Electrochemical and sonochemical advanced oxidation processes applied to tartrazine removal. Influence of operational conditions and aqueous matrix

The Evolution of Sonochemistry: From the Beginnings to Novel Applications

Sonochemistry is the use of ultrasonic waves in an aqueous medium, to generate acoustic cavitation. In this context, sonochemistry emerged as a focal point over the past few decades, starting as a manageable process such as a cleaning technique. Now, it is found in a wide range of applications across various chemical, physical, and biological processes, creating opportunities for analysis between these processes. Sonochemistry is a powerful and eco-friendly technique often called "green chemistry" for less energy use, toxic reagents, and residues generation. It is increasing the number of applications achieved through the ultrasonic irradiation (USI) method. Sonochemistry has been established as a sustainable and cost-effective alternative compared to traditional industrial methods. It promotes scientific and social well-being, offering non-destructive advantages, including rapid processes, improved process efficiency, enhanced product quality, and, in some cases, the retention of key product characteristics. This versatile technology has significantly contributed to the food industry, materials technology, environmental remediation, and biological research. This review is created with enthusiasm and focus on shedding light on the manifold applications of sonochemistry. It delves into this technique's evolution and current applications in cleaning, environmental remediation, microfluidic, biological, and medical fields. The purpose is to show the physicochemical effects and characteristics of acoustic cavitation in different processes across various fields and to demonstrate the extending application reach of sonochemistry. Also to provide insights into the prospects of this versatile technique and demonstrating that sonochemistry is an adapting system able to generate more efficient products or processes.

Intensified degradation of tartrazine dye present in effluent using ultrasound combined with ultraviolet irradiation and oxidants

Effluent containing tartrazine can affect the environment and human health significantly prompting the current study into degradation using a sonochemical reactor operated individually and combined with advanced oxidation processes. The optimum conditions for ultrasound treatment were established as dye concentration of 10 ppm, pH of 3, temperature as 35 °C, and power as 90 W. The combination approach of H2O2/UV, H2O2/US, and H2O2/UV/US resulted in higher degradation of 25.44%, 57.4%, and 74.36% respectively. Use of ZnO/UV/US approach increased the degradation significantly to 85.31% whereas maximum degradation as 93.11% was obtained for the US/UV/Fenton combination. COD reduction was found maximum as 83.78% for the US/UV/Fenton combination. The kinetic analysis showed that tartrazine dye degradation follows pseudo first-order kinetics for all the studied processes. Combination of Fenton with UV and US was elucidated as the best approach for degradation of tartrazine.

Convex optimization for maximizing the degradation efficiency of chloroquine in a flow-by electrochemical reactor

The degradation efficiency of chloroquine phosphate (CQ), an anti-COVID-19 drug, was investigated in a flow-by electrochemical reactor (FBER) provided with two boron-doped diamond (BDD) electrodes (as cathode and anode) under batch recirculation mode. A central composite rotatable design (CCRD) was run down to model and assess the influence of initial pH in an interval of 3.71 to 11.28, the current density in an interval of 34.32 to 185.68 mA cm-2, and liquid volumetric flow rate in an interval of 0.58 to 1.42 L min-1, and conduct the convex optimization to obtain the maximum degradation efficiency. Experimental results were modeled through a second-order polynomial equation having a determination coefficient (R2) of 0.9705 with a variance coefficient of 1.1%. Optimal operating conditions found (initial pH of 5.38, current density (j) of 34.4 mA cm-2, and liquid flow rate (Q) of 1.42 L min-1) led to a global maximum degradation efficiency, COD removal efficiency, and mineralization efficiency of 89.3, 51.6 and 53.1%, respectively, with an energy consumption of 0.041 kWh L-1 within 9 h of treatment. Additionally, a pseudo-zero-order kinetic model was demonstrated to fit the experimental data and the calculated pseudo-zero-order kinetic constant (kapp) was 13.14 mg L-1 h-1 (2.54 × 10-5 mol dm-3 h-1). Furthermore, the total operating cost was of 0.47 US$ L-1. Finally, this research could be helpful for the treatment of wastewater containing an anti-COVID-19 drug such as CQ.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10008-023-05452-7.

Recent advances and prospects in electrochemical coupling technologies for metal recovery from water

With the development of our society, the desire to recover valuable metal resources from metal-containing wastewaters or natural water bodies is becoming increasingly stronger nowadays. To overcome the limitations of single techniques, coupling technologies with synergistic effects are attracting increasing attention regarding metal resource recovery from water with particular interest in electrochemical coupling technologies in view of the advantages of electrochemical methods. This state-of-the-art review comprehensively presented the mechanisms and performance of electrochemical coupling systems for metal recovery from water. To give a clear overview of current research trends, technologies coupled with electrochemical processes can be categorized into six main types: electrochemical techniques, membrane modules, adsorption/extraction techniques, sonication technologies, energy supply techniques and others. The electrochemical coupling system has shown synergistic advantages (e.g., improving metal recovery efficiency, reducing energy consumption) over single technologies. We then discuss the remaining challenges, present corresponding solutions, and put forward future directions for current electrochemical coupled systems towards metal recovery. This review is conducive to broadening the potential applications of electrochemical coupling processes for metal recovery and sustainable water treatment.

Highly effectual photocatalytic degradation of tartrazine by using Ag nanoparticles decorated on Zn-Cu-Cr layered double hydroxide@ 2D graphitic carbon nitride (C3N5)

Pollution of water resources is one of the main concerns of many countries. This issue originates from the entry of diverse pollutants, including dye compounds, into water sources. In this work, ternary Zn-Cu-Cr layered double hydroxides (LDH) supported on graphitic carbon nitride (g-C₃N₅) decorated by silver nanoparticles (C₃N₅-LDH-Ag) was first prepared. Application of various characterization techniques such as SEM, XRD, and FT-IR revealed that the synthesized nanocomposite was composed of Zn-Cu-Cr LDH nanoparticles, g-C₃N₅ nanosheets, and Ag nanoparticles. The prepared nanomaterials were employed for the photodegradation of tartrazine in aqueous solutions. It was found that the C₃N₅-LDH-Ag catalyst outperformed their pure g-C₃N₅, Zn-Cu-Cr LDH, and C₃N₅-LDH composite in photocatalytic degradation of tartrazine under visible light irradiation. Tartrazine (20 mg/L) can be entirely removed by 0.25 g/L C₃N₅-LDH-Ag photocatalyst under 1 h visible light irradiation (200 W) at pH 6 with a rapid degradation rate constant (k) that is 4.4, 3.9, and 2.6 times higher than that of pure C₃N₅, Zn-Cu-Cr LDH, and C₃N₅-LDH component, respectively. The formation of hydroxyl radicals on the surface of C₃N₅-LDH-Ag as the main active species was approved by the capturing experiment. The finding results approved the stability and reusability of C₃N₅-LDH-Ag in four photocatalytic degradation cycles. In general, our findings revealed that the synthesized nanocomposite could be employed as an efficient photocatalyst in environmental remediation.

New hybrid strategy of the photo-Fered-Fenton process assisted by O3 for the degradation of wastewater from the pretreatment of biodiesel production

The present work aims to fill a scientific gap regarding the treatment of wastewater from the enzymatic pretreatment of biodiesel production (WEPBP), as well as the identification of organic contaminants present in this complex matrix. Different treatment strategies were proposed for the removal of total organic carbon (TOC) and chemical oxygen demand (COD) from WEPBP. The interesting combination of O₃/H₂O₂/UV-Vis and electrocoagulation (EC) process was studied in two setups, with the EC process applied prior to O₃/H₂O₂/UV-Vis and vice versa. Further, the innovative hybrid system based on the photo-Fered-Fenton process with O₃ addition (PEF-Fere-O₃) was preliminarily studied for WEPBP treatment. The hybrid system provided the best results for the WEPBP treatment when the reactor was operated at pH of 4.5, 65 mg O₃ L^-1 and 10000 mg H₂O₂ L^-1, UV-Vis was used as the irradiation source, and the current intensity of 3.0 A. Removals of 45% of TOC and 68.7% of COD were reached within 45 min. Oleic acid, linoleic acid, and Diisooctyl phthalate (DIOP) were the main organic contaminants identified in the WEPBP as determined by Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Acute toxicity assays with the bio indicator Artemia salina were carried out in untreated and treated WEPBP samples, indicating that the PEF-Fere-O₃ treatment decreased the amount of contaminants present in the WEPBP as well as reduced the toxicity levels and increased biodegradability index, suggesting its great potential for the treatment of complex industrial wastewaters.

In-situ hydrothermal synthesis of CNT decorated by nano ZnS/CuO for simultaneous removal of acid food dyes from binary water samples

The zinc sulfide/copper oxide–carbon nanotube nanocomposite (ZnS/CuO-CNT) was fabricated by using an in-situ hydrothermal synthesis method and was used for simultaneous ultrasound-assisted adsorptive removal of a binary mixture of ponceau 4R (P4R) and tartrazine (TA) acid food dyes from contaminated water. The as-synthesized ZnS/CuO-CNT was described by FESEM, XRD, FTIR, BET, and zeta potential analysis. The results included nested network morphology, high purity with the crystalline structure, oxygen-containing functional groups, mesoporous/micropores texture with cumulate interspace, specific surface area of 106.54 m² g^-1, and zero-point charge (pH_zpc) of 5.3. In adsorption experiments, the simultaneous effect of main independent variables, including solution pH, adsorbent dosage, concentration of each dye, temperature, and sonication time on the removal efficiency of dyes was studied systematically using the central composite design (CCD) method based on response surface methodology (RSM). Also, the second-order multivariate equation was presented to determine the relationship between the removal efficiencies of P4R and AT dyes and six independent effective variables. The high correlation coefficient (R² ≥ 0.99), significant p-value (P < 0.0001), and non-significant lack-of-fit (P > 0.05) showed the high accuracy, and validity of the proposed model to predict the removal efficiency of P4R and TA acid food dyes. The experimental removal efficiency for P4R and TA dyes was found to be 98.45 ± 2.54, and 99.21 ± 2.23, respectively. Also, the Langmuir maximum adsorption capacity for P4R and TA dyes was determined to be 190.1 mg g^-1 and 183.5 mg g^-1, respectively. Finally, the adsorbent's reusability was tested for six periods and could be reused repeatedly without significant reduction in adsorption performance.

Emerging Pollutants in Wastewater, Advanced Oxidation Processes as an Alternative Treatment and Perspectives

Emerging pollutants are present in wastewaters treated by conventional processes. Due to water cycle interactions, these contaminants have been reported in groundwater, surface water, and drinking waters. Since conventional processes cannot guarantee their removal or biotransformation, it is necessary to study processes that comply with complete elimination. The current literature review was conducted to describe and provide an overview of the available information about the most significant groups of emerging pollutants that could potentially be found in the wastewater and the environment. In addition, it describes the main entry and distribution pathways of emerging contaminants into the environment through the water and wastewater cycle, as well as some of the potential effects they may cause to flora, fauna, and humans. Relevant information on the SARS-CoV-2 virus and its potential spread through wastewater is included. Furthermore, it also outlines some of the Advanced Oxidation Processes (AOPs) used for the total or partial emerging pollutants removal, emphasizing the reaction mechanisms and process parameters that need to be considered. As well, some biological processes that, although slow, are effective for the biotransformation of some emerging contaminants and can be used in combination with advanced oxidation processes.

The surfactant-ionic liquid bi-functionalization of chitosan beads for their adsorption performance improvement toward Tartrazine

In this study, the ionic liquid (Aliquat-336) and anionic surfactant (cetyltrimethylammonium bromide, CTAB) bi-functionalized chitosan beads were prepared and characterised using different techniques, including FTIR, XRD, SEM, EDS and BET surface area analysis. The characteristic analysis confirmed the successful conjugation of chitosan beads with both surfactant and ionic liquid. The novel fabricated beads (CS-CTAB-AL) were efficiently employed, as a high-performance adsorbent, for the removal of Tartrazine (TZ), an anionic food dye, from polluted water. The optimum adsorption of TZ onto the CS-CTAB-AL was found at 2 g L^-1 of adsorbent in the wide pH range of 4-11, whereas just 45 min was required to reach more than 90% adsorption efficiency in the studied conditions. Also, the adsorption and kinetic studies showed that the experimental data well fitted the pseudo-first-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of prepared beads was found to be 45.95 mg g^-1 at 45 °C. The adsorption properties of enabling CS-CTAB-AL conjugation introduced a new type of adsorbents, exploited the combination of ionic liquid and surfactant capabilities for wastewater treatment.

New research on water, waste and energy management, with special focus on antibiotics and priority pollutants

The Editors of the Virtual Special Issue (VSI) "New Research on Water, Waste and Energy Management, with Special Focus on Antibiotics and Priority Pollutants" (VSI WWEM-20) here present details corresponding to papers that have been accepted, as well as further comments on the matter. It should be noted that the VSI should be associated to a Conference that had been initially programmed to be held in Rome during the summer of 2020, Unfortunately, it was postponed due to the COVID-19 pandemic. That conference was one of those within the series called "International Congress on Water, Waste and Energy Management". Although the Conference was postponed, the Call for Papers for the VSI was maintained by this journal. As a result, a set of very interesting papers were accepted after a careful peer-review process. We hope that it will be complemented with additional VSIs associated to future conferences corresponding to the series, increasing the knowledge on the topic.