Evaluation of a graphitic porous carbon modified with iron oxides for atrazine environmental remediation in water by adsorption.

In the last decades, the growth of world agricultural activity has significantly contributed to the increased presence of emerging pollutants such as atrazine (ATZ) in aquatic ecosystems. Due to its high stability to the natural or artificial degradation processes, the ATZ environmental remediation by adsorption has been investigated. In this study, a graphitic-porous-carbon- (GPC) based material with magnetic domains was applied to remove ATZ from aqueous solution. ATZ high adsorption efficiency in a reduced time was achieved in the presence of the GPC adsorbent, leading to a detailed investigation of the mechanisms involved in the adsorption processes. Pseudo-first-order (PFO), pseudo-second-order (PSO), Ritchie, Elovich, and Weber-Morris models were applied to calculate the kinetic process efficiency. Likewise, adsorption isotherms based on Langmuir, Freundlich, Temkin, and Redlich-Peterson models were applied for a detailed understanding of the adsorption mechanisms. GPC was successfully applied for ATZ remediation in natural waters, confirming its high potential for treating natural waters contaminated by ATZ using adsorption process. The material can also be recovered and reused for up to 4 application cycles due to its magnetic properties, showing that in addition to ATZ adsorption efficiency, its sustainable use can be achieved.

Speciation of As in environmental samples using the nano-TiO2/PCHG-FAAS online system.

This work presents an alternative method for arsenic speciation using the nano-TiO2 hydride generation photocatalytic hydride generation (PCHG) system, which is easily separated from the medium. Nano-TiO2 was studied as photocatalyst to reduction of arsenic species by UV-induced with formic acid and atomic absorption detection of different forms of arsenic [As (III), As (V), dimethylarsinic acid (DMA)] in environmental samples (water, sediment and plant). The effect of the average pH, the organic acid concentration, the ultraviolet irradiation time and their amount were investigated. With the presence of formic acid, the process was more effective in the reduction of arsenic when compared to other organic acids, mainly acetic acid. In addition, the photocatalytic hydride generation and flame atomic absorption spectrometry (nano-TiO2/PCHG-FAAS) increased the identification and quantification of different arsenic species. The ultrasound extraction procedure was used as a method to prepare samples with solutions of 1.0 mol L-1 phosphoric acid. The accuracy of the measurements (n = 12), calculated as relative standard deviation, was less than 8.6%. The detection limits for As (III) and As (total) in samples were 0.418 and 0.574 µg g-1, respectively.

Striking the balance: Unveiling the interplay between photocatalytic efficiency and toxicity of La-incorporated Ag3PO4.

Persistent molecules, such as pesticides, herbicides, and pharmaceuticals, pose significant threats to both the environment and human health. Advancements in developing efficient photocatalysts for degrading these substances can play a fundamental role in remediating contaminated environments, thereby enhancing safety for all forms of life. This study investigates the enhancement of photocatalytic efficiency achieved by incorporating La3+ into Ag3PO4, using the co-precipitation method in an aqueous medium. These materials were utilized in the photocatalytic degradation of Rhodamine B (RhB) and Ciprofloxacin (CIP) under visible light irradiation, with monitoring conducted through high-performance liquid chromatography (HPLC). The synthesized materials exhibited improved stability and photodegradation levels for RhB. Particularly noteworthy was the 2% La3+-incorporated sample (APL2), which achieved a 32.6% mineralization of CIP, nearly three times higher than pure Ag3PO4. Toxicological analysis of the residue from CIP photodegradation using the microalga Raphidocelis subcapitata revealed high toxicity due to the leaching of Ag + ions from the catalyst. This underscores the necessity for cautious wastewater disposal after using the photocatalyst. The toxicity of the APL2 photocatalysts was thoroughly assessed through comprehensive toxicological tests involving embryo development in Danio rerio, revealing its potential to induce death and malformations in zebrafish embryos, even at low concentrations. This emphasizes the importance of meticulous management. Essentially, this study adeptly delineated a thorough toxicological profile intricately intertwined with the photocatalytic efficacy of newly developed catalysts and the resultant waste produced, prompting deliberations on the disposal of degraded materials post-exposure to photocatalysts.

UV-Vis spectrophotometry coupled to chemometric analysis for the performance evaluation of atrazine photolysis and photocatalysis.

In this study, a spectrophotometric-chemometric (Spec-Chem) approach was applied as an alternative to chromatography to monitor ATZ and by-products after photolytic and photocatalytic oxidation aiming to unveil the ATZ degradation mechanism. Spec-Chem is an accessible, easy-to-operate, low-cost analytical approach to monitor atrazine (ATZ) and by-products, and its applicability was validated by HPLC, the reference technique for the evaluation of pollutant degradation mechanisms. The chromatographic (DChro) and spectrophotometric (DSpec) data found 95% and 57% ATZ removal after 30 min, respectively, proving that the DSpec erroneously induces a 38% loss in removal efficiency. When DSpec was treated by multivariate curve resolution (MCR) analysis for providing chemometric data (DChem), it found ATZ removal and hydroxyatrazine (HAT) formation statistically equal to DChro (t-test, p = 0.05). After unraveling the ATZ degradation mechanism using Spec-Chem, a new hypothesis for the kinetic calculation of ATZ degradation was presented, where the concentrations of ATZ and HAT were used to find k and R2 values representative for the ATZ degradation mechanism. The values found for k were compatible with the literature under similar conditions of ATZ degradation, and the linear correlation coefficients (R2 = 0.99) showed an optimal fit for the proposed hypothesis. Thus, Spec-Chem was successfully applied to unravel the mechanism of photocatalytic degradation of ATZ in the presence of TiO2, while k was obtained by the new hypothesis proposed that considered ATZ and HAT concentration as parameters of kinetic interest. Therefore, the importance of monitoring quantitatively ATZ and HAT were provided in this study, providing new information for the scientific community.

Photocatalytic degradation of Prozac® mediated by TiO2 nanoparticles obtained via three synthesis methods: sonochemical, microwave hydrothermal, and polymeric precursor.

Three different synthesis methods were applied to obtain TiO2 nanoparticles: microwave-assisted hydrothermal (TiO2-MW), sonochemical (TiO2-US), and polymeric precursor (TiO2-PP). The nanoparticles thus obtained presented 93% (TiO2-MW) and 92% (TiO2-US) anatase phase, and TiO2-PP 93% rutile phase. The TiO2-US sample performed best during the Prozac® photodegradation assays because of its lipophilic surface, attributable to the C-H groups therein. Additionally, adsorption rate and photodegradation were optimized by adjusting Prozac® solution to pH ~ 8. Following Prozac® photodegradation, quantitative monitoring of its by-products (PPMA, MAEB, and TFMP) was done using HPLC. This quantitative approach led us to conclude that semiconductor photoactivity cannot be discussed solely in terms of the main compound. Lastly, it was seen that these by-products compete with each other in the degradation mechanisms and are influenced by different materials. Graphical abstract.

Evaluation of atrazine degradation applied to different energy systems.

Atrazine is an herbicide widely used in crops and has drawn attention due to potential pollution present in soil, sediment, water, and food. Since conventional methods are not potentially efficient to persistent degradation of organic compounds, new technology has been developed to remove them, especially practices utilizing advanced oxidation processes (AOPs). This work aims to evaluate the use of different energies (ultraviolet (UV), microwaves (MW), and radiations (MW-UV)) to the herbicide atrazine through the process of photo-oxidation. These systems found degradation rates of around 12% (UV), 28% (MW), and 83% (MW-UV), respectively, with time intervals of 120 s. After the photolytic processes, the samples were analyzed at a wavelength scanning the range of 190 to 300 nm, where the spectral analysis of the signal was used to evaluate the degradation of atrazine and the appearance of some other peaks (degradation products). The spectrum evaluation resulting from photolytic processes gave rise to a new signal which was confirmed by chromatography. This spectrum indicated the possible pathway of atrazine degradation by the process of photolytic MW-UV, generating atrazine-2-hydroxy, atrazine-desethyl-2-hidroxy, and atrazine-desisopropyl-2-hydroxy. The process indicated that in all situations, chloride was present in the analytic structure and was substituted by a hydroxyl group, which lowered the toxicity of the compound through the photolytic processMW-UV. Chromatographic analysis ascertained these preliminary assessments using spectrophotometry. It was also significantly observed that the process can be optimized by adjusting the pH of the solution, which was evident by an improvement of 10% in the rate of degradation when subjected to a pH solution equal to 8.37.

Evaluation of atrazine degradation applied to different energy systems.

Atrazine is an herbicide widely used in crops and has drawn attention due to potential pollution present in soil, sediment, water, and food. Since conventional methods are not potentially efficient to persistent degradation of organic compounds, new technology has been developed to remove them, especially practices utilizing advanced oxidation processes (AOPs). This work aims to evaluate the use of different energies (ultraviolet (UV), microwaves (MW), and radiations (MW-UV)) to the herbicide atrazine through the process of photo-oxidation. These systems found degradation rates of around 12 % (UV), 28 % (MW), and 83 % (MW-UV), respectively, with time intervals of 120 s. After the photolytic processes, the samples were analyzed at a wavelength scanning the range of 190 to 300 nm, where the spectral analysis of the signal was used to evaluate the degradation of atrazine and the appearance of some other peaks (degradation products). The spectrum evaluation resulting from photolytic processes gave rise to a new signal which was confirmed by chromatography. This spectrum indicated the possible pathway of atrazine degradation by the process of photolytic MW-UV, generating atrazine-2-hydroxy, atrazine-desethyl-2-hidroxy, and atrazine-desisopropyl-2-hydroxy. The process indicated that in all situations, chloride was present in the analytic structure and was substituted by a hydroxyl group, which lowered the toxicity of the compound through the photolytic process MW-UV. Chromatographic analysis ascertained these preliminary assessments using spectrophotometry. It was also significantly observed that the process can be optimized by adjusting the pH of the solution, which was evident by an improvement of 10 % in the rate of degradation when subjected to a pH solution equal to 8.37.