Extensive use of pesticides resulting in their accumulation in the environment presents a hazard for their non-target species, including humans. Hence, efficient remediation strategies are needed, ...and, in this sense, adsorption is seen as the most straightforward approach. We have studied activated carbon fibers (ACFs) derived from viscose fibers impregnated with diammonium hydrogen phosphate (DAHP). By changing the amount of DAHP in the impregnation step, the chemical composition and textural properties of ACFs are effectively tuned, affecting their performance for dimethoate removal from water. The prepared ACFs effectively reduced the toxicity of treated water samples, both deionized water solutions and spiked tap water samples, under batch conditions and in dynamic filtration experiments. Using the results of physicochemical characterization and dimethoate adsorption measurements, multiple linear regression models were made to reliably predict performance towards dimethoate removal from water. These models can be used to quickly screen among larger sets of possible adsorbents and guide the development of novel, highly efficient adsorbents for dimethoate removal from water.
With recent advances in the field of single‐atoms (SAs) used in photocatalysis, an unprecedented performance of atomically dispersed co‐catalysts has been achieved. However, the stability and ...agglomeration of SA co‐catalysts on the semiconductor surface may represent a critical issue in potential applications. Here, the photoinduced destabilization of Pt SAs on the benchmark photocatalyst, TiO2, is described. In aqueous solutions within illumination timescales ranging from few minutes to several hours, light‐induced agglomeration of Pt SAs to ensembles (dimers, multimers) and finally nanoparticles takes place. The kinetics critically depends on the presence of sacrificial hole scavengers and the used light intensity. Density‐functional theory calculations attribute the light induced destabilization of the SA Pt species to binding of surface‐coordinated Pt with solution‐hydrogen (adsorbed H atoms), which consequently weakens the Pt SA bonding to the TiO2 surface. Despite the gradual aggregation of Pt SAs into surface clusters and their overall reduction to metallic state, which involves >90% of Pt SAs, the overall photocatalytic H2 evolution remains virtually unaffected.
Pt single atoms (SAs) supported on TiO2 surfaces form clusters and undergo reduction (by photogenerated electrons) to a metallic state over the course of a photocatalytic reaction. Although this process affects >90% of the loaded Pt SAs, Pt SA‐TiO2 photocatalysts show stable H2 production. Density‐functional theory calculations suggest Pt SA interaction with H adatom as a destabilizing factor.
Organophosphate pesticides are used in large quantities. Once accumulated in the environment, they exhibit toxic effects on non-target organisms. Dimethoate, a frequently used insecticide, and its ...oxo-analog omethoate inhibit acetylcholinesterase and are toxic for mammals. However, under environmental conditions, they also undergo chemical transformations and decomposition. Nevertheless, the systematic data about dimethoate and omethoate decomposition are missing. We performed a systematic analysis of dimethoate and omethoate decomposition under different pH conditions and estimated their long-term eco-neurotoxic effects. Dimethoate and omethoate decompose rapidly in alkaline aqueous solutions (half-lives 5.7 ± 1.4 and 0.89 ± 0.21 days) but are highly stable in acidic solutions (half-lives 124 ± 18 and 104 ± 9 days). These differences are explained using quantum chemical calculations, indicating that a weaker P–S bond in omethoate is more susceptible to hydrolysis, particularly at a high pH. The toxicity of these pesticide solutions decreases over time, indicating that no or very little of highly more toxic omethoate is formed during hydrolysis of dimethoate, pointing to the advantage of alkaline hydrolysis over other techniques for dimethoate removal. Presented data are used to benchmark dimethoate and omethoate concentrations and toxicity in contaminated water in the pH range 3 to 9 for up to 70 days upon the release in the environment.
Graphical abstract
The release and accumulation of pesticides in the environment require the development of novel sustainable technologies for their removal. While adsorption is a classical approach, the design of new ...materials with enhanced adsorption properties could rationalize the remediation routes and decrease potential risks for their non-target organisms, including humans. More importantly, the use of adsorbents and their synthesis should be implemented in a sustainable and environmentally friendly manner. In this contribution, we studied the adsorption of organophosphorus pesticides (OPs) dimethoate, malathion, and chlorpyrifos on viscose fiber–derived activated carbon fibers (ACFs). The most efficient adsorption was found for chlorpyrifos, followed by malathion and dimethoate, while material properties were correlated with OP uptake. These ACFs are extremely efficient for chlorpyrifos adsorption, with experimentally observed adsorption capacitances reaching 240 mg g
−1
. Detailed analysis suggests that chlorpyrifos is physisorbed on ACF surfaces and that increased surface hydrophilicity reduces the uptake. Studied ACFs have great potential for practical application. They can reduce OPs’ concentrations to such levels that no acute neurotoxic effects of the studied OPs in spiked tap water samples are seen, even for starting concentrations up to 10
4
times higher than the allowed ones. Finally, this study presents possible guidance for developing even more efficient and environmentally friendly adsorbents for chlorpyrifos, the most toxic among studied OPs.
Graphical abstract
Intensive use of pesticides requires innovative approaches for their removal from the environment. Here we report the method for degradation of dimethoate in water using non-thermal plasma needle and ...analyze kinetics of dimethoate removal and possible degradation pathways. The effects of dimethoate initial concentration, plasma treatment time, Argon flow rate and the presence of radical promoters on the effectiveness of proposed method are evaluated. With argon flow rate of 0.5 slm (standard litres per minute) 1 × 10−4 M dimethoate can be removed within 30 min of treatment. Using UPLC analysis it was confirmed that one of the decomposition products is dimethoate oxo-analogue omethoate, which is in fact more toxic than dimethoate. However, the overall toxicity of contaminated water was reduced upon the treatment. The addition of H2O2 as a free radical promoter enhances dimethoate removal, while K2S2O8 results with selective conversion to omethoate. Using mass spectrometry in combination with the theoretical calculations, possible degradation pathways were proposed. The feasibility of the proposed method for dimethoate degradation in real water samples is confirmed. The proposed method is demonstrated as a highly effective approach for dimethoate removal without significant accumulation of undesirable toxic products and secondary waste.
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•Development of an efficient treatment to remove water pollutants is urgent.•Non-thermal plasma needle is a new method for degradation of dimethoate in water.•This method enabled us to successfully remediate 1 × 10−4 M dimethoate from water.•The feasibility of the proposed method in real water samples is confirmed.
•Electrochemical reduction of graphene oxide proceeds with activation energy below 30 kJ mol−1.•Reduction of graphene oxide films is faster in KCl than in LiCl-containing electrolyte.•Lateral ...conductivity through the film is restored rapidly, at deep negative potentials.•Transversal conductivity is restored locally, through the growth of conductive islands which coalesce.•Isolated OH groups are easy to reduce, while cluster oxygen functional groups are more stable.
Graphene oxide finds applications in different fields of science, including energy conversion. Electrochemical reduction of graphene oxide (GO) significantly improves its conductivity. However, the kinetics of this process depends on the solvent, supporting electrolyte, pH, and numerous other factors. Most studies report the macroscopic views and ex-situ properties of reduced GO. To expand the knowledge about GO reduction, in this study, we used cyclic voltammetry (CV), simultaneous 2 points and 4 points resistance measurement (s24), conductive atomic force microscopy (AFM), and theoretical calculations. Using CV, we demonstrated that the choice of supporting electrolyte (KCl or LiCl) influences the potential range in which electrochemical GO reduction occurs. The activation energy of this process was estimated to be below 30 kJ mol‒1 in both electrolytes, being significantly lower than that required for thermal reduction of GO. Simultaneous in situ s24 resistance measurements suggest that GO films reach a highly conductive state at deep negative potentials, with an abrupt, irreversible switch from non-conductive to the conductive state. However, conductive AFM presents a more exact picture of this process: the reduction of GO films starts locally while the formed conductive islands grow during the reduction. This mechanism was confirmed by theoretical calculations indicating that the reduction starts on isolated oxygen-functional groups over the GO basal plane, while clustered OH groups are more difficult to reduce. The presented results can help in tailoring reduced GO for a particular electrochemical application by precisely controlling the reduction degree and percentage of the conductive area of the reduced GO films.
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The HeartPy Python toolkit for analysis of noisy signals from heart rate measurements is an excellent tool to use in conjunction with novel wearable sensors. Nevertheless, most of the work to date ...has focused on applying the toolkit to data measured with commercially available sensors. We demonstrate the application of the HeartPy functions to data obtained with a novel graphene-based heartbeat sensor. We produce the sensor by laser-inducing graphene on a flexible polyimide substrate. Both graphene on the polyimide substrate and graphene transferred onto a PDMS substrate show piezoresistive behavior that can be utilized to measure human heartbeat by registering median cubital vein motion during blood pumping. We process electrical resistance data from the graphene sensor using HeartPy and demonstrate extraction of several heartbeat parameters, in agreement with measurements taken with independent reference sensors. We compare the quality of the heartbeat signal from graphene on different substrates, demonstrating that in all cases the device yields results consistent with reference sensors. Our work is a first demonstration of successful application of HeartPy to analysis of data from a sensor in development.
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