Search Results (10)

Phytoremediation is considered as a green alternative for remediating metal-contaminated soil and water, yet further efforts are needed to minimise secondary pollution after phytoremediation. This study investigates a cost-effective and sustainable method to synthesise carbon quantum dot supported on zinc oxide (CQD-ZnO) composites using extracted zinc (Zn) from post-phytoremediated plants, plant extracts, and CQDs derived from water hyacinth (Eichhornia crassipes) for the sonocatalytic degradation of malachite green. The CQD-ZnO materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface analysis, and ultraviolet–visible (UV–Vis) spectroscopy to confirm their crystalline structure, morphology, functional groups, surface area, and optical properties. The composites exhibited disaggregation of agglomerates, high crystallinity, and increased carbon content due to the addition of CQDs containing phenolic functional groups (e.g., polyphenols, flavonoids) from the plant extract. The highest sonocatalytic degradation efficiency (84.52%) was achieved after 90 min of treating 10 ppm malachite green using 1 g/L of the CQD-ZnO composite at a natural pH, with 300 W ultrasonic power at 25 kHz. This study paves the way for the development of environmentally friendly, high-performance sonocatalysts from post-phytoremediated plants for wastewater treatment applications. Full article

This study explores the sonocatalytic activity of gold nanoclusters (Au NCs) combined with titanium dioxide (TiO₂) nanoparticles, forming Au NCs/TiO₂ composites. The hybrid material significantly enhances hydroxyl radical (•OH) generation under ultrasonic conditions, attributed to high-energy cavitation bubbles formed during ultrasonication. The effects of frequency (200, 430, and 950 kHz) and power were systematically evaluated on Au₁₄₄/TiO₂ composites, identifying 430 kHz as optimal for •OH production due to its efficient cavitation energy. Au₁₄₄ NCs function as electron traps, reducing electron–hole recombination in ultrasonically activated TiO₂, thereby improving charge separation and enhancing •OH generation. Size-dependent effects were also studied, showing an efficiency trend of Au₁₄₄ > Au₂₅ > plasmonic Au nanoparticles > bare TiO₂. These findings highlight the importance of ultrasonication frequency and Au NC size in optimizing sonocatalytic performance in the Au NCs/TiO₂ composites, providing valuable insights for designing advanced sonocatalysts with applications in chemical synthesis, environmental remediation, and biomedical fields. Full article

The development of environmentally friendly technology is vital to effectively address the issues related to environmental deterioration. This work integrates ZnO-decorated MoS₂ (MZ) to create a high-performing PVDF-based PVDF/MoS₂-ZnO (PMZ) hybrid polymer composite film for sonocatalytic organic pollutant degradation. An efficient synergistic combination of MZ was identified by altering the ratio, and its influence on PVDF was assessed using diverse structural, morphological, and sonocatalytic performances. The PMZ film demonstrated very effective sonocatalytic characteristics by degrading rhodamine B (RhB) dye with a degradation efficiency of 97.23%, whereas PVDF only degraded 17.7%. Combining MoS₂ and ZnO reduces electron–hole recombination and increases the sonocatalytic degradation performance. Moreover, an ideal piezoelectric PVDF polymer with MZ enhances polarization to improve redox processes and dye degradation, ultimately increasing the degradation efficiency. The degradation efficiency of RhB was seen to decrease while employing isopropanol (IPA) and p-benzoquinone (BQ) due to the presence of reactive oxygen species. This suggests that the active species •O₂⁻ and •OH are primarily responsible for the degradation of RhB utilizing PMZ2 film. The PMZ film exhibited improved reusability without substantially decreasing its catalytic activity. The superior embellishment of ZnO onto MoS₂ and effective integration of MZ into the PVDF polymer film results in improved degrading performance. Full article

The cavitation effect is an important geochemical phenomenon, which generally exists under strong hydrodynamic conditions. Therefore, developing an economical and effective sonocatalyst becomes a vital method in capitalizing on the cavitation effect for energy generation. In this study, we first report a novel Fe₃O₄ sonocatalyst that can be easily separated using a magnetic field and does not require any additional cocatalysts for H₂ production from H₂O. When subjected to ultrasonic vibration, this catalyst achieves an impressive H₂ production rate of up to 175 μmol/h/USD (where USD stands for dollars), surpassing most previously reported mechanical catalytic materials. Furthermore, the ease and efficiency of separating this catalyst using an external magnetic field, coupled with its effortless recovery, highlight its significant potential for practical applications. By addressing the key limitations of conventional sonocatalysts, our study not only demonstrates the feasibility of using Fe₃O₄ as a highly efficient sonocatalyst but also showcases the exciting possibility of using a new class of magnetically separable sonocatalysts to productively transform mechanical energy into chemical energy. Full article

Dual-frequency ultrasound (DFUS) coupled with sonocatalysts has emerged to be an advanced tool for antimicrobial applications in medicine but remains scarcely studied for water disinfection. In the present work, we first integrated high-frequency DFUS (120 + 1700 kHz), persulfate (S₂O₈²⁻) and ZnO nano- (50 nm) and microparticles (1 μm) for eradicating Escherichia coli and Enterococcus faecalis in synthetic water. For E. coli, the efficiency of DFUS-based processes can be ranked as follows: DFUS < DFUS/ZnO < DFUS/S₂O₈²⁻ < DFUS/ZnO/S₂O₈²⁻. A similar efficiency of the DFUS/S₂O₈²⁻ and DFUS/ZnO/S₂O₈²⁻ processes was found for more resistant E. faecalis. In the absence of persulfate, the performance of 1 μm ZnO was higher than that observed with 50 nm for inactivating E. coli via the DFUS/ZnO and 1700 kHz/ZnO processes. A synergy of DFUS in terms of 5-log (total) reduction was found in the S₂O₈²⁻/ZnO-based systems, being higher for E. faecalis (synergistic coefficient = 1.8–3.0). The synergistic effect was proposed to be driven by the boosted generation of reactive oxygen species and sonoporation. This study opens prospects for the development of novel DFUS-based piezo-catalytic systems for efficient water disinfection. Full article

Biochar has been widely used in the fields of environment and energy, and green preparation can make biochar-based materials more environmentally friendly. Particularly, in the low-temperature pyrolysis of biochar, labile C with low biological toxicity is the main influencing factor of bacteria in soil. Therefore, it is worth studying to develop the fabrication technology of low-temperature pyrolysis biochar with rich pore structure. The mechanical effect of ultrasonic cavitation is considered to be an effective strategy for the preparation of biochar. However, the sonochemical effects on biochar remain to be studied. In this review, ultrasonic modification and ultrasonic-chemical modification on biochar has been reviewed. Metal oxide/biochar composites can also be obtained by an ultrasonic-chemical method. It is worth mentioning that there have been some reports on the regeneration of biochar by ultrasound. In addition to ultrasonic preparation of biochar, ultrasound can also trigger the sonocatalytic performance and promote the adsorption ability of biochar for the removal of harmful substances. The catalytic mechanism of ultrasound/biochar needs to be further investigated. For application, biochar prepared by ultrasound has been used for the removal of heavy metals in water, the adsorption of carbon dioxide, and soil remediation. Full article

This study focused on the modification of graphitic carbon nitride (g-C₃N₄) using carbon which was obtained from the pyrolysis of coconut shell husk. The sonocatalytic performance of the synthesized samples was then studied through the degradation of malachite green. In this work, pure g-C₃N₄, pure carbon and carbon/g-C₃N₄ composites (C/g-C₃N₄) at different weight percentages were prepared and characterized by using XRD, SEM-EDX, FTIR, TGA and surface analysis. The effect of carbon amount in the C/g-C₃N₄ composites on the sonocatalytic performance was studied and 10 wt% C/g-C₃N₄ showed the best catalytic activity. The optimization study was conducted by using response surface methodology (RSM) with a central composite design (CCD) model. Three experimental parameters were selected in RSM including initial dye concentration (20 to 25 ppm), initial catalyst loading (0.3 to 0.5 g/L), and solution pH (4 to 8). The model obtained was found to be significant and reliable with R² value (0.9862) close to unity. The degradation efficiency of malachite green was optimized at 97.11% under the conditions with initial dye concentration = 20 ppm, initial catalyst loading = 0.5 g/L, solution pH = 8 after 10 min. The reusability study revealed the high stability of 10 wt% C/g-C₃N₄ as sonocatalyst. In short, 10 wt% C/g-C₃N₄ has a high potential for industrial application since it is cost effective, reusable, sustainable, and provides good sonocatalytic performance. Full article

In this study, a novel cellulose/Ag/TiO₂ nanocomposite was successfully synthesized via the hydrothermal method. The cellulose extracted from oil palm empty fruit bunch (OPEFB) could address the disposal issue created by OPEFB biomass. Characterization studies such as FESEM, EDX, HRTEM, XRD, FTIR, UV–Vis DRS, PL, XPS, and surface analysis were conducted. It was observed that the incorporation of cellulose could hinder the agglomeration, reduce the band gap energy to 3 eV, increase the specific surface area to 150.22 m³/g, and lower the recombination rate of the generated electron-hole pairs compared to Ag/TiO₂ nanoparticles. The excellent properties enhance the sonocatalytic degradation efficiency of 10 mg/L Congo red (up to 81.3% after 10 min ultrasonic irradiation) in the presence of 0.5 g/L cellulose/Ag/TiO₂ at 24 kHz and 280 W. The improvement of catalytic activity was due to the surface plasmon resonance effect of Ag and numerous hydroxyl groups on cellulose that capture the holes, which delay the recombination rate of the charge carriers in TiO₂. This study demonstrated an alternative approach in the development of an efficient sonocatalyst for the sonocatalytic degradation of Congo red. Full article

The sulfur-doped carbon nitride/cobalt ferrite nanocomposite (SCN/CoFe₂O₄) was prepared via ultrasonication and studied for the sonocatalytic degradation of wastewater organic dye pollutants including methylene blue, rhodamine B, and Congo red. The X-ray photoelectron spectroscopy confirmed the presence and atomic ratios of S, C, N, Co, Fe, and O elements and their corresponding bonds with Co²⁺ and Fe³⁺ cations. The nanocomposite was found to have aggregated nanoparticles on a sheet-like structure. The bandgap energy was estimated to be 1.85 eV. For the sonocatalytic degradation of 25-ppm methylene blue at 20 kHz, 1 W and 50% amplitude, the best operating condition was determined to be 1 g/L of catalyst dosage and 4 vol % of hydrogen peroxide loading. Under this condition, the sonocatalytic removal efficiency was the highest at 96% within a reaction period of 20 min. SCN/CoFe₂O₄ outperformed SCN and CoFe₂O₄ by 2.2 and 6.8 times, respectively. The SCN/CoFe₂O₄ nanocomposite was also found to have good reusability with a drop of only 7% after the fifth cycle. However, the degradation efficiencies were low when tested with rhodamine B and Congo red due to difference in dye sizes, structural compositions, and electric charges. Full article

ZnO and ZnO-Cu₂O were grown on aluminum foam using hydrothermal method. Due to the positively charged sites on the surface, both ZnO and ZnO-Cu₂O show higher adsorption capability towards anionic dyes, but poorer adsorption capability towards cationic dyes. The adsorption ability of ZnO-Cu₂O is smaller than that of ZnO since there is a depletion layer at the interface. In order to decolorize cationic dyes, ZnO and ZnO-Cu₂O are used as sono-catalyst with ultrasonic irradiation. The ZnO-Cu₂O is better than ZnO in sono-catalysis decoloration of cationic dyes. This may be due to the enhanced piezoelectricity and electrochemical activity, as the free electrons in ZnO are reduced in the depletion layer. Full article