Degradation of SDBS in water solutions using plasma in gas-liquid interface discharge: Performance, byproduct formation and toxicity evaluation

Probing the interaction mechanism of SDBS with AtPrxQ from Arabidopsis thaliana: Insight into the molecular toxicity to plants

As the most universally used anionic surfactant, ubiquitous existence and accumulation of sodium dodecyl benzene sulfonate (SDBS) in the environment has inevitably imposed the associated harmful impacts to plants due to producing excessive reactive oxygen species. However, the underlying hazardous mechanism of the SDBS-induced oxidative stress to plants at molecular level has never been reported. Here, the molecular interaction of AtPrxQ with SDBS was explored for the first time. The intrinsic fluorescence of AtPrxQ was quenched based on static quenching, and a single binding site of AtPrxQ towards SDBS and the potential interaction forces driven by hydrophobic interactions were predicted from thermodynamic parameters and molecular docking results. Besides, the interaction pattern of AtPrxQ and SDBS was also confirmed by the bio-layer interferometry with moderate binding affinity. Moreover, the structural changes of AtPrxQ along with the destructions of the protein framework and the hydrophobic enhancement around aromatic amino acids were observed upon binding with SDBS. At last, the toxic effects produced by SDBS on peroxidase activities and Arabidopsis seedlings growth were also characterized. Thus this work may provide insights on the molecular interactions of AtPrxQ with SDBS and assessments on the biological hazards of SDBS to plants even for the agriculture.

Remediation of Surfactants Used by VUV/O3 Techniques: Degradation Efficiency, Pathway and Toxicological Analysis

Surfactants are increasingly used in systems that come into contact with the human body, such as food, pharmaceuticals, cosmetics and personal hygiene products. Increasing attention is being devoted to the toxic effects of surfactants in various human contact formulations, as well as the removal of residual surfactants. In the presence of ozone (O₃), anion surfactants-a characteristic micro-pollutant-such as sodium dodecylbenzene sulfonate (SDBS) in greywater, can be removed using radical advanced oxidation. Herein, we report a systematic study of the SDBS degradation effect of O₃ activated by vacuum ultraviolet (VUV) irradiation and the influence of water composition on VUV/O₃, and determined the contribution of radical species. We show a synergistic effect of VUV and O₃, while VUV/O₃ reached a higher mineralization (50.37%) than that of VUV (10.63%) and O₃ (29.60%) alone. The main reactive radicals of VUV/O₃ were HO•. VUV/O₃ had an optimal pH of 9. The addition of SO₄^2- had almost no effect on the degradation of SDBS by VUV/O₃, Cl^- and HCO₃^- slightly reduced the reaction rate, and NO₃^- had a significant inhibition on the degradation. In total, SDBS had three isomers, with which the three degradation pathways were very comparable. Compared with SDBS, the toxicity and harmfulness of the degradation by-products of the VUV/O₃ process decreased. Additionally, VUV/O₃ could degrade synthetic anion surfactants from laundry greywater effectively. Overall, the results show the potential of VUV/O₃ in safeguarding humans from residual surfactant hazards.

An overview on surfactants as pollutants of concern: Occurrence, impacts and persulfate-based remediation technologies

Surfactants are molecules that reduce interfacial energy and increase solubility of other pollutants in water. These properties make them suitable for various domestic and industrial applications, soil remediation, pesticide formulation, among others. The increase in their use and the lack of strict regulations regarding their disposal and management is a matter of concern and requires more attention since the release and distribution of these compounds into the environment can modify important water quality parameters. As a result of these changes, different toxicological effects to aquatic organisms are discussed and exposed herein. On this basis, we provide an overview of the classes of surfactants, as well as their occurrence in different aqueous matrices. In addition, existing regulations around the world regarding their concentration limit for different environments are discussed. Current research focuses on the application of conventional treatments, such as biological treatments; notwithstanding, more toxic and bioaccumulative products can be generated. Advanced Oxidation Processes are promising alternatives and have also been widely applied for the removal of surfactants. This study provides, for the first time, an overview of the application of persulfate-based processes for surfactants degradation based on recent literature findings, as well as the various factors related to the activation of the persulfate anions. This review also highlights the challenges and opportunities for future research to overcome the obstacles to the practical application of this process.

Rapid determination of three textile surfactants in environmental samples by modeling excitation-emission second-order data with multi-way calibration methods

The textile industry is an important potential source of environmental pollution due to the use of chemical products. Dyes, hydrolyzed dyes, and surfactants, among others, are chemical compounds present in wastewater of textile plant. Moreover, the anionic surfactants have toxic effects for various aquatic organisms even in low concentrations. The methodologies investigated to quantify surfactants, in general, consume a lot of analysis time and frequently use toxic or environmentally objectionable reagents. For these reasons, the objective of this work was to develop a quick and simple method to quantify surfactants without the use of expensive reagents and equipment, avoiding extraction and preconcentration stages. The proposed method is based on fluorescent spectroscopy measurements for the acquisition of second-order data in excitation-emission matrices and multivariate calibration techniques applied to the data. The unfolded partial least squares combined to residual bilinearization (U-PLS/RBL) algorithm was better than parallel factor analysis (PARAFAC). U-PLS/RBL accurately quantified alkylnonylphenolethoxylated (APEO), dodecylbenzenesulfonic acid (ADBS), and 2-phenoxy-ethoxylated fatty alcohol (AGFE) surfactants. The chemometric model obtained good analytical figures of merit: REP% between 5 and 13 and LOQ between 0.45 and 2.77 μg mL^-1. This methodology had no significant difference compared with results obtained by a HPLC-FD reference technique, in addition with a considerable reduction in analysis time, reagent consumption, and therefore lower cost. For environmental applications, APEO, ADBS, and AGFE were quantify in textile wastewater treatment and in the receiving water body. The concentrations varied from 8.73 to 73.94 μg mL^-1 in the textile wastewater and were not detected in the receiving water body.

Prediction of the joint action of binary mixtures based on characteristic parameter k∙ECx from concentration-response curves

The evaluation of joint toxicity of mixtures is an important topic in toxicology. Previous studies have found that the parameter k∙EC_x of concentration response curves (CRCs) can be used to assess the applicability of concentration addition model (CA). This study further assesses the predictability of k∙EC_x on the joint toxicity evaluation. The toxicities of the twelve environmental pollutants, as well as those of binary mixtures with an equivalent-effect concentration ratio, to Vibrio fischeri were determined by using the microplate toxicity analysis. The toxicity evaluation of mixtures was conducted by CA and independent action model (IA). The relationship between the joint toxicity (measured by the relative model deviation ratio (rMDR)) and the k∙EC_x was studied. The results shows that the k∙EC_x could reflect the shape of CRCs in the whole concentration range. According to the IA and CA, 65% of the mixtures produce strong antagonistic or synergistic effect due to the significant difference of k∙EC_x. The percentage of the relative difference of k∙EC_x of components and the rMDR_x can be fitted by an exponential function. Different types of interactions could be described using this function. It is suggested that the joint toxicity of binary mixtures can be assessed with the parameter k∙EC_x, which can quickly get very important data when planning experiments, but also reduce the number of experiments.