Electrochemical detection and simultaneous removal of endocrine disruptor, bisphenol A using a carbon felt electrode

An insight on the plausible biological and non-biological detoxification of heavy metals in tannery waste: A comprehensive review

A key challenge for the tannery industries is the volume of tannery waste water (TWW) generated during the processing of leather, releasing various forms of toxic heavy metals resulting in uncontrolled discharge of tannery waste (TW) into the environment leading to pollution. The pollutants in TW includes heavy metals such as chromium (Cr), cadmium (Cd), lead (Pb) etc, when discharged above the permissible limit causes ill effects on humans. Therefore, several researchers have reported the application of biological and non-biological methods for the removal of pollutants in TW. This review provides insights on the global scenario of tannery industries and the harmful effects of heavy metal generated by tannery industry on micro and macroorganisms of the various ecological niches. It also provides information on the process, advantages and disadvantages of non-biological methods such as electrochemical oxidation, advanced oxidation processes, photon assisted catalytic remediation, adsorption and membrane technology. The various biological methods emphasised includes strategies such as constructed wetland, vermitechnology, phytoremediation, bioaugmentation, quorum sensing and biofilm in the remediation of heavy metals from tannery wastewater (TWW) with special emphasize on chromium.

Electrochemical Detection of Bisphenol A Based on Gold Nanoparticles/Multi-Walled Carbon Nanotubes: Applications on Glassy Carbon and Screen Printed Electrodes

Bisphenol A (BPA) has been classified as an endocrine-disrupting substance that may cause adverse effects on human health and the environment. The development of simple and sensitive electrochemical biosensors is crucial for the rapid and effective quantitative determination of BPA. This work presents a study on electrochemical sensors utilizing gold nanoparticle-modified multi-walled carbon nanotubes (CNT/AuNPs). Glassy carbon electrodes (GCEs) and screen-printed electrodes (SPEs) were conveniently modified and used for BPA detection. AuNPs were electrodeposited onto the CNT-modified electrodes using the galvanostatic method. The electrodes were properly modified and characterized by using Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance analysis (EIS). The electrochemical response of the sensors was studied using differential pulse voltammetry (DPV) and constant potential amperometry (CPA) for modified GCE and SPE electrodes, respectively, and the main analytical parameters were studied and optimized. Problems encountered with the use of GCEs, such as sensor degradation and high limit of detection (LOD), were overcome by using modified SPEs and a flow injection device for the measurements. Under this approach, an LOD as low as 5 nM (S/N = 3) was achieved and presented a linear range up to 20 μM. Finally, our investigation addressed interference, reproducibility, and reusability aspects, successfully identifying BPA in both spiked and authentic samples, including commercial and tap waters. These findings underscore the practical applicability of our method for accurate BPA detection in real-world scenarios. Notably, the integration of SPEs and a flow injection device facilitated simplified automation, offering an exceptionally efficient and reliable solution for precise BPA detection in water analysis laboratories.

Preparation of amino-functionalized triazine-based hyper-crosslinked polymer for efficient adsorption of endocrine disruptors

Herein, two novel amino-functionalized triazine-based hyper-crosslinked porous polymer (NH2-HCPs) (named as DPT-BB, DPT-DX) were designed and synthesized by direct crosslinking of 2,4-diamino-6-phenyl-1,3,5-triazine (DPT) with 4,4'-bis(chloromethyl)-1,1'-biphenyl (BB) or α, α'-dichloro-p-xylene (DX). Thanks to the amino functional group and hyper-crosslinked porous structure, NH2-HCPs displayed remarkable adsorption ability for phenolic EDCs. The adsorption mechanism mainly involved hydrogen bond, π-π interaction, hydrophobic interaction and pore filling. Thus DPT-BB was applied as solid phase extraction sorbent to extract phenolic EDCs from water and orange juice samples prior to quantitative analysis by high performance liquid chromatography. Under the optimal conditions, detection limit as low as 0.07-0.2 ng mL-1 for water and 0.1-0.27 ng mL-1 for orange juice was achieved. Good recoveries spanned the range of 83.5%-114% were obtained for spiked samples, with relative standard deviations below 8.9%. The results demonstrated that the developed method displayed excellent practicability for sensitive analysis of EDCs.

A flexible electrochemical sensor for bisphenol A detection based on photoinitiated molecular imprinting on CdS functionalized carbon felt

Long-term and excessive exposure to bisphenol A (BPA) has an extremely detrimental effect on human health and ecological system. Hence, there is an urgent need to develop a sensitive and selective sensor for precisely monitoring BPA levels. In this work, a flexible and tailor-made electrochemical sensor for BPA has been fabricated based on in situ photopolymerization of molecular imprinting on cadmium sulfide (CdS) modified carbon felt (MIP@CdS-CF). It is worth nothing that CdS acts as a photocatalyst to enhance the capacity of photopolymerization, accordingly upgrading imprinting efficiency. Meanwhile, carbon felt (CF) exhibits attractive merits in term of superior electrical conductivity, enlarged electrochemical active areas and unique flexibility. Consequently, the novel MIP@CdS-CF electrochemical sensor shows superior sensitivity, high selectivity, extraordinary reproducibility and stability to detect BPA. The detection limit is 1.5 nM, which is lower than those of previously reported electrochemical sensors for the detection of BPA. More importantly, this newly developed electrochemical sensor can be utilized for detecting BPA in plastic bottles with satisfactory results.

Palladium-Copper Bimetallic Aerogel as New Modifier for Highly Sensitive Determination of Bisphenol A in Real Samples

In this study, a bimetallic palladium-copper aerogel was synthesized and used for modification of a graphite paste electrode (Pd-Cu/GPE), allowing the sensitive determination of bisphenol A (BPA). Different techniques, such as SEM, TEM, XPS, and AFM, were used for characterization of the Pd-Cu aerogel. To elucidate the properties of the Pd-Cu/GPE, the electrochemistry methods such as differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy were used. DPV measurements were conducted in phosphate electrolyte and buffer solution (0.2 M PBS, pH 5) at a potential range from 0.4 to 0.9 V vs. Ag/AgCl. The DPVs peaks currents increased linearly with BPA concentrations in the 0.04-85 and 85-305 µM ranges, with a limit of detection of 20 nM. The modified electrode was successfully used in real samples to determine BPA, and the results were compared to the standard HPLC method. The results showed that the Pd-Cu/GPE had good selectivity, stability, and sensitivity for BPA determination.

Management of tannery waste effluents towards the reclamation of clean water using an integrated membrane system: A state-of-the-art review

Tanning and other leather processing methods utilize a large amount of freshwater, dyes, chemicals, and salts and produce toxic waste, raising questions regarding their environmental sensitivity and eco-friendly nature. Total suspended solids, total dissolved solids, chemical oxygen demand, and ions such as chromium, sulfate, and chloride turn tannery wastewater exceedingly toxic for any living species. Therefore, it is imperative to treat tannery effluent, and existing plants must be examined and upgraded to keep up with recent technological developments. Different conventional techniques to treat tannery wastewater have been reported based on their pollutant removal efficiencies, advantages, and disadvantages. Research on photo-assisted catalyst-enhanced deterioration has inferred that both homogeneous and heterogeneous catalysis can be established as green initiatives, the latter being more efficient at degrading organic pollutants. However, the scientific community experiences significant problems developing a feasible treatment technique owing to the long degradation times and low removal efficiency. Hence, there is a chance for an improved solution to the problem of treating tannery wastewater through the development of a hybrid technology that uses flocculation as the primary treatment, a unique integrated photo-catalyst in a precision-designed reactor as the secondary method, and finally, membrane-based tertiary treatment to recover the spent catalyst and reclaimable water. This review gives an understanding of the progressive advancement of a cutting-edge membrane-based system for the management of tanning industrial waste effluents towards the reclamation of clean water. Adaptable routes toward sludge disposal and the reviews on techno-economic assessments have been shown in detail, strengthening the scale-up confidence for implementing such innovative hybrid systems.

In-Situ Construction Molecular Imprinting Electrocatalyst of Au-MoO3/Graphene for Bisphenol A Determination with Long-Term Stability

Molecular imprinting (MI) technology has been used in electrochemical analysis technology because of its unique selectivity and specificity. In this work, an electrochemical sensor based on in-situ inorganic MI-Au-MoO3/graphene for bisphenol A (BPA) analysis is designed, where MI-MoO3 is hybridized with graphene nanosheets and Au nanoparticles, and BPA is acted as the temple molecular. Differential pulse voltammetry (DPV) was used to evaluate the sensing performance of the MI-Au-MoO3/rGO sensor toward BPA determination and it is about 2.0 times that of NI-Au-MoO3/rGO. The as-constructed sensor presents a wide linear range from 0.01 to 106.04 μM and a low limit of detection of 0.003 μM. It also displays outstanding stability and repeatability up to 20 days, and can be used to analyze the content of BPA in dust leachate and plastic bottle. This sensor offers a promising strategy for environment pollution and food analysis via MI technology.

Flexible Electrochemical Platform Coupled with In Situ Prepared Synthetic Receptors for Sensitive Detection of Bisphenol A

A flexible electrochemical sensor based on the carbon felt (CF) functionalized with Bisphenol A (BPA) synthetic receptors was developed. The artificial Bisphenol A receptors were grafted on the CF by a simple thermal polymerization molecular imprinting process. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and electrochemical characterizations were used to analyze the receptors. Characterization results demonstrated that the Bisphenol A synthetic receptors successfully formed on the CFs surface. Because the synthetic receptor and the porous CFs were successfully combined, the sensor displayed a better current response once Bisphenol A was identified. The sensor's linear range was determined to be from 0.5 to 8.0 nM and 10.0 to 300.0 nM, with a detection limit of 0.36 nM. Even after being bent and stretched repeatedly, the electrode's performance was unaffected, demonstrating the robustness, adaptability and viability of installing the sensor on flat or curved surfaces for on-site detection. The designed electrochemical sensor has been used successfully to identify Bisphenol A in milk samples with satisfactory results. This work provided a promising platform for the design of implantable, portable and miniaturized sensors.

Electrocatalytic performance of oxygen-activated carbon fibre felt anodes mediating degradation mechanism of acetaminophen in aqueous environments

Carbon felts are flexible and scalable, have high specific areas, and are highly conductive materials that fit the requirements for both anodes and cathodes in advanced electrocatalytic processes. Advanced oxidative modification processes (thermal, chemical, and plasma-chemical) were applied to carbon felt anodes to enhance their efficiency towards electro-oxidation. The modification of the porous anodes results in increased kinetics of acetaminophen degradation in aqueous environments. The utilised oxidation techniques deliver single-step, straightforward, eco-friendly, and stable physiochemical reformation of carbon felt surfaces. The modifications caused minor changes in both the specific surface area and total pore volume corresponding with the surface morphology. A pristine carbon felt electrode was capable of decomposing up to 70% of the acetaminophen in a 240 min electrolysis process, while the oxygen-plasma treated electrode achieved a removal yield of 99.9% estimated utilising HPLC-UV-Vis. Here, the electro-induced incineration kinetics of acetaminophen resulted in a rate constant of 1.54 h^-1, with the second-best result of 0.59 h^-1 after oxidation in 30% H₂O₂. The kinetics of acetaminophen removal was synergistically studied by spectroscopic and electrochemical techniques, revealing various reaction pathways attributed to the formation of intermediate compounds such as p-aminophenol and others. The enhancement of the electrochemical oxidation rates towards acetaminophen was attributed to the appearance of surface carbonyl species. Our results indicate that the best-performing plasma-chemical treated CFE follows a heterogeneous mechanism with only approx. 40% removal due to direct electro-oxidation. The degradation mechanism of acetaminophen at the treated carbon felt anodes was proposed based on the detected intermediate products. Estimation of the cost-effectiveness of removal processes, in terms of energy consumption, was also elaborated. Although the study was focussed on acetaminophen, the achieved results could be adapted to also process emerging, hazardous pollutant groups such as anti-inflammatory pharmaceuticals.

An electrochemical sensor for detection of trace-level endocrine disruptor bisphenol A using Mo2Ti2AlC3 MAX phase/MWCNT composite modified electrode

Bisphenol A (BPA) is an industrially preferred material for the production of plastic and polycarbonate as well as a used material for the interior of food and beverage cans. In this study, synthesis and electrochemical sensor application of Mo₂Ti₂AlC₃/MWCNT (multi-walled carbon nanotube) nanocomposite for BPA sensing was evaluated. Mo₂Ti₂AlC₃ was used as MAX phase material in the design of the sensor, and MWCNT was preferred to increase conductivity and sensitivity. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to determine Mo₂Ti₂AlC₃/MWCNT nanocomposite's electrochemical sensor performances which had LOD of 2.7 nM and LOQ of 8.91 nM in the linear working range of 0.01-8.50 μM calculated from DPV. The composite showed a single oxidation step against BPA which is diffusion-controlled and irreversible. The sensor was successfully applied for the determination of BPA in milk pack, plastic bottle, and can with recoveries ranging from 95.67% to 100.60%. In addition, sensor performance was examined through selectivity, repeatability, and reusability studies. HPLC as a standard determination method was carried out for accuracy of the voltammetric determination method in the real samples. The developed sensor could be applied to different areas from industry quality control to clinical analysis for the detection of BPA.

Development of highly sensitive and selective bisphenol A sensor based on a cobalt phthalocyanine-modified carbon paste electrode: application in dairy analysis

The development of an accurate, sensitive and selective sensor for the detection of bisphenol A (BPA) based on the incorporation of a new phthalocyanine derivative, cobalt phthalocyanine, C,C,C,C-tetracarboxylic acid-polyacrylamide (CoPc-PAA) into a carbon-paste matrix is presented using voltammetry and constant potential techniques. The influence of measuring parameters such as pH and scan rate on the analytical performance of the sensor was evaluated. Several kinetic parameters such as electron transfer number (n), charge transfer coefficient (α), electrode surface area (A) and diffusion coefficient (D) were also calculated. Under optimum conditions, particularly at pH 7.2, the BPA sensor resulted in a wide linear range from 25 × 10^-11 M to 2.5 × 10^-7 M and a limit of detection as low as 63.5 pM. Based on these findings, it can be concluded that our sensor can be substantially utilized for detecting BPA in spiked milk samples.