation as a separation technique was explored, examining the influence of chemical agents, pre-treatment, and multi-step processes. Frother agent addition improved material recovery in the froth, while collector addition influenced the separation efficiency and enhanced graphite recovery. Pre-treatment, particularly sonication, was found to break down agglomerates and further improve separation. Multi-step flotation increased the purity of recovered fractions. The optimized process for a black mass < 250 µm, involving sonication pre-treatment and double flotation, resulted in enriched carbonaceous material (80.3 mol%) in froth fractions and high LFP concentration (81.9 mol%) in tailings fractions. The recovered spent LFP cathode material contained 37.20 wt% Fe2P2O7, a degradation product of LiFePO4. This research offers valuable insights for the development of efficient battery recycling methods for LFP batteries.

Methane production enhancement from Tetraselmis biomass co-digestion using frying oil residue as co-substrate and ultrasonication as pretreatment

Tetraselmis sp. microalgae biomass co-digestion with frying oil residue was investigated without or with an ultrasonication pretreatment to enhance methane production. Interestingly, compared to untreated Tetraselmis biomass, sonication pretreatment using specific energy of 1.6 kJ/g VS significantly improved specific methane production by 60.5%. However, increasing specific energy sonication to 3.2 kJ/g VS decreased the positive energy balance of whole process from 8.6 to 5.5 ± 0.3 kJ/g VS. Furthermore, it was demonstrated that the correction of the C/N ratio with frying oil waste coupled to the sonication of Tetraselmis biomass resulted in the highest methane yield of 443.7 ± 6.4 ml CH4/g VS and highest energy gains of 14.1 ± 0.2 kJ/g VS. This study proved the presence of a complementary effect between the co-digestion of Tetraselmis biomass with frying oil and the sonication pretreatment on specific methane production and energy recovery. Low ultrasonication specific energy is recommended as pretreatment process before Tetraselmis biomass anaerobic digestion.

Agglomeration of oil droplets assisted by low-frequency sonic pretreatment

The metalworking process in industrial buildings produces small droplets of oil. The efficient purification of small oil droplets can protect the built environment and human health. Purifier performance is generally related to particle size, and increasing the particle size by pretreatment significantly improves purification efficiency. Acoustic agglomeration is a widely recognized technique for increasing dust particle size. In this study, the agglomeration efficiency (decrease in the number concentration) of oil droplets with a particle size of <5 μm under a sound wave was investigated. The operating parameters studied included sound wave frequency (1000–4000 Hz), waveform (sine, square, and triangular waves), sound pressure level (130–145 dB), and oil droplet residence time (2.5–4 s). The results show that the agglomeration efficiency peaks with frequency and increases linearly with the sound pressure level, first increasing sharply and then leveling off with residence time. The following were the optimum parameters:1800 Hz sine wave, 145 dB, and residence time of 3 s. Under these operating conditions, the agglomeration efficiency is 9.9%. The enhancement of acoustic agglomeration on purification by a wire mesh filter was verified, and it was shown that the purification efficiency of a wire mesh filter for 0.3–5 μm oil droplets increased by over 20%.

Effects of ultrasound time, xanthan gum, and sucrose levels on the osmosis dehydration and appearance characteristics of grapefruit slices: Process optimization using response surface methodology

In this work, the novel use of ultrasonic pre-treatment and edible coating treatment during osmosis dehydration to optimize the weight reduction, moisture loss, sucrose gain, rehydration, and surface shrinkage using a response surface methodology (RSM) based on a central composite design (CCD) technique was successfully conducted on grapefruit slices. The process parameters include sonication pre-treatment time (5–10 min), xanthan-gum-based edible coating (0.1%-0.3%, w/w), and sucrose concentration (20–50 Brix), were examined and optimized for osmosis dehydration of grapefruit slices. At each step, three grapefruit slices were immersed in an ultrasonic water bath at 40 kHz, 150 W, and 20 C. Then, the sonicated slices were placed in a container contain sucrose and xanthan, and the container was put in a 50 C water-bath for 1 h. The optimum concentration of xanthan gum, sucrose, and time of treatment were predicted to be 0.15%, 20.0 Brix, and 10.0 min, respectively. Under this optimum condition, estimated values of response variables are as follows: weight reduction 14.14%, moisture loss 25.92%, solids gain 11.78%, rehydration ratio 203.40%, and shrinkage 2.90%. The weight reduction and moisture loss increased when the sonication time and sucrose concentration increased. Results demonstrated that the experimental data could be adequately fitted into a linear model with p-value ranging from 0.0001 to 0.0309 for all the variables examined. The rehydration of dried samples increased when xanthan concentration increased. Also, the weight reduction, moisture loss, sucrose absorption, and shrinkage declined with increasing in the xanthan levels.

Evaluation of the acidogenic fermentation potential of food industry by-products

Food industry annually generates huge amounts of waste and by-products, which represent untapped renewable resources to produce platform chemicals (e.g., organic acids) through biological processes, such as acidogenic fermentation (AF). Here, the AF potential of nine food industry by-products has been evaluated in anaerobic batch experiments, with main attention to the spectrum of attained products and related conversion yields. Farinaceous by-products, especially Bread Crust (BC) and Reground Pasta (RP), exhibited the highest conversion yield of the initial Chemical Oxygen Demand (COD) into AF products, up to values of 55 ± 2% and 75 ± 9% (for RP and BC, respectively). Substantially lower values, ranging between 6 ± 1% (for Spinach, SP) and 22 ± 1% (for Grape pomace Lees, GL) were achieved with by-products from the vegetable and winery industry. Further experiments with GL, SP, and WP (White exhausted grape Pomace) in the presence of glucose as reference substrate, revealed the coexistence of both recalcitrant and inhibitory compounds in GL and WP, whereas no inhibition on microbial activity was displayed by SP. A sonication pre-treatment experiment (at a low frequency of 20 kHz for 15 min and at room temperature) allowed increasing the conversion yield of GL by approximately 45%.

Cost-effective bio-methanation via oxalic acid coupled sonication pretreatment of Gracilaria salicornia

Gracilaria salicornia (macroalgae) can be used for the production of biofuels such as biomethane. Because of the complex cell wall structure in macroalgae, disintegration is crucial for anaerobic fermentation. The main goal of this study is to implement the combination of oxalic acid and ultrasonic pretreatment (SP) techniques over macroalgae Gracilaria salicornia in order to generate energy-efficient biomethane. A combination of ultrasonic pretreatment and oxalic acid (OSP) improves macromolecule availability in anaerobic fermentation, leading to enhanced biomethane production. Ultrasonic pretreatment was initially performed at 20–180 W for 5–60 min. A maximum solubilization of 9.19% was obtained, with a SCOD of 496 mg/L, at optimal conditions (140 W intensity, 30 min). Oxalic acid was added in various dosages from 0.01 to 0.1 N to optimize OSP conditions, enhance disintegration efficiency, and maximize biomethane production. With a SCOD of 914 mg/L and 16.93% SCOD solubilization, the best result was observed with 0.06 N oxalic acid dosage. A maximum biomethane production was achieved in the OSP sample (0.252 L/g COD) compared with the control (0.22 L/g COD) and SD (0.139 L/g COD) samples. As compared to SP, OSP was proved to be more energy-efficient. It was concluded that OSP was an efficient energy source for field applications. Combined OSP was a successful strategy for the production of energy-efficient biomethane.

Colloidal network oleogels structured by sonothermal conjugates of sodium caseinate and anionic gums

Food-grade colloidal network oleogels prepared by high internal phase emulsion (HIPE) templates are innovative systems in the field of solid fat mimetics. However, finding a colloidal stabilizer with outstanding interfacial activity that can stabilize the oleogels throughout storage (without oil-off) is still an uphill task. Herein, conjugates were prepared via sonothermal glycation of sodium caseinate (SC) with κappa-carrageenan (kC) or Alyssum homolocarpum seed gum (AHSG) and then successfully utilized in the stabilization of HIPEs. Emulsions were then oven-dried to obtain the oleogels. It was observed that HIPE stabilized by SC-AHSG conjugate prepared by 30 min sonication pretreatment (SC-AHSG30) resulted in the lowest mean droplet size (1.75 ± 0.01 μm) and polydispersity (0.47 ± 0.04) as well as the highest zeta potential (−33.43 ± 0.12 mV), centrifugal stability (82.20 ± 0.43%) and storage stability. This was justified by the highest glycation degree and interfacial activity of SC-AHSG30 conjugate. Likewise, the HIPE-templated oleogel stabilized by SC-AHSG30 conjugate revealed the highest apparent viscosity, gel strength (complex modulus = 621.80 ± 4.68 kPa), melting temperature (115.45 ± 0.65 °C), induction period of oxidation (25.14 ± 0.05 days) and was ultra-stable throughout 30-days of storage (no oil-off was noticed). This research confirms that sonothermally-glycated food hydrocolloids can be utilized as superb liquid oil structurants.

Prospects for Biodiesel Production from Emerging Algal Resource: Process Optimization and Characterization of Biodiesel Properties

The present work focuses on the optimization of the energy conversion process and the use of algal resources for biodiesel production with ultrasound and microwave techniques in Oedogonium, Oscillatoria, Ulothrix, Chlorella, Cladophora, and Spirogyra for the first time. The fuel properties are investigated to optimize the efficiency of the newly emerging algal energy feedstock. The study indicates that the optimized microwave technique improves the lipid extraction efficiency in Oedogonium, Oscillatoria, Ulothrix, Chlorella, Cladophora, and Spirogyra (38.5, 34, 55, 48, 40, and 33%, respectively). Moreover, the ultrasonic technique was also effective in extracting more lipids from Oedogonium sp., Oscillatoria sp., Ulothrix sp., Chlorella, Cladophora sp., and Spirogyra sp. (32, 21, 51, 40, and 36%, respectively) than from controls, using an ultra-sonication power of 80 kHz with an 8-min extraction time. The fatty acid composition, especially the contents of C16:0 and C18:1, were also enhanced after the microwave and sonication pretreatments in algal species. Enhancement of the lipids extracted from algal species improved the cetane number, high heating value, cold filter plugging point, and oxidative stability as compared to controls. Our results indicate that the conversion of biofuels from algae could be increased by the ultrasound and microwave techniques, to develop an eco-green and sustainable environment.

Characterization of Juice Extracted from Ultrasonic-Treated Red Pitaya Flesh

Red pitaya is a tropical fruit rich in phytonutrients essential for human health. The fruit is savored either through its processed products or raw consumption. This study aimed to assess the physicochemical properties of red pitaya juice extracted from ultrasonic-pretreated flesh. The red pitaya flesh was cut into cubes and subjected to different durations (20, 40, and 60 min) of ultrasonic treatment. The total soluble solids, pH, and titratable acidity of the juice were unaffected by pretreatment durations. Compared with the non-ultrasonic pretreated sample, the levels of organic acids, phenolics, and anthocyanins in red pitaya juice increased (p &lt; 0.05) following 60 min of ultrasonic pretreatment. The duration of sonication pretreatment influenced the antioxidant activity of red pitaya juice. This pilot study shows that pretreatment of the red pitaya flesh using ultrasound enhances the quality of its juice.

Effect of sonication - cooking on the immunoreactivity of soy slurry from germinated soybeans

Soy proteins are globular in nature and are resistant to denaturation with lower intensity thermal treatments like cooking. Likewise, germination can also alter the protein structure through the activity of various enzymes and sonication can disrupt the molecular structure through cavitation and other ultrasound effects, and contribute to some reduction in immunoreactivity (IR) of allergens. This study evaluated the effects of germination and sonication pretreatment in combination with common cooking on lowering the soy allergen IR. Germination was carried out for up to 120 h and ultrasound sonication treatments were given for 20, 40 and 60 min at room temperature. Cooking at 100 ^oC was carried out for 10 to 60 min. The soy allergen IR was evaluated using a commercial sandwich ELISA kit. The combined action of germination, sonication and cooking helped to reduce the soy allergen IR to single digit mg/L levels from the nearly 400 mg/L initial level in the 5% soy slurry (&gt; 99% reduction). These levels are lower than the reported threshold values of soy allergens in foods. In addition, the germination and ultrasound process was shown to reduce the anti-nutritional properties and enhance the phenolic and radical scavenging activity by over 50%.

Identification of novel potent biocatalysts, Bacillus thuringiensis STV1324a, Bacillus aquimaris STV1324b, and effective augmentation in a bioelectrochemical system for green energy production

Field studies were conducted through the unexplored wetlands of Kerala, the southernmost state of the Indian sub-continent, searching for the biocatalysts of the microbial fuel cell, the exoelectrogens. In-situ and ex-situ membrane-less microbial fuel cells were constructed to enrich, isolate, and characterize exoelectrogens. Exoelectrogenic property, Biofilm genesis ability, and waste removal capability of two novel candidates, Bacillus thuringiensis STV1324a and Bacillus aquimaris STV1324b, were confirmed with fuel cell operation, the chemical and biological oxygen demand removal studies and Scanning electron microscopy, respectively. Waste removal and clean water production ability of B.thuringiensis STV1324a and B.aquimaris STV1324b were successively analyzed on Coconut oil mill effluents, bakery wastewater, and synthetic municipal wastewater. Sonication pretreatment of wastes enhances overall waste removal properties up to 69.6% in B. thuringiensis STV1324a and 72% in B. aquimaris STV1324b. B. thuringiensis STV1324a and B.aquimaris STV1324b produced electricity with a maximum power density of 351.24mW/m 2 and 442.8 mW/m 2 , respectively. Exolectrogens with non-sonicated wastes shows lesser efficiency compared to those with sonicated. • Two novel exoelectrogens were isolated from unexplored wetlands of Kerala, India. • Waste removal properties of isolated exoelectrogens were analyzed. • Strains were successfully employed in MFC to generate bioelectricity. • SEM imaging was performed to confirm the biofilm of novel isolates on electrodes. • Pre-treatment of the substrate was found to be more effective on MFC performance.

Ultrasonic treatment of high phosphorus Australian iron ore fines

The trends and efficacy of ultrasonic pre-treatment before desliming high phosphorus Australian iron ore fines was investigated in the presented fundamental study. The −1 mm iron ore fines (57.5 wt% Fe, 2.47 wt% Si, 2.15 wt% Al, 0.132 wt% P) were subjected to sonication while the ultrasonic power, duration and pumping direction were varied. Sonication increased the iron grade and decreased the Si and Al assay in all size fractions except the ultrafines, where the opposite occurred.Ultrasonic treatment was found to depend on the total sonication energy input (up to 68 kJ) with no preference for either power or duration alone. The direction of pulp circulation was important and best results were obtained by pumping the pulp downwards past the ultrasonic probe rather than upwards.Sonication of iron ore fines suspended in water promotes deagglomeration, surface cleaning or disintegration, resulting in substantial deportment of mass from the coarser size fractions to the ultrafines (less than9.9 µm). The iron grade of ultrafines generated by sonication was lower than that of the ultrafines in the head sample, while the corresponding grades of Si, Al and P were higher. Increasing the sonication energy increased the proportion of hematite and decreased the proportion of kaolinite in material that deported to the ultrafines, which was most probably due to the surface action of ultrasonic treatment. A substantial portion of kaolinite (∼33 %) deported to the ultrafines during sonication using 68 kJ, compared with only 8.8 % of the goethite.Desliming of the unsonicated and sonicated samples was evaluated by calculated size classification. The sonication pre-treatments substantially improved the predicted grades of Fe, Si and Al in the deslimed products compared with unsonicated deslimed sample. For experiment using the highest sonication energy (68 kJ) and calculated desliming of < CS5 fraction, the predicted product iron grade improved by 2.8 wt% (1.6 wt% more than unsonicated) after desliming, while the silicon grade decreased relatively by 36.0 % (22.7 % more than unsonicated), the aluminium grade decreased relatively by 39.5 % (25.1 % more than unsonicated) and the predicted phosphorus content decreased relatively by 3.0 % (1.5 % more than unsonicated).The difference in sonication effect between Al, Si and P was due to the association with different minerals. Aluminium and silicon were mainly associated with kaolinite and soft goethite, which were easily disintegrated by ultrasound and deported to the ultrafines, while phosphorus was mainly associated with goethite (mostly of the hard types) present at around 40–48 wt% in most size fractions before and after sonication.

Effect of ultrasonic pretreatment on tocochromanol and carotenoid biofortification in maize (Zea mays L.) seedlings.

Maize is a sought-after food crop because it is micronutrient-rich and affordable. It is an excellent source of carotenoids and tocochromanols. To investigate ways to enhance the micronutrients in maize, we grew maize seedlings with ultrasonic pretreatment to study the effect of ultrasound pretreatment on the biofortification of tocochromanols and carotenoids using high-performance liquid chromatography and real-time quantitative polymerase chain reaction. Four tocopherol isomers, three tocotrienol isomers and six carotenoid components were measured in maize seedlings. Compared with the untreated maize seedlings, carotenoid content increased and reached the highest level at 8min ultrasonic pretreatment (19.21 ± 0.44 μg g-1 fresh weight (FW)), but tocotrienol content evidently decreased. Tocopherol dropped at first but began to rise after 8min ultrasonic pretreatment (258.1 ± 6.4μg g-1 FW). In particular, zeaxanthin in maize seedlings doubled after pre-sonication, while lutein was boosted to 11.81 ± 0.20 μg g-1 FW. Ultrasonic pretreatment changed the predominant component of tocochromanols in maize seedlings from γ-tocotrienol to α-tocopherol, with the latter content being 1.3 times higher than in the untreated group. Up-regulation of key genes involved in the biosynthesis of tocopherols and carotenoids in maize seedlings occurred as a result of both 2min and 6min sonication pretreatment. In particular, Zm HPPD, Zm ZE, Zm ZDS and Zm MPBQ-MT could partly explain the changes in these phytochemicals. Wet ultrasonic pretreatment could increase tocopherol and carotenoid accumulation in maize seedlings but decrease tocotrienol synthesis. Some up-regulating genes are related to relevant syntheses, such as Zm HPPD, Zm ZE, Zm ZDS and Zm MPBQ-MT, which could influence the accumulation of tocopherols and carotenoids after ultrasonic pretreatment. © 2022 Society of Chemical Industry.